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      11-08-2011, 02:43 PM   #1
mikeouk
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mixing run flats and non run flats???

run flats on rear (255/30 r19) need changing, is it ok to fit non run flats and leave the run flats on front until they need changing, they have plenty of life left.
also, 265/30 r19 are loads cheaper for some reason, would it be ok to fit them instead?
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      11-08-2011, 02:47 PM   #2
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No don't do it. The car will handle like jelly
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      11-09-2011, 05:44 AM   #3
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I too am going to have the same issue with my 1 series, where the backs are almost knackered and the fronts still have some life....

Have already bought 4 Pirelli tyres and was planning on changing in pairs as the current one's die...

Is this a def no-no??
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      11-09-2011, 06:55 AM   #4
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Very seriously recommended no-no.

Change all 4, and sell the part worn fronts, either here or on ebay. There's a surprising market for part worn RFTs.
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      11-09-2011, 07:51 AM   #5
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I was advise against doing the same thing recently so just ended up buying a set of rear runflats.
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      11-09-2011, 08:34 AM   #6
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Mikeouk,

Definite no-no.

Spoke with local friendly tyre shop and he showed the difference between RFT and non RFT same brand of tyres [PS3]. Sidewall stiffness completely different. He likened the "RFT v non-RFT" mix and match to the "cross ply v radial" debate ~ 40yrs ago !!!

He would sooner sell me 2 more RFT for same monet as non RFT [like I said he's a friend] than put non RFT on one axle with existing RFT on the other.

Thats my 1p's worth....

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      11-09-2011, 08:38 AM   #7
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Just buy 4 non runflats and sell the two front runflats!
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      11-09-2011, 08:50 AM   #8
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i'm so tempted aswell......my rears will be comin to an end soon...and the fronts got lots of tread left....
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      11-09-2011, 08:55 AM   #9
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Quote:
Originally Posted by Pave Dew View Post
Mikeouk,

Definite no-no.

Spoke with local friendly tyre shop and he showed the difference between RFT and non RFT same brand of tyres [PS3]. Sidewall stiffness completely different. He likened the "RFT v non-RFT" mix and match to the "cross ply v radial" debate ~ 40yrs ago !!!
Same thoughts myself, about the old cross-ply vs. radial position. Characteristics are so different, and who's controlling which axle gets the RFts, with a limited slip angle?

Personally I'm surprised we only have the official "not recommended", "don't do it" type comments for axle to axle fitment, from the tyre and road safety industries. I wouldn't be surprised if we 'eventually' get a legal stance on the issue.

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      11-09-2011, 09:20 AM   #10
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The best thing to do would be to either buy some part worn RFT rears from eBay and work it so that your fronts will need changing at the same time as your rears and switch them all to non-RFTs.

Or if you're desperate to get rid of RFTs, just buy a set of 4 non-RFT's and sell the fronts on ebay. A pair of front RFTs with 5mm tread on eBay should get you around 120 quite easily.
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      11-09-2011, 10:23 AM   #11
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Cross ply vs radial debate..sorry guys, not aware of this

Is it being suggested that there are safety issues associated with running a mix of runflats and conventional tyres or purely ride quality issues??
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      11-09-2011, 11:56 AM   #12
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I did it for about 2 months. Don't do it you cannot drive the car at motorway speeds as the car will wobble at anything over 60. It feels horrible and it's dangerous. It's not illegal but I would swap all 4 and sell the front ones
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      11-09-2011, 11:56 AM   #13
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Quote:
Originally Posted by dakhu1 View Post
Cross ply vs radial debate..sorry guys, not aware of this

Is it being suggested that there are safety issues associated with running a mix of runflats and conventional tyres or purely ride quality issues??
In the 'olden days' so many folks found the ditch, usually backwards, that legislation was brought in to ban mixing cross-plys and radial tyres on the wrong axles. You could only fit radials on the rear, if you had cross-plys on the front, but not the other way around. Definitely not on the same axle, either end.

The tyre experts, tyre makers and safety agencies, clearly state mixing run-flats with conventional tyres, axle to axle, can effect handling and stability. Makes perfect sense, as each tyre type has different build criteria and slip angle characteristics.

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      11-10-2011, 02:13 AM   #14
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I bought my car in June and it had 2 brand new Bridgestone RFTs on the back and 2 brand new non run flats on the front, I had all good intentions of changing either the fronts or the rears but just haven't got round to it.

Why ? Well to be honest guys the car feels fine, it handles well, there's no silly swapping ends if I nail it, nothing of the sort. All the cross ply and radial talk is complete nonsense. No doubt the lack of run flats on the front make the overall feel of the front end a little softer, I doubt if it's much though, we are talking about a 30mm tyre wall, it's not going to give a great deal regardless of what tyre type.

What I wouldn't do is put two different tyre types on the same axle, I don't think that would be too clever !
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      11-10-2011, 03:53 AM   #15
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i wouldnt advise the mixing of the two, just sell the 2 runflats on fleabay.

i would advise buying anything non-bridgestone, ride quality is soooo much better without them. ive got michelins, and got 265/35 on the rear. seems fine.
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      11-10-2011, 04:19 AM   #16
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Quote:
Originally Posted by Abbot26 View Post
Why ? Well to be honest guys the car feels fine, it handles well, there's no silly swapping ends if I nail it, nothing of the sort. All the cross ply and radial talk is complete nonsense.

