[gIzzE]

http://www.e90post.com/forums/showthread.php?t=581273

[Jules6]

Purely on my experience (and I have been running non rfts for 35k miles) I would agree with Gizze, as I have found that running my Contis at 3-4psi above the sticker pressures is not only both best for feel and grip but also can't be too far out as the wear is spot on.

[gIzzE]

That was actually the reason I spoke with Michelin originally, I was getting excessive wear on the inside edge, as do many with run flats, and they told me that they were under inflated and they were wearing on the inside more due to the way BMW set up the angles.
So I went from 34psi to 38psi and after that they were fine, wore perfectly from them on.

[bnasim]

So I took the plunge and fitted vredestein ultrac sessanta's to my E92.

Although they appear chunkier and less sleek than the Bridgestones, so far so good and the ride has been great.

I have set the pressure to 2.7 rear and 2.6 front. How does that sound?

The only problem is that Ive been advised to fit new valves on them as the existing ones are rusty and needs replacing.

Apparently they are a special order from BMW and normal standard valves wont do? They are metal valves. I have 19" wheels.

Is that the case? Ive called around the dealerships and they have to be ordered in.

[AdrianSi]

Originally Posted by gIzzE

That was actually the reason I spoke with Michelin originally, I was getting excessive wear on the inside edge, as do many with run flats, and they told me that they were under inflated and they were wearing on the inside more due to the way BMW set up the angles.
So I went from 34psi to 38psi and after that they were fine, wore perfectly from them on.

This makes sense to compensate for the weaker sidewalls of the non rft's. The stiff sidewalls of the rft's are the cause for the increased stiffness in ride quality. The weaker more flexible sidewalls will give this slightly wandering feeling, however grip levels wont generally be decreased (tyre dependant i.e premium vs budget) by this and often will actually increase the grip levels as the tyres are less likely to break away when pushed to the limit.

I used to do a lot of track day'ing a few years back in hot hatches, and the only decent tyres we could get to fit our rims (5.5x13) were taller sidewall profiles than we could use on the road. You did get this slighly jelly feel to the suspension and steering, however combined with stiff suspension set up it actually felt more controllable on the limit as you could feel the tyres breaking away. The stiffer lower profile tyres will tend to just breakaway without warning. Its all about the trade off.

Only thing i would say about running higher pressures is to consider what the maximum pressure rating of the tyre. If you are close to the limit you must also consider that when running on hot days and higher speed/loading conditions that the tyre pressure will rise...sometimes by 5 degrees!

[witeagle]

So what do you folks do for the spare that run non-RFT?

[m1bjr]

Originally Posted by gIzzE

http://www.e90post.com/forums/showthread.php?t=581273

That doesnt answer anything.

At the end of that thread you state that the pressures were higher on the E46 than on the E9x.

Its a completely different car - geo, weight, everything!

[m1bjr]

Originally Posted by AdrianSi

I used to do a lot of track day'ing a few years back in hot hatches, and the only decent tyres we could get to fit our rims (5.5x13) were taller sidewall profiles than we could use on the road.

You did get this slighly jelly feel to the suspension and steering, however combined with stiff suspension set up it actually felt more controllable on the limit as you could feel the tyres breaking away. The stiffer lower profile tyres will tend to just breakaway without warning. Its all about the trade off.

The reason your taller 'track' tyres apparently generated more grip is down to the increased slip angles

This is just one reason why RFTs are a crap choice on a performance car (and why they are not on the M cars)

The sidewall has almost no flex so you likely won't get to optimum slip angles for the tyres - and therefor optimum grip levels.

And another reason why making the non RFT retrofit sidewalls harder by pumping up the TP is not always a great idea.
You may have a 'perceived' increase in turn in 'feel' but you can LOSE 'grip'. One makes no difference to the cornering ability, the other makes a large contribution

Steve.

[BIGTIME]

Nissan GTR's have runflats and they handle well.

[zltm089]

Originally Posted by BIGTIME

Nissan GTR's have runflats and they handle well.

plus one....

why tho...?

[bnasim]

Originally Posted by m1bjr

The reason your taller 'track' tyres apparently generated more grip is down to the increased slip angles

This is just one reason why RFTs are a crap choice on a performance car (and why they are not on the M cars)

The sidewall has almost no flex so you likely won't get to optimum slip angles for the tyres - and therefor optimum grip levels.

And another reason why making the non RFT retrofit sidewalls harder by pumping up the TP is not always a great idea.
You may have a 'perceived' increase in turn in 'feel' but you can LOSE 'grip'. One makes no difference to the cornering ability, the other makes a large contribution

Steve.

Out of interest what tyres are on the M cars? Does that mean they carry spare saver wheels and the kit that goes with it?

[m1bjr]

Originally Posted by BIGTIME

Nissan GTR's have runflats and they handle well.

Interesting, I didnt know that.

[chris_s1]

Originally Posted by BIGTIME

Nissan GTR's have runflats and they handle well.

People do complain about the ride of the GTR being harsh on the road, many of the reviews when it came out noted that.

However, I think people have very different expectations for the type of ride in a hardcore sports car compared to a family saloon........

[F31-340i]

Originally Posted by MB London

I recently took the plunge and got shot of my runflats which were (as everyone knows) a pain in the backside. Splashed out on conti 5’s and initially was really pleased with the difference, however I am now not so sure now.
The handling and steering are just so much different now and not in a positive way, on runflats the car was on rails and if you pointed the car in a direction it would stay there until you touched the wheel with any sort of gesture. Now, the car appears to move from side to side, is no way near as planted as before and the steering feel so much lighter.

Could it be that the garage fucked the alignment up? Or is it more likely to be my head playing mind games. Don’t get me wrong, the car is much quieter and absorbs the craters in the road in a way which make the car a better place to be but I think I miss that firmness of the steering with runflats

I had basically the same experience. See thread - by post#8 I had changed the 19" RFTs to 19" non-RFTs and had the same feeling as you

http://www.e90post.com/forums/showthread.php?t=376130

You get used to it however - after a while you forget how much sharper it was on RFTs and it still handles very well on non-RFTs - its all relative.

[HighlandPete]

Originally Posted by ///ajd

..You get used to it however - after a while you forget how much sharper it was on RFTs and it still handles very well on non-RFTs - its all relative.

It is all relaative, also every tyre/wheel change involves a set of compromises, trading one thing for another. Can't have the sharpest turn in, without losing somewhere else. It also depends what our priorities are, and how we try to achieve them.

HighlandPete

[CarAbuser]

Currently running 30.5 front 33.5 rear as per door plate on my non-rfts.

Given the advice here should i run 34/36 or go higher?

[gIzzE]

Originally Posted by m1bjr

That doesnt answer anything.

At the end of that thread you state that the pressures were higher on the E46 than on the E9x.

Its a completely different car - geo, weight, everything!

If you take the Alpina D3 which runs on Pilot Sport 2's and is the same as the 302d the pressures are 2.6 front and rear, which is just over 37psi.