On 8/10/2020 11:37 AM, Tom Kunich wrote:
On Sunday, August 9, 2020 at 5:15:01 PM UTC-7, AMuzi wrote:
On 8/9/2020 11:47 AM, Tom Kunich wrote:
On Saturday, August 8, 2020 at 6:08:01 PM UTC-7, jbeattie wrote:
On Saturday, August 8, 2020 at 3:15:40 PM UTC-7, Tom Kunich wrote:
When I got my Trek Madone if became rapidly clear why it was so cheap. The bearings in the BB90 were rather loose. Now there are several methods of fixing this - one is to use a strong locktite-type compound which locked the bearings in place and one is the Trek way which is to put an oversize bearing in place of the stock bearing.

With normal caution as an Engineer I chose the least damaging method first. I followed the directions on the locktite and glued the "just fits" bearing into place and allowed it to dry the requisite 48 hours.. Well, climbing one of the local hills last Tuesday the BB90 began to "click" in the same place every revolution on the drive side pedal. This means the glued drive side bearing has come loose. Inasmuch as I am presently working on the Colnago I won't look at this until later. Another choice has come up - that is to check the bearing that is presently in the Madone, to see if it is undersize. That might be the case since the bearings more easily obtained from Trek are Chinese and let's say they aren't the finest quality bearing available. Hambini of one piece BB push in bearing fame who hates BB90 also can supply NTN bearings which are exactly the right size. NTN is a Japanese bearing manufacturer that supplies the best bearings in the world.

So when I remove the bearing that is presently flopping around in there I can closely measure it if I can remember where I put my micrometers. Failing that I do have a digital caliper that is fairly accurate to two decimal places. If the bearing that is in there is undersized by any significant amount (which is common with Chinese bearings.) I will get the bearing set from Hambini and install those before going to the extreme of those oversize Trek bearings which are so oversize that they can distort the bearing cups. This screws up the bearing and generally causes premature failure though "premature" is sort of an undefined term that might mean it only lasts for 1,000 hours. Chinese bearings would probably only last for twice that anyway. NTN bearings virtually last forever under the sorts of loadings that the BB90 puts on them.

So presently I'm riding the Emonda and trying to go no lower than the 28 tooth so that I can get a little more training in my legs. I am presently at 80,000 feet of climbing when I would normally be at double that. I normally close a year off with over 200,000 feet of climbing. Judging from the way that my legs felt today after a couple of 900 foot climbs I don't think that I will make 125,000 but stranger things have happened.
You should also check the crank bolt torque and maybe swap the pedals out, check the chain ring bolts and even the rear QR before pressing in new bearings. Cyclical clicks can come from places other than the BB.

-- Jay Beattie.
Being on the drive side it cannot be crank torque, the pedals are new so the bearings are extremely unlikely to be loose and usually make noise at the ends of the crank revolutions both top and bottom. Cyclical clicks in exactly the same location almost always means that you have a loose bottom bracket bearing. But of course before I disassemble anything I check everything out. That is what a bike repair stand is for.

Before doing anything else, find an able willing assistant
(who is not our age with hearing impairment).

Get on your bike with your shoes and hold the front brake
firmly tight. Lean on something (doorway, chair back) with
you other hand. Press as hard as you are able on the right
crank (around 3:00 position). Backpedal and repeat for the
left crank. Hard. Continue in that cycle as assistant
listens near the BB area, at the rear wheel and so on. I
find a finger on a chainring bolt or RH cup/bearing or pedal
spindle to sometimes be edifying (you can talk with
assistant as you do this so there are no mangled fingers). A
mechanic's stethoscope is also useful.

We replace some crank bearings at rider request which
sometimes are a misdiagnosis of a
pedal/skewer/spoke/chainring bolt/saddle noise.
--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971
I hadn't thought of a lose crank bolt which could offer the same sort of noise in the same sort of position.

Years ago, in the middle of nowhere (well, western Ohio) on a solo tour,
I had one of those loose crank bolt events. It was a great feeling to go
from impending doom to silence and joy using only an allen wrench.


--
- Frank Krygowski