Mixing Tyre Types

[craigdm]

What are the groups thoughts on mixing RF and NRF tyres Front & Rear?

When I bought the car last year it failed the MOT on rear tyres so the dealer fitted 2 new RFs.
Fronts are now getting marginal, so I was considering fitting NRFs in a vain attempt to improve the ride on the 19" rims.

Not too sure this would make a massive difference, maybe new RFs would be an improvement anyway.

 

[Deepseaskateboard]

It’s not optimal.

It will still drive from A to B, but I wouldn't do anything excessive in it.

Best to have four matching corners, runflats or not.

 

[mcbutler]

Hi Craig,
When I tried to do this on my first Zed about 5 years ago I online ordered new Non - RFT Michelin PS4, booked a fitting session and drove doen. The guy immediately spotted the RFT tyres on the front and refused to fit non rft on the rear. I though that was BS but after contacting/visiting several fitting ststions none of them would do it, apart from a seedy used tyre joint.
Dont know if its definitively illegal but common sense would suggest its very dodgy.
Going back a few dcades they wouldnt fit radials with crossplys because of the sidewall behaviours, and sidewalls are the definitive difference between non rft/frt.
Your options are to run your fronts to min tread then replace all 4 or maybe try and find some used fronts to last till the rears go. Lots of reputable used tyre suppliers, usually the spares from wrecked etc vehicles.

 

[Chippie]

My advice for what it’s worth is to bite the bullet and buy new front and rear non run flats, then sell your old rears to recoup some of the cost, you don’t have to buy a premium brand but certainly don’t buy budget.

 

[SonnyA85]

It should be fine if it's matching across the same axle. I wouldn't mix across an axle but different front and rear is absolutely fine.

 

[SonnyA85]

Hi Craig,
When I tried to do this on my first Zed about 5 years ago I online ordered new Non - RFT Michelin PS4, booked a fitting session and drove doen. The guy immediately spotted the RFT tyres on the front and refused to fit non rft on the rear. I though that was BS but after contacting/visiting several fitting ststions none of them would do it, apart from a seedy used tyre joint.
Dont know if its definitively illegal but common sense would suggest its very dodgy.
Going back a few dcades they wouldnt fit radials with crossplys because of the sidewall behaviours, and sidewalls are the definitive difference between non rft/frt.
Your options are to run your fronts to min tread then replace all 4 or maybe try and find some used fronts to last till the rears go. Lots of reputable used tyre suppliers, usually the spares from wrecked etc vehicles.

That's funny because majority of cars have budget ditchfinders on them. The idea that they are happy to install a £10 tyre on a car but not premium tyres which match across an axle is mind boggling

 

[Busterboo]

My advice for what it’s worth is to bite the bullet and buy new front and rear non run flats, then sell your old rears to recoup some of the cost, you don’t have to buy a premium brand but certainly don’t buy budget.

Good advice, craigdm, surely?

And the price difference between quite good and very good ain't much, anyway.

 

[craigdm]

Interesting experiences there.

I have worked as an automotive design engineer and never heard about fitters refusing to mix RFs and NRFs.

I'd never mix on an axle, but I'm surprised there would be any risk front to rear. Surely it can't be a safety thing as worn rears and new fronts would produce a more dangerous offset.

Not driving it much at the moment as I'm working from home. It might have to go as the ride is just too harsh. Think I sold the wrong car when I let my mx5 go in March!

 

[Nanu]

As long as the tyres on each axel are the same then what you propose is legal. However if you had an accident, it may give an insurance company a chance to question any claim. They may not succeed but why risk it. I would bite the bullet and change all 4 and if the tyres being changed are in good nick, sell them.

 

[Mr Tidy]

If the main issue is with the ride you could always look for a set of 17 or 18 inch wheels - you may even find a set with non run-flats already fitted.

Then you could sell your 19s so the total cost may not be that much!

 

[mr wilks]

What are the groups thoughts on mixing RF and NRF tyres Front & Rear?

When I bought the car last year it failed the MOT on rear tyres so the dealer fitted 2 new RFs.
Fronts are now getting marginal, so I was considering fitting NRFs in a vain attempt to improve the ride on the 19" rims.

Not too sure this would make a massive difference, maybe new RFs would be an improvement anyway.

The answer is a simple one & cheaper than changing the car , fit non runflats ( ideally all 4 ) & fit 255 35 19 to rear .
The ridiculous 30 profile coupled with RF sidewalls is a recipe for split alloy rims :roll:
Bmw persevered for many models over many years when Porsche , Mercedes , Audi all fitted a 35 profile to 19 inch rims .
Recent models they have finally seen some sense & dropped the 30 .

 

[flybobbie]

Need B Manning's advice on tyres.... :roll:

 

[craigdm]

I never realised that there might be a market for good used tyres. I'll look into that.

Happy to buy a full set of NRFs if I could be sure that this would improve the ride quality.
I'd like to stick with the 19" rims though as they look good.

Can I go to a 40 front/35 rear profile without any issues? I realise that the speedo might under read slightly.

 

[Chippie]

When I bought my 35is it already had non run flats fitted and I don’t think the ride is that hard on the 19’s although it also has the adaptive suspension so that may help, but from reading other posts it does seem that the non run flats with around 34psi front and 36psi rear are a softer ride than the hard run flats.
I don’t think you would have any problems increasing the profile although it may spoil the look slightly.

 

[Mr Tidy]

Can I go to a 40 front/35 rear profile without any issues? I realise that the speedo might under read slightly.

Given how many Z4s and sets of wheels "mr wilks" has had I'd be amazed if he hadn't fitted those profiles to one of his cars!

If it helps I had 255/45 x 18 tyres fitted to the rear of my Z4 last year instead of the OE 255/40 x 18 size and haven't had any issues - if anything the speeds is now more accurate.