Tech Talks: Seth's Pre-Load Nightmare - Part 1

Oct 25, 2018
by Pinkbike Staff  
Tech Talks Presented by Park Tool

In this episode, Calvin and Truman pull Seth's well-used bike out of his travel bag and discover that his bottom bracket has had a hard life. Hilarity ensues. Not really, but they do show us the importance of proper spacing, proper bearing preload, and what happens when things are out of whack.

Tech Talks Presented by Park Tool is a monthly video series hosted by Park Tool's own wrench whisperers, Calvin Jones and Truman. The series covers the A to Zs of some of the most prevalent repair jobs, with the last highlighting how to bed in brakes.

Bike Assembly How-To

Views: 7,230    Faves: 9    Comments: 1

Need more Calvin & Truman in your life?

Episode #1 - Tubeless tire installation and conversion
Episode #2 - Saving that bent disc rotor
Episode #3 - Derailleur hanger alignment
Episode #4 - Shimano and Crankbrothers pedal service
Episode #5 - Trailside wheel repair
Episode #6 - Trailside chain repair
Episode #7 - Derailleur limits and cable tension
Episode #8 - Derailleur setup
Episode #9 - Fork wiper seal replacement
Episode #10 - Clipless pedal setup
Episode #11 - New cleat setup
Episode #12 - Top 5 next level shifting issues
Episode #13 - Fixing cassette play
Episode #14 - Gearing hacks
Episode #15 - Fixing sticky pistons
Episode #16 - Lubing fork seals
Episode #17 - A cleat's story
Episode #18 - Tricks of a mechanical mind
Episode #19 - Handlebar Trimming
Episode #20 - Chain Line
Episode #21 - Tools for a trip
Episode #22 - Bedding in brakes
Episode #23 - Direct Mount Chainring Install
Episode #24 - Wheel Balance 101
Episode #25 - Data Under Pressure, Part I
Episode #26 - Data Under Pressure, Part II
Episode #27 - In the pits with professional mechanics

Stay tuned for more mechanical how-to videos with Calvin returning on the last Thursday of every month to show you the easiest way to get the job done. Want to know more? Park Tool's how-to section has you and your bike covered. / @ParkToolCompany


  • 24 2
 Shimano cranks FTW. Ohh so easy to preload. Combine that with a threaded BB-shell and Bobs your uncle Smile
  • 2 0
 Absolutely...only I never got why they have a special spline interface in the fixing bolt. I have replaced that for a unoriginal hex bolt on most of my bikes.
  • 2 0
 Roberts your mother's brother?
  • 2 1
 Shimano BBs use the same external cup spacers and can suffer from the exact same problem they addressed on Seth's RaceFace BB, for the record.
  • 4 0
 @fullfacemike: Sure, but it is easier to adjust on Shimano cranks.
  • 1 0
 @IluvRIDING: Literally the same number of steps. And, as you pointed out, Shimano requires a special tool to adjust preload which RaceFace does not.
  • 1 0
 @chubby5000: Fanny's your aunt!
  • 3 0
 @fullfacemike: yea, but that special tool is included with quality BB tools, and doesn't strip out so I dunno why people are bitching about it.
  • 4 0
 @fullfacemike: there are also way more parts in a race face crank... my Cinch cranks were a nightmare. The integrated crank arm puller was a bit poorly thought out, the outer 16mm allen cap is threaded the same direction as the fixing bolt that presses against it when you pull the crank... so, a bit of dust on the inside of that outer cap and it backs out when you try to pull the crank... NO ONE has 16mm allens locally, it's a very uncommon size. had to order one. That whole issue could have been solved by theading the cap left hand instead of right... engineering 101.

Shimano cranks for the win.
  • 11 0
 I love these guys. From little baby handlebars to this, excellent. Truman is so lucky to work with Calvin, and obviously has the skills. I would LOVE to be able to work with Calvin and just f'ing learn all day err'y day at work.
  • 6 0
 Nice to know I'm not the only mech that doesn't automatically know every BB spacing off my head! Even these guys RTFM every so often. Also I like the acceptance that not everything has to be done by the book to be 'right'..
  • 6 0
 Nice vid, as usual.

Would love to see one about "what to put on that part ?". Like, should you use grease (and what kind), anti seize, nothing...
  • 2 0
 Jury is out on the grease debate. Some grease, some don't.

