Jackmen

I am in the process of replacing the Bottom bracket on my 2014 Giant Defy advanced 0. All carbon frame but has a aluminum insert that the bottom bracket fits into. Determined that it is a Press fit Shimano BB86 or that it uses a BB71-41B bottom bracket which I have on order. It uses the plastic receiver that pushes into the BB shell that contains the bearings.

Popping it out was a breeze with the Park removal tool, and installation looks very simple also.

The question I have is that the aluminum insert has some very minor corrosion on the outside edge. My thought was to take some very fine emory cloth and brush up the inside of the insert to make it smooth as possible. Then I have heard that if you do have an aluminum insert that you should install grease prior to pushing in the new bearing cups. does this sound correct?

The reason for the BB replacement is a squeak that happens only when the temperatures get quite warm, and the squeak gets worse the warmer the temperature gets outside. The bearings appear smooth in the old BB but my guess is that as it got warmer the BB shell (flat black Color) got warmer and expanded and allowed a little more space between the aluminum insert and the press fit BB cup which caused the squeak. Hopefully putting a new BB and greasing it well will eliminate the squeak.

Andrew R Stewart 

Some sort of isolating compound is a very good idea. If the fit between bearing and shell is tight enough grease serves well. If not then anti seize or even Locktite retaining compound are suggested. This fit is hard to determine for the novice so the usual path is to try grease, being the easiest to apply, likely to be on hand and least effort to reverse. Then move onto more involved compounds if the grease doesn't work for long enough. Note I said "for long enough". No solution is forever. Andy (who never put much credence in the "heating up" of a drivetrain as reason to cause issues).

Jackmen

Andy you have some very interesting view points, that appear to come from experience with press fit BB's. So apparently you have ran into this situation before and solutions are temporary in nature, such as greasing, then having to grease again after a time (maybe a season of riding) to keep the press fit from squeaking. I was thinking of locktite also but was wondering about its effectiveness between the Bearing cups and the aluminum insert.

I am guessing about the temperature causing expansion as the reason for the squeak but how do you explain that it get loudest on hot days and goes away when it gets cooler out ?

Tunnelrat81

I have a BB86 Trek being used with a Shimano crankset, and although I have yet to have any trouble with the OEM BB (the bike has less than 1k miles), I've had my eye on the threaded option such as the Wheels Manufacturing bottom brackets. I've had good luck with their threaded PF30 BB's for shimano cranks, and I assume the threaded BB86 option would be equally as successful. They are more expensive, but if it decreases noise and and increases bearing life, it might be worth considering.

Wheels Manufacturing BB86/92 Bottom Brackets

-Jeremy

Andrew R Stewart 

I don't have an explanation except my observations of many (as in many dozens over the years) customers suggestion the same "heating up" effect. Sometimes I ask if they actually compared the temps of the parts before and during their ride, but that's only when I got frustrated because I know they didn't.


The metal that the shell and the bearings are made of has such a minute amount of expansion over the relatively few degrees of difference between a home and the outside (20-40*) (Compared to the metal's 1000*+ of temp range before significant changes occur). The grease is more effected but it's inside the bearing, not between the bearing and shell (and having grease there usually quiets down and creaks anyway). So that's not what's going on.


So I offer this- the most variable component, the part that does experience a "warm up", the piece that does have a larger variability in it's function, it's forces, and is the only component that has perception is the motor. The rider. It is reasonable to look at the part that has this variability and a perception (which also if variable in it's function) as a major factor. Andy.

dsbrantjr

I would think long and hard about using Loctite or other adhesives on a press-fit BB, due to concerns about serviceability. You will need to plan how to get the assembly apart unless you expect the BB to last forever.
From the Loctite brochure:

"Bearings assembled with LOCTITE®Retaining Compound can be disassembled with industrystandard bearing disassembly tools and techniques,including bearing pullers and hydraulic presses. Anothertechnique is to heat the parts well above the servicetemperature [to 250°C (482°F) for most products] anddisassemble while the parts are hot." https://na.henkel-adhesives.com/us/co...Brochure_F.pdf


Sound like good ways to damage or destroy a frame, especially carbon.

