The other day I got stuck in the mud, because the rear wheels tried to push around the front. (lucky for me I've got a diff lock, and came right out.) This got me thinking about all the times I switch back to 2X4 and I hear a (quiet) pop, and the front end seems to roll forward, as if while in 4X4 the front end has been pushed, the whole time. Well one thing led to another and I got a tape and out measured the front wheels. 23.5" (dunlops) front and 24.5" (dunlops) rear. It seems the fronts are getting pushed along.
I then went to 'Master Nyroc's' site and he says that the fronts should be a 2" shorter roll out. This would make sense in that the fronts are to have 4psi and the rear 5psi.
Now I admitt I am not smart. But help me please understand why the fronts need a shorter rolling distance? This seems like it would be hard on the drive train, or am I up in the night?
Thanks in advance.

 

What I said had no scientific calculations behind it. It just seems to work best.

Even rolling distance means no drag going straight, but hard steering in 4x4.
4" shorter or more in front means excessive drag, clunking, wear, fuel consumption etc.

It is just a mental statistic of mine, that every tire set I have ever seen or ridden that is around 2" difference doesn't drag very much, and also steers ok in 4x4. Seems to be a great happy medium. I have measured a few myself. Ridden quite a few others.

I believe this is why most tire manufacturers design their rear tires to roll a little further than the fronts. If they roll too far in back, then the tire manufacturer did not do a very good job.

This is not quite as important on a part time 2x4, but the full time 4x4 machines really need to have the right balance between no drag and easy steering.

 

i`m no rocket scientist, but if the front tires are shorter, they are going to be turning faster and it would
be pulling the quad. did that make any sense? also smaller tires= easier steering...

 

Scootdog,
It's the other way around. Shorter front tires, do need to turn faster to keep up the rears, however they are being turned by the same drivetrain as the rear ones. So they will NOT, travel as far as the rears will. (if turned at the same rpm). This causes the rear wheels to want to go around the fronts in the mud.
I now understand that having a shorter front tire makes for less steering effort, however is this hard on the drivetrain?

 

I've wondered but can never remember to check, if either the final drive ratio is different from the rear to the front or the trans gearing is different on the output shafts front to rear. The trans, although I havn't checked, should be direct drive front to rear rather than run one end through a planetary inside the case like some automotive applications, but the diffs could be geared differently.

Nyroc; what ya think? We'll have to check.