[patonjames]

Ok, I used the search function and Google. A lot. And deduced that there is a lot of crap out there about tyre pressures without any final concrete answer.

My dilemma is that I have a 335i E91 LCI that has:

- Just been fully aligned at BMW
- Had AG M359s fitted with non runflat Kumho KU39s
- Front 245/35ZR19
- Rear 275/30ZR19

On the door jam, the BMW recommended pressure for 19" wheels (not fully loaded) is 2.9bar front and 3.2bar rear, which equates to a monumental 42psi front and 46psi rear, cold. The marking on the tyrewall states do not exceed 50psi so on a hard drive (trackday or summer thrash) Im guessing that 50psi will be exceeded.

And besides, I tried those pressures (as recommended by many) and the front does not feel good at all, very light and tracks horrendously.

So, I tried 38psi all round, and while the front feels better, the rears feel like they are squirming around at the back under hard acceleration.

Finally I settled with 36/40psi and while the car feels a bit more planted, the front could still be more planted, like the prior set up I had with MV3 18" tyres with 38psi.

Has anyone gone through this non runflat handling journey and can offer some authoritative and valuable input based on experience or professional recommendation?

Thanks for any help, its most appreciated!!

James

[smuler]

I switched from B'stone RFT's to Michelin Pilot Super Sports back in May and asked the tyre place and Michelin about pressures, giving them my plate so advice was based on my specific car. I also did a post on here, the general forum, for advice.

I tried several recommendations and nothing worked as well as.....

Yes, you guessed it, what the door jam says. I think,as I'm not by the car, my staggered 19s were 36 and 43. I'd say with the MPSS' I feel I am driving the car to the limits of it's chassis so I got it right for me.

As another vote for the door jam advice I changed late last month to a 17s square set up instead of staggered for my winter tyres and once again, I find the best advice is the door jam.

My car is coupe, so may not be the nitty gritty advice for you, but a big vote for just going with the door jam.

[pmmcbl]

I run the standar 18" on my E91 335i but with Michelin sports and use te numbers on the door. The car feels good but can't wait to get replace them with non run flats.

[Maph]

Hi James,

I have found my E91 very sensitive to both tyre pressures and brands, only thing you can do is keep experimenting with different pressures until you find the sweet spot.

Here is my experience:

Mine is running the Bird's kit (with up-rated anti-roll bars, M3 front suspension and rear bushes) on 313s fitted with 235/35 and 265/30s Goodyear Ass2 non runflats.

When I bought it it was running the same suspension and the MV3 on Michelin non-runflats.... I found the best pressures for me were 33F/38R.

I then changed to the 313s with Continental 5ps and I ran them at 36F/38R, any higher and they were really uncomfortable...... I assumed it was the trade off for going from 18s to 19s.....

Long story short the rears wore through the sidewalls, which I think was a combination of poor alignment and low tyre pressures.

I am currently running Goodyear Ass 2s all around at 38F/43R and they are soooooo comfortable compared to the Contis.

I know new tyres will feel more comfortable with more tread but considering the rears had 5mm+ on them (apart from the split/wear at the bottom of the sidewall) and the fronts had 4mm+ on them it is light and day.

I replaced the rears first and the fronts a couple of months later, as I could feel the difference in comfort between the two axles.

I would go so far as to say it is riding better now that it did on the 18s.

I have been a fan of Goodyears for a while but having tried others on this and other cars of mine over the last couple of years (Contis, Pirelli, Michelin, Bridgestone, Dunlop) I will only be running Goodyear or Michelin in the future.

If I were you I would certainly go higher on the rears if you can bear the ride, to reduce the risk of excessive wear, especially as you have gone for 275s.

Best of luck with it.

[Aragorn30d]

your tyre sizes are very similar to what the M3 runs, so why not look there for pressures?

[patonjames]

Maph,

Thanks for the input, very logical and will give it a try. I ran the Kumhos on my remapped 530d on 19" and they felt great. Shame I cannot remember what pressure I used :-(

Aragorn,

I did check M3 Cutters, etc. and came up with the same conclusion - many different opinions and most threads coming back to what is printed on the door jam.

Do you have an E90 M3 door jam that you could photo/print the details on here? That may be a good way to go.

In the meantime I will try the 38F/43R cold pressure set up and see how that feels.

Will report back soon.

Thanks guys

[BarrySt]

For what it's worth, I recently checked with BMW re tyre pressures for non-run flats and they said use the same pressure as for run flats (so per door frame data)

[Digitalize]

I do 40/45 on my 18" Eagle F1s

[Aragorn30d]

Originally Posted by patonjames

I did check M3 Cutters, etc. and came up with the same conclusion - many different opinions and most threads coming back to what is printed on the door jam.

Do you have an E90 M3 door jam that you could photo/print the details on here? That may be a good way to go.

Agreed, and thats what i meant, run the factory M3 figures.

I think this is an M3 sticker:

http://www.m3post.com/forums/attachm...3&d=1352807395

The M3 door jam figures seem to be a lot lower than the normal E90 ones. 2.4 bar all round.

[patonjames]

I have a result....

Per chat with Barons BMW, they would have been able to search the parts DB for the label if I had an M3 VIN or Registration Number. The chap said to leave it with him and he would call back with some answers.

This got me thinking, so I went onto realoem.com and searched for a 2009 M3 LCI E90 in right hand drive and managed to find the label (see attached photo)

Looks like the M3 with 19" wheels and non run-flat MPSS in 245 and 275 runs lower pressures than I originally thought. It is 2.3bar front and 2.5bar rear (33/36).

Just back from a drive with these pressures and the car feels a lot more planted, not flighty at all like it felt before. I'm happy with these pressures for now and will keep an eye on tyre wear.

Thanks for all the help guys!

[Aragorn30d]

those tyre sizes dont look right for an E90 M3

Look at my label above, the M3 factory fitment is 18's in 245/265 both 40 profile and 245/265 both 35 profile in 19"

Your sticker shows MUCH larger tyres, with the 19's listed as having a 45 and 40 sidewall.

I suspect the image of the label in realoem is just a generic picture, rather than an exact representation of what it should look like, and those sizes are off a 5/6/7 series or something.

[patonjames]

Well spotted!

I checked a few different cars and the label is the same, to your point.

Will have to call Barons BMW back as they have not yet called me.

[patonjames]

Ha!

They are reluctant to tell me as the car is not an M3 and they could be liable. 2.3 and 2.5 is not far away from the 2.4 2.4 in the picture you linked.

If I get the chance later I will adjust and go out for a drive. Worse case will find somewhere selling an M3 and ask to look around the car, taking a photo while I enjoy the view!

lol

[patonjames]

The car definitely felt 100% better to drive with 2.3 and 2.5bar, so I dont think Im a million miles away.

[windymissile]

I have been down this same road with my E90 with those same tyres. I'll have to double check tomorrow but I think I settled on 2.4 all round.

WM