My philosophy is that all carbon mating surfaces get carbon assembly compound, most everything (other than brake parts and bolts that already have thread compound, and brake/shifter mounts on the bars) gets some water proof synthic grease. Then, go to the lower of the torque range (since, most torques are given for dry install unless otherwise specified) The grease has solved a whole lot of creaking issues and it means bolts will always be removed easily.
  • 8 1
 $400 dollar cranks, $2.99 plastic preloader that strips out all the time... no thanks.
  • 3 1
 I stripped mine too and replaced it with the Cane Creek preload collar. Threads right on, has a titanium bolt, works like a champ. Best $29 you'll spend in a while.
  • 1 0
 After hearing folks with loosening plastic preload collars and stripping threads, I wasn't very confident in mine. So I measured how much gap I had between the collar and crankarm after proper assembly and preloading. Then I made a basic snap-ring with the same thickness as the gap, out of delrin on the lathe. So that is snapped in place between the crankarm and collar. Then, even if the collar isn't tight enough, it can't really walk its way toward the crankarm and loosen things up. With that tweak, mine has been solid and I don't have to worry every ride if it's loosening up. I just have to pop off the snap-ring before servicing. Another option for folks who don't have a lathe in their shop is to find an o-ring that could be squeezed into the gap. It might be hard to get out though!
  • 1 0
 @fullfacemike: Same here. Both my Raceface cranksets have the Cane Creek alloy preload ring. Raceface should be ashamed to used the POS plastic ones on such high end cranks
  • 6 1
 Seth is a little bit ... well, just little comparing to Calvin )))
  • 1 0
 This is great. I checked my rear wheel and it was a little crunchy. Gave it a few taps with a hammer like they showed and now have butter smooth bearing. The front feels like it has a little crunch too but there's no axle going through the bearings to hit. It's a front dtswiss 350, any one know how to adjust preload on those?
  • 2 0
 Damn, they integrated, "Seth's Bike Hacks". Triple threat. "The show to end all shows". I don't think having every tool ever made is very, bike hacky.
  • 4 0
 It is when they're Park Tools
  • 1 0
 @spaceofades: Made me laugh, my Park took is broken.
  • 4 0
 Who else picked the issue at 2:01?
  • 5 1
 still can't get over the fact that Calvin spilled that beer, sorry :/
  • 2 0
 The one good thing about December is taking the poor bike apart, cleaning ,inspecting and fixing the the damage I’ve done over the year.
  • 2 1
 With the fix they were proposing, it solves the pre-load issue but wouldn't the chain line be off? unless this was done to fix the original chain line? any mechanics out there want to chime in on this one?
  • 4 0
 All the work is being done to the non drive side, leaving the chain line that is determined by the spacing on the drive side in this system, alone.
  • 1 0
 The chainline will not change, since the spacer was removed from the non drive side, and not the drive side. The lockring for the chainring will still bottom out on the dust seal of the drive side BB cup, the preload mechanism will just be used to take up the extra slack caused by removing the NDS spacer.
  • 2 1
 Preloading a radial bearing seems to be the wrong thing. You want to eliminate play in the system for sure but preloading should be done only with angular contact bearings.
  • 2 0
 Eliminating play is essentially, preloading. The amount of preload should be the least amount as possible without allowing play. If you do not apply preload you will have play in the system, which will cause bearing skid, noise, excess wear and lead to premature failure. I can thing of 2 places on a bike where the bearings do not require preload. And they are not common, plus they are not ball bearings. Angular contact bearings offer more support for axial loads, but the preload concept is the same.
  • 1 0
 @partsgeek: So most pivot bearings are radial bearings, and the (bb) bearing shown at 1:07 is a radial bearing too. Why would you preload the bb but not pivot bearings?
  • 1 0
 @theteaser: You set preload on many pivot bearings as well. Think Santa Cruz. Id venture to guess that suspension setups that do not factor in bearing preload will usually burn through bearings at a faster rate. Do you agree that a cartridge bearing starts out life with play?
  • 1 0
 You're not wrong. Industry uses cartridge bearings because they're cheap and easy to replace. The right thing to use for most mountain bike applications would be an angular contact bearing, which would require a pre-load. Loading cartridge bearings will just work one side of the race more than the other.
  • 1 0
 There used to be a pretty badass video floating around of some dude down in NZ doing pro bike builds for folks. If I remember right he was doing up a Commencal.
  • 1 0
 I really enjoy stuff like this. I wish I had a multitude of all sorts of spacers to play with.
  • 4 0
 never throw anything away!
  • 1 0
 @jcav5: Agreed!
  • 2 1
 This has Diamondback assembly wrongs all over it !
  • 5 2
 I think its just Seth just being a hack
  • 1 0
 Tech talks. My PB favorite, on par with Claudio's previews ...
  • 1 3
 The fact that those carbon Raceface cranks haven’t failed tells me that Seth isn’t that hard of a rider. I can’t even get the next R version of those not to fail on my XC bike....
  • 1 1
 Yeah. Broke my Next SLs just by having my foot slip off the pedal going over a roller, landed on one foot and snapped the crank arm right at the pedal eyelet.
  • 1 0
 Didn't he say that he ripped a pedal right out of them when he crashed? Not sure I'd call that a failure but he must be kinda riding hard?
  • 2 1
 Where's Randy?
  • 4 5
 Im not sure I trust a mechanic who pours a beer in the trash.
  • 2 0
 I'm like bipolar when it comes to beer, I get totally smashed on like 15, then I'm like, "no alcohol in this house ever again!!!"
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