What I wouldn't do is put two different tyre types on the same axle, I don't think that would be too clever !
Interesting, you will run different types of tyres front to rear, but not similar tyres across the car... strange logic.

Also the "cross-ply vs. radial talk is complete nonsense"... Is that so? Were you back there to see the issues and accidents...? Many back then thought the same as yourself, but the facts proved to be different.

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      11-10-2011, 04:20 AM   #17
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Well i must dissagree with some of you on her i have just changed my rears to nrft and left the fronts as rfts and i am getting no wobble or any bad vibrations at high speeds if anything it is an improvement, im running 19" bridgestone potenzas rfts on the front and contie nrfts on the rear.
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      11-10-2011, 05:13 AM   #18
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Of course there will be some who have odd combinations, who don't feel as if they are compromising on tyre choice, but it never makes it best practice, definitely does't follow the advice or recommendations of the experts.

You may not even feel there is any defficiency, but another driver in that same car, may feel it isn't what it ought to be.

Mixing tyres has always had this sort of reaction. I remember reading a guy using 4 odd tyres on a Ford Focus saying it made no difference than having 4 the same, debating it with another guy who had lost the precision of his Focus, by just changing brands. We don't all come from the same place when driving.

We know there can be major issues on something like the E46 330ci when mixing tyres, front to rear. Again some say it makes no difference to the car, but others have found the car becomes near on dangerous, just by having two odd pairs, even Michelin PS1 and PS2 didn't work together. Get a bit of suspension wear in the mix and that can completely change the tyre mix equation.

Big subject, but the official advice is clear, don't mix run-flats with non run-flats.

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      11-10-2011, 03:38 PM   #19
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Quote:
Originally Posted by HighlandPete View Post
Of course there will be some who have odd combinations, who don't feel as if they are compromising on tyre choice, but it never makes it best practice, definitely does't follow the advice or recommendations of the experts.

You may not even feel there is any defficiency, but another driver in that same car, may feel it isn't what it ought to be.

Mixing tyres has always had this sort of reaction. I remember reading a guy using 4 odd tyres on a Ford Focus saying it made no difference than having 4 the same, debating it with another guy who had lost the precision of his Focus, by just changing brands. We don't all come from the same place when driving.

We know there can be major issues on something like the E46 330ci when mixing tyres, front to rear. Again some say it makes no difference to the car, but others have found the car becomes near on dangerous, just by having two odd pairs, even Michelin PS1 and PS2 didn't work together. Get a bit of suspension wear in the mix and that can completely change the tyre mix equation.

Big subject, but the official advice is clear, don't mix run-flats with non run-flats.

HighlandPete
So pete

Are you saying we should trust tyre manufacturers and the experts (who work for tyre manufacturers) ? They won't have a vested interest in selling more tyres of course

If there is a choice of which experts to take advice from surely that would be BMW, if I'm not mistaken their cars are developed and setup to run on RFT's, as soon as you step away from those you completely compromise the manufacturers design.

This issue is not the same as cross-ply/radial from the 70's and 80's
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      11-10-2011, 04:24 PM   #20
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Quote:
Originally Posted by Abbot26 View Post
So pete

Are you saying we should trust tyre manufacturers and the experts (who work for tyre manufacturers) ? They won't have a vested interest in selling more tyres of course

If there is a choice of which experts to take advice from surely that would be BMW, if I'm not mistaken their cars are developed and setup to run on RFT's, as soon as you step away from those you completely compromise the manufacturers design.

This issue is not the same as cross-ply/radial from the 70's and 80's
They do it to save money, and try as hard as they can to try and get the handling back, but so far have failed in every car I have tied with them.
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      11-10-2011, 05:14 PM   #21
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Quote:
Originally Posted by Abbot26 View Post
So pete

Are you saying we should trust tyre manufacturers and the experts (who work for tyre manufacturers) ? They won't have a vested interest in selling more tyres of course

If there is a choice of which experts to take advice from surely that would be BMW, if I'm not mistaken their cars are developed and setup to run on RFT's, as soon as you step away from those you completely compromise the manufacturers design.

This issue is not the same as cross-ply/radial from the 70's and 80's
The advice is not to mix tyre types, not to buy "more" of anything, don't see the problem with that advice at all.

Now as for BMW and RFTs, we know they are desperate to have RFTs that perform like non RFTs, the official Bridgestone/BMW 'G3' launch proved that very clearly. And now that some models have a tyre option, shows they never got it correct from day one. Also we know some markets wouldn't endorse the RFT, so didn't have them.

I've been driving BMW since the 1970's, and know all too well that BMW compromised the chassis when RFTs were fitted, it wasn't a proven technology, still isn't truely sorted, as the concept is flawed when we know how suspension/tyre systems work best. M-division and Alpina have given their response by not using them, while being developed into the market place.

My view is, BMW is not "designed for run-flats" but "compromised for run-flats". I'll debate that with anyone. I have done so with both BMW and Bridgestone senior technical engineers. Had a senior Bridgestone engineer come and ride in my car, to show the defficiences on highland roads first hand.

But they can't back down, but do know the cars can be better handling, and ride better on conventional tyres.

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      11-11-2011, 01:00 AM   #22
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Quote:
Originally Posted by gIzzE View Post
They do it to save money, and try as hard as they can to try and get the handling back, but so far have failed in every car I have tied with them.
How does fitting run flats, a more expensive tyre, then probably spend millions on developing the handling save BMW money ?
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