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What size tyres have you fitted?

Posted: Sat Jul 22, 2017 8:07 am
by CG8589
Hi all,

I'm going to be changing my Interlagos soon and can't decide what size tyres to go for, 235/40/18 or 225/40/18.

I'm just asking if anyone has found anything wrong with fitting 225's really.

Thanks

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Re: What size tyres have you fitted?

Posted: Sat Jul 22, 2017 8:23 am
by Cuprabob
Only reason to choose the 225/40 size over the OEM size is cost. Also there may be insurance implications of fitting a different size tyre. Personally I would stick to the OEM size as that's what VW engineers chose and set up the car around. Arch gap looks bad enough on the Scirocco without making it worse by fitting a tyre with a slightly smaller sidewall.

Re: What size tyres have you fitted?

Posted: Mon Jul 24, 2017 7:38 pm
by CG8589
Thanks, the price difference was my main reason for asking the question! Might stick with the 235's as the arch gap is big enough already, like you said.

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Re: What size tyres have you fitted?

Posted: Mon Jul 31, 2017 9:48 am
by Astonbarlow
Unless im misunderstanding the post but the 235 section of the code is the width of the tyre. Your rim is made to accommodate a tire of with 235mm, if you put a 225mm wide tyre on you will essentially be created a 10mm difference between tyre and rim, which could potentially cause all sorts of issue with handling. The 40 indicates with side wall radius, therefore if you were to find a tire 235/35/18 that would create a large arch gap and 235/45/18 would create a smaller arch gap but obviously you'd have a lot more tyre to wheel ratio which takes away that sport look.

If you're keeping the same wheel the only number on the tyre you can alter is the side wall radius (40), you have to keep the width and rim diameter the same.

Re: What size tyres have you fitted?

Posted: Mon Jul 31, 2017 7:03 pm
by xjay1337
Sticking a 225-40 on will make it look stupid.
Arch gap will be notably larger.

Stick to 235 40. Decent tyres are around 100 per corner so not a great amount more than 225 40.

Re: What size tyres have you fitted?

Posted: Mon Jul 31, 2017 7:38 pm
by chelspeed
Astonbarlow - Nearly right except the 40 or 35 isn't the side wall radius as in 40mm or 35mm. It's the side wall depth as a percentage of the width so 235/40 mean the side wall is 40% of 235 and for 235/35 it's smaller as it's 35% of 235.

That's why you can go from 235/40 to perhaps 245/35 and keep a similar rolling circumference and gearing. The sidewall depth is a smaller percentage of a bigger number so stays similar.

Re: What size tyres have you fitted?

Posted: Tue Aug 01, 2017 7:47 am
by Astonbarlow
Chelspeed - Ah fair game, yeah always assumed it was in mm. Well im happy to learn something new!

Re: What size tyres have you fitted?

Posted: Wed Aug 02, 2017 10:30 am
by Harry_VW
Astonbarlow wrote:Unless im misunderstanding the post but the 235 section of the code is the width of the tyre. Your rim is made to accommodate a tire of with 235mm, if you put a 225mm wide tyre on you will essentially be created a 10mm difference between tyre and rim, which could potentially cause all sorts of issue with handling. The 40 indicates with side wall radius, therefore if you were to find a tire 235/35/18 that would create a large arch gap and 235/45/18 would create a smaller arch gap but obviously you'd have a lot more tyre to wheel ratio which takes away that sport look.

If you're keeping the same wheel the only number on the tyre you can alter is the side wall radius (40), you have to keep the width and rim diameter the same.
Nope. This will alter the total running circumference and therefore can affect how accurately your speedo reads.