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GrassRoots also published a great article on front camber for MINI Coopers. It was a testing of a R53 with different camber settings and what was “ideal”. I seem to remember that the lap times were at their minimum with camber somewhere between -3.0 and -3.5 deg. Above that, braking suffered and lap times started to go up.
The one thing that I don’t hear/read much about is increasing caster. Simply put, caster becomes camber as you turn the steering wheel and the R-Comps I tried suggested a preferred minimum camber and recommended as much caster as possible. Also, if you look at the steering geometry, as you turn the steering wheel and the strut housing rotates, the front wheels will loose camber. Not talking about body lean; just in a static situation. It is the caster designed into the suspension that counteracts this.
I have seen a few (one or 2) camber/caster plates for these cars, but there is not much. There is also a front lower control arm bushing that adds caster. A friend of mine who used to autocross his R53 (and did very well at it) tried these and loved them.
Is there anyone out there who has experience with changing caster?
GrassRoots also published a great article on front camber for MINI Coopers. It was a testing of a R53 with different camber settings and what was “ideal”. I seem to remember that the lap times were at their minimum with camber somewhere between -3.0 and -3.5 deg. Above that, braking suffered and lap times started to go up.
The one thing that I don’t hear/read much about is increasing caster. Simply put, caster becomes camber as you turn the steering wheel and the R-Comps I tried suggested a preferred minimum camber and recommended as much caster as possible. Also, if you look at the steering geometry, as you turn the steering wheel and the strut housing rotates, the front wheels will loose camber. Not talking about body lean; just in a static situation. It is the caster designed into the suspension that counteracts this.
I have seen a few (one or 2) camber/caster plates for these cars, but there is not much. There is also a front lower control arm bushing that adds caster. A friend of mine who used to autocross his R53 (and did very well at it) tried these and loved them.
Is there anyone out there who has experience with changing caster?
The race car has caster/camber plates. We increased caster to max (which I think was ~ 6 degrees) because we couldn't get more than 2.5 degrees of negative camber. And it works fine at the "club" tracks we frequent in Texas, Oklahoma, and Louisiana.
However, at CotA this past weekend which has long hard brake zones I had an issue with overheating the insides of the fronts. We ended up running the car with about 1.5 degrees of negative camber (so the tires are more level under hard braking which we think causes the overheating on the insides) and slightly less caster. We haven't figured everything out yet, but we take tire temps after every session.
I was at Lime Rock Park (LRP) last Friday for a track day and met up with some friends. We had a chance to do some lead-follow and one friend posted this video on YouTube in which he is following my car and shows it from the back. I thought that it would be interesting to post a link to this video here given the various discussions throughout NAM about the potential ill effects from adding a large front sway bar (FSB) in conjunction with a large rear sway bar (RSB). I think the video show reasonably well how my car handles.
A bit of background. LRP is a short track. It is 1.5 miles around and made up of mostly right turns and one numbered left turn (T3) in the esses and a left dog-leg shortly after that. In this video I am running a stock S engine (182 hp), stock MINI sports suspension springs, Quaife LSD, Bilstein B8 shocks, IE fixed camberplates (-1.5 deg), PowerFlex front lower control arm bushings, 27mm solid FSB, 25mm hollow RSB on the softest setting and 205/50x15 Bridgestone RE71Rs (brand new this day).
The video starts with us leaving the pits and entering T1, which is at the end of the front straight. The car and tires are hot as we had just pitted from a 20 min session and were invited to go back out for another session. For reference, at the completion of a lap and the start of the next, I am typically doing ~105+ mph on the front straight, going into T1 braking zone. I trail brake almost to the apex of T1. From there, it is maintenance throttle to the turn-in for T2 (the second part of this 180 deg bend). T2 is the one of the worst turns for a MINI as it is very hard to carry any momentum this far around the bend and the car wants to push (understeer). I will “help” the car to rotate into T2 with aggressive throttle steering (an abrupt lift off the throttle). I didn’t have data for this session (late in the day and ran out of battery), but typically T1 is taken at about 1g per Harry’s. Another thing I will point out is that, in going through the final turn that enters onto the front straight at the end of the downhill, you can see the lean of my car. This turn is about 80+ mph at the apex. There is also a good shot of the back of a Neon going into the left-hand turn, which provides a comparison to my car (I don’t know how it was prepped).
