[tomgrey]

Seen lots of threads about RFT vs Non RFT and what tyres are good. Going to set off for tour of europe shortly and tyre fitter reckons rears have 1-2000 miles left. They are of course perfect except about 1 inch strip on inner side.

Fronts are still very good.

Tyre fitter says non RFT on rear with RFT on front should be fine. However, I have read other posts and 'oli' has said he would not do this, but others 'fub' have done it.

Too defer expense I would prefer to have 2x new rears (Conti 3's) for now and when the fronts go, get same on front.

By the way, the car is e93 M sport highline 330d.

Or I could have all conti 3s fitted and try and sell tyres on ebay?

255/30/R19 rears and 225/30/R19 fronts.

I would welcome advise. Thanks,

[HighlandPete]

The tyre industry do not recommend mixing RFTs and non run-flats even axle wise. Some clearly publish the reason/warning being different tyre characteristics, which is of course what we all know. So a tyre fitter stating the above, about rear fitment, is not really in order. I'm not sure his boss is covering the insurance liability when a guy makes such a statement.

Personally I wouldn't want the mix anyway, as it could be that one bend, when the grip snaps away and it all goes pear shaped. Much like having poor tread depth on the rear, often nothing much you can do to correct things.

HighlandPete

[Mr Plum]

+1.

I was in the same position and considered it for about 30 seconds..... then fitted 4 new tyres.

Actual cost of binning the tyres 1000/2000 miles early?? Offset that against the feeling of driving across europe on quality roads with 4 of the same tyres...

French motorways if they are wet don't drain too well - I'd want lots of tread and 4 tyres that were going to react the same way!

[m1bjr]

Originally Posted by Mr Plum

I'd want lots of tread and 4 tyres that were going to react the same way!

But you don't have that anyhow.

The fronts a very different size to start with

Thinking outside the apparently obvious logic here.
What is the REAL difference from having other tyres on the rear axle?
I mean, what will it REALLY affect, providing the non RFTs are a quality tyre?

The fronts compared to the rear already have:
Different size
Different loading, inlcluding having to steer the car and all the angle changes involved.
Different Camber and toe, hence different wear patterns and contact patch geometry.
Different loading, the rears are driven and the fronts are not.
Different inflation pressures, and many play with that anyhow.

So in strictly physical, logic and Engineering terms - why would it ACTUALLY matter that you had non RFTs on the back?

[HighlandPete]

Start with the fact the car is set up to work on four tyres of the same brand and type, even if the sizing/load rating is different. OK some of the settings are to get the car to understeer, to be more safe for the average driver. Also cars may be supplied with different brands, we know how that can change a car's dynamics, so even that is not always too subtle. But that is another subject.

Now add a different tyre to the rear, with different lateral stiffness, etc, and different slip angles and see the handling balance change in controlled conditions. Same can be found even changing to worn treads on the rear, hence the advice to fit new tyres on the rear (if possible) in preference to the front.

A little bit of history on BMW tyre sensitivities, teaches us even different tyres specs of the same brand can completely mess the handling balance and induce sudden breakaway. The E46 330i is particularly sensitive to a proper tyre mix, even mixing Michelin PS2 and PS1 can throw the DSC into confusion. Let alone mixing brands. Even BMW and the tyre makers have scratched their heads as to why the 330i has been so messed with simple tyre changes. Add a bit of trailing arm bush wear, and mixed tyres, and the cars can become almost undriveable near the limits.

I'm aware of a BMW garage with BMW involved swapping wheel sets to try and find out exactly why a 330Ci was having DSC intervention and why the car was unstable. The garage car was fine on the tyre mix, the customer car virtually undriveable. The car with troubles was so different with a same spec' tyre set. Almost perfect, but it showed mixed sets and a bit of softening bushing really mess with a car. Only when the rear trailing arms were replaced and the tyres all the same, did the customer get the car driveability, he had before he replaced a couple of tyres. Sometimes as tyres wear they 'wear to fit' and can mask a bit of suspension wear and a couple of new tyres show the wear and is evident by poor stability and sometimes very weird dynamics.

BMW with rear wheel drive are pretty sensitive cars to many tyres, so mixing just adds to any potential issues.

IMO, always wisest to run a same spec tyre on all four corners. That's been my view way before RFTs came about, they just compound the issue on mixing.

There can be exceptions, but you really need to know what you are doing and what performance changes you are after, or will get.

HighlandPete

[ShereKhan]

I don't think your insurance company would see it that way. If you crashed your car they would want any little reason to wriggle out of a claim.

I personally would have full RFT or full non RFT. Might be worth checking out of there are any cheap tyres in Calais (assuming you can make it there). You could also try Costco in Avonmouth.

