Front fenders question

[djafactor]

I've always wondered why the front wheels of our cars are not centered in the fender well. It seems like maybe a design error when they were forming the front bumper and fenders. The wheels seem to look pushed more towards the back making them off center. I don't know if this has been discussed before. My buddy and I came back from a sunday blast and were having a couple of beers looking at the car and started talking about this. Is there a specific reason why it's like this? Below is a pic I snagged from another thread to illustrate what i'm talking about.

cheers

Amit

[e30m3man]

I noticed that with my car as well. I just fitted some style 5's and the tires were rubbing on the inside. It really seems noticeable with larger wheels.

[Jim]

A friend of mine who lives in Europe has exactly the same as me and we noticed when the cars were set side by side his wheels are located very slightly different that mine...but that could be because the Cabrios were all built by hand.
Cheers,
Jim

[t13vom]

Your ears must have been burning... I was thinking about this samething in relation to the offset control arm bushings which are installed on my car. I have not looked under my car but I was begining to think they might be installed 180 degrees out. I would be very interested in this discussion.

Cheers!

[chutrain]

About all the M3's I have seen have this issue. I've looked past the visual awkwardness, and never questioned it. I thought it might have been the control arms, but never found out the reason. Will be interesting to see what others might say.

[djafactor]

I figured this would be a good discussion. Maybe there is a solution too? Being a designer myself, this really bugs me and I just can't see why they would have done this unless it has something to do with aerodynamics/lift/etc. I'll talk to my BMW guru this week and get his thoughts as well.

cheers

Amit

[Bruce]

A friend of mine (Nikos on here) chased this issue for a long time....turns out it was a bent control arm.

[.cj.]

It's the diffrence between the standard e30 strut vs. the e30 m3 strut. The
e30 m3 has different SAI than the standard e30. Also the caster is greater on th e30 m3 strut.

Also compare the regular e30 fender opening to the m3 and youll see that the rear part of the opening on the m3 is more vertical.


Cris

[blyguy]

The offset control arm bushings are the reason for the slightly rearward set of the front wheels. On early M3's (prior to 6/89) the control arm bushing was centered and so was the front wheel centerline.

For 1989 and later cars, an offset control arm bushing was used to increase caster, and more importantly allow for more clearance for wider wheel/tires at full lock (ie 225/45 16s). It was not a design mistake.

By now, most cars have been upgraded to the offset control arm bushings. You could use the centered bushing if you wanted, but it would be a step backwards and you wouldn't be able to run wider tires without rubbing the front fender liner.

A bent control arm can also set your wheel back some, but for a whole 'nother reason, brother :hogan:

cheers,
Bryant

[Reelizmpro]

The offset control arm bushings are the reason for the slightly rearward set of the front wheels. On early M3's (prior to 6/89) the control arm bushing was centered and so was the front wheel centerline.

The offset bushings actually move the wheels slightly forward a bit. The old centered bushings on my 88 made the problem worse.

[Nikos]

Use the offset contral arm bushing and get some 96+ E36 M3 control arms. Your wheel will sit nice and centered at that point.

Of course, then you may have some slight rubbing on the front of the wheel opening with the wheel turned, but a dremel tool with a cutoff wheel works wonders


Nick

PS
Oh, and my control arm was not bent that much...going to 96+ arms from the aluminum ones helped, but my passenger side is still slightly further back than the driver's side. Go figure.

[M3probe]

I'm glad that someone mention this because just yesterday I changed to the offset bushings and notice this as well. After furture review of the design, the flaw is with the wishbone bracket. The section that bolts to the frame where the two mounting bolts is'nt long enough.

[djafactor]

thanks for the explanation. When you say increase caster does this mean that the upper ball joint is further forward than the lower ball joint? If so what benefit is this besides the extra room for wider tires?

So I guess the best way to cure this is the 96+ e36 control arms? Is there big difference in weight/design? Does it upset and handling characteristics?

cheers

Amit

[blyguy]

The offset control arm bushings are the reason for the slightly rearward set of the front wheels. On early M3's (prior to 6/89) the control arm bushing was centered and so was the front wheel centerline.

I stand very much corrected - the offset CA bushings will move the front wheels forward. This will increase caster (the top of steering axis of the front wheels tilts more towards the rear of the car when viewed from the side)

Increased caster increases the amount of negative camber (inward tilt of the wheels when viewed from the front of the car) you gain as you steer. The end result being increased steering effort and front end grip.

Disclaimer: I'm no expert, but we're all here to learn right? :chug:

cheers,
Bryant

[Mario L.]

It was designed this way . . . .

a combination of caster camber and steering geometry for tire clearance

ever notice that when you turn the wheel all the way in one direction, let's say to the right, that the rear of the right wheel easily clears the rear of the fender opening, and the wheel is angled to a positive camber position while on the opposite side of the car the wheel is barely clearing the back of the bumper and front under trays and has a negative camber position.

Because the wheel/tire do not steer on the same axis as the strut center line, the front outer edge of the tire rotates on a larger radius than the rear outer edge, consequently requiring greater body opening for clearance.

This is from the spindle placement in relationship to the lower ball joint and the upper strut bearing . . . complex, and I'm sure that an automotive engineer with a "Steering Degree" will give us the proper terms . . .

Note that a stock E30 does not do this as much. The steering geometry of the M3 is effected by the turning plates at the bottom of the strut, which are not on a non ///M E30.

It's all part of what makes this car so much fun to drive!

Enjoy!
Mario L.