Runflat Rear Only?

Street · Post by **Street** » Thu Sep 16, 2021 9:21 pm

I need to renew my fronts (225/45/18) of a staggered set. The rears are in good shape - BridgeStone Potenza Runflats 255/40/18

I'm an advocate for the benefits of removing the runflats but does anyone have an opinion on replacing them in stages?
Non-runflat fronts and runflat rears?

Is the non runflats alone going to help with any tramlining and ride quality?

Zforbes · Post by **Zforbes** » Thu Sep 16, 2021 9:35 pm

Street wrote: ↑Thu Sep 16, 2021 9:21 pm I need to renew my fronts (225/45/18) of a staggered set. The rears are in good shape - BridgeStone Potenza Runflats 255/40/18

I'm an advocate for the benefits of removing the runflats but does anyone have an opinion on replacing them in stages?
Non-runflat fronts and runflat rears?

Is the non runflats alone going to help with any tramlining and ride quality?

You may get a difference in responses but IMO keep the axles the same and you'll be fine, tramlining is mainly the fronts so changing them to non RFT's will make the biggest difference. I did this on an E46 some years ago now with no issues what so ever, just don't forget to buy a slime / compressor kit just in case of a punture

Ride quality isn't as big as a difference as the tramlining though but a decent non RFT will give you lots more grip

ronk · Post by **ronk** » Thu Sep 16, 2021 9:52 pm

Zforbes wrote: ↑Thu Sep 16, 2021 9:35 pm
……. but a decent non RFT will give you lots more grip

I think that answers the question.

Don’t do it! Change all four tyres is the safest way.

Street · Post by **Street** » Thu Sep 16, 2021 10:01 pm

Cheers guys
Both good advice. I'll have a look into what I might get second hand for the rears towards replacements and go from there.

M1k3yC · Post by **M1k3yC** » Fri Sep 17, 2021 11:09 am

I've posted my thoughts on runflats vs. non-runflats before. In short, I didn't like the Bridgestones that my E86 came with but was fine for years with Michelin runflats. I've recently moved away from runflats altogether and noticed a slight improvement but nothing (in my opinion) revolutionary. Some forum members have posted on here that runflats have improved a lot over recent years and now would be less concerned about running them.

To your question, I think that it depends on how you drive. I am normally not concerned about mixing tyres on a car as long as they are the same brand and type on each axle. My MX-5 is running like that until a couple wear out and I can match them all. However, if you like to drive hard and near the limit and expect a significant difference in grip between the front and back axle then I absolutely would not mix tyres in the way you're considering. You only need that to catch you out once and the bill will be much more than two tyres

Personally, I wouldn't do what you're asking about for any length of time, despite what I've said about my MX-5, just because I don't like the idea of 50% runflat tyres. That's just my thoughts - the choice is yours and what's important is that you're confident in the car and consider it safe.

brillomaster · Post by **brillomaster** » Fri Sep 17, 2021 11:57 am

how long do you think the rears will last before they need replacement?

sounds like it'll be a while yet, in which case i'd take the runflats off and put them on ebay.

i ran a mis matched run flat/non run flat combo on a daily driver with no adverse issues, but only did it so i could buy front tyres from one paycheck and rears from the next.

Mr Tidy · Post by **Mr Tidy** » Fri Sep 17, 2021 9:53 pm

I've never had issues with tramlining on BMWs (E46s and E86M) with non run-flats, but I had a few other models (E87 1 Series and E9* 3 Series) with Pirelli, Continental and other brands of run-flats that didn't seem to suffer from it either.

The Bridgestone Potenzas on my 3.0Si Coupes were just awful, but as they had decent tread on both cars I never got around to swapping them for "proper" tyres.

As someone said non runflats on the front should help with any tramlining, but given where you sit in a Z4 I think the rears would be far more likely to improve the ride.

I've never tried it but I can't see why having two of each at opposite ends should be a problem, unless you are driving like you stole it!

You could always try selling your rear Potenzas, or maybe just turn the T/C off and have some fun.

kinger · Post by **kinger** » Sat Sep 18, 2021 12:00 pm

Ive just had a similar decision to make .
I recently broke a 326 alloy on the back of my car, i bought a new one from Poland and went to get the tyre swapped.
The run flat Potenza tyre had started to delaminate inside so i swapped the rear pair for 'normal' tyres, the difference is ride is amazing.
So the front pair will be swapped very shortly, i think they will bring in enough money to self fund the swap.

As my car was sat waiting for its new alloy to arrive i was playing with my Carly, i got distracted and left it in for a little over 2 weeks.
So flat battery and 'Hand Brake' failure followed.
I do have a mate with a garage that has all the BMW software, he reset my car for me to sort that problem out.
So if anyone in the Somerset / south west area is looking for someone to fix their handbrake failure without paying BMW prices...DM and ill pass their info on.
Mike

Z4-forum.com

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