Has anyone tried slightly different tyre size from the standard.

I'm running 235 45 r18 but there seems to be some very competitive pricing on 245 40 r18.

I'm aware what the physical differences are but keen to hear from anyone who has actually had these fitted.. any issues?

I moved from the standard 235/40/19 to 245/40/19. Partly for the larger contact patch, partly for the price (more common sizes tend to be cheaper taking advantage of economies of scale). No difference in feel and I’d have to take it on a track and compare track times to see whether I’ve gotten any benefit.

Since then prices seem to have altered and 235/40/19 seems to be just as competitive, if not cheaper and the 245s I had (Goodyear F1 Asy5) just looked a bit bulgy and not as neat. Might not be the same for all makes but I’ll go back to 235s when it’s time to change. Just not worth it.

There’s also the minor matter that a tyre size change away from manufacturer recommendation needs to be informed to them so check that too just in case.

Thanks.

Current insurance provider won't insure modifications so I'll shelve this idea for know.

Hi.

If you need any help with insurance at all then please feel free to drop me a line.

Regards,

Dan.

Just to add my 2p - going up to a 245 section on the OE 18" wheel isn't advised. My understanding is that 18" MQB wheels are all 7.5J - the widest you should be putting on that is 235.

@Carlston will know for sure (just because you've shelved the idea doesn't mean others won't find this thread in the future!).

I'm surprised the insurance company care - it's nothing to do with an MOT, and as long as they're Superb type approved (or whatever the term is, Carlston will say) there should be no issues, unless you're changing wheels. Even then, I was only charged a £10 admin fee to change my wheels when I was 19, so your insurance should be fine. Weird.

Edited 3 August, 20253 Aug by OccyVRS

29 minutes ago, OccyVRS said:

I'm surprised the insurance company care - it's nothing to do with an MOT, and as long as they're Superb type approved (or whatever the term is, Carlston will say) there should be no issues, unless you're changing wheels. Even then, I was only charged a £10 admin fee to change my wheels when I was 19, so your insurance should be fine. Weird.

I think you are not thinking like an insurance risk analyst, they don't care if it passes a MOT, if it doesn't it will either be rectified, scrapped, or insurance will be invalidated.

However if modifications to non standard are done to save money (eg cheaper tyre size) then they are going to be less happy by assuming the owner is not doing everything a normal person would to maintain the car to the default standard, so is a higher risk because don't know where else they might also be cutting corners or quietly making changes.

3 minutes ago, SurreyJohn said:

I think you are not thinking like an insurance risk analyst, they don't care if it passes a MOT, if it doesn't it will either be rectified, scrapped, or insurance will be invalidated.

However if modifications to non standard are done to save money (eg cheaper tyre size) then they are going to be less happy by assuming the owner is not doing everything a normal person would to maintain the car to the default standard, so is a higher risk because don't know where else they might also be cutting corners or quietly making changes.

I agree, but going up to a more expensive tyre width isn’t really the same thing, I’d argue. Then again, is there even an option to tell the insurance specifically about wider tyres?

I know several people that regularly drive on wider semi slicks on the road - two have been in smashes and had no issues.

The only issue I can see is that I don’t think any Superb is approved to run on 245s.

42 minutes ago, OccyVRS said:

Just to add my 2p - going up to a 245 section on the OE 18" wheel isn't advised. My understanding is that 18" MQB wheels are all 7.5J - the widest you should be putting on that is 235.

@Carlston will know for sure (just because you've shelved the idea doesn't mean others won't find this thread in the future!).

I'm surprised the insurance company care - it's nothing to do with an MOT, and as long as they're Superb type approved (or whatever the term is, Carlston will say) there should be no issues, unless you're changing wheels. Even then, I was only charged a £10 admin fee to change my wheels when I was 19, so your insurance should be fine. Weird.

The 18" rims on the Superb MK3 are at least 8" wide.

The Superb MK3 parts catalogue shows most are 8Jx18 ET44, but there's a couple of BRAGA alloy rims listed at 8.5Jx18 ET41.

Edited 3 August, 20253 Aug by Carlston

4 minutes ago, Carlston said:

The 18" rims on the Superb MK3 are at least 8" wide.

The Superb MK3 parts catalogue shows most are 8Jx18 ET44, but there's a couple of BRAGA alloy rims listed at 8.5Jx18 ET41.

OP would want the BRAGA wheels then, really, as 245s on an 8J is the realistic maximum.

I’m maybe correct that the widest 18” on the MQB platform is 7.5J but, of course, that is assuming I engage my brain and realise the Superb isn’t MQB. Whoops.

11 hours ago, OccyVRS said:

I engage my brain and realise the Superb isn’t MQB. Whoops.

It is.

Bloody Octavia drivers, coming over here making claims about our Superbs. Go back to Octavialand! 😝

2 hours ago, logiclee said:

It is.

I thought the Superb and Passat shared the A6 platform - turns out they don’t.

I’ll stick to the Octavia forum.

14 hours ago, SurreyJohn said:

If modifications to non standard are done to save money (eg cheaper tyre size) then they are going to be less happy by assuming the owner is not doing everything a normal person would to maintain the car to the default standard, so is a higher risk because don't know where else they might also be cutting corners or quietly making changes.

I'd agree with this about everything except tyres (nothing else springs to mind at the moment) where a better tyre can be cheaper because of unusual pricing strategies (on reflection, not unlike insurance I guess). You can substitute a premium standard tyre with a premium tyre of larger width thereby increasing grip/safety, and in this case I believe make the speedo more accurate for less cost (or at least you could at the time). I guess an insurance risk analyst also sees higher risk as higher premium though.

When I enquired with my insurance company (Allianz) they just don't insure any modifications, full stop.

It sounds like from the above posts that the new tyre size may not work anyway but good to know.

You'll gain far more grip from sticking on some Pilot Sport 5s than you will going up to a 245 or so - that extra 10mm won't make any difference unless you're on a track and running semi slicks at the ragged edge.

Evening all ,

I have noticed that I have seen a few Skoda in my location using stretched tyres !

5 minutes ago, super717 said:

Evening all ,

I have noticed that I have seen a few Skoda in my location using stretched tyres !

Very slightly stretched tyres reduce sidewall/carcass flex (shoulder roll) and can marginally improve handling in that respect. Many prefer an increased contact patch, however, and in most cases a stretched tyre is for... idiots.