Running different sizes front to back?

[ozzymalone]

Just enquiring...recently bought my first truck 98 Gu 4.5ltr petrol/gas running Larger tyres upfront to rear....is this a normal occurence or is something strange going on?

Running Maxxis Bighorn 285 75 16r up front but only 275/65 16r (Maxxis Bighorns also) @ rear.

Any input would be appreciated as i'm left scratching my head.....

:049:

[the ferret]

Running larger Diameter tyres on the rear will cause your transfer box to wind up, making it difficult the go from 4wd to 2wd.
You should never run different sizes between front an rear., It would be fine with hubs out and in 2wd only or on a non 4x4 vehicle.
But at the moment you have 33s on front and 30s on the back, no good mate.

Cheers, the ferret.

[ozzymalone]

Cheers ferret...thought something sus was on the go....do you reckon I would have done much damage taking it out for one day in low range and a quick run on the beach in 4h?

[BearGUST]

Not ideal at all. Different size front to rear or side to side is bad news.
Side to side will cause issues with your LSD.
Front to rear will cause transfer case wind-up. Technically you should only be in 4WD on loose surfaces but still no good.

I actually had a case in a previous Technical Assistance job where a front wheel drive car (with electronic throttle) was accelerating itself, turned out it had larger tyres on the front which made the computer think the front wheels were travelling slower so it would try to accelerate the drive wheels to even it out.

[ozzymalone]

Yeah Bear it was rock driving and a bit o mud in low range. What sort of noticable effect has wind up got?

Crazy story about the ff....cracker! Hopefully the gu hasn't got the most intricate computer...no idea personally.

[BearGUST]

The wind-up is the front wheels travelling at a different speed to the rear wheels (due to their different size), however the transfer case is locked making them try to spin at the same rate. This causes wind up where evertything is twisting up and creating tension, as ferret said it can make it very difficult to disengage 4WD amongst other problems.

[ozzymalone]

Well its off the road till I can get some matching tyres to throw on the ole girl......anyone got some 285/76 Bighorns on offer?!? Lol