Bearing life?

[Ouiji Veck]

Changing my front tire w/ 31K mi and was thinking better "check" the bearings..

maybe better just replace 'em huh?

Easy enough job, just hate to pay $$$ for them when I just need

to go down to the bearing shop and look the guy in the eye and lie..

" uh......there for the winch @ the boat yard" and get 'em for $8.00 ea.

[Guest ratchethack]

Say Weej -- this might just be me, but if they don't feel rough, why bother?

 

Unless they get conaminated, run dry, or suffer the dreaded crushed linguini-spacer horrors , they can go for hundreds of thou miles. . .?

[Ouiji Veck]

I'm with ya ratch. Pulled the front wheel and they're as smooth as a baby's bumm.

Just gettin' antsy leavin' for Newfoundland a week from this Fri.

I suppose if I get stuck up there in the nether regions of Quebec I'll just have

to find a mademoiselle to put me up 'till the Fed-Ex truck arrives.

[pete roper]

I'm with ya ratch. Pulled the front wheel and they're as smooth as a baby's bumm.

Just gettin' antsy leavin' for Newfoundland a week from this Fri.

I suppose if I get stuck up there in the nether regions of Quebec I'll just have

to find a mademoiselle to put me up 'till the Fed-Ex truck arrives.

 

Or simply go to the nearest workshop and ask the owner to order you a couple. Biff 'em out and give them to him, he orders them in and you install. better than $700 and a tow!

 

I always wash bearings out before installing 'em. Pop out a seal from one side with a small screwdriver and wash the crappy then silicone grease out and re pack 'em about 2/3rds full with bearing grease and pop the seal back in. Install with the removed seal side inwards on the wheel.

 

Wheel bearings only work at comparatively low speeds and really high loads are unusual, they should last for ages unless they overheat. What causes overheating? Usually lack of lubricant!

 

Pete

[raz]

I always wash bearings out before installing 'em. Pop out a seal from one side with a small screwdriver and wash the crappy then silicone grease out and re pack 'em about 2/3rds full with bearing grease and pop the seal back in. Install with the removed seal side inwards on the wheel.

Are you saying you do this to brand new bearings? Why? The grease they come with is so bad?

[pete roper]

Two reasons. 1.) I don't like the silicone type grease used in most 2RS bearings nowadays. 2.) There is never enough of it. If they put an adequate sufficiency of decent grease in there when they sealed 'em you'd never have to buy another one . No, that isn't strictly true but if a rolling elemant bearing is correctly packed and sealed it will last a very long time.

 

Remember, sealed bearings shouldn't be packed *full*. If you do that there is nowhere for the grease to expand as the bearing warms up so it will pop out the seal. Also too much grease will prevent the rollers or balls from turning so they will skid producing rapid wear. There is always an element od skidding in a rolling element bearing, (The outer race is longer than the inner one so the rolling element has to skid as it turns on one of the races.) havind grease in there enables this to happen with less friction and that friction that there is has it's heat disipated effectively by the correct amount of lubricant.

 

Pete

[Guest ratchethack]

. . .There is always an element od skidding in a rolling element bearing, (The outer race is longer than the inner one so the rolling element has to skid as it turns on one of the races.)

. . .

Pete

Thanks, Pete.

 

In all my years of fiddling with motors and replacing bearings, I'd never considered this.

 

Now that you mention it, it occurs to me that without considerable skidding 100% of the time -- in other words, if they worked like planetary gears, hard-meshed on their inner and outer races -- ball and roller bearings would be permanently locked-up.

 

No wonder the little devils get so testy when they run out o' their favorite salve!!!

[Ryland3210]

Two reasons. 1.) I don't like the silicone type grease used in most 2RS bearings nowadays. 2.) There is never enough of it. If they put an adequate sufficiency of decent grease in there when they sealed 'em you'd never have to buy another one . No, that isn't strictly true but if a rolling elemant bearing is correctly packed and sealed it will last a very long time.

 

Remember, sealed bearings shouldn't be packed *full*. If you do that there is nowhere for the grease to expand as the bearing warms up so it will pop out the seal. Also too much grease will prevent the rollers or balls from turning so they will skid producing rapid wear. There is always an element od skidding in a rolling element bearing, (The outer race is longer than the inner one so the rolling element has to skid as it turns on one of the races.) havind grease in there enables this to happen with less friction and that friction that there is has it's heat disipated effectively by the correct amount of lubricant.

 

Pete

 

I beg to differ. The fact that the outer race is longer than the inner is no cause for skidding. For example, with the radius of the grooves slightly larger than the radius of the balls, and absent side thrust, the contact between the balls and both inner and outer races will be along a line along the middle of the grooves. The only sliding motion is therefore along the sides of the groove, which is lubricated in the minute gap between the balls and the side of the grooves.

[Guest ratchethack]

I beg to differ. The fact that the outer race is longer than the inner is no cause for skidding. For example, with the radius of the grooves slightly larger than the radius of the balls, and absent side thrust, the contact between the balls and both inner and outer races will be along a line along the middle of the grooves. The only sliding motion is therefore along the sides of the groove, which is lubricated in the minute gap between the balls and the side of the grooves.

