sorry to have missed this thread - you should have told me you made it! thanks for weighing the mini - we've got pretty similar options, so i have to imagine our car weights will be pretty similar. i passed on a couple things you have, but also added seat heaters, being that i dont live in cali =P

am i understanding right that that's the car weight with a full tank of gas? Assuming gas in somewhere between 6-8 lbs/gallon, the car will probably clock in at around 2400 even, with slightly more front weight bias

looking forward to reading your build. I definitely wanted to run with FCM's suspension, but I think it's just too much for me to start with. I am going with the JCW stuff though. Also, not to be in your business, but damn that is an expensive rear bar - may I ask why your decision to go with this one rather than HSport's comp bar? I think similar rates to the one you purchased, at about half the price. We may have brushed on this once in a different thread, but I forget what you said

 

I'd guess I had about 70lb more gas than I really wanted, so he's danm near 2400 when running.

I never saw the H Sport bar in my researches, but I really like the engineering in the Tarett bar, it really is a work of art. The separate lever arms allow you to change the bar without dropping the rear subframe, you can also get an even stiffer bar, you just have to change bar not the lever arms. I wish they did one which was slightly softer. The bar and lever arms only weigh 7.1lb.

 

gotcha - definitely a well engineered piece!

 

There's waaay more that goes into the determination of understeer/oversteer than weight distribution and roll stiffness. For one, roll stiffness is also a function of front and rear spring rates + motion ratio, as well as other suspension stiffness (bushings, bump stops). Secondly, there are a whole host of other factors that play into the mix...tire pressures, alignment (camber, caster, toe), tire temperature, suspension geometry, course conditions, etc. And this is all assuming steady state cornering.

My point is, I don't see any value in hypothesizing what the "ideal" rear sway bar size is for "perfect" balance. You want enough adjustment where you can go from understeer to oversteer if possible by only changing the rear bar. This will give you a tuning handle to dial the car in to your liking. The tricky part here is that with several other variables to alter and the potential for interaction effects, the possible combination of settings is quite large.

Personally, I run the Hotchkis 25mm hollow bar on the middle setting. It allows for good throttle lift rotation and I can typically adjust balance to surface conditions with tire pressures. There might be some gain to be had by adjusting the bar for different surfaces/conditions, but for medium grip asphalt it seems about right to me.

I rolled my car across some scales during an event this year. '09 w/ heated seats, fog lights, 16x6.5 tire rack wheels, 1/4 tank or less (I don't remember exactly), stock exhaust: 2415lbs. Wouldn't be too hard to get below 2400 with a lighter exhaust, less gas, lighter wheels.

 

btw, did you weigh the car with the 17s? and did you have the spare pulled out of the car at the time?

 

Bertie was weighed with the 16" wheels, just as Cathy had driven him at his first event, just with a full tank. So no spare or tools.

 

gotcha, thanks. seems i can expect the mini to be veeerry close to 2400# even as it sits

 

I just found out, I'm not going to have the modded suspension for the next event. I've been gently poking FatCat to find out the status of the order, I sent two emails, but heard nothing. So I rang them, the person who answered said he'd leave a message.

Later this evening I got an broadcast email saying due to other commitments he'd be late on orders.

Very annoying, they said being done by this weekend shouldn't have been a problem. After this weekend's event the next one isn't for a couple of months.

So now I'm contemplating fitting the bar myself before this weekend's event. I think I could manage that. I'd have to cut the old bar to get it out, then the new one can be threaded in without dropping the rear subframe. Cathy doesn't like the idea of destroying the old bar, but the labour involved in getting it out would be about the cost of a new one. This method also has the advantage of not disturbing the alignment, so it wouldn't need to be aligned.

The idea of changing one thing at a time (bar then shocks) is attractive, so we can see what difference each individual change makes.

To complicate matters, the weather forecast is threatening near freezing temperatures for this weekend's event (at least in the early morning). I was also planning on testing the new tires/wheels against the old tires/wheels to see what the difference is. The cold morning might skew the results, our regular run group is first out, the second run won't be till sometime in the afternoon.

 

Still not heard anything about the new suspension. I should bug them, our next event may be on the 18th of January, when the BMW club is doing a "rewind". That is doing a fun run on a course from this year. I think I might take Algy instead just to see how he compares.

