The great run flat tyre debate.

[Swervin_Mervin]

RobM77 said:

Swervin_Mervin said:

RobM77 said:

On my last E90 (a 2007 320d SE) I used to regularly go from run-flat standard BMW fit Conti-sport contacts (205/55/16 I think) to Dunlop Winter Sport non run flat tyres. Aside from the obvious changes in tread deformation when cornering (which was horrible on the winters), the non runflats gave a nasty bouncy ride. Basically, the tyre sidewall is part of the suspension and that's what an RFT equipped BMW's suspension is tuned for - change an element in that and it's no longer as designed. I couldn't wait to get the RFTs back on in spring each year.

I currently own another E90, this time a 2010 LCI 320d ED, and that doesn't have RFTs, shunning them for Michelin Energy Saver tyres. This isn't really relevant to the discussion though, because the ED suspension was notoriously bad. I switched to Birds' suspension and kept the Energy Saver non-RFT tyres. It's a vast improvement, but the Birds kit is designed to work with non-RFT low profile 17s and 18s, not my non-RFT balloon profile tyres. I can't help wondering if I could improve the ride and handling further by switching to RFTs to get closer to the sidewall stiffness that the non-RFT larger tyres have....

You could just try some better non-RFT tyres than energy saving ones! You can't expect a reasonable comparison between soft winter/energy saving non-RFT to normal/sport oriented RFT tyres

Look for extra load versions of the likes of the Eage F1 or the Michelin PS3

Thanks. I like lower grip and find the car progressive enough for me. I’m worried that Eagle F1s will give me too much grip?

Fair enough. I used to run Firestone Fuelhawks on the back of my old mk1 CLio 16v with grippy Yoko Paradas on the front to get the best blend of front end grip and rear end movement.

Maybe try and see if you can get Extra Load variants of the fuel saver ones at least, as the stiffer sidewall should help.

[RobM77]

Swervin_Mervin said:

RobM77 said:

Swervin_Mervin said:

RobM77 said:

On my last E90 (a 2007 320d SE) I used to regularly go from run-flat standard BMW fit Conti-sport contacts (205/55/16 I think) to Dunlop Winter Sport non run flat tyres. Aside from the obvious changes in tread deformation when cornering (which was horrible on the winters), the non runflats gave a nasty bouncy ride. Basically, the tyre sidewall is part of the suspension and that's what an RFT equipped BMW's suspension is tuned for - change an element in that and it's no longer as designed. I couldn't wait to get the RFTs back on in spring each year.

I currently own another E90, this time a 2010 LCI 320d ED, and that doesn't have RFTs, shunning them for Michelin Energy Saver tyres. This isn't really relevant to the discussion though, because the ED suspension was notoriously bad. I switched to Birds' suspension and kept the Energy Saver non-RFT tyres. It's a vast improvement, but the Birds kit is designed to work with non-RFT low profile 17s and 18s, not my non-RFT balloon profile tyres. I can't help wondering if I could improve the ride and handling further by switching to RFTs to get closer to the sidewall stiffness that the non-RFT larger tyres have....

You could just try some better non-RFT tyres than energy saving ones! You can't expect a reasonable comparison between soft winter/energy saving non-RFT to normal/sport oriented RFT tyres

Look for extra load versions of the likes of the Eage F1 or the Michelin PS3

Thanks. I like lower grip and find the car progressive enough for me. I’m worried that Eagle F1s will give me too much grip?

Fair enough. I used to run Firestone Fuelhawks on the back of my old mk1 CLio 16v with grippy Yoko Paradas on the front to get the best blend of front end grip and rear end movement.

Maybe try and see if you can get Extra Load variants of the fuel saver ones at least, as the stiffer sidewall should help.

Thank you, I didn't realise that extra load tyres existed. With the Birds suspension my car corners noticeably faster now, plus I regularly tow with a very high nose weight, so the loading on the tyres is often quite high.

