I’m again with Matt Harvey from Enduro Bearings for spherical two, all about Backside Brackets!
In the event you haven’t listened to our first chat, I like to recommend it as we go so deep down the rabbit gap of bearings that it’ll give you numerous to consider as you’re making an attempt to optimize your bike.
On this episode, we deal with Backside Brackets as a result of Enduro just lately launched a report that exhibits the outcomes of years of testing many well-liked manufacturers of BBs, however the numbers want some explaining. You’ll discover the charts and a few fascinating knowledge beneath, together with a abstract rationalization to accompany the deeper dive on this interview.
Additionally within the interview are extra enjoyable info about backside bracket bearings, design, and supplies…positively price a pay attention. Large because of Matt for the added explanations!
At first look, this chart makes it seem as if each different backside bracket examined fails miserably, which isn’t the case. I spoke with Matt about this at Sea Otter and we agreed that an in-depth dialog about what these numbers actually imply was so as.
Earlier than you take a look at this chart and suppose that each one of these different manufacturers suck, let’s discuss concerning the facets that result in the efficiency variations, after which additional down I’ll present why this explicit chart is visually deceptive.
The full report is on the market for obtain on Enduro’s web site, however right here’s the gist of it:
- Bearing measurement issues most
- Bearing and Race materials comes subsequent
- Bearing design is final
Bearing Design
The explanation bearing design is least vital is as a result of most manufacturers use the identical or extraordinarily related designs, and since you mainly have solely two choices: Angular Contact, and Sealed Cartridge. The overwhelming majority of manufacturers use Sealed Cartridge and purchase these from a small pool of third events (generally Enduro!), so that they’re largely interchangeable apart from Enduro’s MaxHit, which use a customized, a lot deeper channel for the balls to roll in.
Angular contact is, theoretically, higher, however a lot more durable to setup and preserve, and for many customers, the added work and danger of doing it flawed isn’t price it. We clarify why within the podcast.
Bearing & Race Materials
Enduro’s XD15 materials mixed with ceramic balls is mainly the longest enduring combo you may get, not less than of these examined, but in addition just about total.
Chromium Metal is the least costly and most definitely to corrode, so it requires probably the most upkeep. It’ll put on extraordinarily shortly if water, mud or different contaminants get in there.
440C Stainless is a softer metal than the XD15 however nonetheless good, nevertheless bearing measurement performs a large function in its sturdiness.
Bearing Dimension
Merely put, greater balls roll extra slowly, which implies decrease put on, and so they have a bigger contact patch, which implies higher potential to deal with greater hundreds.
Bearing Design…once more
So, really, close to becoming greater balls right into a bearing, design issues quite a bit. Enduro’s MaxHit merchandise use the shell of the product because the outer race, which frees up room for greater balls.
Relying on the mix of bearing measurement and materials choice, mixed with the situations you trip in and your upkeep efforts, a backside bracket’s sturdiness can go from weeks or months to a decade. Sure, Enduro has had clients placing in hundreds of miles per yr for a decade on the identical backside bracket.
Now, again to that chart…
New bearings, regardless of which of them, will sometimes contribute about 0.25 watts of drag to a motorbike. Added all up in your drivetrain, it’s perhaps 2-3 watts whole, excluding seal drag. It’s not a lot.
Which is why the numbers above threw me at first. On the left are AMPLIFIED watts, not precise watts. And that’s as a result of Enduro needed to amplify the readings by 12x with a view to see a distinction…as a result of energy meters merely aren’t delicate sufficient to measure small fractions of watts.
If we have been precise wattage variations, the chart would look extra like this:
The precise wattage distinction between backside brackets from one of the best case to the purpose simply earlier than failure is round 0.7 watts. Now, when it fails, it fails, however so long as the bearings are saved clear and greased, the distinction in DRAG goes to be minimal.
That doesn’t essentially imply they gained’t develop play and really feel a bit sloppy, however they gained’t achieve a lot drag…till they fail.
The deceptive quantity on the chart is the lifespan. The take a look at was performed with a 360º load on the bearings, however in actuality, BB bearings are solely about 1/3 loaded (on the underside) after we’re pedaling. So, that’s a 3x over actuality.
Subsequent, the load on the bike was equal to a 480lb rider placing out a constant 600 watts, which averages someplace round 4x the load put onto the bearings by a typical rider.
So, if we take a look at even the worst performing BB on the chart failing at ~35 hours and multiply by the hundreds, that’s:
35 x 3 x 4 = 420 hours at 100rpm
420 hours is 210 days of two hour rides, which is not less than a pair years price of driving for many of us. So whereas it could seem like some manufacturers fail a lot ahead of others, the fact is that each one of them final a very very long time.
Why geek out on this?
Effectively, if I’m being sincere, I’m pals with each model on that listing. So after I first noticed this, I’m pondering “Crap, they’re all going to hate me if I publish that chart.” However the extra I checked out it, the extra questions I had. Finally, simply sharing the uncooked chart would do a disservice to you and the opposite manufacturers, so I needed to place it into perspective.
Enduro has a whole lot of feedback within the report for every model, explaining why they suppose some did higher than others. Between this publish, that report, and the podcast interview, I hope you’ll get a greater understanding of BBs and bearings and never be afraid to query what you see. I’m glad I did, and glad Matt’s at all times eager to share his expertise.
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