Runflat tyres.

[Dan7357]

I want to keep to the same make and tread on my car, but the only front tyres I can get are runflats ?? (no stock for weeks of non runflat)
What's a runflat ?

Is there a problem having a set of runflats on the front and non runflats on the rear ? Same tread/make ect..

Thanks

[HellDiver]

A run flat tyre is one that you can drive on when it's flat.

There's no difference other than stiffer sidewalls, so you can use them OK on standard rims. Expect a lumpy ride, though.

[Gwagon111]

They're not known as " run like st " tyres for nothing . The tyre walls are three times thicker than a normal tyre, which allows you to drive on them if they go flat. The pay off is that the tyre walls don't flex like a normal tyre. This leads to a rubbish ride. You should also fit pressure sensors if you use run flats, which are expensive and notoriously rubbish.

[Dan7357]

Should be good on a track car, hard sidewalls ! lol

[Big E 118]

My current car has runflats, never again.

Expect a very "crashy" ride and you will spend every drive swerving around even the smallest holes in the road!

[Funk]

Just to provide a counter-point; I have RFTs on my car and have no complaints about them at all.

[GSP]

+1 I have 245/35 18" on my car and they are fine, the Msport suspension is bumpy but the tyres are fine.

I wouldn't want them if I didn't have the sensors though as I have been in cars with 'flat' run flats and you can't tell.

[Cost Captain]

if you're car wasn't specifically designed with run flat tyres in mind, dn't fit them.

i assume the reason you want the same make and tread pattern is so that the tyres grip/drive the same, and if you fit 2 standard tyres and 2 run flat tyres, they won't drive the same. surely a different supplier will be able to get the tyres? what size/brand/tread you looking for?

[530dTPhil]

HellDiver said:

.........so you can use them OK on standard rims.

I think that you are 100% wrong there. You can fit non RF tyres to RF rims but not the other way around. I believe that there is a special retaining ridge on the RF rims to ensure that the tyre stays in place when running flat.

Edited by 530dTPhil on Tuesday 23 November 12:41

[V8s ONLY]

Runflat tyres,if marked as exactly the same size as non runflats,ie 205/55r16 or 255/55r18 etc.fit onto normal wheels,there is absolutely no difference.However putting runflat tyres onto a car not originally fitted whith them creates a few problems.The car must be fitted with a pressure monitoring system to let you know when one has lost pressure,as you would just run it to destruction.The suspension is tuned to the different handling characteristics of runflats.THE BIG NO NO IS FITTING RUNFLATS ON THE FRONT ONLY,this will make the car an oversteering drift machine like you wouldn't believe.Runflats that require special wheels have different size markings to prevent fitting to the wrong wheel ie 220/65r390 (old Jag XJ40 size)non runflat equivalent was 225/65r15.

[HellDiver]

530dTPhil said:

HellDiver said:

.........so you can use them OK on standard rims.

I think that you are 100% wrong there. You can fit non RF tyres to RF rims but not the other way around. I believe that there is a special retaining ridge on the RF rims to ensure that the tyre stays in place when running flat.

I'm 100% sure you're wrong in thinking I'm wrong.

You're thinking of the old systems like Michelin's PAX. Current generation SSR tyres (as seen on BMW etc) need nothing extra, though it is recommended you use a pressure warning system.

[Funk]

HellDiver said:

530dTPhil said:

HellDiver said:

.........so you can use them OK on standard rims.

I think that you are 100% wrong there. You can fit non RF tyres to RF rims but not the other way around. I believe that there is a special retaining ridge on the RF rims to ensure that the tyre stays in place when running flat.

I'm 100% sure you're wrong in thinking I'm wrong.

You're thinking of the old systems like Michelin's PAX. Current generation SSR tyres (as seen on BMW etc) need nothing extra, though it is recommended you use a pressure warning system.

BMW say you shouldn't fit RFTs to a non-RFT rim. There is indeed a part of the rim that ensures the tyre stays in place when running flat.

You can fit non-RFT to a RFT rim though, however as has been pointed out, suspension setups are tuned to deal with the increase in unsprung weight of a RFT.

[530dTPhil]

HellDiver said:

530dTPhil said:

HellDiver said:

.........so you can use them OK on standard rims.

I think that you are 100% wrong there. You can fit non RF tyres to RF rims but not the other way around. I believe that there is a special retaining ridge on the RF rims to ensure that the tyre stays in place when running flat.

I'm 100% sure you're wrong in thinking I'm wrong.

You're thinking of the old systems like Michelin's PAX. Current generation SSR tyres (as seen on BMW etc) need nothing extra, though it is recommended you use a pressure warning system.

I'm not familiar with the detail of the old Michelins but I know that they existed. I am talking from personal experience with 115,000 miles in a 5 Series fitted with RFTs; I have seen the rims stripped and there is definitely another ridge in the well to keep the tyre in place.

Technically, you can fit RFTs to non RF rims but there's no point as they wouldn't stay in the correct place on the rim when deflated for the sidewall to support the weight of the car.

[anonymous-user]

Runflats are the work of the devil - avoid!

They have been fitted to Corvettes as standard equipment since 1997. Ditching them in favour of good conventional tyres (Michelin Pilot Sport) gives significant improvement in both ride and handling.

There are similar reports on the BMW forums.