# DIY external bottom bracket bearing tool?



## pwrtrainer (Oct 23, 2005)

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## bad mechanic (Jun 21, 2006)

Buy a blind bearing puller. You can buy them all day long for about $70 on eBay.


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## PissedOffCil (Oct 18, 2007)

A blind bearing puller is fine for taking the bearings out but not so much for pressing new ones back in.

If I remember correctly, I saw someone who used a headset cup,a rod and washers to take it out using a vice. Pushing new ones in is easier, you only need a vice and washers.

P.S. The Hope tool on CRC isn't too expensive. FSA does a cheap one too.


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## bad mechanic (Jun 21, 2006)

Pressing the new ones in is easy. Take one of the old bearings and remove the bearings and inner race (punch the ball retainer out). Then take the outer race, and put it on top of the out race of the new bearing, and then wrap a piece of tape along the outside to keep them together. Then, simply tape in the new bearing with a hammer, making sure to only hit the taped on old outer race. As the bearing is pushed into the place, the tape will be pushed off the new bearing.


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## pwrtrainer (Oct 23, 2005)

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## bad mechanic (Jun 21, 2006)

pwrtrainer said:


> I found a puller on harbor freight for cheap. Can I use it to also pull the bearings out of my frame pivots?


Yes, so long as the collet fits.


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## sanjuro (Sep 29, 2004)

This is another classic "There is something so special and unique about bicycle repair" situation.

I realized this when I tried to pull my bearings from my Kona Dawg, which has 4 rings. I estimate it would have taken me 2 hours. 

My friend took it down to his transmission shop buddies, and they did the whole job in 15 minutes. 

There is nothing special or unique about bearing replacement. The only thing you have to be sure when you buy tools from Harbor Freight is make sure you get the right size collets, since most industrial bearing tools are much bigger.


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## pwrtrainer (Oct 23, 2005)

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## tomacropod (Jul 23, 2004)

The Australian company DIYmtb (diymtb.com) makes a tool kit for removing and reinstalling Bearings from external BB cups. It's well made and very quick and easy to use.

- Joel


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## Mount Dora Cycles (May 29, 2009)

bad mechanic said:


> Pressing the new ones in is easy. Take one of the old bearings and remove the bearings and inner race (punch the ball retainer out). Then take the outer race, and put it on top of the out race of the new bearing, and then wrap a piece of tape along the outside to keep them together. Then, simply *tape* in the new bearing with a hammer, making sure to only hit the taped on old outer race. As the bearing is pushed into the place, the tape will be pushed off the new bearing.


typo.

Good advise on using tape to hold them together, never tried that. I usually use a small bolt and washer through the bearing to hold it while tapping in but like the tape idea better. Old dogs can learn new tricks.


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## ettore (Nov 13, 2004)

There is a thread on here to resurrect External BB bearings without removing them ... the idea was that the bearings themselves are quite robust, but the seals and the grease are dookie.

Thread is here: Click Me


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## LyNx (Oct 26, 2004)

Ding, ding, ding, we have a winner  I've used this method so many times it isn't funny, even works with the cups in the bike (actually for me that makes it easier). Take a look at my trance bearing replacement guide for ideas, also check out Speedub.nates headset press where I originally got the idea for the frame presses. http://forums.mtbr.com/showthread.php?t=130069



PissedOffCil said:


> A blind bearing puller is fine for taking the bearings out but not so much for pressing new ones back in.
> _*
> If I remember correctly, I saw someone who used a headset cup,a rod and washers to take it out using a vice. Pushing new ones in is easier, you only need a vice and washers.*_
> 
> P.S. The Hope tool on CRC isn't too expensive. FSA does a cheap one too.


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## pwrtrainer (Oct 23, 2005)

ettore said:


> There is a thread on here to resurrect External BB bearings without removing them ... the idea was that the bearings themselves are quite robust, but the seals and the grease are dookie.
> 
> Thread is here: Click Me


Yeah, I have done this already, but the left bearing is beginning to need servicing more frequently so I would like to replace the obviously subpar bearings with better ones like enduro or something...


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## LyNx (Oct 26, 2004)

Actually I believe it is a design flaw of the Shimano external BB cranks :skep: Even after replacing the stock bearings with good Enduro SS ones I still have to keep an eye on the left/non drive side bearing :madman:



pwrtrainer said:


> Yeah, I have done this already, but the left bearing is beginning to need servicing more frequently so I would like to replace the obviously subpar bearings with better ones like enduro or something...


