[Eelesy24]

It is fine to mix them front and rear.

I work in a BMW dealership and recently we had a customer who wanted to know if swapping to non run flats was approved, and as we couldn't give a definitive answer we emailed BMW technical, and their response was yes it is fine and they said the best way was to swap in stages, with the rear axle first, and then the front at a later date.

Mike

[Frobius]

I'm sure it is fine. Just the same as putting ping pong tyres on is 'fine'.

[imygaf]

Originally Posted by Eelesy24

It is fine to mix them front and rear.

I work in a BMW dealership and recently we had a customer who wanted to know if swapping to non run flats was approved, and as we couldn't give a definitive answer we emailed BMW technical, and their response was yes it is fine and they said the best way was to swap in stages, with the rear axle first, and then the front at a later date.

Mike

This seems a very strange response from bmw. Ok, some people say its fine and others disagree. But what is the reasoning behind saying the "best" way to do it is rear first then front later.

Surely the best way would be all or nothing? Why dont they send the cars from the factory with different front and rear setup if thats the best way?

[ukbeemerboy]

Originally Posted by Eelesy24

It is fine to mix them front and rear.

I work in a BMW dealership and recently we had a customer who wanted to know if swapping to non run flats was approved, and as we couldn't give a definitive answer we emailed BMW technical, and their response was yes it is fine and they said the best way was to swap in stages, with the rear axle first, and then the front at a later date.

Mike

Don't believe that as a response from BMW or your dealership. If you work at a dealership then you will know to AUC a car for the forecourt, if it hasn't got RFT tyres on a car that should have them as OE equipment then you need to fit them to retail it.

[shrink]

Frobius, I think you're being a bit alarmist here. You're assuming that putting different types of tyre on each axle will suddenly make the car unstable in some way. That would be basically saying that the tyres would have completely different levels of grip and performance. I would suggest that as long as they are capable tyres, what difference could it make. Traction is the main concern here, the car and road don't care whether its a run flat or not, as long as traction characteristics are similar.

I wouldn't think putting standard Bridgestone rft rears on, and having the exact same tyre but non rft would turn the car into a death trap. Aside from one being rft, the grip characteristics and tread pattern should be pretty similar.

[MEGA]

Right.

I've run RFT front / non RFT rears all of this year. Including:

2x E90post driving meets
1x Santa pod
1x Bedford Autodrome Open Pitlane
1x Silverstone Open Pitlane.

It has caused me no problem whatsoever. Anyone that says it's terrible obviously has no experience and is just copy pasting something someone else said! Simple as.

Think of it this way.

RFTs have lower grip than non RFTs assuming you buy a good one. That is given.

So what is better:

4x RFT (no grip x 4)
2x RFT (no grip x 2)
0x RFT (no grip x 0)

Obviously, in an ideal world you'll change front and back. But. Changing just the back will clearly give you more performance than being on full run flats.

The tramlining will also decrease, and bumps will feel less harsh.

As soon as you can, get the other runflats moved over too. Mine have a couple k left on them now and will then be dumped for a pair of Contisport 5Ps to match the rear - which I've had waiting to go on a couple months.



This OBVIOUSLy only accounts for having the same wheels on each axle. If you do something mental like make left non rft and right rft, then enjoy your accident.

Rgds
Dave

[MrPogle]

Originally Posted by shrink

Traction is the main concern here, the car and road don't care whether its a run flat or not, as long as traction characteristics are similar.

It's not traction that is the potential concern, it's grip. If you change the grip at one end of the car but not the other there is potential for it to behave differently in extreme circumstances (e.g. a high speed swerve).

Now how much this is a problem is a matter for endless "reckoning" but if you believe that there is little or no difference between an RFT and a non-RFT

a) Why ditch the RFT?

and

b) There is no problem running a mix on the same axle.

[lemonukas]

For MOT I don't think is law in UK to have same tyres on axle. It's is different in EU you have to have 2 same tyres on axle because of handling, braking and bla bla bla. Maybe law it was change.

[Eelesy24]

Originally Posted by ukbeemerboy

Don't believe that as a response from BMW or your dealership. If you work at a dealership then you will know to AUC a car for the forecourt, if it hasn't got RFT tyres on a car that should have them as OE equipment then you need to fit them to retail it.

Why not believe it?

For auc yes you need to put the vehicle to standard as you would if it had any non standard accessories. But this isn't for auc this is for an individual customer, disbelieve me if you like but that was the response from BMW.

[shrink]

Originally Posted by MrPogle

It's not traction that is the potential concern, it's grip. If you change the grip at one end of the car but not the other there is potential for it to behave differently in extreme circumstances (e.g. a high speed swerve).

Now how much this is a problem is a matter for endless "reckoning" but if you believe that there is little or no difference between an RFT and a non-RFT

a) Why ditch the RFT?

and

b) There is no problem running a mix on the same axle.

You're ridiculously over simplifying this. I'm suggesting there need be very little difference in terms of grip and braking performance etc between the two types. Ride quality is a very different matter, and that's precisely why many including myself intend to ditch the run flats. There's also noise and potentially poor cold weather performance on rft

[HighlandPete]

Originally Posted by Eelesy24

Why not believe it?

