Tyre sizes

no_1_dave

no_1_dave

no_1_dave

Soldato
Joined
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Gloucester
Do tyres with rated 285/70 fit on a car with 285/65 tyres?
If I change all tyres would it have any negative effect?

I have 4 good tyres all rated 285/70 but my astra is fitted with 285/65 budgets so i'm thinking of swapping them over...
 
285??? Surely you mean 185?

A change to 70 profile from 65s will make your speedo read slow but shouldn't cause too many problems otherwise.
 
They'll fit as long as the wheel diameter is the same (!)

And will make your speedo over-read by a couple of mph at 60mph. Depending how inaccurate it already is.

I find THIS useful for all the figures.


EDIT: oops I just noticed 285 isn't a realistic tyre width for an Astra. If they're 185s then the speedo inaccuracy is only about 1mph at 60mph. (5% of 185mm is less than 5% of 285mm!)
 
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I think he must mean 185, with a profile that high there is no way they are 285 ...unless they are some sort of custom rear muscle car tyres ...and on an Astra, I doubt they'd fit anyway :p

But yea you can change the profile, as Dogbreath said though, your speedo will be a bit out.

The difference is the width, 185 or 285 is the width measurement of the tyre in mm, so the difference is considerable. 285 is a very wide tyre, few cars have them that wide ...certainly nothing hatchback shaped and remotely ordinary anyway.
 
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Its 185.

I have some 185/70 R14's
I'm tempted to put them on the astra which currently has 185/65 R15's

Other then (according to the above site) the speedo being 0.8mph out @ 65mph will there be any difference at all? Is one size better then the other?
 
Well if one set is 14" and the other 15" you can't do it, they won't fit over the wheels. You can change the tyres to a a set with the same wheel size but a different profile but not a totally different size.
 
Moeks said:
Well if one set is 14" and the other 15" you can't do it, they won't fit over the wheels. You can change the tyres to a a set with the same wheel size but a different profile but not a totally different size.
Click to expand...

I know that.
They are the same size, they are different wheels, same size, same fitting, just different measurement as detailed above...
Cheap budget tyres on my astra, good firestone tyres, quite new on the old vectra i'm getting rid of. just thinking of swapping the wheels over first ;)
 
Oh you are actually going to change the wheels, yea you can do that, provided the off-set etc is the same. I should think it will be if the Astra and Vectra are the same generation.
 
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The offset is usually stamped into the back of one of the spokes on the wheel. You'll have to remove one to be able to check. It'll be ET followed by a number like 49. (sometimes it is IS instead of ET but i haven't found any wheels with that on them yet.
 
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