Fitting New Wheels and Tyres - How Crucial Is The Load Rating?

[190]

The one guy said that he only got 40-45k miles out of his tyres. I’ve never heard anyone get even close to that. I’ve managed more than 20,000 miles a few times but doubling that is incredible!

You have to bear in mind that it was a US based forum where it's the norm to expect very high miles out of tires, Perhaps the tire manufacturers also use harder rubber compounds to facilitate that. Motorways vs town driving does make a huge difference. When reverting to town use after many years of predominately motorway driving I can recall be surprised when a set a of tyres only lasted 20,000 miles. I'm back on the motorways again and have already put 30,000 on a set of tyres with plenty of tread left yet.

 

[190]

To go back to the OP's question of how critical is the load rating. My initial thoughts were that in practice the lower load rated tyres would probably be ok because there is usually a small safety margin built in.

Take my car for example: maximum permitted rear axle weight is 1060 Kg with the tyre load rating being specified as 89 giving approx. 10% more at 1160 KG.

When you throw in the fact that I'm extremely unlikely ever to trouble the axle with 1060 Kg and that the car can only legally be driven at half it's maximum speed then it seems to me that in the real world there must be safety margin and to spare in the tyre specification. Perhaps it's not that simple but I'd sleep at night.

 

[markjay]

To go back to the OP's question of how critical is the load rating. My initial thoughts were that in practice the lower load rated tyres would probably be ok because there is usually a small safety margin built in.

Take my car for example: maximum permitted rear axle weight is 1060 Kg with the tyre load rating being specified as 89 giving approx. 10% more at 1160 KG.

When you throw in the fact that I'm extremely unlikely ever to trouble the axle with 1060 Kg and that the car can only legally be driven at half it's maximum speed then it seems to me that in the real world there must be safety margin and to spare in the tyre specification. Perhaps it's not that simple but I'd sleep at night.

You are correct, also in the sense that the load index specified by the car manufacturer ensures that the car is safe when loaded to the maximum permissible weight (which never happens) and driven at the maximum speed (which also never happens), so anything under the official load index will be fine.

BUT - there are legal issues and insurance issues involved, which is why you shouldn't be doing this. Similarly, you shouldn't fit tyres with lower speed rating than those specified by the car manufacturer, even if you never exceed 70mph. Etc.

 

[Gowm]

Cheers for that theory was right, number was wrong lol

 

[190]

BUT - there are legal issues and insurance issues involved, which is why you shouldn't be doing this. Similarly, you shouldn't fit tyres with lower speed rating than those specified by the car manufacturer, even if you never exceed 70mph. Etc.

Except for winter tyres, I'm sure the tyre shop wouldn't do it anyway.

It's particularly annoying that I have to use V rated tyres because the the top speed is listed as 143 MPH. In practice H rated at 130 MPH would be enough and they would ride better.

I wonder what Volvo have done when specifying tyes now that all their cars are limited to 112 MPH.

 

[st13phil]

You have to bear in mind that it was a US based forum where it's the norm to expect very high miles out of tires, Perhaps the tire manufacturers also use harder rubber compounds to facilitate that.

Back in the late 1980's when I visited a relative in Canada I was astonished to see that some national tyre suppliers would guarantee mileage from tyres. From memory, the cheapest were guaranteed 40k miles, up to the most expensive that were guaranteed to cover 70k miles. I commented at the time that they must be made of wood - a view that was reinforced when a few days later I had to brake hard in a rental car on a wet road: they delivered a scarily low level of grip.

 

[tonysmb]

The one guy said that he only got 40-45k miles out of his tyres. I’ve never heard anyone get even close to that. I’ve managed more than 20,000 miles a few times but doubling that is incredible!

Many years ago we had a first-generation (W168) A-Class diesel. Bought new, fitted with Michelin green/eco tyres (can't recall exact type), tyres never rotated, primarily used by wife on dual carriageways etc. and when I replaced the rear tyres they had covered over 70,000 miles.

Even then they weren't down to the wear indicators by any means but were replaced as they were starting to show signs of cracking in the sidewalls. I pointed out to the tyre fitter that they were original tyres and I was surprised how many miles they'd covered, his reply 'We don't like customers like you', probably only half-joking. Conversely, a quickish fwd car, only managed 6,000 miles out of one set of front tyres whereas a different brand on the same car, same driving conditions and style, lasted 18,000 miles.

 

[ToeKnee]

Recently replaced the rears on my SL500 at 31000 miles, they weren't near the tread wear indicator but I changed them as they were over 8 years old (date indicator was for before car was delivered/registered).

 

[NJSS]

BUT - there are legal issues and insurance issues involved, which is why you shouldn't be doing this. Similarly, you shouldn't fit tyres with lower speed rating than those specified by the car manufacturer, even if you never exceed 70mph. Etc.

If you fit non-standard wheels or tyres you must advise your insurers to ensure that in the event you make a claim they avoid it on the grounds of an undeclared modification. I would advise doing this in writing & ensuring that you get an acknowledgement or reply.

NJSS

 

[markjay]

If you fit non-standard wheels or tyres you must advise your insurers to ensure that in the event you make a claim they avoid it on the grounds of an undeclared modification. I would advise doing this in writing & ensuring that you get an acknowledgement or reply.

NJSS

Correct, but even if you do declare it, and it later transpires that the tyres were substandard (i.e. not meeting the manufacturer's recommendations), you may - in some circumstances - end up with an invalidated policy.

 

[NJSS]

Absolutely.

