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miller_himself

S15 Suspension Setup For Time Attack

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I'm building a trackworthy s15 and looking for advice how to setup my suspension properly.

My specs are: 8j 235/40/18 fronts, 9j 255/35/18 rears, tein 10k/8k coilovers, everything else in suspension is stock. Past year i ran slightly differnent setup - 215/45/18 and 235/40/18 on the same rims and an old coilver set. The car performed not so good on a track - it used to lift rear inner wheel while cornering and the rear was jumpy.

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Are you running street tyres? Same tyres front and rear?

 

Start with an alignment:

Front: 2.5 degrees camber. 0 toe

Rear: 1.25 degrees camber. 2mm toe in.

 

If you have stock rear arms you might need to change the camber and toe ones to get the rear setup properly.

 

Your coilovers might be a little bit stiff but should be ok, if you wanted you could move the 8kg rears to the front and get a set of 6kg for the rear.

 

I assume you're running stock sway bars? If it's still has too much oversteer try disconnecting the rear sway bar.

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I'm running ad08r all around. Sway bars and rear arms are stock. The car doesnt have to much oversteer, its just lifts one wheel so i unable to accelerate mid corner. But this issue was on an old set of coilovers - i dont know yet how the car will handle in on the new ones.

Edited by miller_himself

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sounds like too much rear roll and not enough suspension travel causing suspension to lift?.. cant say much more as not much info has been provided. could be a million things which also means millions of ways to fix it.

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mods in this order progressively

front and rear anti roll bars

front castor rods

rear camber, traction rods & maybe tie rods if your stock ones are out of adjustment

 

and whatever you do, don't slam the car flat on the ground... it actually ruins handling

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mods in this order progressively

front and rear anti roll bars

front castor rods

rear camber, traction rods & maybe tie rods if your stock ones are out of adjustment

 

and whatever you do, don't slam the car flat on the ground... it actually ruins handling

 

spring rates are way too high

that would be the first thing i would change

 

8kg front 6kg rear

 

whiteline sway bars front and rear the motorpsort blade adjustable

 

you probably need more aero too.....

Edited by kdog

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Nothing wrong with spring rates, I run 10/8 and that works well for me. As long as shocks can support these spring rates you'll be fine.

 

Definitely need more travel though if you're lifting a wheel. Try raising the car somewhat. Also make sure your bushings aren't causing bind, non-lubricated poly bushings can become tight and stop the suspension arms moving, so check and lubricate them if necessary.

 

What track are you mostly doing btw?

And what alignment settings?

What tyres?

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Are you actually doing time attack? Or just club days?

 

what has that got to do with anything? either way he's chasing times.

May not be a WTAC car however...

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The way i see it is a time attack car relys on aero for grip, where a normal circuit car mainly relys on suspension and tyres

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Are you actually doing time attack? Or just club days?

 

Don't see much difference also. We restricted on our track days to compete each other, so we chasing time (moslty ha ha). I'm planning to add aero elements later in this year after i overcome my suspension issues. Front splitter and rear wing, just like on sx developments s15.

 

Nothing wrong with spring rates, I run 10/8 and that works well for me. As long as shocks can support these spring rates you'll be fine.

 

Definitely need more travel though if you're lifting a wheel. Try raising the car somewhat. Also make sure your bushings aren't causing bind, non-lubricated poly bushings can become tight and stop the suspension arms moving, so check and lubricate them if necessary.

 

What track are you mostly doing btw?

And what alignment settings?

What tyres?

 

My bushings are stock also. I think i had too stiff rear coilovers, i'll try to raise a car a little bit and set shocks to the most soft settings.

 

I have two tracks nearby, one is 3.2 km long, counterclockwise direction, i will mostly run on this one.

 

track.gif

 

and the other is about 3-4 km long (depends on configuration), also counterclockwise

 

mraceway_big.gif

 

I will stick to settings what aformentioned above.

