odd tyre on one wheel

[PCshedman]

I noticed that my spare is a 215/80 x 15 and the :nenauother tyres are 235/75 x 15. Would it be illegal to use the spare?

 

[lacroupade]

I noticed that my spare is a 215/80 x 15 and the :nenauother tyres are 235/75 x 15. Would it be illegal to use the spare?

Not that big a deal but best to keep it as a spare only.

75% of 235 = 176.25, while 80% of 215 = 172, which means the side walls are slightly different in height between the two tyres. OK its not much - just under 1cm on the overall wheel height, but thats like driving with one tyre slightly deflated.......

 

[DEE]

Be fine to get you out of trouble. But thats all. Drive about with it to much and the old bill with have you :doh Get origenal back on soon as puncher fixed

 

[Spook]

would fail mot (if tester spotted it).

i had a slightly bigger rear tyre on a fwd car - failed mot swoped it for spare and put in a space saver i had in boot to cover the legals:augie keepng the slight over size as my 'get me home at a decent speed' spare.:thumb2

got a local part-worn tyre dealer nearby? or one of those tyre shredder people - they're canny at spotting just legal tyres and flogging them for a few quid to keep on right side of the boys in blue, & their mates

 

[Deleted account DD]

Apart from the legal argument, the difference in size means the tyres react differently to each other under load.

Negligible under min load, more apparent as you load em up :naughty "unbalanced" axle + towing or @ speed

Good way of considering this is to consider why space savers (shite that they are) are limited by speed (and mileage ? ) Just ask someone who's overdone a space saver what theyre like :augie:augie:augie

 

[PCshedman]

Interesting answers -thanks! Also interesting is that it passed MOT when visible mounted on tailgate!

 

[Deleted account DD]

Interesting answers -thanks! Also interesting is that it passed MOT when visible mounted on tailgate!

Some MOT testers are as confused as everyone on some points. When a tyre is stored as a spare its ok to have it a different size (think space saver) when in use the goal posts change :thumb2

 

[PCshedman]

I get your point, but intrinsically it contradicts itself! ie what use is a spare you cannot legally run?

 

[Spook]

i always thought space savers had to have the same rolling circumference? and only for abs equipped cars?
urban myth

 

[Deleted account DD]

I get your point, but intrinsically it contradicts itself! ie what use is a spare you cannot legally run?

You can run it under certain condition and circumstances. I cant remember the legislation and what have you but essentially a space saver limits itself by design to certain speeds and I seem to remember mileage and is lawful. Above those very low limits which are only designed as get you to the next tyre fitter, it'll probably pop or the car will go out of control. Therfore youve got an incentive to get a proper sized one fitted asap. Dont space savers have to be type approved too??

Fitting a nearly the same size one is unlawful and one reason (not legislated ) is that because the difference is minimal the effects of mismatched tyres will not be anything like as extreme as with a space saver and you will be tempted to continue using it.

You'll be fine until the day you really could have done with 4 matched tyres

So they say anyway

 

[Deleted account DD]

i always thought space savers had to have the same rolling circumference? and only for abs equipped cars?
urban myth

Not an expert but logically I suppose they must be the same circumference or theyd be well dangerous.

I dont know why the ABS bit would apply, perhaps thats because theyve only been around about the same time as abs has been commonplace :nenau

 

[PCshedman]

What if you had two of one size on one axle and two of another size on the other axle?

 

[lacroupade]

i always thought space savers had to have the same rolling circumference? and only for abs equipped cars?
urban myth

They certainly do, although I'm not aware of any connection with ABS - it is what it says, just a space saving thing. And I suspect the speed restriction is more about the huge impact on handling when running a spacesaver, rather than anything else. On my Honda HRV VTEC the space saver is about a third of the width of the standard tyre, so a car that would normally corner on rails in virtually all weather conditions becomes a piece of shite on bends at speed LOL

What if you had two of one size on one axle and two of another size on the other axle?

that would be operational in 2WD but in 4WD you'd get permanent transmission windup in all conditions - bad idea.