Bikedud

The shop where I work has sold dozens of Giant Defy Advanced and TCR's with the Shimano Pressfit BB. Also, I personally own only one high performance carbon bike and it's a TCR. I experienced a creaking BB a couple of months after I purchased my TCR and other customers were began reporting the same experience so I conferred with the tech guys at Shimano and Giant. Now, as a matter of routine maintenance, I remove, clean, grease, and reinstall the BB and crankset on my own TCR at least annually (headset bearings too). Over the years I have done the same for dozens of customers. I haven't noticed any correlation between increased temperature and BB noises, but there may well be one. My experience has been that once the creaking/squeaking begin, it doesn't go away until maintenance/replacement is completed.
FWIW- If you have the triangular aero seat post, you may want to make sure you keep the post clean and install some carbon assembly compound.

well biked

While there are definitely situations where pressfit-to-threaded bb adapters are not a bad idea, if you are running a Shimano crankset in a frame that uses the BB86 standard, there's no good reason to not use a Shimano BB86 bottom bracket, in my experience. These Shimano pressfit bb's are very durable, sealed well, and are made for Hollowtech II cranks, no adapters called for or needed. I've personally had excellent results with their performance and durability.

Bikedud

Ditto

Andrew R Stewart 

My suggestion is with respect to the OP's situation. He said his shell has an alloy sleeve. I do agree that bare carbon is not where common retaining compounds are to be applied. Andy

Kimmo 

Threadless BBs like BB30, PF30, BB86, etc are inherently problematic. Creaking noises are way too common.

Fortunately, there's a sensible solution:

Jackmen

Bikedud

Thanks for sharing your experience. Does your TCR have an alloy insert in the BB shell? Just wondering with mine having the alloy shell in the carbon shell, is it wise to use grease or Loctite between the bearing holders and the alloy shell? And when you take apart the bottom bracket do you remove your BB86 bearing holder grease and reinstall the same one. I have seen that you are to not reinstall the old one but install a new one every time.

Bikedud

My TCR (2012 model) has the aluminum insert in the BB and I always use grease when installing a new BB or re-installing the old BB. Generally, I remove the entire press fit assembly, clean BB shell and press fit assembly, inspect the bearings and re-install or replace the BB depending upon the condition of the bearings. It's usually very easy to tell if the bearings are crapped out, but unless you ride in the rain a lot, they last quite a while. Of course, a Shimano BB72 is generally less than $25 so if your concerned at all about the condition of the bearings, just replace everything. Like anything else, it helps to have the proper BB removal and installation tools.

WizardOfBoz

Andrew, I think you know all about the following. It was motivated by your "heating up" comment.

Normally when you fit a bearing, you press fit it onto a steel shaft or into a metal housing. One or the other (both?) can be mounted this way. The tight fight is called an interference fit. So the ID of the bearing is a little smaller than the od of the shaft. Fitting the bearing on the shaft actually stretches the internal race. This might reduce radial clearance by a bit. One example I looked up cited a change of 13 microns. Same thing if an interference fit is used for the outer bearing surface, but normally you use an interference fit for either the shaft or the outer bearing housing, and not both. Anyway, for this reason, bearings often have an unmounted clearance in the same range, depending upon bearing class.Typical figures might be 6-23 microns.

The press fit into the CF frame probably doesn't apply the same compressive force as does fitting a bearing into (for example) 4340 steel. And the hollow BB spindles are what is called a "sliding fit". Neither will stretch the bearings much. I suspect that bicycle BB bearings have a smaller initial radial clearance. Maybe even a preload, which would be negative clearance (that is, a pretty tight fit).

The thermal expansivity coefficient for stainless and bearing steels is 10-11 x 10E-6/K. So assuming you went from 20°C to 60°C (140°F), you'd see a 4 parts in 10000 increase in the bearings and the races. For a 37mm OD BB90 bearing, that's about 0.0148 mm in the outer race. This is 15 microns. That would be an increase in the ball size, and the inner race size, too. About 10 microns for the race. The change in ball size is negligible. So the thermal change in clearance, for a reasonable temperature change, would be about 5 microns.

