Car Wheel Size Variants.

[cumbriasteve]

Googling is providing mixed guidance/opinion.

I understand the basics of differentials and gearing but there are members here with much more knowledge than me on the subject ....so....

My space saver spare wheel arrived today and it is approx 40 to 50mm smaller diameter than the normal wheel and tyre, it is however the correct item and anything larger would not fit in the allocated boot space.

Now I don't see that as a problem on the independent free running rear wheels, the one with the space saver will simply do more revolutions but wonder about the front drive wheels.

Some suggest it's fine, the car handbook makes no reference to fine or not which sort of suggests fine and some suggest in the event of a front tyre puncture a double change to ensure the space saver is on a rear wheel.

Normal practice would be drive a short distance to the depot and get the tyre sorted but in a worse case scenario it may have to cover 80 miles with no chance of finding a tyre depot open to repair and replace the original.

Will the diff happily compensate for the size difference without any issues/damage or is the double change a must do .

 

[dcocks]

The diff will sort it out, only time it would be a problem would be on a permeant 4x4 car

 

[Fazerruss]

Although not answering your original question I would recommend buying one of these kits....

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/183466372665

They are brilliant and I don't why I didn't get one sooner.
6 weeks ago I got a puncture on my Suzuki Grand Vitara and my brother repaired it with one of the above without even removing the wheel. It took all of 10 minutes and it's not lost a whiff of air in nearly 1000 miles.
I just pulled out the screw and shoved one of these in. Bob's your mother's brother.

 

[rtbcomp]

The diff will sort it out, only time it would be a problem would be on a permeant 4x4 car

Even then the axle diff will sort it out, although it could be a problem with limited-slip diffs and axle lockers.

 

[steveo3002]

Although not answering your original question I would recommend buying one of these kits....

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/183466372665

They are brilliant and I don't why I didn't get one sooner.
6 weeks ago I got a puncture on my Suzuki Grand Vitara and my brother repaired it with one of the above without even removing the wheel. It took all of 10 minutes and it's not lost a whiff of air in nearly 1000 miles.
I just pulled out the screw and shoved one of these in. Bob's your mother's brother.

yeah theyre good ..rarely give any trouble

 

[slim_boy_fat]

I can only assume the recommendation for switching over to ensure it goes on the back should you have a front wheel puncture, is for possible imbalance of the amount of grip, steering wise?

 

[gaz_moose]

on a regular run of the car it will be fine.
if you have a fancy plated type LSD it will wind the diff up
probably knacker you up if its a permanent 4wd.

I think the concession is not to drive like a total tit with a skinny space saver on the front.

 

[steveo3002]

if its to pop home 5 mins then use it , if you have to do 100s of miles then it would be worth the 10 mins to fit it to the rear

 

[8ob]

Although not answering your original question I would recommend buying one of these kits....

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/183466372665

They are brilliant and I don't why I didn't get one sooner.
6 weeks ago I got a puncture on my Suzuki Grand Vitara and my brother repaired it with one of the above without even removing the wheel. It took all of 10 minutes and it's not lost a whiff of air in nearly 1000 miles.
I just pulled out the screw and shoved one of these in. Bob's your mother's brother.

Oi

I use them all the time, supposedly a temporary repair but I just leave them in and have had no problems. You also need a compressor but that said the kit plus compressor take up a lot less space than a wheel and jack.

 

[Anguz]

wonder how abs deals with the reduction is size?

 

[Robotstar5]

On my MGZS I had no options if I had a front tyre go, I had to swap with a back wheel as the steel spare wouldn't fit over the front disc/caliper.

 

[CompoSimmonite]

You need one of these tyres -

 

[cumbriasteve]

Some good comments and advice.... thanks folks.

I will certainly get one of those kits, keeping the small supplied compressor in the dish of the spacesaver so would be a belt and braces scenario.

 

[zx9]

Oi

I use them all the time, supposedly a temporary repair but I just leave them in and have had no problems. You also need a compressor but that said the kit plus compressor take up a lot less space than a wheel and jack.

In your line of work I expect you often have need for one of those kits. I have had the rubber plugs fitted by my local tyre place but they broke the bead to see how much damage had occurred inside the tyre before fitting and re inflating. Looking at the position of that repair they may have refused to do it, it does look very close to the side of the tread.

