SE autocross and suspension thread.

Started this thread so we can swap notes on SE autocross setup.
I've been autocrossing my SE since September.
It's an absolute hoot. Most courses are very safe. It is possible to hit hard or squishy things, but that usually requires an excess of stupidity. A few courses have areas where I do avoid driving at 11/10ths as I am wary of obstacles should I completely lose it.
My first event, I was showroom stock apart from a bit more air in the tyres.
Next one, I stiffened the rear ARB by 25% by adding extra holes. At some point after that, I obtained falken 215/45-16 RT660s. Then I got some crash hubs to add another -0.5° camber up front.
Sometimes I do fairly well, sometimes less well. Being a relative noob, that's to be expected?
At my best event I raw timed 4 of the 6 street class Porsche's there. 2x Caymans and 2x 911s. Damn, I was smug after that!

My last event I had a fast codriver. I think he made a bigger difference than the tyres did. He sometimes wins the SSC class at local events. No surprise, he smoked me. He didn't catch my usual class nemesis, though. I do learn a lot from ridealongs and seeing how he drove my car was educational and well worth the rubber and being bumped down to 3rd.

I am sticking to street stock class. GS for our SEs. Mods are limited, which is a theoretically a good thing for my wallet.

Today, a honking huge 25mm rear ARB turned up. Almost 10lb worth. Stock one is 3 ½lb, according to realoem I'll check that when I get it off. I'm a little skeptical about it as I was getting good rotation at the last event, though with tyre pressures pretty close. 42F, 38R, hot. But so many people have said a bar is the way forward...

I have been curious about the F56 suspension specs and have found no hard numbers. I was very, very impressed with the lack of bump steer I couldn't measure some months ago.
I reversed one rear wheel onto a ramp earlier.
The wheel in the air dropped an inch, the one on the ramp compressed 3 inches. With a kerb weight spec of 3150lbs and a 54/46 weight split, I came up with:

Spring wheel rate of 180lb/in
ARB wheel rate of 60lb/in.
Rear frequency 94cpm

I calculate my modified stock ARB at 240lb/in.
So, looks like a 50% motion ratio for the ARB.

The 25mm ARB on 'soft' came out at 550lb/in. Hard at 690lb/in. The ICE cars it is usually bolted to have around 2/3 the weight of an SE's fat butt. That was what finally persuaded me to get one. I may investigate sprung links if it is a little much for daily dodging.

This is fairly crude way to get spring rates. I think it should be within +/-10%, though. The ARB numbers being the most sketchy. But good enough to find the ballpark. I'll do the front at some point, too. I'm expecting a wheel spring rate of around 200 there.

If the weather cooperates tomorrow, I'll get the bar on.

 

Oops, can't count. I need to try again.

 

I got the new bar on.
I haven't seen a description of how to bar an SE, so here goes. It's pretty similar to an ICE F5x. Except the battery is adding extra fun.
If I'd had this guide, I may have done it in 3-4 hours.
It's a tedious job.You will need a selection of E-torx sockets. I mostly used a deep set from a car parts store. The ARB brackets I used a short E12 socket and 3/8 ratchet. Original bar links need a a torx, 30, I think, to hold it while the nut is removed. Might get away with an allen key. A variety of expletives is also useful.

Get the back up on blocks, pull the wheels.
Remove centre plastic from back of car and ones on each radius arm. 8mm nutdriver FTW here.
Photo time if you have any doubts about putting it back together how it looks now
Disconnect original bar.
Unclip hoses from bottom track arms.
Unclip brake hard lines from body clips nearest each hose. The left side is not visible. Grope for it. the line going right in the hidden clip can stay put.
Unclip wires down to hubs in the wheelarhces.
Check to see there isn't smething else fragile I've forgotten to mention.
Unbolt track arms from radius arms. Inner ends can stay on the subframe. The bottom arm sets the camber, so mark it if you don't want to be doing an alignment afterwards. The battery prevents dropping the subframe to access the front ARB clamp bolt, but it can be pulled backwards instead if the track arms are disconnected.
Unbolt shocks
Push radius arms down and fish both springs out
Unbolt battery from subframe and subframe from the body.
Pull subframe back 2-3 inches
Wonder why, oh why, Mini didn't put captive nuts in the ARB brackets and bolt through from the other side.
Unbolt the ARB clamp bolts. The rear is easy, the front ones are why we take half the back end apart. Pull/pry the subframe back and down until you can get at them. I used a short 3/8 E12 socket and ratchet. If I did this often, I'd mangle an E12 wrench into a C-shape, weld a socket on and get the front ones from underneath
Remove bracket from ARB. Original ones have bushes bonded to the bar, don't try getting those off...
Carefully finagle the bar out. There are things it will catch on, be careful.
Tea break, you are 1/3 of the way there!

