[BIGTIME]

Originally Posted by rsmallwo

The physics would suggest to me that normal tyres (non runflat's) would make the alloy wheel less prone to cracking as the tyres have a more cushioning affect than runflat tyres with their stiff sidewalls.

I initially thought this but have read that alloys cracking often occurs when the tyres are underinflated. ie bottoming out. I also read that you won't crack or an alloy my hitting it with a rubber mallet so it shouldn't buckle with a hard rubber tyre that is correctly inflated.

If this is the case the sidewall is hard and you go over a pot hole the tyre doesn't give way so the alloy takes less impact.

I just wish I knew as this would decide which tyres I get next.

[BrianR]

I need to replace my two rear RFT's and I was wondering if it is possible to "legally" have two non-runflats on the rear while keeping the existing runflats (which have less wear than the rears) on the front ?

[dkan]

I have a friend with a 6 series who has done this. So should not be a problem.

Just to give all an update. Replaced my Conti's this weekend with some Kumho KU31. Cost me £280 for 4 tyres, balanced and fitted, which was a very good price. So what do I think ???

To be honest...still not sure. I think I need more time to get use to the car again. To all those thinking of changing from run flats to non run-flats....it's really does change how you car handles....I would say my car is now totally different. Better or worse ?? I'm not sure yet.

Good points :

It's bloody quiet, these tyres are very quiet. Most of the time all I hear is wind noise, engine, and suspension creak...tyres are very quiet indeed.

The ride it much softer, no more crashing around when hitting bumps. It's like the shocks have been reconfigured.

No more tramlining, drove to MK this evening, and never felt the steering wheel thug once.

Bad points :

Straight after the tyres were replace, the handling of the car totally changed. To be honest, I didn't like it. It was very soft and had no feel. However, on checking the tyre pressure they had put 30PSI all round. Lower than what I had in the run flats. So I bumped them up to 31PSI (front) and 34PSI (back). Feels a lot better, but I think I need to bump the fronts up maybe to 33PSI and backs to 36. The Kumho's are really soft, so this maybe the reason too.

Cornering still feels a little vagues, I guess I just need to get use to the car again. It's a big difference...with the run flats you feel every bump, stone and road....with the non runflat...everything just feels softer...like a comfy slipper. I prefer something in between, and increasing the PSI should help.

As for the tyre....initial thoughs are they are bloody soft....think they are softer than the Toyo Proxes I had serveral years ago, which concerns me a bit because of wear/short life span. Having said that, they have a treadwear rating of 320, which is better than the Conti's 280. They also seems very grippy, I've not really push too hard at the moment, as I need to get use to the car...but they seems to bite the road well in the dry.

Will post update once I get some more air and put some more miles on them.

Any advice for PSI for non run flat 17inch wheels would be much appreciated.

Cheers,

Originally Posted by BrianR

I need to replace my two rear RFT's and I was wondering if it is possible to "legally" have two non-runflats on the rear while keeping the existing runflats (which have less wear than the rears) on the front ?

[BrianR]

Thank you very much indeed dkan, your description is exactly the kind of quiet, smooth, soft result I am looking for, this is my third 3 series with Run Flats and I concur with your comments re. that with Run Flats you feel every bump and I also get a lot of road noise.

I have an E90 with Continental 'Sport Contact 2 SSR' 225/45 R17 91V' tyres on which I have done just over 30000 miles.

The front have less wear than the rears, so I thought I could maybe just replace the rears at the moment.
I am a wee bit concerned on reading about needing to modify suspension setup, etc, so if there is any doubt at all about the mechanical or safety implications specifically applicable to my particular model I'll hold off in the meantime and maybe casually ask my local BMW dealer.

Looking forward to hearing how you get on with these and thanks again dkan.

[mgarvey]

I'll second the opinion on the Kumho's. I replaced my 19" RFT Bridgestones with the Kumho Ecsta Sport Ku31, which if I'm honest was my second choice as Falken 452's were out of stock at the time and I needed them quickly.

After a few early miles of wondering whether I'd done the right thing I started to appreciate the significant improvement in ride and not notice the softer edge to the handling. If you are a performance nut there are perhaps better choices, but on crappy UK roads these are great for most drivers.

[BrianR]

I talked to two different BMW dealers and there was no mention at all about suspension issues, or having to get different wheels, or voiding the warranty, or anything like that at all. Comments expressed concerned the resulting situation in which "no spare" would be available in the event of a puncture.

