One for the techies

[wotme]

Would it upset the applecart to run a couple of hundred miles with one wheel fitted with a 245 tyre and the other three with 235. The other ratings being compatible.

 

[Boringfrog]

I don't think any problems would occur.

 

[addoaddo]

on the non driving axel it would be no problem. On the driving axel it will make the diff work harder as one wheel will be turning slightly faster then the other assuming the profile of the tyres are the same. It will make your speedo really slightly different <5% but should not be a problem.

There will be a very minor imbalance in braking but unlikely to be seen unless extreme braking.

Personally I would put the odd tyre on the back and not worry

 

[TheBig1]

as above, on a driven wheel it causes issues,

 

[jockaneezer]

I can't see how the width of the tyre (235/245) would make it turn faster, but if the profile were different (60/70 say) that would make a difference and Space Savers would be illegal. As said, stick it on a non driven axle and you will be fine.

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[Silver-Fox]

I can't see how the width of the tyre (235/245) would make it turn faster, but if the profile were different (60/70 say) that would make a difference and Space Savers would be illegal. As said, stick it on a non driven axle and you will be fine.

Exactly
It’s when the profile is different you’ll have problems

 

[addoaddo]

The profile is described as a percentage of the width, so if the width changes the diameter changes as well.

 

[mushy]

Here you go read all about it.

Tire Size Calculator

The best tire size calculator. Use our tire size calculator to find tire size specs and suggested tire sizes. Then check prices for all available tire sizes.

tiresize.com

 

[wotme]

Thanks guys, the reason I ask this question is I don't have a spare but I do have this oversized tyre which I thought of carrying just in case I get a blow out somewhere in the back of beyond and the nearest tyre fitters don't have anything in stock

 

[TerryL]

Thanks guys, the reason I ask this question is I don't have a spare but I do have this oversized tyre which I thought of carrying just in case I get a blow out somewhere in the back of beyond and the nearest tyre fitters don't have anything in stock

Sounds an excellent idea to me as long as the tyre is in good condition.

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[TheBig1]

an excellent idea unless in France, where not only do the tyres need to be the same size and profile both sides of the axle, they even insist on matching tread pattern. a blowout often leads to 2 new tyres being bought unless you carry a matching spare

 

[Deneb]

an excellent idea unless in France, where not only do the tyres need to be the same size and profile both sides of the axle, they even insist on matching tread pattern. a blowout often leads to 2 new tyres being bought unless you carry a matching spare

And in the UK it's an MOT Major reason for failure and could be construed as using a motor vehicle with an unsuitable tyre having regard to the size and type of tyres fitted to the other wheels.

 

[busby]

And in the UK it's an MOT Major reason for failure and could be construed as using a motor vehicle with an unsuitable tyre having regard to the size and type of tyres fitted to the other wheels.

Dont have this spare tyre in the van when it goes in for MOT,,simples.BUSBY.

 

[Deneb]

Dont have this spare tyre in the van when it goes in for MOT,,simples.BUSBY.

He was asking about using it, not having it in the van. Could probably get away with using it in an emergency as long as you don't go for an MOT or have an accident. In my experience though, not many people book their accidents in advance

 

[wotme]

Bugger if education ain't wonderful,

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[Just smiffy]

My Lexus had 225 on the fronts and 245’s on the back.. never had a problem getting to 140mph..?

 

[pappajohn]

an excellent idea unless in France, where not only do the tyres need to be the same size and profile both sides of the axle, they even insist on matching tread pattern. a blowout often leads to 2 new tyres being bought unless you carry a matching spare

In France I would, if possible, use a DIY repair plug for that reason alone.
I've used them in my trailer tyres (regular car tyres, not balloon tyres) and they've been very successful.
VWAlan swears by them in his truck and mini artic tyres.

 

[PeteH]

I would not worry about it, even in France. On Ballance, I cannot see the Gendarmes crawling all over your tyres. They have better things to do. (more cash to be made from motorists who exceed a change of speed limit).

 

[Guigsy]

My Lexus had 225 on the fronts and 245’s on the back.. never had a problem getting to 140mph..?

Front to back isn't an issue. The new Porsche 911 has larger diameter rims at the back.

It's across the axle that could be an issue. The driveline wouldn't like it much and it probably wouldn't do your ABS any favours if you were to call on it. If it's an emergency 'get me home' wheel though, I'd probably run it.

 

[Spanner]

The spare wheel is not part of the mot in the UK

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[Deneb]

The spare wheel is not part of the mot in the UK

Unless it's fitted to one of the axle hubs at the time of the test. You are missing the point.