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## pwrtrainer (Oct 23, 2005)

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## bad mechanic (Jun 21, 2006)

LyNx said:


> Actually I believe it is a design flaw of the Shimano external BB cranks :skep: Even after replacing the stock bearings with good Enduro SS ones I still have to keep an eye on the left/non drive side bearing :madman:


I've had excellent luck with Enduro bearings, and contribute this to three reasons:
1. The Enduro bearings use bigger bearings.
2. The Enduro bearings are better sealed with both a primary and secondary seal with grease in between. It works MUCH better than Shimano's system.
3. The Enduro bearings are simply higher quality. Shimano uses VERY cheap bearings.


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## PissedOffCil (Oct 18, 2007)

LyNx said:


> Actually I believe it is a design flaw of the Shimano external BB cranks :skep: Even after replacing the stock bearings with good Enduro SS ones I still have to keep an eye on the left/non drive side bearing :madman:


I'm not sure it has to do with the fact that the left side is more subject to grime, although it probably plays a part. My explanation is this:

The non-drive side is subject to higher load than the drive side since the cranks transmit the load directly to the bearings. On the drive side, the chain helps alleviate some of that pressure, which is why they don't wear out as fast.

Maybe I'm wrong and someone can deny this... ISIS BB didn't have this problem, I wonder why...


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## bad mechanic (Jun 21, 2006)

PissedOffCil said:


> The non-drive side is subject to higher load than the drive side since the cranks transmit the load directly to the bearings. On the drive side, the chain helps alleviate some of that pressure, which is why they don't wear out as fast.
> 
> Maybe I'm wrong and someone can deny this... ISIS BB didn't have this problem, I wonder why...


I'm going to disagree. The new through axle cranks are stiff enough where I doubt the bearings are seeing much difference in force. But even if they are, the drive side bearing would see higher load. The chain isn't alleviating any force, it's what is helping produce it.

Yeah, an ISIS BB would grenade it's bearings all at once. ISIS had a serious issue with undersized bearings.

My guess as to why your left bearing is causing more trouble is either an unfaced frame, or you simply got a bad bearing.


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## PissedOffCil (Oct 18, 2007)

Hum. I've got 3 bikes with ext BB and all 3 develop left bearing wear faster. I also repacked multiple Ex BB for friends, the left side always wears faster.

Let me explain my supposition a bit more. On drive side, since the chain is there, it stiffens the axle/bearing interface, thus putting less stress on the bearings. On the non-drive side, when you puh the pedal, the axle pushes directly on the bearing, thus wearing the balls more.

This is all supposition but it seems to make sense. The drive side doesn't put as much load on the bearings since the chain prevents the axle from pushing too hard on the bearings, it distributes the load through the chain and through the whole frame.


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## bad mechanic (Jun 21, 2006)

Again, the chain is what is applying the load, and that load will be supported by the bearings. It's that whole "to every action there is always an equal and opposite reaction". The chain is also incapable of stiffening anything, as it's flexible both up and down and side to side. Sorry man, but look somewhere else for your answer.

If anything, the left side would wear faster because it's less protected from contamination.


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## pwrtrainer (Oct 23, 2005)

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## PissedOffCil (Oct 18, 2007)

bad mechanic said:


> Again, the chain is what is applying the load, and that load will be supported by the bearings. It's that whole "to every action there is always an equal and opposite reaction". The chain is also incapable of stiffening anything, as it's flexible both up and down and side to side. Sorry man, but look somewhere else for your answer.
> 
> If anything, the left side would wear faster because it's less protected from contamination.


Well since the chain links the crank to the rear wheel, you need to flex the whole chainstay to apply an equal load on the bearing instead of simply applying a given load on the NDS crank... Sure the chain is applying a load, but not to the bearings, rather to the rear wheel, no? If it really was a matter of contamination I wouldn't see the effect of the roadie where it's barely a factor.

I might be imagining things but I'd really love to see numbers on this matter since I'm sure it has to play a role. Again, I insist that this as always been a hypothesis and in no way can I back it up.


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## bad mechanic (Jun 21, 2006)

PissedOffCil said:


> Sure the chain is applying a load, but not to the bearings, rather to the rear wheel, no?