I have replaced all four with Michelin Pilot Sport 3's, I spent quite a bit of time reading on line and appreciated the very many favourable comments on Kumhos and Falkens, and alternatively having noted that a lot of opinion suggests the Continental non-runflats seem to wear quickly I decided to go for something different and got the Michelins, which apparantly have only been introduced this year. I am hoping to get very long life from these.

I immediately noticed the difference in the smoother ride, all the bumps were now being absorbed while before, with the runflats, every bump and surface was annoyingly felt.
The fitted pressures were 32psi all round, after some 50 miles I inflated the rears to 39psi in accordance with the figures on the door plate (I read that non-runflat tyre pressure and runflat pressures are the same and are as noted on the door plate) and noted the same smoothness but somewhat less soft in handling.
Last night I inflated the fronts to 37psi as I thought I could hear more roadnoise from the fronts than the rears, but I think I'll take the fronts back down again as the tyre pressures would then be as per the door plate, but I'll probably experiment further.
I am overall very pleased and glad I did it.

I bought a can of Tyre-Weld but I am not convinced that tyres can be repaired after using, nor about how effective it would be in the event of a tyre-wall puncture. Tyre fitters seem to wince immediately at the very mention of TyreWeld.
I think that it may be a "get you home" solution but would end up in having to buy a new tyre rather than a possible repair.

Then I thought about having Ultraseal treatment, which from what I have read is apparantly highly regarded, but I came back to thinking that I do a lot of miles, I really need to be as sure as I can be that I am as best prepared as possible for a puncture and then thought about biting the bullet and buying a 'space saver tyre'.

To cut a long story short, the cost quoted by BMW for a space-saver wheel and tyre kit instantly disengaged my interest,
and although there are items of varying condition on ebay I can't see anything for an E90 and I understand if you fit the wrong type of spacesaver wheel it could interfere with the brakes.

So I have decided to buy a wheel for around £60 and have a reasonably low cost tyre fitted that, which I plan to stow in the boot. I know this will take up space but I would rather this spare wheel was there rather than just empty space, and although it may add some weight in the rear it may actually help rear wheel traction with this added mass over the rear axle, if the snow comes this year as bad as it was last year.

[dkan]

Bumped up the PSI to 33 fronts and 36 rears, so much better. I am loving the car now. Feels perfect, comfortable, quiet, but still corners and handles well. So glad I made the switch now. Only real problem now is that it's so quiet I can hear all the suspension creak over speed bumps.

[SixDegrees]

All good input that I'm taking on board. On a note I was discussing ditching the non-RFTs with my BMW dealer and he had no issue with this but it seems now the RTFs are Conti SC3 where as I have BS RE050s.

Car was in for 1st MOT and I got a 320D SE Coupe with 17" Conti RTFs as the loaner odd car, another story) and I have to say these were light years ahead in terms of grip (wet), comfort and noise compared to the BS RE050s. Was set on getting non-RFTs but maybe the advances in RTFs over the past few years and being Contis I might stick to RTFs.

Also, insurer does care about RFT v's non-RFTs only that they are the right size, load, speed.

Anyway, its now winter and so 16" SE alloys with winters going on and I'll address the 18" staggered RTF / non-RTF issue next March.

[BrianR]

33 front, 36 rear here too, seems good!
After nearly a thousand miles with the new non-runflats, I am still aware of some degree of road noise from the Michelins but this is gradually becoming less noticable and may either be because I am becoming used to it or because the tyre tread surface is 'bedding in' and becoming less rough or whatever.

In any case, I do not think they can be nearly as quiet as reported for the Kumhos but they are dramatically quieter than the run-flats I had previously, the car feels much more powerfull, the handling feels good to me, grip in dry or wet is excellent, and I can now hear that the engine in this car is very quiet indeed.

On a smooth-surface stretch of motorway there is practically no road noise at all.

I bought a BMW steel wheel and fitted a Michelin EnergySaver tyre (the tyre size 205/55 16 to fit this steel wheel is different from the four tyres on the car)
This will be the temporary spare and is in the boot, together with a scissors jack, which I have tried and confirmed fits the jacking points on the car, and wheel nut wrench.
I have kept the can of tyre weld so that if the spare gets a puncture, I can use tyre weld for that, so I think I am well covered