[RDV8]

So Marbles......what did you go for in the end?

[11jhw]

I've recently purchased a 340i touring with GY Asymmetric F1's and was anxious with all the negative runflat talk. As tyres go I've always loved Michelin's but fact that my car had Goodyears RF's when I purchased it (my second favourite brand) that was a bonus. As tyres go they give decent feed back and grip and considering how I've been treating them they are standing up well to wear. My last car I would see 7000-8000mls out of a set of rear OM Continentals and yet the Gy F1's still look like the day I got them which is impressive and a relief after 4000mls. But I do hate hitting pot holes as it feels so harsh that it will buckle a wheel and the car is unsettled at speed on a classic British B road and doesn't inspire confidence more a challange. But having a 118I as a loan car for the past couple of days it confirmed how non compliant my car was. Yes it had runflats, but sensible size wheels with plenty of profile to protect the wheel. Now weather this is down to more weight, larger wheel size, run flats or profile on the 340 I don't know. But the confidence I could carry speed at in the 118i while really enjoying it down a bumpy B-road i recon would surprise faster BMW's. So for me its Michelin Pilot Sport 4s's next time to see if they make a great car better for British roads.

[Mr Tidy]

11jhw said:

I've recently purchased a 340i touring with GY Asymmetric F1's and was anxious with all the negative runflat talk. As tyres go I've always loved Michelin's but fact that my car had Goodyears RF's when I purchased it (my second favourite brand) that was a bonus. As tyres go they give decent feed back and grip and considering how I've been treating them they are standing up well to wear. My last car I would see 7000-8000mls out of a set of rear OM Continentals and yet the Gy F1's still look like the day I got them which is impressive and a relief after 4000mls. But I do hate hitting pot holes as it feels so harsh that it will buckle a wheel and the car is unsettled at speed on a classic British B road and doesn't inspire confidence more a challange. But having a 118I as a loan car for the past couple of days it confirmed how non compliant my car was. Yes it had runflats, but sensible size wheels with plenty of profile to protect the wheel. Now weather this is down to more weight, larger wheel size, run flats or profile on the 340 I don't know. But the confidence I could carry speed at in the 118i while really enjoying it down a bumpy B-road i recon would surprise faster BMW's. So for me its Michelin Pilot Sport 4s's next time to see if they make a great car better for British roads.

I'm guessing your car may have 19 inch wheels with a very low profile tyre - most BMW owners with 19s and fun-flats seem to suffer terrible ride, but worse still cracked or split rims because the tyres have no "give" in them.

I had a 123d with M-sport suspension but only 17 inch rims and Pirelli run-flats and that rode pretty well.

I've now got a Z4 Coupe with 18 inch rims and M-Sport suspension on Bridgestone run-flats, and the ride quality is pretty poor! Last year I bought a set of 18 inch wheels with Falken winter tyres that are non RFT - I must get round to putting them on to see how much difference it makes!

[E-bmw]

It'll be like someone has just switched the suspension on, night & day.

[anonymous-user]

Mr Tidy said:

I'm guessing your car may have 19 inch wheels with a very low profile tyre - most BMW owners with 19s and fun-flats seem to suffer terrible ride, but worse still cracked or split rims because the tyres have no "give" in them.

I had a 123d with M-sport suspension but only 17 inch rims and Pirelli run-flats and that rode pretty well.

I've now got a Z4 Coupe with 18 inch rims and M-Sport suspension on Bridgestone run-flats, and the ride quality is pretty poor! Last year I bought a set of 18 inch wheels with Falken winter tyres that are non RFT - I must get round to putting them on to see how much difference it makes!

A bmw with 19” low profile tyres will rise badly and risk cracked rims run flats or not. It’ll also suffer uneven tyre wear, run flats or not.

[anonymous-user]

E-bmw said:

It'll be like someone has just switched the suspension on, night & day.

I very much doubt it. It’ll ride a little softer but will also wallow and pitch a bit, especially as they’re winter tyres.

