What's causing your bearings to fail prematurely
At Kogel we have recently seen an uptick in warranty claims that surprised us. For the last 8+ years, our warranty volume has been steady between 2 and 3%. That number is the reason why we offer the best warranty in the industry: 2 years with very few questions asked. Ball bearings are wear items, just like grips, tires, and chains. To guarantee them for 10 years makes no sense at all and indicates that a company will probably make you jump through a few hoops before they grant your claim.
Our aforementioned warranty claims are few and they are predictable. The recent claims that surprised us are from bearings that started creaking within a few hundred miles of being installed. We’re talking about practically new bearings that should be nowhere near the end of their lifespan. So what has changed? Let’s analyze the reasons why bearings can disintegrate within hours after installation.
Cause #1: Too Many Spacers
Even though Kogel’s motto is "any crank, any frame, no adapters", most cranksets are designed to be installed with spacers on the spindle. Sram DUB is an obvious one that comes to mind. Even though there are guidelines on which spacers to use and how many, our experience is that following the chart puts you in the right ballpark, but is not completely accurate. Some trial and error by your mechanic is required.
Radial ball bearings, which are in most bottom brackets, are built to run with zero preload. None. Nada. The goal during installation is to set up the system to the point where the spacers and preload adjuster find the exact sweet spot between too wide (axle can rock back and forth between the bearing cups) and too tight (when tightening down the bolts, the spacers compress the bearings).
While too wide is very easy to spot, a crank that is set up too tight is less obvious. Everything looks fine until you start tightening the crank bolts and all of a sudden the crankset only free spins one and a half revolutions on fresh road seals. Back off the bolt and the cranks spin freely again.
The solution on Sram cranks is to start with a crank set that is slightly loose after torquing the crank bolt, then take up any additional tolerance with the preload adjuster. On Shimano cranksets, the best practice is to tighten the preload bolt, then once it bottoms out, back off the bolt half or a quarter turn just as a security measure. Remember for any crankset, the goal is to find the sweet spot between play and compression.
Cause #2: Frame Misalignment
If spacers aren't the issue, a misaligned bottom bracket shell in a frame is nothing new. Everyone has heard of Pressfit frames where one side of the BB cup is higher than the other, or the two do not precisely meet at a 180 degree angle. We’ve all heard the horror stories, and production errors like these are virtually impossible to prove with tools that are available in a bike shop.
In the last two years we have seen an increase of these flawed frames making it out of production and to the end consumer. In the post-covid world, many items produced overseas have dropped in quality or at least in the QC procedures executed at the factories. I have personally seen clear examples in appliances.
After purchasing a new stove and fridge, both were delivered in pristine boxes. Upon removing the packaging, the oven was so crooked that the rack did not fit inside, as it was so far off square that the rack could not engage with the mounting points. A fridge in a separate delivery looked like someone backed a forklift into it. Doors would still close, but were severely dented. The protective film however, was carefully applied across the damaged areas, making sure to not leave any air bubbles. At least someone at the production facilities was doing a good job that day. I guess the point of my story is that in the age of product shortages across all industries, manufacturers are forced to drop their quality standards or accept even larger shortages.
We have seen frames that were fine while using a plastic bottom bracket with loose tolerances but then started acting up after the customer installed a high precision bottom bracket that does not allow the loose tolerances in the BB to compensate for the misaligned frame. All of a sudden, the bearings fail within hours, not because of the bearing quality, but because of unusual loads put on them through misalignment.
Kogel’s solution is to offer plastic bearing inserts as an after sale option. The fit of these is a bit more relaxed compared to our aluminum inserts and allows for a slight misalignment between the left and right cup.
Cause #3: Bearing Insert Too Tight
Since we typically use aluminum inserts in our bearings instead of plastic, the tolerances on these sleeves need to be extremely tight. Aluminum just does not stretch in the same way a composite material typically does.
While we make every effort to build the perfect bottom bracket and then test each one on a crank set in our office before shipping, it occasionally happens that the crank spindle does not easily slide into the bottom bracket. A few light taps to install the crankset is acceptable, but if it needs whacking rather than tapping, you need to have a look at what's going wrong. This could happen when a Kogel bearing insert that is at the lower end of the tolerance meets a DUB spindle that is at the higher end of the tolerance. We only have a few hundredths of a millimeter to play with.
Imagine the bearings being crushed from both sides: they are pressed into the cups and the cups into the frame, then the spindle is pushing outwards from the inner race. The entire bearing can get compressed. It will still run for a little bit, but you can probably tell it is not as smooth as the Kogel promo videos. Compressing the bearing will lead to failure. Instead of smoothly rolling across the races, the balls are now crushed into them.
While installing the crankset, there is a way to determine if the problem is misalignment or tight inserts. Try installing the crankset as you would always do.
- If the spindle is hard to get through the first bearing, the insert is probably too tight for your crankset.
- If the first one is fine and the second one is hard, it can be either a tight insert or a frame misalignment. Take the crank out and stick the spindle in from the opposite side. If it slides in smoothly, it is probably a frame issue, if it stops and needs a hammer, a new aluminum or plastic insert will fix your problem.
Cause #4: Incorrect Tools Used
We just published an entire article about installing bottom brackets with incorrect tools. Please find it [here] . I will not repeat all the details but I will repeat the title of the article: Your homemade bearing press is a recipe for disaster.
Bottom brackets can be severely damaged if they are installed with improvised tools. Ask some questions when you drop your bike off at the shop about their bearing press tools. You should see a huge range of drifts for every bottom bracket and wheel bearing size. If your shop just has a single press with one or two drifts on it, it is probably better to take this job elsewhere.
Destroyed bearings might run well for a week or so, but after that they will deteriorate fast.
What happens if my bearings fail prematurely?
If your Kogel Bearings fail in a very short period of time, please do not be upset if we ask some questions when you call in for a warranty. There are a few things we need to find out before we provide you with the best solution, even if the best solution is to send your frame in for warranty with the manufacturer.
Kogel’s Guaranteed Performance slogan means our team will always take care of you to the best of our abilities.