I will say that a downside to my setup (as compared to my previous S that was sprung much softer and had only a 20mm RSB) is that it has little response to throttle steering inputs. That is, an abrupt lift of the throttle doesn’t produce a lot of rotation. I don’t know if this is just the swaybars or if a large RSB with stiff springs up front would be the same. I have never had the chance to make that comparison. I also have not tried a stiffer setting on the RSB.
Question, if you are looking for more rotation, why do you have the rear bar set on the softest setting?
Good Question!
I assume your are referring to my comment about that T2. I have had a ride in a R53 Cooper with a 22mm RSB and 600# springs in the rear (I forget the rest of the setup) and the driver was very quick around that same track. He had the same problem that I have, but to a lesser extent. I think it is the nature of that 1 - 2 turn combination, more so than the car. T1 is a larger radius turn than T2. T1 is entered with heavy trailbraking. This loads weight onto the front wheels and lowers the front of the car which adds camber. With the stiff front sway bar I don’t loose much camber given I don’t have much car lean in the turn. All of this makes for a nice entrance and gives me good grip in the turn. However, once past the T1 apex, I am on maintenance throttle then a lift off the throttle to turn in for T2. I no longer have that front end loading and gone is the grip I had going into T1. Hence the tough time with T2.
I could add more RSB stiffness and get more rotation in this turn. However, I am running a somewhat conservative setup and it works well for the other turns on this track and for the other track I spend most of my time. So, for me T2 is a bit of a sacrifice and a compromise for the other turns on this track and for the other track in general.
The conservative setup is out of self preservation. By that I mean, I want to drive the car home at the end of the day. If you watch that video and observe the area either side of the pavement you will see either guardrail that is really close or grassy land that is sloped away from the track, which leads to guardrail. In either case, going off the track leads to guardrail and most likely a totaled car, which I have seen in numerous place on this track. In most cases it has been the result of either under braking and going into the guardrail straight ahead or over rotation (oversteer) in a turn and ending up in the guardrail on the inside of the turn and at the exit of that turn. I have also had unexpected and undesirable occurrences happen in a turn, like coming upon someone who has suddenly braked hard when in a turn or I have hit antifreeze at the apex of a 100+ mph turn with guardrail 2’ off the track (different track).
My somewhat conservative setup gives me a neutral to a slight understeer handling in most corners. This comes from the FSB/RSB combination, mild camber in the front (-1.5 deg) and a lot of camber in the rear (about -2.5, if I remember right). It is probably a 95+% car from what would be the optimum setup. This allows me a little “room” for unexpected occurrences and/or my own brain farts, which I have had a few. With this setup, the car and I survived the antifreeze. But, with technique (late braking, trailbraking, throttle steering, being smooth with brake release and steering inputs, etc) I can usually overcome the understeer. However, even with this setup, I have had the rear step out on me. So, it can still be made to oversteer; it just takes some effort.
If I was big into racing or autocross, I would have a different setup, like a 26mm front bar. the RSB on a stiffer setting, less camber in the rear, more camber in the front, etc. But for me, doing DEs, this setup has worked out really well. If I were to make any changes it would be to increase the negative camber up front by a half to a deg, which would give me -2 to -2.5 deg and that would be to even out the loading on the tires.
The race car has caster/camber plates. We increased caster to max (which I think was ~ 6 degrees) because we couldn't get more than 2.5 degrees of negative camber. And it works fine at the "club" tracks we frequent in Texas, Oklahoma, and Louisiana.
However, at CotA this past weekend which has long hard brake zones I had an issue with overheating the insides of the fronts. We ended up running the car with about 1.5 degrees of negative camber (so the tires are more level under hard braking which we think causes the overheating on the insides) and slightly less caster. We haven't figured everything out yet, but we take tire temps after every session.
