Pinion size and wheel offset questions

[JR R]

I have a trx4 79 bronco that I added the long arm lift kit. Put the Mickey Thompson Baja pro tires on. Tires were a little tall and would bind, and fried the Titan motor. I've seen where people put in the Hobbywing fusion pro and swear by it. I ordered one, 2300kv motor. When I added the lift and went to 2.2 wheels the installation manual said install the 10t pinion, which I did. The wheels I got are 200g, wit -10mm Offset. I have a couple questions. First, should I keep the 10t pinion, or go back to the stock 11t that came on the 79 bronco without the lift when I install the Hobbywing. Second, I know I need to go with smaller diameter tires, I don't want to cut fenders because I want to keep the stock, scale look. Should I keep the offset, or change to a more stock hex? Thanks in advance for any opinions and reasons for recommendation.

 

[Cheetah928]

Me personally, I would get a motor with more tourque (such as the hobby wing) and keep the 11t. Thats what I did putting in a 540 27t motor instead. For the offset, I would first try to go back to stock, and if that doesn't work, I would go to a positive offset. My trx-4 is much different around the Fenders than yours is, but that's my thought. I basically deleted my Fenders to get a much better angle of attack. Also so I could fit the body on.

Also for the tires, maybe try a few different off sets, and maybe you'll find one that works nicely with the 2.2 tires.

 

[WickedFog]

Adding hex extenders will also add scrub steer. This will affect both your drivetrain by adding some additional stress to the components when turning, and will add lots of stress to your steering servo because of what is called scrub steer.

The further away from your kingpin (point where spindles pivot) that the tire contact patch (point where tire touches the ground) is moved, the more the tire is drug around an arc vs pivoting on the contact patch. Whereas a stock setup should be rotating the tire pretty close to the contact patch. This puts a tremendous load on the servo, especially if you turn the steering while sitting stationary.

So you want to make sure you have a pretty stout servo (lots of torque) with metal gears to handle the extra load if you run extenders. For a 1/10 crawler, torque for a steering servo is generally buy as much as you can afford. Because prices for steering servos go up depending on how much torque and speed they have.

As far as the pinion goes, that is dealer's choice, barring any excess heat generated by going too high on your pinion/tire diameter. The bigger the tires or pinion, the faster the truck will go. But it will also generate more heat.

Best thing to do is get yourself an infrared temp gun from Amazon or wherever. You can get them pretty cheap, like less than $20. Run your rig and check the temps of the ESC and motor.

For the Fusion, since the ESC is built into the motor, check the end of the motor can, which is where the ESC is, and check the front of the motor as well as the middle. You want to stay below 160°F or so.

You can run them hotter and be just fine, but I tend to stay at 160° because while driving the rig, you may pick up some grass, or a stick you don't notice right away and it could put more load on your electronics and smoke them before you know it. So staying below 160° gives you a bit of a cusion there for those kinda unforseen problems.

 

[Cheetah928]

Or you could live dangerously, and instead of a temp gun use your finger. Can you keep it on for 3 seconds and not hurt yourself? Temps probably fine. I'm totally not guilty here . You could also look into Traxxas telementry (if you don't have it already) and buy the temp sensor for it.

 

[JR R]

Thanks for that. Yes I did get the Hobbywing pro 2300kv. Probably gonna install it today. I do like the 2.2 wheels. Just need to get tires with a smaller outside diameter. The Prolines catch on the bumper and rock sliders in turns. I don't want to cut on the body because I want to keep the stock body look. With the lift on it, I think the 1,9s woul look to small for scale.

 

[JR R]

Adding hex extenders will also add scrub steer. This will affect both your drivetrain by adding some additional stress to the components when turning, and will add lots of stress to your steering servo because of what is called scrub steer.

The further away from your kingpin (point where spindles pivot) that the tire contact patch (point where tire touches the ground) is moved, the more the tire is drug around an arc vs pivoting on the contact patch. Whereas a stock setup should be rotating the tire pretty close to the contact patch. This puts a tremendous load on the servo, especially if you turn the steering while sitting stationary.

So you want to make sure you have a pretty stout servo (lots of torque) with metal gears to handle the extra load if you run extenders. For a 1/10 crawler, torque for a steering servo is generally buy as much as you can afford. Because prices for steering servos go up depending on how much torque and speed they have.

As far as the pinion goes, that is dealer's choice, barring any excess heat generated by going too high on your pinion/tire diameter. The bigger the tires or pinion, the faster the truck will go. But it will also generate more heat.

Best thing to do is get yourself an infrared temp gun from Amazon or wherever. You can get them pretty cheap, like less than $20. Run your rig and check the temps of the ESC and motor.

For the Fusion, since the ESC is built into the motor, check the end of the motor can, which is where the ESC is, and check the front of the motor as well as the middle. You want to stay below 160°F or so.

You can run them hotter and be just fine, but I tend to stay at 160° because while driving the rig, you may pick up some grass, or a stick you don't notice right away and it could put more load on your electronics and smoke them before you know it. So staying below 160° gives you a bit of a cusion there for those kinda unforseen problems.

The offset came as stock on the wheels when I bought them. Was thinking about using the neutral offset hexes from the 1.9s. Also have the traxxas high torque 600 2280 servo I'm going to install. The stock servo is weak, even for the stock 1.9 wheels. I'm not trying to make a basher out of it, just a respectable trail/crawler. I'm figuring temp got the Titan motor from the tires binding on turns. When it quit running it was hot enough to burn the finger tips at first touch, the of course it had the smell. LOL I'm totally new to RC, so learning as I go. I've got a Stampede 4x4 that's taught me a lot about break, fix, repat. Thanks for the advice.

 

[JR R]

Or you could live dangerously, and instead of a temp gun use your finger. Can you keep it on for 3 seconds and not hurt yourself? Temps probably fine. I'm totally not guilty here . You could also look into Traxxas telementry (if you don't have it already) and buy the temp sensor for it.

Yep, I wouldn't be guilty of that either.

 

[WickedFog]

The offset came as stock on the wheels when I bought them. Was thinking about using the neutral offset hexes from the 1.9s. Also have the traxxas high torque 600 2280 servo I'm going to install. The stock servo is weak, even for the stock 1.9 wheels. I'm not trying to make a basher out of it, just a respectable trail/crawler. I'm figuring temp got the Titan motor from the tires binding on turns. When it quit running it was hot enough to burn the finger tips at first touch, the of course it had the smell. LOL I'm totally new to RC, so learning as I go. I've got a Stampede 4x4 that's taught me a lot about break, fix, repat. Thanks for the advice.

Cheetah gave some good advice with the touch thing. I meant to add that, but ran a bit long already with my post. But yeah, if you can lay your finger on the electronics for a few seconds, you should be ok. Unless you're like me. I grab hot stuff right out of the air fryer and my kid just looks at me like I'm crazy. My fingertips are nearly dead, so I stick with the temp gun