Overdrive gearing?

[Stan3535]

Hi there.
I currently have the stock 38/13 (2.9) gearing in both axles. I want overdrive gearing to where the front turns slightly faster than the rear. I see there is also a 43/13 (3.3) and a 36/14 (2.5) gear set. Are people going with the biggest spread in gears from front to rear or is that too much overdrive? Or will running a 2.9 up front with the 3.3 in the rear work better? This rig is purely used for slow crawling.
Thanks a bunch!

[PoorManRC]

IMHO, you want the smaller spread...
The more hardcore Competitors will run 36/14 in front and 43/14 in back. They rarely Trail with this setup, and will never run on flat, Hard Packed surfaces. That would CERTAINLY break something!!

Either way will introduce driveline stresses beyond what they were designed for. You'll NEVER see that on a 1:1 Rig!! However, our Tiny Trucks aren't pressing 3 Tons+ on to the pavement.

[Ninomaniac]

the stress thing is a bit overhyped. as soon as youre not going in a straight line all the wheels are scrubbing.

however, if changing only one axle it's beneficial to go with UD in the rear instead of OD in the front.

[OSRC]

I run OD/UD on several of my rigs. On plenty of trail runs - never had a problem. Our little trucks don't put the same stresses on drive train components as a 1:1 would.

If you are primarily doing slow speed work - go for it. Makes a heck of a difference.

[ferp420]

I never had good results with over under set up on my wraith but i crawl alot of large sheer slick granit my crawler has it and works good but i just cant get it to work for me on the wraith i do know one company the old subarus did run a over/under drive set up they had 3.7:1 up front and 3.9:1 rear they did it for the handling on graval and muddy road theres a big sticker that says never engage on dry pavement lol but they only did that for a few years but they did it

[nightcrawler48]

This post came up just at the right time for me as I was wondering which was the better setup. If one axle keeps the stock gearing, is it better to overdrive the front or underdrive the rear? and why is one setup preferred over the other?

Maybe a little off topic but a friend of mine wants to "buggy" a Wraith for some reason so we are looking at underdriving the rear and overdriving the front. The rear will have 4.8" od x 2.5" wide monster truck tires and the front needs about 96mm or 3.78" od. He wants the front tires skinny as well, somewhere between 1" and 1-1/2" wide. Not sure about this, may or may not look cool, but will be different. He is not concerned about how the tires perform, supposedly its all about looks for him.

[mewalsh100]

I started with just UD in the rear and it was a noticeable difference. I do now run OD/UD in both my Truggy and my Wraith. My suggestion would be to just try the UD in the rear and see how you like it and the gains it provides. If it's not doing as much as you'd like, then throw the OD in the front.

I wonder what the non - rc crawler would make of some of these threads!? "just try the UD in the rear..."

[mewalsh100]

Originally Posted by nightcrawler48

This post came up just at the right time for me as I was wondering which was the better setup. If one axle keeps the stock gearing, is it better to overdrive the front or underdrive the rear? and why is one setup preferred over the other?

Maybe a little off topic but a friend of mine wants to "buggy" a Wraith for some reason so we are looking at underdriving the rear and overdriving the front. The rear will have 4.8" od x 2.5" wide monster truck tires and the front needs about 96mm or 3.78" od. He wants the front tires skinny as well, somewhere between 1" and 1-1/2" wide. Not sure about this, may or may not look cool, but will be different. He is not concerned about how the tires perform, supposedly its all about looks for him.

If just doing one, go with the UD in the rear. The underdrive in the rear helps the front pull the rig more and tightens up turning radius as well. Plus, you're gearing down with UD in the back versus gearing up with OD in the front. Like I said in my earlier post, I started with the UD out back and it was a noticeable gain. I have since gone OD/UD in two of my rigs.

[Inspector86]

OD/UD axle gearing seems to me more like a tuning tool and I'm wondering why ya'll don't just play with tire stagger instead of changing gears. At least by using tire stagger you can quickly make changes based on field conditions. Just as an example, a 5" tire up front with a 4.75" tire rear would yield just over 5% overdrive on the front axle.

[nightcrawler48]

Originally Posted by Inspector86

OD/UD axle gearing seems to me more like a tuning tool and I'm wondering why ya'll don't just play with tire stagger instead of changing gears. At least by using tire stagger you can quickly make changes based on field conditions. Just as an example, a 5" tire up front with a 4.75" tire rear would yield just over 5% overdrive on the front axle.

Okay, I'm going to piss someone off I think. The scalers would go crazy if the front tire was bigger than the rear. Never seen in the real world so totally not scale man. But hey, that's thinkin' outside the box Inspector.

[Ninomaniac]

Exactly, that's yucky.

[mewalsh100]

Agreed. Tire stagger, though it would yield a result, would 1.) look silly. 2.) potentially cost more. Guessing not many people have mixed sizes of matching tires/tread laying around. As far as OD/UD being a tuning tool,it is indeed. But, once it’s done, it’s not like you’re messing with it any further.

[Natedog]

Originally Posted by Ninomaniac

the stress thing is a bit overhyped. as soon as youre not going in a straight line all the wheels are scrubbing.

however, if changing only one axle it's beneficial to go with UD in the rear instead of OD in the front.

X2

Originally Posted by OSRC

I run OD/UD on several of my rigs. On plenty of trail runs - never had a problem. Our little trucks don't put the same stresses on drive train components as a 1:1 would.

If you are primarily doing slow speed work - go for it. Makes a heck of a difference.

Yes, but ime OD or UD is perfect, more than that (combining both as in Axial SCX10 or Wraith gearing) is too much and is noticeable going down the trail and makes some obstacles too easy. OD or UD is perfect. But all out comp rig do both, it's somewhat personal preferance too.

Originally Posted by mewalsh100

I started with just UD in the rear and it was a noticeable difference. I do now run OD/UD in both my Truggy and my Wraith. My suggestion would be to just try the UD in the rear and see how you like it and the gains it provides. If it's not doing as much as you'd like, then throw the OD in the front.

Originally Posted by mewalsh100

Agreed. Tire stagger, though it would yield a result, would 1.) look silly. 2.) potentially cost more. Guessing not many people have mixed sizes of matching tires/tread laying around. As far as OD/UD being a tuning tool,it is indeed. But, once it’s done, it’s not like you’re messing with it any further.

Tire stagger is used in 1:1 mostly in racing, mud bogging, and hill climb stuff. I don't like the look and rather have same size tires with different gears.