[Prinny]

REALIST123 said:

A bmw with 19” low profile tyres will rise badly and risk cracked rims run flats or not. It’ll also suffer uneven tyre wear, run flats or not.

I agree with your first sentence. Your second is conjecture.

Not bashing into kerbs, or thumping into potholes or sleeping policeman, i.e. keeping the alignment correct, as well as being vigilant on checking tyre pressures has meant that all 4 of my 19” wheeled (ok, the 7 is on 20”) BMW’s owned have had consistent wear across the tyre width. They might not always last that long... but that’s a different topic!

[E-bmw]

REALIST123 said:

E-bmw said:

It'll be like someone has just switched the suspension on, night & day.

I very much doubt it. It’ll ride a little softer but will also wallow and pitch a bit, especially as they’re winter tyres.

When I went from 17 RFT to 17 non-rft it was like night & day, suddenly the suspension worked & the tyres gripped (both were CS5 so not the tyres) so yes, I think it will be VERY noticeable.

Mine wasn't bmw but the physics are the same no matter what the car.

[RobM77]

RobM77 said:

On my last E90 (a 2007 320d SE) I used to regularly go from run-flat standard BMW fit Conti-sport contacts (205/55/16 I think) to Dunlop Winter Sport non run flat tyres. Aside from the obvious changes in tread deformation when cornering (which was horrible on the winters), the non runflats gave a nasty bouncy ride. Basically, the tyre sidewall is part of the suspension and that's what an RFT equipped BMW's suspension is tuned for - change an element in that and it's no longer as designed. I couldn't wait to get the RFTs back on in spring each year.

I currently own another E90, this time a 2010 LCI 320d ED, and that doesn't have RFTs, shunning them for Michelin Energy Saver tyres. This isn't really relevant to the discussion though, because the ED suspension was notoriously bad. I switched to Birds' suspension and kept the Energy Saver non-RFT tyres. It's a vast improvement, but the Birds kit is designed to work with non-RFT low profile 17s and 18s, not my non-RFT balloon profile tyres. I can't help wondering if I could improve the ride and handling further by switching to RFTs to get closer to the sidewall stiffness that the non-RFT larger tyres have....

An update: I've just switched my non-RFT winters (Dunlop 4D sport) to RFT winters (Pirelli Sottozero 3) and can confirm that my suspicions were correct: the ride has been improved noticeably (less bouncy), as has the turn in (less sidewall deformation I presume). The handling in extremis is noticeably worse though, which is a shame. They're also a tad noisier. I could only find two winter RFTs online though, and the others (Goodyear) had poor reviews. I'm convinced now though and when I replace my summer tyres they will definitely be RFTs.

ETA: Handling issue sorted. The tyre fitter had set the rears 0.3bar too low and the fronts a touch low. Back to the correct pressures now and the handling's fine.

Edited by RobM77 on Thursday 15th February 20:34

[Roma101]

I wonder if age has anything to do with it. When I got my car new with RFs it was fine, but after about 18 months I started to feel issues with it (wobbly steering wheel, harsh ride). Perhaps they "go off" quicker and more abruptly than normal tyres? I have no evidence for that, but I haven't had the same thing with any of my non-RF cars in the past. On PS4s now and if I have to buy another car with RFs as standard, I will probably only run it on the factory RFs for 6 to 12 months and then swap. No regrets going to PS4s and they will be my default choice again.

[RobM77]

Roma101 said:

I wonder if age has anything to do with it. When I got my car new with RFs it was fine, but after about 18 months I started to feel issues with it (wobbly steering wheel, harsh ride). Perhaps they "go off" quicker and more abruptly than normal tyres? I have no evidence for that, but I haven't had the same thing with any of my non-RF cars in the past. On PS4s now and if I have to buy another car with RFs as standard, I will probably only run it on the factory RFs for 6 to 12 months and then swap. No regrets going to PS4s and they will be my default choice again.