It is an offence under the Road Vehicles (Construction & Use) Regulations to use a motor vehicle with an unsuitable tyre, having regard to the other tyres fitted to the vehicle. As the use of tyres of two different sizes on the same axle constitutes a major defect if present on a vehicle at the time it is submitted for a test, it would also be good evidence of unsuitable use if found at any time during a road side check or during an examination following a collision, whether the vehicle was subject to MOT testing or otherwise.

Use it at your own risk. Part of the role of DVSA and police vehicle examiners is to examine vehicles in roadside checks and following collisions, and submit evidence of defects to support prosecutions. The risk of detection may be remote, the person considering the use of the tyre needs to consider whether they wish to accept the risk.

 

[Coolcats]

I would treat it as a ‘get you home tyre’ many sorts cars have a slim tyre to use normally they are speed/ distance restricted so if you took the same approach eg max 50mph you should be OK it’s a view but one you should be able to use if you got pulled over

 

[NorthernSands]

The OP simply needs to give the full tyre specs of both sizes. Width difference alone on one axle, even the driven axle, is not a problem (ahem, space savers).

Diameter differences across one axle is where problems step in.

 

[Ridgeway]

In France I would, if possible, use a DIY repair plug for that reason alone.
I've used them in my trailer tyres (regular car tyres, not balloon tyres) and they've been very successful.
VWAlan swears by them in his truck and mini artic tyres.

I use them on my push bike and they are pretty amazing things, now got a kit for the van, exactly the same things even if the ones for my bike are probably higher quality. The trick is to get really sticky ones.

 

[sonny]

If you fit the spare wheel on ,does it not cease to be a spare wheel and become part of the mot.

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[wotme]

Before the sixties there was no MOT and no 70mph limit but what we did have was numerous scrap yards where you could wrestle all day with spanners hammers and crowbars to get what ever replacement part you wanted. Motoring in those days was a pleasure too and comparatively much cheaper. You could buy a complete car in running order for less than a tenner. Definitely not roadworthy but it would run after a fashion. My very first car after raising hell for a couple of years as a suicidal rocker was a huge open top hulk that was entered in the Monty Carlo Rally in the 30s by a decorated military officer. The history was all there in a brown fold out log book and it was still capable of 100mph plus. The problem was keeping it in a straight line having gone through the sound barrier. It cost me forty quid which just about cleaned me out but the fun it gave me was worth every penny. I spent six months tarting it up but I never did get the mechanics 100% so I moved on to something more sedate and sold the old girl for what I paid. Something I now dearly regret as I recently saw a similar model selling for 80K The thing is there was some really unroadworthy vehicles around in those days but no where near as many road deaths. The sheer volume of vehicles on the road today has a lot to do with statistics but I'm sure a lot of unnecessary accidents occur because of inexperienced and/or intoxicated drivers behind the wheel. So having read your posts I've concluded it probably won't cause any harm fitting my tyre unless I'm involved in an incident and the eyes of the law scrutinise every little detail, then of course it will be my wallet that will sustain serious injury
Thanks for all your comments and I promise if I have to use the tyre I will not go over 50mph

 

[NorthernSands]

If you have the full tyre specs you'd get more definitive advice. I would not run different diameter wheels on the same axle (unless within margin of error or very damn close). Ever. Different width is a different matter.

And depending on the type of accident, the scrutiny could get very in-depth. I know of one very low speed accident involving a Land Rover Defender. The Defender driver was penalised because one front brake rotor was vented, then other not. Both the same diameter, both same size pads, both 4-pot. The difference in width would make zero difference in a low speed accident, and braking wasn't even part of it, but it was picked up on and used in evidence.

It's not about what the Gendarmes or Police spot at the road side; it's what the crash inspectors find and how the opposition party use that in evidence.

 

[Oulton Broads Anton]

Spot on Northern Sands. I really rarely sift through all this, will it, won't it, trivia. What the op needed to know is about aspect ratios, in relation to his tyres. He ultlmately would have 1 out of 4 tyres a totally different size (in width, diameter and circumference). Construction and use springs to mind. If he, per chance, happened to get involved in any incident..not related even to his tyres and there was death and or injury involved to any other party, he would be hung out to dry. Would I do what he proposes?...I'd take that risk in an emergency situation but then again why carry the wrong tyre in the first place!! JRM

 

[ambulancekidd]

I'm going to throw the proverbial spanner in the works here.
If you were unfortunate enough to have an accident, it'd be a slam dunk for the insurance to wash their hands of you.
Now imagine this accident is bad & results in serious injury or worse still a fatality, regardless of who is perceived to have caused it, you'd be quite likely to end up in jail.
It is illegal to have two different sized tyres on one axle, so the question which arises, is it really worth it just to save a few quid?