31 Front, 32 Rear

[havok011101]

Hey Guys,

I'm hoping to get some rims off ebay as part of my plan to have a couple of spares, and paint my white sunnies black.

Anyway, I'm bidding on a set that have 32" BFG muddies, can I run them on the back whilst running 31s on the front?

Will be good to see how the 32s fare if I want to go up a size for the next set.

 

[Jarh73]

You can't run different size tyres if in 4WD.

Well you can try to but it won't do much good for the tyres or your drive line.

The back tyres will have to rotate less revolutions compared to the front tyres and yet the drive train is telling both tyres to go the same speed.

At the same speed the rear tyres 32 inch will require less revolutions that theh front tyres 31 inch.

Its not a huge difference but its enough to put some loads on the system and most likely slow the whole car down as the front and rear tyres "fight" each other.

In 2WD it will be fine and in theory very slippey condtions it won't matter either.

It won't work very well it all.

Really need to have the same overall diameter.

Cheers

Justin

 

[havok011101]

Damn that's what I was thinking.

Oh well, it was the rims I was really after so hopefully the price will stay down.

Can still use them 2 at a time to paint them all black, and can try out the muddies in 2wd!!

Thanks!

 

[bmurray2250]

Jarh73 is correct, you need same size front and rear.

 

[teza h]

Yeh mate, dont even try it, it's not worth it.

 

[Davidman]

What about the scenario where you have a different sized spare, say 28 inch spare and 31 inch front and rear. For an emergency situation where a tyre could not be repaired on the spot, what sort of pressure or strain would this put on your drive train at a low enough speed to get you to either home or a tyre repair shop. I would imagine that if on the front in 2 wheel drive, not a huge issue, but what about on the back ?

Only asking because I may be in this situation for a month or two until I get a spare of the same diameter.

Also, is there such a thing as a light weight spare like you see in some cars these days. The ones that are only rated to 80 kmh or so, are usually orange or yellow and are only a couple of inches in width. Could save on weight on the rear door and possibly cost. It would also depend on if you were doing only day trips, or something longer, in which case you would want a full sized spare to be able to continue to 'play'.

Any thoughts ??

 

[bmurray2250]

Some cars have different wheels size for the spare and it is designed to travel slowly to the tyre repair shop. On a 4x4 that can dis-engage the front hubs would be ok for a short distance. On a AWD, I wouldn't risk it. Going places that don't have a town near by, I would just purchase good 2nd tyre or a new one.

 

[Davidman]

Am planning a purchase, but there may be a month or two gap in the middle where a different sized spare will be the only one available for the shorter day trips

 

[bmurray2250]

Always good to have a new spare tyre but unless you are rotating through the wheel changes it will rarely get used. If you have a good spare, you may be able to change it over with a good used tyre of zero or little cost. Food for thought

 

[Jarh73]

Left to right or visa versa (across the axle) differences in tyre diameter are not much of a problem because the front and rear diff can make up the difference in rotational speed.

As that is what a diff is designed to do allow different speeds across the axle.

If you have a locked diff it won't work, with a LSD diff as long as the difference in diameter is not huge the LSD will cope.

You have the option of 4H with a centre diff in the Pajero and that allows you to have different tyre sizes front to rear as the centre diff allows the front to turn at a different speed to the rear. Very cool set up on the Pajero in my humble opinion.

For the tyre sizes you are talking about i would not worry at all.

Cheers

Justin