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PostPosted: Wed Feb 22, 2017 11:56 pm 
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I have a Trek with a BB90 carbon shell bottom bracket. The BB bearings are a slip fit. Grease is the normally all that is needed. Unfortunately the bb shell has become ovalized to the point that there is play in the crank - I am able to slightly rock the crank arms. Trek is recommending loctite as the solution but I wonder about coating the shell with loctite and then pressing the bearings in. Won't the loctite squish up and all over the inner seal of the bearing as it is pressed in? My fear is that loctite could find its way in around the edges of the bearing seal and seriously interfere with the function of the bearing once it has set.

I am curious about people's thoughts on this. Or are there better solutions?

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Posted: Wed Feb 22, 2017 11:56 pm 


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PostPosted: Thu Feb 23, 2017 12:28 am 
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Your fears are well founded. I had an FSA Mega BB I was trying to get creak free once, and that's exactly what FSA suggested... a retaining compound between the cups and bearings themselves. It was a long time ago when not many folks were using retaining compounds and it was my first time as well. Got the rather expensive Loctite 609, and basically I made a mess of things. The retaining compound did indeed get mixed in the grease of the bearings themselves and made a huge mess. Got new bearings in the end. Live and learn.

Also, make sure you use a retaining compound like Loctite 609, and NOT a threadlocker such as Loctite 222 or 242. Different things for different applications.

So, if you go the retaining compound route in your BB90 shell, the way I would go about it is to:
1) Get both Loctite 609 and the appropriate primer (may want to use 638 instead of 609 in your case with slipfit where the gaps are bigger). Most of the time I'm working with an interference pressfit so Loctite 609 is better for small gaps. The primer is needed since you are using it with an inactive material, in this case the carbon shell.
2) Make sure the BB shell is squeaky clean as well as the outside of the bearing surfaces. Apply primer to both the inside of the BB90 shell and the OUTSIDE of the bearing surface.
3) Apply the retaining compound to the outside of the bearing surfaces only, and sparingly, so the when you push it in the shell, any excess won't get trapped behind and end up in your bearings as it would if you applied the retaining compound to the inside of the BB shell surface as well.
4) Have a rag handy so that you can quickly wipe away any retaining compound that may get squeezed out the sides as you push the bearings in.
5) Install crank and let it set up for a day before riding.
6) Keep fingers crossed, do special dance if you have one, and whatever other good luck rituals you deem worthy but don't want to discuss over the internet.

I am curious... what crank and BB are you using here? Shimano? If so, I think sometimes people don't get the preload adjusted properly from the get go which allows for some play in there. It's hard to know just how much preload there should be with that system. I tend to want to overtighten a bit, to make sure you take up any slack, then back off a smidge so it's not jamming stuff, kind of like you would do if you were adjusting a cup and cone wheel bearing.

I have an Emonda and run Campy with it. I have not experienced any issues with the BB90 shell, and I think part of that may be due to the fact that the bearings on Campy Ultratorque cranks are pressed onto the spindle itself, and when the ultratorque crank is all locked into place, those bearings stay pretty aligned with the crank making it difficult for the bearings to get askew at all within the shell. I have not had to resort to anything but grease in the shell itself, and not a peep or any play.

Also, make sure it's not just really worn bearings that are creating the play, versus an ovalized shell. The feeling of play could be caused by that as well.

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PostPosted: Thu Feb 23, 2017 3:03 am 
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Thanks Cal,

As always, a fountain of useful info.

Applying the loctite to the outer races of the bearings instead of the shell seems to be the way to avoid contamination - good tip.

The problem is unrelated to sideload, or faulty installation, or brand of of BB. I can only get play in the crank when I have it at the 12 and 6 o'clock positions. At 3 and 9 it is rock solid. The shell is ovalized on the vertical axis which is what you would expect from wear. And there is absolutely no play laterally so sideload is more than adequate. Using Sram as at happens. I have the same set up on another Trek which has and alloy sleeve in the shell. No play at all on that bike.

I have also heard that trek has slightly oversize bearings for bikes that are, or end up out of spec. I think it would be my preference to go this route if it meant I could still use grease. Using loctite means I can't take things apart and clean quickly and easily.

This is yet another example of why press fit, slip fit, etc. is such an inferior design. This problem could ultimately render this frame unusable (something you demonstrated in an earlier post). No one should be surprised by this. Using grease facilitates movement which leads to wear.

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wheelsONfire wrote:
When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.


