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Deep groove radial or angular contact bearings in bottom bracket

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Deep groove radial or angular contact bearings in bottom bracket

Old 03-04-17, 02:09 PM
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Deep groove radial or angular contact bearings in bottom bracket

I haven't found any commentary on this subject on the web. Does one have a choice in whether to use deep groove radial bearings, or angular contact bearings? Or are cranksets designed for one or the other? I have a Dura Ace 9000 setup in a BB90 bottom. If there's a specific bearing that has great performance and good value, I'd love to hear about it. What bearings does Trek use for BB90/Hollotech? Thanks!

If you can answer the question above, you probably know the following. For general interest... There are two main types of ball bearings for radial thrust. One is called deep groove radial bearing. In that type of bearing, the inner race and outer race each have a groove machined (and, after hardening by heat treatment, precision ground and polished) into their outer/inner surfaces respectively. The bearings are assembled by machine, but it's illustrative to think about how you assemble them by hand. You'd place the outer race on the table, and the inner race on the table inside the outer race, and you'd move the inner race so it was off center. This would allow you to add a number of ball bearings. You would then even out the spacing on the balls. This would center the inner race, and retain it in place as long as the balls remained evenly spread out. So you'd press in a ball retainer (a "cage"), which retains balls with correct spacing. You'd do this with grease already present (NEVER run a bearing without lubricant - its very easy to gall the bearing and race surfaces). But you'd probably add a bit more grease to get the proper amount, and would press in seals. A key thing is that the inner race and outer race both are grooved into cylindrical surfaces - there is no taper on either part. While such bearings can take minor amounts of axial thrust, they are really designed to support a radial load. Further, because of the assembly method, there is space between the bearings (that is, higher load per bearing).

Angular contact bearings races are often called "cone" and "cup". The older style wheel bearings are like this. If you draw a line between the point where the ball contacts the cone, and where it contacts the cup, the line forms an angle with with a radial plane through the bearings. This angle means that the bearing can support an axial thrust AND a radial load. And because you can put in a full complement of bearings and then assemble the thing, the load per ball is lower. And you don't need to have a "cage" in the system. You typically have at least two A/C bearings installed on any spindle, with the angles opposing each other. Then, you tighten a nut or bolt (or press the stem down against fork tube spacers and tighten it). This puts a preload on the A/C bearings.

I think that radial bearings are used a lot in wheels. A/C bearings are used for headsets.

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Old 03-04-17, 02:17 PM
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You will have to have the side loading adjustable.. Yup, its essentially what a Cup and Cone loose ball bearing is.

A component not made for it is probably not suitable.


FWIW, Bullseye made a BB which was a combination of needle bearings and a row of ball bearings for Thrust..

He held the patent for the hollow tube spindle attached to the right crank arm , everyone uses these days
But his was an Internal BB and the cranks were Tig Steel , fabricated in California.

...

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Old 03-04-17, 03:24 PM
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I agree with FB. The BB design will or won't have a coaxial pre load adjustment ability. Without radial contact bearings are the norm. With it angular contact. And I don't consider the draw cap on a pinch bolted crank arm a preload device suitable for an angular bearing. Andy
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Old 03-04-17, 04:22 PM
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Enduro Fork Seals makes an angular contact bearing kit for the Trek BB90 bottom bracket. It uses a wave washer and spacers to set the preload on the bearings. RWC TREK BB90/BB95 FOR SHIMANO CRANKS

I have their angular contact GXP bottom bracket in my single speed MTB and it has outlasted all of the SRAM GXP bottom brackets I used in the past. I have had to add spacers twice, after it developed a bit of side play, but its still rolling smooth.
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Old 03-04-17, 08:44 PM
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Originally Posted by Andrew R Stewart
I agree with FB. The BB design will or won't have a coaxial pre load adjustment ability. Without radial contact bearings are the norm. With it angular contact. And I don't consider the draw cap on a pinch bolted crank arm a preload device suitable for an angular bearing. Andy
So the little plastic wrench that has a small "finger tight" torque spec and that forces the crank arm against the rubber bearing seal (the orange washer-like thing in the pic below, two of which came with my bike) is not suitable for AC preload, but rather is for radial deep groove bearing preload. I guess it should have been obvious: a thick elastomer washer is going to squeeze under the axial thrust generated by the radial force on the pedals and chainring. Although the bearings pictured below are claimed to be AC bearings by RWC!

dsaul, I think that this is what's happening: you graunch down on the pedal, which applies radial force to the bearing. The angular part converts this to axial thrust, compressing the seal. This eventually degrades the seal and gives you the symptoms you mention.

