wheels-inmotion
Active Member
The evolution
The RFT made a entrance way back in the 80's with the Dunlop Denovo. This was a split-rim wheel filled with gel canisters that would burst and cool the deflated tyre. Needless to say the evolution failed due to cost and I think the public wasn't interested or understood the safety value.
Nevertheless, Dunlop stayed with the evolution and eventually added the Demlock. Again this was a gel filled tyre but this time it was a past rather than canisters. In addition, the wheel was conventional but the tyre had an extra rail in the bead area that locked into the wheel to avoid departure once deflated.
Again this failed and again it was due to cost and demand so only the high-end manufactures added these, classing them as an extra.
For about 20yrs things went quite until Bridgestone developed the RFT without the cooling gel but with an armoured sidewall. BMW initially added the RFT to their build, I think part cost-cutting ( no spare tyre ) and part selling safety.
The Pro's
Safety is without question. No more fitting a spare tyre on the side of the road and there's no such thing as a blow-out on a RFT. These points can't be denied and since they save lives I welcome that.
The con's
The RFT's are way more expensive than a conventional tyre.
The RFT cannot be repaired if punctured. Reason being the manufacture says the sidewall cannot be examined correctly for damage unless it's X-rayed. I've argued this with them because an experienced tech would know if there is damage and what if he/ she did repair the tyre and it failed. The worst thing that could happen is the tyre would have to do exactly as promised and "run-flat".
The RFT has extremely loud harmonics.
The RFT's traction is less than remarkable due to its composition silica content, simply because they struggle to get hot.
The RFT is heavy?... Due to this the wheel is made from a lightweight alloy composite. This is done to reduce unsprung weight. The problem is the first line defence buffer offered by a conventional tyres sidewall isn't there so concussion is transmitted directly to the wheel, and they crack.
So what's the problem?
BMW, who have committed the RFT to their entire models and also apply a chassis geometry to perform perfectly at the cars suggested top-speed. The problem I found was a train of BMW's with tyres worn down to the wire in as little as 4k. At £400 a tyre owners are not happy.
The reason for this is the chassis positions are applied to a tyre that cannot deform and adopt a sports camber position. Solution is simple, dial out some camber but stay within BMW's datum. Will the car handle as well at 160mph? Probably not but what do you want, preservation or performance.
Point to note BMW M series do not fit RFT's and AMG didn't until recently.
Point of this post is because I'm now seeing MB's on RFT's and the whole episode is starting again. MB has adjustability issues unlike the BMW and although things can be made better I wouldn't call it a cure at the rear of the car, but I'm working on it.
I hope this helps.......
The RFT made a entrance way back in the 80's with the Dunlop Denovo. This was a split-rim wheel filled with gel canisters that would burst and cool the deflated tyre. Needless to say the evolution failed due to cost and I think the public wasn't interested or understood the safety value.
Nevertheless, Dunlop stayed with the evolution and eventually added the Demlock. Again this was a gel filled tyre but this time it was a past rather than canisters. In addition, the wheel was conventional but the tyre had an extra rail in the bead area that locked into the wheel to avoid departure once deflated.
Again this failed and again it was due to cost and demand so only the high-end manufactures added these, classing them as an extra.
For about 20yrs things went quite until Bridgestone developed the RFT without the cooling gel but with an armoured sidewall. BMW initially added the RFT to their build, I think part cost-cutting ( no spare tyre ) and part selling safety.
The Pro's
Safety is without question. No more fitting a spare tyre on the side of the road and there's no such thing as a blow-out on a RFT. These points can't be denied and since they save lives I welcome that.
The con's
The RFT's are way more expensive than a conventional tyre.
The RFT cannot be repaired if punctured. Reason being the manufacture says the sidewall cannot be examined correctly for damage unless it's X-rayed. I've argued this with them because an experienced tech would know if there is damage and what if he/ she did repair the tyre and it failed. The worst thing that could happen is the tyre would have to do exactly as promised and "run-flat".
The RFT has extremely loud harmonics.
The RFT's traction is less than remarkable due to its composition silica content, simply because they struggle to get hot.
The RFT is heavy?... Due to this the wheel is made from a lightweight alloy composite. This is done to reduce unsprung weight. The problem is the first line defence buffer offered by a conventional tyres sidewall isn't there so concussion is transmitted directly to the wheel, and they crack.
So what's the problem?
BMW, who have committed the RFT to their entire models and also apply a chassis geometry to perform perfectly at the cars suggested top-speed. The problem I found was a train of BMW's with tyres worn down to the wire in as little as 4k. At £400 a tyre owners are not happy.
The reason for this is the chassis positions are applied to a tyre that cannot deform and adopt a sports camber position. Solution is simple, dial out some camber but stay within BMW's datum. Will the car handle as well at 160mph? Probably not but what do you want, preservation or performance.
Point to note BMW M series do not fit RFT's and AMG didn't until recently.
Point of this post is because I'm now seeing MB's on RFT's and the whole episode is starting again. MB has adjustability issues unlike the BMW and although things can be made better I wouldn't call it a cure at the rear of the car, but I'm working on it.
I hope this helps.......
