Trx4m understeer

[Tucky]

I’m slowly building this truck and I can’t figure out the understeer problem. It just pushes the front tires and then I end up throttling through the obstruction and get off course. I have 59mm injora shocks with no springs and 35wt oil, injora diamond +4mm axles, rubber band limit strap 74mm DJ crawler tires with solid brass wheels and 72mm injora comp pins in brass wheels and they both do it.
Any ideas on how to fix this?

 

[diezel666]

Unless the TRX4M has changed sine I first looked at them...
What you're experiencing, is normal. This effect is due to all 4 wheels turning at the same exact speed. The transmission front and rear output shafts are spinning at the same rate to each other. The front axle and rear axle have a "spool" type diff, which is completely locked. Thus, all 4 wheels turn at the same speed.

I only know of only three ways to counter act this:
1: Driver Mod: Set yourself up tighter through an obstacle, knowing you're going to push off course.
2: Add more weight to the front and remove weight from the rear. So the front has more traction to pull the rear end. This effect won't be as strong as it could be since the front and rear spin wheels at the same rate.
3: Replace the diff, IIRC RC4WD makes an axle set (front and rear) that has an Open Diff or Spool (locker) option.

 

[Tucky]

Oh I do have the overdrive and underdrive gears in the diffs as well. I'll see if I can shift any weight more forward and see if that helps. If thats just the way they are then I'll just live with it I guess, I just bought a Capra and I will shift my focus to that as it seems like a much better truck for what I want to do with it.

 

[skurge]

Oh I do have the overdrive and underdrive gears in the diffs as well. I'll see if I can shift any weight more forward and see if that helps. If thats just the way they are then I'll just live with it I guess, I just bought a Capra and I will shift my focus to that as it seems like a much better truck for what I want to do with it.

i would double check and make sure you installed them correctly, you may have the overdrive in the rear, that would explain it also. it shouldn't be pushing its front around no matter the weight if you've got overdrive already

 

[Tucky]

i would double check and make sure you installed them correctly, you may have the overdrive in the rear, that would explain it also. it shouldn't be pushing its front around no matter the weight if you've got overdrive already

I will check when I get home in the morning but I’m pretty sure they are correct but I have been wrong before

 

[skurge]

I will check when I get home in the morning but I’m pretty sure they are correct but I have been wrong before

i've done it before myself lol

 

[Tucky]

i've done it before myself lol

I had the front and rear switched . The bags they came in were labeled F and R but I didn’t look at them to confirm that they were correct.

 

[diezel666]

I had the front and rear switched . The bags they came in were labeled F and R but I didn’t look at them to confirm that they were correct.

That will def help some. I should have noted the OD/UD being helpful in my original post.

The laws of physics still apply. Both front wheels are turning at the same speed, and the outer tire (in relation to the steering angle) should be turning faster than the inside tire, or one encounters push of the front end towards the outer tire since both tires are trying to cover the exact same distance. Which in a turn is not the same distance for the inside vs outside tire.

Same physics are still at play, no matter the scale: front locker potential problems

 

[skurge]

I had the front and rear switched . The bags they came in were labeled F and R but I didn’t look at them to confirm that they were correct.

happens to everyone hah! glad you figured it out