
Tech Talk
By Jim Langley
This week’s Tech Talk is about modern bottom brackets, which employ sealed cartridge bearings.
They’re a bit of a mystery to many roadies since there are no obvious adjustments to make. This week I’ll try to unravel the mystery so you know what you’re dealing with and how to care for them.
Jay wrote: “I had a 9-year-old Race Face square-taper sealed cartridge bottom bracket with at least 18,000 miles on it. I finally noticed that the cranks felt different when pedaling and that there was side-to-side play. I had also been experiencing front derailleur rub for at least two years but thought it was my “flexy” steel frame. I had my LBS confirm that the BB had lived a good life, and had them install a Velo-Orange Grand Cru model. Pedaling felt normal again, and there was a distinct absence of front derailleur rub. My question is, How can you tell a bottom bracket requires replacement before allowing it to get so worn that you can feel it while pedaling and suffer issues like rubbing and play?”
Bottom brackets 101
Before I answer Jay’s question, I should explain how bottom brackets became the somewhat mysterious black boxes they are today.
If you’ve been riding for awhile you may remember that the standard road BB used to be a 3-piece design composed of a bottom-bracket spindle that the crankarms attached to (also called an axle), held in place by 2 cups that threaded into the frame. In between the spindle and cups were 2 sets of ball bearings allowing the spindle and crankset to spin smoothly inside the cups.
With the right bottom bracket tools, you could adjust these 3-piece BBs, take them all apart to clean and inspect the parts and bearings, and replace individual parts if needed when things wore out. You usually had to do this once a year – if you were lucky.
A lot of mechanics and roadies liked the easy maintenance aspect; however, it also meant that when you were riding, the BBs could loosen and cause problems. Also, it meant that proper installation and adjustment required skill and could be done incorrectly, leading to breakdowns on the road or worse, halfway into that century you trained for for so long.
Tip: Whether you have bikes with 3-piece BBs or modern sealed cartridge types (keep reading), I recommend buying the basic tools needed to work on them and learning how to use them. It’s not a complicated job, and the tools aren’t expensive. The easiest way to pick up the right tools is to ride by a bike shop on the bike with the bottom bracket you want to work on, and ask the mechanic to show you which tools you need to buy. Once you have them, you’ll be able to install a new BB by following the instructions that come with them.
Sealed Cartridge BBs
To fix the limitations of 3-piece BBs, the bicycle industry responded by replacing them with sealed cartridge bottom brackets, which come in many styles but are designed to all but eliminate maintenance andbreakdowns. That is because they employ sealed and basically adjustment- and maintenance-free bearings.
It’s not exactly accurate, but you can think of these sealed bearings as the old-style cup and bearing made together, which is why they are called “cartridge” bearings and BBs.
The idea is that the bearings are permanently lubricated and adjusted for life when they’re made at the factory. And the cartridges are pressed into the bottom bracket or the BB cups, or into the frame itself, depending on what style of sealed BB you have on your bike.
Replace don’t fix
But the biggest difference with the sealed cartridge BBs is that they are designed to be replaced when they wear out rather than being fixed. In comparison, the 3-piece BBs were designed to be disassembled, inspected and repaired by replacing individual worn-out pieces.
When sealed cartridge BBs came out, a lot of us worried that we’d be replacing them all the time and they would prove much more costly than the tried-and-true 3-piecers. But time has shown that a quality cartridge unit will last for at least several years with zero maintenance (consider the 18,000 miles it took to wear out Jay’s). Plus, they’re easy to install, run smoothly without any fussy adjustment, usually require no maintenance and, best of all, aren’t overly expensive.
Tip: We tend to think of sealed cartridge BBs as something new; however, it’s a time-tested and proven design going back at least 70 years in cycling and much further in machine tools and motors, etc.
Back to Jay’s question
I replied, “Thanks for the question, Jay. I’ve seen the same thing happen to lots of cyclists. Our legs are so strong, and pedaling is so easy and fun, it’s often only major problems that really get our attention. An extreme example I remember is when I fixed a top woman racer’s bike on the eve of a huge race. She said it was running great.
I routinely checked it over and found a problem straight away. Her bottom bracket bearings were rusted so badly that you couldn’t even turn her crank by hand, but only by forcefully pedaling.
She had no idea at all because it had gradually worsened and she was so strong she didn’t notice. Many cyclists would have felt this, but the fact that she didn’t is a good lesson to check your equipment by hand, don’t judge by how it feels riding it alone.
And, paying more attention like this is the only way to avoid BB issues. A good way to do it is by setting a schedule for checking the bottom bracket. For most riders, once every month or so would be a good interval, if you’re riding every few days.
How to check your bottom bracket
To do it, you just lift the chain off the chainrings so that the crank can turn freely. Then you turn it by hand nice and slowly and see if it turns smoothly with a slight hydraulic resistance from nice grease inside the bearings.
Next, you grab one crankarm with one hand, reach through with the other hand and grab the other arm and push and pull sideways. You are feeling for looseness or play in the cartridge sealed bearing BB. There shouldn’t be any.
