Tyre pressure non run flat

peter2704

Member
I’m 225 /35/18 front and 255/35/18 rear what tyres pressures do people recommend ? Touring wales next week so need correct pressures
 
peter2704 said:
I’m 225 /35/18 front and 255/35/18 rear what tyres pressures do people recommend ? Touring wales next week so need correct pressures

To my mind the pressure is the pressure regardless of the whether run flats or not since the primary function of the air in tyres is support the load of the car which remains a constant. I'm also running standard tyres but I have stuck to the BMW recommended pressures.
 
Whose tyres have you got front and back?

Most folks run 32-36 front and 34-38 rear ..

I use 32/34

Higher pressures on the OE run flats were related to speed and load ratings..
 
To be honest I think they are cheap tyres on the car when bought , I had accéléra ph1-R on my last car and they seemed ok for the price so may fit them to the 19” alloys
 
Fady said:
To my mind the pressure is the pressure regardless of the whether run flats or not since the primary function of the air in tyres is support the load of the car which remains a constant. I'm also running standard tyres but I have stuck to the BMW recommended pressures.
This./\
Pressures should only be changed for different internal volumes of tyres IMO, not whether they are RFTs or not.
As said, the bit of air inside the tyres supports the whole weight of the car. The manufacturer went to great lengths (presumably) to determine what those should be for a given volume of space inside the tyres.

Why anyone would decide they know better is a strange phenomenon exclusive to car forums IME.

Always makes me laugh when the 'forum experts' ask what make of tyre you have. It makes sod-all difference.
 
Pondrew said:
Fady said:
To my mind the pressure is the pressure regardless of the whether run flats or not since the primary function of the air in tyres is support the load of the car which remains a constant. I'm also running standard tyres but I have stuck to the BMW recommended pressures.
This./\
Pressures should only be changed for different internal volumes of tyres IMO, not whether they are RFTs or not.
As said, the bit of air inside the tyres supports the whole weight of the car. The manufacturer went to great lengths (presumably) to determine what those should be for a given volume of space inside the tyres.

Why anyone would decide they know better is a strange phenomenon exclusive to car forums IME.

Always makes me laugh when the 'forum experts' ask what make of tyre you have. It makes sod-all difference.
That would’ve been true if all tyre brands and models were built with the same materials and specs. But they vary. And so do road conditions and driving styles.
 
I ran my first set of rear nonrft at recommended 42 psi.
The rear would skip bumps and later with wheel off i could see the crown of the tyre wearing more than the edge.
Now run 40psi rear and get even wear.
Same at the front use 40psi get even wear which to me it means the load is spread even across the tyre.
Theses tyres are GY asym 5 now.
Just experiment.
 
peter2704 said:
To be honest I think they are cheap tyres on the car when bought , I had accéléra ph1-R on my last car and they seemed ok for the price so may fit them to the 19” alloys
The tyre market is very competitive, so you get what you pay for.

My experience of cheap tyres is that they were ... er ... cheap tyres. :)
 
peter2704 said:
wont the engine of the car make a difference,mines the N52 6cyl which i presume weighs more than the 4 cyl
And 35i even heavier.

It's the reason you have to experiment.
 
peter2704 said:
wont the engine of the car make a difference,mines the N52 6cyl which i presume weighs more than the 4 cyl

Suggested pressures as shown on the sticker on the door jamb will likely vary depending on the model!
 
flybobbie said:
peter2704 said:
wont the engine of the car make a difference,mines the N52 6cyl which i presume weighs more than the 4 cyl
And 35i even heavier.

It's the reason you have to experiment.
Exactly , some complete ballaux posted in this thread :cry: why would any end user assume the big names have every corner covered , their mistakes small or large are legendary & even worse repetitive .
Don't be a sheep following the herd , there are alternative tyres, tyre pressures , oil brands & possibly the biggest insult to a car owners intelligence :evil: alternative service regimes than they stipulate as fact .
 
mr wilks said:
Exactly , some complete ballaux posted in this thread :cry: why would any end user assume the big names have every corner covered , their mistakes small or large are legendary & even worse repetitive .
Don't be a sheep following the herd , there are alternative tyres, tyre pressures , oil brands & possibly the biggest insult to a car owners intelligence :evil: alternative service regimes than they stipulate as fact .
So, there's your choice, fellow Z4 owners: follow BMW or mr wilks. Easy, really.
 
Like the light aircraft we fly.
Aircraft were designed around 1950's technology with tyres made in the 70's.
Tyre pressures quoted in manual.
Modern tyres have different ply ratings and manufacturers, probably due liability and original certification, offer no new tyre pressures.
So we run probably 10 psi more than old manual figures.
The old tyre pressures the tyres look well deflated.
 
Busterboo said:
mr wilks said:
Exactly , some complete ballaux posted in this thread :cry: why would any end user assume the big names have every corner covered , their mistakes small or large are legendary & even worse repetitive .
Don't be a sheep following the herd , there are alternative tyres, tyre pressures , oil brands & possibly the biggest insult to a car owners intelligence :evil: alternative service regimes than they stipulate as fact .
So, there's your choice, fellow Z4 owners: follow BMW or mr wilks. Easy, really.

:oops: if the big names never made mistakes I'd follow your thought process but as anyone with the slightest interest in cars ( & particular germanic ones) should know is that unfortunately for the end user we don't always get faultfree or even flawfree cars .

Tyre sizes are a perfect example of a mistake finally acknowledged & rectified.
Through the 90s to 2020s Bmw persisted with 30 + 35 profile + RFTs on 19s whilst MB & Audi did not .
Now Bmw have upped their profiles like their rivals , why didn't the rivals change theirs to what Bmw were fitting ? :wink:
You're a salesmans dream Mr Bb
 
I had to laugh at this thread :) thanks all.

Tyre pressure for run flats / non run flats isn't the same - even the manufacturers keep changing their minds!

Tyre construction plays a big part, and in the early days of run flats (which is what your label in the door jam is using) were nonsense & soon revised in later years. Of course your sticker doesn't change just because the manufacturer figured things out better after the fact.

If you need proof, there are some cars available that have run flats fitted to the base level cars, and non run flats fitted to the performance option (look at the 2 series BMW 220 vs m240i for example). The tyres have different psi values.

Most people go with the knowledge gained from a large group of users testing this out (from another forum) & combine that with the shift in attitude from BMW on more recent cars - which is on 19" rims at 38 psi rear, 34psi front.

I only paid attention to the 19" rim pressures as that is what I have :)
 
matsmith749 said:
If you need proof, there are some cars available that have run flats fitted to the base level cars, and non run flats fitted to the performance option (look at the 2 series BMW 220 vs m240i for example). The tyres have different psi values.
Your theory here will only work if the 2 models have the same tyre sizes.
 
Back
Top Bottom