[trescuarenta]

Hey guys,

I recently changed wheels and tyres on my 340i xDrive. I had 225/255 before. Now i changed to 235/275 tyres, and my 0-100 times dropped from 3,4 average to 3,8 average. My 100-200 time also dropped by about 0,3 secs. No issues or juddering or anything, could my transfer case be limiting power without giving me any notice? Before the car takes off when launching it looks like it waits a bit and then goes..

[Billfitz]

The wider the tire the more rolling resistance it has. That would account in part for the loss of acceleration. If the wider tires are heavier that would explain part of it as well. The higher friction between the tire and roadway with wider tires is only beneficial in turns.

[visionaut]

Like Bill says for tire width/weight, but it’d have to be pretty significant to account for .4 secs 0-100. You’re less than an inch wider.

Are you working from GPS or your speedo for your timing? If you changed your tire diameter your speedo might be off, no?

So maybe a combo of the two effects (width + speedo error).

Also, I hope your new tires have ~equal diameters, since you’re XDrive. If the car senses they’re not, maybe it’s possible that could cause some traction fault/delay (?)

[340iGUY]

235-275 may make oversteer worse.

[Billfitz]

I can't think of any improvement that 235-275 would give, especially with xDrive.

[trescuarenta]

Im using dragy to measure times, previously i was spinning my entire first gear. I also have new wheels which are 1kg lighter each corner, so its not an increase in weight.. Hopefully with the 265 rears things will be back to normal..

[Billfitz]

You shouldn't get spinning with xDrive.

[TheFanatic]

Originally Posted by trescuarenta

Im using dragy to measure times, previously i was spinning my entire first gear. I also have new wheels which are 1kg lighter each corner, so its not an increase in weight.. Hopefully with the 265 rears things will be back to normal..

You probably have other problems if you're spinning through 1st. I run 255 square and have a little spin on initial launch but not enough definitely not through the whole gear. How much power are you putting down?

[trescuarenta]

Car is making 540 hp at the crank, it was good for 3,1-3,2 0-60 mph times.

[TheFanatic]

Originally Posted by trescuarenta

Car is making 540 hp at the crank, it was good for 3,1-3,2 0-60 mph times.

you should be able to get traction with x-drive at that power level. maybe some stickier rubber is in order. You can also adjust the launch control to not put so much power down in 1st in order to get more traction.

[trescuarenta]

Originally Posted by TheFanatic

you should be able to get traction with x-drive at that power level. maybe some stickier rubber is in order. You can also adjust the launch control to not put so much power down in 1st in order to get more traction.

Now with 265 tyres the car is flying again. Even broke my pr and 0-60 in 3.0x

[TheFanatic]

Originally Posted by trescuarenta

Now with 265 tyres the car is flying again. Even broke my pr and 0-60 in 3.0x

265 square or just in the rear? Glad to hear your traction is solved though.

[Wires]

Most likely it's the rotational mass from heavier rubber. Lighter tires allows the axles to spin up faster (less flywheel effect)