If there was an issue I'd probably encounter it, and I haven't yet. I'm not saying it doesn't happen though, just describing my experiences. Due to my high motorway miles (I do 25-30k miles a year, 85% of which are on the motorway at a steady 70), my tyres last for a long time. I've not seen the symptoms you mention on either my RFT equipped E90 SE or my non-RFT equipped E90 ED.

The only issue I've had with tyre age is my non-RFT Michelin Space Savers got so old that the rubber perished (fine cracking visible on the sidewalls) and they started to blow out. I had three or four blow outs in the space of a month or two last winter, I then replaced them all and haven't had an issue since. I just had a tyre deflate on my non-RFT Dunlop winters, and that tyre was from 2011 (used for 2-3 months each winter and with 3-4mm left, so that's 1.5 years of use, but 7 years old); again I replaced all four just in case.

[Swervin_Mervin]

Roma101 said:

I wonder if age has anything to do with it. When I got my car new with RFs it was fine, but after about 18 months I started to feel issues with it (wobbly steering wheel, harsh ride). Perhaps they "go off" quicker and more abruptly than normal tyres? I have no evidence for that, but I haven't had the same thing with any of my non-RF cars in the past. On PS4s now and if I have to buy another car with RFs as standard, I will probably only run it on the factory RFs for 6 to 12 months and then swap. No regrets going to PS4s and they will be my default choice again.

I think they're just cr4p when the tread blocks are worn beyond a certain point, which isn't after all that long IME.

[Roma101]

RobM77 said:

Roma101 said:

I wonder if age has anything to do with it. When I got my car new with RFs it was fine, but after about 18 months I started to feel issues with it (wobbly steering wheel, harsh ride). Perhaps they "go off" quicker and more abruptly than normal tyres? I have no evidence for that, but I haven't had the same thing with any of my non-RF cars in the past. On PS4s now and if I have to buy another car with RFs as standard, I will probably only run it on the factory RFs for 6 to 12 months and then swap. No regrets going to PS4s and they will be my default choice again.

If there was an issue I'd probably encounter it, and I haven't yet. I'm not saying it doesn't happen though, just describing my experiences. Due to my high motorway miles (I do 25-30k miles a year, 85% of which are on the motorway at a steady 70), my tyres last for a long time. I've not seen the symptoms you mention on either my RFT equipped E90 SE or my non-RFT equipped E90 ED.

The only issue I've had with tyre age is my non-RFT Michelin Space Savers got so old that the rubber perished (fine cracking visible on the sidewalls) and they started to blow out. I had three or four blow outs in the space of a month or two last winter, I then replaced them all and haven't had an issue since. I just had a tyre deflate on my non-RFT Dunlop winters, and that tyre was from 2011 (used for 2-3 months each winter and with 3-4mm left, so that's 1.5 years of use, but 7 years old); again I replaced all four just in case.

Ok, thanks for that. Probably just the RFs I had having stupidly stiff sidewalls and not great. They were the standard 3 series Bridgestone/Contis (can't remember which one). These characteristics meant that on the deeply rutted sections of the M25, the steering wheels wobbled quite markedly. I put the Michelins on and that side effect all but disappeared.

[RobM77]

Roma101 said:

RobM77 said:

Roma101 said:

I wonder if age has anything to do with it. When I got my car new with RFs it was fine, but after about 18 months I started to feel issues with it (wobbly steering wheel, harsh ride). Perhaps they "go off" quicker and more abruptly than normal tyres? I have no evidence for that, but I haven't had the same thing with any of my non-RF cars in the past. On PS4s now and if I have to buy another car with RFs as standard, I will probably only run it on the factory RFs for 6 to 12 months and then swap. No regrets going to PS4s and they will be my default choice again.

