[DaveC]

Forced into it really - one rear was badly worn the other was almost gone but somehow lost all its air last night - the warning came up as I left work yesterday and I thought - pfft must be a false alarm. Checked em this morning and sure enough there was no air in one of the rears.

Must say, they DO drive well with no air in

Anyway, as it was a rush job didn't have much choice available ended up putting a set of workhorse P6000s on (yeah I know they aren't the greatest but they do a good all round job - had em before).

So, the main reason for this post is really just to say "wow" what a difference. Haven't had a chance to check the performance side of things much, new tyres, damp road etc... but the ride is SO much better. They dont turn the car into a Rolls but they take out so much of the harshness that the RFTs added. Very happy at the moment.

What pressures are the converted types running at? straight out of the tyre place the readings were 32, 36 (fronts) 35, 44 (rears) 44? are they mad? Great job tyre place

Anyway I set them at 30 fronts and 35 rears and it feels pretty good, think I might put a couple more PSI in the fronts.

[E92Fan]

30/35 is too soft - you'll experience a considerable loss of precision in cornering, and will get excessive tramlining too. Try upping the fronts to 35/36 and the rears to 38/39. Ride comfort won't suffer, but the driving feel will be hugely better.

[Oli]

Good to hear, those people with RFT's dont know what they are missing out on!!!

Im running mine on 36 front and 38 rear, and its just perfect for me

Enjoy

[SDRX]

Great idea, glad you like the conversion, crank up the pressures a bit though.

[red-max]

Yes, I think I'm on 36 front 38 or 39 rear too.

I was a little disappointed that the PS2s are almost as noisy as the Bridgestone runflats, but they are much better over uneven roads, and don't crash over holes and bad joins in the road. I wouldn't say I've got a smooth ride (the "Sports" suspension is pretty hard) but it's a lot more bearable for everyday driving.

Funnily enough I was driving the wife's MINI Cooper S yesterday and today. It still has the OEM runflats, and I really noticed how bloody hard they feel - it seems that they amplify every imperfection in the road. I used to get that feeling in the 335d, but switching to non-runflats has improved the ride quite a bit.

[hov333]

hey so what do you do if u get a flat since there's no spare in the trunk? I was also thinking about swapping the runflats but i'm worried about being stranded one day

[red-max]

Originally Posted by hov333

hey so what do you do if u get a flat since there's no spare in the trunk? I was also thinking about swapping the runflats but i'm worried about being stranded one day

Well, it depends how paranoid you are, or how well prepared you want to be if you do have a puncture.

The cheapest solution is to carry a can of tyre-weld "goo" and perhaps a compressor. The M3 and M5 don't have run-flats, they have an M Mobility kit, which is a compressor and a bottle of goo. I bought one of these from the local stealers, I think it was about £100.

Since I travel a fair bit, I also bought a space-saver spare. BMW don't offer one for the E9x series, but I'm told the E46 spacesaver does fit (same bolt pattern), but depending on the model you might need a spacer and longer bolts. I bought a kit from LeatherZ, but I must admit I haven't actually tried it. I'm a bit surprised that no-one in the UK (or Europe) seems to offer something like this, it seems an obvious accessory for BMW owners ditching their run-flats.

The space saver just sits on the floor in the boot. It takes up a bit of space, but not too much. LeatherZ even do a vinyl wheel cover.

Hope that helps.

[Oli]

watch this sapce ref, Space Savers, I think youll find SiBurt is onto something as we speak......

[- Paul -]

I'm on "normal" (non-runflat) tyres on both the 16" and 19" and love them. I have the M3 goo kit in the boot but might be interested in the siburt deal?????????

[squeezebm]

Glad i converted from RFT's

[bts]

Originally Posted by DaveC

Anyway, as it was a rush job didn't have much choice available ended up putting a set of workhorse P6000s on (yeah I know they aren't the greatest but they do a good all round job - had em before).

So, the main reason for this post is really just to say "wow" what a difference. Haven't had a chance to check the performance side of things much, new tyres, damp road etc... but the ride is SO much better.

I'll be interested to read a follow-up comparison once you drive the P6000s a bit. I've previously had these and would never use them again ... but I've typically used PS2s. I have yet to drive my 335i w/o snow tires, but the more I read the boards swapping out the RFTs w/o even giving them a try moves up on my todo list.

[DaveC]

Originally Posted by E92Fan

30/35 is too soft - you'll experience a considerable loss of precision in cornering, and will get excessive tramlining too. Try upping the fronts to 35/36 and the rears to 38/39. Ride comfort won't suffer, but the driving feel will be hugely better.

How are you getting figures that high? I'm looking at the Michelin recommendations for non runflats on my car (32/36) OK its not my tyre but I think thats roughly where I'll end up.

As far as I know higher pressures lead to tramlining not lower.

Edit: The reason for starting the fronts low is so that I can work up over the next few days to see what feels best.

[ChrisMWard]

Originally Posted by DaveC

As far as I know higher pressures lead to tramlining not lower.

