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      10-31-2009, 05:17 PM   #1
Codeman
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Square set up? Understeer?

I know a square setup (referring to wheels and tires) is when all the wheels and tires are the same size. I'm wanting to put a square setup on my car, the front wheels would be the same size but the rears wouldn't.

My question is, would having the rear wheels further apart than the front create more understeer? (putting in a massive wheel spacer)



The wheels I found would 'require' me to put in 21mm spacers in the rear to make things look right. (if I go with a square setup)


Original rear wheels: 9 wide; 30 offset
New rear wheels: 8 wide; 38 offset

It's for an M roadster and I want to put M6 replica wheels on.
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      10-31-2009, 06:57 PM   #2
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Quote:
Originally Posted by Codeman View Post
I know a square setup (referring to wheels and tires) is when all the wheels and tires are the same size. I'm wanting to put a square setup on my car, the front wheels would be the same size but the rears wouldn't.

My question is, would having the rear wheels further apart than the front create more understeer? (putting in a massive wheel spacer)



The wheels I found would 'require' me to put in 21mm spacers in the rear to make things look right. (if I go with a square setup)


Original rear wheels: 9 wide; 30 offset
New rear wheels: 8 wide; 38 offset

It's for an M roadster and I want to put M6 replica wheels on.
Ummm this isn't a square setup... that's staggard. M6 reps - not sure how much they weigh, but if you are honestly into performance there are better choices out there. Plus, personally I think M6 wheels look bad on these cars.
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      10-31-2009, 07:33 PM   #3
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I like the look of the M6 wheels, but regardless.

If all of the wheels and tires are the same size and the rears are further apart than the front will that cause more understeer?

I'm open to different types of wheels, it's just those are the only ones I've found that even come close to fitting the M and looking somewhat decent.
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      11-01-2009, 12:05 AM   #4
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Quote:
Originally Posted by Codeman View Post
If all of the wheels and tires are the same size and the rears are further apart than the front will that cause more understeer?
theoretically yes. but this would be like having a staggered setup. why don't you just go with a staggered setup so this way you wont even have to use spacers?
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      11-01-2009, 01:39 AM   #5
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Because I know for sure having more rubber in the back would create more/the same understeer I have now.

I want a car that 'handles' better for autocross. I don't care as much about straight line performance.

Bottom line is I don't want wider tires/wheels in the back.


So with all the wheels/tires the same size, but the back further apart, I may have more understeer?
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      11-01-2009, 02:42 AM   #6
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Why not stiffen up the back if its too understeery for you?
Either trunk brace, thicker rear sway bar or harder springs in the rear. Any one of these would help cancell out understeer/promote oversteer.
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      11-01-2009, 07:42 AM   #7
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Quote:
Originally Posted by Codeman View Post
So with all the wheels/tires the same size, but the back further apart, I may have more understeer?
of course. the wider the rear stance, the more it'll push on a turn and the front will just slide making you understeer.

to be honest though, i have a staggered setup myself and i've never actually had a time where i experienced understeer. even during an autocross event. im sure it's possible depending on the track but im usually dealing with oversteer the majority of the time.
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      11-01-2009, 11:45 AM   #8
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Hmmm, I guess maybe I'm just used to the multiple non-M Z3s I had before and my Sky redline.

Thanks for the help, I'll look for the thickest rear sway bar I can find.


A little OT, but does anyone know off-hand if the rear sway bars are easy to replace like the Z3 or if you have to remove multiple rear suspension components?
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      11-02-2009, 11:12 AM   #9
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I find it odd that you are experiencing understeer as a problem. Almost everyone driving a RWD car staggers the setup to decrease oversteer. You've got lots of power and oversteer would be the bigger problem than understeering through a turn.

If you find it understeering, give it some more gas and powerslide.

You're better off finding proper sized rims for your car then going for something because it "looks good".

Isn't it better to go fast through a turn and look good doing it? Or rather you go through a turn slowly... but "look good"?
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      11-03-2009, 12:44 PM   #10
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8 inch wheels are too skinny for the rear. You can't put a proper size tire on that wheel. Find a different wheel.
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      11-03-2009, 01:32 PM   #11
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Quote:
Originally Posted by silversprint View Post
8 inch wheels are too skinny for the rear. You can't put a proper size tire on that wheel. Find a different wheel.
8 inch wheels in the rear is fine. non-sport packaged z4s come with 17x8 all around with the same size tire.

Quote:
Originally Posted by Codeman View Post
A little OT, but does anyone know off-hand if the rear sway bars are easy to replace like the Z3 or if you have to remove multiple rear suspension components?
swapping the rear sway on the z4 is easier than the z3. on the z4 you only have to remove the wheels, unbolt the endlinks and unbolt the metal tabs and it comes right out. on the z3 you have to remove the wheels, unbolt the endlinks (removing spring makes it easy to get to these) and also drop the rear muffler to get it out. some also remove the rear shocks. it's a big pain.