Start with an alignment:

Front: 2.5 degrees camber. 0 toe

Rear: 1.25 degrees camber. 2mm toe in.

 

the tyres now are advan neovas ad08r.

Edited by miller_himself

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Those alignment settings are fairly conservative I reckon. Up to you how aggressive you want to go.

I run:

Front: -4 deg camber, 3mm toe out

Rear: -2.5 deg camber, 0 toe

 

If you're lifting a rear wheel then you need more shock travel. Softening the rebound will be worse if anything, it wont help with lifting the inside wheel.

Stiffer sway bars will reduce roll, I would do that first.

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Those alignments are for street tyres. I would add half a degree of camber all round for semis and maybe up to 2mm of front toe out.

 

Im running slicks and only running 4 degrees and 2mm toe out front, 2.25 degrees and 2mm toe in rear.

  • Upvote 1

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Cool circuits, where do you live?

.

 

Its near Moscow.

 

I will stick to the sc s15's settings because they look reasonable for a daily driven car. Already looking for a thicker sway bars. Thanks guys.

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Thicker swaybars with those spring rates will

Make things worse. The spring rates with stock bars should work reasonable well. Post a pick of your car plz. I bet it's pretty low and the suspension can't do its job.

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Why low suspension can't do its job? I have separate height adjustment on my coilovers and wheels dont rub arches, dont understand how lowering car can worsen handling except adjustment limits (minimum camber -1 etc).

 

Here is the pic:

 

7709700852_d216c55473_z.jpg

Edited by miller_himself

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http://www.motoiq.com/MagazineArticles/articleType/CategoryView/categoryId/120/Ultimate-Suspension-Guide.aspx

 

http://mcablog.com/?p=409

 

2 of the best articals on the net. My attitude an s15 was exactly like yours. Once I lifted my car, yes lifted it and set it up to allow the shocks to work with correct suspension geometry my times dropped significantly. It's something you may have to learn from experience and by playing with your car but I can guarantee the height it's set at now won't allow you to get good use of your coilovers.

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Make sure you read every part of the moto iq one. I think it's part 1-7. The mca one shows an explains that you bottom adjustment on your coilovers isn't completely for height adjustment, it's more so for setting up and positioning shock travel and stroke.

  • Upvote 1

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There is a minimum/recommended wheel hub to guard length that is ideal for shock travel on an s-chassis, hence why lowering too much is bad for handling on an s-chassis

 

If you squat down and look at your lower control arm (both front and rear and tie rods), if it's not horizontal to the floor, then it's too low and needs to be raised

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As above that's a simple way to put it but the mca artical is a gem on suspension install and setup!

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Great advice abovve, especially regarding suspension geometry. Upon lowering a car, you're lowering it below what factory intended it to be. Those bent arms you see after lowering it causes excess bodyroll because of the roll centre being affected negatively at angle rather than the control arms being perpendicular. There are ways to counter this.

  1. Purchase Driftworks knuckles for the S-Chassis. This will allow up to 50mm roll centre correction for the front and 45mm roll centre correction at the rear which also means you can wind up those coilovers accordingly (more stroke) and much less chance of hopping or lift with better overall grip. Downfall is you lose the standard Ackerman angle. Typically, cars are pro-Ackerman so the front inside wheel turns at a higher degree of radius at the front for steering which is better for low speed corners as it allows for turn-in, for you this might not be a huge problem until you meet the low speed corners on a track. You're looking at just over 1000 pounds delivered. Provides better lock and less effort to complete a full lock. IMHO best upgrade, Ackerman can be altered by buying upgraded steering arms which allow for Ackerman or modifying the knuckles. Link here: http://www.driftworks.com/driftworks-geomaster-hubs.html
  2. Ikeya Formula lower control arms allow for some roll centre correction, I'm still trying to figure out how much it corrects roll centre by though, about the same price if not, more than the Driftworks knuckles.
  3. Moonface Pro SuperLap Roll Centre Adjuster - balljoints, read that these split after a few track sessions so not ideal if that's the case.