I guess I can pull my crank pretty easily and inspect, but what' I'd like to do is order the right part, and strip my bike (spring cleaning) of parts and wash it. Then reassemble with new bearings, cables, and tape. I think I'll pull the crank...

Thanks, guys!

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Old 03-04-17, 10:21 PM
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IMO a Hollowtech preload cap is adequate for angular contact bearings.
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Old 03-05-17, 04:47 AM
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To my thinking a company has done their engineering & selected the correct type of bearing for each application, so you replace the same; no need to re-invent the wheel, obviously the better quality models from good companies will have possible better specification / tolerance bearings. You can go to a large bearing supplier with a bearing number & will be offered several different manufacturers / prices all due to quality, same on tyres & everything else.

Fit whats there.
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Old 03-05-17, 11:03 AM
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Bike tinker man,

I understand your point, and as an engineer who has designed things, feel that a change to a well-considered design should not be undertaken lightly. But I think everyone here has probably changed things on their bike. From deviating from the stock tires to changing (in my case) the seat, and the handlebars. To your point, sometimes those changes have proven idiotic in retrospect (my own choices have sometimes). Anyway, "Man's reach should exceed his grasp, or what's a heaven for?"

I'm going to chat with Wheels mfg tomorrow. They sell both deep groove and AC bearings for the BB90. They claim that the ACs are the oem item. I'll report back anything I learn.

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Old 03-07-17, 01:00 PM
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Originally Posted by Kimmo
IMO a Hollowtech preload cap is adequate for angular contact bearings.
I just noted you were upside down, Kimmo. Does that affect the seal?

More importantly (and less tongue-in-cheekly), do you have experience in doing this?
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Old 03-09-17, 03:22 AM
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Originally Posted by WizardOfBoz
More importantly (and less tongue-in-cheekly), do you have experience in doing this?
If that was the case, I'd have typed IME rather than IMO.

But I just ordered an angular contact thread-together BB86 BB designed for Hollowtech II cranks for a customer. So Wheels Manufacturing concur.
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Old 03-09-17, 10:34 AM
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Originally Posted by Kimmo
But I just ordered an angular contact thread-together BB86 BB designed for Hollowtech II cranks for a customer. So Wheels Manufacturing concur.
Ah, so we are both experimenting. Report back, and I will, too.
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Old 03-10-17, 10:31 PM
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Originally Posted by WizardOfBoz
Ah, so we are both experimenting. Report back, and I will, too.
I'm pretty sure there's no worries about adequate preload here, or Wheels Mfg wouldn't have done an angular contact variant of their Hollowtech II BB (IIRC there are normal radial and ceramic versions too).

And furthermore, it seems readily apparent to me that adequate preload can be achieved via Shimano's end cap and thumbwheel tool, since it's possible to put more than enough preload into Shimano's own radial bearings like that.

When I do up a Hollowtech II crank, I wind on more than enough preload to ensure it's fully seated, then back it off and come at it again like normal. If I just left it with as much preload as I could put in with the tool, you can see it's too much preload when you spin the cranks. I'd hazard that amount of tension on the preload cap would be too much for angular contact bearings also.

The BB arrived, but bugger it, I assumed it used a standard BB tool. It's a larger diameter than that, waiting for the Wheels Mfg tool now. Hope I can get away with just having one, since it only screws into itself...
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Old 03-11-17, 10:23 AM
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I bought the cheap wheels mfg bb tool - 35 bucks. Comes with two drifts, the all-thread rod, and two handles. I'm going to buy four SS washers and two PTFE (Teflon(R), I hope since I'm a former DuPonter) to use as low friction bearings. Quite frankly, two nuts, two washers (maybe a third one - a large diameter fender washer) and a short length of two by four with a hole in it would proabably work just almost as well.

I'm going to try this today.

Are the Shimano OEM parts AC or radial? Or does Shimano even make an OEM BB90 bearing? The one think I'd like to see would be a seal (by which I mean the washer that installs outboard of the bearing, but inboard of the crank arms on each side) that would have a stainless ring on the ID to allow for a rigid spacer so that your preload would remain and would not be diminished by cold-flow of the elastic (which can happen with the current all-rubber setup).

Last edited by WizardOfBoz; 03-12-17 at 09:32 AM.
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