Heya all.

so I have 1 rear tyre that needs replacing. It’s worn on the outside quite substantially. The other side does not have the same issue.

The 3 good tyres have about 50% tread.

I’m ok with replacing both rears and getting an alignment done. At the same time I will get some MAD auxiliary springs I bought, installed anyway.

What I’m curious about is I currently run 225/50r17 all round. The fit is a bit tight, especially at the front and I want to go to 215/50r17. 
Could I run the decent 225’s on the front for another 10k kms and have 215’s on the rear for that time?

The size difference is about 1.5% (new) but the 225’s are worn, so difference would be closer.

Also as the larger tyres would be on the front. The Haldex won’t register them as slipping (I would think) until they actually do. Unlike having smaller mismatch in the front.

what does the brains trust think?

I’m not keen on replacing all 4 just yet, even though they were cheapies, bought to test whether the smaller rim larger tyre combo would reduce road noise. And yes it made an enormous improvement.

I’m about to buy some 16’s for running some AT tyres for an outback trip.

 

Edited 1 October, 20223 yr by Rkdee

I’m reading on other forums Haldex won’t be affected by under 4% differences 🧐🤔

Ended up putting the 215/50’s on the front. 
I can’t really tell if there has been an increase or decrease in road noise, so better tyres and loss of sidewall probably even out (or the Pace pc10 is really good value)
Bought Kuhmo Ectsa pa51. 

Not really sure what pressure to run - trying 38psi but may bump it up to 40psi.

400km round trip on terrible country roads, while towing a trailer, they rode just fine. Another 200km today with no trailer and very happy, pushed it through some twisties in pursuit of a beemer. I like my car. 
 

There is a bit of a clunk in the rear when going from 1st - 2nd - but not in any other gears - that I had not noticed previously. Hoping it’s nothing serious, might hurry up the purchase of 2 more 215/50’s

Edited 2 November, 20223 yr by Rkdee

I'm confused, what are you driving? Is it a Superb 1.8 TSI 4x4? Your tyre sizes and pressures are way different to my 2010 1.8 TSI.  My car runs 225/40-18's, front tyre pressure is 32psi and rear 33-34psi.

On 02/11/2022 at 08:51, Rkdee said:

Ended up putting the 215/50’s on the front.

Not really sure what pressure to run - trying 38psi but may bump it up to 40psi.

 

215/50R17 tyres have the same standard load index as 205/55R16 and 225/45R17, so use the same tyre pressures that you would use with those tyre sizes.

 

Edited 7 November, 20223 yr by Carlston

@Andy9-5 2.0 125kw diesel 4x4

I find running lower than 36psi has the front tyres wearing on the edges rather than evenly.

 

@Carlston thanks.

Update:

put new tyres on the rear today. The “clunk” between 1st and 2nd has gone. 
 

So a 3.5mm difference in tyre wall height between front and rear was noticeable by the Haldex. 
Certainly has me wondering about the 4% tolerance. 
My difference was 1.5% and the clunk was quite noticeable - unless going around a corner when the gear change was made.

 

Also the road noise has definitely decreased with all 4 new tyres. So, much of the noise must have been resonating from the rear 🤔

might slip some foam pieces into the cavity above the wheel arches.

 

Out of curiosity, is the recommended tyre pressure not on a little chart on the inside of the fuel filler flap? It certainly is on UK/European spec cars. 

@Andy9-5 it is. 
But I’m pretty sure recommended is not relevant when I’m using non-standard tyre sizes. And @36psi I found the 225/50r17 was wearing on the edges, suggesting under-inflation. 
the 215/50 looks a little under-inflated @36psi too. It handles fine at @38psi 🤷🏼‍♂️