Trek 520 Lesson Learned
 

I posted this on the Touring forum but felt it should also be here:

I have been averaging close to 100 miles a week commuting on my 520 in No. Virginia since April 1, 2012. This includes all through the winter slush and road salt and sand treatment. As of this past Friday I have 3994 miles on the 520 and I discovered that my left side bottom bracket bearing is completely gone. Just three months ago, at the end of March, I had the shop do the year end adjustment. I had a 15 minute lesson from the mechanic on how to disassemble the BB. I had never worked on a sealed bearing BB before and knew, after the year free adjustments, I would be doing everything myself. We, the mechanic and I didn’t notice any play in the bearing at that time. He even said there wasn’t much to do with the sealed bearing. He didn’t’ say I should take the BB apart to check for wear. I was focused on the BB at that time because I knew an extended road tour was in my future.

It know with the damage, it must have been longer than two weeks ago but I thought I felt a wobble or play in my left side pedal. I thought my cleat on my riding sandals was loose. It got a lot worse last week and when I checked found the spindle had at least 1/16 of play in the left side bearing. When I got BB apart (I had to hammer the spindle out with a rubber mallet). I found a lot of road grit and sand in the bottom of the frame which I assume came in through the weep hole. The problem had gone unnoticed long enough to score the spindle. It took a solvent soaked brass brush to get the dried grease off the spindle.

I consider myself a fairly experienced bike mechanic. For years (since 1980), riding non-sealed bearing bikes, I religiously did a winter tear down of the bike, cleaning and repacking the BB, wheel hubs and steering tube. After hearing “you don’t have to do much” with sealed BB, I did just that, never looking or checking. Going from 4-600 miles of weekend riding a year ( recently on a 2006 Trek 1000) to 3,500 plus miles of commuting is a big jump. The Trek 520 was cleaned and the chain lubed after every major rain event. Yes in the winter that might go a couple of weeks but I at least hosed off the road grit when I could.

Hard lesson learned. I $40 BB isn’t too bad and from now on it will be checked every 1000 -1500 miles. I have my fingers cross that there won’t be any play in the damaged spindle, knowing replacement will go closer to $100.

I get flak from many here when I say this, but most of the bearings used on bikes are stock sealed bearings intended for the electric motor trade, and have dust seals rather than true weather seals. IMO these do a better job keeping water in than out, so I avoid them whenever possible (gets harder every year).

You're right that all season riders must tear down, clean and inspect, and grease (or replace) all the bicycle's bearings including the so-called types.

One reminder to those who service sealed (cartridge) bearing hubs and BBs. Most of these are of the radial, vs. angular contact type, and as such are not to be preloaded the same way. On a radial bearing the radial clearance and preload is engineered into the bearing, and you are only to take up the last of the axial play. Putting an axial preload on a radial bearing has the balls running against the sides of the races and will cause very rapid bearing wear.

I think you are laying blame where is isn't due. First there is no "weep" hole in Trek 520 frames that I know of. With the exception of the hole for the cable guide, their bottom bracket shells are solid tubes. The cable guide is either attached with a screw or it presses into place and is effectively sealed against infiltration of water. Infiltration of grit and sand would be nearly impossible unless the cable guide were dislodged. Shifting would have suffered immediately if the cable guide were out of place, however.

The problem here appears to be more related to operator error than to equipment failure. I have no doubt that your bearings wore out sometime in the past. It happens although I haven't worn out any cartridge bottom bracket of any kind whether it was internal or external since I went to cartridge bearing bottom brackets in the mid90s. I've seen a few while a volunteer at my local coop but even there they are rare. That said, when your bike started acting strange, you should have checked to see what the problem was. It sent you a message but you failed to heed it. These kind of bottom brackets really are 'set and (almost) forget' mechanisms. But you do have to attend them when they don't act normally.

I suspect that the bearing cup came loose in your case which would account for play in the spindle. The actual spindle is press fit into the inner race of the cartridge bearing and that turns the bearings. I doubt that you have done much to the spindle. The spindle shouldn't actually turn on the bearing. Just keep the cups tight and I doubt you'll have any problems.