Last edited by nickpapa; 11-03-2009 at 01:59 PM..
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      11-05-2009, 12:58 PM   #12
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Quote:
Originally Posted by nickpapa View Post
8 inch wheels in the rear is fine. non-sport packaged z4s come with 17x8 all around with the same size tire.



swapping the rear sway on the z4 is easier than the z3. on the z4 you only have to remove the wheels, unbolt the endlinks and unbolt the metal tabs and it comes right out. on the z3 you have to remove the wheels, unbolt the endlinks (removing spring makes it easy to get to these) and also drop the rear muffler to get it out. some also remove the rear shocks. it's a big pain.
Isn't he putting these wheel on a MZ4 as indicated on the first post??

Which means he would have to either squeeze the OEM 255 on a 8 inch wheel or go down to a recommended 245 tire. If this is for cosmetics then why ask about handling.

If concerned about handling then reducing the contact patch to an 8inch wheel will have a significant effect on grip. If running a square setup on the MZ4 then I would recommend at least a 9 inch wheel on all 4 corners with larger tires on the front which is why most people go to a square setup.
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      11-05-2009, 09:12 PM   #13
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Quote:
Originally Posted by silversprint View Post
Isn't he putting these wheel on a MZ4 as indicated on the first post??

Which means he would have to either squeeze the OEM 255 on a 8 inch wheel or go down to a recommended 245 tire. If this is for cosmetics then why ask about handling.

If concerned about handling then reducing the contact patch to an 8inch wheel will have a significant effect on grip. If running a square setup on the MZ4 then I would recommend at least a 9 inch wheel on all 4 corners with larger tires on the front which is why most people go to a square setup.
my mistake, i forgot the fact that he was looking to put on the m6 wheels on a z4m.

i guess what he wants is a lower contact patch for the rear but the same look of a proper width/offset wheel on the rear. i assume the OP is thinking since there will be less rubber, it will reduce understeer rather than having a staggered setup which will look the same but will just have more rubber.

either way, i never really liked the idea of using spacers especially such large spacers so im going to have to agree with silversprint and say find another set of wheels with the width/offset youre looking for.
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      11-05-2009, 11:59 PM   #14
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Guys... Making your rear axle width wider creates less grip on the rear of the car, promoting over-steer.

The wider the stance will typically allow for less traction if that's all that's done to adjust your handling. The cars weight, when shifted, won't help the tires bite into the ground as easy as it would with a narrower width.

These cars push like crazy if you try to hustle it through slow speed turns... and putting more gas into the throttle is the last thing you want to do if you're pushing in a corner. You need to ease off the gas and turn into the push direction to allow the tires to regain traction again.

You guys should read a couple basic race car driving books to learn about that stuff before asking or giving advice on a forum. Anyone that has any true knowledge of driving a car on a track would know this basic stuff. The last thing you want to do is plow your car into a guardrail because BMR4LIFE ( or whoever ) told you to punch the gas while in a push.

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      11-06-2009, 02:29 PM   #15
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Quote:
Originally Posted by bkz4mc View Post
Guys... Making your rear axle width wider creates less grip on the rear of the car, promoting over-steer.

The wider the stance will typically allow for less traction if that's all that's done to adjust your handling. The cars weight, when shifted, won't help the tires bite into the ground as easy as it would with a narrower width.

i dont exactly understand how you are losing grip by making the rear axle wider? i see it as the rear having more grip than the front which in turn causes the front to push and you get understeer. not the best example but take a shopping cart for example, most are wider in the rear and if you are feeling fun at the market and take a turn down the aisle quick, majority of the time it just plows. again, not the best example but

i guess it would all depend on how the weight is transferred which would mean it would depend mostly on driver technique. so this question might be a little subjective to each person's experience.
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      11-09-2009, 11:22 PM   #16
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Quote:
Originally Posted by Codeman View Post
Because I know for sure having more rubber in the back would create more/the same understeer I have now.

I want a car that 'handles' better for autocross
. I don't care as much about straight line performance.

Bottom line is I don't want wider tires/wheels in the back.


So with all the wheels/tires the same size, but the back further apart, I may have more understeer?
Then why would you get M6 reps? Rotational mass is the enemy of almost any kind of sports car.

If autox is your goal then get some lightweight k1s or enkei's and put some good / sticky tires on. M6 reps may be cheap - but there are other pretty cheap wheels out there that are better for your end goal it seems.
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      12-02-2009, 04:22 PM   #17
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the tricky thing from a Z4M is the understeer suddenly going over in oversteer. I really recommend you to invest in a proper suspension and to let this be set up properly. I had a KW clubsport with adjustable camberplates in my Z4M coupe, and the understeer was completely gone, and I was driving 235 front, 265 back. The car was beautifully balanced! I really recommend you not to get narrow tires in the back! You are not solving the problem, just fighting the symptoms.
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