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The one thing I think Sheldon Brown got dead wrong

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The one thing I think Sheldon Brown got dead wrong

Old 09-06-21, 01:18 PM
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mrmb
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The one thing I think Sheldon Brown got dead wrong

Chain tension on a fixed gear set-up.

He says to set it up as tight as possible without binding. To make matters worse, he does not explain his definition of binding. I used to do it this way, and it was a mess.

My experience is that the chain should be as loose as it can be without there being a possibility of the chain derailing. This is how I do it now and things run so much smoother.

What do you think?
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Old 09-06-21, 01:38 PM
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How was it "a mess"? The sweet spot for chain tension isn't the same for everyone, and what you might like can be hard to express in words or numbers.

Personally, I can't stand when there's a bunch of slack in the chain. Somewhere in Sheldon's instructions he talks about keeping a small amount of droop in the chain and not feeling extra resistance at the tightest portion of the crank's rotation. I like to put the bike on a stand and watch the top run of the chain from behind as I spin the cranks. Done right, the drivetrain spins as freely as if the chain were super-loose, but with no more slack than absolutely necessary.
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Old 09-06-21, 01:44 PM
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Loose is fast. Like the OP said I like as loose as possible while not being able to push it off the chainring w/ your peanut butter wrench. I set my bmx bike up more like what Thermonic posted because the rear axle is below the chain stay quite a bit and my normal loose set up would have the chain hitting the stay.
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Old 09-06-21, 01:49 PM
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The looser the chain, the faster it all wears out. You only have 1 link/tooth at a time taking the pedaling force. Just short of binding and many links are sharing the load.

Biggest problem is cheap bikes where the sprockets aren't running round. The chain goes slack then tightens, and repeats for every pedal revolution. Most common on chinese made bikes with 1 piece cranks. When the chain binds, it puts tremendous pressure on the bearings and destroys them pretty quick. On those you find the tight spot and adjust from there.
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Old 09-06-21, 02:10 PM
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Maybe your loose as it can be without coming off is about the same as his tight with out binding.

At best you are just on opposite ends of a very narrow range that provides good results.
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Old 09-06-21, 03:18 PM
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Originally Posted by rickpaulos View Post
The looser the chain, the faster it all wears out. You only have 1 link/tooth at a time taking the pedaling force. Just short of binding and many links are sharing the load.

Biggest problem is cheap bikes where the sprockets aren't running round. The chain goes slack then tightens, and repeats for every pedal revolution. Most common on chinese made bikes with 1 piece cranks. When the chain binds, it puts tremendous pressure on the bearings and destroys them pretty quick. On those you find the tight spot and adjust from there.
I beg to differ. The tighter the chain the quicker the BB and rear hub (and/or freewheel/freehub) bearings will wear out. The tension set up you suggest will only share chain roller/tooth sharing (of the stress) until the chain wears and then you're back to where only one tooth/link sees the stress. I'll also speculate that when the chain is under tension (with no pedal forces) it and the cog are both wearing even when soft pedaling. So in my experience a too tight chain has more friction, wears faster, makes more noise and the only possible redeeming advantage is it won't tend to derail when raggedly powering the bike. Andy (waiting for the flames to start)
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Old 09-06-21, 04:12 PM
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I like to be able to move the upper run of the chain up/down by about 1-2cm at the midpoint between the crank and the rear sprocket. Looser than that, and I get annoying lash when I change pedal cadence. Tighter than that, and bearings will wear quickly. It's important to check this slack for the entire rotation of the crank, as chainrings (particularly inexpensive ones) are not necessarily perfectly round. You may get it perfectly set in one position, but rotate the crank some, and it becomes excessively tight. Set it so you get the 1-2cm slack at the tightest point in the crank rotation.
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Old 09-06-21, 04:49 PM
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Originally Posted by Andrew R Stewart View Post
I beg to differ. The tighter the chain the quicker the BB and rear hub (and/or freewheel/freehub) bearings will wear out. The tension set up you suggest will only share chain roller/tooth sharing (of the stress) until the chain wears and then you're back to where only one tooth/link sees the stress. I'll also speculate that when the chain is under tension (with no pedal forces) it and the cog are both wearing even when soft pedaling. So in my experience a too tight chain has more friction, wears faster, makes more noise and the only possible redeeming advantage is it won't tend to derail when raggedly powering the bike. Andy (waiting for the flames to start)
^This^ A tight chain wears everything out faster.
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Old 09-06-21, 04:54 PM
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Originally Posted by JohnDThompson View Post
I like to be able to move the upper run of the chain up/down by about 1-2cm at the midpoint between the crank and the rear sprocket. Looser than that, and I get annoying lash when I change pedal cadence. Tighter than that, and bearings will wear quickly. It's important to check this slack for the entire rotation of the crank, as chainrings (particularly inexpensive ones) are not necessarily perfectly round. You may get it perfectly set in one position, but rotate the crank some, and it becomes excessively tight. Set it so you get the 1-2cm slack at the tightest point in the crank rotation.
This sounds right to me.
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Old 09-06-21, 05:18 PM
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Originally Posted by rickpaulos View Post
The looser the chain, the faster it all wears out. You only have 1 link/tooth at a time taking the pedaling force. Just short of binding and many links are sharing the load.

