Rear tire size installation question.

[zmuff]

It's time to buy two rear tires for my 535i, the fronts are still in great shape(hmmm, wonder how that happened?), and I'm considering going to a bit larger size. Right now there are 245/45/17's on the back. Do you think I could squeeze some 255 or 265/40/17's back there, or will I have a clearance problem with the fender lip because the car sits so low? Thanks to all.
http://www.bmwe34.net/asp/upload/869.JPG

[simon-york]

Hi there!

I have a set of Alpinas on my car, mine are the staggered size set-up with the fronts 8.5" and the rears 9.5". The front tyres are 245/35/17 and the rears are 255/45/17. The car is lowered on Eibach springs, but there is still plenty of clearance. I understand from Bruno's site that the rear tyres ought to be 40 aspect, so it is probably best to stick with his figures to keep the speedometer accurate.

Hope this helps you.

Simon Daubeney, York, England
1989 530i SE E30 engine 5spd 152,000 miles

[DueyT]

Zmuff, 255/40-ZR17 is a sure thing (see the Black Beast below as proof*). 265's may need rolling of the inner rear fender...

Cheers,
Duey

[scott540]

Zmuff, I've got 255/40 17 on and they fit fine. They look tight in there but when you look close there's plenty o room.

[l8apex]

One big reason that BMW and other marques put larger tires on the rear of their cars is safety. The setup using rear tires wider than front tires tends to induce understeer. This is considered to be safer on a mass market vehicle because, as you add speed and greater steering input the car tends to "plow" the front end as you reach dangerous velocities. Thus it is more "stable" and harder to get into trouble with (spin). The alternative would be excessive "looseness" as the rear tires lose traction and the rear of the car spins to the side.
In the performance world, a balanced or slightly "loose" or oversteering car is preferred as it is more responsive to steering input, albeit somewhat more easy to develop a spin. Don't think that the wider rear tires are there in order to "put more power down on the road". Our cars have good power, but not enough that wider tires will make any difference in that department.
If you want to go to larger tires for appearance, well and good, just don't do it for better handling.

Dave
1994 540i-my track baby-245/45-17 Victoracers all around
180,000 miles on original Nikasil block
1996 328iS-daily driver
1998 318ti-our spare car-very tossable on the track-great fun

[Scott E]

One big reason that BMW and other marques put larger tires on the rear of their cars is safety. The setup using rear tires wider than front tires tends to induce understeer. This is considered to be safer on a mass market vehicle because, as you add speed and greater steering input the car tends to "plow" the front end as you reach dangerous velocities. Thus it is more "stable" and harder to get into trouble with (spin). The alternative would be excessive "looseness" as the rear tires lose traction and the rear of the car spins to the side.
In the performance world, a balanced or slightly "loose" or oversteering car is preferred as it is more responsive to steering input, albeit somewhat more easy to develop a spin. Don't think that the wider rear tires are there in order to "put more power down on the road". Our cars have good power, but not enough that wider tires will make any difference in that department.
If you want to go to larger tires for appearance, well and good, just don't do it for better handling.

Dave
1994 540i-my track baby-245/45-17 Victoracers all around
180,000 miles on original Nikasil block
1996 328iS-daily driver
1998 318ti-our spare car-very tossable on the track-great fun

[zmuff]

Thanks all! Looks like I'll be putting on some fatter meats.