ACK!@#$%&

 

Now my brain is locked-up!

 

Must. . .resolve. . .or. . .forever. . .be. . .lost. . .in. . .doubt. . .

 

Now this thinking would of course account for bearings' endless appetite for clean, high-grade lube -- same as skidding of the rolling elements.

 

But wot of the example where the balls would be hard-meshed to inner & outer races? Isn't this an impossibility WRT rotation as Pete has suggested due to unequal circumferences of races, or, assuming the only contact is at the center of the races (as you've said, John), is it rather not an impossibility because each ball handles the ratio of inner & outer circumferences equally??!!

 

Now that I think about it (Part II), planetary gears in a differential don't lock up! Therefore, no skidding under ideal, center-race-only contact?!

 

Somebody help!

[Ryland3210]

ACK!@#$%&

 

Now my brain is locked-up!

 

Must. . .resolve. . .or. . .forever. . .be. . .lost. . .in. . .doubt. . .

 

Now this thinking would of course account for bearings' endless appetite for clean, high-grade lube -- same as skidding of the rolling elements.

 

But wot of the example where the balls would be hard-meshed to inner & outer races? Isn't this an impossibility WRT rotation as Pete has suggested due to unequal circumferences of races, or, assuming the only contact is at the center of the races (as you've said, John), is it rather not an impossibility because each ball handles the ratio of inner & outer circumferences equally??!!

 

Now that I think about it (Part II), planetary gears in a differential don't lock up! Therefore, no skidding under ideal, center-race-only contact?!

 

Somebody help!

 

 

Here's a way to look at it that may help: Imagine that the groove radius is ten times that of the balls, so you can clearly contemplate the balls contacting both inner and outer races along a line around the circumference of the balls in the ball rotation plane, similar to the planetary gear setup. There is no skidding as the balls roll around. It may be easier to visualize if the outer race is stationary and the inner rotates.

 

If the groove radius were exactly the same as the balls and there were no lubrication, the contact would be along a line transverse to the ball rotational plane. In that case, there will be sliding motion everywhere along that line of contact except at the bottom of the groove. However, grooves with radii slightly larger than the balls prevent that transverse line metal to metal contact, so the lubricant can do its job.

 

Hope that helps.

 

Signing off for now.

[Guest ratchethack]

Here's a way to look at it that may help: Imagine that the groove radius is ten times that of the balls, so you can clearly contemplate the balls contacting both inner and outer races along a line around the circumference of the balls in the ball rotation plane, similar to the planetary gear setup. There is no skidding as the balls roll around. It may be easier to visualize if the outer race is stationary and the inner rotates.

 

If the groove radius were exactly the same as the balls and there were no lubrication, the contact would be along a line transverse to the ball rotational plane. In that case, there will be sliding motion everywhere along that line of contact except at the bottom of the groove. However, grooves with radii slightly larger than the balls prevent that transverse line metal to metal contact, so the lubricant can do its job.

 

Hope that helps.

 

Signing off for now.

I understood that part the way you do first pass, John. It's the idea that skidding is necessary as Pete first suggested, which at first made sense to me -- until I thought again about planetary gears -- that's got me cerebrum a bit wrapped around the ol' driveshaft. . . .

 

I'm thinking now that under ideal conditions, that is, no side loading, but only center groove contact and assuming all balls contact both inner and outer races, there IS NO SLIDING AFTER ALL....... agreed?

 

Nevermind. You've said as much above by my analysis.

 

Thanks.

[raz]

Still confused, but on a higher level

[dlaing]

I suppose if I get stuck up there in the nether regions of Quebec I'll just have

to find a mademoiselle to put me up 'till the Fed-Ex truck arrives.

Braking down in the nether regions of Quebec might be a problem.

But if you can make it to an auto part store, there is a good chance they will have the bearing in stock.

Here is a list of bearings that you can translate to Quebecois, print out and carry along with your volume of Guzziology(that might already have the numbers).

http://www.geocities.com/rcdlaing/v11bearings.htm

But you can always tell the mademoiselle that the bearings have to ship from Italy or from some boutique bike shop in boston, while you borrow the rafters in her garage to hold the bike up. Hopefully you will be out of there by the time the EPT results come back

Bon voyage!

[Guest ratchethack]

Still confused, but on a higher level

How about this, then:

 

Do tapered roller bearings necessarily have to slide to some degree -- all the time?

[pete roper]

Actually I think Ryland has me nailed on this one

 

I spent a few hours thinking about it last night, he's right, I'm wrong. The explanation I gave was how it was explained to me at tech all those many years ago and I never gave it that much serious though, it seems logical. The problem is of course that while the inner race does a full revolution to return to it's original position the balls or rollers won't remain in the same orientation to either the inner or outer races so the same element won't of returned to the same place in relation to either race.

 

The fact remains though that rolling elements DO scuff, there is also the rubbing motion betwixt the element and it's cage, or, in the case of crowded rollers, the contra-rotation against the adjacent rolling elements.

 

Good to be forced to put the old grey matter to some use occasionally. Thank you ryland, I stand corrected!

 

pete