My new Mayhem ST is only a few tanks past break in, so I've been able to nail the throttle recently.

The right front will come off the ground and the truck will veer off to the right under heavy throttle. It is a very upsetting condition. With the right front coming up, the tire is free to baloon, and then it re-grips momentarily as it swells and causes a vey unstable handling condition.

The wheel nuts are on strong and there is no stripped wheel.

Checking the diff action (Mayhems have factory silicone diff fluid):

front: If I raise the front only, and spin the right front, the left front will rotate opposite. If I rotate the left, the right rotates opposite. Action seems slow, but I guess that is a product of the fluid. Slight diff clicking is heard. I guess all seems ok.

rear: Repeating the above test on the rear produces similar results, but it sounds just a tick quieter.


I'm lost. If the front had issues, how the heck would it come up on one corner? Could the issue be in the rear? Is this issue of one corner coming off the ground indicitive of a common problem?

Is this just a result of the wheels coming up and the diff action?

From this I would believe the problem is within the suspension. Whether it would be spring height differences, spring differences or shock oil differences I'm not sure. I would check this over as suspension is a probable cause.


I don't quite understand this too well. The tires need speed in order to balloon. While the tire is off the ground it doesn not gain speed. Although I do know ballooned tires do cause very unstable driving.

This is just the characteristics of how a differential works. I do not believe the problem has anything with the differential. Does the mayhem use a ball diff or a gear diff?

Ryan

OK basically i think what is happening is there is to much weight transfer. The weight transfer is just to much If the wheel comes off while turning then the left front spring is to soft. Try putting preload spacers or the colars on so the spring is a bit more stiffer.

But if your not turning then the weight trasnfering is to the left rear which would allow the right front to come up. Again make the left rear spring stiifer by either the preload spacers or by putting the colar down on the shock shaft. Basically you need the weight to stop trasnfering to the left. You could try taking off the load from the right rear. Which would allow the rear to squat evenly and would do a wheelie instead of just bringing the right front up.

And yes if you have 4WD the wheel with the least amount of weight will get the most power. Thats how all 4wd vehicles work yes even our 1:1 scale unless you have possi (in 1:1) or you have a locked differential. If you have 4wd without the diff being locked then if you grab the one wheel and hit the gas that wheel will not move. That means that the power is being given to the other wheel.


Another words if you grab the left rear power will be transferred to the right rear and the left front. The power always goes diagonoly. Another words a 4wd without a diff lock isnt really 4wd it's more or less 2wd if you pick up the truck and hit the gas yes all 4 wheels will spin but grab the left rear and then hit the gas it wount give you any resistance and you can go ahead and grab the right front to along with the left rear and all the power will go to the opposite wheels and should not give you any resistance. That how 4wd works unless again you have the diff locked.


well i hope this helped in some way. shane

Hmm....I think you guys are on to something. I noticed it when I was on asphalt, and prior to that the truggy was used on grass, where it handled much much better.

I'm thinking that on asphalt, the rear is squatting, as usual, but the tires are really hooking up (suspension is set soft). The front comes up, but not totally even -- the right is up more.

I am going to at least stiffen the whole setup, and stiffen rear to keep it from squatting too much. I want to see how it is when the front wheels stay in better contact with the ground.

Notes:

>my comment about the diff spinning was just to let you know they looked ok and felt okay doing the wheel spin test.

>the tire balooning: When the right front comes off the ground, I'm sure all the tires are balooning a bit by that point, but since the right front is off the ground it gets a little taller than the rest of the tires.

I think my key is to keep the wheels in contact with the ground under heavy accel, which I will try by stiffening the suspension and maybe putting a little more stiff bias in the rear for anti squat.

If you put heavier diff oil in the center it will transfer more power to the rear and the front tires will not balloon so badly. I had the same problem with my st and changing the oil helped a lot .

Well, some stiffening helped a little. I stiffened the rear and front, but made the rear stiffer. The back still tends to squat more, so I might increase it a bit.

My last runs: On asphalt, the steering pull was less dramatic, but it did fluctuate between a mild to modest left and right pull. Now, I am not big on running on asphalt, but sometimes that is what is around. I prefer grass and dirt where she seems happier.

The front wheels have a little negative camber and some slight toe in, if that matters. Rears are toed in more, plus more negative camber than the fronts.

I am tempted to make the fronts a slight 'toe out' setting.

Thoughts? Feedback?