Finagle the new bar in. Make sure it is the right way up! I went in from the right. There is a brake line on the left that the bar needs to go underneath. A new larger bar isn't keen on that. It may be easier going in from the left. Slow and careful avoids damage...
If your bar comes with lube, smear it in the bushes. Mine was silicone, Goop doesn't work on that, so I used goof-off on my hands too. Or, be smart and wear gloves?
Bushes on the bar. Mine were split, so easy to get on. I temporarily removed the grease nipples as they were in the way of the wrench for the front bolts.
Many people think that the clamps should be shimmed so that the bar rotates easily. I am not one of those people. Torque setting may not be any good as the clamp needs pulling down a way until it seats. You should feel it snug up tight in about 1/4 turn when it finally gets there.
Put the grease nipples back on. Much easier before you get the subframe back in place!
Persuade the subframe back home. Try to get the brake lines clipped back in to the body clips when it is nearly there. easier than when it is there.
Fit all bolts loosely, then snug them up and back off 1/4 turn. The battery ones need to be a bit loose. With the bolts to the body almost tight, use a piece of wood and heavy object to get the battery bolt shadows lined up. If you put everything back where it was, no alignment needed. 5-10 minutes here can save you an hour later.
Snug all the body bolts up. Snug up battery bolts. Check washer shadows are still good.
Tighten body bolts 100Nm, 74ftlb
Tighten battery bolts 100Nm, 74ftlb. The Shop manual actual calls for new battery to subframe bolts and 74ftlb + 90 degree. If yuo are reusing bolts, go maybe 15 degree.
Reattach track arms, jacking up the hub to normal-ish ride height makes this way easier. Snug the bolts but don't tighten yet.
If you are changing the bar links, they are much easier to do before the springs go back in. I set my adjustable ones to 95mm
Refit the springs.
Jack the hubs back up and get the shock bolts in. Snug, but don't tighten
The bottom track arm link and shock bolt should be tightened with weight on the wheels. The top track arm seems to get a free pass in the sho manual. I suspect that is because it is damn hard to reach with the wheels on. I jacked the hub up to about nomal ride height and tightened it. Jack was already there from the shock bolts...
Attach top of links to bar.You shouldn't have leftover parts other than plastics and wheels by this point

Fit the plastics and wheels and drop the car. I dropped mine onto 4" concrete blocks so I could still squeeze under. If you don't have an E12? wrench, you'll need to leave the radius arms plastics off until the camber bolts are set and torqued
Do your chosen alignment on the bottom camber adjusters and tighten. From marks or do it properly, your choice 100Nm, 74 ftlb
tighten shock bolts 155Nm, 114ftlb
get the car on the ground

Test drive then a beer.

View from the back, after pulling original bar. The plastic thing at the bottom is a jacking point.





View from the right side, after bolting new bar to subframe. Only 2 hours to get the job done from here! I pretty much knew what I needed to do by this point. Disassembly had some dead ends I wasted time on.

 

Race report!
Well it might look like the same car, but it's completely different.
Huge amounts of rotation.
I started with 37F, 34R pressures.
Let 2+1 out of the rears after runs 1 and 2
Finished with 40F, 34R.
Sprayed fronts after run 3.

It is very controllable, though. While it probably looked wild, it never got away from me. Several corners each run I was still sideways with the front inside trying to spin.
I need to change my technique to drive this. I suspect it is a bit too much bar for the car, but will try some more events.
First run was dreadful. I picked up 4s over the next three. I felt I was still several seconds behind where I'd usually be. Judging by other entrants I usually beat or am close to.
Still smoked the cop in a Crown Vic, though.

 

Missing photos below. They were showing up, then they weren't.
I did make a post or thread about adding holes to the stock bar. Can't find it now. Holes are about 5/8 inboard of originals. They stiffen the bar about 20%. The fun part was squishing the bar flat.
I got a set of NM links for the jumbo bar.

