MB

The more stiff the chassis, the more tyre load so yes, more camber potentially required.

But you are then getting into territory where it will not feel so nice on the road and get odd tyre wear, hence I mentioned you end up with a compromise.

You should base your camber requirements on your tyre wear - the tyres tell a story.

chrispayze

Think that's what I just decided!

Although 00-01 front ARB is pretty much the same as the CR, and more readily available, so I'll got for that first.

MB

Oops I was looking at the wrong numbers

If the below are correct, id actually be going for an 00 / CR front and keep the stadard rear or CR rear, combined with 8kg springs.


[CODE] | Front Rear | Front Rear
Model Year | Spring Spring | Sway Bar Sway Bar
--------------+------------------+--------------------
2000-2001 | 219 291 | 393 427
2002-2003 | 246 309 | 300 396
2004-2005 | 262 278 | 300 311
2006-2007 | 262 269 | 300 311
2008-2009 | 280 294 | 354 311
2008-2009 CR | 384 343 | 392 362

Note 1: All figures are in lb/in. Divide by 56 to get kg/mm.
Note 2: Edited 17Nov2010 with slight updates to spring rates per rev1 of paper

MB

Looking at the 00 rates, it's not surprising it was a lairy bast!

They really sussed it out on the CR that you need to go less rate at the rear for track use - all the other MY have the balance the other way around.

chrispayze

Ah, slightly softer rear than the 02. I'll see how I get on with the changes one by one and make a decision then. Thanks very much for the input.

chrispayze

Thought I'd post an update following an airfield day at Keevil today. It started off wet, and dried throughout the day so it was a decent test of some different conditions. I have replaced the front ARB with one from a MY99-01, retaining the stock rear (MY04) and the 10kg/mm coilovers all round. I'm no driving God, but I think I've done enough track days to sense reasonable differences in handling.

Firstly, the S felt great all day and didn't miss a beat, ultra reliable, no brake fade on 20-25 min sessions (DS2500s, no dust shields), no oil usage (Castrol Edge 5W40) and happily jump started a Boxster and a 5 Series which had flat batteries! I LOVE Jap reliability (especially when maintain fastidiously by me)! It felt nice and progressive at the limit. I had a fair few moments where the back end started to come round, both under power and braking, and none of it happened suddenly. I really enjoyed the day.


Wet:
Given that it's an airfield, the tarmac retains a reasonable level of grip in the wet, but it was plenty slippery enough to find the limits, although I was taking it pretty steady. The car did seem a little more neutral, with both end seeming to react fairly equally to the same slippery patches. It seemed to be a little more predictable than previously. I only did a couple of wet runs though, so didn't get too close to the limit in most circumstances. The change seems positive in these conditions though. Good for the road too.

Dry:
Roll is reduced, there's no doubt about that. I kept the damping on the coilovers at lower levels that I had previously and didn't feel that the car was as wallowy through direction changes. Once I built up my confidence, I pushed harder through the faster corners (up to 80mph entrance, balanced throttle fading to full throttle on exit) than I felt comfortable doing last time (pre ARB mod). And there was gentle 'push' as I started to get close to the limit (there was probably still a reasonable margin, but that's more down to my driving skill and nadger size!). For fast corners, this gave me a lot more confidence.

For mid speed corners, I noticed that I did really have to be on the brakes or on the throttle to get the car turning well. It does understeer a little more if I've on a balanced throttle. Worth having to 'coax' it for the high speed confidence though.

For the tight hairpin, mid corner front end grip was a struggle. I remember it being slightly like this previously, but I do believe it is worsened by the stiffer front ARB (which makes sense from a theoretical standpoint). This is borne out by the slightly worn edge to the outside front tyre too, which clearly isn't getting the weight transfer that it used to. I tried upping the rear damping and reducing the front, which did help, but perhaps I could have done this more. I didn't want to upset the balance in the fast corners though.

Thoughts for the next change:
I am tempted to go for a slightly stiffer rear ARB, but I don't want to diminish the predictability, especially in the wet. Hence, my thoughts are turning to increased camber at the front wheels. My theory is that the camber would give a bit more grip when front is being pushed hard, like the hairpin, but in the wet, the car wouldn't be able to generate as much load, so the contact patch would remain smaller, giving more understeer (and 'safety') in the wet. And the balance in the high speed corners won't be as upset as it would be if I upped the stiffness of the rear ARB.

What do people think? Is the camber change likely to be too subtle to give me the results that I want or do you think it will do the job? Current camber settings are -2°10' rear and -1°20' front.


Thoughts from learned gentlefolk very much appreciated, and hopefully this thread will document the effects of some of these changes for other people to refer to later.

mdb_75

I can't help too much, but I've played around with my suspension a little like you have, except I kind of went the other way as I have a 1999 S2000.

I felt mine had way too much oversteer when on track. To reduce it I fitted front OEM struts off a 2004 to stiffen the front whilst keeping the 1999 front Arb.

At the rear I left the springs as they were, but I swapped the roll bar for the slightly softer 2002/2003 one (which is harder than your 2004+ bar).

The results are that my car is a lot more predictable than it was and I'm not constantly worrying about loosing the rear, it felt so loose before!

I was thinking about trying a 2004 rear bar, but maybe that would be too soft. Perhaps you should try a 2003/2003 rear bar or try and find a CR one which is somewhere between what you have now and a 2002 one?

I'd have liked to have done Keevil today too, I did it in June and would like to have compared things now that the cars a bit different.

Did you do any in car filming?

chrispayze

Thanks for the info, interesting that we're heading to a similar place from the opposite end of the spectrum!

If I were to upgrade the rear ARB, it would be the CR one I'd go for (as also suggested by MB above).

I recorded a few sessions on the GoPro. I'll post some links when I get round to editing and uploading them. No overlay this time though, track recorder plugin for Torque didn't want to record more than 34 seconds.

MB

I'd say leave the bars alone now, and tune the dampers to see if you can get what you need.

Check your front tyre contact before adjusting camber.

A lot of people run more rear than front camber, which imo isn't the way to go on a staggered setup. Your narrower fronts need more camber than a wider rear. I have 2.5-3 front and just under 2 rear.

s2konroids

Interesting is that camber setup suitable for the road.