What is the largest/tallest tyre that will fit on the B7?

[Oatmeal]

Really odd question, but what is the tallest tyre size that will fit on a B7?

General background:
2007 A4 B7 1.8T Quattro SE

Had the standard 17 inch wheels, replaced with dual pcd 18's so I could use the same wheels for my Subaru and my Audi. Subaru has since been sold.

They're Audi TT style wheels?

I chucked on a set of Bridgestone Potenza Sport 225/40/R18, you know... the cheapest 18" tyre size haha

My Subaru never used to tramline as hard as this Audi does and someone suggested it would be because the tyres are wider than the Subaru. Subaru running 215/45/R18's compared to the 235/45/R17's on the Audi originally.

This Audi rim is wider than the Subaru's, so I don't see myself getting away with 215's really. Not without being forced to entertain wheel damage from my dismal parallel parking. Where I live there is always parking spaces, don't judge me

So, in following the same logic or line of reasoning that a thinner tyre won't tramline as hard as a wider one, would a taller tyre not provide the same characteristic or would it actually be measurably worse?

With this, am I being a fool for wanting to buy a 225/45/R18 tyre for these 18" rims?

Somewhat hoping that the added benefits of:
-Less likely to damage my rims with my sh*t parallel parking skills... (Comes up often enough to be a chore but not often enough to actually improve at it)
-Less likely to tramline?
-Hopefully more comfortable than the lower profile tyres
-Hopefully less noisy in the cabin than the lower profile tyres

Not sure about everyone elses experience but I've never felt overly confident with the handling of the Audi compared to the Subaru, feels less predictable. I don't think I'll be missing out much on the handling drawbacks of a taller tyre.

With all of this blathering on, what is the tallest tyre I could comfortably fit on my B7?

TLR
I do a lot of motorway driving and this car tramlines like a b*tch. Had the suspension checked out and it all checks out, presume it's just an Audi thing?

Is a 225/45/R18 a feasible idea?

My current tyres are on 2mm and I'm looking to replace them soonish, currently looking at the Potenza Sports just really not sure what size to get or if it even makes enough of a difference to be worth the difference in cost?

 

[Charlie Farley]

There is no quick answer to be honest.
If one works around the s-line option on a B7 , they will be an 8j rim 18" dia and offset around ET43 , factory tire fitment on that rim is 235/40 18" .
this is a good compromise as its middle ground .
17" come with a taller side wall profile but overall diameter will still be around the same.
19" go 235/35 19" so a bit lower than 18" but over diameter stays the same.
You want to stay as close to factory spec with regards to overall dia of the wheel/tyre when fitted, how you get to the point is down to you.
If you are not up to speed with tyre profile/width ratios then maybe look at a guide that offers the specific info you need , something like , "will they fit" .
235/40 18 are fine on motorways etc , dont forget, not all tyres are the same in terms of road noise etc, some are quiet and some are not.
suspension damping quality and ride height are also a big factor on B7's , there is no one quick fix I'm afraid and most experiment to get the end result they prefer.

 

[Oatmeal]

Looking at the Tyre size calculator, I see that the stock wheels (235/45/R17) I had fitted have a diameter of: 25.3"
The ones I propose (225/45/R18) are about .7" taller @ 26"
Nothing hugely significant, but enough to worry about clearances.
Most of the forum posts I see are mainly around fitting wider tyres, not taller ones.
I've got Halfords site open and they'll do a free mobile fitment of 4 tyres, plus they've got a 15% off deal atm when buying 4 tyres, so I'm tempted to just buy them and see what happens.

 

[Charlie Farley]

side wall profile (height) is a percetage of the tyre width.

235 is pretty well accepted as the best width on an A4/S4 chassis B7 on suitable rims.

235/45 17
235/40 18
235/35 19

If you have non-s-line suspension then that small increase won't make much difference assuming you are running stock offset.
your speedo maybe be out a bit though.

 

[Charlie Farley]

My old bus tramlined really badly with continental 19" tyres , I changed tyre brand and pattern and the problem disappeared but they were still the same size 235/35 19 , never had any tramlining with the 18" with sp max on etc.

 

[Oatmeal]

I decided in the end just to got for 235/40/18's. Didn't feel like jumping down a rabbit hole this time.

Weirdly though I discovered why my car tramlines so hard, as the tech was replacing the existing tyres he said that I'd somehow bought BMW run flat tyres.

Car is far more comfortable now, not as noisy and doesn't tramline like a b*tch anymore