aerosam
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| posted on 21/6/09 at 12:59 PM |
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help me work out my tyre sizes...
I have fitted 245/45/R17 tyres to the rear, I want to fit 225 wide tyres to the front, so what profile should they be to match the rears?
The wheels are 8.5J x 17inch.
Thanks!
Had enough of this dictatorship known as LCB. Gone elsewhere, not coming back. Kiss my ass ChrisW.
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Mark Allanson
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| posted on 21/6/09 at 01:06 PM |
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Why do they have to match?
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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aerosam
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| posted on 21/6/09 at 01:15 PM |
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because if they are a different diameter they will rotate at a different rate to the rears and confuse the ABS.
Should have mentioned this is for my tintop BMW.
Had enough of this dictatorship known as LCB. Gone elsewhere, not coming back. Kiss my ass ChrisW.
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Mark Allanson
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| posted on 21/6/09 at 01:24 PM |
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Ah! I thought it was for your proper car
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Mark Allanson
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| posted on 21/6/09 at 01:29 PM |
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Tyre Width Profile Diameter Rolling Dia
225 50 17 25.85826772
Tyre Width Profile Diameter Rolling Dia
245 45 17 25.68110236
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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Humbug
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| posted on 21/6/09 at 01:32 PM |
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245/45/17 has a theoretical diameter of 65.23cm
225/50/17 has a diameter of 65.68cm, i.e. just under half a cm different depends how sensitive the ABS is 
(I calculate a 225/41.3/17 to have a diameter of 61.77cm, quite a lot different...)
[Edited on 21.06.2009 by Humbug]
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tul214
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| posted on 21/6/09 at 01:35 PM |
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225/50/17 would give a +5mm difference
225/45/17 would give a -18mm difference
Ha Ha...eta..must type faster!!
[Edited on 21/6/09 by tul214]
1.6 Raw Super6 sold
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Macbeast
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| posted on 21/6/09 at 01:37 PM |
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225 x 49
Blxed first answer, sorry
[Edited on 21/6/09 by Macbeast]
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aerosam
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| posted on 21/6/09 at 05:32 PM |
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So the 245 wide tyres have a rolling circumference of 102.463cm and the 225 tyres have 103.169cm.
So the front tyres will turn 0.706cm less for every rotation of the rears.
I doubt it's that sensitive - thanks guys!
Had enough of this dictatorship known as LCB. Gone elsewhere, not coming back. Kiss my ass ChrisW.
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