Going from 5 microns preload, to zero micron clearance after a warmup, is probably not going to be noticeable, especially since you are applying force at 175mm or so. But perhaps experience proves me wrong (properly obtained and analyzed data beat the best theory). Does the above jibe with experience?

Andrew R Stewart 

WoB- Yes I see the clearance/preload of cartridge bearings close up on installation (or better to say when a "bad" bearing is felt "in situ" then removed, the "badness" feel reduces as the preload loosens up). As to the growth of the actual rolling elements with heat- I suspect that the tolerances of a bike exceed any tiny heat induced changes. So I tend to look for the greater effect. Is the bearing seat (axle or shell machining) within x number of microns? Was the bearing pressed in with the same accuracy? Are the bearing's inner and outer races in the same plane, or is there a slight offset (preload) between them that's not designed into the bearing by the bearing manufacturer? (As in the shell sleeve and the spindle don't have the correct bearing seat spreads). How much does the bending of the axle or distortion of the frame due to pedaling forces compare to heat induces growth? I don't know these answers but I have strong suspicions that the real life and setting of bike bearings are far more a factor then minor heat induced dimensional changes are.


This post started with the issue of noises/creaks/clicks/squeaks (and what each term is in real life has overlap that's different for each rider's perception). My experience with heavily preloaded bearings is not a short/quick/momentary type of sound if the bearings are otherwise in good shape and well lubed. I highly doubt that the rolling elements/races condition is causing the OP's noises. A good condition bearing poorly installed, loose fitted, dry seats can very well cause the noise the OP mentions.


Example is a hub I worked on just Friday, a cartridge bearinged design with an Al shell and axle. The complaint was a noise similar to what I suspect the OP was trying to describe (and again the same noise will be described differently by different people). With the freehub body removed and the axle in place one can feel the bearings slight roughness (they are tiny 6802s, these have very small diameter balls. The load capacity of the bearing is geometric with the ball diameter but linear with the ball count. No wonder the bearings are getting rough in a "short" time. They don't have the capacity of larger balled cartridges). I pulled the axle. Found that the axle has a snug but slip fit between the inner race and the axle bearing seat and that the non drive side seat was dry of any compound. I could see slight polishing of the axle seat that was uneven, suggesting the axle if moving within the inner race a tiny bit. This is what I attribute to be the cause of the noise. With the axle removed the bearing still in the shell felt rough. Removed both bearings and now the bearings feel not so bad, the preload of the shell press fit has been relieved. Reassembled with new bearings and HD marine grease between all seats/races. All feels smooth and no noise on test ride. If the sound returns and the bearings still feel good then I'll advance to a bit of 609 retaining compound on the axle seats. Andy.

Jackmen

OP here. I reinstalled my bottom bracket press in cup on the giant defy with a nice layer of grease both on the alloy BB insert and on the plastic bearing cup that fits into the alloy insert. If I would have known this was so easy I would have done this years ago.
There definetly was a increase in sound as the temperature increased.

Personally I dont think it had anything to do with the bearings themselves changing temperature, as I'm not sure that's where the noise came from. My thought is that the change in temperature of the BB and the alloy insert allowed for differential change in in size of the alloy insert and the plastic bearing holder that fits into the the insert allowed a slight movement and because the bearing cups had never been removed and regreased it caused the creek.

The bike frame is flat black and it seemed like the creek was the worst when the sun was shining and it was hot out. Nothing to do with the bearing heating up because of movement. When flat black carbon fiber is left in the hot missouri sun, Im sure it reached 120-130 degrees, which would transfer to the alloy insert as its a great conductor. Insert heat up expands (at a greater rate than the plastic bearing cup, which had no grease in it from 2+ years of use and 12,000 miles, so it creaks. When it would come fall temperatures would cool, the creek would go away.

This is all somewhat of a conjecture, but I guess we will find out when summer hits now that the cups and insert have a nice layer of grease. Thanks for everyones help on this issue. Many have shared a great amount of info that has helped me out imensly.