Biggest problem is cheap bikes where the sprockets aren't running round. The chain goes slack then tightens, and repeats for every pedal revolution. Most common on chinese made bikes with 1 piece cranks. When the chain binds, it puts tremendous pressure on the bearings and destroys them pretty quick. On those you find the tight spot and adjust from there.
The tension changes with both pedal revolutions and cog revolutions. Unless the chainring and sprocket have an integer ratio, like 36:18 or 48:16, it will take numerous crank rotations to get to all of the combinations of positions in order to to find the true tight spot.
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Old 09-06-21, 05:21 PM
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Iím sure he knew how to tension a bicycle chain. But perhaps he didnít describe it so that everyone understands the same way. Tensioning a roller chain is not hard if you understand it. Explaining it to someone that has no understanding of one may be.

if Brown had a YouTube channel I think he would have been able to demonstrate.
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Old 09-06-21, 07:54 PM
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Originally Posted by Iride01 View Post
Maybe your loose as it can be without coming off is about the same as his tight with out binding.

At best you are just on opposite ends of a very narrow range that provides good results.
^ As usual, someone found a much better way to say what I was trying to.
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Old 09-07-21, 08:44 AM
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pump your brakes kid. that man is a national treasure.
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Old 09-07-21, 09:57 AM
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It's not just chainrings that can be out of round. I have at least one all-city rear sprocket that isn't radially true. I also have a mavic ellipse rear wheel where one side is unusable because the sprocket mounting threads are so far out out of being radially true. I also prefer a loose set up since it takes the load off the hub and BB bearings and spins faster. It's also more tolerant of less than smooth pedaling.
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Old 09-07-21, 10:14 AM
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For background, I've been riding fix gear a long time. Like quite a few laps around the planet's worth of miles.

The chain should NEVER go tight. There is quite a large window between just acceptably loose and too loose and danger of coming off BUT both of those "end points" are determined by the quality (and wear level) of the setup. The more round the crankset and BB are, the tighter you can run the chain. (Velodrome quality cranksets are a joy. Virtually no change throughout the crank circle in chain slack.) Worn or poor chainrings can be far more prone to the chain falling off and require less slack. It is possible to have low enough crank quality and a poor enough chanring that the sweet middle ground cannot be reached. Also, not all cogs are equal in retaining slack chains.

For these reasons I run only 1/8" chains, rings and cogs. I run only Izume Eco or better chains, EurAsian cogs (well, I have a couple of Dura-Ace from years ago and other brands for the big cogs EA doesn't make). Cranksets vary a lot. Two are 110 BCD on my commuter and my Mooney. The Mooney so I can run an 1/8" triple, 46-44-38. The bike of my logo has a Sugino 75, a pure joy, Never have to seek out the tight spot. I flip he wheel most rides and it is so easy. Oh, smooth running and a securely seated chain are not one and the same and to some extent, at odds with each other. I run the Izumi and EU because both use squared off shapes - very resistant to dropping chains; as far from the modern "shaped" teeth as you can get and also quite noisy. I have a Surley cog that runs silent that I will only only use on the best bike with its Sugino 75 crankset so I can comfortably run the chain tight enough to stay on that "slippery" cog.

Yes, I know I sound like an elitist with what I run but I did many years on far cheaper setups. I've dropped a few chains, skidded through a few tires and walked home a few times. Luckily never crashed from dropping a chain. Also gone close to 50 on those cheap setups. (It was a time in my life when I was going to go drugs, institutions, death by my own hand or crazy fix gear. I don't regret my choice but that higher being was looking after me.) Running those EU cogs and Izumi chains now might cost more to get on the road, but they both last a long time and are far safer on those descents. (I'm also a lot closer to sane and keep my RPM within reason.)

Oh, a note on slack chains and speed - go to any velodrome and observe what the good riders ride. You won't see tight!
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Old 09-07-21, 10:49 AM
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Piggy-backing off that last post: since my fixed-gear conversion runs a mish-mash of parts (Surly cogs but a Sugino GLP road crank and "road" 45T or 42T ring depending on the season) there is some tension variance. I "characterize" it by installing the chainring so that the tightest point is with the drive-side crank arm pointing forward. That way, if I have to fix a flat on the road, I can point that crank arm forward when reinstalling the wheel and the chain won't get any tighter than that while riding.
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Old 09-07-21, 01:42 PM
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As 79pmooney posted the quality of your gear makes a big difference. I used Sugino 75 rings and EAI cogs as well. There are actually quite a few national teams that use the Euro Asia cogs, surprising how many you see wandering around the infield at a World Cup. Super high quality, very round.
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Old 09-07-21, 07:06 PM
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It would be so cool if Sheldon were still around to chime in on this thread. It was awesome to be on this forum when he would sometimes show up and comment. I'm pretty sure he never really saw himself as the end-all authority on anything, he was just a very intelligent guy who knew one helluva a lot about bicycles. He put a lot into sharing that knowledge on this forum, and especially on his website, and I've always thought that was really nice. I have no idea what he would say if he were here to reply to this thread, but it would surely be interesting, and I wish he could.
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Old 09-07-21, 07:20 PM
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Originally Posted by Chuck M View Post
if Brown
One thing I know for sure that Sheldon would have said, and it was what he always said in response to someone calling him by his last name on this forum:
"'Sheldon, please'."

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Old 09-08-21, 09:29 AM
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Originally Posted by cxwrench View Post
^This^ A tight chain wears everything out faster.
Iíd rather replace a chain than any of those other components.
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