Increase Spring Rate or Thicker Front Sway?

[3002 tii]

Currently running 255 square, -2.8 degrees up front, AST 4100 450/550. Car is pretty neutral in my opinion but I realized as I learn to carry more speed into turns, I find myself needing to trail brake more to increase the front end grip. In order to rotate the car better, is it time for me to look into

a) stiffer springs
b) thicker front (only) sway
c) re-analyzing my lines?

I know the 450/550 combo is soft compared to what others are running but this was TCK's recommendation and I find it perfect for the tracks I've been on. Rear end doesn't get get loose on bumps and still civilized enough for street. My only concern however with upgrading to a thicker sway (25mm factory, 27mm H&R) is the dreaded sway bar tabs from factory. I know it'll only be a matter of time before they rip although I suppose I can always add reinforcement from the beginning.

Thoughts?

[seank]

Is there a (d? A sway bar will decrease roll progressively but has negative consequences of lifting the inside front wheel. Increasing front springs will decrease roll in thefront but both of theoptions won't rotate the car. They both will promote push. You can add more camber in the front if you need it, or you should stiffen the rear spring rate.

Btw: the faster you learn how to drive, you will trail brake andleft brake more. I trail brake or left foot brake nearly to the apex of every corner.

Set the car up with the most important corner in mind.

[pokeybritches]

I thought you soften the springs on the end of the car that needs more grip (or use stiffer springs on the opposite end)? /answerfromatracknoob

[007MCoupe]

sub'd. sorry i don't have anythign to add constructively.

[JasonH]

If I was going to upgrade the front sway bar I would just have reinforcements welded in at the same time. That being said, I would probably be inclined to go with a set of front/rear adjustable bars like Ground Controls so you could fine tune them. Of course, bumping the front spring rate up would be easier and cheaper so I would probably try that before messing with the sway bars.

[RobMCoupe]

I'm not expert by any means.

Have you consider getting dual adjustable front struts to fine tune your suspension? My understanding is adjusting rebound can provide oversteer/understeer.

[3002 tii]

I think we're all just waiting for the Hack to chime in.... =P

[Finnegan]

+1 on The Hack, his input is always helpful. Sean gave some good input as well.

We already have pretty stiff bars, stiffer front bar will increase grip, but at the limit will promote understeer. If you're driving well enough to be at the limit a good chunk of the time, it may have the opposite effect of what you're after. And there's the reinforcement requirement too.

If you don't have a pyrometer, I'll make a plug for one. The car may well need more negative front camber, or it may need tire pressure adjustment, but you'll never know until you read those tire temps. We can guess at optimal camber settings and pressure for our driving style and needs, but the pyrometer provides hard data, and it provides very quick feedback on changes. It's also useful when changing springs, bars, etc. down the road.

My vote at this point is to not change the setup, but to continue to work on your trail braking and transistion, and set your alignment based on pyrometer data. Push it to the limit with your existing equipment, plus tweaks, and add in skill improvement. Once you've exhaust that, then look at other set-up changes.

[RADRACR]

Originally Posted by Finnegan

but you'll never know until you read those tire temps.

So what are optimal tire temps? Also, is it the same difference to calculate by cold/hot PSI?

[Kgolf31]

Originally Posted by RobMCoupe

I'm not expert by any means.

Have you consider getting dual adjustable front struts to fine tune your suspension? My understanding is adjusting rebound can provide oversteer/understeer.

Compression will help adjust understeer in the front and oversteer in the rear. SA shocks already adjust rebound.

Compression deals with the unsprung weight, aka wheeling the wheel on the ground

Originally Posted by Finnegan

+1 on The Hack, his input is always helpful. Sean gave some good input as well.

We already have pretty stiff bars, stiffer front bar will increase grip, but at the limit will promote understeer. If you're driving well enough to be at the limit a good chunk of the time, it may have the opposite effect of what you're after. And there's the reinforcement requirement too.

If you don't have a pyrometer, I'll make a plug for one. The car may well need more negative front camber, or it may need tire pressure adjustment, but you'll never know until you read those tire temps. We can guess at optimal camber settings and pressure for our driving style and needs, but the pyrometer provides hard data, and it provides very quick feedback on changes. It's also useful when changing springs, bars, etc. down the road.

My vote at this point is to not change the setup, but to continue to work on your trail braking and transistion, and set your alignment based on pyrometer data. Push it to the limit with your existing equipment, plus tweaks, and add in skill improvement. Once you've exhaust that, then look at other set-up changes.

Z4M has stiff bars, not a Non-M though.

I'm upgraded to a 30mm and experience tire lifting on RS3s with OEM shocks and springs.

+1 on a pyrometer. It will really tell you what your tires are doing

[seank]

Originally Posted by pokeybritches

I thought you soften the springs on the end of the car that needs more grip (or use stiffer springs on the opposite end)? /answerfromatracknoob

You can do that. If he doesn't have enough camber though, the softer springs on the front will need more than he doesn't already have. Stiffer spring on the rear will help rotate the car as you mentioned.

The cheapest option and probably the best is to do what Finnegan said.

-know tire temps readings (15 degree difference from inside to outside.) If you need more camber, add more camber.
-if you still need a looser car, increase rear springs by 100lb.

This is where I would start.

[Finnegan]

Originally Posted by aestheticstorm

So what are optimal tire temps? Also, is it the same difference to calculate by cold/hot PSI?

Answer is dependent on the type of tire, and there's an optimal range, not a single target temp. R-comps have a higher operating range. If you've got pretty even temps across the tire, but you're outside the operating range, your slip angles are probably too high and you're over driving the tires (which means less available grip). Pyrometer is good for all kinds of assessment. Here's a good little piece on this topic.

You take the temps hot. Basically with a probe pyrometer it's like checking the temp with a meat thermometer. Really.

Originally Posted by Kgolf31

Z4M has stiff bars, not a Non-M though.

Forgot about that. Still think looking at camber/tire temp across the tire is a good place to start, and then follow Sean's idea for the rear end with springs. But it never ends as we all know! (Mods anyone? )

Lots of good ideas and input in this thread--I've learned a thing or two. Always more to learn!

[pal]

I am not a fan of sway bars for suspension tuning unless there are absolutely no other options.

I'd say start with tire pressures on track in 1psi increments and work that along with adjusting lines. Usually works if the basic setup is good and you are fine tuning.

Shock adjustments (compression and rebound to match) are next. I like to do that at home using a trial and error method on my local loop near my house. I don't like to do this at the track as then it becomes a test and tune day rather than having fun and improving driving skill.

Next would be spring rates. Have you though about softening the car a bit? Maybe 400lbs up front and 500lbs rear? You can do it in two steps- soften front first and see if it makes the rear too loose and go from there.

You will never have a setup that works perfectly on all tracks and conditions unless there is a team working for you Get the basic setup to a point you are happy and just fine tune small things when needed. That is my theory anyways, so take it for what it is.