Today we had winter non runflat tires installed on our CMS A4.

Anyone have any ideas regarding what pressures we should be running for non-runflat tires? Of course the owners manual says nothing about this because Mini does not recommend non runflat tires.

A related question... We installed 225-50-18's instead of the OEM 225-45-18's. The new tires are load range 99, whereas the original tires were load range 91. Do I need to lower the pressure to offset the fact that the new tires are a higher load range? If I do not lower the pressure, will the new tires wear as if they were overinflated?

Thanks for your help in advance.

 

Bump. So for those of you who switched to non-run flats, what pressures are you running in your tires, and how are the tires wearing?

The tire dealer who installed our run flats merely filled them with the pressure noted on the sticker on the door jam. Thanks.

 

My winter non-RFT Michelin Primacy Alpin PA3s are running at the door jam pressures of 32 psi and I'm happy. They are stock 17 size. The installer pumped them up to 42 psi for some reason. I thought the RFTs were still on until I checked and adjusted 'em. Love the tires BTW, although not much in the way of snow here in the Philly burbs so far this winter.

 

35 lbs for P225/50ZR-17 Pirelli P Zero Nero All Season XL

Handles great and wearing properly.

32 is too soft... Run flats were to hard...
35 lbs is juuuust right

 

Thanks, I almost bought the PA3's, but assumed they would not be quite as good in severe weather conditions, which is the whole reason for my fine winter tires to begin with. I assume they are better handling tires on dry and wet roads, though.

 

Thanks, I am going to play around with the pressures a bit and see what happens. Thanks for the input.

 

on my cms all4, i have found that +5psi in front over the rears make a big difference, and the front bias weight distribution makes this seem reasonable

i used a borrowed tire pyrometer and chalk to set the pressures of the oem pirelli 225/45R18 p7 cinturato summer rfs to 42 psi frt / 37 psi rear

handling improved, ride improved, the tires are wearing evenly both front to rear and across the tread of each tire

if i bump the rears to 42, the rear breaks away easily and the car becomes an oversteering handful

on my dunlop 205/70R16 grandtrek sj6 studless ice and snow non-rfs, i ended up at 40 psi frt / 35 psi rear, at the stock 32 psi f/r, the car wallowed like an old cadillac

same results if i raise the rear pressure to 40 psi, massive oversteer

scott

 

I tried several different tire pressures to see what would happen.

Despite the larger size, The tire dealer who installed the tires had filled them to the same 32 pounds that the doorjamb sticker calls for for the OEM run flats. When I reduced the pressures to 28 pounds, it was immediately obvious that the tires had become too squishy. I was very surprised how much of a difference a decrease of only 4 pounds made. Perhaps it was noticeable because minis have such good steering feel.

I tried 38 pounds, and not surprisingly the ride was like I had reinstalled the run flats, although the bumps were not quite as jarring.

At 35 pounds, The bumps were a bit better, but it still felt like the run flats were on the car.

So with the tires that I have in a non-standard size, it seems like 32 pounds is the optimal compromise between ride quality and handling. But since I don't have a tire pyrometer like Scott does, I really don't know how the tires are going to wear long term.

Scott, I was going to try to reduce the pressure of the rear tires like you have, but I thought that might cause the TPMS System to think that there was a problem. I know in the R53 we used to have, that if a tire was under inflated by 5 pounds versus another tire the warning light would come on. Does anyone know if the TPMS system merely compares tires on the same axle, or if it compares front tires versus rear tires also?

 

i have run up to 10 psi difference front to rear with no objection from the tpms system ... just do a reset after you set the pressure you want

my guess is the computer "remembers" the set pressure of each tire individually

scott

 

I replaced my 225 45 18 91 v Goodyear Efficient Grip RFT tyres with 225 45 18 91w Dunlop Sportmaxx TT non RFT, does anyone know if any inflation pressure rate difference between them or not?

 

This thread now has me wondering - does anybody know where those numbers on the door sill come from? Are they merely dreamed up by the vehicle manufacturer or are they based on some collaboration between the tire manufacturer and the vehicle manufacturer?

I don't know if it's still the case, but there was a time when MINI was fitting tires from multiple manufacturers (Bridgestone and Pirellis I think) depending on whether or not you got performance or all-season tires. Were the sill labels different depending on the tire? Are the labels the same regardless of the size of the tire fitted? Or are they same across the entire model lineup?

In all honesty this is something I never thought about before - I just filled to the sill label and moved on....

 

I just swapped the run flats out to the Michelin Pilot Super Sport 225/45/18.

What's the optimum pressure? I started with 34psi, it seems to be a bit too soft and wobbly, I now have it at 35psi, almost perfect. I'll up a notch to 36psi.

As I think I'm used to the run flats and the hard side walls? btw I have the sports suspension as well

 

i used a tire pyrometer to set my tire pressures

2012 cms all4, 225/45R18 pirelli p7 summer run-flats

ended up at 42 psi front and 35 psi rear, but the car had more understeer than i like so i added first 1 psi then 2 psi to the rears and have nice neutral handling

same process on my winters, 205/70R16 dunlop grandtrek sj6 studless snow and ice tires non-rfs, ended up at 40 psi front and 35 psi rear

i seldom have bodies in the back seats so i expect a pressure differential front to rear due to weight distribution

i am seeing even tire wear, both across each tires tread and front to rear using the different front and rear pressures

a note on tire pressures and handling, my racer buddies will adjust pressure in 1/2 psi increments to address under/oversteer after getting a basic pressure using the pyrometer

scott