Trackday suspension. - Saxperience

Simo^p · 5th August 2006, 14:25

If possible, Id like to start some serious chat about trackday suspension setups. Whats good, what's bad, etc, etc.

On the last two trackdays Ive been to my rear end has felt very very light. The cars stripped out but I think the problems arise from diagonal roll... ie front dips into a corner, causing the rear wheel to lift due to the stiff suspension.

I currently have Bilstein shocks on the front and rear. Standard torsion bars and ARB's on the rear. The front has been lowered with GMC 40mm springs (blue).

I guess the answer is stiffer front springs... so what are the options?

bullit · 5th August 2006, 19:30

you wanna be having campdavids track day set up then. 200 pound springs 22mm rear bars and 25 arb. his billies are revalved sports but as your running group n's they wont need to be.
then theres all your mounts and bushes, roll cage.
this is the steup that i might be going or ill have 21mm bars and lower powdage springs(180) more for fast roading. ill tackle that when i come to it.

as for you rear end i take it you stripped it after you fitted your sus because this has happened to mine aswell. the weight off the back has risen the rear up and its not balanced or as you said your fronts not being stiff enough if not

Barry123 · 5th August 2006, 19:46

stiffer anti roll bars simo.

Also your tyres look like they're having a hard time (certainly when taking the cornering load), so maybe reduce the profile.

GreenSaxo · 5th August 2006, 20:02

get some springs from faulkners mate.. you know it makes sense!!!

Frevo · 5th August 2006, 20:58

I've taken mine to a track recently, and it actually wasn't too bad.
Just look at the difference between yours and mine:

And that's with -50mm GMC springs and Koni dampers (and a full cage).
Not the same corner (obviously) so hard to compare, but mine doesn't seem to suffer much from body roll at all. I think -50mm GMC are stiffer than the -40mm versions.
Why not go for coilovers?

Frevo · 5th August 2006, 21:00

Quote:

Originally Posted by adsayer

stiffer anti roll bars simo.

Also your tyres look like they're having a hard time (certainly when taking the cornering load), so maybe reduce the profile.

I always increaser the tyre pressure for a trackday.

Ax_beefy · 5th August 2006, 21:08

You will need to stiffen the rear in proportion to the front, if you have a stiff front and soggy rear the front will dig in and you'll lose rear grip... too stiff on the rear and you'll skip sideways..... if the stiffness of front and rear are kept in proportion you should minimise the diagonal roll but it wont dissapear... like said get a full cage to stiffen the chassis as this is why you get diagonal roll because the movement in the front is amplified as it travels through the chassis

Barry123 · 5th August 2006, 21:12

Quote:

Originally Posted by Frevo

I always increaser the tyre pressure for a trackday.

I thought that but doesn't that comprise the grip at all?

Ax_beefy · 5th August 2006, 21:20

Not if you do it right you need to put as much in as is needed to create the greatest surface area on the track whilst retaining the solidity of the tyre

Barry123 · 5th August 2006, 21:22

cool stuff.

Wouldn't reducing the pressure increase lateral grip through increasing the surface area and flex of the tyre? and increasing the pressure would do the reverse?

Ax_beefy · 5th August 2006, 21:25

Well sort of, but for general road use manufacturers tend to state pressures that are abit too soft, which suprisingly helps in the wet, but on a dry track solid tyres is best and fastest

Frevo · 5th August 2006, 21:34

Quote:

Originally Posted by adsayer

cool stuff.

Wouldn't reducing the pressure increase lateral grip through increasing the surface area and flex of the tyre? and increasing the pressure would do the reverse?

Not if low tyre pressure means driving on the sidewall like in Simo's pic

Barry123 · 5th August 2006, 21:38

Quote:

Originally Posted by Frevo

Not if low tyre pressure means driving on the sidewall like in Simo's pic

oh yeah! good point (hence the lowering of profile

)

williamsvts · 5th August 2006, 23:24

what tracks have you been driving? were these fast tracks where the rear felt light?
strange for it to be like that with standard rear and stiffer front.
were your rear tyre pressures not higher than the front?

Ax_beefy · 5th August 2006, 23:30

He's got uprated shocks on the rear.... when I put my shocks on the front I didn't put the rear on for a couple of days and my god did it kangaroo round islands!....

Simo^p · 6th August 2006, 00:32

The tyres are 205/40/17. I dont think a lower profile is the answer, as its already damn low. The pressure of all tyres was 32psi.

Ive only noticed problems when going around tight corners at 85mph+

Hard to compare with your photo Fred, as it looks like you are clear of the corner, whereas my cars still flying around the corner. Also, I've seen the way you drive...

I have Grp N shocks front and rear and Grp A engine mounts and a rear roll cage.

Whats the deal with coilovers? Does someone sell a kit to suit the standard hubs/strut bottoms, or is it a weld on conversion???

CampDavid · 6th August 2006, 11:02

Tyre pressures don't make a massive difference, the argument is that you need to raise the pressure for a stiffer sidewall or lower the pressure as the air in the tyre wil get hot and this will expand and increase the pressure anyway. I run mine at 36 as a rule and it seems fine.

As for your suspension issues I think your bang on about it being the springs. GMC efforts are soft as fuck are the reason the car is pitching wildly like that. A set of custom springs will sort that out nicely for you, see the difference bellow in the amount of lean through the long right hander between me and Widders, who was on a set of 50mm springs at that point I believe

Faulkner allow you to specify the poundage of the springs and the length. Mine are 200lb which I think is just right for road use an trackday, a few people have 180lb and some have gone harder with 225 or 250 lb, PGTIs stock hatch 106 has on something crazy like 300lb but that would be a nightmare on the road. Once you've worked out the poundage you want you can decide on the length which will give you the amount it lowers the car by. I can see that your a bit of a style whore Simo so you'll probably want to specify a length shorter than mine as I'm only down 10mm. There is a thread on the SSC where everyone with faulkners put up there specs and how much it dropped the car by, I can't link to it though as the SSC down.

Coilover wise I'm a bit green but you should be able to achieve the same sort of results but keep the car a bit lower down. Like I say though, advice on this is better coming from elsewhere as its not something I've looked into much as I can't see too much advantage in it and the costs are very high, plus I don't want to lower my car to much as I don't like the slammed look that much and it fucks up all the geometry angles.

After springs you may want to look at stiffening up all the bushes and mounts with pug sport kit or similar and increasing the size of your ARB and torsion bars. a 25mm ARB is ideal and about 100quid from pug sport, or you can nab a 24mm one off a 106 GTI or Rallye as they had the thicker ARB as standard for some reason. Torsion bar wise 22mm is ideal for matching up wth 200lb springs and gives a really nice setup. 23mm is availible but may wel be to hard fr road use or 21mm, which matches the 180lb spring very well

bullit · 6th August 2006, 18:13

can you run 200 pound springs with standard rear torsion or is it best to do both at the same time?

CampDavid · 7th August 2006, 09:39

You can, an upgrade of the ARB would help stiffen it a bit but peopl;e have done it. I did everything on mine all at once which makes it hard to comment for sure, though others seem to think its fine

Simo^p · 7th August 2006, 15:42

Quote:

Originally Posted by Simo

Whats the deal with coilovers? Does someone sell a kit to suit the standard hubs/strut bottoms, or is it a weld on conversion???

Anyone? Advice/pics??