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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Wheels and Tires Forum Sponsored by The Tire Rack > Smoother w/ non-runflat's



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      07-22-2005, 12:19 PM   #1
BMRu4ia
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How much smoother w/ non-runflat's??

Could I assume that if my e90 was equiped with non-RF that if would be a smoother ride?
Or is the difference not that noticeable.

Last edited by BMRu4ia; 07-22-2005 at 12:53 PM.
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      07-22-2005, 04:12 PM   #2
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Quote:
Originally Posted by BMRu4ia
Could I assume that if my e90 was equiped with non-RF that if would be a smoother ride?
Or is the difference not that noticeable.
It's really hard to say. One person said that they didn't notice any adverse effects from going to 19s with non run-flats. Run flats are heavier by up to 10 pounds per tire (from what I have heard) so it stands to reason that less unsprung weight would make for a better ride.

But being that the suspension in the E90 is apparently tuned with run-flats in mind, it's hard to say what a lighter wheel/tire combo would do. I know that the ride on the E90 with run-flats is much better than it is in the Mini and the 5 series with run-flats.

Conventional wisdom is that less unsprung weight will definitely help the ride.
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      07-22-2005, 04:27 PM   #3
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I would believe it would be reasonable to assume that if you have two E90s (one with and one without RFT), the non-RFT shod car would ride better than the RFT car. As far as being noticeable, it would really depend how sensitive you are. The E90 non-sport rides very well, and I don't really sense a sense of harshness when going over sharp bumps and railroad tracks.
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      07-22-2005, 09:24 PM   #4
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Quote:
Originally Posted by CC 330i
Run flats are heavier by up to 10 pounds per tire (from what I have heard) so it stands to reason that less unsprung weight would make for a better ride.
According to Tire Rack's specs on the Bridgestone Pontenza RE050A in a 225/45R17 size, the run flat version is 27 lbs. and the regular version is 24 lbs. That's enough to make a small difference in handling, but I'm guessing the bigger factor is the sidewall stiffness.
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      07-22-2005, 11:56 PM   #5
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Quote:
Originally Posted by BMRu4ia
Could I assume that if my e90 was equiped with non-RF that if would be a smoother ride?
Or is the difference not that noticeable.
I was wondering the same thing today... better ride with out RFT?
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      07-23-2005, 01:04 AM   #6
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I can guranteed one thing...the non-RF tires are a lot cheaper!
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      07-24-2005, 08:42 AM   #7
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Quote:
Originally Posted by CC 330i
It's really hard to say. One person said that they didn't notice any adverse effects from going to 19s with non run-flats. Run flats are heavier by up to 10 pounds per tire (from what I have heard) so it stands to reason that less unsprung weight would make for a better ride.

But being that the suspension in the E90 is apparently tuned with run-flats in mind, it's hard to say what a lighter wheel/tire combo would do. I know that the ride on the E90 with run-flats is much better than it is in the Mini and the 5 series with run-flats.

Conventional wisdom is that less unsprung weight will definitely help the ride.
Holy crap, are they really heavier by up to 10 pounds each?? I'm definitely switching to non-runflats when these stock tires are done. 10 pounds at each corner will make such an awesome difference in handling. I guarantee it.

Also, altho I don't have specific experience with using non-runflats on this car, on paper the non-runflats must ride more comfortablly / less harsh than the runflats because the runflats have a much much stiffer sidewall.
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      07-24-2005, 09:25 AM   #8
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Pondermatic provides the data (thanks!): 27 lbs. runflat vs. 24 lbs regular, i.e., 3 lbs. difference. That is within the range of variation of regular tires. 3 lbs. will not affect ride quality in most circumstances. Unsprung weight is important for handling over rough surfaces, that is, situations in which the wheel assembly is moving up and down. The lighter the wheel assembly, the easier it is to control the movement, it has less momentum. This is especially important for off-road motorcycles, desert racing, rallye cars and the like. It is not as big a deal for luxury cars on the street. I guarantee Cadillacs have more unsprung weight than an E90. It is the sidewall stiffness, as Pondermatic states, that is the relevant variable affecting ride quality, i.e., the extent to which we can 'feel' bumps. If you want a smoother ride, get higher aspect tires (e.g., switch to a 60 series) that are designed for ride quality. The tradoff is that the tire will 'bend' more during sideways loads, hence will not corner as well. I prefer the go-kart feel. When we are down to 30 aspect ratio tires, the difference btw a regular and a non-flat is almost imperceptible. At this point we need to assess which tire performs. Anyone know of any good runflat comparison tests yet?
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      07-24-2005, 02:01 PM   #9
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Run Flat Tires

Can you order Michelin Pilot Sport tires at the same time you order your car ? -- Or is it at crap shoot. ? Plan to order a 330 I.

Thanks,
Donnie
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      07-24-2005, 04:12 PM   #10
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Quote:
Originally Posted by cypwood
Can you order Michelin Pilot Sport tires at the same time you order your car ? -- Or is it at crap shoot. ? Plan to order a 330 I.

Thanks,
Donnie
It's pretty much a crap shoot...My car came with Pirellis and I wanted the Bridgestones...They made a swap for me with another car.
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