Winter Tyres and Aftermarket Wheels

[whiskyguy]

Almost two weeks into 992 Targa GTS ownership and loving it so far!

Looking ahead to the colder months I'm keen to put winter tyres on. At the same time I'd like to buy a new set of wheels either for summer, or winter so I have two full sets of wheels/tyres that can easily be swapped around. I've done this with previous cars I'll keep long term and it works well.

Current thinking is that I'd like to use the Satin Black Spyder wheels the car came with (standard 5 bolt fitting) with the winter tyres and buy a new set of wheels to put the summer tyres on. The summer wheels will almost certainly need to be custom made (a shame the BBS e88 only come in 18" and 19" as I love that look!) so it should be fairly easy to match up with the Pirelli Pzero rubber the car was supplied with, but are there any issues with putting winter tyres on the Spyders? I ask this because the manual specifies a slightly smaller wheel on the rear for winter tyres...

Summer:
Front: 245/35/R20(91Y)
Rear: 305/30/R21(100Y)

Winter:
Front: 245/35/R20(91V) or 245/35/R20(95V) XL
Rear: 295/30/R21(98V) or 295/30/R21(102V) XL

I'm assuming that given the wheel sizes are consistent across summer and winter (20" 8.5j/21" 11.5j) I'll be able to put the narrower rear tyres on the spyders ok, but it would be good to confirm. Given there is a 10mm difference between recommended summer and winter rubber will this leave a slight gap on the edge of the rim?

Also would be very interested to hear from anyone that has run winter tyres on your 992 and what you'd recommend. Looks like the most used is the Michelin Pilot Alpin which seems to be available in a Porsche specific version. Again would be good to know if this makes any tangible difference. Unfortunately I'm quite clueless in terms of what is possible/good idea as far as wheel/tyre sizing is concerned.

Thanks
WG

 

[lowndes]

Apologies for the delay in replying, I don’t find myself in these parts much these days.

You don’t say specifically why you need winter tyres, definition of a winter tyre being one with the three peak mountain snowflake symbol. Is it for cold (below 7°C) or snow or both?

The reason why this is relevant is linked to the current Porsche design philosophy of large wheels with low aspect ratio tyres. The large wheels are partly for aesthetics but also to provide clearance to the brake disks and calipers, not to say offering enhanced bragging rights in the pub carpark.

If winter driving is mainly on cold wet roads then the wheel size may be less of an issue. If on the other hand you need to deal with Alpine conditions including mountainous terrain and uncompacted snow then wheel size is relevant .

Porsche do partially recognise this and in some cases offer either smaller diameter wheels or a narrower wheel and winter tyre. However, the reduction in wheel size is limited by the need to fit over the brakes. The result is that even the £6k Porsche approved wheel/winter tyre combination specifically designed for the turbo S did not work in the real world. In deep uncompacted snow the wide tyres simply "snowplaned” down any camber or crossfall and made the descent of a steep Alpine pass difficult to say the least. The set I have is as below and I found them not up to the task.

20-/21-inch 911 Turbo S winter wheel-and-tyre set
Forged alloy wheels with a five-double-spoke design in a two-tone finish and with central lock. Painted Black with bright-polished frontal area.
Front axle: 8.5 J x 20 RO 40 with 245/35 R20 95V XL tyres,
Rear axle: 11 J x 21 RO 66 with 305/30 R21 104V XL tyres.

I see from the website that Porsche are sticking with the 21” winter wheel for Carrera. The reduction to 295 may help a little but I wouldn’t bank on it.

 

[whiskyguy]

Thanks for the response.

I have actually gone ahead and ordered Continental Winter Contacts to fit on the RS Spyder wheels and will aim to get some other wheels for summer use - probably retro old skool style!

I'm based in Scotland and whilst we do get some heavy snow some years mostly its just cold and wet, therefore the benefit of winter tyres is for improved performance in cold/wet conditions that may include some snow from time to time. I very much doubt I'll choose to drive the 911 on days when we have deep uncompacted snow - the height clearance would exclude that option anyway.

I've had numerous cars now for which I've purchased a winter set and the benefits have been very tangible. You also get to change the appearance of the car for a new season!

WG