Telly

Hello everyone,

Even though this IS a technical question, I've posted it here in the Clydes/Athenas section since our parts might be prone to a bit more wear and tear...

How long does your bottom brackets last for?

I commute to work daily with my bike and since the last time I changed my bottom bracket (factory defect) I've logged in around 1000km (about 650 miles). Please keep in mind that the bottom bracket I have is a Shimano UN26 (68x113) with the plastic cup on one side, and during the last few days I've felt the B/B loosen a bit. So far I've checked the pedals and cranks for play: negative, and have had a fellow cyclist which knows his stuff check out the bottom bracket which he said had a tiny bit of play.

I will take the bike to my LBS on Monday and see if it needs some tightening, but from past experience it feels like it's failing, and since I don't mash on the cranks or ride hard, I believe that it should have lasted a bit longer.

Also, can someone recommend a better quality alternative to the UN26 which would be compatible?

Thanks!

10 Wheels

18,000 miles on mine before it went bad.

CommuteCommando

The most miles I ever put on a bike was just under 10k, and I never had one fail.

RollCNY

My stock UN26 failed after 1600 miles, but it didn't fail by loosening up. I probably wouldn't have known mine was shot if I hadn't needed to change the BB length, and when I had the cranks off I noticed how poorly it turned, and that it had very sticky spots. I replaced it with an IRD BB and have been very happy, but have not passed 1000 miles with it yet. Most of my miles have been on an external bearing crank, with no bearing issues after 4k miles

Telly

I know that the UN26 is the bottom-end/economy model, and would like to upgrade to something better, and so far was looking into the UN54/UN55 version of Shimano's range. RollCNY, can you tell me where you got the IRD unit and how much it costs?

Mr. Beanz

I had a stock BB that lasted about 10,000 miles on my Lemond. It was replaced by the shop but loosened after 500 miles or so. It was tightened by the same mop head but once again came loose after another 500 miles.

It worked loose once again afer another 500 miles. Took it to a mechanic I trusted. He said there was nothing wrong with it, that the mop head mechanic did not readjust the BB properly when I took it in for service (cranked down super hard on one side and did not touch the other). I did however replace the entire crank and BB with an Ultegra outboard set up and never looked back.

The mop head did tell lme at installation that it might work loosen after a few miles and to bring it back for readjustment. I just thought he woud have done a good job at the adjustment but didn't.

So yeah, they can work loose after installation and can need adjustment.

The BB in my Lemond was TruVativ, $1000 bike, I neve did like it. Never was smooth so I was happy to replace it.

RollCNY

https://www.amazon.com/IRD-QB-55-JIS-...0789567&sr=8-1

Telly

Hello again Mr. Beanz,

Since I don't have the proper tools to check out the B/B, I've arranged to take the bike to my LBS on Monday and have it checked, although the UN26 doesn't have any other adjustments; just slip it in and torque to 50-70Nm (of which I HIGHLY DOUBT my previous LBS did since I never witnessed the use of a torque wrench in his shop).


Thank you for the link RollCNY!

RollCNY

Also, I would suggest that you learn to tighten them yourself. Crank puller and BB socket are inexpensive, and have been the most used tools that I have, especially since I help out the neighbor kids at times. Per Mr. Beanz's comments, I find tightening a BB properly to be a multi-step process, incrementally tightening each side until both are set.

SUPER SECRET TRICK: When using the BB tool, thread a bolt into the pedal spindle to hold the socket in place. Take your new BB to the hardware store, find the right M6 thread (can't remember the right pitch), and then store it with the tool. Major life saver in loosening a tight BB.

Mr. Beanz

I was in the same sit not having the tool. The work is easy but with several types of BB's on 10 (max bikes) I wasn't about to buy a tool for every one knowing it was not cost effective. So I know where you are coming from. I did buy the tool for my latest bike since I wanted it done right.

As per RollCNY's advice, most times when I go to the shop I am lucky enough to witness the work. I will tell the mechanic "can you please be sure to tighten blah blah blah evenly, please. I know it will be more effective blah blah blah". Let them politely know you know what's up.

When I had mine done, I had never done it myself or had the valuable advice of forum members on the issue. Now you know so let em know you're informed on the matter.

Mr Sinister

Or you can take the bolt from the crank itself down to the hardware store, and reverse engineer it. I did this by putting the bolt in a nut display, finding the right nut, and they had a bolt with the right thread size just below it. Either way its good.

Like Roll said, this trick makes it so much easier.

mkadam68

Shoot... my BB probably has 40,000 miles on it. About 4-6 times a year, I take it out & apart, clean it up, re-grease the threads, and I'm good.

