[gloryd]

I have a fully loaded 15 x3 35i m-sport with 20inch wheel and performance tires. I got a chance the other day to drive a loaner X-line 35i and feels it has better acceleration and smoother ride when driving in city, not much difference on highway. The loaner car feels very light and has a sensitive throttle, it moves immediately when I tap on the throttle. Whereas I feel my own car is heavier and not as smooth as the x-line.

I've been trying to figure out the cause and wondering if anyone here has any input.

So far, I'm hesitating the wider tire and bigger wheels on my car contributes to this issue.

[bichoo]

Originally Posted by gloryd

I have a fully loaded 15 x3 35i m-sport with 21inch wheel and performance tires. I got a chance the other day to drive a loaner X-line 35i and feels it has better acceleration and smoother ride when driving in city, not much difference on highway. The loaner car feels very light and has a sensitive throttle, it moves immediately when I tap on the throttle. Whereas I feel my own car is heavier and not as smooth as the x-line.

I've been trying to figure out the cause and wondering if anyone here has any input.

So far, I'm hesitating the wider tire and bigger wheels on my car contributes to this issue.

Those wheels are 21inch and yes, there could be a difference between wheels with respect to acceleration. I notice it when I go from my 20s to my 18 winter tires. I'm not sure what you mean by "smoother"

[MichiganMike]

You may find the Car and Driver article at the link comparing effects of upsized wheels and tires on a VW Golf to be informative.

http://www.caranddriver.com/features...d-tires-tested

"What’s immediately apparent from the results is that as the wheel-and-tire packages get larger and heavier, acceleration and fuel economy suffer. Neither is a huge surprise, but we measured a 10-percent drop in fuel economy and a four-percent degradation in 0-to-60-mph acceleration from the 15s to the 19s, which is worth considering should you be thinking about “going big.” "

[Tjalle]

The wheels look like my 20" 310M:s.

My car is a bit slow in Comfort, but responsive in Sport. I believe this is more a calibration issue, than "big wheels". I can feel no difference with my 18" winterwheels.

We are talking 300+bhp and 400Nm of torque.

[gloryd]

Originally Posted by Tjalle

The wheels look like my 20" 310M:s.

My car is a bit slow in Comfort, but responsive in Sport. I believe this is more a calibration issue, than "big wheels". I can feel no difference with my 18" winterwheels.

We are talking 300+bhp and 400Nm of torque.

Originally Posted by gloryd

I have a fully loaded 15 x3 35i m-sport with 21inch wheel and performance tires. I got a chance the other day to drive a loaner X-line 35i and feels it has better acceleration and smoother ride when driving in city, not much difference on highway. The loaner car feels very light and has a sensitive throttle, it moves immediately when I tap on the throttle. Whereas I feel my own car is heavier and not as smooth as the x-line.

I've been trying to figure out the cause and wondering if anyone here has any input.

So far, I'm hesitating the wider tire and bigger wheels on my car contributes to this issue.

Originally Posted by Tjalle

The wheels look like my 20" 310M:s.

My car is a bit slow in Comfort, but responsive in Sport. I believe this is more a calibration issue, than "big wheels". I can feel no difference with my 18" winterwheels.

We are talking 300+bhp and 400Nm of torque.

My bad, it's 20 inch 310M. I think you might be right about the calibration, as I also didn't tell much difference with my 18 inch winter wheels. I recently increased my tire pressure from 32/35 to 35/38, and that made it a little bit better, but still not as fast as x-line or even 28i when in comfort mode. Was thinking bring it to a tuner shop to improve the responsiveness but then got told that can void my warranty.

Good to know I am not the only one feels the slowness.

