staggered tires versus non, wide versus non: questions

[leegf]

hello -- i'm new to these cars and just had a few basic questions. assuming all other variables are constant (tire make/model, tire pressure, etc.), how would the following setups behave differently from one another in a track environment? for the sake of argument, assume an 'extreme summer' street tire like the dunlop direzza z1 star spec is used, since that will most likely be my case:

- 205/50/16 front, 225/45/16 rear
- 205/50/16 all around
- 225/45/16 all around

i like the idea of being able to rotate the tires front to rear, but will a staggered setup result in more neutral handling in these cars, or does it just introduce understeer unnecessarily? not sure what the consensus is among track-oriented folks (my car came with a staggered setup, fyi). and does the added width of 225 tires all around result in noticeably more grip over 205 tires all around?

thanks!

[JMPAuto]

Stay with the square setup. I run 205/50/15 Star Spec all around and car handles really good on the track. No need for extra wide on the rears unless you have lots of power.

[CincinnatiKid]

My guess is unless you're running massive amounts of HP or a veteran racer, you won't notice a difference. I'd stick with same size on all 4

[Hellabad]

Same size all around. You will always need more front grip than rear grip until you get 500hp, and even then....

[Emre]

.i like the idea of being able to rotate the tires front to rear, but will a staggered setup result in more neutral handling in these cars, or does it just introduce understeer unnecessarily?

An E30 is one of the best balanced cars you're ever going to drive. The car is neutral with a square setup. Stagger is going to shift the cornering balance towards understeer without any benefit. Plus, you're going to limit your options for tire rotation, which is never a great idea on a track-driven car.

not sure what the consensus is among track-oriented folks (my car came with a staggered setup, fyi).

Square set-up with 225/45R-15 all around is preferred amongst track junkies.

and does the added width of 225 tires all around result in noticeably more grip over 205 tires all around?

That is going to depend to a large extent on whether you have enough wheel width to make use of the extra tire width. Tire construction will also be a factor. To a lesser extent, suspension set-up will also contribute.

If you'd like to run 225/45R-15 rubber, Ideally you'd like to have 15x8" wheels. But 15x7" will work, especially if the tires have a stiff sidewall and your suspension has enough roll resistance to keep the wheels upright. With stock suspension and less aggressive tires, you may actually have better transient response with a 205/50-R15 tire on a 15x7" rim.

[leegf]

thanks everyone, i think my questions have been answered. i have 16x8 wheels now, so it sounds like 225/45/16 all around would be ideal for a track setup, or perhaps 205/50/15 all around if i were to change to a 15x7 wheel (which is a possibility).

[dreeves]

The only issue with the 16" fitment is that the tire selection is very narrow. No RA-1s, NT-01s, etc -- you're pretty much limited to the R888, a yokohama and perhaps the Hoosier R6.

Welcome, btw. Love the blog.

[balooshinakus]

Everyone always says that the e30 has traction issues due to its poor rear suspension design, wouldn't wider rear tires help compensate for this and allow more power coming out of corners?

[Brian D]

The traction issues are generally at the front, due to the Macstrut/lack of camber gain of the stock front suspension.

[Emre]

Everyone always says that the e30 has traction issues due to its poor rear suspension design...

No one who knows what they're talking about says that. Even with a 240+ hp S50 under the hood, there's no shortage of traction.

If anyone is critical of the rear suspension, it's because (like the 911) it tends to snap into oversteer if you lift off abruptly in a corner. Those of us who know how to drive properly actually like how easy it is to "throttle steer" an E30.

Sticking huge, low-profile rubber in the rear of a car with this type of suspension tends to ruin the delicate balance: the car gets more twitchy at the limit, with more sudden oversteer that's tricky to control. That's the main reason why a Z3 M-Coupe is slower around a track than an E46 M3, even though they weigh about the same and have the same engine (at least later S54-powered M-Coupes do).

The traction issues are generally at the front, due to the Macstrut/lack of camber gain of the stock front suspension.

Exactly. Which is why the E30 tends to understeer less when you put on heavy front swaybars and run high front spring rates. This is the opposite of conventional wisdom regarding suspension tuning.

[Fusion]

I agree with the above, though my view comes from only about 3 hours track time.
I run 15x7 with 205/50 tires all around and I love it. You have the feeling you know exactly what each wheel is doing. And I have experienced unintentional oversteer out of corners, ie. on first laps before the tires (steet spec Conti's) got warm, but I just let it flow and have never felt out of control or unsafe (for myslef and others at the track). It just feels natural and brings a huge smile upon your face. But I am going to try to get rid of the slight understeer into turns with IE sway setup.

[leegf]

thanks everyone- lots of useful information here.

[SA E30]

What is your suspension setup?

I run 225/45/17 up front, and 235/40/17 in the rear on my car, Bridgestone semi slicks. Although though I have a 800lbs springs all around (true rear coilover), stock sway in the rear and h&r in the front set to it's stiffest setting.

Car is very neutral in turn in, and mid corner, I cxan get on the power rather easily on corner exit.

[leegf]

this is how i acquired the car (to the best of my knowledge):

- E30 M3 5-lug swap
- IE Stage3 springs
- Bilstein Sports
- 25mm front IE sway
- 19mm IX rear sway
- E36 M3 offset control arm bushings

these seem like sensible mods to me, but others here obviously know more. do any of these mods not make sense?

[txtorquemade]

this is how i acquired the car (to the best of my knowledge):

- E30 M3 5-lug swap
- IE Stage3 springs
- Bilstein Sports
- 25mm front IE sway
- 19mm IX rear sway
- E36 M3 offset control arm bushings

these seem like sensible mods to me, but others here obviously know more. do any of these mods not make sense?

Set up Id like to run. Im sure others will come with something though. Im sure sway reinforcements, poly subfs and RTABS will surface. Id like to do that too, to a track rat.

Id like to know whats the optimum spring rates for a Autox/DD combo.

Not to threadjack...or nutin.. yanno...