At the risk of sounding stupid

[kaustic karl]

After making repairs and getting back on the trail, I was crawling over some rock and noticed my front wheels were turning a bit faster than the rear. Is this normal, or do I have mismatched differentials? I am running the original deadbolt II rear and an injora on the front.

 

[HPIguy]

Probably has overdrive gears in the front compared to the stock rear. Common upgrade actually.

 

[Tallbump]

Yup, a common upgrade.
Not an issue at all.

Overdrive (commonly referred to as ‘o/d’) is a rock crawling thing. Overdriving the front axle makes the front wheels turn faster than the rear wheels, typically by 5% to 15%, but there are implementations out there of up to 33%!

Overdrive can be achieved by driving the front axle faster or the rear axle slower. Ring and pinion gear ratios can be changed so the difference happens on the axle at each or either end. Alternatively some transfer cases have a provision to drive the front faster than the rear, such as the StealthX transmission from Element RC’s Enduro line.

Overdriving the front helps the vehicle maintain direction on difficult climbs where traction is low. It does this in two ways:

• It lets the front pull the rear onto and through problems.
• It also maintains a low loading effect on the suspension by way of that front/rear wheel speed difference. This is thought to aid traction on rock problems, though it would be undesirable on flat, high traction surfaces.

On steep ascents without overdrive, the rear has more of the vehicle’s weight on it and so often has more traction available than the front axles. With that extra traction, the rear will work to push the vehicle forward. This hinders it from turning in whatever direction you’re steering. It’s like a slow-motion, understeer effect that is undesirable on rock problems.

 

[Tunedfrog]

At the risk of sounding stupid and for the most part I do, but wouldn't it be easier to climb if the front end was pulling the rig up
a climb than the rear pushing the rig up?
Serious question actually.

 

[Chubaka]

At the risk of sounding stupid and for the most part I do, but wouldn't it be easier to climb if the front end was pulling the rig up
a climb than the rear pushing the rig up?
Serious question actually.

If it has tge traction, yes. If the front is slipping sometimes that extra rotation helps pull up.

 

[xjtorc]

At the risk of sounding stupid and for the most part I do, but wouldn't it be easier to climb if the front end was pulling the rig up
a climb than the rear pushing the rig up?
Serious question actually.

Yep, that's essentially "the point" of front overdrive. You can also underdrive the rear end for more pushing torque.

Helps with turning too...if doing full lock donuts on flat ground is how you prefer to drive your crawler lol.

 

[Doom!]

For Crawlers it's helpful as stated above for pulling up and over when the rear has no traction. Now you really can't see a difference in performance if it's a shelf queen.

 

[kaustic karl]

That explains why the tires sound like they're dragging when tooling along on my patio. Thank you, Tunedfrog, for the explanation.

 

[Tunedfrog]

That explains why the tires sound like they're dragging when tooling along on my patio. Thank you, Tunedfrog, for the explanation.

If I helped it was purely accidentally my friend. I just thought it would be easier on the rig.

 

[kaustic karl]

My crawling area. Maybe this, plus being new to crawling, explains the breakage. Just a bunch of busted up chunks of cement that I was using as stepping stones in the yard. The yard is under going a bit of a transformation, will be using these as stepping stone again toward the end of summer.

 

[Doom!]

Hey, don't run over those poppies or your going to jail!

 

[CertifiedMike]

You had me at "sounding stupid"!

 

[kaustic karl]

Hey, don't run over those poppies or your going to jail!

My wife worked so hard to get those to grow, now I can't get rid of them.