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PostPosted: Thu Feb 23, 2017 5:04 am 
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I would suggest downloading a copy of Cannondales Pressfit BB30 Bonding Instructions which wouyld serve as a good 'primer' on how this is done. Having used the primer and Loctite 609 to install BB86 bottom brackets on the older Giant TCR Advanced SL (alloy insertsin bottom bracket shell), Scott Solace (BB86 w/carbon BB shell) as well as our BB30 cross frames, I would say that if the retaining fuid is getting into the bearing seals, then you used too much retaining fluid. I applied it by applying a few drops to the bb shell and the outer race of the bearings then spread it either with finger tip or acid brush, then allowed it to set up for 1-2 minutes before pressing in the bearings. If the retaining fluid pools in the bb shell while waiting for it to set up, then you have used to much.

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PostPosted: Thu Feb 23, 2017 5:31 am 
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Location: Olympic Nat'l Park, WA
Loctite manual (large .pdf file):
http://www.loctite.com.au/aue/content_d ... proved.pdf

Note pages 24-30.


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PostPosted: Thu Feb 23, 2017 2:46 pm 
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The only "issue" with retaining compounds ( like 638/648 ) and BB86 is that none of them work with delrin. Alu/steel/Ti to CF -> yes, delrin... no.
If BB shell is out of specs ( delrin is not compressed enough and relatively evenly ) then frame is ... useless. Only solution are brackets from companies like Rotor, Kogel or C-Bear ( alu cups ). Maybe some day some business will do "oversized" delrin cups for worn shells... (?). Compound is able to "cover" up to 0.25mm( 638) or 0.15mm (648) max. For well worn shell it can be not enough.

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PostPosted: Thu Feb 23, 2017 3:37 pm 
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Mr.Gib wrote:
Thanks Cal,

As always, a fountain of useful info.

Applying the loctite to the outer races of the bearings instead of the shell seems to be the way to avoid contamination - good tip.

The problem is unrelated to sideload, or faulty installation, or brand of of BB. I can only get play in the crank when I have it at the 12 and 6 o'clock positions. At 3 and 9 it is rock solid. The shell is ovalized on the vertical axis which is what you would expect from wear. And there is absolutely no play laterally so sideload is more than adequate. Using Sram as at happens. I have the same set up on another Trek which has and alloy sleeve in the shell. No play at all on that bike.

I have also heard that trek has slightly oversize bearings for bikes that are, or end up out of spec. I think it would be my preference to go this route if it meant I could still use grease. Using loctite means I can't take things apart and clean quickly and easily.

This is yet another example of why press fit, slip fit, etc. is such an inferior design. This problem could ultimately render this frame unusable (something you demonstrated in an earlier post). No one should be surprised by this. Using grease facilitates movement which leads to wear.


I suggest the oversized trek bearings before you try the loctite. They are specifically designed for this issue.


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PostPosted: Thu Feb 23, 2017 4:02 pm 
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Yes. I'd actually at least even try a brand new set of regular bearings, just to rule out completely the possibility of shot bearings. They're not expensive. I'd also like to know exactly how "ovalized" the shell has become via measurement of the inside diameter at various axis with a good set of vernier calipers if you've got access to some.
@Goodboy: do you work at a Trek shop? In your experience how common is this issue with BB90 and is it more an issue of the past than current? I've only dealt with recent model Treks for the most part and before I built up my Emonda I measured the shell and the specs were very good. I was very impressed with it compared to some other carbon shells I've measured this way. But I have another Trek awaiting build up and it is a little tighter than my Emonda was and while it is the same BB90 shell (slipfit), the bearings will definitely need a little more "help" going in. So I'm curious as to what the experience has been in general.
@Stormur: the use of primer allows these retaining compounds to work with "inactive" substrates such as carbon fiber and titanium. 638 is actually what Trek recommends, along with the primer, to install the Campy adapter kit in the BB90 shell. It's just a little thicker than say, 609, and intended to work with larger gaps which is the case with the Campy seal seat fit in the BB90 shell. 0.25mm is quite a significant gap in these applications and if you've got that much then you've probably got worse things to worry about. I've never had an issue bonding, in other brands, Delrin PF30 cups to carbon shells this way. Works very well.

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Colnago C60 - PR99
C59 Five Years Later
My Special Colnago EPQ
Trek Emonda SL Campagnolo SR


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PostPosted: Thu Feb 23, 2017 4:15 pm 
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Location: Wilmington, DE
stormur wrote:
The only "issue" with retaining compounds ( like 638/648 ) and BB86 is that none of them work with delrin. Alu/steel/Ti to CF -> yes, delrin... no.
If BB shell is out of specs ( delrin is not compressed enough and relatively evenly ) then frame is ... useless. Only solution are brackets from companies like Rotor, Kogel or C-Bear ( alu cups ). Maybe some day some business will do "oversized" delrin cups for worn shells... (?). Compound is able to "cover" up to 0.25mm( 638) or 0.15mm (648) max. For well worn shell it can be not enough.


