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Fingers crossed but I wouldn't hold out much hope. Do you speak German? The only useful information I've seen out of KW came from motherland, the NA office seems to be a bit weak technically.
So Jeremy's initial setup was so careful, that there is no further adjustment justified.
Ready for the 2020 season.
Thanks MoP!
Cheers,
Charlie
PS: I am still waiting for the full stroke, and the stroke until bump stop, for the JCW Pro Coils. I think I will get it eventually. \With the front end fully extended, the ride height (lower edge of 17" wheel to top of wheel well) this setup is 654 mm (25.75 inches) which 76 mm (2.9 inches) of extension from ride height to the limit of the shock. I still hope for the compression stroke from ride height until the bump stop, but not yet. At present I am down 15mm front, and 10 mm rear, and have no data to add. Except that the LCA angle is 0 degrees.
Also note that you have one other piece of info from all of this. You say that the LCA angle is 0, with the car lowered 15mm. So, if you measure the length of the LCA, from pivot to pivot, you can calculate the angle of the LCA at the stock JCW height. This will allow you to calculate the location roll center at the stock height.
In this very sketchy sketch, where scale is approximate (wheels 25" tall, axle height 12.5", track 67"), it seems that dropping the outer ball joint only 15 mm (.6") will put a 10 degree angle on the LCA.
It seems that might well move the roll center upwards, closer to the roll axis, by 2-3 inches. Assuming the CG height is 21" that change would reduce the roll moment of the chassis significantly.
I sure wish I had the dynamic model, but I am just not willing to do the work, and spend the money and time.
At the end of the day, and as usual, the car will be better than the driver this coming season...
Charlie - Sorry for my confusion, but ... Above you say “if you lower the outer ball joint 15mm”. Is this to make the angle of the LCA be at the “stock height” angle? Assuming that the outer ball joint is the one next to the wheel, then this one doesn’t, in reality, move when raising or lowering the car. But if you are “moving” it just for simplicity in making the calculations, that would make sense.
An observation - Based on your calculations for 15mm drop, the 10mm drop MINI has used in the past for the JCW Sports Suspension is actually significant in terms of roll center and moment arms. Interesting!
Charlie - Sorry for my confusion, but ... Above you say “if you lower the outer ball joint 15mm”. Is this to make the angle of the LCA be at the “stock height” angle? Assuming that the outer ball joint is the one next to the wheel, then this one doesn’t, in reality, move when raising or lowering the car. But if you are “moving” it just for simplicity in making the calculations, that would make sense.
An observation - Based on your calculations for 15mm drop, the 10mm drop MINI has used in the past for the JCW Sports Suspension is actually significant in terms of roll center and moment arms. Interesting!
Yep, what I meant was, the LCA gets 10 degrees at the stock ride height. Level for me at 15 mm drop. Mind you I assume 12" for the LCA, but that's not too far off I reckon.
And I too am impressed by the apparent sensitivity of the roll center. How much roll do I want? The lower I go, the more I get.
Way down the rabbit hole aren't we?
And I've not yet tackled the dynamic behavior - add 1.5" of compression and now what? How about the effect of lowering the CG on the pitch axis? It isn't just roll..
Ok, the good news is that the 17x8wheels still fit with the new coil overs.
Yay! Tight (inner sidewall to shock body), but still a few mm clearance
I am still working with KW to get the two critical dimensions for the JCW Pro Coils - being total stroke, and stroke to bump stop. The hazard is Mini part #, versus "Article Number" from KW, and including the absence of any cross reference.
So the fat lady has not yet sung, as I do not yet know how much compression travel I now have, given the ride height.
Charlie - I would be happy to “walk” you around LRP and join up with you on iRacing. I have a friend in northern VT whose husband just got into iRacing and the last I heard he was doing 1:03. So you are doing well. Here is a good video:
This is a great visual walk around the Park that I can use for discussion. There are a few thing I would do differently in a MINI or other momentum car. He does have a great discussion for doing the down hill turn.
here is another video that has a few other pointers in it:
I hope these help. I wish I had a few of my later videos up on YouTube, but I lost the video editor for the camera I am using so they are languishing on the SD cards they were recorded on.
If you start a thread for iRacing around LRP, post a link here on this thread and I will get it.
Enjoy! And motor on...
BTW - Sam Posey was the first person to break the minute mark around LRP and that was in a Porsche race car. My feeling is iRacing is a bit optimistic on lap times. In real life I turn 1:05s +/- a little, with my best being a 1:03. A well driven Spec Miata is a touch faster than I am.
Thanks Eddie. One thing the MX-5 Cup and my car have in common, is that feathering the throttle induces a nice gentle oversteer, and accelerating pins the back end to the ground (with one notable exception).
So momentum, and don't lift unless you mean it!
The exception is the exit of the diving turn, where the **** end is hanging on by a thread, and unless I am mindful of unwinding as I enter the straight the car will cheerfully hook into the right hand verge!
I look forward to a bit of collaboration on the virtual track.
Thanks Eddie. One thing the MX-5 Cup and my car have in common, is that feathering the throttle induces a nice gentle oversteer, and accelerating pins the back end to the ground (with one notable exception).
So momentum, and don't lift unless you mean it!
The exception is the exit of the diving turn, where the **** end is hanging on by a thread, and unless I am mindful of unwinding as I enter the straight the car will cheerfully hook into the right hand verge!
I look forward to a bit of collaboration on the virtual track.
Cheers,
Charlie
I have a friend whose MINI was set up like yours and, while tracking out from the downhill turn, wound up in the tires on the inside of the turn. Oversteer can be a fickle thing...
