Tire size question: Ok to swap 235s with 255s?

"Tapas" (tapas) 01/31/2018 at 08:15 • Filed to: None

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Update:

Thanks for the comments, guys! The Q5 now has new tires in the original size.

My dad’s Q5 needs new tires. (picture unrelated)

It comes with 235/R60/18 103W tires all around from Audi. But getting them at a decent price is proving to be a challenge.

There’s a store that’s carrying the exact same tire in 255 103H rating for a decent price. Indian roads don’t allow for high speeds above 130 mph/210 kmph any way.

I think this should be ok.

But just to make sure - is it ok to go with a slightly wider tire with the same 18" wheels?

Are there any trade offs?

Tekamul > Tapas 01/31/2018 at 08:37

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If they are 255, you probably want an R55, not R60. As long as the wheel is an 8.5" or wider, it will fit fine. Any chance they have 245s?

EDIT : The internet says the Q5 has 8x18 wheels, so 255 is probably too far.

e36Jeff now drives a ZHP > Tapas 01/31/2018 at 08:43

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Your speedometer will be off. A 255/60/18 will have more sidewall than a 235/60/18. The first number is the width of the tire in millimeters. The second number is the percentage of the first number that is sidewall. so a 255/60 has a 153mm sidewall. A 235/60 has a 141mm sidewall. A 255/55/18 tire would be much closer in overall diameter than a 255/60/18 is.

BrianGriffin thinks “reliable” is just a state of mind > Tapas 01/31/2018 at 08:43

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If the available tires are 255/60/18, the total diameter is going to be different from stock. Your speedo will be off by a bit and the car may ride differently or they may rub. It’ll probably be okay, but see if you can’t find tires that keep the same aspect ratio.

Wacko > Tapas 01/31/2018 at 08:46

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https://tiresize.com/comparison/

generally speaking a larger/wider tire will be harder on gas. but larger contact point and greater traction.

if too large may rub when turning.

cbell04 > Tapas 01/31/2018 at 09:54

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If be worried about rubbing but the speed difference won’t be to bad at all.

Cé hé sin > Tapas 01/31/2018 at 10:26

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If he’s driving in India, worrying about whether his tyres are too wide is probably the least of his problems!

Future next gen S2000 owner > Tekamul 01/31/2018 at 10:37

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I ran a 255 on a 17x8 wheel for a while. Brands are all a little different but they fit fine. 255x40x17 on a 17. Upsized from a 245x45x17 to keep a similar OD.

Future next gen S2000 owner > Tapas 01/31/2018 at 10:38

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You’ll have to match the OD, ie reduce the sidewall ratio. Depending on the brand you will probably be fine. Some run wide, like shoes.

If you can’t match the OD, get a tuner for Audi’s and reset the speedo.

merged-5876237249235911857-hrw8uc > Tekamul 01/31/2018 at 10:54

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Eh, an 8” wheel should be fine with a 255 width tire, but yes, you need to reduce the aspect ratio to make the overall diameter work. Check out tires.com for their tire size calculator and you can punch in the different values to see what the differences are.

46and2aheadofme > Tapas 01/31/2018 at 10:58

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In my experience it’s always best to go with stock tire size. I’ve switched a bunch of times (cars, trucks and bikes) and almost always been unhappy with the results. Just my .02.

Tapas > Cé hé sin 01/31/2018 at 11:34

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Very true