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Originally Posted by Mad Honk
(Post 22974049)
The quick and easy fix is something that came up regularly, within the Little 500 race bikes. When the front ring was put on the crank arms it was not perfectly centered and produce the tight chain / loose chain issue. The fix is to put the chain in the tight position, and hold the crank arm steady. Then put a cloth on the chain midway between the front and rear sprockets, and push the chain on the bottom section against the top section. That procedure normally centers the front chain ring on the crank and fixes the problem. HTH, Smiles, MH
Are you talking about a chainring with mounting bolts? If so, then I think I understand what you are describing. However, my chainring does not have mounting hardware. If you are talking about solid chainrings that fit onto a 15/16th spindle directly, then maybe a photo would help me better understand what you are describing. |
Originally Posted by maddog34
(Post 22974217)
i'll try again...
"Is it possible that these could be manufactured out of round?" YES! is your crank a one piece, "Ashtabula" type? like this one? https://www.ebay.com/itm/25609923033...029e9154cf723a if so, it is, almost certainly, Manufactured Out of Round... almost ALL of them are manufactured out of round. and they also BEND when the bikes get jumped and /or Crash hard. Not that BMX bikes ever get Abused then Sold.... :rolleyes: you may want to try Re-Centering the Chain ring a few times, testing it each time.. is there any slop to allow a minor re-centering? the "tight spot" will happen when the Ring is out towards the Front of the bike.. tap it back when it's at the "tight spot".. Place a chunk of wood over the teeth with CHAIN IN PLACE, then whack the wood with a hammer... see if it moved. btw... the rear gear/freewheels and hubs are also out of round...they will cause extra-tight and loose spots that don't happen in exact rhythm with the crank turnings... been there a million times, and probably a few more this weekend,... sigh. No. Mine are not Ashtabula type. They are 3 piece. Spindle, & separate splined cranks that bolt on. As for the chainring, no, there was no slop when I installed it. It fit snug, and so no wiggle-room for any potential re-centering. Thanks! |
Originally Posted by Midawi
(Post 22986317)
For now I loosened the chain a bit. It works, but I'm not happy about it as a long term solution.
I'm 90% sure the spindle is bent (or manufactured poorly?), since there was some visible & audible grinding of the chainring happening once per revolution. However, I havent taken the bb apart & the spindle out to confirm this. I don't know if I want to replace it (the spindle or the bottom bracket) since the frame is very heavy at 7 pounds anyway. (Lipstick on a pig!?!?) If I replace the frame with a newer frame it is sort of a can of worms: I will probably need 1) a new fork, right? 2) new cranks, right? (Please confirm!) I'll probably wait a bit until I can find a lighter frame & fork at a good price on Marketplace. I'm in NJ. Are there any shops in my area that have good prices & a decent selection on 2nd hand gear? I'm having fun riding this thing as is, but I'm sure it will be even better 4 pounds lighter! I ordered Demolition Momentum tires too which are about a pound lighter per tire, so 2 pounds. Then potentially another 2 pounds off when I get a better frame. Thanks for any advice or input! https://cimg7.ibsrv.net/gimg/bikefor...9ba2d08b94.jpg Chain as is. https://cimg1.ibsrv.net/gimg/bikefor...992e709c0d.jpg Not sure if you can see much difference, but this is at the loosest spot in the crank revolution. https://cimg3.ibsrv.net/gimg/bikefor...4b27516eb6.jpg And at the tightest spot in the crank revolution. If you don't have chain tugs, they'd be really helpful here, as you can easily pull the axle back 'til the chain just starts to bind, then back it off a bit, center the wheel, rinse/repeat 'til you have the chain as tight as possible without binding. |
Originally Posted by LesterOfPuppets
(Post 22986540)
Looks a little loose, but try doing your chain deflection pics showing the whole drivetrain and only pushing on one run of the chain, not squeezing them both together, also do so in the center of the chain run, not towards the back of it .
If you don't have chain tugs, they'd be really helpful here, as you can easily pull the axle back 'til the chain just starts to bind, then back it off a bit, center the wheel, rinse/repeat 'til you have the chain as tight as possible without binding. But this is as tight as I could get it and still avoid any grinding of the chainring from the chain. So, DEFINITELY not an ideal or long term solution. But it works for now. It is not so loose that the chain will fall off, fortunately. I will take better photos when I can. If I do decide to live with this frame, I will consider getting some chain tugs. They have been a life saver on my cheapo fixed gear bike. But I think it is more likely I'll get a lighter frame eventually, so it is better if I save my money. Thanks! |
Originally Posted by Schweinhund
(Post 22986542)
how many splines? 8 or 48? If 8 and open bearings, then it's 15/16ths. if floating like below then it's a 19mm
If 48 it'll be a floating axle with spacers in the middle of the bb shell. and it'll be 19mm, 22mm, or 24mm Yes, open bearings. So yes, it must be 15/16ths. Thanks! |
Originally Posted by Midawi
(Post 22986486)
Makes sense.