Bonding Delrin (acetal) is a lot like bonding polyolefins. It needs a specific primer and adhesive but with those it can be bonded quite well. Page 17 of this design guide (https://www.ellsworth.com/globalassets/ ... onding.pdf) recommends Loctite 770 primer and 401 Prism adhesive. I have used this combination to bond polypropylene-based thermoplastic elastomers and the result is a bond that is far stronger than the rubber. Without the primer, virtually nothing will even begin to bond to the TPE. Per the chart provided in that pdf, acetal seems to behave very similarly.

The only caveat with using 770 and 401 is that you will need act quick. The bond happens in a few seconds but it does take some time to reach full strength. Be prepared with a wood block and hammer to tap the bearings the rest of the way in should they freeze up before fully seated.

As far as filling large gaps, Loctite has a product for that, too: http://www.loctite.sg/sea/content_data/ ... mpound.pdf

I've used that stuff to repair a crankshaft end on my Honda after the crank pulley driving the time belt came loose and wore away a good chunk of the hardened steel. Been going strong for ~8 years since that repair.


Last edited by joejack951 on Thu Feb 23, 2017 4:17 pm, edited 1 time in total.

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PostPosted: Thu Feb 23, 2017 4:17 pm 
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Are you the original owner of the frame? Trek offers a slightly oversized bearing for this problem. I think they have a green seal on them. Or send it into trek so they can rebuild the BB area. We have never been instructed by trek to use any kind of locktite at the shop.


Last edited by nickf on Thu Feb 23, 2017 4:19 pm, edited 1 time in total.

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PostPosted: Thu Feb 23, 2017 4:19 pm 
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I think trek changed specs and manufacturing practices several years ago when this came up. But this still comes up for other reasons. If the preload is set wrong on the crank, the slight movement over time will cause this to happen as well. So in summary, originally due to poor mfg tolerances but now mostly seen due to user error in preloading. I don't work at a trek shop, but I've seen my share of these. As an aside, I've always found that the NDS bearings on bb90 frames goes first. DS bearing usually is ok. Perhaps due to more protection from dirt and water.

Sent from my SM-G900W8 using Tapatalk

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PostPosted: Thu Feb 23, 2017 4:35 pm 
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Interesting. Thanks. And yes again about the proper preload being used.

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Colnago C60 - PR99
C59 Five Years Later
My Special Colnago EPQ
Trek Emonda SL Campagnolo SR


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PostPosted: Thu Feb 23, 2017 4:36 pm 
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@Calnago, I went thru ALL compounds with delrin. It is one of the most ( if not most ) "stubborn" material to bond. I have somewhere in archives list of compounds which work for delrin+alu/steel/ti/cf , but it's very short list. Some agents have extremely fast curing time ( like mentioned above ); for slip on it maybe enough, for usuall press fit and ovalized shell ( when still require to press in ) - not so much.

There's other solution, bit radical so rather for permanent assembly ; automotive silicones for assembling "plastic" parts of cars . Naturally with primer , curing time to full strnegth 24h at 20degrees Celsius. But require extremely clean surfaces. Works also for f.e. Rotor alu cups in really worn shells ( I mean really really worn ) or those very out of specs ( like Wilier 386 shell and "Wilier cups" ; those have replacable bearings so... can be done that way ). These silicones are very vibration-load, sheer & peer resistant. Range of temperatures is also beyond any cycling need, same as oil / cleaning agents resistance. But they're not cheap. Other side : this thing is able to bond everything to anything ;) . It's so good that most of those have approval for military and aircraft assembly/ repair.

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PostPosted: Thu Feb 23, 2017 4:47 pm 
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Aren't SRAM PF30 cups made of delrin? And pretty sure the cups from Praxis for one of their OSBB bb solutions are also delrin. I've had no issues with bonding these in what were previously "problem" shells.

Image

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Colnago C60 - PR99
C59 Five Years Later
My Special Colnago EPQ
Trek Emonda SL Campagnolo SR


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PostPosted: Thu Feb 23, 2017 5:57 pm 
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Calnago wrote:
I'd also like to know exactly how "ovalized" the shell has become via measurement of the inside diameter at various axis with a good set of vernier calipers if you've got access to some.

No access to calipers for a precise measurement. Just by rocking the crank I would guess 0.5 mm, maybe more. A huge amount in this situation. I have never noticed it because I keep the BB perfectly clean and greased so the bike is silent. And just the drive side. Non- drive seems solid.

I think this is an issue we will see more of as these bikes age. The local Trek dealer was quite familiar with the problem - seen it in Madones. Normally a Boone would never see the kind of mileage that a road bike would, but I use mine a my winter trainers so to 200 - 300 km per week depending on the weather so a lot more wear than your average cross bike.

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wheelsONfire wrote:
When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.


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Posted: Thu Feb 23, 2017 5:57 pm 


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