Underdrive overdrive question

[crazee horse]

So if you run this gearing in the trx4 and use it for trails as well do you get much more tyre wear or scrub due to different rotation?

[Inspector86]

Yes you will get accelerated tire wear along with accelerated drive line wear. I am not a fan of UD OD set ups but then I trail mostly. For rock crawling I can see the advanvges but there are also disadvantages. An UD OD set up will climb better but will also down hill and side hill worse. Just remember EVERYTHING in a set up is a compromise. You can improve one aspect of performance but it is always at the expense of some other aspect of performance. Overall I am skeptical that the advantages of UD OD outweigh the disadvantages and in the end I prefer to not go down that road.

[MaX-D]

Originally Posted by Inspector86

Yes you will get accelerated tire wear along with accelerated drive line wear. I am not a fan of UD OD set ups but then I trail mostly. For rock crawling I can see the advanvges but there are also disadvantages. An UD OD set up will climb better but will also down hill and side hill worse. Just remember EVERYTHING in a set up is a compromise. You can improve one aspect of performance but it is always at the expense of some other aspect of performance. Overall I am skeptical that the advantages of UD OD outweigh the disadvantages and in the end I prefer to not go down that road.

So would you say that strategic weight distribution on the truck is a better route to go than OD/UD for crawling?

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[Inspector86]

Personally I feel you have much better adjust-ability by adding/moving weight as necessary. I prefer a well balanced set up that will do everything well over a specialized set up like UD OD that will make an excellent uphill crawler but gives up down hill and side hill ability. I am concerned that many people are spending money on UD OD set ups because someone told them it was the trendy thing to do not because they actually need to.

[pyroM!KE]

Myself I have a sport. I strictly use it on courses that are rock wood mix. I dont have a need to go fast. In my situation OD UD is practical. Trail use I would not.. Hope this helps

[Nez02]

Originally Posted by pyroM!KE

Myself I have a sport. I strictly use it on courses that are rock wood mix. I dont have a need to go fast. In my situation OD UD is practical. Trail use I would not.. Hope this helps

Was it a drastic improvement or just slight? I'm currently running 100% rock as well. Debating whether or not to run the UD in the rear.

[Veygr]

I run rear UD gears and the difference is small but noticeable. Only UD because of the better gear mesh and to combat the little torque twist. Sidehill i do not see big difference and when going downhill i do one / two veeery easy tricks* to combat this. I move the battery from forward position (in front of servo) to stock battery place. This have much more effect then the UD gears can bring.
And in my case i do very long mountain hikes and the next trick is just sick: when i reach the peak and want to go downhill, i move the front tires back, and the back tires front. This and the battery movement will glue the truck downhill. So best of all worlds :P

[Stormin2u]

I don't trail at all, my focus is purely rock crawling. I run both ov/un for a tighter turning radius and improved climbing and it cancels out any torque twist. I haven't notice any negatives only improvements in overall rock crawling. As far as trailing is concerned I would guess the stock gearing or either ov or un but not both would be best.

[JatoTheRipper]

I think any concerns of exaggerated tire or drivetrain wear are overblown. RC's are light vehicles and on dirt, walking trails. The tires are going to spin fine until you get on high traction surfaces. Wear on tires and the drivetrain will be negligible IMO.

[chevy42083]

FYI... driving the front faster than the back (either both under and over or just one end) helps down hill too. Its like dragging the rear so it won't push over the front, keeps the chassis stretched long and low (just like on uphills).

Sidehill is only affected if its steep enough that the different in rotation speed causes a break in traction, causing it to slide sideways. Honestly, unless you are traveling a decent distance, at a big angle, AND in a straight line... any steering inputs start to cancel out any binding that causes downhill slip/slide.

I would think tire wear would be negligable on trail, do to the slip in the dirt. If you're talking sticky concrete like rock... then yea, you'd see some wear if you're running a soft compound. I'd bet most of us are looking for an excuse to try a new tire style/height/tread/compound about the time we wear them out anyways.

EDIT: Looks like Jato beat me to the main point.

[Stormin2u]

Originally Posted by JatoTheRipper

I think any concerns of exaggerated tire or drivetrain wear are overblown. RC's are light vehicles and on dirt, walking trails. The tires are going to spin fine until you get on high traction surfaces. Wear on tires and the drivetrain will be negligible IMO.

I agree, I haven't noticed any unusual wear on either tires or driveline. But my rigs rarely see top speed runs like you possibly could trailing on occasion. I've never been a trail enthusiast just a competitive rock crawler.

[Nez02]

I tossed the OD kit in the front of my sport and noticed a nice improvement in turning radius and down hilling. i may toss the UD kit in the rear to see how it works. The truck is used on rock 100% of the time.

[89lxmorepower]

I have od gears in the front of my trx4 sport and noticed it climbs a bit better and turns better as the front has a slight pull now do to spinning faster than rear. I do a mix of trail and rocks so I can see the difference. I've talked to alot of people that say it's only better to do one or the other vs both as it can increase strain on the electrical and cause it to heat it up rapidly