No. If the chain is applying a load to the rear wheels, it's also applying a load to the BB bearing. Again, that whole "to every action there is always an equal and opposite reaction".

Does the road bike ever ride in the wet or rain?


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## LyNx (Oct 26, 2004)

Whatever it is, I also experience the same thing as Cliff and that's over 3 bikes - all with M760 XT HT2 cranks. Hasn't mattered which bearings either, just the Enduros last a bit longer.


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## bad mechanic (Jun 21, 2006)

PissedOffCil and LyNx, was the BB shell faced on the bikes having the bearing issues?


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## PissedOffCil (Oct 18, 2007)

bad mechanic said:


> No. If the chain is applying a load to the rear wheels, it's also applying a load to the BB bearing. Again, that whole "to every action there is always an equal and opposite reaction".
> 
> Does the road bike ever ride in the wet or rain?


Not really, no. Of course there is an occasion here and there but now that I have a trainer, it'll probably be never again.

Some were faced, other's weren't...
If it was a facing problem, I see no reason it would always affect he left side bearing unless it has to do with the spindle being attached to the right crank arm?


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## LyNx (Oct 26, 2004)

UH, let's see, no, yeah, think so.



bad mechanic said:


> PissedOffCil and LyNx, was the BB shell faced on the bikes having the bearing issues?


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## rbyoung2007 (Jun 21, 2010)

PissedOffCil said:


> Not really, no. Of course there is an occasion here and there but now that I have a trainer, it'll probably be never again.
> 
> Some were faced, other's weren't...
> If it was a facing problem, I see no reason it would always affect he left side bearing unless it has to do with the spindle being attached to the right crank arm?


yep, very true.


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## froggy97 (Oct 16, 2009)

*Pissedoffcil, maybe it's mechanics*

as in biomechanics.

The idea that the drive side is going to wear faster than the non-drive makes no sense. The pedals are directly connected. It's how force is applied.

However, we all favor one foot over the other. It's a fact of life that one leg is dominant over the other. Just as you'd favour a leg for kicking, you do the same thing on a bike. Some people crunch down with their left leg, instead of the right. I was a kinesiology student 15 years ago

With clipless pedals this is actually accentuated. The dominant side generates the bulk of the force (even if only 51/49) by having the advantage of weight. Even when pulling up there is still a counter-force on the opposite side (basic newtonian physics) The leverage against the bottom bracket spindle will work on one side of bearings more than the other. The dominant side uses that side's bearings as the fulcrum, whereas the weaker side doesn't apply as much pressure on the opposing crank

This was quite common back in the day when BBs had a spindle two cups and two races and you were dealing with sprinters. The new crank systems are much better than the old cup and races, but there is still that element of dominance in the pedal stroke.


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## PissedOffCil (Oct 18, 2007)

froggy97 said:


> as in biomechanics.
> 
> The idea that the drive side is going to wear faster than the non-drive makes no sense. The pedals are directly connected. It's how force is applied.
> 
> ...


Quite possible and I think I've got a stronger left than right leg, but this unequal wear was also visible on friends bikes. Could we all have a stronger left? Seems like a weird coincidence, or maybe it's more common.


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## froggy97 (Oct 16, 2009)

This is a cool puzzle. We know it happens, but why?

Maybe it's "handed-ness"? Assuming you're right handed. That's your stronger arm. When you pedal hard it's your left leg that works with your right arm. Same Idea as what I said before but it makes more sense since most people are right handed.

Bad Mechanic brought up a good point about the chain. The non-drive side will have downward force more concentrated than the drive side. *The chain tension would pull the spindle aft, and the rear hub forward*. The force would be distributed across a greater arc section of the bearings on the DS than the NDS.

Pulled from Dirtrag
[COLOR="Blue".....This is exactly what happened with Shimano's Octalink V1 and V2 systems and the open-standard, co-operatively developed ISIS interface. Both of these splined systems offer greater spindle strength with Q-factor measurements similar to square taper systems, but at the price of bearing durability. The smaller bearings are more susceptible to dirt, require more precise tolerances and simply wear out faster than square taper systems in practical use for a large number of riders.[/COLOR]

While the actual reason is a bit of a mystery, its a bigger problem now because of the smaller bearings needed for external BBs. Or we just learn to accept a larger Q-factor and ride bowlegged

I don't have any answers, just enjoying the speculating


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## bad mechanic (Jun 21, 2006)

froggy97 said:


> Maybe it's "handed-ness"?