Your post reminded me that there is an interesting GrassRoots Motorsport post about testing different camber settings for the R53 (probably applies well to the R56, too):
With too much camber, they too had braking issues (a bit different consequence, but same cause)
Alan - For COTA, what do you run for a brake setup (ie - what brakes front and rear, and what pads front and rear)? And are you at threshold braking at the rear?
Your post reminded me that there is an interesting GrassRoots Motorsport post about testing different camber settings for the R53 (probably applies well to the R56, too):
With too much camber, they too had braking issues (a bit different consequence, but same cause)
Alan - For COTA, what do you run for a brake setup (ie - what brakes front and rear, and what pads front and rear)? And are you at threshold braking at the rear?
The front brakes are Wilwood Dynalite calipers with 12" x 1.25" Coleman race rotors and G-Loc R16 pads
The rear brakes are stock calipers, Autozone rotors, and G-Loc R10 pads.
As far as threshold braking at the rear I have never looked into that - the rears do very little braking. 61% of the cars weight is on the fronts, plus weight transfer under braking - I should be able to do stoppies!
I do collect wheel speed data with the Aim and have a macro that calculates efficiency of the LSD. I could look at front to back wheel speeds / slip under braking....
The front brakes are Wilwood Dynalite calipers with 12" x 1.25" Coleman race rotors and G-Loc R16 pads
The rear brakes are stock calipers, Autozone rotors, and G-Loc R10 pads.
As far as threshold braking at the rear I have never looked into that - the rears do very little braking. 61% of the cars weight is on the fronts, plus weight transfer under braking - I should be able to do stoppies!
I do collect wheel speed data with the Aim and have a macro that calculates efficiency of the LSD. I could look at front to back wheel speeds / slip under braking....
I know this is a thread about suspension, however, you made the point that your suspension geometry had to be changed because braking caused tire heat issues. I suspect that reducing camber that much was a compromise. It also points out how everything is interconnected.
An observation that I have made is that while these cars do most of the braking in the front, I have had success in moving some of the brake load to the rear brakes. I have also followed the MINI designers lead with this. I originally followed the conventional wisdom of forward brake bias (eg: Carbotech XP10s in front and 8s in the rear). I have since gone to a more aggressive rear brake pad and now run Hawk DTC60 pads front and rear. Part of this change comes from the factory setup for the R56 JCW. The front Brembos run a 12.4” rotor. With that they include a larger rear rotor than is used in the S and base Cooper (which I plan to go to when my current rotors wear out). It also seems that in a race car, which is more stiffly sprung, there will be less weight transfer to the front wheels under braking as compared to the street counterpart, which means that the rears could take on more of the braking duties than in the street setup.
My reason for my brake questions to you, is because of my own observations. As a thought exercise, I was wondering if it would be possible to recover some of the camber you dialed out, by having more rear braking. Of course, the rear brakes would have to stay within some sort of temperature limits (it would do no good to overheat those solid rotor; larger dia here would help with that) and the rears would have to stay within the limits of adhesion of the tires. Like I said, just thinking out loud hear, all under the guise of helping out the suspension geometry.
Eddie07S, I loved your LRP video. Brought back memories of the mid-80s when I was there for an IMSA GTP race, the turbo cars would spit flames out the back when they were off the throttle and singe the front bumper of the car behind. The sounds were glorious. Porsche 962s, the Group 44 Jaguar XJR5s, I forget what all else.
I agree with your philosophy of a slightly conservative setup. I recently went from softest to middle setting on the RSB and have been carefully approaching the limits. Very important to be able to drive the car home at the end of the day. I have never had the back end get away from me, I have managed to make the entire car slide in a fast, off camber downhill turn (turn 10 at Laguna Seca), but never anything close to losing the back end. Maybe I'm just not trying hard enough!