The diving turn (down hill) has 2 parts to it. One is the turn in point which is a “breath” later than it appears. Otherwise you will be turning in too early and that will keep you from getting on the gas after the apex, which, as you noted, is necessary to keep the rear planted. I find I have a tendency to creep to the right before the real turn in point, which counts as turning in too early. Stay on the left side until the front starts to compress. The sweet spot for the turn-in point is small, but it is glorious when you find it.
The second part of the downhill turn is to fully apex the turn. That may be obvious to you, but you would be surprised to see just how many people don’t. Just touch the edge of the curb. There is a bit of a pocket there that will help you. Too much curb will send you off the track. Too far out from the curb means a slower exit speed and likely hinder your ability to unwind and get on the gas.
Unlike the “conventional wisdom” exiting this turn faster doesn’t gain you any extra speed at the end of the straight as you will hit terminal velocity (or close to it) In the Miata before you get to the T1 braking point. It will shorten your time on the straight which translates into faster lap time. Exiting this corner at a high speed also gets you a chance to run up along the inside edge of your opponent and beat that person into T1.
I catch a lot of much faster cars exiting this turn. And into T1 and into the uphill... Technical, so technical.
I needed a morale boost today, so I ran down to Fun Hondas in Maynard and chatted with Chang and Kim Soo while he meticulously put the good rims and tires back on.
Chang made me grin, wire brushing the mating surfaces of both wheel and hub, and putting a touch of anti seize on the periphery of the hub center. Meticulous.
Kim Soo would be two events into the season right now, running her HS Civic (setup by Danny Kao) instead of the karts she has been running since she was five years old. She told me she has a "Student Driver" sticker for the car, when we do get back to autocross later this year. I cannot wait. We chatted about her having to learn right foot braking, having used her left exclusively for ten years. Since I've gone iRacing, I've had to make the opposite shift, although I did LFB for two seasons with Gollum I it was many years ago.
It was nice to take that ride out into farm country, get the hell out of the house, and see both of them.
So now Gollum is butch again, and ready for competition. All dressed up and nowhere to go. A lot of folks have worse problems, so I know I'm blessed so far.
Those 225 mm RE-71s won't have much stick until things warm up, and at 5/32 they won't like puddles either. I'll be careful.
Speaking of iRacing, I spent three weeks tolerating a frame rate of 20-25 FPS while driving Lime Rock, Laguna, and the Glen - it hurt.
So I spent real money in this virtual world, 'cause that's how motorsport is, right? A shiny Dell G5 with a good graphics processor arrived last Monday. Christmas!
I set it up, and the wireless appendages, and the really nice headset, and LO I was at 85 FPS. That was at 6 pm Monday evening. I immediately ran a 59.x lap at Lime Rock in a Skip Barber car, which was a solid one second improvement just because I could bloody well see!
So I joined the NER SCCA iRacing League for their Monday night race - for practice mostly as they're really good and I have no racecraft to speak of. I wouldn't dare go past practice, not yet.
We were running the "ROVAL" at Charlotte Motor Speedway, and at 7:15 pm as I joined the one hour practice session I had two immediate experiences. The first was that the new computer kept up, despite over twenty five other cars on the same track, rendered everything well, and held the frame rate. The second was that my rather antique Thrustmaster wheel and pedal set became possessed and started generating random downshifts, and sometimes doubling an upshift.
So I now know what happens if you shift a ND Miata into first gear entering turn 6 at Charlotte.
The new wheel and pedals are due in at the end of this week.
Idle hands are the devil's tools. Last year's RE-71R tires have accrued 17,000 miles since they went on August 1st.
I protected them from the cold over the winter, but the spring weather highlights their one weakness - wet performance. They are now heartstopping on a wet highway, as there isn't sufficient tread depth remaining.
And maybe, just maybe, we'll go back to autocross in June - fingers crossed.
So I just purchased a nice set of Yokohama A052 in 225/45-17, ignoring the temptation of rolling the dice on clearances with a 245.
My distinguished colleagues in the New England Region recommended these, even over the stellar RE-71R, and the ST class results from Nationals last year underscore their credibility as a real contender for the Bridgestone's crown.
I now have an excess of readiness and a deficit of autocross events. A motorsport impactment...
Cheers,
Charlie
You are gonna LOVE those YOKOS. Tire Pressure will make a big diff. For me more PSI was a benefit AUTOxing. I do have to say that replacing my front bushings on the Lower Control Arm with the PowerFlex BLACK made a huge feel diff,,,
I'll bite Darby, what do you run for hot pressures with these tires please sir?
Since I've the 8" rims, I'd tend to moderate as in 35f / 40r. I like a waggy tail and run square alignment, so I usually go a bit high out back.
More?
Cheers,
Charlie
I went from running ~ 34FR/33rear (RE71s) and at first on A052s...then tried 38/36 and got a big diff. I have only run the A052s once at those PSIs so it is still a learning curve but the difference
was noticeable. Now that I have added the PowerFlex BLACK LCA Bushings it will be fun once we get to AutoX again...
I do appreciate all you suspension adjustments and have ordered some Bilstein 16 PSS10 Struts/Shocks w/ Compression/Rebound adjustments to replace the Bilstein 14 (that don't have Compression/Rebound adjustments) to fine tune. The 14's were great but I wanted to step it up a bit.
The Bilstein 14's which were only used for about 10 AutoXs will be for sale (only 2500 miles on them) for $500 OBO plus shipping