I use the Shimano BB-6600:

skilsaw

From my experience, the right side cup has a specific position where, after installing the crank, the chain rings are in the correct position relative to the frame (chain stay not interfering with the chainrings). In this position, the chain rings also line up properly with the front derailleur. It isn't torque on the right side that matters. It is getting the cup in the right position. But I may have it all wrong.

RollCNY

My comment was specific to cartridge style square taper BB's, like the UN26 referenced in the OP. I install drive side until it tightens securely, then non-drive, and I find that the drive side is usually slightly loose after doing the non-drive. So I repeat the process. I may be doing it wrong, but have had the best results that way. Additionally, I could buy a 2nd tool to tighten both sides concurrently, but that has been unnecessary so fat.

As to lining up chainstay clearance and position with FD, that is a function of having the correct length BB to start with for correct chain line. Typically 103 for single, 107 or 110 for double crank, and up to 123 for triples.

bradtx

If you're going to buy a new one there are two BBs that are well regarded; Shimano UN-54 and UN-55. The only difference is that the UN-55 has an alloy NDS cup.

Brad

nymtber

I have an older Shimano UN-72 BB from 2001. It has maybe 3000 miles on it, most all off road/crushed gravel bike path. I take it out every other year, clean all the grit and grime off the bearing area and re-install. Still as tight and smooth as the day I bought it

Bill Kapaun

I swap in quite a few UN-26's for my CL bikes I flip.
I can't imagine the cups loosening if one comes halfway close to the proper torque.

As often as not, in order to fully seat the plastic cup without breaking, I back off the fixed cup, seat the plastic cup and then "drive" the fixed cup home.
Removal is the opposite to avoid breaking the plastic. Loosen the fixed cup first.

Telly

I have to thank everyone here for all the input and great ideas!

One thing that still bothers me is IF the B/B is toast, can it be something with the frame causing it to fail so soon? That's my hidden fear... frame failure; everything else can be swapped/repaired but I wouldn't want to think that I manged to destroy the B/B mounts!


EDIT: Just found a great deal on the Shimano UN55 B/B (both cups are metal) from a German online firm for €11 and have gone ahead and placed the order; I'll replace the UN26 with the UN55 which is supposed to have better quality ball-bearings and if the UN26 only needed tightening, I'll keep it as a spare unit.

bradtx

Telly, The UN-54/55 has better seals also. As you have one on the way, install it rather than retightening the UN-26.

While it's possible, it's very unlikely that the BB shell is causing a problem. The NDS plastic cup (which was introduced to reduce creaking noises) is also not likely the problem. You can also ask the bike shop to "face and chase" the BB shell prior to installation. This will square the BB shell edges to the threading and insure full contact on the drive side.

Brad

Rona

I have a very, very old sugino that has been around since dirt. I don't know how many miles it had on it before me. It gets pulled apart and regreased every 5 or 6 months. It's pretty sweet and has a lovely finish.

Telly

Hey Brad, I'll take your sound advance and wait till the UN55 unit arrives this week to swap it out with the current UN26. Don't think the bike needs any facing since it's only 5 months old and hasn't had a hard life at all.

Quick question: except for cleaning the shell races and re-tightening, does the UN55 or any cartridge type B/B need other type of maintenance? I ask because of Rona's comment on her Sugino being pulled apart and re-greased every 5-6 months. BTW Rona, US ex-pat here too!

bradtx

Telly, Actually refacing the BB shell is usually done on some bikes prior to the first build. Often it is paint over spray that needs to be removed to make a flush fit of the BB.

The cartridge BB could be serviced, but generally parts are too difficult to find and they're tossed or recycled.

Brad

paisan

When you say the BB is loose, are you referring to the cups or the axle itself? If it's the cups, just tighten them. Unless you have an Italian threaded BB, which could explain the loosening cups. If it is an Italian threaded BB and it doesn't already have some form of thread prep(which UN-26's don't) then it requires locktite on the non drive side to help keep it from working itself loose.

If it's an english thread BB and the cups are continually coming loose then it's either been installed improperly or your cups need to be faced badly. When you go to swap your BB don't forget that english thread bottom brackets are threaded opposite of pedals. So drive side is left hand, non drive is right hand. Italian thread are Right hand on both sides.

RollCNY

This seems wrong to me. BB shell gets faced, not cups, and only on outboard bearing style designs. Squareness of face to threads is less relevant to square taper internal cartridge bearing BB's. Bearings are already perpendicular to spindle regardless of BB shell condition.

OP - in my opinion, if they offer to face the BB for free, let them do it. If they want to charge you for it, it is probably not worth it.

paisan

LOL yes sorry for the confusion.

True, I'm thinking cup and cone, and again italian threaded BB where any extra binding will help the nds walk itself out.