Barrymagrec
pfm Member
Only Boeing and Airbus ones in the main. Avoid any of those and you'll probably be ok
Be O.K. on early Comets and DC10s then.
Tyre sizes and departing from OEM spec
- Thread starter Sue Pertwee-Tyr
- Start date
Be O.K. on early Comets and DC10s then.
-alan-
pfm Member
I was only a minor part of the team that did the fatigue calcs on those - the subsequent investigation made that quite clear
Seeker_UK
Feelin' nearly faded as my jeans
1 - As long as you don't speed, there's no problem. If you do speed and get caught, "sorry officer I had big tyres" won't cut it.
2 - That's a very grey area and down to what the tester thinks is safe and roadworthy IAW the guidelines - https://www.gov.uk/guidance/mot-ins...les-wheels-tyres-and-suspension#section-5-2-3 for example, rubbing at full lock might be considered an issue ("fouling").
So you might get away with it, or you might not.
Yank
Bulbous Also Tapered
A quick back of the envelope calculation suggests a 3% change in diameter would give you just slightly under a 10% change in the rolling circumference, which would potentially increase your car speedo error beyond the 'nominal' +10%/-0% that manufacturers are believed to be allowed*
Might be just a case that somebody's done the calc. and figured out that's the max change you can have before your speedo is legally unfit for purpose ?
*I haven't had my morning coffee yet, so that calc could be rubbish btw..
And since the odometer is part of the speedo, your mileage would also be off, affecting service intervals and such.
It's not going to be sufficiently far out to make a difference, service intervals are nominal anyway. If 10,000 miles becomes 9500 or 10500, no big deal.
Usually messes up the scrub radius as well making handling twitchy, especially in an emergency stop on variable surfaces.
SteveG
pfm Member
My wife's SLK needs tyres and, having been impressed by the Michelin Cross Climates on my C-class, I'm also thinking about putting all-season tyres on that. The front (225/40R18 92Y XL) is no problem as there are plenty of all-seasons available in that size, including the Michelins. The rear seems to be a problem though - it's 245/35R18 92Y XL and there don't seem to be any all-seasons matching that size and speed rating. The closest (and which some sites list as a fitting for the car) is the Continental AllSeasonContact however it's a W speed rating in that fitting (and the front fitting), not Y. Given W speed rating is 168mph (compared to the 186mph of the Y) then that still seems like it should be ok (given the top-speed of the car isn't much over 150mph).
Any thoughts?
Any thoughts?
Yank
Bulbous Also Tapered
Is the Michelin Pilot All Season 4 available in your sizes?
SteveG
pfm Member
Doesn't look like it. Looks like they tend to be for bigger and lower profile options.
Yank
Bulbous Also Tapered
Not that this does you any good, but your sizes are available for the Pilot Sport All Season 4 in the USA:
https://www.tirerack.com/tires/Tire...iameter=18&rearSortCode=53950&performance=ALL
martin clark
pinko bodger
what are the standard range of tyre sizes quoted? It'll be in the handbook, might also be on a sticker on the driver door pillar.
TBH if you can fit the same size on the rears as the fronts, they are only 20mm diff width, I'd just do that. Fitting allweather tyres of same tread width all round isn't suddenly going to turn it into an oversteery monster.. esp on an SLK
And there is just so much 'oh but insurance' FUD up-thread it is unbelievable.
- Check the handbook for the recommended range of sizes.
- Fit within those ranges if pos. Pick for purpose first, like your entirely-justifiable consideration of response to local climate: and forget the excess speed rating, you don't need 186mph in the UK...
- Fit, forget: enjoy a safe drive in-season everywhere. You have taken more care over your choices than / a desperately, god-awfully high proportion of the unthinking/ covered by the exactly-similar kinds of insurance provisions and considerations.
martin clark
pinko bodger
PS on speed rating: of course winter/cross climate tyres aren't available in the higher bands - poor conditions are the definition of mitigation against needing such!
sincerely
Captain Obvious.
sincerely
Captain Obvious.
James
Lord of the Erg\o/s
Even if the rear wheels are wider? I think that would look naff.
Actually, I think that combination is off. The rear 245/35R18 tyres have a smaller rolling diameter than the 225/40R18 fronts. A closer match would be 255/35R18 on the back. If the rear wheel is at least 8.5" wide, 255 section tyres will fit with no problems, except maybe more understeer at the limits.
SteveG
pfm Member
The diesel SLK has masses of torque and is quite prone to oversteer, and in slippery conditions even with the traction control active - so I wouldn't be inclined to fit narrower tyres than standard at the back.
Mercedes models tend to have so many possible fitments that they're not marked on the car or in the handbook - so it can be tricky to work out what standard options are available.
Mercedes models tend to have so many possible fitments that they're not marked on the car or in the handbook - so it can be tricky to work out what standard options are available.
SteveG
pfm Member
Definitely the case with winter tyres, but not with cross climates as they are an all year fitment.
Tony Lockhart
Avoiding Stress, at Every Opportunity
A friend took his Pirelli Sottozero-shod Golf Edition to the Nurburgring in spring a few years ago. The Sottozero is a pure winter tyre. Drove flat out in mild, wet conditions fast enough to have to stop to let his passenger puke over an Armco barrier, and cleared 140mph a few times. That was in 2013, and winter/cross climate tyres have come a long way since.
And no, he didn’t destroy the tyres, the rubber didn’t turn to bubblegum, and he knows how to drive very fast.