Looking to dial out understeer

[Nihilation]

Initially I had the idea of fixing my lack of front grip in tight turns by tossing on more meat(235+). If I look at the problem closer I think maybe that's kind of the "band-aid" route that creates other issues. Rubbing, possible TCS issues, the need for wider/heavier wheels to fit properly, etc. Alignment plays a huge role obviously, and should be looked at first and foremost. I recall back when I autocrossed my E36 BMW- originally the car had a minimal 1 degree of negative camber. When I stepped it up to 3 in the front the increase in front grip and turn-in feel was enormous. Like driving a totally different car. Now THIS was turning!

I'm going to skip the beefy front tires for now and start with the obvious- swaybars and an aggressive alignment. I'm only at negative .6 degrees in the front now, so I'll probably try 2 degrees of front camber with 1/8" total toe out, and retain the 1.3 degrees in the rear that I'm running now with OE toe specs. Should do the trick!

I'm really surprised this hasn't been brought up yet. SPACERS!! Increasing front track would help a lot.

If I still need more grip then the next step would be looking into more front rubber, or possibly a little less in the rear.

 

[docjohn]

You will have a tough time getting more than 2 deg - camber in front unless you are lowered enough to help out.Spacers work in theory but again if you want to do that to a degree that it might help you will end up with tires pushed beyond your fender ,,not recomended.Our cars come with oem wheels with pretty high offsets for a reason.

 

[sjs]

Agreed, spacers are not a good first step and have the same worries about rubbing as do wider tires, but with fewer benefits. They also require longer studs. For sure, rotating unsprung mass is the downside to bigger tires so get the lightest wheels you can find, but apparently that wasn't very important when you bought steamrollers for the rear.

 

[Nihilation]

For sure, rotating unsprung mass is the downside to bigger tires so get the lightest wheels you can find, but apparently that wasn't very important when you bought steamrollers for the rear.

I bought lightweight wheels. =) 18x9.5 = 18lbs without tires. The fronts in 17x7.5 are 15lbs. Thanks.

 

[sjs]

That's great, I'm actually impressed. The tires are still heavier than narrower ones and all that weight is at the outer circumference, but you are still way ahead of a lot of guys who buy big "pretty" wheels without a clue of the real impact.

 

[RacerX-21]

I haven’t read every post so excuse my slower entry and early on the gas. Do you push everywhere or in a specific place? Corner entry, middle of the corner, or exit? Not to sound condescending because at one point I asked the same questions. To make it easier for everybody, it’s simple physics solved mostly by manipulating weight to the area that needs traction. This can be done in many ways that vary in different circumstances like budget or car geometry. Some of the examples-
Tire pressure differences
Driver input!
Sway Bar adjustments
Spring adjustments
Ride Height adjustments
Tow adjustments
Camber adjustments
Down force adjustments
Caster adjustments
Weight Adjustments
Tire Size
Rebound adjustments
Corner balance
Low speed compression adjustments

Give me specifics about where exactly your condition takes place and I can give you a better answer of what I would try first.

All of these adjustments can help but you will start to develop an order depending on where the condition is.
The same list applies to braking.
I developed a constantly evolving cheat sheet for what to work with in any condition. Last Note- Keep in mind that there is always a tradeoff, better in one area makes it worse in another. The trick is to find a happy medium or determine what the most important locations are to master on the track. The same principle as sacrificing a corner to improve another. Some teams maximize passing zones and some maximize their weakest areas, it all depends on strategy. Oh, and keep in mind that you should be careful not to chase down a problem that is caused by assumptions. By assumptions I’m talking about relying on another shop to do your corner balance or alignment specs, or assuming the conditions of your tires are the same as when you first ran them. Ok, it’s really my last note- My guess is camber, even the locals with secondary or occasional street use NSX’s that want them to rock on the track, I have reworked them to have –2 degrees of camber. (I understand that’s not for everybody)

 

[Scin]

I couldn't get anymore then 1.5 degrees up front with mine.

I bet if you do the max up front (probably less then 2) and play with sway bars you can find something that will make you happy.

Initially I had the idea of fixing my lack of front grip in tight turns by tossing on more meat(235+). If I look at the problem closer I think maybe that's kind of the "band-aid" route that creates other issues. Rubbing, possible TCS issues, the need for wider/heavier wheels to fit properly, etc. Alignment plays a huge role obviously, and should be looked at first and foremost. I recall back when I autocrossed my E36 BMW- originally the car had a minimal 1 degree of negative camber. When I stepped it up to 3 in the front the increase in front grip and turn-in feel was enormous. Like driving a totally different car. Now THIS was turning!

I'm going to skip the beefy front tires for now and start with the obvious- swaybars and an aggressive alignment. I'm only at negative .6 degrees in the front now, so I'll probably try 2 degrees of front camber with 1/8" total toe out, and retain the 1.3 degrees in the rear that I'm running now with OE toe specs. Should do the trick!

I'm really surprised this hasn't been brought up yet. SPACERS!! Increasing front track would help a lot.

If I still need more grip then the next step would be looking into more front rubber, or possibly a little less in the rear.

 

[titaniumdave]

I couldn't get anymore then 1.5 degrees up front with mine.

I bet if you do the max up front (probably less then 2) and play with sway bars you can find something that will make you happy.

Good point, remember stiffer sway= less traction. To get more turn in bite, try a stiffer rear sway, more damping on the rear shocks or less damping on the front shocks.

A stiffer front sway will reduce body roll AND reduce front grip, increasing under steer as you approach the limits of adhesion.

 

[Nihilation]

I couldn't get anymore then 1.5 degrees up front with mine.

I bet if you do the max up front (probably less then 2) and play with sway bars you can find something that will make you happy.

Even if I manage to get 1.5 that's still 3x as much as I'm running now(-.6), so I should notice at least a little improvement.

I was gonna say "Should I consider running less rear camber?" but I think I'll hold off on that until after I hit the track again.

As far as swaybars go I understand that it's effectively adding more understeer if added only to the front but I really want to get rid of the body roll, it's crazy. So further thoughts about the swaybar:

Adding them to the front obviously reduces body roll and as titaniumdave stated, also increases understeer. That's why they come in pairs. Stiffen the rear to compensate.

There needs to be a nice "total" combo kit out there that works well, similar to what NISMO does for the 350Z, or what Eibach sells.

Dali has a Street and a Street/Track swaybar kit. Advertised as 30% and 100% stiffer respectively. I know these are just numbers, but doesn't it seem pointless to purchase a swaybar set that's "only" 30% stiffer? Is that even enough to notice a difference? When combined with a suspension that's 30% stiffer overall I could see it, but when running Bilsteins on OE springs? It'd be nice if I could retain the balanced feel, with a lot less body roll.

Would it be a bad idea to just add the Zanardi rear swaybar?

 

[titaniumdave]

Do one thing at a time or you don't know what you like. Change the front camber and go back to the track. I can notice a 0.2 degree difference, I am sure you will notice a 0.9 degree change, might be all you need!

I personally don't like more sway on the rear than the front, I am running a 7/8" front with the stock rear sway and am happy with the balance using 235 front and 275 rear tires. When I use my street tires, 215 front, 265 rear, I reduce my front damping to increase bite on the front end and get better turn in.

You can also play with tire pressures to see how things feel with less grip, put 2 lbs. more in the rear tires and see if that helps get the rear to slip sooner. The nice thing about pressure is you can make changes all day long, cost you nothing and takes almost no time to do, only one tool too.:biggrin: