Fuel consumption - Rft vs normal tyres!
 

Hi guys,

I have recently replaced a set of 20' 214 wheels with 09 build bridgestone dueler rft. For some reason, it is more comfortable than my previous 19' 213 wheels with Conti rft.

Anyway I was going to replace the 20" rft to normal tyre like Conti DWS for more comfort ride. but now I don't think it is a must unless normal tyres provide much better fuel consumption and power.

Can I ask what is your experience if you have gone from rft to normal? Better fuel consumption?

I have read that the RFT is slighly heavier due to the stiffness of the wall. If it is, that might lead to a slight difference in MPG. Honestly, when you drive these types of vehicles MPG is the last thing on my mind. I don't think many of us here pay much attention to it.

Just like to see if there is a different in mpg.

Anyway it is my wife's car and I think it is good idea to keep the rft since changing tyre is impossible for her. I did the 4 wheels swap myself in garage and man each wheel should actually for 2 people to lift. I almost broke my back when did the back 315 width wheel.

All tires have different ride and handling characteristics, and two RFTs with different tread patterns and compounds certainly would. The fact that they are RFT or not is not as important as the tread and compound IMO.

RFTs do have a stiffer sidewall, but in modern RFTs that has been tuned to still support the vehicle with no air pressure, while not necessarily being as harsh.

None of the above should have a significant effect on mileage. Tire pressure may have more of an effect, if they were low prior to changing and high after.

I agree that the effect of tires is not really that significant. My initial reaction would be that, in general, the RFTs might provide better MPG due to the stiffer sidewalls, in spite of heavier weight, as a lot of the rolling resistance has to do with sidewall deformation as the tire rotates, hence the reason higher tire pressures give better MPG.

As you note, the tire compound also impacts this, with the softer compounds typically having more rolling resistance.

In those MPG contests to max-out MPG, they generally go with hard compounds and high tire pressures.

But if one is buying a BMW, I would expect getting tires with good grip and handling would outweigh a few percent in MPG, making it a moot point for most BMW drivers. A change in driving style would provide much more MPG benefit to most drivers, as compared to which tire they choose, e.g., anticipating stop light changes, smoother and lighter foot on the throttle, etc.

I have newer generation Bridgestone RFTs (255/50/19) and I was told since they are newer generation they aren't that stiff but boy are they stiff or are they stiff. You can feel a bump even if you pass a 1" patch.

And I do Ultra94, which gets me about 480km per tank with these tires on.

Just to give you an idea how much more the RFTs weigh. *The Michelin
18 inch rft that come on the x5 weigh 13 lbs more per tire over the
non rft Michelin equivalent (source: tirerack.com). 52 lbs of
rotational mass will definitely affect fuel efficiency.

When I went to non rft on my 3er my fuel efficiency went up by ~.5mpg.
I attribute that to the reduction in mass at the corners(total weight loss: ~40lbs).

I myself am keeping the RFT on my x5. *Unfortunately with the 3rd row
there is no room for a spare:(


Sent from my iPhone

+1.

I fully agree that given the price of the vehicle, mileage should not be top of mind for cost reasons.

However, some of us pay a lot of attention to mileage, for reasons other than costs. When I didn't need to pay for fuel (X5 and 535i), it didn't stop me from measuring my fuel consumption and trying to improve it. We bought an X3 to replace the E53 instead of an E70, partly for fuel consumption reasons. Again, fuel cost didn't matter at all, it was the principle.

Some of us calculate our own personal carbon footprints. But at the same time we enjoy BMWs. I don't think there is necessarily a conflict there.

Especially when you calculate it for the sole purpose of laughing diabolically at the tree huggers and polar bears.