Originally Posted by RostokMcSpoons
Actually the Falkens came out at £340 for the four, but I've not seen anyone have a bad word to say about them on any forums I've searched.
BMW won't sanction me changing to normal tyres - they say the car's ABS and sensors are all set for RFT's, also changing from BMW approved tyres may affect insurance and the DVLA as I'm 'modifying' my car
My BMW dealer has Michelin Sport RFT's in stock, they seem to be about the only ones left in the country - a 'bargain' at £578 for the two (cos they won't sanction mismatched tyres on the same axle either, so I've got to swap both, even though the other tyre still has 4mm of tread to go before it's illegal). I've just given them the go-ahead to put them on cos I'm getting very very bored with phoning around
Replacing your RFT's with regular radials is no more modifying your car than replacing the tires when they are worn out. DVLA is interested in modifications that affect the appearance and power, i.e., new paint color (it must match the V5c) or drivetrain (engine size matches the V5c). Insurance shouldn't be affected with different tires either but a new color or modification to the performance that would put it into a higher insurance band certainly would.
I can see BMW's argument against having a mixed set. The sidewall of the RFT is much stiffer than radials and the cornering, ride, and overall handling would be affected, especially if on the same axle. It was the same argument between bias-ply tires and radials. You could, in a pinch, put them together but the handling was affected. You could put bias-ply on the front and radial on the back -- better to have the bias on the back, though.
You also don't want a different size tires on opposite sides of the car. For one, the car won't handle properly. The sensors such as ABS, DTC, and FTM won't work properly. The OBC is expecting certain feedback from the sensors and a mixture it isn't expecting would screw with its mind. Kind of like when you have one plugged ear...you tend to get dizzy because the inner ear on one side is telling the brain something different than the inner ear on the other side. You certainly don't want your OBC getting sick on you.