I think the size RBH is suggesting is the 255x40x19 that he has, if you use the calculator you'll see it makes just a 1.2% difference on your speedo, thats within the manufacturer tolerance. If you fit a 45 profile it will make a bigger difference 3.5% which could put your speedo reading under what you are actually doing.
An SUV rated trye is likely to have stiffer sidewalls and sometimes a chunkier tread to allow for mild offroad use so you wont neccessarily improve the ride.
going to a 255x40 instead of 245x40 will give 10 mm more width and 4mm more sidewall which doesn't sound much but should improve the ride and give better rim protection.
I did it on mine (although 255x35x20) and the extra 3.5 mm in sidewall and slightly more volume makes the ride very good.
Hope that helps.
Last edited by Drew; 22-09-2020, 08:58 AM.
Reason: I've edited that because I got the profile wrong in the first line, it should have read 40 Not 45.
I think the size RBH is suggesting is the 255x45x19 that he has, if you use the calculator you'll see it makes just a 1.2% difference on your speedo, thats within the manufacturer tolerance. If you fit a 45 profile it will make a bigger difference 3.5% which could put your speedo reading under what you are actually doing.
An SUV rated trye is likely to have stiffer sidewalls and sometimes a chunkier tread to allow for mild offroad use so you wont neccessarily improve the ride.
going to a 255x40 instead of 245x40 will give 10 mm more width and 4mm more sidewall which doesn't sound much but should improve the ride and give better rim protection.
I did it on mine (although 255x35x20) and the extra 3.5 mm in sidewall and slightly more volume makes the ride very good.
Hope that helps.
Mines are 255/40x19
i personally would go any more than this.
Why would you wanna out SUV tyres on.....they'll be more expensive
The second figure is the sidewall height expressed as a percentage of the width. So if you increase width you increse sidewall height by that percentage as well. That second figure is not fixed your sidewall height is 40% of the width i.e. 40% of 245 is 98mm, thats the height of the sidewall. Increase to 255 width and 40% is 102mm so you gain 4mm extra sidewall. I know it doesn't sound a lot but you also increase the volume of the tyre as well and greater volume equals a smoother ride.
Believe me MR rock -man .
im running 225-35-18"
and the ride dare I say is a bit "crashey "
now if I had been cleaver I could of and I wish I had gone for 45 profile
less crashey esp with our roads being full of holes .
yes it may look better with lower profile,but for transporting family around a higher profile is more family friendly.
if you are thinking of SUV tyres then my answer would be no !
as potentially you are fitting a tyre that is not designed for use on a car
but that's my therory.
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