I'm also selling the wheels we used for most of this year: https://www.northamericanmotoring.co...-5-wheels.html

I'm looking at getting some Enkei RPF1 with 225/45-16 ZII tires. Then I'll test the 15" Rivals vs the 16" ZIIs.

Our tire test last weekend was inconclusive because of the weather. The two tires performed about the same, but the Rivals were 20 degrees colder. I'm satisfied the Rivals are better than the RE-11s.

 

Good for you!

As a man of science (I think you said that you're a physicist by training), I'm surprised you didn't choose this route from the onset of your build. Otherwise, you'd never have known which change made the best impact in lowering your times.

 

that's EXACTLY the setup I decided to go with - 16x7 Enkei RPF1s, with 43mm offset, and 225/45-16 Z2s lol.

 

The new wheels/tires should be here Monday. They'll also work as track tires, I'm intending to run Bertie at a few events next year. The Rivals are a bit short for track tires, I've found a taller tire to be advantageous.


The plan was to change both, because I hadn't thought about it much, it should have allowed us to get the changes done this year, and its cheaper to get it all done at once. If the back end is already being taken apart, its only an extra hour to fit the rear bar.

Now I have time to think about it, I'm considering rearranging matters to make one change at a time. I could fit the bar myself and still get to our first event on Feb 9th. Then get the shocks fitted for the next event on March 3rd. In between there's MINI Thunder track day at Thunderhill (missing the SFR event 2) and possibly another track day at Laguna as well. February is going to be a busy month.

 

I got the rear sway bar installed today. I went the easy route and payed our independent shop to do it for me. I haven't pushed it yet, I'm going to save that for an autocross. I'm going to be careful with this on the street. Its currently set to full soft. Finding the right stiffness is going to take some experimentation.

I had hoped to be able to adjust the bar by poking a nut driver through the wheel to loosen the nut on the droplink and be able to move it to a harder or softer setting. That would allow me to adjust the bar at an event, which would make tuning it a lot easier. But the nut on the link is hiding behind the brake rotor. So I took the wheel off and investigated lengthening the drop links. The link ends can be screwed and unscrewed to change the length.

First problem was the shop had really tightened so I had great difficulty undoing the nut. Then when I get the nut loosened, the bolt would turn with it. So adjusting it by poking through the wheel would be difficult without getting a wrench to the back of the bolt.

After lengthening the links so I could get a nut driver on the nut over the brake rotor, I put the wheel back on and it bumped on the lever arm of the bar (the fancy CNC aluminium bits). There was very little clearance between the arm and the rim. Lengthening the link reduced the clearance. So I reduced the length of the link again and put the wheel back on. There was more clearance, but not much. Now I'm wondering if I could fit the 15" wheels over the arms. I'll try that at the weekend. I'm pretty sure a 15x7 wheel wouldn't fit (I'm fitting the 16x7 wheels). A 15x6.5" wheel (such as I've got) might fit due to the angle of the arm.

In other new, I splurged and went halves on some corner weight scales with another local autocross guy. The scales are more for interest, as there's not a lot you can do to affect the corner weights in Street. So I did some weighing. In street trim the weights are:

Empty:
762 764
471 492
total: 2489

With me as driver
847 807
571 530
total: 2755

Autocross to win has somethings to say about corner weights: http://farnorthracing.com/autocross_secrets11.html His theory is that with an offset driver they're never going to be equal. So the best you can do is to get the front and rear to both have the same left/right distribution. He has a handy calculator to check this. Plugging those numbers in, Bertie is quite well balanced, the corner weights balance within his suggested 5lb.

Once I put him in race trim (race wheels, ad take out the tools and spare wheel) with a 15% full gas tank, he weighted 2400lb. Once I put in the cameras, harness and helmet he was back up to 2410lb. I also disconnected the sway bars.

The corner weights were, empty:

763 754
463 420
2400

with driver:

843 796
483 538
2660

The corner weight calculator shows that's not so well balanced, the weights are off by about 25. Who'd have thought MINI actually balanced the car well as it came from the factory.

One interesting note is autocross to win suggests that if you get any change in corner weights when you reconnect the sway bar, you have some preload in the bar. I had the crazy idea that you could actually adjust the corner weights by adjusting the preload in the rear sway bar. The new bar's adjustable droplinks would make that quite easy. I'm not sure if that would help or just make things weird.

