Robbo

Hi all,

I just read an article in the latest issue of the German magazine Sport Auto; they tested Bridgestone's Potenza RE50A and the Michelin PS2 both RFT and standard tires. The test was made with an E90 but the result should be the same with the E60.
The difference in the wet is remarkable - the brake distance from 100km/h differed some 4m's!! Also the handling in the wet was very poor compared with the non-RFT tire.
I just thought that only the comfort issue was a stake here but this clearly points out the safety argument as an important factor to consider.

Any other thought? I know that there have been a lot of (negative) discussions regarding RFT's but the poor road performance is all new to me!

/R

hawkeye74a

The driving with RFT?s in wet conditions is absolutely terrible. I had on my car the Bridgestone RE50 - RFT tires. Three times on the highway i had nearly lost control of the car at wet conditions and this with nearly new tires. Thanks of DSC, it solved the problem... A few weeks ago i have changed it to Bridgestone RE50A non-RFT. What a difference... we had in the last weeks a lot of rain... so i know what i am talking about. But the comfort issue was also an important issue for the change...

znod

Thanks for the useful info R.

Bimmer32

Any TIS about dealers replacing RF with Regular sport tires yet? I waiting . . . thanks for the info.

On wet pavement, you can easily spin with a touch of the acceleration pedal on a 545i with fairly new RF.

jet190rs

My Dunlop RFTs with 8k miles are very slippery in the corners....much less grip than the Michelin MXM (also w/ 8k miles) on my other car. You can read about my experience during an Autocross session here http://forums.e60.net/index.php?showtopic=26876

UUronL

While I don't wish to dispute the findings or the conclusion, this magazine's findings are in stark contrast to BMW's published findings. BMW claims -better- performance with RFTs - not worse. Some kind of explanation must be presented - otherwise we must assume one set of data is flawed, or from a flawed/ill conceived test. Certainly something was the cause for the variation in wet performance between the tires in this magazine test. I wonder if perhaps different tire pressures are required to offset the effect of the stiffer sidewalls on the RFTs? Did they note the parameters of the test?

When switching from RFT to non-RFT, I wouldn't pick either tire... check out Car and Driver's E90 tire test. They have detailed test data for dry, wet, braking, and autocross.

darkside

Its like a different car with Michelin PS2's compared to the Bridgestone runflats. I couldn't believe how much better the steering feel was and how much more connected to the road I felt after the switch.

525dse

Run Flats are awful compared to your normal summer tires... On the world launch of the E60 BMW, used cars with the most basic wheels and NON-RFT tires, I wonder why?

Robbo

Here are the data:

Handling dry (2770 m track):

B-stone RFT: 1,17,0 min
B-stone Std: 1.19,4 min
PS2 RFT: 1.17,4
PS2 Std: 1.17,8 min

Handling wet (2300 m track)

B-stone RFT: 1.49,3 min
B-stone Std: 1.44,7 min
PS2 RFT: 1.44,2
PS2 Std: 1.42,5 min

Braking dry (100 km/h)

B-stone RFT: 36,7 m
B-stone Std: 37,9 m
PS2 RFT: 36,7 m
PS2 Std: 35,6 m

Braking wet (100 km/h)

B-stone RFT: 52,4 m
B-stone Std: 49,2 m
PS2 RFT: 54,3 m
PS2 Std: 49,8 m


4,5 m differance in the wet between RFT and non RFT!!

As a side note, Sport Auto is a very higly regarded magazine and is a sister to Auto Motor & Sport!
I have no trouble trusting their test data.

/R

BetterMakeWay

I always thought rf tires are junk.