Final thought - in the Grassroots Motorsports article I linked earlier, the author uses the term "load transfer" instead of "weight transfer" to describe the change in force on the wheels under braking / cornering / etc. For some reason I find "load transfer" does a much better job of describing what is happening. "Weight transfer" to me suggests that the mass distribution within the car is changing (which it is not), "load transfer" says that the forces on the tires is changing due to the moments caused by braking, cornering, etc. Just different terms to describe what is happening but one seems so much more accurate and descriptive to me.
I was at LRP today to watch practice sessions for the SVRA and T/A races. Got to see everything from ‘60s 427 Corvettes, Cameros and Mustangs to Owen Trinkler’s IMSA Mercedes (beautiful car with handling beyond compare). And the T/A2 cars very nicely spit flames out the sides (that’s were the exhaust is now). Quite a sight coming out of a 4” pipe!
In keeping with the spirit of this thread, I may have some video from today that may show what I mean about the 1 - 2 turn combination at LRP and how T2 is a compromise turn relative to car setup. I will look to review it soon so I can get it up for viewing.
As for sliding a MINI through a turn vs loosing “it” in a turn is an interesting conundrum. A MINI, even with a large sway bar in the rear can be made to slide (4 wheel drift?). This is pretty classic. You can see it with the IMSA ST MINIs at a place like Dayton. If I understand correctly, this is done with a bit of throttle on, which would keep load on the rear wheels. The car is basically in a neutral to understeer attitude. The conundrum and problem is that while a MINI can easily be made to understeer, it can also be made to oversteer, more or less easily depend in on the setup. This “setup” includes spring rates, sway bars and shock dampening. That is oversteer will come in if, when you are “drifting”, you happen to lift off the throttle. This will move load forward and the rear wheels will loose traction, the fronts will gain traction and the car will rotate. How much will depend on how conservatively the car is setup. A really experienced driver will get back on the throttle and, hopefully, this will end the rotation. Experienced race car drivers use this tendency for oversteer to their advantage. However, If rotation happens to an inexperienced driver, they are likely to lift further in a panic. The fronts will get further loaded and the rears more unloaded. In addition, with that load transfer, the rears will loose camber which will further exacerbate the problem. This will likely result in the car spinning, as in old Porsche 911 oversteer. I would not suggest trying that Turn 10 at Laguna Seca. But it could happen in inadvertently, which is why I have a conservative setup.
A side note: It is interesting that T10 at Laguna Seca is a MINI drift turn because T10 at Watkins Glen is also a MINI drift corner. The thing that one has to remember at WGI is that if your drift too wide is to just let it go wide and go into the runoff, as there is a football field size runoff area there. If you try to correct it and hit the curbing, it will likely catch that over-corrected steering input and spin your car into the inside guardrail (seen that happen... Ugh!).
BTW - I like your observation about using the term “load transfer”.
Question, if you are looking for more rotation, why do you have the rear bar set on the softest setting?
Originally Posted by Eddie07S
Good Question!
I assume your are referring to my comment about that T2. I have had a ride in a R53 Cooper with a 22mm RSB and 600# springs in the rear (I forget the rest of the setup) and the driver was very quick around that same track. He had the same problem that I have, but to a lesser extent. I think it is the nature of that 1 - 2 turn combination, more so than the car. T1 is a larger radius turn than T2. T1 is entered with heavy trailbraking. This loads weight onto the front wheels and lowers the front of the car which adds camber. With the stiff front sway bar I don’t loose much camber given I don’t have much car lean in the turn. All of this makes for a nice entrance and gives me good grip in the turn. However, once past the T1 apex, I am on maintenance throttle then a lift off the throttle to turn in for T2. I no longer have that front end loading and gone is the grip I had going into T1. Hence the tough time with T2.
I could add more RSB stiffness and get more rotation in this turn. However, I am running a somewhat conservative setup and it works well for the other turns on this track and for the other track I spend most of my time. So, for me T2 is a bit of a sacrifice and a compromise for the other turns on this track and for the other track in general.
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I remarked that T2 at LRP was a bit of a sacrifice and a compromise. This was in respect to suspension setup, but has to do with how to drive through that turn as well as the rest of the track.