This looks more like a drain hole instead of a weep hole. It's almost .25 across. Interesting the right side doesn't have one and the right side bearing wasn't effected.
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I only wish I got a photo of the inside before I wiped it out.
So I am not surprised after riding through all the Virginia salt and sand all winter the bearing is shot.

Like I said.. lesson learned.

What year is this 520? Trek 520s during my sojourn at Trek (1980-1986) didn't have holes like that.

Agreed tht the "weep hole" is odd. My last 4 years in a Trek shop has not seen this as a stock spec.

Also agreed with Francis that most cartridge bearings are only so-so at keeping stuff out and very good at keeping it in. Given the BB is in the direct path of spray from both wheels and in at the bottom of the bike what would be surprising about short life in poor conditions.

But the upside is that replacements are not too expensive. Andy.

I can't believe that was stock. It just doesn't make any sense that a BB would be shopped that way. It's not even in the right place if the design called for a liner, but then again, there's lots of stuff in the bike world that doesn't make sense, so why should Trek be an exception.

A well designed weep hole is usually smaller and baffled or shielded so it isn't a primary source of dirt entry. Some of the necest I've seen are hidden under the plastic cable guide which, in turn, is relieved in the back to make a channel.

BTW- IME left side BB and hub bearings seem to fare worse because they're more exposed to spray. Even going back to the days of open cup/cone BBs my left side was always more contaminated than the right. I suspect that the right crank arm spider acts as a sort of shield, while the left arm is perfectly shaped to bounce spray directly toward the spindle clearance.

that 520 was made in the last few years i believe. 2 or 3 yrs old max.

does the weep hole have paint on it? that may tell you if the shop did it or not. factory weep holes are not that big IME. i only see 2 or 3 new 520s roll out the shop a year so not a lot of experience

It is a 2012 model year bought new and delivered March 31. Yes the hole has frame paint in it. I will try and reach out to Trek to see if they can give me a reason.

I reviewed my cycling log and saw that I replaced the chain at 2600 miles at the end of January. I remember at the time thinking that the crank rotation seemed "sticky", not very fluid in its rotation. It didn’t have a gritty feel but not smooth. I am guessing the bearing deterioration had already started.

cycommute said;
"I suspect that the bearing cup came loose in your case which would account for play in the spindle. The actual spindle is press fit into the inner race of the cartridge bearing and that turns the bearings. I doubt that you have done much to the spindle. The spindle shouldn't actually turn on the bearing. Just keep the cups tight and I doubt you'll have any problems."

This was not the case. This 520 uses an external MTB BB. Both side were tight in the frame and the left crank arm that sets the lateral play was also tight, set my my shop mechanic back at the end of March. I'll add a photo of the spindle when I can. It is scored quite deeply.

Assuming your bike has the same M 543 crank as the 2013 model, I wonder how the spindle got scored. It should always rotate in unison with the inner bearing race and could only get damaged if the bearing seized solid and the spindle slipped against the race.

That "weep-hole" looks like it is completely covered by the bb cup's threads so it shouldn't be a leak source. Also, there is an O-ringed tubular shield that should be part of the bottom bracket (part #9 in the Shimano tech document, see below). Was it installed?

http://techdocs.shimano.com/media/te...9830625624.pdf

That's what I was trying to say above. Also if the bearing cups were tight to the frame, there's not much way that the crank could have any kind of play in them because of the way that the spindle mates to the inner race.

I don't know what Trek was thinking but weep holes were dumb back in the 1980s and their are just as dumb now. Perhaps that is a mount for a different cable guide. Either way, I'd RTV it to seal it. It serves no purpose but to allow infiltration of things you don't want in the frame.

I'll get the calipers out again tonight and measure how far in the hole is centered and how deep the threads extend on the new cups, but I am sure the hole wasn't covered. Not with as much sand and grit in the frame. The spindle got scored because the bearing "came apart enough" allowing vertical play when I pedaled. Yes the 2012 has the M543 crank. And yes, the plastic shield that extends across the cups was in place.

I hate it when they recycle model numbers. It's not as if we're going to run out of numbers, after all.