I have replaced all my run flats with conventional tyres, but retained the same sizes. I am not quite sure what pressure to put in them and I can't understand the numbers on the plate in the drivers door jamb. I was putting around 28psi into them but I have recently had a new tyre and found when checking all four that the fitter had put about 37psi into the new one. I have since placed 33psi in all four tyres, front and back. Advice gratefully received, thanks.

2013 3 Series M Sport hard top convertible, 320d auto.

Hi Martin

You say you have replaced your run-flats with conventional tyres. Presuming you didn't do this yourself, I'd like to think the tyre fitters inflated to the correct pressure according to the size, make and type. You say you were putting 28psi into them but was this to maintain the pressure, increase it or reduce it? 

The new tyre, is that the same make and tread pattern as those already fitted or different? It's not recommended to mix tyres of different tread patterns on the same axle.

37 psi is a lot different from the 28 psi you had before and if on the same axle, again could compromise safety.

Why now 33 psi on all 4? That seems an arbitrary figure and usually front and rear are different with higher on the rear than the front.

I would recommend you go back to wherever you bought the tyre(s) from and ask them for the recommended pressures. If they are a reputable supplier, they should be able to advise you correctly. If a back st supplier, they may not have the full technical knowledge in which case try an e-mail to the tyre manufacturer's technical department.

Hope this helps

John

 

Hi John

No, I didn't replace the tyres myself, it was done by a reputable tyre dealer in Nottingham called Lindleys (I don't use back street suppliers). When I have to replace tyres now I always make sure I use the same make and pattern - I am using Landsail tyres which are made in China but have a good reputation within the tyre trade. They are quite reasonably priced at around £80 per tyre and because I have seriously low profiles they are subjective to damage quite easily and do not require a bank loan to replace each time.

28psi was used purely out of ignorance (this was the pressure I used in my previous car, a Jaguar S Type) and when I checked all four recently, the last one to be replaced had 37psi in it - this was inflated by the fitter. I thought it was a bit high but also gave me the thought that 28psi was too low. As a compromise, again out of ignorance, I put 33psi in all four. This is what prompted my posting on this forum to see exactly what they need to be. I had a reply about 10 days ago now by another forum member Greydog (I mistakenly placed the same question in the Newbies forum too) who told me of a neighbour with the same car put 32psi in the rears and 36psi in the fronts - he had also replaced run flats with conventional tyres.

On that respect, I thought the 33psi I had in was a happy medium until I get chance to adjust the pressures at a garage - the rears are just 1psi to high and the fronts are just 3psi to low, nothing to be honest that is going to make a lot of difference. I will say that since I have put 33psi in all four, the ride has been much better.

Thanks for your posting.

Martin

Hi Martin

Greydog is very knowledgeable so I wouldn't dream of contradicting any of his advice. However, the Facebook BMW forum doesn't rate Landsail tyres at all.

It depends on your driving style and experience. For "normal" journeys, the Landsail is probably ok in terms of grip and wear. The difference comes if you try and use the capabilities of your car in terms of performance, cornering ability, braking performance etc etc. If you're pushing the boundaries, then the Landsail will fail early in terms of grip or wear or both.

Incorrect tyre pressures, whatever the make of tyre can also make the difference with wear and performance so it's as well to have them right rather than just an educated guess.

Happy (and safe) driving.

John