Can I change my tyre profile? 265/30/20 to 265/35/20?

[Ollieox]

I have a 2009 A5 cab 3.0lt Quattro and need some new tyres. Having looked around the 265/30/20 are very expensive and limited in choice. Has anyone changed their tyres to a different profile...( I’m looking at the 265/35/20) and if so have you had any issues? 

The 265/30s are quite a hard ride and my fronts have both suffered from side wall bulges

thanks in advance for your input

[Magnet]

Hello Ollie,

Thanks for being in touch. 

The first port of call when considering changing tyre dimensions is to calculate what effect that change has on the outside diameter on the wheel + tyre. 

Moving from your current ( manufacturer’s original tyre size?) tyres to a higher 35 profile tyre, will increase the OD by just over 13mm ( approx.1/2 inch), and although not significant, is sufficient to cause second thoughts, in terms of effect on gearing, speedo etc. 

If you couple this with second-thought concern with the potential of your insurer being interested in the fitment of non standard tyres, then it may help to concentrate the mind on whether the economics are worth while. 

You don’t mention the load (xl/non XL) and speed ratings of the proposed size compared with the ones you have now, but these would indeed be meaningful. We take it your current ones are not run flat -? 

It’s interesting that you mention the hard ride with your current 30 profile tyres. This is a meaningful issue, and the downside of ‘nice looking’ large diameter wheels. 

It would be worth looking in your handbook to check the original specified tyre sizes for the 20 inch option wheels. Who knows, someone might have previously fitted non standard tyres, and you could be trying to match to that anomaly! 

Kind regards,

Gareth. 

[Ollieox]

Thanks for your reply Gareth...

in answer to your questions the existing 260/30/20 on the car are load rating 95, speed rating Y and the are XL. 
 

if the 265/35/20 will increase the tyre height too much how about going with a 275/30/20? There seems to be much more choice. 
From what I can make out the 265/30/20 are what the car was originally sent out of the factory with

 

regards Ollie 

[Magnet]

Hello Ollie,

Thanks for coming back on this. 

So your additional requirements will be to match the load and speed ratings. 

We haven’t yet considered whether the current tyres are run-flat on not, and if so, then that of course has to be matched. 

To assess the effect of different widths and profile, just calculate the effect of the proline as a % of the width. 

I can appreciate the quest to try to save money and extend choice, but obviously moving from the manufacturer’s specification will result in you having non standard tyres on the car, and you will have to decide whether you inform your insurers - or not. 

Kind regards, 

Gareth.