Super tire fitment

[jalopi]

Sup bros,

So I've been thinking for a while now about getting a set of 17x10" wheels, think I'm finally going to pull the trigger on some custom jobbies. They need to be 17's for the 330i brakes I want to use and I'd like them to be 10" wide so I can fit anything from 235's for drifting/street use to 275's for serious track action without having to change sets of wheels. I put down about 300 wheel torque around 2k rpms, so yes, I do need that much tire.

I'd like to keep the wheel fitment square, but in order to do that I'd have to run a really, really low offset due to the steering angle kit I have (60* or so of angle)... to keep the potential wheel from hitting the control arm I'd have to rock a -38 offset wheel.

Just came back in from taking some measurements on the car and it looks like I'd need to extend the fenders by 95mm to make this work.

Right now I've got e46 control arms, centered CABs and 205/45's on a 16x8 wheel. When I get pretty close to full lock right now the tire starts rubbing on the inner fender well / body, so I've got concerns about extending this bit out by about 60mm.

Basically, my question is this: can I use offset CABs to max out the caster and not worry about hitting the fender well / body at full lock? I realize I'm going to have to widebody it or something to stop the tires from hitting the fenders. Help is greatly appreciated; I really don't feel like spending $60 on one of those tire/wheel 'calculator' tools.

[Madhatter]

Added caster on mine put the wheels REALLY close to hitting the fender and the inner guard at the very front below the headlights, not so much the very inner side near the chassis rails. Only really need a few mm of clearance to be honest. You can roughly measure it to get the space you want, but the problem is not all tyres are of equal width. So some 275's will actually be 275mm wide, while others might only be 260mm or so.

If you are getting this tight with specs, really just going to end up having to pick a wheel and tyre combo, then see how it fits. Can play around with thin spacers to see just how much you need to alter the offset by, but keep note of the wheel backspace too as this is just as (if not more) important if you are rubbing on the very inside of the wheel well. I don't think you'll need to space it out anywhere near what you think you will, just pay attention to tyre dimensions. Anything oversized compared to stock profile is going to reduce your clearance. For example, 255/40R17 is much taller, but if you drop down to a 255/35R17 you end up almost identical radius to the original 195/65's.

I reckon the biggest problem you are going to have is to find a wide tyre in a friendly dimension. Do you really want/need to run wider than 235's on the front? 235/40R17 is a pretty big tyre without going massively oversized. Clears everything inside on a 9" wide, ET20 wheel with 15mm spacers, but the outer guard lip is a problem so have some wide flares from KA motors to go on which should do the trick. Not sure I really like my chances running something like a 255 up front. Might swap the rears to the fronts one day and see how much space there really is, but the 255/40's are certainly too big.

A host of problems spacing a wheel out that far from the stub axle, id probably be wary of even considering it if you do a lot of street miles. Otherwise id be looking at reinforcing your strut tubes at a minimum and expect having to replace the front wheel bearings at regular intervals. Lots of leverage developed that far out and I reckon you might start to notice any bumpsteer issues you have if you have really lowered the suspension without any regard for the control arm angle.

To be honest. If a customer came to me with this question about running such wide wheel/tyre combos properly, id start by looking at replacing the control arms and moving the whole stub axle further out. Depending on how far out you really want to go, as an extreme example mounting points for the strut at the top might need to be altered, so the strut tower would end up needing to be boxed and altered. Might end up having to run tubular arms or converting to some sort of link setup you'll see in motorsport use a lot (i think AKG offers similar), but then you are really starting to get into the realm of the car being dedicated track use because the parts wont take the abuse of running daily on the street. You'll pretty much just destroy the spherical bearings or end up bending a rod or arm (happens on the track too) if you spend a lot of time on the street.

I know the AKG kits provide a track increase of up to an inch by spacing the stub axle further out. They even have extensions for the tie rods to help with the bump steer, but how much cash do you want to put into the car? none of the tubular or link motorsport conversions are cheap.

[jalopi]

The biggest issue is the wheels hitting the control arms at full lock. I essentially need an extra 10ish mm of suspension clearance over what my current wheels provide.

[Madhatter]

So now you are hitting the control arm at full lock? you said you were rubbing on the body before. The control arm has a slight taper to it I guess, but where are you rubbing on it because it only has a slight taper down towards the outer ball joint. Tubular arms and the like aren't going to help either because they are usually cross braced in one form or another and will be worse. I honestly don't see an easy solution as the control arm is pretty thin. Depending on where it was rubbing, may be able to reduce the toe out on turns a little with alignment settings.

Personally, id sacrifice 5 degrees of steering angle, fit steering stops to make sure they never hit the control arm and work out the rest with a small spacer to clear sheet metal.