Winter tyre pressures

Morning,

Well, a week ago I had my winter tyres fitted - I had to employ a mate to change the wheels over as with my left hand out of action I couldn't do it myself. I would normally change them around early November.

According to the sticker on the B pillar I set the pressures to 2.8 bar front and 3.0 rear, didn't drive the car much over the weekend, drove the car this week in the near freezing temperatures and I found the car absolutely shocking to drive

It really felt like I was heading for the nearest ditch, the steering felt incredibly light - even in Sport mode. I tried it in comfort but while it was still light there was less feedback so kept it in sport for that reason. Honestly it really felt unsafe and I ended up driving everywhere a lot slower than even the driving conditions would dictate. I could feel every surface imperfection most likely due to the tyres being runflat and the tyre pressure.

Last night I dropped the pressures to 2.4 front and 2.6 rear in anticipation of a short drive over some back roads. What a transformation! Steering felt like it did when I had my summers on, it wasn't perfect - the runflats occasionally appearing to tramline, however it felt much more glued to the road and minor surface imperfections were absorbed with ease.

The outdoor temperature last night was milder than earlier in the week so I'l have to wait and see how it behaves in colder conditions.

What pressures are you running? For reference my tyres are Pirelli Sottozero 95V M+S XL 225/45r18 on a square setup with approx 5mm tread all round.

 

Those are exactly the same winter tyres on my F30. The specified pressure (door pillar) do seem to be very high, but I must admit I've never felt that the handling was that unpredictable. But they do seem to handle slightly better when the pressures have dropped slightly so I do run them at least 0.2 Barg lower. In comparison the summer P Zero's on 19 inch wheels are so much sharper with better feedback. I'm always glad to get the winters off the car come spring time.

 

I think I'll be glad to get back to the summers too Mike. I have Hankooks and while they grip well they wear quicker than the Goodyears I had on my previous car so come next winter my summers will be getting new tyres.

 

Those posted pressures do seem high for normal running. At first, I thought it could be because the tyres are new... but reading on... see they are part worn, so should be more stable. My experience, run-flats run at 'optimum' performance in a very tight pressure window, get it wrong (high or low) and ride/handling deteriorates.

I run 2.4 - 2.45bar front and 2.6 - 2.65bar, on my 535i, for my 17" winter run-flats, the same setting pressures as my 18" summer set. I run a bit higher than the door plate (lower) figures, as those pressures are too low for optimum performance. I find the winter run-flats perform well, much more confident in cooler conditions and the ride is sweet. As the tread wears down a bit, the ride/handling balance is better than at full tread. Not surprising, as there is less tread block movement when pushing on.

I will be tempted to run my winter set well into next spring, (or until down to ~3mm), as they are on their last winter use, (above 4mm). Get into summer temperatures before moving to the summer set.

Peter

 

The Pirelli Sottozero tyres came with the winter wheels that I bought 12 months ago. They do feel somewhat vague with little feedback compared to the P Zero's. I've never had winter tyres before, but succumbed to all the posts by others insisting that winters are essential, and when the set of nice BMW 18" Turbine alloys came up at a reasonable price I bought them. Given the limited mileage I do in bad winter weather I'm wondering whether I do need the winters? I've had no problems in the past with the xDrive on light snow / ice on the summer tyres. I'll get this winter out of the Pirelli Sottozero's before they need replacing. What other brand type of winter tyre would others recommend that might perform better?

 

I'm currently on Dunlop Winter Sport 3D. I'll be tempted to go with the Continental Winter Contact TS 850/860 series, next time. Or similar. I've used Vredestein Wintrac Xtreme on the 3-series, a superb winter tyre for our type of climate.

Peter

 

I had the Wintrac Extreme on my e91 and they were good for about 4 winters before they perished with age (and unfavourable storage conditions ) Didn't notice the same issues with them as I do with the current Pirellis. In fact I always remember solidly ploughing up a snowy hill with no issues where the 4x4 in front of me was all over the place!

Also agree about the optimum pressure being in a narrower range than compared to non runflats.

Next year I might go for the Goodyear Ultragrip, they seem to get good reviews.

 

3 bar does sound high. Is the summer set a square setup or staggered?

 

Same winter set up as you, have always run 2.4 front 2.6 rear with no issues.

Kindest Regards
Carl.

 

They're staggered Ed.

Here are the pressures on the door plate:

 

Looks very much to me that the pressure settings are for load carrying capacity, on the XL tyres. Haven't done the tyre/axle load math, but at first sight definitely looks that way. I note the normal tyres (including the 94 H M&S) show 2.4bar front and rear.

Peter

 

That's the same door plate on my F30 xDrive

 

The pressures specified are for all winter conditions, and I do wonder whether these high pressures are for heavy snowfall, rather than just the chilly weather we get here in the UK. But I agree with @bishbosh - slightly lower pressures do give better handling.

 

I check my tyre pressures regularly but I do find that the pressures vary quite considerably depending on where I check them . For example , if I check them at my local Tesco then go to my local Esso Garage and check them again I find a few Lbs pressure difference . Sometimes it s the calibration of the Air Pressure Machine that s at fault .

 

Air points at garage forecourts always seem to vary. I have my own compressor and gauge which I know is accurate (checked at local tyre supplier)

 

The car will flash up a dash warning and iDrive screen [just in case you don't hear that alarming 'Bong' that accompanies, even the low outside temps warning].if it detects pressure differences, even a pound or two, at least mine does.

Nearly stops my heart if it sounds when I'm on the move!!

 

A 'Must Have' accessory for the Porker owners on here?

I've just purchased one - Christmas present to self. I can't resist shiny car accessories.
Now just need the car to go with it. Thanks @Singvogel .

And if you want to save a few quid, it's available from this UK Porsche specialist (postage free).

https://www.9apart.co.uk/product-page/genuine-porsche-classic-tyre-pressure-gauge

 

I use the digital gauge on a Ring tyre inflator. It's about 0.05 to 0.1bar out compared to what the tpms sensors read.

 

The TPMS sensors on my car read about 0.1 Bar low. So when I've inflated to 2.6 Bg. they all read 2.5 on the iDrive.