Very frequently a right handed person's left leg will be stronger since it's the plant leg. However, I doubt a leg would produce so much more power as to reduce bearing life on that side.



froggy97 said:


> The non-drive side will have downward force more concentrated than the drive side. *The chain tension would pull the spindle aft, and the rear hub forward*. The force would be distributed across a greater arc section of the bearings on the DS than the NDS.


This I don't really agree with. Unless the inner race is going to appreciably deform (and I don't see that happening with the tight fit of the axle), then you won't be loading the bearing over a larger area from DS to NDS.


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## froggy97 (Oct 16, 2009)

So then what is your hypothesis for the phenomenon?

_Originally Posted by bad mechanic
No. If the chain is applying a load to the rear wheels, it's also applying a load to the BB bearing. Again, that whole "to every action there is always an equal and opposite reaction".

Does the road bike ever ride in the wet or rain?_

Again, the load applied to the bearing is being distributed over a larger arc. It has nothing to do with ovalizing. You just don't get it.

You're also not considering the fact that the pedals are oriented 180 from each other. BM, when the NDS side is concentrating the force downward, the DS is pulling up, which drives the NDS harder. The chain tension negates the aft-ward force on the DS.

The two sides are connected but not symmetrical. If they were there would be chain running forward from the NDS to the front wheel. So you have an imbalances of forces, which translates to premature wear.

{assumption} it sounds like you visualize the bearings in question to be simple annulars. Most bearings used on bikes have an offset contact angle for obvious reasons. A cup and cone bearing is around 45 degrees to handle both axial and lateral loads. The loading on a crankset happens in two planes, and so does wear.

I don't mind being challenged, but a hypothesis would be nice, rather than just being a contrarian.


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## bad mechanic (Jun 21, 2006)

No, the load isn't being distributed over a larger arch. Imagine two equal forces pushing on the spindle, 180 degrees apart from each other. Is the force distributed over a larger arch? No, because the forces sum to zero. If you have a force pushing down and a force pushing back, they're going to sum to a force pushing at a diagonal. Unless the spindle and inner race are deforming, the bearing only ever "sees" one force.

An imbalance of forces doesn't immediate translate to premature wear, provided the forces are within the operating specs of the bearings. One bearing doesn't know what the other bearing is doing; it only knows the forces it sees.

The bearings used in an external BB are deep groove radial cartridge ball bearings (which are a type of annular bearing), which are ideally suited for radial forces, and capable of dealing with some axial loading as well.



froggy97 said:


> You're also not considering the fact that the pedals are oriented 180 from each other. BM, when the NDS side is concentrating the force downward, the DS is pulling up, which drives the NDS harder. The chain tension negates the aft-ward force on the DS.


Does this make sense even to you? :skep:


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## froggy97 (Oct 16, 2009)

force vectors? you've got an additional force vector on the DS. There isn't the equilibrium that would negate the forces.

It's basic physics. Bicycling Science from M.I.T. Press authors Whitt and Wilson, it explains this completely.:madman: Though, if you don't understand that you don't have a net zero with the force vectors I think it'll be over your head. But given your interest in bikes it's worth picking up.

If the net force was zero then there is no work being done. And the bike doesn't move. Therefore there has to be an imbalance on the pedals to move the bike. The two bearings while bridged operate independatly

If you're claiming that it's a net zero system and the bike can still travel forward you have no grasp of physics. The vector induced by chain tension moves the radial vector back about 45 degrees. There is no equivalent tension on the NDSYou brought up the chain and now you're arguing against it? Forget listening to me, *you aren't even listening to yourself
*
This started as a fun mental exercise, but life is too short. You just don't get it. I'm sure you are talented in other areas but basic physics isn't one of them. This isn't even Newtonian, we're talking Archimedes simple!!!


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## bad mechanic (Jun 21, 2006)

You have completely, utterly missed the point. While I'm using a simple model to illustrate that multiple vectors sum to one vector, you're taking that simple model *as* my argument. I mean...wow. :lol:

Careful, a couple more slip ups like that, and you'll get kicked out of your precious _intelligentsia_.


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## PissedOffCil (Oct 18, 2007)

Calm down folks...

I gotta get that bike physics book!!!


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