hot hubs?

[sentonist]

Hey guys! So on my week old Senton 3s, blew a tire, huge bummer. Just got a set of BFG Baja KR2 proline tires, and converted to a 12mm hex from the 14mm. I decided to convert because of the rarity of wheels with that size hex.

Anyway, out of suspicion that something might go wrong, I noticed that the center hub nut was pretty dang hot. And with my lack of experience in this, I have no idea how that area is getting so hot.

Can any of you guys lend some knowledge in this aspect?

thanks

 

[bicketybam]

Hey guys! So on my week old Senton 3s, blew a tire, huge bummer. Just got a set of BFG Baja KR2 proline tires, and converted to a 12mm hex from the 14mm. I decided to convert because of the rarity of wheels with that size hex.

Anyway, out of suspicion that something might go wrong, I noticed that the center hub nut was pretty dang hot. And with my lack of experience in this, I have no idea how that area is getting so hot.

Can any of you guys lend some knowledge in this aspect?

thanks

You lost me at center hub nut. I'm not sure what you are referring to. Help me out

 

[sentonist]

You lost me at center hub nut. I'm not sure what you are referring to. Help me out

Oh man, my bad. I meant the lug nut. So after riding my senton around for a bit, I notice the lug nut and the wheel stud are both really hot. I'm starting to suspect that the stud is grinding against the wheel

 

[olds97_lss]

If your talking about the wheel nut, could mean your bearings are shot/binding, or the new 12mm hubs your using aren't made properly for the hub and are putting a lot of side load on the bearing, which is killing them.

It's a bit of work, but usually, if you take the hub off and then put the tire on, tighten the nut and while holding the c-hub in your hand, spin the wheel slowly/gently. If there's a lot of side load on the bearing, it will feel notchy. Then if you loosen the wheel nut, you will feel it get less and less notchy feeling. That's a sign that your hub/pin isn't the right depth for your axle and it's smashing the bearing from the side.

I had that issue when putting MIP's axles on my stampede. Had to get creative with shims between the bearings so that all the load was on the inner race only when I tightened the nut.

 

[sentonist]

If your talking about the wheel nut, could mean your bearings are shot/binding, or the new 12mm hubs your using aren't made properly for the hub and are putting a lot of side load on the bearing, which is killing them.

It's a bit of work, but usually, if you take the hub off and then put the tire on, tighten the nut and while holding the c-hub in your hand, spin the wheel slowly/gently. If there's a lot of side load on the bearing, it will feel notchy. Then if you loosen the wheel nut, you will feel it get less and less notchy feeling. That's a sign that your hub/pin isn't the right depth for your axle and it's smashing the bearing from the side.

I had that issue when putting MIP's axles on my stampede. Had to get creative with shims between the bearings so that all the load was on the inner race only when I tightened the nut.

I appreciate the help there buddy, but I'm pretty darn confused as to some of the parts on there. While I was at a hobby shop, I had originally gone there for some new tires. So to get the tires, I needed to convert. So a couple things didn't work, so the guy there actually took a dremel to the back side of the hub, so that the little pin would fit through the stud, and hold it on. It seemed a little sketchy to me, since each one could be a different depth. But if the hub is wide enough to where it's grinding against the bearing, could I just take a higher-grit sand paper to it, and shorten the width just a tad?

Thanks!

 

[olds97_lss]

Wow... that's shoddy. Sounds like partly the issue is what I'm talking about and a new issue.

Typically, the hex is just thick enough to where the back of the wheel itself doesn't rub on the bearing, the hex itself, if you put it in the back of the wheel would sit flush.

So, if you grind the hex itself to be thinner, then the wheel will rub/bind on the hub.

It's one of those things that if you were talking face to face, it would be a 30 second thing to show/explain... but require 12 images and 8 paragraphs to type it out.

 

[sentonist]

Ah I see! So in your expert opinion, should I just try looking for different hubs? One of the bearings although, I'm almost certain is shot. (Sometimes I like to hold the r/c midair, and see how much the tires balloon. I had noticed that for one, they all for one have a little too much slack in it, and one of those in particular, the bearing was just moving all over the place. I'll attach some photos of what it looks like.

 

[olds97_lss]

Yeah, they went and shaved down the hex so it would fit, but now the back of the wheel is rubbing the axle carrier. My guess is that it may still be too much and is putting side pressure on the inner race of the bearing when you tighten down the wheel nut. Which is also adding to the heat issue and eventually would destroy the bearings themselves.

Like I said, hard to explain the "bearing binding" problem.

Basically, every RC I've had that had wheel nuts that thread on the axle itself, with the nut as tight as I can get it, I can physically push/pull the wheel in/out from the truck and have about 1mm or so of movement. You don't want much more or much less than that. If there's more, you take the wheel off, the hex off, the pin out, then put a shim on (thin washer). Put the pin back in, hex back on, wheel on, tighten the nut and recheck. The axle essentially floats in/out about a mm or so.

When you have the wrong hex with the relief in the back where the pin is being too deep, the pin goes further into the hex and it moves the back of the hex closer to the bearing. If it's too deep, when you tighten the wheel nut, it's smashing the back of the hex into the side of the bearing itself. Then if you push/pull on the wheel, there's no in/out movement. Radial bearings we use for RC aren't meant to have side load on them. Or at least, very little.

Too much slop has other negative effects. Causes excess wear on the output cup of the diff, allows the bearings to float around too much in the carrier which ends up causing a lot of slop, and other stuff I'm sure.