 

F56 stock and aftermarket sway bar rates.
Standard on the SE is the 917 bar. This is also used on the cabrio with standard suspension. Cabrios run softer bars than hardtops.
891 is usually used on base models. 918 on some S's and JCW cabrio. 919 on newer S's and JCW hardtops.
Stock bars have quick codes of H4-H7.
Now I have one off, I can measure it a bit better. So numbers are little different to post 1. Somewhat lower.
Stock bar lever arm radius is 6 ⅛" my extra holes are at 5 ½"
My WMW hollow 25mm (actually 1"+powder coat) has holes at 5 ¾" and 6 ½" I've used these number for the stock and aftermarkets bars. Whiteline makes a solid 24mm, HR does a solid 25mm. There is a 23mm bar advertised, but it's actually 22.2 according to buyers. Most bars appear to be made from inch size tubing. So I've calculated from the nearest inch size. This is not surprising due to inch sizes still being industry standard. Yes, you get any size you want, but a standard size will be cheaper. I measured my 917. I see that bushes are available for 20.8, 21.4, 21.8 F56 bars, so used that for OD
There's also a 'Hardrace' 22mm hollow bar available. This may just be baby bears' porridge for our SEs. It isn't sticked in the USA, though. So $$$$$hipping...
These numbers are not super accurate. However, they were all calculated the same way, so should provide a decent comparison between bars.

Personally, I think a 25mm hollow is a bit much for an SE, especially with my skill level. I have done several nice full throttle drifts with it, though!
New stock bars a little under $200. I may grab a cheap 918 from eBay and add extra holes and see how that works. My stiffened stock bar was absolutely fine for road use. 919s are scarce on eBay. Maybe JCW owners aren't often tempted to upgrade?

Stock
917 H4. 164lb/in. 198lb/in
891 H5. 187lb/in. 226lb/in
918 H6. 214lb/in. 259lb/in
919 H7. 240lb/in. 291lb/in

Aftermarket
22 solid. 353lb/in. 440lb/in
24 solid. 464lb/in. 578lb/in
25 hollow. 550lb/in. 686lb/in
25 solid. 602lb/in. 749lb/in

 

It wasn't a huge difference. It was certainly cheap, though!

 

Rear bars are interchangeable. The standard SE bar is also the non-sport cabrio bar.
The centre kink in the front bar is different to ICE Mini bars, so we are out of luck there. Maybe someone will start making them.
The SE has a somewhat smaller roll moment arm than the ICE Minis. This is partly from a slower centre of gravity, partly from a higher roll centre. So if it had ICE bars, it will roll less, despite its extra weight.
It's a shame that Mini didn't offer a sport suspension package with stiffer ARBs. Roll is my biggest enemy on autocross courses.

 

Yeah, I've found very little on tweaking the SE online. There's also serious lack of actual information on what is available. I'm a big fan of swapping factory parts.

But to hell with facts, it's opinion time! I found my uprated stock bar to give a little more rotation than standard. But I still had no problem getting it to understeer. I think an 891 or maybe an 918 would be fine for the street. Used ones are around $100 on ebay. My hollow 25.4 is definitely a bit much for street use. I doubt it will see winter daily dodging duty.

 

I usually autocross in mid and always with DSC 'off" It isn't really off, just dialled back. Sport is too touchy with the throttle. Traction control even cuts power in roller mode. Though roller mode does kill the ABS. TC also seems to cut power if you are particularly sideways. I'm pretty sure I spun at my last event after it cut power on me in a drift. That is not a good feature on a loose FWD car.
I have yet to try an autocross run in roller mode.

 

I did a second event with the big bar last weekend.
Short and tight course. I'd never been there before.
I actually did very well. For me, anyway . Class win and my time would have put me 2nd in E street against all those damn Miatas . I also raw timed every CAM-C car . I am modifying my technique for the bar. The trick is to be back on the throttle once the car starts rotating. Brake, turn in while moving foot back, gas around and out. Overdrive this bar and it it gets messy, fast. It's teaching me to drive properly.
17th out of 86 on Pax sounds great , but there were 30 novices!

I also got two fun runs. The first I tried in sport rather than mid and went 0.6s faster. The last funrun was at 11/10ths to get even more practice at fixing my frequent overdriving errors. That was still 0.2s faster than all my official runs and probably quite entertaining to watch. My hands weren't really fast enough, everywhere...

I'm limited by rear grip with this bar. But it is good for for getting rotation on tight corners as well as forcing me to be less ham fisted. I'm sure I've been lifting the inside rear wheel off the ground all over the place. Once that inside rear wheel is off, the bar has helped all it can with lateral weight transfer. At some point, I'll try a softer bar than this one but stiffer than stock. I don't want to daily this one over winter.

1st funrun, my quickest run of the event.