I was back at LRP yesterday to watch practice for this weekend’s TA and SVRA races. While I was there I took some video of the TA cars coming out of Turn 1 and going through Turn 2. Standing there, watching them, it was clear that they too were on maintenance throttle until they got past the apex of T2 at which point they got on the gas. What you don’t see in the video is the cars coming down the front straight at probably 140 mph, braking hard going into T1 and trailbraking up to the apex. The video picks up from there. Also, remember T1 is a larger radius than T2 so it makes it even harder to get T2 correct. I am hoping that this video show why I think T2 is a sacrifice as the cars have little to do but to just get through it. So, this is why I wouldn’t build in rotation for this turn as it likely won’t be right for the rest of the turns on the track.
However, because I was there and I knew what I was looking for, I may be seeing what I want to see in the video, if you know what I mean. Hopefully, this actually does show what I think I’m seeing...
So, a serious question on suspension setup and tires. I didn’t think of this one until I got my new JCW and I found out that the tires are 205/40 - 18” are the OEM size as compared to the 205/45-17” that are optional...
The question is - does anyone have experience with wider and lower profile tires on a MINI than what we have been working with (eg: the 17”, 45 series) and is there a difference in suspension setup to get the maximum out of them? This question would be applicable to street and track.
I know a lot of the suspension development for these cars has been with the 17” 45 series tires. I also know that the MINI’s McPherson strut suspension goes through a lot of geometry changes as it goes through it motions. In particular how it gains and losses camber as the wheels go up and down and how body roll in corners reduces camber. It would seem that if a tire is too wide and has too low a profile (but on the correct size wheel), that the car might not be able to take advantage of the whole tire.
I am looking to further modify my Cooper S with the addition of a set of Ohlins coilovers and camber/caster plates. My plan is to set the camber to -2 to -2.25 deg and add 0.5 deg caster. In the rear set the camber to -2.5 deg or max out the MINI adjuster.
The unknown in these changes is the shock settings. I know how the car handles with the 27/25mm front/rear sway bars, rear in the softest setting, which I plan to retain (at least for now), Bilstein B8s and MINI sports springs. I also know the spring rates of the Ohlins (400/343 #/in front/rear), which are in the same relative relationship as the stock springs front to rear.
I have access to a go kart-like autocross course on which I can safely test the car. My plan is to start with the shock set on the softer side of mid-level, with the fronts slightly stiffer than the rear. This should set the car up with a bit of understeer and I can stiffen the rear/soften the front to dial that out, if needed. My objective is to set the car up for track day DEs, with a bit of conservatism to help ensure I can drive the car home at the end of the day.
Anyone have any suggestions, pros, cons with my plans for setting up the shocks?
In keeping with the spirit of this thread, it would be interesting to hear how people go about setting adjustable shocks. It is one thing to setup shocks that are single adjustable, it is another to setup 2-way adjustable shocks... Any thoughts?
Caster / Camber plates
We've found the best setup is to max out caster, then adjust camber using tire temps. Max caster allows us to run with just 1 to 1.5 degrees negative camber. Improves braking and tire wear.
2-way adjustable shocks - assuming that means separate rebound and compression (not always true)
Front set high compression / low rebound This acts as anti-dive under braking and generally helps the heavy end of the car
Rear set high rebound / low compression Helps the car squat under acceleration, and when taking a set at turn-in it keeps the rear from coming up before track-out.
Double check on straight with dips - car should not pogo
I know this may sound a little goofy, but with a car that is weighted 60% front / 40% rear you have to do some non-intuitive things to make it handle like a 50/50 car.
Adjust / drive laps / check tire temps and pressures / repeat On a track you've done a bunch of laps on and know how the car should feel.
Alan -
Yes - your assumption is correct. I did mean the shocks with separate compression and rebound adjustments.
A couple of questions about your post...
Caster isn’t talked much about for MINIs and it seems that it should be. Do you know if your added caster has any negative affect on the power steering pump from any add load?