I spent 40 minutes on youtube trying to find a good video for RC's showing the issue... I'm usually pretty good at searching, but came up empty. If my bench wasn't full of revo parts right now, I'd think about taking my MIP hub off the rear of my stampede and making a short video as that's the only truck I recall having the issue on, mostly due to the design of the MIP axle not using a pin but rather flat spots and set screws. But, it was a good example of when inner race crush spacers are used and why they are used.

 

[sentonist]

Yeah, they went and shaved down the hex so it would fit, but now the back of the wheel is rubbing the axle carrier. My guess is that it may still be too much and is putting side pressure on the inner race of the bearing when you tighten down the wheel nut. Which is also adding to the heat issue and eventually would destroy the bearings themselves.

Dang.

So, being pretty broke right now, trip to the coast coming up, real anxious to try this beast on sand, is there a "cheap" alternative to somewhat fix/redneck it?

I always wondered why r/c hobbyists were broke. Now I know... lol.

 

[SrC]

I would have machined the wheel a bit if anything , not the hub/hexes at the axles. It seems that you had a parts mismatch scenario. And a Dremel used in the wrong area made things worse?

 

[sentonist]

I would have machined the wheel a bit if anything , not the hub/hexes at the axles. It seems that you had a parts mismatch scenario. And a Dremel used in the wrong area made things worse?

Well, the whole reason for the guy dremeling the hub was so that he could fit the pin in the hub, because before, it would slide on there, but it was just a hair off-center, to where the pin would not fit correctly, so he took a dremel to the back, so that the pin would fit through and hold the hub on the stud

 

[SrC]

Ok I see.

 

[olds97_lss]

A hack way to remedy it would be to put a washer on the hex before the wheel, here where I put the yellow line:

However, that diatribe I put a couple posts up about smashing the bearing may still be a problem. The back of the hub should have a .5mm collar no thicker than the inner race of the bearing so as the entire back of the hub doesn't touch the face of the bearing, which it appears yours is now doing.

Your only real option is to put a washer like I said, then get a .5mm shim behind the hex and grind the back of the hex down a bit more to allow the axle to float with the shim not allowing the hex to touch the face of the bearing.

In the end, if I saw an employee at a store doing that to someone, I'd step in and say something. That's just BS that they sell you something, modify it, then it ends up destroying your truck. Just so they could make you think they were doing you a solid and making a $3 profit off some hubs.

 

[sentonist]

A hack way to remedy it would be to put a washer on the hex before the wheel, here where I put the yellow line:

However, that diatribe I put a couple posts up about smashing the bearing may still be a problem. The back of the hub should have a .5mm collar no thicker than the inner race of the bearing so as the entire back of the hub doesn't touch the face of the bearing, which it appears yours is now doing.

Your only real option is to put a washer like I said, then get a .5mm shim behind the hex and grind the back of the hex down a bit more to allow the axle to float with the shim not allowing the hex to touch the face of the bearing.

when you say a shim, what do you mean by that?

 

[olds97_lss]

when you say a shim, what do you mean by that?

A shim is a high tolerance thin washer.

Cheap typical washers vary in size due to being stamped. Shims are made with tighter tolerances in thousands of an inch to allow you to space things precisely.

Your bearing I think (according to the manual I found) has an inner diameter of 6mm. So, you would use a 6mm shim:
https://www.rcplanet.com/rc-parts/r-c-car-truck-parts/losi-shim-set-metric-5mm-6mm-losa6356

EDIT:
Found better ones:
https://www.amainhobbies.com/xray-6x8x0.5mm-washer-10-xra962060/p358258

 

[sentonist]

A shim is a high tolerance thin washer.

Cheap typical washers vary in size due to being stamped. Shims are made with tighter tolerances in thousands of an inch to allow you to space things precisely.

ahh I see. I was a tad confused by what you meant there, since the shim I'm used to in construction is usually a wooden/plastic object shaped like a door stopper. But yeah, I'll try to stop by a hardware store by tomorrow and pick some of those up. Thanks for the help dude!

 

[olds97_lss]

You will still need to find a washer that fits on the front of the hub without being too large and interphere with the hex as well as grind the back of the hub down a bit more so you have room for a shim with a bit of play behind it.

 

[sentonist]

You will still need to find a washer that fits on the front of the hub without being too large and interphere with the hex as well as grind the back of the hub down a bit more so you have room for a shim with a bit of play behind it.

Well, I've definitely had better days. So I hadn't mentioned this yet, but right after I got the new set of tires and played around with it back at my house, the hub socket on the wheel completely stripped, I know I had it tightened down, so coming to think of it, I betcha the reason it stripped out was because of the wack hubs.

So, I know my hardware store will not have that exact dimensions of a washer, so should I just buy a slightly larger one, and dremel it down to fit correctly? I'm just trying to find the easiest and fastest way to solve these issues...

beginning to think I should've stayed with the 14mm hex and gotten another set of dboots fortress tires... only thing is I'm a huge fan of bfg tread, and the dboots had no grip whatsoever, and the new set of tires handle so stinking good!

 

[olds97_lss]

So, I know my hardware store will not have that exact dimensions of a washer, so should I just buy a slightly larger one, and dremel it down to fit correctly? I'm just trying to find the easiest and fastest way to solve these issues...

I've done that in a pinch.

 

[slick2500]

I would just buy this and call it a day. I would rather just spend $10 than try and monkey around trying to get incorrect parts to fit.
https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXHADZ