Run Flats Are A Disaster!

[Dego]

Just thought I would share my opinion after having to buy a new tyre after a run flat got punctured. I bought my IS200 with 4 run flat tyres on and a normal spare. The spare had never been on the car and the rear tyres had very little wear. Any how I got a puncture on rear dvr side last week, and could I get anyone to even try to plug or patch it?.......Not a chance!!! Tried 5 different places and all told me I needed to buy a new tyre, not happy about that. Ended up putting the spare and a new tyre on the back, and kept the unpunctured rear as the new spare. All the tyres were Continental turanza so it worked out ok. The original spare was luckily (strangely) a normal tyre. So now I have run flat fronts and normal rears and I will be phasing out the fronts when I need to change them. Got me thinking afterwards, the previous owner was a woman, and she probably had the run flats put on for peace of mind, but for anyone who CANT afford to buy a new tyre every time they get a puncture, avoid the run flats like the plague!!!!

[Tony-Bones]

How come you have RFT's on the IS.... There not OEM are they?

[Dego]

How come you have RFT's on the IS.... There not OEM are they?

Definately not, my car is a 2002, I don't even think run flats were common place then. I reckon the previous owner put them on. I didn't notice when I bought the car in January. I read somewhere that runflats shouldn't be put on a car if they didn't come as standard, something about the suspension settings and runflats being a complete package??? Did you ever hear that??? I will be changing the fronts soon enough anyhow.

[Tony-Bones]

It's incredibly dangerous to use RFT's on a car not designed for them.

Reason for this is the tyre sidewall is armoured to support the cars weight in the event of deflation... In reply to this the suspension is "down graded" to compensate for the lack of pneumatic compliance.

Incorrect marriage of this means the tyre will "bounce" off the road hitting a bump since the damper cannot reply to the combined (RFT/coil) compression.... Basically the coil/oil ratios are destroyed.

Whoever fitted these to the car or allowed the owner to fit them if requested should be charged with attempted murder!!

[Dego]

As I am not the most educated on cars/tyres/suspension etc. I didn't realise the seriousness of this. I seen it as merely an inconvenience having to buy a new tyre in the event of a puncture. I bought the car with the run flats fitted unbeknown to me, from a small time independant dealer. I doubt he even knew he was selling a car with incorrect tyres. I know the previous owner was a woman from the documents, and I reckon she was probably ignorant to the situation too. I have just checked through the reciepts that came with the car, but there was nothing for tyres. The two runflats on the front of the car have tread for the short term future, but now I think I should change them next week to have normal tyres on all 4 corners. Cut my losses, they would need changed in a couple of months anyway.

[Tony-Bones]

Please get them off!!

To explain the full picture....

The RFT once deflated is deemed scrap because the deflated limits regarding driven miles is 50. Since the only way to test the condition of the armoured sidewall is Xray then the tyre industry has to assume the tyre is not safe to be repaired although the actual repair is the same as any other tyre.

The refusal to repair the RFT means there is a flood of them in the second hand tyre industry who do repair them (legally) then sell them on to the unaware consumer.

It's probable the seller of your car bought them to replace the badly worn fronts and didn't care they were second hand (part worns)

I absolutely despise RFT's but they will be mandatory on all new cars in the EU by 2015.

[Dego]

I will change the fronts on tuesday. I will still have one runflat remaining as a spare but I will eventually change it. Its all money, money, money. Thanks for the explanation and advice.

[Tony-Bones]

I will change the fronts on tuesday. I will still have one runflat remaining as a spare but I will eventually change it. Its all money, money, money. Thanks for the explanation and advice.

Since these have been on the car since you bought it then you really will enjoy the splendor of the IS once the correct tyres are fitted :)

[Parthiban]

This is really interesting information Tony, I had never thought it could cause such a serious difference to have runflats. Is it not a similar situation then if you fit different stiffer suspension? Or is it ok that way round? Sorry if this is a dumb question but it's quite an eye-opener that stiffer tyres could cause such serious consequences.......

[Tony-Bones]

I despise RFT's..... Why? this is why!

The 'RFT' concept does have a point regarding safety and hazard, but the evolution belays a few convenient areas not on public display.........so in true wim fashion........

Principle

The RFT can resist and react to most forms of deflation, sudden or progressive and permit the driver to continue with the journey regardless of the deflation, valuable for safety and it assures the owner that nothing would deny the destination other than fuel or the M25.