Only one problem in this case. There are no mounting bolts on this chainring. It fits directly onto the spindle (which, as I explain elsewhere in the thread, I am 90% certain is bent.) ..... More significantly, if the issue were a bent spindle, the chainring would have a pronounced wobble. So, consider that maybe there's a bit of wiggle room where it's mounted, and revisit my earlier advice. In any case, some eccentricity is normal. Center the chainring as well as possible, then pull the wheel back so you have minimal slack at th we tightest point. BTW I just noticed the photos. All is good, you should stop obsessing over nothing and ride. |
dude.. you're trying to set the chain too TIGHTLY to begin with... and there's a high probability that the REAR sprocket is also "out of round"...
AND.. that chain looks bone Dry. SMH. |
Originally Posted by Midawi
(Post 22986552)
I believe it is 8 splines. (Definitely wasn't 48.)
Yes, open bearings. So yes, it must be 15/16ths. Thanks! For best results run sealed and a floating axle much closer tolerances. However, one of these would make it better https://www.danscomp.com/odyssey-dyn...01-sv/p1205290 |
Originally Posted by FBinNY
(Post 22986618)
Spindles are both strong and hard. So bent spindles are extremely rare.
More significantly, if the issue were a bent spindle, the chainring would have a pronounced wobble. So, consider that maybe there's a bit of wiggle room where it's mounted, and revisit my earlier advice. In any case, some eccentricity is normal. Center the chainring as well as possible, then pull the wheel back so you have minimal slack at th we tightest point. BTW I just noticed the photos. All is good, you should stop obsessing over nothing and ride. |
Originally Posted by Schweinhund
(Post 22986702)
those hot forged bmx axles for one piece bb are notorious for warping while cooling. not much, just enough. :rolleyes:
BUT It doesn't matter anyway. Days, and often weeks, pass between when parts are cast or forged and subsequently machined. Because manufacturers aren't stupid and don't machine parts until they've finished "settling". Then all machined surfaces, ie. Bearing seats, chainring locating faces, etc. are referenced to each other and do not rely on forging precision. |
Originally Posted by Schweinhund
(Post 22986746)
People like me that fix low end crap to keep people moving......
The precision requirements for chainring concentricity are very low. There's only a problem when expectations are unnecessarily high, as is the case here. |
If the crank spindle were warped enough to affect the chain tightness, it'd almost certainly also make the pedal(s) feel off - i.e., the pedal axle would feel as though it were oscillating, which it would be.
The OP seems to be under the impression that, ideally, the chain should have no slack whatsoever at any point while pedaling. In fact, the general guideline is, and has been since chain-drive single-speed bikes were invented in the 1800's, that the rear hub should be placed such that the chain has 1/4" (or a bit more) of slack where the chain is at its tightest. The assumption being that all but (maybe) the most expensive drive train components have some eccentricity in either the chainring or the sprocket or both. |
Originally Posted by Trakhak
(Post 22986781)
If the crank spindle were warped enough to affect the chain tightness, it'd almost certainly also make the pedal(s) feel off - i.e., the pedal axle would feel as though it were oscillating, which it would be.
The OP seems to be under the impression that, ideally, the chain should have no slack whatsoever at any point while pedaling. In fact, the general guideline is, and has been since chain-drive single-speed bikes were invented in the 1800's, that the rear hub should be placed such that the chain has 1/4" (or a bit more) of slack where the chain is at its tightest. The assumption being that all but (maybe) the most expensive drive train components have some eccentricity in either the chainring or the sprocket or both. Says Ben who's been riding fix gears of a wide range of quality for nearly 50 years and more than 100,000 miles. |
Originally Posted by 79pmooney
(Post 22986803)
Says Ben who's been riding fix gears of a wide range of quality for nearly 50 years and more than 100,000 miles.
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Originally Posted by Trakhak
(Post 22986823)
You and me both. First was a Helyett Speciale track bike in Reynolds 531 in 1964.....
FWIW I hate backlash so I ALMOST zero out slack, and good hardware allows minimal added slack at the worst place. So my rule is to work as close as the hardware allows, never hitting zero. |
Originally Posted by Schweinhund
(Post 22986702)
those hot forged bmx axles for one piece bb are notorious for warping while cooling. not much, just enough. :rolleyes:
Thanks! |
Originally Posted by maddog34
(Post 22986668)
dude.. you're trying to set the chain too TIGHTLY to begin with... and there's a high probability that the REAR sprocket is also "out of round"...
AND.. that chain looks bone Dry. SMH. And the chain has since been lubed, only right after the short test ride I took, on which ride the photos were taken. |
Originally Posted by Midawi
(Post 22987588)
No worries. The chain was recently cleaned thoroughly.
And the chain has since been lubed, only right after the short test ride I took, on which ride the photos were taken. :popcorn |
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