If there is, you want to figure out why. Usually, it’s as simple as something coming loose, like a cup or bearing, and tightening the bottom bracket will fix it. Sometimes it means the grease is completely used up and the bearings are wearing. In that case you usually replace the bottom bracket, which on modern units is not that expensive and pretty easy to do with basic tools. Or a shop can do it for you for not much money, too.
Tip: I like to keep the correct replacement BB on hand in my toolbox just in case I need it in the days before a race and don’t have time to get down to the shop. This practice has also saved the day for teammates when they realized theirs was shot at the last minute and I was ableto set them up with my new BB.
Other checks to make
While you’re checking your BB, Jay, there are other things to check since they can cause problems, too, and they’re easy to inspect with basic tools. Make sure that all the bolts, both the ones holding the crankarms on and the ones holding the chainrings on, are tight. If you have a triple crankset, there are chainring bolts on the inside to check, too.
While you’re checking that things are tight, it’s good to make sure the pedals are tight, too, since they sometimes loosen or weren’t on tight enough to begin with, and loose pedals can cause problems, too.
I hope these tips help you get even more than 18K out of your bottom bracket!
I check mine each time I have the chain off. And the point to cartridge bearings is you just buy new bearings for a few bucks instead of a new BB, as I just did for my 80’s Phil Wood, it feels like new again.
I follow the manufacturers maintenance recommendations and grease the hybrid ceramic bearings on my SRAM Red bottom bracket every 100 hours or so. Six years old, like new.
Mr. Langley,
While on the subject of bottom brackets, I wonder if you might have comments about Campagnolo’s current bottom bracket design. It seems to combine certain characteristics of both the cartridge and the loose bearing designs. It does require regular maintenance, but seems relatively east to disassemble. I’ve wondered about the bicycling industry’s assessment of Campagnolo’s current design in theory and practice. I’ve also wondered about how well the ceramic (and steel) bearings are performing and lasting in real-world use. Another related question has to do with bearing replacement; who would be equipped to replace the bearings, and what seem to be typical associated logistics and costs?
Thanks for the great questions, Richard. Campagnolo has been using their Ultra Torque bottom bracket system for quite a few years now https://www.campagnolo.com/US/en/Technologies/ultra_torque It’s a interesting design based on a crank with an integrated spindle that’s actually split in the middle and joined by a through bolt to install the crank on the bike.
The bearings are held on the spindle so that they simply press into the frame cups as the bolt is tightened during crank installation.
As far as I know, the person who invented the split spindle design is Californian bicycle engineer/inventor Tim Brummer of Lightning Cycle Dynamics and he makes the Lightning Carbon Cranks, one of the lightest crankset available https://www.lightningbikes.com/cranks/index.html I ride one on my time trial bike and I reviewed it a while back: https://www.roadbikerider.com/lightning-cycle-dynamics-carbon-crankset-130-carbon-spyder-with-bottom-bracket-d1/
As to the ease of maintenance, there’s not a lot to these cranksets and bottom brackets, so you only need a few tools to install and remove it to access the bearings. They are sealed bearings so you usually replace them when they wear out or become contaminated.
I have used sealed steel and ceramic bearings and have had no issues with either type. Ceramic provides the least friction but riders will not be able to notice a difference from the feel of the pedals. You might if you just spin the crank in a repair stand (no chain), but once you start pedaling it’s hard to feel minor differences in bearing quality.
I think the industry likes the design of these cranks and bottom brackets. Besides Lightning Cycle Dynamics and Campagnolo, Specialized has used it, too – one of the largest bicycle companies. Overall, I believe it’s a very nice system. And, for tools, it depends on which type/brand you have. But the tools should not be too many or too costly – and the maintenance and bearing changes aren’t difficult with the proper tools.
Hope this is helpful,
Jim Langley
One downside to the older square taper BB cartridges is that they can be difficult to remove if you’ve deferred maintenance. I’ve had headache thread seizing problems with aluminum frames and the low-end shimano units with the plastic adjustable cup. How often do people remove these just to make sure the BB threads are not corroded? Also, the square taper units arrive new with loctite on the threads, but I like to grease mine. Which is recommended?
Hi Bert,
Yes, they can get stuck, but usually so long as you have good tools, you can get them out. Heating the bottom bracket can help (the frame BB), but don’t overheat and burn the paint. Penetrants can help, too.
Re the loctite, I usually go with whatever they put on the cup threads from the factory. It won’t hurt to grease the frame threads if you want. The cups are less likely to loosen with the sealed bearing inside the cartridge so grease shouldn’t increase that possibility.
Thanks for the questions,
Jim
I owned a bike back in the 70s and 80s with a Campagnolo Nuovo Record crank. I put over 90,000 miles on the BB with regular maintenance and never needed to replace either the bearings, cups or axle.
Thanks, Kerry. That was a great bottom bracket in my experience, too. I still have a few working just fine. I always thought it was cool that Campy put threads in the holes in the cups so that any grit/dirt would rotate out and away from the insides so it wouldn’t get into the grease and bearings.
And, Campagnolo’s bottom bracket tools are some of the nicest tools I own.
Thanks again,
Jim