Run Flats or Not Run Flats

[ronk]

A previousE89 of mine with low mileage was absolutely fine at U.K. speeds but was not an easy drive in Germany- at 120 it was a constant battle and it did not instill any confidence - it was running on the standard run flat rubber

This current car is on the supplied rubber and at 145 it feels very very planted (only the speed limiter in the LH seat prevented any increase)

I’m sorry if that muddies the waters - but I suspect the instability comes from the budget tyres

[IanzZ4]

Hi again and thanks to everyone for your advice.

Well the consensus of blame seems to point to the RF tyres and their varying performance.

To be clear it's matching new RF Yokahamas on the front and matching RF Churchills (fight them on the beaches - HaHa very good) on the rear, on the std M Sport 18" rims, 255/35 rear, 225/40 front. Rather unhelpfully somebody has ripped the important part of the tyre pressure label off the door jamb. My 320i has factory fit Potenza RF's same width and profile front and rear, just 19" instead of 18" so used BMW's recommended 2.3bar front and rear for them as a starting point.

Before I commit to spending £500 on a new matching set of non-run flat tyres, I've booked the car in to my local Indy BMW workshop, Hallmark Autos of Maldon (any one know them?) on Monday. I've asked them to carry out a thorough inspection of the car, which should show up any hidden defects.

The dealer I bought it from, View Autos, did their own pre-sales check and an oil service, but I will feel happier with my own independent assessment.

Thanks for your valuable advice and please watch out for my next post after Monday's visit to the workshop.

Best regards

Ian

[axelleveau]

Hi Ian,

I am guessing you meant 225/40 at the front and 255/35 at the rear? (havign the 35 and 40 mixed up?)
2.3 bars front and rear seems fair to me but I am not used to RFTs so they might need a touch more

I think your plan to get it inspected first is fair, at least you can have piece of mind there is no serious suspension issue or even a leaking damper.
I would advice getting the alignment checked, regardless whether you end up changing tires or not you should get it done so you cannot really loose there.

And then take it from there, if ride is harsh then change tyres, otherwise keep it as is

[enuff_zed]

Just looked at mine in the garage. Can't get a decent photo due to the light, but:

225/40 Front = 2.5 bar
255/35 Rear = 2.7 bar

I'm now on non-RFTs and prefer PSI, so after much experimentation I'm running them 34psi front and 36 psi rear.

Hope that helps?

[Busterboo]

Just looked at mine in the garage. Can't get a decent photo due to the light, but:

225/40 Front = 2.5 bar
255/35 Rear = 2.7 bar

I'm now on non-RFTs and prefer PSI, so after much experimentation I'm running them 34psi front and 36 psi rear.

Hope that helps?

Preferring PSI, as I do, or not, 2.5 bar is approximately 36 and 2.7 bar is 39.

[enuff_zed]

Just looked at mine in the garage. Can't get a decent photo due to the light, but:

225/40 Front = 2.5 bar
255/35 Rear = 2.7 bar

I'm now on non-RFTs and prefer PSI, so after much experimentation I'm running them 34psi front and 36 psi rear.

Hope that helps?

Preferring PSI, as I do, or not, 2.5 bar is approximately 36 and 2.7 bar is 39.

I am aware the figures I quoted don't match.
The OP wanted to see the book figures and I then told him what my 'bum-ometer' ended up with on non-RFTs.
Either way it seems he is running lower pressures and the same front and rear.
Air is free so there's a cheap starting point.

[Silverstar]

Just looked at mine in the garage. Can't get a decent photo due to the light, but:

225/40 Front = 2.5 bar
255/35 Rear = 2.7 bar

I'm now on non-RFTs and prefer PSI, so after much experimentation I'm running them 34psi front and 36 psi rear.

Hope that helps?

I am pretty sure 18" should be 2.5 bars front and 3.0 bars rear, although I can't check the label right now as my car is in the garage.

[enuff_zed]

Just looked at mine in the garage. Can't get a decent photo due to the light, but:

225/40 Front = 2.5 bar
255/35 Rear = 2.7 bar

I'm now on non-RFTs and prefer PSI, so after much experimentation I'm running them 34psi front and 36 psi rear.

Hope that helps?

I am pretty sure 18" should be 2.5 bars front and 3.0 bars rear, although I can't check the label right now as my car is in the garage.

Well maybe you have a different label?
This is for a 64-plate 20i, so similar to the OPs.

[Silverstar]

Just looked at mine in the garage. Can't get a decent photo due to the light, but:

225/40 Front = 2.5 bar
255/35 Rear = 2.7 bar

I'm now on non-RFTs and prefer PSI, so after much experimentation I'm running them 34psi front and 36 psi rear.

Hope that helps?

I am pretty sure 18" should be 2.5 bars front and 3.0 bars rear, although I can't check the label right now as my car is in the garage.

Well maybe you have a different label?
This is for a 64-plate 20i, so similar to the OPs.

Ah didn't think of that, mine is a 30i

[enuff_zed]

I am pretty sure 18" should be 2.5 bars front and 3.0 bars rear, although I can't check the label right now as my car is in the garage.

Well maybe you have a different label?
This is for a 64-plate 20i, so similar to the OPs.

Ah didn't think of that, mine is a 30i

Keep up at the back.

[Silverstar]

Well maybe you have a different label?
This is for a 64-plate 20i, so similar to the OPs.

Ah didn't think of that, mine is a 30i

Keep up at the back.

[inkey$]

Before I commit to spending £500 on a new matching set of non-run flat tyres, I've booked the car in to my local Indy BMW workshop, Hallmark Autos of Maldon (any one know them?) on Monday. I've asked them to carry out a thorough inspection of the car, which should show up any hidden defects.

The dealer I bought it from, View Autos, did their own pre-sales check and an oil service, but I will feel happier with my own independent assessment.

Keep us all posted on how you get on

[jamesgarbett]

What;s the view on adjusting to slightly different tyre widths/profiles to OEM on 19" wheels? Any benefit/disadvantage?

[sars]

What;s the view on adjusting to slightly different tyre widths/profiles to OEM on 19" wheels? Any benefit/disadvantage?

That's a bigger can of worms than the RFT issue, there are many who have changed widths or profile for comfort, aesthetics or traction reasons. Just be aware you absolve liability from the manufacturer (BMW) and you become liable, if you go outside of what was homologated by the manufacturer. It is not necessarily illegal to do so, but your insurance could be voided if you do not declare any modifications.

[Silverstar]

What;s the view on adjusting to slightly different tyre widths/profiles to OEM on 19" wheels? Any benefit/disadvantage?

That's a bigger can of worms than the RFT issue, there are many who have changed widths or profile for comfort, aesthetics or traction reasons. Just be aware you absolve liability from the manufacturer (BMW) and you become liable, if you go outside of what was homologated by the manufacturer. It is not necessarily illegal to do so, but your insurance could be voided if you do not declare any modifications.

Amazing how much you can mod your car in the UK without any real headaches apart from informing your insurance company. Here almost all mods have to be homologated and pass a separate ITV (MOT) inspection for it to be legal, this can get quite expensive. Tyres have to be one of the sizes stipulated by the manufacturer any deviation and it won't pass the ITV.