One disadvantage is that they wont fit over the brakes on an R56 MCS.

 

MINI > *. I forgot NAM Maxim # 1

And yes, 15's will fit over R56 brakes. Do I need to post a pic to prove it?

 

Not R56 brakes, R56 MCS brakes. Are there some 15" that will fit the MCS brakes? My understanding was that most don't.

 

Yes, there are 15's that will fit the R56...I have JCW brakes on my R53 (same brakes as the R56) and run 15 x 7 Kosei's with Falken Azeni's on the track, no spacers required.

It is a dramatic difference going from 17's to 15's. I'm also running a smaller diameter than stock tire, which also has something to do with it (The gears are shorter, acceleration is quicker), and dropped significant weight off each wheel. I read where an earlier poster couldn't tell the difference between his 18's and lightweight smaller rims, but going from my 17's to 15's is like driving an entirely different car. Maybe its more the diameter difference than the weight, but the difference in the two tire/rim combos is jaw dropping.

 

At the risk of stepping into the middle of a ninnyfest, I suggest you test drive both if you want to get a feel, assuming you are able to drive the test ride under conditions similar to how you anticipate driving your car.

To me, all else being equal, 17's felt a little quicker at turn initiation and 16's felt a little smoother over pavement nonuniformities. The differences were subtle, IMO. E.g. I virtually never initiate turns as quickly as I did during portions of my test drives, and normally I try not to drive over every bump I see. You may feel different things. Heck, I may feel different things after driving my new MINI for a while. But FWIW, those are my impressions.

Now, back to your physics discussion...

 

most don't. some do. I have a set that do indeed work.

I went from 16" R84 with Dunlop runflats (stock) to 15x7 BBS RG-F with Kumho SPT (almost stock OD). No appreciable difference in acceleration, though the ride improved. Handling fell way short of stock (too soft of a tire...steering response was non-existent).

the OD has more to do with acceleration than the weight difference does. My 18" set was shorter than stock while the other sets I compared it to were stock OD. Weight diff = nullified.

 

Ok, makes sense. I am still trying to decide on wether to stay at 15 or not--I'm still not entirely comfortable with the gearing change; I'd like something in between stock and the 15's. I really don't want to go with a wider sidewall because of turn in issues, so I'll probably stay where I'm at or go to 16's. I'm beginning to think 16's may be the best overall for the track, when it comes to tire diameter/gearing change and weight. I could see how 15's would be preferred (with a smaller tire diameter) for autocross though.

 

light wheels are loud

 

Care to explain that please.

I'm not sure how you can extrapolate driver weight from the photo posted. The course may dictate that a sharp turn at that point.

 

he won't explain. he's a hit-and-run insult type of guy. methinks his doc should adjust his meds (again)

 

bad joke...sorry pgt