[Baby Dave]

I had non rfts at the rear and rfts at the front for about a week.I wouldn't recommend it.It felt like the rear of the car was pushing itself through the front it wobbled at speed and over 60 mph the car was very unstable. Mine is only a 320d god noes what would happen in a 330d

[Giff]

Originally Posted by Baby Dave

I had non rfts at the rear and rfts at the front for about a week.I wouldn't recommend it.It felt like the rear of the car was pushing itself through the front it wobbled at speed and over 60 mph the car was very unstable. Mine is only a 320d god noes what would happen in a 330d

That sounds like pretty much what you'd expect bar the wobbling!
Fitting them to the rear would effectively reduce the spring rate and promote understeer, did you get them balanced?

[ed335d]

Originally Posted by Baby Dave

I had non rfts at the rear and rfts at the front for about a week.I wouldn't recommend it.It felt like the rear of the car was pushing itself through the front it wobbled at speed and over 60 mph the car was very unstable. Mine is only a 320d god noes what would happen in a 330d

I had a pair of RFT's on the front of the M for a couple of days while I was waiting for new tyres to be delivered, didn't feel too bad (although I wasn't pushing it)

[tomgrey]

Thanks for all the replies. naturally I want to believe that Non RFT on rear with RFT on front will be fine especially as that costs less. Logical head also says right size rear tyre with right size front tyre should be fine, and that some tread patterns will mix better than others.
In the end I think the right answer is either to replace rears with like for like, or get 4x new all NON RFT. If I keep the RFT fronts when they come off, if I do not like the Non RFTs, then when rears wear out again, I can put the old fronts back on, new RFT on rear.
From what everyone has said about tyres the conti 3s seem a good Non RFT choice. Anyone want to pitch some ideas about cost for 4 of these, fitted and balanced?
If that is what I do I will post the final price so we can see who was closest.

255/30/R19 rears and 225/35/R19 fronts.

Big thanks to all you guys and gals for responses and advice so far.

[rup]

I've been driving for approx 5 months on Falken rears and RFT bridgestone fronts. The ride and especially the (lack) of tramling is now much better than when had 4 RFT.
I drive my car hard and have never experienced anything dangerous. RFT are NOT fundamentally different to non-RFT tyres, ie layers of rubber/metal/composite materials etc. They just have a stronger side wall.
IMHO run flats are down right dangerous due to horrible tramlining.
Yes, 4 non-RFT is ofcourse ideal but mixing them is still better than 4 RFT.

[tomgrey]

Hi All,

have decided to get 4x conti SP3 and keep the old set of bridgestone RFT and either sell on ebay or put them back on when I come to sell. Already had a 12v compressor to pump the tyres and now have added the tyreweld kit. Will keep both in the car, just in case.

I am off to france, spain and portugal and I know some of the roads are even worse than UK roads for potholes, so having SP3 non RFT should make the ride better.

Once I am back I will post an update about the difference in ride quality and performance. I don't push the car that hard bit do enjoy the overtaking capabilities, which is perhaps why the rears are so much more worn than the fronts.

Thanks to all for your advice.

[m1bjr]

Originally Posted by rup

I've been driving for approx 5 months on Falken rears and RFT bridgestone fronts. The ride and especially the (lack) of tramling is now much better than when had 4 RFT.
I drive my car hard and have never experienced anything dangerous. RFT are NOT fundamentally different to non-RFT tyres, ie layers of rubber/metal/composite materials etc. They just have a stronger side wall.
IMHO run flats are down right dangerous due to horrible tramlining.
Yes, 4 non-RFT is ofcourse ideal but mixing them is still better than 4 RFT.

Good intel and perfectly logical.
But I doubt anyone here will believe you.
Except me of course

As regards quotes about slip angles...
Increasing a slip angle on the rear may not be a bad thing at all on a car that inherently understeers.


I had all the same unfounded comments when I switched my S2000 (regarded as 'a twitchy handful' on a good day) to non-stagger.
Yes, I was about to die and spin off into oblivion. Massive oversteer/Rear Bias/Tail Happy/Yada Yada.
It drove fine on road. Just like stock actually with a bit more tramlining from the wide fronts.
I drive hard, very hard. And as the times I logged on track will attest, it was a huge improvement.
No DSC on that car

I bet there are thousands upon thousands of cars operating with totally different wheel and tyre combos to that which the manufacturer intended on our roads.
In fact a lot of the time you cannot even obtain some oem tyres in the original sizes, so forcing a change. The early S2K is actually one good example.
And what about all the thousands of aftermarket wheel/offset/tyre combos out there - incidently all insured and declared (hopefully).

I suspect this will cue the 'But a BMW is 'special' comments. It aint.
And everyone still drives to work and home in one piece generally.

