Tank Slap - Motorcycle Forum

The BMW owners manual says 51 psi in the rear if 4 passengers but the max pressure on the tyre side wall issued by Bridgestone says 50 psi

The tyres are BMW specific for my car and are Bridgestone Potenza RE050A Rft.

51 psi seems very high and even though Bridgestone have made a BMW specific tyre it seems the two companies don't talk to each other and it's all pretty confusing for the end user.

Even if just 2 people in the car BMW recommended 48 psi in the rear Bridgestone.

Have you ever read Fear and Loathing in Las Vegas?

There's a great bit in there where they experiment with pressure in their tyres.

I would go with what Bridgestone recommend, it's their product.

I usually use 32psi F/R or 34F/38R with a full boot or 2 passengers, 42R with full boot and passengers/towing

Your pressures seem ridiculous to me

lol is 3 psi really going to make any difference

I may be completely wrong but won't the pressure increase as people get in the car? i.e. the pressure will go above the maximum anyway?

I would imagine 1 PSI either way will make little difference, honestly. Besides, they're only supposed to be used for getting to somewhere to get a proper tyre fitted again.

Hilarious, watching people drive around on them for weeks.

I think you're mixing up space savers and bmw run flats

51 psi does seem crazy!

Just Googled it and apparently due to the massively stiffer sidewalls on a run flat, a much higher pressure is needed to help the centre part of the tyre contact with the road.

DaytonAndy wrote:I think you're mixing up space savers and bmw run flats

You know, I did. Yes. Tee hee.

I would go with Bridgestone figure and seems the sensible decision however I have a question.

Bridgestone recommend one figure and it's 42 psi. But this doesn't take into account the specific car it's used on.

For example the pressure in our 318d recommends 36 psi in the rear for the same tyre our 330d recommends 51 psi. I agree a few psi won't make much difference but 15 psi will. The pressures quoted are for the same 255/30zr19 Bridgestone RE050A Rft.

Confused

That does seem strange, both definitely rear pressures? It makes sense for the front as you would expect the 330 engine to be much heavier than the 318 hence the higher pressure needed but the rear??? Hang on though surely they're different size tyres which would go some way to explain?

Andy I was quoting rear pressures for both the 318d and 330d with a 255/30ZR19 so the only variable I can see is the 330d overall vehicle weight is 250kg more but 15 psi for the same tyre seems a bug difference imo.

I dont think 15 psi is that big a difference when the car weighs 250kg more,thats a huge weight difference

I would not have guessed a 318 would have 255 cross section tyres in a million years! That's massive!

It's the msport Andy

I have gone for 40 front 45 rear and wll see how it feels and how the tyres wear.

Problem is the bigger the tyres the more they cost too!

I think most of the issue is wear at different psi s. Sadly you'll find out in a few thousand miles, but I think your right it's a very confusing set of advice.