What don’t you like about dive under braking? Or, what bad thing is the car doing when the front dives? I have no experience in setting up a car for anti-dive and wonder what I should look for.
Also, I should have noted in my post that the Ohlins have a single adjuster, but it stiffens or softens both the compression and rebound, simultaneously. This is the same as the Bilstein B16 coilovers. But it is different from most single adjustment shocks (Koni Yellows, KW, BC, AST, etc) that only change the rebound.
I think you will really like the Ohlins! I have to go back and check my notes but from memory, the first time I was at the track with the Ohlins I started out at about 10 clicks on the adjuster from full stiff. I cranked them up in subsequent sessions until finally I was at -1 front, -3 rear. The car was very happy there - I could push it really hard but never had a worry about the back stepping out. If I was stupid I'd get understeer, especially in the hairpin (T2) but the solution to that was taking the proper line, trail braking, and not being to eager with the throttle.
For daily driving I have found that similar to the track I prefer the back a few clicks softer than the front, generally I'm at -18 front, -20 rear. I have posted before that I'm set up with -2 degrees camber all around, with tire rotations at 5K intervals I don't have any uneven wear. If the car was dedicated to the track I'd experiment with more front camber.
At the moment I have the fronts off the car, I finally sent them in for rebuild. I called Performance Shock at Sonoma Raceway, they said due to the price of parts it didn't make sense for them to rebuild them, send them to Ohlins North Carolina instead. The Ohlins guys were great, two days after UPS dropped off the shocks they called to say they had them apart, the top teflon bushings were totally shot and I should have sent them in earlier. They had to put in a bit of extra labor to polish the inner tube, so it was just over $500 plus shipping. They were on the way back in 2 days. They said typically it should be about $200 per corner. Based on my experience you should plan on having them rebuilt after about 30K, maybe less if you have a lot of track time on them.
When I bought the Ohlins I ordered new rear top plates and Powerflex bushings so I didn't have to deal with getting a spring compressor to take the original top plates off. I saved the stock shocks/springs and just swapped them back in while I have the Ohlins off for rebuild.
Alan -
Yes - your assumption is correct. I did mean the shocks with separate compression and rebound adjustments.
A couple of questions about your post...
Caster isn’t talked much about for MINIs and it seems that it should be. Do you know if your added caster has any negative affect on the power steering pump from any add load?
What don’t you like about dive under braking? Or, what bad thing is the car doing when the front dives? I have no experience in setting up a car for anti-dive and wonder what I should look for.
Also, I should have noted in my post that the Ohlins have a single adjuster, but it stiffens or softens both the compression and rebound, simultaneously. This is the same as the Bilstein B16 coilovers. But it is different from most single adjustment shocks (Koni Yellows, KW, BC, AST, etc) that only change the rebound.
You are correct that adding caster will make the steering heavier. Have been running max caster for ~2 seasons now without PS issues.
You should have the car corner balanced when adding coilovers. You will find each front tire carries about 800 lbs. The coilovers have about 4 inches of travel. Without long springs and a bunch of pre-load the 400 lb/in springs will be half way compressed with the car just sitting. Another 1.0 G of load will have them on the bump stop. A situation easy to attain under threshold braking with decent track tires. You can use the compression setting to help this situation, but you do not want a bunch of rebound. You want the front to come up as you release the brake.
I think you will really like the Ohlins! I have to go back and check my notes but from memory, the first time I was at the track with the Ohlins I started out at about 10 clicks on the adjuster from full stiff. I cranked them up in subsequent sessions until finally I was at -1 front, -3 rear. The car was very happy there - I could push it really hard but never had a worry about the back stepping out. If I was stupid I'd get understeer, especially in the hairpin (T2) but the solution to that was taking the proper line, trail braking, and not being to eager with the throttle.m
For daily driving I have found that similar to the track I prefer the back a few clicks softer than the front, generally I'm at -18 front, -20 rear. I have posted before that I'm set up with -2 degrees camber all around, with tire rotations at 5K intervals I don't have any uneven wear. If the car was dedicated to the track I'd experiment with more front camber.
