Confused of Berkshire 19 Inch Non Run Flats

spantheman · Post by **spantheman** » Thu Mar 24, 2022 3:09 am

Recently sploshed out on a set of Goodyear F1 Assym 5 Non Run Flat 19inchers for my 2014 E89 20i.
Naturally want them to last a decade or 2 but confused re pressure discussions and debates. The door badge says 2.8 rear 2.3 front equating to 40 and 33 PSI respectively. I am veering towards some opinions that these are too high and I should reduce them...but to what and for what reason. Any friendly advice gratefully received

Colin_E · Post by **Colin_E** » Sat Mar 26, 2022 7:47 pm

I've been asking similar questions lately as I ditched my run-flats last weekend for Michelin Pilot Sport 4S. In my case I changed the rear profile a little too. Seems that some folk stick with the recommended (RF) pressures and others drop a little when moving to non-RF. Seems also that opinions get a bit entrenched

FWIW my take is that you're probably fine with 33psi at front. For rears I'd experiment but staying somewhere between 36-40;
a) What feels best to you for your style of driving etc.
b) Check wear over time.
c) Whilst I can't really vouch for this personally, I found a suggestion that a properly inflated tyre should increase pressure by 3-4psi from cold after an hour of driving. Could be nonsense - but might be worth a try?

I'm setting mine to 34F & 38R for now but its a work in progress. So far, ride feels great and ample grip. No comment (yet) about wear as its too soon.

Pondrew · Post by **Pondrew** » Mon Mar 28, 2022 7:26 pm

Always a fun discussion, tyre pressures.

My opinion (and it's my opinion) based on what I have learned:
Manufacturers post recommended tyre pressures based on the car set up from factory, not the tyres. The sticker is permanent, the tyres are not.
As long as the tyres you are using are able to take the pressure, then the manufacturer's pressures should be used irrespective of the tyre type or brand.
A few psi either way is not going to hurt cos unless you have a calibrated pressure gauge, your reading is a 'ball park' anyway.

For instance; I have a very cheap tyre compressor with a gauge. If I inflate to 40psi on this and then use a 'proper' calibrated gauge (which I used for work), the difference is about 5-15%, depending on which way the wind is blowing.

Personally I think having both tyres reading the same on an axle is far more important than the actual number of that reading.

spantheman · Post by **spantheman** » Sun Apr 03, 2022 12:59 pm

Thanks for the advice....its much appreciated ! Will keep a close eye on the wear... Cheers

tiglon · Post by **tiglon** » Sun Apr 03, 2022 2:25 pm

I don't think you'll ever find a definitive answer to this.

The sticker in the door is for the car and for tyres that are the same spec - i.e. run flats. They are delivering a car with a specific set of tyres and will recommend based on that. Once you change the spec it's your problem not theirs. I would expect BMW's opinion to be that if you change to non run flats then it's up to you to work out what's best and that they couldn't care less.

Mine are currently 35 and 37, for no particular scientific reason.

mcbutler · Post by **mcbutler** » Mon Apr 04, 2022 1:11 pm

Email the tyre maufacturers support dept - thats what I did when i swapped out my RF for PS4.
Tyre pressures are very important, its those four palm sized patches of rubber that keep you and those around you alive.
So ask an expert.......

Smartbear · Post by **Smartbear** » Mon Apr 04, 2022 3:02 pm

mcbutler wrote: ↑Mon Apr 04, 2022 1:11 pm Email the tyre maufacturers support dept - thats what I did when i swapped out my RF for PS4.
Tyre pressures are very important, its those four palm sized patches of rubber that keep you and those around you alive.
So ask an expert.......

What did they say to you?

Rob

N4LLY · Post by **N4LLY** » Mon Apr 04, 2022 4:38 pm

Smartbear wrote: ↑Mon Apr 04, 2022 3:02 pm
mcbutler wrote: ↑Mon Apr 04, 2022 1:11 pm Email the tyre maufacturers support dept - thats what I did when i swapped out my RF for PS4.
Tyre pressures are very important, its those four palm sized patches of rubber that keep you and those around you alive.
So ask an expert.......
What did they say to you?
Rob

I'd be interest to know also

tiglon · Post by **tiglon** » Mon Apr 04, 2022 4:54 pm

I would imagine they would say something like (taken from Michelin website):

The recommended tyre pressure for your vehicle is listed in the maintenance guide, displayed on a sticker on the inside front door (often passenger side) or even on the vehicles fuel cap.

BMW have thoroughly tested your vehicle with the OE tyres, so they are able to recommend tyre pressure for that. The tyre manufacturer has almost certainly not tested it's tyres on a vehicle for which completely different tyres are recommended, so I fail to see how they would be able to offer a recommendation on pressure or why they would even want to.

spantheman · Post by **spantheman** » Mon Apr 11, 2022 7:52 am

I must admit with the runflats inflated to the recommended for the non run flats the ride is harder than expected following the switch. I might adopt the non scientific 2-3 PSI reduction method and see ....?

Elmore · Post by **Elmore** » Wed May 04, 2022 12:20 pm

Hi y'all
did the switch from the run flats to normal tires, improve the ride enough to justify the change??I got 19" Bridgestones (like new) on my e89, and it rides like a covered wagon..
one tire seller suggested moving from a 255/30 to 265/30..and from 225 to 235/35 for a better ride..
anyone care to comment?

Smartbear · Post by **Smartbear** » Wed May 04, 2022 1:42 pm

Elmore wrote: ↑Wed May 04, 2022 12:20 pm Hi y'all
did the switch from the run flats to normal tires, improve the ride enough to justify the change??I got 19" Bridgestones (like new) on my e89, and it rides like a covered wagon..
one tire seller suggested moving from a 255/30 to 265/30..and from 225 to 235/35 for a better ride..
anyone care to comment?

I have those sizes on my e89 & the ride is a little better, though the biggest improvement comes from getting rid of the original runflat tyres even if sticking to the oem sizes.
Rob

B21 · Post by **B21** » Wed May 04, 2022 1:55 pm

The published on the door jamb for tyre pressure is the rated pressure at the rated continuous maximum speed..ie 155mph ish

You can reduce the pressures if you de-rate the continuous max speed of operation.

For ‘normal’ UK use most folks find something in the 32-36 front and 34-38 rear works for them

https://www.tyreleader.co.uk/tyres-advi ... e-to-speed

Refers

Busterboo · Post by **Busterboo** » Wed May 04, 2022 4:34 pm

B21 wrote: ↑Wed May 04, 2022 1:55 pm The published on the door jamb for tyre pressure is the rated pressure at the rated continuous maximum speed..ie 155mph ish

Where did you find that, please?

B21 · Post by **B21** » Wed May 04, 2022 5:12 pm

Busterboo wrote: ↑Wed May 04, 2022 4:34 pm
B21 wrote: ↑Wed May 04, 2022 1:55 pm The published on the door jamb for tyre pressure is the rated pressure at the rated continuous maximum speed..ie 155mph ish
Where did you find that, please?

I didn’t specifically…however type certification for products like cars and aircraft state that fluids, pressures etc. will be suitable for the maximum continuously rated speed / power

The required pressures for tyres increase with operating speed as per chart attached..

Z4-forum.com

Z4-forum.com