rear axle bearing spacer

[jrt]

I asked Bob to cut me a rear wheel bearing spacer based on our discussion here:

http://www.v11lemans.com/forums/index.php?showtopic=5537

see about page 3ish.

Bob is either the spiritual leader of a freaky church but he's also my father in law, a good machinist, and an absolute motorcycle nut (He's into Vincents though...I'm working on him).

So here's pictures of the first spacer he made up:

 

Nice composition with the fruit and bread

 

Slightly beveled ends for Baldini

 

It says '$3.50 material, 1/2 hour @$17.00, $21.50 + S/H"

I think he should charge more, but that's just me. Just curious if anyone know what the MG part costs?

 

Dimensions are 113.04 mm (4.452") long X 25.2 (.9945) outside X 20.37 (.8) inside. Wall thickness is 2.51 mm. It is made of either 2024 or 7075 aluminum (I'll have to ask). Both are high grade aircraft aluminum.

We calculated that the side load on the tube will be ~2-3000 psi. That's waaayyy below the stress limit for this part.

 

Now, I do NOT have time to drop my rear wheel and remove the bearings to make sure this fits. It will if the dimensions I was given are correct. Who wants to be the guinea pig? Anyone working on their bearings?

Jason

[dlaing]

SNAP!

I'll take one, por favor!

(Thanx for going with aluminum)

FWIW the cheap aluminum spacer that I made seems to holding up well, and has not gotten mashed down under torque enough to cause problems.

I just pulled the rear wheel last night, after a thousand miles and the spacer was firm but moveable between the bearings, and the bearings turned like new.

I used an aluminum that is probably less than half as hard or strong as the rated alloys, so the high grade aluminum alloy should have no problem.

[al_roethlisberger]

I don't need one now, but I'd like to get one just in case.... especially at that bargain price

 

 

I can't buy it now though, as with the coming move(in a week)... I can't receive shipments or even think about ordering stuff right now.

 

But if you can "put me on the list" and ping me in September when done(and I'm all moved), I'll get one from you.

 

al

[beauchemin]

Has anyone actually measured the distance between the bearing-shoulders inside the hub of the rear Brembo wheel? If we can expect this distance to vary from wheel to wheel, then doing a production run of the spacers will be pretty much impossible -- won't it?

[jrt]

Well, that was quick. On its way to David already.

 

beauchemin: Yes. I worry about that a little bit. On the flip side, I would hope that the hub and maybe the whole wheel is a standardized run from Brembo.

 

 

Al, I'll be happy to take more money. Any extra goes to Jaap as a donation and/or to Bob for his efforts. I personally think Bob should charge 25 bucks, and that's what I will give him for mine.

 

J

[gh67]

Sweet! jrt, count me in. I've got my front wheel off waiting for my bearings to come in (hopefully today) and will be changing the rears in a few weeks. Though, I'd vote for dlaing getting the first off the line....he's had more spacer experience to compare the new one to. Thanks for making this happen!

[dlaing]

Sweet!  jrt, count me in.  I've got my front wheel off waiting for my bearings to come in (hopefully today) and will be changing the rears in a few weeks.  Though, I'd vote for dlaing getting the first off the line....he's had more spacer experience to compare the new one to.  Thanks for making this happen!

57564[/snapback]

Thanks, GH,

Unfortunately, I am not great at measuring

But I'll be sure to report on the fit.

The worst thing is that now I have to trash one of my bearings....

But a small cost for safety.

I am sure the 113.04mm is fine for me and many others, but you might just recommend that people measure before ordering.

For those that did not follow the thread, the distance between the bearings has been measured by Gio to be between 112.6 and 112.7, and I believe Baldini measured it at 112.8mm.

We never totally agreed on how much freeplay is acceptable, but if your distance between is around 112.6 and 112.8 I believe we agreed it should be fine to make the spacer 113.0x mm.

The OEM spacer was too short at about 112.4-112.6. I measured with a wood ruler Yours may vary!!!

The spacer MUST be longer than the distance between the bearing seats.

Thanks Jason, Bob, and all those who contributed with posts!

[beauchemin]

The spacer MUST be longer than the distance between the bearing seats.

57589[/snapback]

 

Why? If the distance between the seats is 112.8, and a 113 spacer works, then a 112.6 spacer should also be fine. It's within the same tolerance that a 113 spacer is.

[jrt]

No, the spacer has to be longer than the distance between seats, otherwise the bearings will take the side load (rather than the bearing race taking the side load).

 

Some of this is just unsubstantiated argument and I would like to end it definitively by getting an accurate measure of the distance between bearing seats.

David- go buy a damn set of calipers. Even the plastic ones work pretty good and they cost like $1.50. Seriously, I'll pay for 'em. Or borrow a nice digital vernier from from your fancy machine shop. When I was at CalTech, I was always bothering the machine shop to make some hoopty part for me. They enjoyed it because it was a break in their routine.

[dlaing]

We covered it in the other thread in 9 pages.

But since it is sooooo important, I'll try to explain here.

You have to visualize what is happening to the inner and outer races when the axle is torqued.

Point one, the spacer will compress under torque, and if it is too soft it will deform.

Regardless, the tolerance of the bearing is less than a tenth of a millimeter, so if the spacer is a tenth short, the torque from the axle nut will put damaging pressure on the bearing.

In the other direction, if the spacer is longer, you can torque it till the threads strip and it will not damage the bearing. We never really covered the implications of it being too long,

I suppose the wheel could shift enough to cause the rotor to scrub the pads, but one or even two millimeter longer, should not be a problem, because the bearings are seated pretty well and the force to shift the wheel would have to move both bearings in their seats simultaneously.

While it would theoretically be ideal to never have freeplay for anything, the real world needs freeplay.

Things expand and contract from temperature and other forces.

Back to point one, if you torque the axle nut to ten foot pounds, then torque it to spec, think about what is happening. The metal is deforming. The axle is getting longer and the bearing spacer is getting shorter, as evidenced by the bolt moving along the threaded axle.

This is why some prefered steel to aluminum, and it is also why we need freeplay.

But the grades of aluminum that Bob specified should do the job as the hardness and strength of these tubes exceed that of many steels.

[dlaing]

David- go buy a damn set of calipers.  Even the plastic ones work pretty good and they cost like $1.50. 

57619[/snapback]

I looked and they were all over $20!!!!!!

I'll check Home Repo, I mean Home Depot.

[jrt]

http://www.harborfreight.com/cpi/ctaf/Disp...temnumber=47257

16 bucks

 

http://www.harborfreight.com/cpi/ctaf/Disp...itemnumber=7914

dolla-ninety nine

 

[dlaing]

http://www.harborfreight.com/cpi/ctaf/Disp...itemnumber=7914

dolla-ninety nine

57644[/snapback]

...and six-ninety nine for shipping

I'll find something to measure it with.

It is my duty to the Guzzi community.

[belfastguzzi]

Nice composition with the fruit and bread

'$3.50 material, 1/2 hour @$17.00, $21.50 + S/H"

 

57544[/snapback]

bit pricey for a bread roll

 

Just curious if anyone know what the MG part costs? 

57544[/snapback]

I was quoted about £16

 

but then, it's a real classy part

[belfastguzzi]

I'll find something to measure it with.

 

57653[/snapback]

 

 

I could lend you a piece of string

though I don't know how long it is

 

someone out there must know

then we'd really be getting somewhere