I also weighed the new and old bars. The new bar is slightly heavier, 3.27kg vs 3.04kg. (Half a pound heavier.) That's actually good, if the new bar were a solid bar of equivalent stiffness it'd be 4lb heavier.

 

A quick picture of Bertie with the Enkei wheels. (And the new bar, but you can't see that.)

Also I've swapped his front pads for EBC Yellowstuff in preparation for taking him to a few track days. For autocross I was planning on stock pads and letting the dealer pay for them. Though I like the way the Yellowstuff bite, but that may be just the break in coating.

 

I notice this thread is light on pictures. Here's an action shot with the Rota slipstreams.

 

ho ho looking good! are those rpf1's in 16x7? did you powdercoat them?

we probably already talked about this, but what exactly are you running? im going 16x7, those wheels, et43, and 225/45-16 tires, z2s are really the only option as of now.

did you ever get your dampers from fcm???

 

They're RPF1 in 16x7", +43 offset. With Dunlop Z11 in 225/45-16. They're not coated (at least by me) they came that way from TireRack. Enkei offers then in Black and Silver, the black look better. I already have 17" versions for Algy (currently with 215/45-17 Bridgestone RE-11A), so I like they way they look. I'll actually be using the 17" wheels at MINI Thunder so I'm not heat cycling the Z11s too much before testing them.

Still no dampers from FCM. I need to chase them up. Even if I got the dampers, I won't be fitting them until the end of Feb or middle of March. I'm going to run with just the sway bar for an event or two first.

 

I've been fiddling with the sway bar again. The 15" wheels have more clearance than the 16" wheels do. I adjusted the links again, so I could get to the nut, and the 15" wheel had about 1mm of clearance. The 16" wheel rubbed on the lever arm. So I adjusted them back to give more clearance, all of 4-5mm. I think I could get more clearance if I reseated the arms on the bar (pushed them further onto the bar). But the shop has tightened the locking nut so much I can budge it with my hex key. I might get a hex bit for my socket set and see if I can move it.

For working on the links, a couple of 17mm wrenches are very useful. I just picked up a couple with a box end on one end and an open end on the other. All the nuts and bolts are 17mm. (Which is the same size as the lug bolts, so I have sockets to fit.)

I also worked out that if you twist the tubes which make up the endlinks, it adjusts the length of the links. (I had thought that they were threaded so they'd stay the same length.) There's a handy hole in the middle of the tubes to poke a screw driver through to get leverage on it. I may need to adjust the length of the links when adjusting the bar stiffness, so that they don't bump into anything. Its looking like adjusting the bar stiffness is a more involved operation than I'd expected. Its needs to have the back raised and both wheels off.

 

ahh, that's EXACTLY what im going with, but decided to go silver (on black car) may powdercoat white though.

sadly i think i may be autoxing on stock suspension this year though

 

I got a new tool that should allow me to adjust the rear bar more easily. It offsets a 1/2" drive socket by about 2". I should be able to get at the nut even when its behind the brake rotor.



I'm also getting some unhappy sounding noises from the rear right. I'm taking him back to the shop to get looked at (and heard). There's a bit of a clatter, or chatter from back there. I've looked over the suspension and can't see any problems. I even checked the torque on all the bolts they'd have to have touched to get the bar in.

 

My H sport bar works itself loose at the end links about once a month, I'd double check those before taking it anywhere. The other common clunk when I have the Konis in is the top nut on the strut working loose, but you are still bone stock, right?

Also, FWIW, I was like "oh I'll switch it back to soft after every event" and I think I maybe did it twice before deciding it wasn't worth the hassle.

 

The shop thinks its the droplinks. Everything's tight, but with the teflon coated spherical bearings the links rotate freely. In fact I just adjusted them so that they rotate the most. That could be causing the chattering. Now I've got to work out how to quiet them down.

 

I tried quieting the bearing by packing them with rubber washers. That quietened things, but now I'm not convinced the link rotating was causing the noise. The other link is just as free to rotate and its quiet. The only thing I can think of is I didn't manage to tighten the link properly, but with a bit of preload which stopped this being apparant. As soon as the suspension moved, it rattled.

I've taken out the washers and things are quiet again. There is a bit of squeaking. I've heard you can lubricate the bushings to quieten that.

 

did u ever receive ur ssr wheels?

 

I'm not expecting any SSR wheels (my current ones are for sale). I was trying to get some Volks, but I'm not worrying about that until I find the 15" tires are better.