 

[ibrooks]

Normally the advised pressure for the space saver is far higher than for the proper tyres which makes them run far closer to their outer diameter. It's also normal for the manufacturer to specify that they should only be fitted to the front (double change for a rear puncture) and that they are for a strictly limited distance and speed. You'll often find this marked on the wheel itself and they are supposed to be a different colour to the standard wheels (hence often red or in the case of my Mazda buff but if the car came with alloys then black satisfies the rules).

A diff will handle a degree of mismatch but it's working harder hence the speed and distance limitations (less of a concern on a rwd car but they'll have the same advice). You'll almost never see a 4x4 with a space-saver, they'll have a proper wheel or a can of goop.

The reason for putting them on the front is "safer" handling with the reduced grip. The front end sliding is usually easier for an inexperienced driver to recover or cope with than the rear end. Same reason that it's generally advised to put the newest tyres on the rear (they are assuming that new tyres have more grip over an average of real world siuations).

Cars with abs will either "know" how to recognise and cope with it or they won't come with a space saver. I have seen manuals that have a specified routine for you to go through when fitting a space saver that are effectively you telling the abs about it (combinations of buttons or settings in the menu system).

 

[ibrooks]

Regarding the tyre plugs shown....... they ain't legal for UK road use. Insurance and liability minefield so use black ones and hide the kit so you can say it was like that when you got it and you didn't spot them when doing checks.

The "proper" mushroom type are legal when fitted by a "competent" person but you need to take the tyre off or mostly off to fit them and they can't be fitted too close to the sidewall as the head just peels off if it's exposed to the flexing of the sidewall.

 

[8ob]

"Legal" "illegal" tyre repair is a load of cods. There are recommendations and some tyre companies work to some kind of tyre institutes guidelines. Not saying they dont make sense but a string repair on a tyre thats just had a nail in it is not illegal or dangerous. Not recommended is not illegal.

http://www.dexel.co.uk/blog/british-standard-tyre-puncture-repair/

bob

 

[Bill Edwards]

The string repairs are brilliant and do a permanent job with minimal time and effort, but like most things there are things they can't do:

Slits - they'll deal with a hole but if it's a slit they'll usually come out at some point.
Sidewall - they can slow a leak down but don't expect it to work properly and don't expect it to last.
Shoulder - sometimes people get away with it, but don't trust it.

One problem with them is that the tyre can suffer damage from being run flat and this is not seen without taking the tyre off to look inside.

Personally I'd always choose a spare wheel over a string and compressor or a can of sealant. Aside from the sealant making a mess inside the tyre for the poor sod who has to deal with it later neither method will repair a large puncture, sidewall damage, blowout or rim damage.

 

[fizzy]

Although not answering your original question I would recommend buying one of these kits....

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/183466372665

They are brilliant and I don't why I didn't get one sooner.
6 weeks ago I got a puncture on my Suzuki Grand Vitara and my brother repaired it with one of the above without even removing the wheel. It took all of 10 minutes and it's not lost a whiff of air in nearly 1000 miles.
I just pulled out the screw and shoved one of these in. Bob's your mother's brother.

Yes these kits work but to be honest tyre weld will sort these problems as well unless it is a big hole in the side wall.
I was stranded last month - they were late changing my hire car - def Sat they said - then it turned into Monday. Sunday night I get a puncture 40 miles from home. No spare of course. Yes the tyres were pretty low on tread - what I hadn't noticed was the wire poking through on the very inside edge! Had to be recovered home and then have a mobile fitter come to the house the next day!
Even a space saver is better than nothing!
One advantage of very low profile tyres - you hardly notice a blowout. My Land Rover would have been leaning over at 45 degrees!

 

[cumbriasteve]

Right...I think I may be sorted, I now have....

A space saver.
The manufacturers gunk and compressor.
A string repair kit.
A torch for finding the nail.
A pair of pliers for pulling out the nail.
A stanley knife for cutting off the excess string
A bit of foam to kneel on.
An old coat in case it's raining.
An old cap in case its still raining.
An extended socket bar for the nuts the garage windy hammered on.
Wet wipes for cleaning the hands.
Old towel for drying the hands.
First aid kit for scuffed knuckles when jacking the car.
A puncture aerosol (given by a mate and forgot I had).
A fancy red flashing warning thing (given to me by the same mate).
A fire extinguiser, well it was cheap and looks good.
RAC recovery.
10mpg less due to the weight in the boot.

I can't help but think if I witnessed any other person with that much I would consider them insane.