I also used to get the rear inside wheel lift as you mentioned. After I installed rear toe, camber and traction arms I had loads of grip and the rear inner wheel hop is gone.

 

My setup is the same tyres are yours, I HIGHLY recommend Achilles 123S Racing for track days, not sure how they work in cold temps though but by far the grippiest tyre I've used. AD08R might just be as good though, haven't tried them yet.

 

I use:

Front: -3.5 camber, 2mm toe out (-), Castor at 9.5 (anything above 7 is normally good, Ikeya Formula also do these well).

Rear: -2 camber, 2mm toe in (+).

 

Good luck and keep safe.

  • Upvote 1

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so i just read the MCA guide.. and what got me is when they mention adjusting ride height with spring seat and not from the bottom like we all thought it was designed for and dont worry if spring is loose or not captive at your ride height choice.

 

am i interrupting it wrong or is this how it should of had been to begin with? (spring being loose when at droop level)

Edited by AE86557

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You read it right! The bottom adjustment is really there to set up where u want your range of shock travel. Obviously if you just wanna slam your ride it won't make much sense and the artical won't be to usefull but if your setting up for track you'll find your spring 9 times out of 10 won't be captive/loose

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My setup is the same tyres are yours, I HIGHLY recommend Achilles 123S Racing for track days, not sure how they work in cold temps though but by far the grippiest tyre I've used. AD08R might just be as good though, haven't tried them yet.

 

I use:

Front: -3.5 camber, 2mm toe out (-), Castor at 9.5 (anything above 7 is normally good, Ikeya Formula also do these well).

Rear: -2 camber, 2mm toe in (+).

 

Good luck and keep safe.

 

I've heard about these tyres but sadly no one sells them here. Instead of this we have Z222 for decent prices. But they are very sensitive to outside temp and performs badly on wet so i desided to buy ad08.

Why do you set 2mm toe out on the front instead of 0 as suggested above?

Edited by miller_himself

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Toe out in the front promotes turn in

 

I run 0 toe up the front as well

 

My settings are:

front: -3 camber, 0mm toe, 7.5 caster

rear: -2 camber, 1.2mm toe in

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Toe out in the front promotes turn in

 

I run 0 toe up the front as well

 

My settings are:

front: -3 camber, 0mm toe, 7.5 caster

rear: -2 camber, 1.2mm toe in

 

 

Correct, I prefer toe out for hills and winding corners but on a track with higher speed corners I would stick to perhaps +1mm out or 0 toe and test between them for the best result for my setup, the track and environment.

 

I also realised that you lowered the S15 as shown in picture without rear camber arms. I lowered my car to your height and I was forced to use -4.8 camber at the rear which eliminates grip fast because the contact patch isn't sitting on the tyre correctly, even around corners. It's forced on the outer shoulders of the tyres which should only be induced under hard cornering, not all the time.

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I also realised that you lowered the S15 as shown in picture without rear camber arms. I lowered my car to your height and I was forced to use -4.8 camber at the rear which eliminates grip fast because the contact patch isn't sitting on the tyre correctly, even around corners. It's forced on the outer shoulders of the tyres which should only be induced under hard cornering, not all the time.

 

i don't had such problem, after i installed these coilovers i was able to set about 2-2.5 of negative camber.

 

 

Installed new tyres on the past weekend - car feels completly different, worth every penny.

Sadly, i've noticed oil leaks from the shocks and now looking for new coilvers.

Which one of these will be more suitable for track days?

 

7F, 5R or 9F, 7R?

 

http://www.tein.co.j...=1&srchfrwd=S15

Edited by miller_himself

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Hks hyper max 3 same price as tein in an 8/6 rate and the shocks work atreat. Should be 1800 through streeter. Don't go heavier than 8/6. Once you install them you will never look back.

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