tyre size differences

[newbie2]

hi all, i have noticed that the tyres on the front of my surf have a bigger diameter than the tyres on the back, will this be ok or could it cause any transmission problems ?

[Maverick]

I'd imagine that a tyre size difference from front to back would give the same results as slightly different diff gear ratios.

I remember when Tony was changing the ratios on the black bullett he could use 4wd because he'd done the back diff but not the front, and enguaging 4wd would result in the rears being driven at a different speed from the fronts.

I'd advise not using 4wd until you find out iff I'm correct, or you have the tyres changed.

[Maverick]

Hold on a second, wheren't you the person that had the rears lock when you tried 4wd?

If so this might be your problem (as long as I'm thinking correctly).

[NiftyNev]

If so this might be your problem (as long as I'm thinking correctly).

You are.

Nev

[NiftyNev]

hi all, i have noticed that the tyres on the front of my surf have a bigger diameter than the tyres on the back, will this be ok or could it cause any transmission problems ?

What's the size of front and back tyres?

Nev

[newbie2]

fronts are 31x10.50r15 and the rears are 215sr15

[Growler]

fronts are 31x10.50r15 and the rears are 215sr15

Is there another number in between the 215 and 15

Should be something like this 215/70/SR15

The middle number generally denotes the tyres diameter in metric terms, which is what may be causing your problem

[newbie2]

i thought that was odd to but no there is not.
but roughly the front tyres are about 1-2 inch bigger in diameter and width than the back tyres, could this be a problem ?

[Growler]

i thought that was odd to but no there is not.
but roughly the front tyres are about 1-2 inch bigger in diameter and width than the back tyres, could this be a problem ?

The width is so much of a problem, other than stability. The main problem is that you have, as you say, nearly 2 inchs difference in the diameter. This will have the same effect as having different ratio's in the front and rear diffs and cause serious wind up in the transmission as you have already found out.

I would suggest that you don't use four wheel drive until you get a set of 4 matching tyres on the truck.

[newbie2]

but as im not supposed to use 4wd on my 2nd gen unless on loose or slippery surfaces because of transmission wind up i would have thought that aslong as i stick to that rule that even if i was using different size tyres front and back that i wouldnt get wind up due the wheels spinning on the slippery surfaces i would be driving on.
or am i missing something ?? obviously im just guessing here.

[Maverick]

But you're forcing one set of wheels to travel at a different speed to the other. Effectively either fronts or backs will always be wheel spinning, which will give you no grip and wear the tyres and drivetrain out. Also if suddenly all four tyres find grip you could find yourself with an expensive repair bill.

[123-gtt]

i sold my scooby to a mate and told him not to use spare wheel if he gets a flat,due to it being 1" smaller anyway he did, and the bill was 1300 quid matching sizes is a must on 4x4s,

[newbie2]

ok thanks guys, i will get some 31x10 asap.

[123-gtt]

think so???

[newbie2]

??