UrS4 coilovers - how stiff springs for trackday use?

[Thuppu]

I'm planning on fabricate coilovers for my UrS. How about the spring stiffness and lenght?

What would be about right stiffness for trackday use? I don't bother about soft ride quality, I wan't it quite stiff. Car weights propably close to 1600kg. Also wonder about the spring lenght, should I use a longer spring or a shorter one with a support spring? How does the spring lenght effect the overall stiffness?

Here is all springs that are available quite near me: http://www.lautamakimotorsport.fi/kynajouset.htm

The guy that owns that shop told I could try 850lbs in front and 500lbs in rear...


Edit.

Does anyone have experience of adjustable Spax chocks?

[Thuppu]

So no one have experience with this C4 big chassis on track? Somehow that 850lbs sounds quite much..? Have also seen that many use stiffer springs in the rear with these quattros to keep the front wheels on the surface.

Found a coilover diy by EDIGREG and he have used 450 in front and 500 in rear, and somehow I belive that is still quite comfort. What if I try something like 650-700lbs, the same in front and rear?

http://www.motorgeek.com/viewtopic.p...0999&start=500

[Wrath]

You should talk to 2bennet or what the company is called, I think they do coilovers for the C4 and they should probably know.

http://www.2bennett.com/body_type44suspension.html

Many US members that use these and seems to be happy about them

[Thuppu]

Maybe I'll just buy these and get the sleeves and other parts. http://www.ebay.de/itm/Gewindedampfe...item1c3d2784e8

If the dampers arn't good and the main springs are too loose, then they can be uprated. If I buy the parts separate from here(can't even get sleeves for 55mm struts)it would cost for one strut 55e/sleeve kit + 50e/support spring + 11e adapters between the main- and support spring. Thats 232 euros for the coilover parts I need for the both front struts. Plus the main spring and a better damper either way.

[Error404]

For track I think 800lb - 1000lb sounds in the right ballpark. I would use stiffer rear springs to dial out the understeer

[philj]

Springs are down to preference, obviously it's good to get a starting point from other people, but you'll probably find yourself with a few sets of springs which is no bad thing. I wouldn't recommend the supersport set for the track, the dampers are budget, ok for the road, but on track will most likely overheat, cavitate and blow. You will need dampers valved to suit your spring rating if want to get the best from them.

All depends on how low you go. If you aren't going low, then a sleeve that just screws onto the damper like the Supersport or TA, a custom damper insert and springs will be fine. If you're going low and want to retain decent handling, you'll want to lower the steering arm, and ideally the ball joint. The strut could be machine slightly so you could flip the steering arm. Ball joint will need proper heat treated spacers. Top mount will need modifying to get some camber back.

Someone got Spax to make some custom rear coilovers? They probably have the drawings still. I'll be getting Gaz to do the same, and probably use the TA front adjustors.

[andy10v]

You will need a good set of shocks with higher spring rates as well, they need to be able to control the springs, and not get blown apart.

Edigreg has re valved Biltseins.

If you are going low you might want shorter shocks to regain travel.

[Rusty]

For track I think 800lb - 1000lb sounds in the right ballpark. I would use stiffer rear springs to dial out the understeer

For a McPherson strut, that's about right for a pure track setup. For a road useable setup, 500-600 is more like it.

As above, get the dampers shortened to remove the need for helper springs.

You need to know the strut free length, axle weight & spring rate to calculate compression & desired strut length for the ride height. From all of this, you can identify a spring or series of springs that match all criteria.

[Thuppu]

Good info here guys, thanks. Sure I'm avare of that I need good chocks to clear the stiffer springs. Maybe I will cut the steering arm off the strut and lower it, like in edigregs thread in motorgeek. Just waiting a reply from bambridge if he can supply sleeves for my sruts. I also have yellow Koni shocks that I have been thinking to send for refurb, and they could modify them for stiffer setups.

[macspring]

All depends on how low you go. If you aren't going low, then a sleeve that just screws onto the damper like the Supersport or TA, a custom damper insert and springs will be fine. If you're going low and want to retain decent handling, you'll want to lower the steering arm, and ideally the ball joint. The strut could be machine slightly so you could flip the steering arm. Ball joint will need proper heat treated spacers. Top mount will need modifying to get some camber back.

Someone got Spax to make some custom rear coilovers? They probably have the drawings still. I'll be getting Gaz to do the same, and probably use the TA front adjustors.

Phil, when you're doing this, if you could post some photos of the before, during, and after, as while I think I understand what you're saying photos would be even more helpful for me.

Thanks.

[Thuppu]

For a McPherson strut, that's about right for a pure track setup. For a road useable setup, 500-600 is more like it.

As above, get the dampers shortened to remove the need for helper springs.

You need to know the strut free length, axle weight & spring rate to calculate compression & desired strut length for the ride height. From all of this, you can identify a spring or series of springs that match all criteria.

Yes, this is only for trackdays, not a full scale track build. Something like 1000lbs will propably bee way too much even that this is a quite heavy car.

[quattro84]

How heavy is your toy Thomas? (I have a calculation sheet i made whilst i did my engineering degree, shall try to dig it out) would reckon 900lbs for front & around 2/3 of the stiffness for the rear so say 600lbs for the rear max.

Buy from Faulkner springs, dead cheap so easy to try a set.

For a McPherson strut
...
You need to know the strut free length, axle weight & spring rate to calculate compression & desired strut length for the ride height. From all of this, you can identify a spring or series of springs that match all criteria.

Don't forget strut inclination and leverage due to mounting location.

[Thuppu]

Well, I havn't weight it. UrS4 is lighter than UrS6, and my doesn't have aircon, so 1600kg would propably be quite close... Don't know how the axle weighs are, but all engine weight is on the front axle, and I'll guess the Avant is heavier in the back than the Sedan.

[Thuppu]

Here is a vid that shows clearly one reason why I need stiffer springs: http://koti.mbnet.fi/pro-ht/Videot/mov/testlaunch.mov

[Error404]

......and a new door trim strip