Rotated crank arms 90 degrees...
10-21-18, 09:35 PM
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Rotated crank arms 90 degrees...
I test-rode an older Miyata that made a funny little rattle & squeak twice during each full rotation of the chainrings.
The chain was oily and gritty like the bike had been ridden in sand.
I checked out the larger alloy chainring and noticed that the sprocket teeth had not worn evenly.
There were two areas on the chain ring about 180 degrees apart where face and flanks of the chain ring teeth were more worn and two areas about 180 degrees apart where they were less worn.
(( The chain rings were the round type, not the oval BioPace type. ))
Is this a thing to do, like rotating your tires on your car ??
Binky
The chain was oily and gritty like the bike had been ridden in sand.
I checked out the larger alloy chainring and noticed that the sprocket teeth had not worn evenly.
There were two areas on the chain ring about 180 degrees apart where face and flanks of the chain ring teeth were more worn and two areas about 180 degrees apart where they were less worn.
(( The chain rings were the round type, not the oval BioPace type. ))
Is this a thing to do, like rotating your tires on your car ??
Binky
Last edited by Binky; 10-22-18 at 04:18 PM.
10-21-18, 10:13 PM
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You've only rotated the cranks on the spindle. That will do nothing for the alignment of the teeth on the chainring.
It may help with pitting on the bottom bracket spindle. On a vintage bike, it never hurts to periodically pull the bottom bracket apart, clean, lube, and re-adjust the cones.
As far as the wear on the chainrings. I've noticed that too, especially on the small ring. You usually have a 5 bolt chainring, so you can't really rotate 90 degrees, but you can rotate forward one notch periodically. Remove the 5 chainring bolts, and rotate the two rings forward.
You will run into issues that the outer ring often has a drop-stop peg which is only in one place. So, rotating the ring, you'll get that peg in the wrong spot (you can remove it if you wish.
Also, newer rings are designed to be synchronized, so they should be rotated pairwise.
The rings may have a countersink for the chainring bolts, but some people have also reported success in flipping vintage rings and running them backwards (not appropriate with modern rings with pins and gates).
It may help with pitting on the bottom bracket spindle. On a vintage bike, it never hurts to periodically pull the bottom bracket apart, clean, lube, and re-adjust the cones.
As far as the wear on the chainrings. I've noticed that too, especially on the small ring. You usually have a 5 bolt chainring, so you can't really rotate 90 degrees, but you can rotate forward one notch periodically. Remove the 5 chainring bolts, and rotate the two rings forward.
You will run into issues that the outer ring often has a drop-stop peg which is only in one place. So, rotating the ring, you'll get that peg in the wrong spot (you can remove it if you wish.
Also, newer rings are designed to be synchronized, so they should be rotated pairwise.
The rings may have a countersink for the chainring bolts, but some people have also reported success in flipping vintage rings and running them backwards (not appropriate with modern rings with pins and gates).
10-22-18, 06:39 AM
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Yes, your rotating the crank arms on the spindle did absolutely nothing toward redistributing the wear pattern on the chainrings. Also, CliffordK's warning is correct that rotating the chainrings themselves relative to the crank arm will eliminate the chain-drop pin's protection since that pin is typically on the big chainring.
Finally, it is very likely that the "worn" chainring teeth you are seeing are intentionally made that way to enhance shifting performance. That's a feature, not a bug.
Finally, it is very likely that the "worn" chainring teeth you are seeing are intentionally made that way to enhance shifting performance. That's a feature, not a bug.
10-22-18, 09:39 AM
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Yes, your rotating the crank arms on the spindle did absolutely nothing toward redistributing the wear pattern on the chainrings. Also, CliffordK's warning is correct that rotating the chainrings themselves relative to the crank arm will eliminate the chain-drop pin's protection since that pin is typically on the big chainring.
Finally, it is very likely that the "worn" chainring teeth you are seeing are intentionally made that way to enhance shifting performance. That's a feature, not a bug.
Finally, it is very likely that the "worn" chainring teeth you are seeing are intentionally made that way to enhance shifting performance. That's a feature, not a bug.
Right....
Thanks guys.
Bink
