Swapping 19" to 18" or even 17" wheels on a A4 Avant S-line

[white_shark]

Hi all,

I am trying to figure out the best course of action for replacing my rims and tyres from 245/35 ZR19 93Y XL (currently fitted) to 245/40 R18 94H or even 225/50 R17 94H on an A4 avant s-line.

The reasons to do that:

1. The rear tyres are worn out badly, probably due to the lack of wheel alignment
2. I really dislike the bumpy ride and too low profile
3. The differential knocking when wheels are fully turned one way is really bad and is said to be worse on the lowest tyre profile

So according to the wheel size calculator, 19" to 18" should be almost identical. 654mm overall wheel height for 19" vs 653mm for 18". 

But is there anything I am missing here? 

What alloys won't look terrible? I kinda dislike the current look anyways as the profile is too low and the car isn't sporty at all with its laughable 35 tfsi engine. But nonetheless, I'd prefer to keep it look nice.

Thanks for recommendations in advance!

[Magnet]

Hello,

I’m sure you’ve got the logic in the right place with this, and there is one thing for certain- Sports suspension coupled with ‘fancy big wheels’, dictating low profile tyres, with the ‘extra load’ specification, all adds up to an uncomfortable ride. 
I haven’t used the wheel size calculator - preferring my old maths! - but it all boils down to using the smallest diameter wheel that was available on your model at the time - the important bit being that the rolling diameter is maintained, by increasing the profile by the correct amount as the wheel diameter decreases. 
To enhance ride quality, it would be advisable to stay away from XL tyres unless you are carrying heavy loads in this estate car. If at any time you are carrying such loads then obviously you will need XL.

OK, pessimistic, but having increased tyre profile via. smaller wheels, you will still be left with the inherent stiffer suspension of the S Line, but……

Kind regards,

Gareth. 

[white_shark]

Thank you for response Gareth,

Yes I don't expect to miraculously get rid of the 'sport' suspension effects and more to that, I am thinking about replacing my current tyres with run flats. Which should make the situation even worse, or at least cancel out the 19" to 18" swap 😄

 

[Magnet]

Hello Shark,

If you are looking for improved comfort, why on earth are you looking to use run-flats, and put up with their inevitably much firmer sidewalls - unless rim design dictates. 
OK no one can argue about the significant benefits of run-flats on the safety scale, but it’s a bit like walking around and going dancing in safety boots - Incase something falls on your toes! 
Kind regards,

Gareth. 

[white_shark]

Quote

If you are looking for improved comfort, why on earth are you looking to use run-flats, and put up with their inevitably much firmer sidewalls - unless rim design dictates. 

Yeah, I know it may sound controversial but I am fine with increased stiffness as long as it provides me peace of mind when driving long distances. I've had two BMWs in the past with run-flats and they were perfect to me. No worries about potholes, punctures, even bulges are fairly safe and hard to make actually - just drive to the next service if something happens at 80 km/h.

Whereas Audi's system of giving the driver a weak compressor and a tube of some crap to seal the punctures that ruins the tyre and ultimately leads to replacing a pair of them at least... well, this doesn't seem sensible at all to me.

Probably, had I not have an uneven wear on the tyres, I would've kept the previous wheels and just bought a spare. But since I had to basically change at least a pair of tyres, or perhaps all of them, I went on to change the 19" to 17" alloys with Pirelli Cinturato P7 run-flat tyres in 225/50 size. After a few first kilometers, I feel no difference with the previous setup as expected. 

Given that 19" tyres are £50-60 more expensive each, it probably makes sense economically as well. At least if I manage to sell my old wheels 😅

Edited February 3, 2023 by white_shark

[jdragon]

I wonder how this played out....on my A5 I went from 245/40 R18 to 255/35 R19 both OEM wheels

The ride isn't noticeably different constantly rolling on A roads, however they definitely feel bumpier for some of the lanes I occasionally drive on.

which brings me to my next topic; new tyres 

[white_shark]

16 hours ago, jdragon said:

I wonder how this played out....on my A5 I went from 245/40 R18 to 255/35 R19 both OEM wheels

The ride isn't noticeably different constantly rolling on A roads, however they definitely feel bumpier for some of the lanes I occasionally drive on.

which brings me to my next topic; new tyres 

Hey, I've done about 5k miles with the 17" run flat tyres and I can say they are alright. Not great though. Because for the first couple thousand miles I was wondering why the hell the steering at high speeds became so imprecise and wobbly. Like when doing long smooth bends on A roads, I had to basically "catch" the car as if it was constantly trying to steer out of the lane. Then I switched the steering from "comfort" to that other mode ("sport"?) and almost immediately felt a relief. It either got better, or I just learned to live with it.

As for the ride, 17" run flats don't feel any better than 19" regular tyres on bumpy roads. I can't tell for sure since it's been a long time, but it's almost exactly the same.

In the end, the only thing I gained with this replacement is the peace of mind. Perhaps it is worth it. Although, almost no one seems to be repairing even absolutely innocent punctures in run flat tyres in this country 🥶

If I were doing the replacement again, I'd probably go for 18" or even keep the original 19" wheels and buy runflats anyway.