For auc yes you need to put the vehicle to standard as you would if it had any non standard accessories. But this isn't for auc this is for an individual customer, disbelieve me if you like but that was the response from BMW.

I'd be very surprised if this is the official view of BMW.

For one, they are going against the advice and guidelines of the tyre industry.

British Tyre Manufacturers’ Association
Mixing SSTs with standard tyres
The handling and performance characteristics of SSTs are different to those of standard radial tyres, and so they should not be intermixed on a vehicle, i.e. all four tyres should be similar in structure.

Then there is the individual advice from the tyre manufacturers themselves, now apply industry advice to the insurance companies, and their knack of seeking get out clauses. Such as:

Pirelli does not recommend mixing run flat tyres and standard tyres on the same vehicle, even if paired in axle sets.

From Continental, in a list of WARNING! notes

It is extremely important to keep the following in mind:
An SSR/standard tyre mix should not be fitted on a vehicle – not even axlewise. (In isolated cases a standard tyre can be temporarily mounted on a vehicle otherwise equipped with SSR tyres. It must be pointed out to the driver, however, that the standard tyre has no runflat properties.)

We could find many more quotes.

There is added risk, and if the advice is clearly spelled out, as it is, I can't see BMW going against that industry advice. I'd imagine any reply from BMW had not passed the legal department before release.

If they have made it their official policy, it can be open to challenge if and when someone chooses to. Say if 'incorrectly matched' tyres are viewed as part of the cause of an accident.

I wager it not an 'official' BMW statement.

HighlandPete

[HighlandPete]

I'm minded to enter debate with BMW tomorrow, over the following statement, to find out whether this really is fact, or just some individual opinion from within BMW.

I work in a BMW dealership and recently we had a customer who wanted to know if swapping to non run flats was approved, and as we couldn't give a definitive answer we emailed BMW technical, and their response was yes it is fine and they said the best way was to swap in stages, with the rear axle first, and then the front at a later date.

I had debates in the past with BMW, when wanting to remove my RFTs from the 330d, and even in verbal discussion with BMW Technical, I just can't believe the advice to remove in stages.

HighlandPete

[MrPogle]

Originally Posted by shrink

You're ridiculously over simplifying this. I'm suggesting there need be very little difference in terms of grip and braking performance etc between the two types. Ride quality is a very different matter, and that's precisely why many including myself intend to ditch the run flats. There's also noise and potentially poor cold weather performance on rft

OK and they are perfectly good reasons to ditch the RFT.

The point I am making (and I'm afraid I'm a simple person) is that it is nonsense to say there is no issue mixing them front-rear but it's madness to mix them left-right.

I strongly suspect some people are confusing 250bhp BMWs with run-flat tyres and drum-braked Ford Anglias with radials and cross-plys.

[shrink]

Lol indeed

If the tyres are all modern standard, rated to the car, and have the same tread depth, I can't see mixing being an issue, I've had all kinds of weird cars in the past and some had scary mismatched tyres,

When my mum bought her old 328i, pretty much every tyre was different. It drove perfectly, even when pushing on quite aggressively

[Frobius]

Fair play to all the 'I've never had a problem' brigade...

I still wouldn't do it. And I've never had any probs either! (Touch wood!)

[Hotcoupe]

Originally Posted by gman3msport

My mot station told me it would be a fail! And a very good freind of mine who has his own tyre company told me the exact same thing. Some mot stations might overlook this but I would rather my car mot was done properly and not overlooked. Safety is paramount especially when my daughter is in the car with me.

Sorry Fella,but both your MOT station and friend are incorrect.
Runflats on the rear axle and non runflats on the front are NOT an MOT failure.

It's amazing just how much/many rubbish/scare stories you read on the web,one being that mixing RFT's and NRFT's front/back or back/front means death,voided warranties/insurance policies,even the premature death of kittens and Polar bears.

Amazing!

[MEGA]

I once mixed runflats and non run flats and then my friend's puppy died.

Coincidence? I strongly doubt it.


Dave

[zltm089]

I haven't mixed and would never mix...

It would just feel wrong IMO...

[scottishpete]

Originally Posted by MEGA

I once mixed runflats and non run flats and then my friend's puppy died.

Coincidence? I strongly doubt it.


Dave

RAFLMFAO

[Ajerthan]

Originally Posted by MEGA

I once mixed runflats and non run flats and then my friend's puppy died.

Coincidence? I strongly doubt it.


Dave

Jheeeez LOOL.

Heated discussion.

[Frobius]

Zzz. There are plenty of tyre fitters and manufacturers who say don't do it. Find me a source that says its ok.. and none of this "my mum's best mate's cat's friend who works at a garage where the owner's dad works for BMW", either!

[MrPogle]

You can appreciate that BMW don't need the aggro/cost of testing multiple combinations of things but my handbook says you shouldn't even move your tyres around to even out wear.

If that is their attitude it seems inconceivable that they will be up for mixing tyres.