Hi all, as my first post, I have a question,m I recently picked up a tidy 1985 LR 90 with 147000 miles on the clock, I needed 2 new tires on the front, as there were two matching tires, 1 on the back and 1 as a spare, so I now have 2 matching tires on the back and 2 new Grabber AT2s on the front. does that make sense? my question is this, will my having slightly different sized tires on the front and back cause any issue if the centre difflock is not engaged? (all the tires are the same 235/85 R16 size but the grabbers are bigger than the existing tires I have on there atm) or will having differerent sized tires front and back, rotating at different sizes fry the centre differential? (is the centre diff just a clutch with friction plates or is it mechanical like diffs on axles?)

I hope that all made sense

Cheers
DB

different size tyres different grip all ways taught same tyres same axle bigger tyres better tyres to the rear but that 2wd.Common sense would tell me that did tyres would cause different loads on trans so with 4wd got to be the same could be wrong mind you.

2wd you keep wheels on axles equall 4wd ,optional the same. permanent 4wd like defenders discos rr have center diff and while it will cope for a while would be best with 4 equal tyres/wheels

Better start saving for that second pair of Grabbers!

I had a think about this, and actually it should make less difference to the centre diff if the wheels were larger on the front, I had a look here: Defender2 - View topic - Defender 4x4 system info
and that cleared things up,as the front axle travels further round a corner than the back axle, the centre diff (CD) is there to remove any wind up (and as you don't have to replace the front or rear diffs on regular cars all the time, and as they do the same essential job as the centre diff, it shouldn't matter too much?). so. larger wheels on the front means that the front drive shaft turns slower than the rear drive shaft to compensate (in a straight line). thus, going around a corner, the front drive shaft would be spinning at a speed closer to that of the rear drive shaft, than if equal sized wheels were used all round. but I get that in the long run it would be best to have equal sized tires front and back, I'm gonna drive the vehicle for a year and then get it SORN and to a full strip and rebuild, replacing parts as I go, I may do bits here and there like doors, and half shafts allong the way over ther weekends....
also being a mechanical diff and not a limited slip or clutch type affair, it won't wear out nearly as quick, plus in daily driving, the front wheels are rarely exactly the same size as the rear ones either, owing to cornering, braking, load carrying etc... am I making sense there?
Cheers
DB

Sounds like you've convinced yourself

The center diff is inside the transferbox and cant see whats going on out side,so if you have bigger wheels on front or rear it just thinks your going around corners all the time,and is just doing what diff should do[where I live I am going around real corners all the time and my diffs ok]

instantsquid said:

Sounds like you've convinced yourself

Click to expand...

well, just doin' a bit of thinking, I don't want to convince myself, but coming to a conclusion through reasoned debate, but there's still heaps of tread on those older tires (Hercules Terra Trac MT), and if it won't hurt untill I get around to doing the complete refurb then I'll keep them on....

for the record, the ones on the front are General Grabber AT and the ones on the back are Hercules Terra Trac MTs..
huh I already said that didn't I......