Evolution

The concept has been realised over many years, Dunlop suggested the 'Denovo' which was a tyre locked between a split rim, this wheel had no internal recess that allowed the tyre to 'off-set' and detach from the rim, this also involved internal canisters that would be crushed and released a gel to keep the tyre cool... at the time the concept was very expensive and ultimately failed, apart from cost the fundamental flaw was if the tyre deflates then it was 'scrap'

Following this commercial failure Dunlop abandoned the concept of the 'split rim' and introduced the 'Demlock' tyre, this carried the same concept and placed the gel in the tyre without the canisters..... a new evolution of wheel was designed to support this but very costly... in fact Jaguar was the main recipient and offered this safety factor deep within the sales campaign... again this failed.. fundamentally for the same reason if the tyre deflates it is 'scrap'.

Then things went quiet..........

Very quiet!

With the birth of the new Mini One/Cooper in 01 Pirelli answered the run flat question again with the 'PAX' design of tyre and rim, basically the rim has internal shoes that supports the tyre and simply replaces the air after deflation... but a new problem was born?.... not only was the tyre scrap after deflation but now only the main dealer had sufficient machinery to remove/ replace the tyre, in time ultimately i feel this will also fail.

Today's evolutions expand on past examples, now the RFT will fit any rim and most shops should be able to fit/ remove the tyre.... but something is missing?..... where is the gel.... where are the internal shoes.... what keeps the tyre cool once deflated?

Construction

The evolution is evident, make the tyre wall armoured and it will suspend the car.....

So they did...... the new Goodyear and Bridgestone are now OE within BMW and associated marques, Pirelli have taken a back seat for now..... but there is still a problem?

The tyres needs to communicate with the car directly via internal censors or externally via the ABS, visible activation on the dash will need to be re-set/ turned off by the dealer, this i feel angry about! (another topic maybe)

A warning

If you have RFT then it's a done deal... due to the armoured construction of the tyre the suspension has been 'down graded' to accommodate the tyre, you cannot deviate from the set-up unless the suspension is also modified, so in essence the tyre/ suspension is a package and must be considered as final.

Oh and to add insult even the new variations of 'run flat tyre' once deflated is 'SCRAP'

[Monster-Mat]

hence why Lexus removed the run flats on the sc430

[Tony-Bones]

hence why Lexus removed the run flats on the sc430

And what a wise move was that!!!

[eddiea1]

I absolutely despise RFT's but they will be mandatory on all new cars in the EU by 2015.

thats insane!

[Tony-Bones]

I absolutely despise RFT's but they will be mandatory on all new cars in the EU by 2015.

thats insane!

I agree..... If i recall correctly all new cars in the US by 2012, EU by 2015.

The RFT limits your choice of tyre and compound and is an absolute nightmare regarding the chassis and other handling issues..

The cost of these tyres are extortianate so in reply to the impending regulation Kumo tyres now make RFT's in an attempt to capture the budget market.... In my opinion the RFT evolution is going from bad to worse!!

[jsj24uk]

I always thought it was illegal to have run falt tyres fitted if you didn't have tyre preasure sensors fitted. Correct me if I'm wrong though. I also noticed that Holts are now advertising these new tyre inflation can's which you can use in the event of a puncture. Is it true that once used, the punctured tyre can't be repaired? Sorry for going off topic. Where can I be sent for my 100 lashes?

[Tony-Bones]

I always thought it was illegal to have run falt tyres fitted if you didn't have tyre preasure sensors fitted. Correct me if I'm wrong though. I also noticed that Holts are now advertising these new tyre inflation can's which you can use in the event of a puncture. Is it true that once used, the punctured tyre can't be repaired? Sorry for going off topic. Where can I be sent for my 100 lashes?

Superb question.... no "lashes needed"

There is no legislation in the UK regarding RFT's. Although there is confusion between the RFT and the (no spare wheel) concept born from the space saving, wide wheel, shallow boot, no room due to design now on the market type of car.

So yes the Holts "can-O-air" is required.... Whereas in the RFT's case no air is needed...

If you think back the evolution of the "space saver" this was the parent of the Holts "can-O-air" and in some cars now no spare tyre at all.

UK laws needed to be reviewed to accommodate a spare tyre with the width a quarter the size of the distressed wheel and most times 3 to 6" smaller in diameter!!

By comparison is the RFT better... Yes

Is this evolution good for us....No