I should have expanded what I wrote to suggest that one should get insurers approval to any modification; even if it means a little more effort & a revised premium.

NJSS

 

[cp3377]

Definitely go 97. I replaced two front tyres once on a W211 E500 with 93 rated (18inch) Continental. Still had 5mm depth left after 20k miles. Went in to MB Oxford for a service and got a call saying they had to replace the front tyres, and yes, the tread was wearing well but would I like to come in and take a look. On both the inside walls were splitting which was pretty scary as it wasn’t something I‘d have spotted until...

The guy there - Ed the “Tyre Man” - who had seen it all said this was down to them being rated at 93 and not being able to cope with the weight of the car and was common when people replaced their original sets and weren’t insistent on the exact ratings. Lesson learned, following Ed’s advice I have always managed 40-50k with the right rating on the fronts and got about 25-35k from the rears too on E500s and CLSs. Most of these were long motorway runs admittedly, but using the right tyres with a car that tracks accurately does make a difference. I found that the Continentals were terrific on the E500s, and thought I’d replace the Pirelli’s with them on my Shooting Brake but I’ve been hugely impressed with the P-Zeros so have stuck with them. So some good options and I’m sure others have recommendations too. Hope that helps.

 

[bolidemichael]

You are correct, also in the sense that the load index specified by the car manufacturer ensures that the car is safe when loaded to the maximum permissible weight (which never happens) and driven at the maximum speed (which also never happens), so anything under the official load index will be fine.

BUT - there are legal issues and insurance issues involved, which is why you shouldn't be doing this. Similarly, you shouldn't fit tyres with lower speed rating than those specified by the car manufacturer, even if you never exceed 70mph. Etc.

I disagree about never and never again. When in Italy, I loaded my estate (with the rear seats flattened) from a factory, with cases of glass bottles containing mineral water. This was up to the maximum load capacity in kg including myself and a full tank of fuel.

I then proceeded to drive very quickly back through Italy and France. Had I had to do so, I would've maxed out on the autobahnen, fully laden, as I know that I have the correct OEM alloys in 17" and the correct tyres, corresponding to the manufacturer's specifications, along with the correct tyre pressures.

They were Pirelli Sottozeros, as I had just been in Munich for a couple of weeks and it is essentially the law in Germany to have winter tyres fitted from October to March.

A five litre estate must haul a cargo swiftly! I would never contemplate reducing the load capacity but sometimes, one has no option but to increase, as is the case with winter tyres that are almost exclusively 99(V) for 245/45/17, iirc.

 

[markjay]

I disagree about never and never again. When in Italy, I loaded my estate (with the rear seats flattened) from a factory, with cases of glass bottles containing mineral water. This was up to the maximum load capacity in kg including myself and a full tank of fuel.

I then proceeded to drive very quickly back through Italy and France. Had I had to do so, I would've maxed out on the autobahnen, fully laden, as I know that I have the correct OEM alloys in 17" and the correct tyres, corresponding to the manufacturer's specifications, along with the correct tyre pressures.

They were Pirelli Sottozeros, as I had just been in Munich for a couple of weeks and it is essentially the law in Germany to have winter tyres fitted from October to March.

A five litre estate must haul a cargo swiftly! I would never contemplate reducing the load capacity but sometimes, one has no option but to increase, as is the case with winter tyres that are almost exclusively 99(V) for 245/45/17, iirc.

I beg to differ, sir!

With the winter tyres on, your permissive top speed would have been lower than the car's maximum speed, hence I put it to you, sir, that you, in fact, never drove a car "loaded to the maximum permissible weight" and "at the maximum speed"!

Members of the jury, I rest my case.

 

[bolidemichael]

I beg to differ, sir!

With the winter tyres on, your permissive top speed would have been lower than the car's maximum speed, hence I put it to you, sir, that you, in fact, never drove a car "loaded to the maximum permissible weight" and "at the maximum speed"!

Members of the jury, I rest my case.

If you read again, I didn't claim to have driven the car at the maximum speed of 155mph, but that I did drive it at the maximum permissible speed when fully laden.

Had they been summer tyres, I would've driven the car at 155mph, fully laden, on the autobahn.

 

[markjay]

If you read again, I didn't claim to have driven the car at the maximum speed of 155mph, but that I did drive it at the maximum permissible speed when fully laden.

Had they been summer tyres, I would've driven the car at 155mph, fully laden, on the autobahn.

Hmmm..... you're out on a technicality... more like a loophole I reckon.....

 

[bolidemichael]

Hmmm..... you're out on a technicality... more like a loophole I reckon.....

I wasn't bragging, simply stating that without being aware of manufactures specifications, I wouldn't be able to make progress whilst utilising the function of a fast estate - those nine or so (heavy) cases of water were necessary to see out the two weeks until the container arrived, it was a supply chain masterclass!

Since we're discussing technicalities... I must confess that the Sottozeros as described were actually RFTs and shouldn't have been fitted to my car by the tyre shop (I'm looking at you, Munster Tyres) that sold me the used set for £400+VAT. I didn't know any better until later and have since sold them and replaced them with Michelin Alpin PA4, which aren't as good but good enough.

 

[bolidemichael]

Incidentally, here is the photo

and not a bad avg speed on a Sunday from Geneva (I stopped overnight) to Calais or London.



apologies for the gratuitous OT, OP, this really is about load ratings, honest!

 

[E55BOF]

Drives to Italy to collect mineral water? It must have been very special mineral water...

 

[NJSS]

It looks like special mineral water

NJSS