Winter Tyre Sizing

Statler

Old enough to know better
I've a set of 225/45 R17 winter tyres on 17" rims. I had the tyres on the BMW for the last couple of winters and they're still in good shape.

I was comparing them with the 19's and thought the diameter was a bit small so I checked it out on one of the tyre sizing sites and the difference in diameter is roughly -4% - smaller in other words

Audi use 225/50x17 on the base and Se spec A5 which have almost the same diameter as the 19" summer tyres.

So, will it be ok to run these as on the A5 or will the -4% difference in diameter have a really noticible affect on speed reading and mileage, gearing etc to the point that I shouldn't use them?

TIA
 

Ian_H

Registered User
This website will give you the complete details on the impact of different tyres ... which for your setup will mean your speedo will over-read by about 2mph at 60.
Over-reading is safer than under-reading of course... The smaller diameter winter tyres will reduce your ride height by about 1cm.
See here
 

Statler

Old enough to know better
Ian, thanks for that, very useful site :)
 

Statler

Old enough to know better
Yeah it is. With winter tyres it'll be unstoppable :)
 

Sc08 LAB

Registered User
You seriously don't need to waste any money on winter tyres, I drove to France last Christmas to Meribel, I used Michelin super sports and they had about 4mm of tread left.

Around snowy mountain roads they were perfect and I was being a little silly testing the Quattro. After leaving it for five days and on a non gritted road on the highest road I drove out no problem. You will not need winter tyres, I won't be buying any and I live here too. Please save your money and spend it on mods.
 

Statler

Old enough to know better
Lol, I like your thinking.
I have the tyres already, been running them for the last three winters so no expenditure. They're a smidge too small but will do if I'm really stuck. Guaranteed that this will be the warmest winter on record ;)
 

5CYL

Registered User
You seriously don't need to waste any money on winter tyres, I drove to France last Christmas to Meribel, I used Michelin super sports and they had about 4mm of tread left.

Around snowy mountain roads they were perfect and I was being a little silly testing the Quattro. After leaving it for five days and on a non gritted road on the highest road I drove out no problem. You will not need winter tyres, I won't be buying any and I live here too. Please save your money and spend it on mods.

Traction with quattro is all well and good but how about braking on snow with "about 4mm of tread left" you didn't mention braking. Were you to say that braking on snow with "about 4mm of tread left" was as effective as using a winter tyre then I'd seriously wonder about that "silly testing" you mention. If all you say is true it really is a wonder that in Germany, at least, the fitting of a 'winter' tyre is a legal requirement, but then you didn't venture into Germany, stayed in France.

I fit winter tyres here in the UK, I have to brake going down snow covered hills, and with winter tyres, it's a lot easier getting back up 'em, too.
 

Shrek5

Registered User
I would also argue you don't *need* winter tyres (at least for typical Berkshire weather - not sure how NI compares), during the snows of previous years even on 20's the quattro has been more than capable of getting moving. With regards to stopping - as @5CYL says they won't be any more effective than any other car on the road, and certainly not a patch on winter tyres.

In my experience driving to the conditions has been all that's required and it has coped with hills and slopes just fine. That said I have the luxury of looking out the window and if it's really bad just staying indoors and working from home, if my job depended on it then I'd probably consider winters. If I was going to Meribel I'd definitely have a set! ;)
 

Sc08 LAB

Registered User
Traction with quattro is all well and good but how about braking on snow with "about 4mm of tread left" you didn't mention braking. Were you to say that braking on snow with "about 4mm of tread left" was as effective as using a winter tyre then I'd seriously wonder about that "silly testing" you mention. If all you say is true it really is a wonder that in Germany, at least, the fitting of a 'winter' tyre is a legal requirement, but then you didn't venture into Germany, stayed in France.

I fit winter tyres here in the UK, I have to brake going down snow covered hills, and with winter tyres, it's a lot easier getting back up 'em, too.
I was being 'silly' in safe places and it's my first Quattro, I used to live in Germany and yes over there they make them a legal requirement for many reasons, not least because they don't pay road tax, therefore it's not the government's responsibility to grit certain roads.

Breaking was fine on the snow (after a big dump of powder before we left), the car was full to the brim so the extra weight helped a little, however on those roads I was a careful driver, when the roads were 'sloshy' the tyres were great.

Again I do stands by this and I won't be buying any.even if I went to Germany for a week our two I wouldn't as its a legal requirement for inhabitants, just like driving through France it's not a legal requirement to have a breathalyzer, if you're not an inhabitant.

Hope this helps and see you soon I hope mate @ statler.
 

Shrek5

Registered User
I thought that you had to carry a breathalyser even if you weren't an inhabitant of France. I thought I'd check that and it looks like, technically, you do but the law has been rendered unenforceable (by a fine at least), see here and here.
 

Sc08 LAB

Registered User
No out does say you need one but it's not a legal requirement and you can't get fined if you're not a French inhabitant. You can only buy them for €7 in any fuel station but I'll find the info when I get the time.
 
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