At the moment I have the fronts off the car, I finally sent them in for rebuild. I called Performance Shock at Sonoma Raceway, they said due to the price of parts it didn't make sense for them to rebuild them, send them to Ohlins North Carolina instead. The Ohlins guys were great, two days after UPS dropped off the shocks they called to say they had them apart, the top teflon bushings were totally shot and I should have sent them in earlier. They had to put in a bit of extra labor to polish the inner tube, so it was just over $500 plus shipping. They were on the way back in 2 days. They said typically it should be about $200 per corner. Based on my experience you should plan on having them rebuilt after about 30K, maybe less if you have a lot of track time on them.
When I bought the Ohlins I ordered new rear top plates and Powerflex bushings so I didn't have to deal with getting a spring compressor to take the original top plates off. I saved the stock shocks/springs and just swapped them back in while I have the Ohlins off for rebuild.
Thanks for the info.
I have several friends who us the Ohlins and they too had very positive experiences with them. I know one of them keeps copious note and I would be curious how your setting match up with his. I’ll have to ask him.
You do raise another question - That is, how do you know when shocks need to be rebuilt? What are the tail-tell signs?
I have been hesitant to switch from my current setup for a few of reasons. The first is that I really like way the car handles now, with the MINI sports springs and Bilstein B8s. Then there was the desire to not lower the car as it was my DD. Lastly, I wasn’t sure how well the stiffer springs would “play” with the big front swaybar. However, that has changed now that I bought the JCW; the 2012 S can be lowered without issue. I think the B8s need rebuilding; the last alignment showed that one front might be getting sloppy as it had more camber than it should. As for how the car will do with the stiffer springs, I guess I will find out.
Most people pair the Ohlins with a stock front sway bar and a larger, usually 22mm solid or 25mm hollow, rear bar. I’ll be pairing the Ohlins with 27mm FSB and a 25mm hollow RSB. I also have the rear bar set at its softest setting. I suspect my settings will be different from yours as a result.
A side note: When I mentioned to a person who sets up race cars that I had a large FSB, he said that I will need softer springs. Not sure why as he didn’t have a good “technical” reason for this comment. Maybe it was “conventional wisdom” without knowing the background for it. Without that background, “conventional wisdom” wisdom is hard for me to accept just off-hand. I like to know the “why” behind it so I can understand what I am dealing with when I make a change. Also, changes are also so much a part of driving style. Without knowing the “why” behind it, I don’t know what I need to adjust driving wise. For example, I grew up drifting a 1966 Chevy 327 station wagon and the like around on snow covered roads here in the NE. The back end gets loose and starts coming around, it is corrected by getting off the gas. My first experience with a MINI with a big RSB and otherwise stock suspension that went into a rear wheel slide in a high speed dog-leg wasn’t pretty. I got off the gas to correct it. Nope, that didn’t work. There is a lot of driving “muscle memory” that needed to be undone to have had a chance of having gotten that one right. I made my upgrade to the big FSB and big RSB after a lot of study and understanding. That change is a little more straight forward than the adjustable shock upgrade. I plan to approach this upgrade very carefully.
Originally Posted by Alan
You are correct that adding caster will make the steering heavier. Have been running max caster for ~2 seasons now without PS issues.
You should have the car corner balanced when adding coilovers. You will find each front tire carries about 800 lbs. The coilovers have about 4 inches of travel. Without long springs and a bunch of pre-load the 400 lb/in springs will be half way compressed with the car just sitting. Another 1.0 G of load will have them on the bump stop. A situation easy to attain under threshold braking with decent track tires. You can use the compression setting to help this situation, but you do not want a bunch of rebound. You want the front to come up as you release the brake.
Thanks!
Good points. So I am sure my stock springs are on their bump-stops when I am braking, even though I don’t get to 1 g under braking... So the Ohlins should help with this, given their stiffer springs.
This also points out why it is necessary for the spring rates to be listed for springs and coilovers that are aimed towards track use. So many coilovers don’t list their spring rates, so you have no clue what you are getting into when you buy a set of those.