If there was an issue I'd probably encounter it, and I haven't yet. I'm not saying it doesn't happen though, just describing my experiences. Due to my high motorway miles (I do 25-30k miles a year, 85% of which are on the motorway at a steady 70), my tyres last for a long time. I've not seen the symptoms you mention on either my RFT equipped E90 SE or my non-RFT equipped E90 ED.

The only issue I've had with tyre age is my non-RFT Michelin Space Savers got so old that the rubber perished (fine cracking visible on the sidewalls) and they started to blow out. I had three or four blow outs in the space of a month or two last winter, I then replaced them all and haven't had an issue since. I just had a tyre deflate on my non-RFT Dunlop winters, and that tyre was from 2011 (used for 2-3 months each winter and with 3-4mm left, so that's 1.5 years of use, but 7 years old); again I replaced all four just in case.

Ok, thanks for that. Probably just the RFs I had having stupidly stiff sidewalls and not great. They were the standard 3 series Bridgestone/Contis (can't remember which one). These characteristics meant that on the deeply rutted sections of the M25, the steering wheels wobbled quite markedly. I put the Michelins on and that side effect all but disappeared.

Interesting. I've certainly not had problems - the RFTs were standard BMW fit ContiSport Contacts (I think? Continentals for sure). As reported earlier, the main thing I've noticed is if you go to non-RFTs the ride is bouncier because you lose the overall spring rate.

[Mr Tidy]

RobM77 said:

Interesting. I've certainly not had problems - the RFTs were standard BMW fit ContiSport Contacts (I think? Continentals for sure). As reported earlier, the main thing I've noticed is if you go to non-RFTs the ride is bouncier because you lose the overall spring rate.

But then yours are an SE and an ED, so probably 16 or 17 inch wheels with a highish profile so even RFTs may have a bit of give in them - like my 123d on 205/50 x 17s had.

[RobM77]

Mr Tidy said:

RobM77 said:

Interesting. I've certainly not had problems - the RFTs were standard BMW fit ContiSport Contacts (I think? Continentals for sure). As reported earlier, the main thing I've noticed is if you go to non-RFTs the ride is bouncier because you lose the overall spring rate.

But then yours are an SE and an ED, so probably 16 or 17 inch wheels with a highish profile so even RFTs may have a bit of give in them - like my 123d on 205/50 x 17s had.

That was a relative statement, so what I meant was that RFT sidewalls will usually be stiffer than non-RFT sidewalls. As you infer though, if you think the ride of your car is too harsh and you want a lower spring rate, ditching RFTs is one way to achieve that. However, the dampers and other aspects of the car's suspension will have been designed around the RFT, so there will be some negative aspects - what you think of the end result then just depends on your own preferences for the various pros and cons.

To answer your question, yes, both my cars have had 16s and that's my preference. I always go for the smallest wheels possible: less unsprung mass, usually a better ride, quieter, better fuel economy, and for me less grip is more fun. The 205/55/16 size is also very cheap to buy! I've also found over the years that most cars usually work best in their standard or highest volume spec.

[ExVantagemech..]

As for the blowout issue, my 17's have Bridgestone RFTs and Ive lost count the number of punctures Ive picked up and ran on before the warning came up on the dash.
The RFTs are crashy, harsh and tramline so badly when 75% worn that the car is almost dangerous on some overbanded repairs.
So much so my wife will only drive the car if its in the 16" winters ( Uniroyal m&s non rft)
I have to say the ride truly is night and day - but not all of it good. The tyres on it now roll and squirm when pushed, yet the RFTs felt planted on high speed corners. Ive just got a set of staggered 18's which again have RFTs but im undecided as to run them as is or fit some rainsports.
Id rather risk a high speed blowout than suffer the constant fidgeting and go-kart style correction required from the Bridgestones. Any day.

[E-bmw]

ExVantagemech.. said:

Id rather risk a high speed blowout than suffer the constant fidgeting and go-kart style correction required from the Bridgestones. Any day.

^^^^100% this.

I find it impossible to relax when on RFTs on all but the most perfect roads & conditions.