Pressures for winter tyres

[jhrfc]

I've just had some continental winter tyres fitted to my 18 wheels. (winter contact ts 810 Sport).

I assume they should be run at the same pressures as the standard tyres?
The fitters seem to see fit to put in nearly 3 bar! that's got to be wrong right? standard pressures inside the door say 2.1 rear 2.0 front, which is what i have set them at. (obviously re-checking as the temp drops).
Cheers
Jon

 

[Buddy]

Jon, I'd say you're right to use std pressures and as you say, check as temps change, it makes such a difference. It's what I intend when I fit mine. 3bar was probably the max pressure the tyre is intended to stand so you've done right to drop the pressures.[] Std pressures are all that are mentioned in the driver's manual and nothing different there concerning winter tyres.

 

[jhrfc]

thanks.

 

[Richard_Hamilton]

I think standard pressures for 18" are 2.0bar front and 2.5 rear. Did you try 3T?

 

[jhrfc]

hmm what year is the table for? the panel on the door definitely says 2.0 F 2.1 rear for 18" on my 2011 2.9 car. maybe 3.4s are higher at the rear? alhtough don't see why, more air not more metal! 3t still haven't rung me back despite a couple of messages. I'll try them again though as he was on holiday last week so may be catching up. plus arranging to get the tyres to and from a workshop is a right pain! Cheers Jon

 

[chrisH]

I believe that table is for the GEN I as GEN II TP's are lower as it has a diffent suspension set up, mine on 19ins are 2.2 Front and 2.3 Rear. Why not ask your tyre dealer who fitted them to contact Continental about it as winter tyres may run at different pressures to ordinary tyres?

 

[jhrfc]

I didn't buy the tyres form the dealer so i doubt they'll have any idea. (esp as they stuck 3 bar in!) I'll break the habit of a lifetime and read the manual [] Failing that i'll ring the OPC at Reading. Cheers Jon

 

[Motorhead]

Jon, I'd be inclined to stick with the recommended pressures given on the door panel and in your driver's handbook. And if you're really concerned, you need to make a pressure correction for ambient temperature too: http://alflash.com.ua/acadia/L-SB-0154-08Compensation%20and%20Adjustment.pdf [P1/T1 = P2/T2 where P and T are absolute pressures and temperatures, ie gauge pressure+1 bar and ambient temperature (deg C)+273] Jeff

 

[Richard_Hamilton]

ORIGINAL: jhrfc hmm what year is the table for? the panel on the door definitely says 2.0 F 2.1 rear for 18" on my 2011 2.9 car.

Oops! The table is for Gen 1. I didn't realise yours was a Gen 2.

ORIGINAL: jhrfc 3t still haven't rung me back despite a couple of messages. I'll try them again though as he was on holiday last week so may be catching up.

Keep trying, as he gets very busy.

 

[Buddy]

Concerning Winter Tyre Pressures, I fitted mine last week and the label in the door opening said 2.0fr 30psi and 2.5Rr 37psi of course conversions vary in their translations as 1Bar is nominally 14.7psi and tyre gauges don't generally go to decimal places. I've now added tyre pressures to the winter tyre post in FAQ's Gen1 & 2 I did go through driver's manuals for Gen1 & 2 and there was no difference in pressures for summer or winter tyres but I have noticed in the past that temps can vary the pressures by a sizeable margin, I presume due to volume since our tyres are greater in volume than some.

 

[Motorhead]

FYI Kevan, for 19" wheels the Gen 2 Driver's Manual gives the front/rear tyre pressures for cold tyres as 2.2 bar (32psi) and 2.3 bar (34psi) respectively; presumably at 20 degC. Perhaps you could add this information to the Cayman FAQs as many of us have the bigger wheels fitted. I'm sure that someone else can give you the pressures for the Gen 1 car on 19" wheels. Incidentally, if you use the formula I gave earlier in this post (for a constant volume), these pressures drop to 2.0 bar and 2.1 bar when temperatures fall to zero, so all the more reason to keep an eye on your pressures at the moment. Jeff

 

[Buddy]

So Jeff, are you saying that if we have a Gen 2 we should set our pressures at 2Bar and 2.1Bar at 0C? Personally I'd say to use the std pressures at any ambient temp. In summer on my 19" Tyres I have noticed greater pressure increases if left too long as temps rise. Anyway, as Porsche only approve 18" winter tyres for the Caymans that was what was listed but I have now added the 19" pressures which apply to std summer tyres Gen1 & Gen2.

 

[Motorhead]

ORIGINAL: Buddy So Jeff, are you saying that if we have a Gen 2 we should set our pressures at 2Bar and 2.1Bar at 0C? Personally I'd say to use the std pressures at any ambient temp.

No Kevan, I've always believed that you should go with the recommended pressures regardless of the ambient temperature, like you say. I was merely pointing out that there's a small but significant pressure change with temperature, as you've noted from your summer observations. The Tyre Pressure Chart given in the pdf referred to in my earlier post makes interesting reading since it shows how the tyre pressure changes from cold tyres to warm to hot tyres, about 4psi in the example given, emphasising the importance of measuring tyre temperatures before a drive. Jeff