[KiwiRD]

Hi all. I have a wheel related question: It has been discussed before, but has anyone switched from 18" to 19" wheels, and felt any real, perceptible level of performance, acceleration, or braking degradation afterwards as a result of additional weight? I am not concerned with changes in ride quality. I just want to hear people's thoughts on the weight factor.

I have a set of 19x10" and 19x9" M359 replicas and am about to replace my M193s with them. Some argue the point about the moment of inertia, and the additional weight not just of the wheel itself, but that it being further to the outer edge of the wheel, multiplying its negative effects. What are people's thoughts on this? In the US forums there is a tendency to exaggerate, and claim that minimal weight gain per corner = maximum performance loss!

[Fundguy1]

Figure every 10 pounds of wheel/tire weight increase is minus 1/10 a second in the quarter mile or equivalent to 100 lbs of car weight. Then calculate the weight difference between the wheel/tire combo you're changing to and you'll have your answer. Don't forget to add the difference of all 4 wheels. Adding 5 pounds per wheel is a 20 pound change.

[KiwiRD]

Originally Posted by Fundguy1

Figure every 10 pounds of wheel/tire weight increase is minus 1/10 a second in the quarter mile or equivalent to 100 lbs of car weight. Then calculate the weight difference between the wheel/tire combo you're changing to and you'll have your answer. Don't forget to add the difference of all 4 wheels. Adding 5 pounds per wheel is a 20 pound change.

I think the increase is around 2kg / 4.4lb per corner. On that basis, it doesn't seem to be much of an issue?

[John320d]

Wider tyres will decrease your mpg.

[KiwiRD]

Originally Posted by John320d

Wider tyres will decrease your mpg.

Not really too worried about losing 1 or 2 mpg. I only drive the car about 4,000 miles a year. I'm most interested in whether people can 'feel' any difference in performance. Does the car feel heavier and less responsive, etc.

[Fundguy1]

You wouldn't know unless you timed it at the track. You're going to be 1% slower.

[RajB]

The extra weight is fairly negligible in the grand scheme of things and normal driving but unsprung weight is noticeable in terms of acceleration and steering feel (mostly on track). You may notice the extra weight on turn in etc but I think you won't really notice it overall.

[KiwiRD]

Originally Posted by RajB

The extra weight is fairly negligible in the grand scheme of things and normal driving but unsprung weight is noticeable in terms of acceleration and steering feel (mostly on track). You may notice the extra weight on turn in etc but I think you won't really notice it overall.

I think you're right. The standard 18" rims and run flats probably weigh more than 19" rims and regular tyres anyway. I was also thinking how many small low powered cars are now being offered with 17" and 18" wheels from the factory. I'm talking about 1.6 and 2 litre normally aspirated engined cars. Now, if those little things re being fitted with 18" wheels and wide tyres relative to the size of the car, then upsizing one inch on a 335i with plenty of power and torque shouldn't make much difference at all. I'm not sure anyone could really feel and few tenths difference.