Quote:
Originally Posted by Bigtop
I have read all the threads here, but non of them give specific evidence that BMW designed the X5 E70 to run on only runflat tires and that if you put non runflat tires on it will be detrimental to the suspension and handling characteristics of the car.
Has anyone got any evidence of this and I mean from high up in BMW, not just the salesperson of the month or the local mechanic?
|
We are getting into very small differences, but here is my take:
I believe that the E70 is designed for a run-flat tires. That does not mean you can not change to non-run flats, go right ahead. Take out the word "only" in your quote, above. What it means is that the suspension has been tuned to accomodate the additional harshness of the stiffer sidewall. Noise/Vibration/Harshness (NVH) tuning is all about resonant frequencies, and what the vehicle operator feels in the seat. Early adopters of RFT (like my 2004 Z4) had a very harsh ride. Switching to non-RFT on that model made a huge difference. By 2008, BMW had tuned the suspensions to reduce the apparent harshness. There is a significant difference (in the same model series) over several years of refinement. You will still likely get a more compliant ride with non-RFT, but there is far less reason to get upset about RFTs now than there was in 2004. If you want to switch, you just need to consider the cost of new tires (on the same rims), the need for a spare, and possible refusal of service by BMW assist for towing you free of charge with a flat tire.
My source is engineering articles read over the past five years, not a sales rep.
__________________
2007 X3 3.0si, 6 MT, Premium, White
Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue
|