Your ears will tell you when a rebuild is needed, you'll start to hear clunking from the suspension over bumps. Fronts are really easy to hear, back is more subtle. But don't let it get that far. This weekend I swapped the rears back to stock also and noticed that the rear suspension was a lot quieter. I haven't been able to feel any side to side play or rattle in the damper off the car, it's impossible to put a high enough load on it by hand.
Regarding how the stiffer springs will work with your stiffer front sway bar, I think of a sway bar as an additional spring force that is applied when there is a lateral force on the car. That means that your stiffer sway bars already give you a stiffer suspension while cornering, and the new springs will add further stiffness. You might have to change the sway bar setting either front or rear though to maintain the same balance as what you have now.
The springs I have from Ohlins are 70N/mm front, 50N/mm rear. Some documents say 60N/mm for the rear but that is either old or a typo, the actual spring says 50N. When I installed them originally at the recommended pre-load the back sat really high, I had to lower the spring perches about 5mm to reduce the rake.
Relative to coilovers, I found this thread that discusses the “The Science of Coilovers”. For anyone installing coilovers and seriously needs or wants to understand what they are going to do to the car, the OP of this thread goes through a number of measurements he took when he installed the JCW Pro coilovers on his F56 MINI and he explains what the measurements mean relative to how the car’s suspension is going to perform. A lot of what he discusses at the beginning seems to be applicable to the installation of any coilovers, even though the focus of the discussion was the JCW parts. For me it was an interesting read:
Having just installed the JCW Pro coilovers on my 2019 JCW, I thought about what would be a good height to lower the car to. It would have been nice if the MINI instructions for installing these things had that information correctly listed in their manual, but they don’t. It has a major error that no one can figure out. So I did some searching for information on this. There is a really good thread that was started and it includes a lot of info about these suspension parts and it even includes the start of a discussion about the car’s roll centers. But that discussion was never finished.
Here is my snap shot of what I have learned from all of this:
- Lowering a car can be a good thing (Lower CG and lower roll center), but too much of a good thing can be a bad thing (bad affect on handling; see link to Charlie’s post)
- The difference in front to rear roll center heights (or height ratio) will affect the handling of the car with respect to understeer and oversteer. Raising the front and/or lowering the rear will move the handling of the car towards understeer. Lowering the front and/or raising the rear will move the car’s handling towards oversteer.
- Adding negative camber to a MINI Cooper will lower the roll center of the car. This needs to be taken into account when lowering a car. Lowering a MINI will increase the negative camber, so looking only at the angle of the lower control alone will not tell the full story of where the roll centers have moved to and whether they have gone too far. This is doubly if one is both lowering the car and adding camber plates to increase the negative camber.
A couple of things that I do know...
- On a F56 hatch, if you measure from the center of the wheel, vertically, to the wheel well arch on a stock MINI, the front will measure about 1/2 inch greater than the rear. But this does not mean the car has a rearward rake.
- MINI historically has only lowered their cars by 10mm, the same front and rear. So, the front to rear height ratio stays the same and by that they don’t change the car’s propensity for understeer/oversteer.
I plan to keep a fairly conservative suspension setup for on the track. I have no desire for the car to go into a snap oversteer when I have to react to something unforeseen that occurs ahead of me... So, it looks like I will go with MINI’s lead on this one. First lower the car the same front and rear. Second target for 10 to 15mm of lowering all the way around. I am assuming MINI has done their homework on this and their 10mm of lowering will keep the roll center from being too low and that they have a bit of conservatism in their ride heights such that a little lower doesn’t create issues and it will allow for some increased negative camber in the future...
Eddie, Gollum is going in for corner balancing in the next week or so. I'll take that opportunity to put a digital level on the lower control arms. The SAI is known, due to the alignment report. At 12,6 degrees, and with the hub carriers (-30 min from stock) I've -2.1 for camber.
With the LCA angles perhaps I can project the instantaneous center location with sufficient accuracy.
05-06-2019, 09:24 PM
