Wide Tires

[Stunnd65]

I'm bugged. ghead I was in the market for new tires and wanted to go with a wider profile than the stock 205s. I saw tirerack claimed that I could go with a 235 17" tire. My local tire shop said that I shouldn't go wider than a 215 or else I'll get some rubbing on the fenders. I took their advice and had them put on 215 15" tires, and it appears that I have plenty of clearance around the fenders. Without rolling the fenders, has anyone had success putting anything wider than a 215 on their E36? And, does it matter if it's a 15" or 17" rim? I wanted a slightly smoother ride, that's why I stayed with 15" rims. I went with steel wheels so I could change the hubcaps as often as I change my mind about how I want the car to look.

[Cruzin 323is]

i have 225/45/17's on my car.. and still have room.. next set of tires i get.. i'm gunna go 215 in front, and 235 in back!

[Stunnd65]

Is there a performance advantage to staggering them like that, or is it just that it looks cool?

[Cruzin 323is]

in think it looks cool.. i mean most of the newer cars( performance cars have them... u know, the viper, vette, porshe, and many other cars that are rwd have it like that, so i guess it would give better handeling and better traction???

[thekid]

Originally posted by Stunnd65@Feb 14 2005, 09:23 PM
Is there a performance advantage to staggering them like that, or is it just that it looks cool?

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You get maximum grip in back for acceleration (for RWD cars such as ours). Then up front you use narrower tires to give them room to make sure that they do not rub ie. you can run wider in the back than the front. If 225s do not rub in front then I would keep them unless 1/4 or 0-60 times are more important to you than front grip. (Narrower tires in front equals less ressistance for 1/4 mile and 0-60 times but less grip for turning which can lead to understeer). Think that about covers it.

[Rooz]

I currently have 215's all around, next tire chamge, am going with 210 or 215 in front 235 in rear

[mmclaren]

i have 225/17 all round, no rub and they grip nicely

[Eggrolled211]

I have 235 17" infront and 255 17" in the rear...never rubbed at all...its sitting on m3 suspension etc. I didn't lower it.....

[nookatee]

Originally posted by Stunnd65@Feb 14 2005, 10:23 PM
Is there a performance advantage to staggering them like that, or is it just that it looks cool?

[snapback]292052[/snapback]

Actually, the reason to have narrower tires in the front and wider tires in the back on a rear wheel drive car is so that you decrease oversteer/increase understeer. Oversteer and understeer are defined as the difference in slip angle between the front and rear wheels. Slip angle is defined as the angle between the direction the wheels are turned and the direction the wheels are going. If the slip angle on the front tires is greater than the back tires, you have understeer. If the slip angle on the rear wheels is greater than that of the front, you have oversteer. Here's a good website:
http://www.ffcobra.com/FAQ/handling102_part2.html (though there's plenty of information elsewhere on the net).
The moral of the story is that if you widen the rear tires on a RWD vehicle, you decrease the slip angle of the rear wheels, and if you narrow the front tires on a RWD, you increase the slip angle of the front wheels. In this way you have magically reduced the natural oversteer of a rear wheel drive vehicle in an attempt to bring it closer to neutral steer (you guessed it! when the slip angle of the rear and front wheels are the same) Hope that was helpful

[Autotechnica]

Using a lower offset for the front and a higher one for the rear will increase oversteer, doing the opposite will increase understeer.

For a staggered setup, increasing the front tire width and having wider tires in the front over the rear will increase oversteer, doing the opposite, will increase understeer. Generally, nobody uses wider tires in the front and narrower ones in the rear (unless you want to drift). It might give you some very unbalanced and unnatural handling. For performance and speed, you actually want a little undertseer. Too much oversteer, and you'll be scrubbing off too much speed in the corners. You want neutral handling, and since the BMW is 50/50 split weight distribution, it's already quite well balanced without going with a staggered setup. Infact, I find that BMW's tend to understeer a little more than I'd like. That can be corrected with an unnatural addition of some sway bars or stiffer rear suspension.

235-245 should be no problem for a car with stock suspension. For a lowered car, I'd run 225 all around.

Bry

[Stunnd65]

thanks everyone....as always, when in doubt, consult the group

[robbins6103]

I have 225/40/18 ZR all around, no rubbing problems at all.

-Dustin

[nookatee]

Originally posted by Autotechnica@Feb 15 2005, 10:47 AM
Using a lower offset for the front and a higher one for the rear will increase oversteer, doing the opposite will increase understeer.

For a staggered setup, increasing the front tire width and having wider tires in the front over the rear will increase oversteer, doing the opposite, will increase understeer. Generally, nobody uses wider tires in the front and narrower ones in the rear (unless you want to drift). It might give you some very unbalanced and unnatural handling. For performance and speed, you actually want a little undertseer. Too much oversteer, and you'll be scrubbing off too much speed in the corners. You want neutral handling, and since the BMW is 50/50 split weight distribution, it's already quite well balanced without going with a staggered setup. Infact, I find that BMW's tend to understeer a little more than I'd like. That can be corrected with an unnatural addition of some sway bars or stiffer rear suspension.

235-245 should be no problem for a car with stock suspension. For a lowered car, I'd run 225 all around.

Bry

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Hey Bry,
Your conceptually 100% accurate, but your terminology is backwards. It's something I've gotten backwards many times myself. But if you are drifting, that is referred to as oversteer. The terminology comes from the fact that you turn the wheel a little and turn the car a lot (i.e. drift). Understeer is where you turn the wheel a lot, but dont get as much response from the vehicle. Again, you're totally right conceptually, just not in terminology. check out the link. It's actually quite interesting:
http://www.ffcobra.com/FAQ/handling102_part2.html

I dont mean to argue, i'm just a stickler, especially on this one. I'm not right often, so i like to let people know when I am. :P
Peace
And chicken grease