Tyres are rated for load and speed, i.e. take a 205/50-17 91W, the \"91\" applies to the load rating, in this case 615kg and the \"W\" to the speed rating, in this case 168mph.
What is the legal position if one should fit for instance \"89V\" rated tyres to a car that was supplied with \"91W\" rated tyres (\"89\" = 580kg and \"V\" = 149mph) if this rating is within the weight/performance chareteristics of the car?
Also what about insurance?
Thanks.
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The requirements will be in the Owner's handbook.
Just because they were supplied with W rated, doesn't mean the car needs them, sometimes it's cheaper for a tyre to be made in a single higher rating which can also be used on cars which require a lower rating, than to make and keep stocks of several variations.
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This came up a couple of months ago, a forum search should find the thread.
You definitely can't fit tyres rated at a speed below that which your car is capable of, i know that. I suppose it is possible that a car could be supplied with tyres rated higher than required however.
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Hello,
All replies good points, I guess it is not just the weight and speed that are factors in specifying a tyre, it is the more general stresses and strains, engine torque, braking, cornering loads etc.
However I am sure that the "89V" tyres will be a suitable replacement for "91W"'s though I want to be sure that there are no legal or insurance related implications?
Thanks.
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I read on one of the tyre manufacturer's website FAQs that you should get the rating in the handbook, as a higher speed load rating will empede on comfort and a lower speed or load rating would impede on safety margins.
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In some cases, particularly with high performance motor cars, I would be more extreme, and insist on getting the same tyres, down to the brand, as the car was originally equipped with.
At a technical presentation given by the engineering designer of the Lotus Elise, he described the huge number of tyre make / size / spec / pressure combinations which were tried and rejected before the final choice was made.
Common sense suggests that tyre tread and sidewall condition and inflation pressure have more practical bearing on safety than speed ratings - although I suspect that wouldn't get you very far in court!
number_cruncher
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In some cases, particularly with high performance motor cars, I would be more extreme, and insist on getting the same tyres, down to the brand, as the car was originally equipped with. At a technical presentation given by the engineering designer of the Lotus Elise, he described the huge number of tyre make / size / spec / pressure combinations which were tried and rejected before the final choice was made. Common sense suggests that tyre tread and sidewall condition and inflation pressure have more practical bearing on safety than speed ratings - although I suspect that wouldn't get you very far in court! number_cruncher
Whilst this may be true of low volume, high performance cars, with those made in volume, then cost, cost, cost and cost tend to be considered before anything else.
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I read often, only post occasionally
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Yes, I expect that the original fitment tyres on Escorts, Astras and the like are determined primarily by which tyre maker offers the manufacturer the best deal, and engineering dynamics comes a poor second.
I am, however, frequently shocked by how some people wreck high spec. cars - BMW, Merc, Jaguar, etc by putting poor quality tyres on them - even remoulds in some extreme instances - derrr!
number_cruncher
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cheddar, what car is this for because I'd go with number_cruncher on this.
Unless the OEM tyres are difficult to get hold of, or ridiculously expensive, I'd stick with them. Tyre choice makes a huge difference to the handling of my Chevy, even with tyres of equivalent rating.
On the legal/insurance front:
I know that in the US, at least in Texas, insurance companies have refused to pay out on claims where the vehicle was fitted with lower spec tyres than original. I don't think it's happened here in the UK yet but it's sure to come.
Kevin...
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I made the mistake of buying some higher speed "Z" rated tyres for my 2001 Mk3 mondeo 2.5 V6 Ghia X (205/50/17 ZR), only to discover that the load rating was lower than the original 93W rated tyres previously fitted. They were rated at 580kg, enough I thought. 8000 miles later they were worn down to 2 mm on both edges of the tyre, same symptoms as being under inflated, but I am meticulous when it comes to tyre pressures. I was told after a visit to the local Ford Rapid fit that the new mondeo should have "extra load" (XL) tyres (reinforced sidewalls) fitted due to the weight of the car. Some of the higher speed rated tyres are lower load rated, i.e. for the lighter sports cars, not big saloons. That was a costly episode at £125 a tyre.
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Hi,
Mines a TDCi 130 Ghia X originally fitted with Conti Sport Contact 2's then Sport Contact 1's (which were said to last longer and did so). Now been sold Bridgestone Potenza's (top brand!), mentioned to the tyre fitter concern over "V" rather than "W" rating, he reassured me, since noticed load rating difference, "89" rather than "91". I am sure the tyres are up to the job (though wear could be an issue) however I want to be sure I am legal with no insurance implications.
Regards.
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Nothing at all to do with the question but just as a matter of interest. Have been using Toyo (Japanese) tyres for the last few years and there is a local agent near me.
Had two fitted yesterday to the Vectra and was chatting with the fitter as he changed them. I noticed that he didn't use a lubricant to get the initial seal even though there was a tub alongside him. Asked him why and he said they never used it with Toyos as they were a tyre which didn't need it as they were so flexible. Sure enough the tyre gripped the rim as soon as he applied the air gun.
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