Rear axle crush tubes/spacers?

[Mochanic]

I'm confused... again, LOL.

I have RPM 70272 carriers with the 3/16x1/2x.196" bearings which fit perfectly into the carrier, but there's not mention of what crush tube/spacer to use. I measured the exact distance between the bearings and it's .107" on 1 side and .112" on the other side. I've seen where people say to use the B4 spacer #7377, but there's no way that's gonna fit, it's way longer than that (I don't have one to measure, but from the looks at all the pictures I have seen it's longer than it the ID is wide and the ID is .187".) There is no mention from RPM about a spacer, but I know it needs one because when I tighten the axle nut the wheel gets pretty tight and hard to turn, this wouldn't happen with spacers.

Any ideas?

[Sixtysixdeuce]

Don't bother. They aren't necessary. The spacers only prevent bearing preload; just don't shim too tight.

[Mochanic]

I understand they will work without them, but I feel they will work better and allow for tighter axle nuts, and less slop if they were there. There is good reason that all the factory kits come with them.
I just need help determining if there are any direct fits for the RPM carriers or not. I sent RPM an email but still have not heard back from them yet.

[Sixtysixdeuce]

I feel they will work better and allow for tighter axle nuts, and less slop if they were there.

The wheel nuts tighten down on the wheels, which in turn seat against the axle pins. Unless the slots in your wheels are too deep, torquing the wheel nut will never load the bearing (unless you crank them so hard you bend the pins). Adding the spacers will do nothing for play. Moreover, there needs to be end play, with or without spacers. You do not preload them like you would the tapered pinion bearings on a 1:1 car. Conventional symmetrical ball bearings as found in RC cars will fail prematurely if preloaded.

[Mochanic]

Found a part number that will work!
9751 are exactly what you need to put between the bearings for the RPM rear carriers. They are .110" thick, with an id of 3/16".
This will be exactly like the original T2 setup and almost every other carrier that has a crush tube from the factory.
I feel they are needed, otherwise they wouldn't have bothered putting them in any of the RC's.
Remember the axle are shimmed with washers behind the pins to take out any side to side slop. So any pressure on the pins at all squeezes the bearings together which causes the axle to bind up.
After installing these spacers there is zero slop and zero binding.

[jwscab]

I hear people say this all the time and it kind of irks me. It's not a 'crush' tube. it's simply a spacer. A crush tube is used in automotive differentials in order to provide a cheap and effective way to preload tapered roller bearings on the pinion gear, and the installation 'crushes' the tube from a nominal length.

it could technically be called an 'anti-crush' tube. Unless you use the B4 style conical spacers such that any thrust from the wheel face is directed into the inner race, those spacers are not effective anyway. even with shims behind the pin, over-tightening the wheel will bend the pins, forcing them into contact with the wrong part of the bearing and additional drag, not to mention possible snapping the hardened steel pins. If using shims on the pin side, you are probably driving the shims into the face of the wheel, deforming it in the process.

not singling you out, BTW, just see/hear information sometimes that need a little correction. If you are tightening the wheels snug and not over doing it, it's perfectly fine to have the spacers in there, but they will not technically be doing anything unless preloaded.

[Mochanic]

Guess you should call team associated and tell they need to get it right because they is exactly what they call it. http://www.teamassociated.com/parts/details/9751/ While you're at it tell their engineers they don't really need them and that they are just wasting money by putting them on >95% of every RC they have ever made!

I know it's just a spacer, I have a degree in automotive technology and have been working on cars professionally since 1992. I called it a crush tube/spacer because that is what they call it and I'm just trying to avoid confusion.

Regardless of what it's called, it WORKS 10 times better with it in place.
I am using the conical washers that were included with the HPI wheels that do in fact push on the inner race like they should which is exactly why the spacers need to be there so they transfer the load to the inner race and onto the axle that also loads the inner race.

I really don't care if you personally use them or not, I'm just letting everybody know that if you want to make it like stock when using the RPM hubs carriers then you need the 9751 spacers which are a direct unmodified fit.

[scr8p]

are these the hpi washers you are talking about?

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXN060&P=FR&gclid=CIvpxYyM8LwCFW3NOgodRSoAmw

[Mochanic]

are these the hpi washers you are talking about?

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXN060&P=FR&gclid=CIvpxYyM8LwCFW3NOgodRSoAmw

I'm guessing they probably are. Mine came with the wheels, so I don't have an exact HPI part number, but they do look the same.

[scr8p]

and you are using them between the pin and bearing?

[SnoopMaxx]

Those HPI spacers are used between the wheel and locknut

[scr8p]

oh yeah, i know where they are supposed to go. but unless i'm reading it wrong, it doesn't sound like that's where he put them.