[gloryd]

Originally Posted by bichoo

Those wheels are 21inch and yes, there could be a difference between wheels with respect to acceleration. I notice it when I go from my 20s to my 18 winter tires. I'm not sure what you mean by "smoother"

Originally Posted by gloryd

I have a fully loaded 15 x3 35i m-sport with 21inch wheel and performance tires. I got a chance the other day to drive a loaner X-line 35i and feels it has better acceleration and smoother ride when driving in city, not much difference on highway. The loaner car feels very light and has a sensitive throttle, it moves immediately when I tap on the throttle. Whereas I feel my own car is heavier and not as smooth as the x-line.

I've been trying to figure out the cause and wondering if anyone here has any input.

So far, I'm hesitating the wider tire and bigger wheels on my car contributes to this issue.

Originally Posted by Tjalle

The wheels look like my 20" 310M:s.

My car is a bit slow in Comfort, but responsive in Sport. I believe this is more a calibration issue, than "big wheels". I can feel no difference with my 18" winterwheels.

We are talking 300+bhp and 400Nm of torque.

Originally Posted by bichoo

Those wheels are 21inch and yes, there could be a difference between wheels with respect to acceleration. I notice it when I go from my 20s to my 18 winter tires. I'm not sure what you mean by "smoother"

I meant the gear changing and throttle lagging is almost not noticeable on the x-line 35i

[exon]

Originally Posted by gloryd

I meant the gear changing and throttle lagging is almost not noticeable on the x-line 35i

It is probably a calibration thing more than anything else. I have a 35i and throttle and transmission lag is pretty annoying at times. Tuning helps, so if you plan to keep the car for a while better do it now. Also there is a throttle reset process for BMW which might help.

[gloryd]

Originally Posted by exon

It is probably a calibration thing more than anything else. I have a 35i and throttle and transmission lag is pretty annoying at times. Tuning helps, so if you plan to keep the car for a while better do it now. Also there is a throttle reset process for BMW which might help.

Originally Posted by exon

It is probably a calibration thing more than anything else. I have a 35i and throttle and transmission lag is pretty annoying at times. Tuning helps, so if you plan to keep the car for a while better do it now. Also there is a throttle reset process for BMW which might help.

Thanks for the advice, buddy. Totally agreed, the lagging is annoying when driving in urban areas. Have you done the tuning on your 35i? If so, do you mind letting me know what type of tuning service is needed? I wonder if dealer will do such things so that it doesn't void my warranty.

[exon]

Originally Posted by gloryd

Thanks for the advice, buddy. Totally agreed, the lagging is annoying when driving in urban areas. Have you done the tuning on your 35i? If so, do you mind letting me know what type of tuning service is needed? I wonder if dealer will do such things so that it doesn't void my warranty.

yup, it is worst in city traffic and frequent stop & go traffic. i.e. when the throttle application is light (<50%) but also varies quickly due to traffic situation (say you let off the gas pedal to let someone in then step on it again to accelerate).

I tried a piggy back style tuning chip (burger tuing N55 stage 1). It makes the engine response sharper & stronger under partial throttle, but does not help the transmission shifting. In the end it does make the car feel less "lazy" and the additional torque reduce the need for some downshifts (which reduces transmission lag).

So I think it is a worthy purchase considering it is quite cheap (<$400). But is it a great fix? probably not. It alleviates the problem by maybe 30% or 40% (if that can be quantified). I would assume most piggy back style chip would give similar results.

I guess maybe a ECU tune that affects both the engine and transmission would bring the car to a more acceptable state, but I have zero experience with those...

[alpwhite46]

Does sport or comfort mode make any difference?
If you push the throttle to the floor in comfort mode, it detects what you are trying to do and it should feel no different than if the car was in sport.

?

[Peter_R]

Originally Posted by alpwhite46

Does sport or comfort mode make any difference?
If you push the throttle to the floor in comfort mode, it detects what you are trying to do and it should feel no different than if the car was in sport.
?

Yes. There is a slight lag when you initially do it because in Comfort Mode the RPM is slightly lower. If you are already in Sport Mode then the engine RPM is already higher, so you get a quicker response when flooring the throttle. With the 3 litre diesel it is barely noticeable because of all the torque you have available to you.