Wheel size confusion

Wheel size confusion

Author
Discussion

Technomad

Original Poster:

753 posts

162 months

Tuesday 9th October 2012
quotequote all
I'm looking for a set of winter wheels for my 997.2 C2S. Standard wheel sizes are 8J19 ET57 front/11J19 ET67 rear and I'd prefer to stick with 19" wheels rather than drop to 18" What's confusing me is the suitability of e.g. BBS CH-Rs, which are 8.5" at the front and with offsets of ET51/56 (f/r). I'd have thought that the offset should be pretty damn consistent between wheels for a given model (although I note that Porsche themselves aren't consistent on this). So thoughts and advice on the CH-Rs versus getting a (slightly boring) set of OEM winter wheels/tyres?

Richard

_gez_

1,013 posts

193 months

Wednesday 10th October 2012
quotequote all

Standard wheel sizes are 8J19 ET57 front/11J19 ET67


BBS CH-Rs, which are 8.5" at the front and with offsets of ET51/56 (f/r)



So, fronts will stick out 6mm + 6mm = 12mm further (6mm from the offset, 6mm from half of the half-inch). Probably okay but I wouldn't be 100%.

Rears will stick out 11mm further. On my 996 turbo that would be fine (I use 15mm spacers on the rear) but again we be better to check.

Having said all that it does sound wasteful for winter tyres. If it was me I get some second hand 18" wheels for winter tyres - you will probably have more choice of tyre and they will be significantly cheaper.

Edited by _gez_ on Wednesday 10th October 23:03

BnB

1,059 posts

174 months

Wednesday 10th October 2012
quotequote all
Why shell out for four wheels?

I just keep a spare set of tyres at the OPC and they swap them twice a year. My wife keeps her winter set in the garage and the local mobile fitter visits in November and March to make the swap.

It costs £10 a corner be it OPC or local grease monkey. That's a lot of tyre swaps before a spare set of wheels has been paid for (not to mention your own labour time cost).

Technomad

Original Poster:

753 posts

162 months

Thursday 11th October 2012
quotequote all
As I live 70 miles from the nearest OPC and mobile tyre fitters don't come out here (I've tried) I prefer to keep winter wheels for all our cars and have them swapped over by the local garage - I don't like the idea of having too many tyres swaps done given the potential for damage to the wheels. My other concern about the OEM 18" winters is that they're notably narrower at the rear (265 vs 295) so on those not infrequent winter days when a good blast is entirely possible, I'd find grip limited by the narrower tyres (something I've found with my 123D)

MrTickle

1,825 posts

238 months

Thursday 11th October 2012
quotequote all
Standard wheel sizes are 8J19 ET57 front/11J19 ET67

BBS CH-Rs, which are 8.5" at the front and with offsets of ET51

Surely if a wheel is 12mm wider, but the offset is 6mm less the outer edge of the wheel will be the same???

_gez_

1,013 posts

193 months

Thursday 11th October 2012
quotequote all
MrTickle said:
Standard wheel sizes are 8J19 ET57 front/11J19 ET67

BBS CH-Rs, which are 8.5" at the front and with offsets of ET51

Surely if a wheel is 12mm wider, but the offset is 6mm less the outer edge of the wheel will be the same???
Have a look at this link which should help with understanding. Smaller ET means wheel sticks out more.

http://www.1010tires.com/WheelOffsetCalculator.asp

MrTickle

1,825 posts

238 months

Thursday 11th October 2012
quotequote all
_gez_ said:
Have a look at this link which should help with understanding. Smaller ET means wheel sticks out more.

http://www.1010tires.com/WheelOffsetCalculator.asp
me being back to front again hehe