So long as the tyres are roadworthy, of the correct load rating and inflated and installed to the manufacturers guidelines, then an insurance company will have no need to question them.

So many many people cite this as a massive issue - the insurance.
But who has ACTUAL experiance of an insurer refusing a claim due to having RFT on one end and Non RFT on the other?

[rup]

Thanks for your comments m1bjr. I notice that a lot of people claiming impending doom by mixing RFT & non-RFT have never tried it themselves.
I'm not encouraging anyone to do anything they're uncomfortable with, just giving my real world experience.

[nik_nak]

I had RFT's on the rear and Falken non RFT on the fronts of my 330d and never noticed any issues.
Ian

[tony20009]

Maybe things are different in the UK, but I've got non-RFT on front and RFT on rear right now. I'm not having any issues driving on city streets and US highways.

[doughboy]

the issue to me is why would you want to mix rft and non rft??

either you want the 'benefits' or you don't.

if you don't want spend the money on rft's then don't moan about it and just buy normal tyres.

you'll have a transition period, just be aware you are going against the manufacturers useage instructions during that time. its no different to say using a directional tyre the wrong way round. just watch out for beady eyed insurance assessors.

normal tyres are so cheap, jusy get 4 if thats the way you want to go.

[tomgrey]

Hi All,

had the conti 3's fiitted today. Not sure I can agree that they were cheap as someone suggested in earlier post, £755 for 4 new tyres, versus £550 odd for two new rears. Yes they cost less, but there not cheap!

Haven't driven more than 1/2 mile yet. But I am hoping that as I have convertible, that for our europe trip, the non RFT will make the car more of a GT tourer and less of a go-kart.

I have no problem with driving a go-kart, but when your on a 4-5,000 mile round trip it stands to reason that if you want to enjoy it you won't be pressing on hard for 6 hours every day and taking each corner like a ball in a bagatelle.

I will post an update of my first impressions once I get to Portugal and may start another theard of conti versus bridge rft.

Thanks again to all for their opinions they have all been a great help.

[m1bjr]

Originally Posted by doughboy

its no different to say using a directional tyre the wrong way round. .

Running a road tyre fitted correctly cannot be compared to running a road tyre incorrectly fitted (backwards).
Obviously.

[HighlandPete]

Guys can do what they like with fitting tyres, but I'll not put a comment on the 'net, when there is a possible safety issue, other than what is recommended as the correct fitment about mixing tyres.

I'm old enough to remember when cross ply and radial ply were being mixed, and cars were very dangerous in some instances. Legislation sorted most of that out, radials on rear axles only.

I can imagine if the internet existed in those days, we would be having comments like... "I have radials on the front and cross plys on the rear and I don't have any issues".

Sorry I don'y buy into the "I don't have issues" as reliable data on whether there are issues or not. Car makers test such things, like worn tyres, front and rear, different specs, worn dampers, etc. Hence the recommendation to fit new tyres to the rear these days, if replacing pairs. I think they have a bit more data, from controlled circumstances than the average internet poster.

The Tyre Council do not recommend mixing run-flat or non run-flat, even axle wise.

HighlandPete

[doughboy]

Originally Posted by m1bjr

Running a road tyre fitted correctly cannot be compared to running a road tyre incorrectly fitted (backwards).
Obviously.

With all due respect, both are instances of not following the manufacturers instructions.

A directional tyre fitted backwards is not inherently immediately dangerous as long as it is fitted properly, it just that the tread won't perform as specified and it is not tested as such. So the instruction is 'don't do it'.

Same with mixing RFTs, this is not formally type tested or proven, so the manufacturers say 'don't do it', if you do you are in unknown territory.

Agree with Pete's comments about radials v cross plies, i've though of that comparison before and I think it is very similar to this discussion.

[doughboy]

Originally Posted by tomgrey

Hi All,

had the conti 3's fiitted today. Not sure I can agree that they were cheap as someone suggested in earlier post, £755 for 4 new tyres, versus £550 odd for two new rears. Yes they cost less, but there not cheap!

Good choice!

My comment about 'cheap' was that non rfts can be cheap, i.e. budget tyres can be had for £200 (not on 19's though!!) a set if that's what you really want, although good quality mid-budget brands like falken or kumho can be had for under £400 for a set of 4 (18") fitted, balanced the lot.

No one does cheap RFTs!

So for those where cost is an issue or the driving factor, you can get cheap tyres and in that case you'd be better going for 4 NEW cheaper tyres than mixing new and old RFTs and non RFTs. You can always sell odd RFTs on ebay to those who want to keep them.

But you (like me and others) have gone for the pricey but, IMO, the best non RFT you could buy for your car - the CSC3

Maybe the CSC 5P now, but the 3's are still great