I'm attempting to figure out if a +48 offset on 17x8 is too high for a MCS with slight lowering. Right now its sitting at stock height, but I plan to mildly lower it with springs soon.

I get mixed signals reading threads on offset, for the MCS do you want it high (48ish) or low (38ish) in the rear to prevent rubbing? I don't mind cutting the inner fender or hammering, but I don't want to damage the exterior of my painted arches or hit suspension components on the inside.

 

It's not the inner wells you have to worry about. It's the rear trailing arm and front struts that will make contact here. Again, clearence will depend on a few things such as tire selection, suspension alignment, and the fact that every Mini seems to be a bit different.
What tires do you plan to use?

 

Hadn't thought about tire sizing too much but the 215/45YR17 BFGoodrich g-Force T/A KDW 2 looks pretty nice

 

That would be a do-able size on 8" rims for this aplication. The tires would be slightly stretched which is good. They shouldn't be much, if any wider then the rims.
If you have to go with these wheels then I would think that you will need some spacers. Maybe 5mm front and 3mm rear. You still may need some plastic well trimming on the outer part and maybe some arch flange trimming. The pic in my sig is my car with a good amount of ender work to fit my tires. One would never know by just looking at it, so don't be too affraid to hit some metal with a hammer...

 

Aside from pure fitment, offset changes almost all goemetrys. One of the most important is the tracking character of the tires as they move thru suspension travel. At very low numeric offsets the tracking pattern will become very wavy. This is not a big deal on glass smooth roads, but can become downright nasty on B type roads.

In theory, and this is a best guess without having checked, 38mm and 48 probably determine the two extremes. 48mm places the steering torques father from the center of the tire - more negative scrub. This, in theory, should reduce steering feel. But so many other factors come into play too.

 

I need to talk with you about this meb. I'm doing some changes that are a bit extreem. Could use your advise
Give ma a call...

 

I've experienced this before on my other car going from stock 17x7 +55 215/50/17 to 18x7.5 +42 225/40/18, added a great deal of over-sensitivity. I'm using 17x8 +45 235/40/17 now and its a better balance between the wider footprint and steering feel.

My MINI has 16x7.5 +43 215/50/16's on right now and the feel is good, and I checked w/ a wheel calculator and the 17x8 +48 215/45/17 is .3in farther in, but almost 0 farther out, so I think feel should stay similar except for the wider tire

 

I responded to your PM. I'll call you tomorrow.

I need to learn how to get sketches in this thing. As jlm wrote, a picture is worth a thousand words.

In essence, changing wheel offset changes spindle. And spindle is exactly what it sounds like; the length of the axle spindle. However, the length of the spindle is determined by the point between where the King pin axis or SAI (the same thing) intersects the axle center line and the tire's center line. now what this actual does at the tire's contact patch is not entirely understood by engineers today because of the complexity and time, and therefore cost of testing. What is known is that as spindle length is increased, changes in actual track length as the suspension moves thru bump and rebound become more dramatic. This is responsible for a wavy track pattern.

It has been written that powerful front wheel drive cars should strive for a wheel offset closer to center point steering. The theory is that too much negative offset will super load the outside tire causing some very uneven torque at the steering - fighting the steering wheel.

Center point steering can be extremely vague and unstable in a straight because the scrubing forces are equal left and right of the tire's center line.


EDIT: I had to go dig something up because I felt something was missing. The wavy track pattern is really determined by the location of the instant centers - whcih determine roll centers. The length of the control arm fits into this calculation too because it affects the length of the radius about which the wheel moves, hence scrub radius. Now, adding more negative offset - lower numeric numbers - pushes the wheel's centerline out farther exaserbating this effect - it adds to more positive spindle. More positive spindle - and I wrote this somehwere else a week or so ago - makes the wheel travel farther up over bumps and into depressions causing very funny torques at the steering wheel because of the accelerated longitudinal forces acting on the wheels center...if one wheel goes over a bump and the other does not while the car is traveling at a steady speed, the wheel that went over the bump must travel faster than the one on smooth roads. Otherwise it would skid in the extreme. But it is this lag and acceleration at the wheel's center - longitudinal forces - that casue steering kick and weirdness. Adding more negative camber also increases spindle length because it moves the SAI inbound of the wheels' centerline. So lots of negative camber and low numeric wheel offsets (?) increase spindle length. The wavy track pattern is indeed scrub.

Ideally, the camber value desired should be selected and then wheel offset. In reality, only an accurate drawing of the Mini's front end will help determine the actual offset/camber. I've got work to do!

 

I'll throw in my .02 worth as well. I"ve done lots of measurements and calculations for 16x8 and 15x7.5 wheels.

I see no reason the 215/45/17 would be a problem on the rear with +48, in fact that's exactly the offset I'd get for a 17 in the rear.

For the front, you would need spacers just to get the WHEEL to clear the strut. I'd say 6mm minimum. Tire height could be a problem in front but I'm long past a stock suspension but it's possible you could have a problem with tire to spring perch clearance even with a 6mm spacer and spacing out farther could cause fender problems. If I was hell bent on some 17x8, +48's, I get some 215/40/17's.

If you check my posts here and MINI2, same user name, and search my wheel sizes you may get a little more insight.

 

i would get it and get a spacer if it rubs the inside.

 

Make sure you understand what happens when you install spacers on one axle and not the other...unless I mis-read your post.