Hi all,

I placed an order this morning with Blackcircles for a pair of new rear tyres for my UK 2003 4.2 XK8 (first time I've needed tyres since obtaining the car). Rim size is 245/50/R17. P-Zeros are what is currently fitted but I could only see them available at circa £250 a corner whereas my alternative option was for Bridgestone Potzenas at a more palatable £160. I then received an email from Blackcircles asking me to confirm if the order was correct as "runflat tyres may not be suitable for the vehicle".

Having done some reading on here my impression is that they will be fine; am I correct in that assumption or is there anything else I need to check as well?

 

I have Bridgestone runflats on mine 255s all round,I love them no problems👌👍 what so ever

 

Threads about tires are similar to oil, coolants, wax and air fresheners. You either love them or hate them.

Will they work on the car, yes of course (assuming you can get the proper sizes).

Would I ever put them on my own car? God no.

 

The main benefit is better control of the car in the event of a blowout, significant at high speed. Another is to be able to continue to drive to a suitable location to have the wheel changed rather than doing the job at the roadside.

Contras are increased cost, weight and rolling resistance and, in the case of 'self supporting sidewalls', the effect of their increased stiffness on the car's handling and ride comfort. Whether they are repairable is also questionable.

This piece by Michelin discusses the subject in a reasonably unbiased manner, IMO, and explains Blackcircle's query:

https://www.michelinman.com/tireEmergencies.html


I wouldn't - I opted for PS4s, mostly based on opinions here - but our wish lists may be different.

 

I believe that run flats are unnecessary for someone who does two things: First, perform proper tire maintenance such as maintain proper air pressure and replace them when they worn or damaged, and second, watch what you're driving over. A good tire with proper inflation on a clean flat road has little chance of blowing out suddenly. If you hit a big piece of metal on the road without slowing down the tire is probably so destroyed that run flat doesn't matter when chunks of it are splattered all over the road.

 

In all my years of owning commercial vehicles and of course passenger cars there is only one (1) reason for a catastrophic tire failure of an undamaged tire with any rated usage outside of extreme tire age. It is overheating of the tire due to under inflation.

This is very easily prevented by purchasing one of those very inexpensive remote tire pressure monitoring systems that either mount on the valve stems or can be installed in wheel. I have the former. What is nice about these systems is that if one picks up a nail and starts to imperceptibly lose air, actions can be taken to fix the tire as opposed to running it flat and ruining the sidewall. These little devices pay for themselves. It is such a good thing that a set is installed on my other cars which already have their own low pressure lights. It is nice to know that something is wrong long before the warning, like an oil pressure gauge. Also, one can see how pressures vary during driving for optimizing any vehicle.

Note that the only other predictable failure which can cause a catastrophic tire failure is a broken belt which relies upon your eyeballs. A run flat will not help anyone here as the tire partially disintegrates. There is a particular model of Goodyear tires, run flats BTW, installed on some very high-end vehicles which are much more prone to belt and sidewall failure. This is due to that fact that Goodyear tires are garbage. The company uses some compounds which do not perform well over time. I am seeing tread separation like one would expect with a truck tire retread on tires installed on Mercedes Benz cars. With MB everyone i know who dumped the run flats for normal tires of the same rating liked the car that much better. The same cars in Europe overall do not run these tires and carry a temporary spare. Perhaps they know something.

The blowout that one wants to avoid at all costs is the rear tire. A front is easier to recover, but a rear can lead to a barrel roll as it causes catastrophic over steer.