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S60 & V60 '11-'18 / XC60 '09-'17 General Forum for the P3-platform 60-series models |
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Xc60 TyresViews : 456 Replies : 10Users Viewing This Thread : |
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May 6th, 2024, 19:25 | #1 |
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FWD , 235/65R18 on the front , 235/60R18 on the back
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May 7th, 2024, 13:13 | #2 |
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It's not factory (all tyres were same size) but it's not illegal or dangerous either, as long as the tyres are match on the same axle and do not foul the bodywork or chassis.
As said above, if the larger tyres are on the front it will make your speedometer read less.
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May 7th, 2024, 14:57 | #3 |
"Archie"
Last Online: May 17th, 2024 09:52
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My understanding is that this would be illegal. Speedometers may over-read (ie indicate you are going faster than you actually are) by something like 5% (might even be 10%, I'm not certain) but may not under-read at all (ie indicate you are at the speed limit, whereas you are actually speeding). That is one reason why so often you see cars driving at a few mph below the speed limit - car manufacturers err on the safe side, and routinely slightly over-read, so the driver often assumes incorrectly that he/she is driving at the limit whereas in fact is driving below it (easily checkable with a GPS on a straight and level road). You should ensure the tyres on the front are no larger than whatever the car is meant to have per the owners handbook.
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XC60 D5 AWD (2015) |
May 9th, 2024, 11:57 | #4 |
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May 9th, 2024, 13:28 | #5 | |
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Quote:
Good evening sir just pulled you over to ask if I can borrow your car to go for a spin and check your speedometer is accurate? - Not likely to ever happen in the real world. |
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May 10th, 2024, 09:40 | #6 |
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Swap front and rears sounds like the best solution providing they clear chassis ok
I’ll look to return to standard when the rears wear out ! |
May 10th, 2024, 10:45 | #7 |
"Archie"
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It is illegal in the UK to have a speedometer which is not reading within the permissible tolerance. If your tyre sizes take you out of that margin then yes, illegal. I had exactly this debate once with a tyre installer, who was worried that my winter tyres/wheels which he was fitting, which had a slightly smaller radius than the summer tyres/wheels being removed, were outside the allowed tolerance, till we checked the vehicle handbook which showed which sizes are approved to keep within the permissible speedometer regulations (and of course, not interfere with the bodywork).
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XC60 D5 AWD (2015) |
May 10th, 2024, 12:59 | #8 |
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IIRC, tires can be different size, but the circumference should be within 5% of the factory size.
Even if you take all 4 factory sizes, and calculate the circumference, they're not the same. So, tire 235/65/18 makes 762,7mm with 1 rotation, while 235/60/18 makes 739,2 mm with 1 rotation. That's 23,5 mm more with each rotation, which is 3,08% less, which is within the 5% tolerance. On FWD/RWD car it doesn't make any difference. If it was 4WD and/or diff locks, then it would not be ideal.
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MY16 XC60 D4 |
May 7th, 2024, 14:54 | #9 |
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