I've always found this as well, but different suspension geometries may react to pressure adjustments in different ways.

We're on our 11th and 12th BMWs at the moment and I've always found the centre of the tyres wearing out before the edges when inflated at the recommended pressures. As a result of this I normally run the tyres a few PSI lower than the manual states.

One of my previous cars, an MG ZT, was fitted with 18" PS2s. Now a ZT is a similar size car to a three, with the weight around that of a four cylinder 318/320, has BMW designed, German manufactured suspension at both ends, yet the recommended tire pressures were 28 PSI all round. Tyre wear was very even and it was one of the best handling FWD family cars I've ever driven.

Currently on the PS2 shod 335d tyre wear is very even and there is no evidence of tramlining with the current pressures set at -3 from recommended. On the 120d the Bridgestones are almost at the end of their life with about 2.5mm of tread left after 20K miles. The rears have worn the centre of the tread more, even with a 3PSI reduction in stated pressure and tramlining is now evident on rutted nearside lanes of motorways. Both handling and grip have improved with the reduction in pressure though.

Regards

Chris

[CokerRat]

If you're running stock sizes, I'd follow whatever BMW states. It should be labelled on the sticker in the driver's door jamb and might show up in the owner's manual.

Keep in mind that the pressure recommended by BMW specifically for your car results in a certain size of contact patch for each corner (the specific vehicle's weight at each corner distributed by the pressure in the tires), whereas the tire manufacturers are specifying something generic that does not differentiate between different vehicles of different weights and front/back distributions.

[Oli]

Originally Posted by CokerRat

If you're running stock sizes, I'd follow whatever BMW states. It should be labelled on the sticker in the driver's door jamb and might show up in the owner's manual.

Keep in mind that the pressure recommended by BMW specifically for your car results in a certain size of contact patch for each corner (the specific vehicle's weight at each corner distributed by the pressure in the tires), whereas the tire manufacturers are specifying something generic that does not differentiate between different vehicles of different weights and front/back distributions.

Yeah but no but..... The stock tyre is a RFT, so has a harder sidewall, hence non RFT's will have to be run at different pressures,to compensate for not have the same sidewall!!!

[E92Fan]

Originally Posted by OliH

Yeah but no but..... The stock tyre is a RFT, so has a harder sidewall, hence non RFT's will have to be run at different pressures,to compensate for not have the same sidewall!!!

Correct - remember that our cars are designed with more compliant suspension bushing to account for the rigidity in the runflat tyres - running non-RFT tyres too soft will only increase wallow as the suspension would then be 'soft'.

Incidentally Dave, the pressures of 36F & 38/39R are derived from the Alpina D3 and Alpina B3 cars, both of which use Michelin PS2 Non-RFT as standard on 19" wheels, and both of which ride supremely well... I also double checked with Alpina to get their opinion on pressures on a regular 335i...

[DaveC]

Originally Posted by E92Fan

Correct - remember that our cars are designed with more compliant suspension bushing to account for the rigidity in the runflat tyres - running non-RFT tyres too soft will only increase wallow as the suspension would then be 'soft'.

Not sure about that, given the quality of the ride I'd suggest they were designed with non RFTs in mind and changed at some point for marketing purposes. The tyres would need to deflect enormouse amounts to induce wallow!

Originally Posted by E92Fan

Incidentally Dave, the pressures of 36F & 38/39R are derived from the Alpina D3 and Alpina B3 cars, both of which use Michelin PS2 Non-RFT as standard on 19" wheels, and both of which ride supremely well... I also double checked with Alpina to get their opinion on pressures on a regular 335i...

They seem enormously high to me. I've upped the fronts to 34 and the steering is definitely lighter but to me it seems to have a little less grip.

On a side note - BMW make a big thing about 50/50 weight distribution - why then do the rears need so much more pressure? The whole purpose of having a certain pressure in the tyre is to get the right contact patch and heat production in tyre - surely this is almost exclusively a product of weight??

[Oli]

I have a higher pressure in the rears on mine because its the touring - heavier, and I believe that the 36/38 that I run mine is the same as the D3 touring

[Tallest]

are these pressure recomendations valid for 17in as well non RFT? or even 16in in winter?

Just curious, as I'm planning a switch to 17s in summer after having bought the car just before winter on 16s. Obviously I don't want to buy RFTs and looking at PS2s.

[Cafe.Racer]

Originally Posted by DaveC

On a side note - BMW make a big thing about 50/50 weight distribution - why then do the rears need so much more pressure? The whole purpose of having a certain pressure in the tyre is to get the right contact patch and heat production in tyre - surely this is almost exclusively a product of weight??

Wider rears?

[DaveC]

Originally Posted by OliH

I have a higher pressure in the rears on mine because its the touring - heavier, and I believe that the 36/38 that I run mine is the same as the D3 touring

My old saloon E46 had much higher pressure quoted for the rears so its not that - or if it is BMW are lying in all their "near 50/50 weight distribution" adverts.

[DaveC]

Originally Posted by Cafe.Racer

Wider rears?

Not on 17" rims.