reversing worn chainrings

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reversing worn chainrings

Postby jules21 » Sat Jul 21, 2012 5:53 pm

can you reverse chainrings?

i'm building a bike up out of old spares which i intend to give to my brother for a xmas pressie and am looking at whether to buy a new crankset or whether i can get away with reversing the worn rings on an old crankset.

so far i've discovered that:
1. the mounting points and teeth are not in the same plane, so when you reverse a chainring, the spacing between the next one (this is a triple chainring) goes out of kilter. i'm thinking maybe i can pack it out with a thin washer?
2. there is a pin on the outer face of the outer chainring, which seems to stop the crank arm from fouling the chain ring (can't see that happening though?) when i reverse the chainring, the pin is then on the inside and would block gear shifts between middle and outer ring. solution - 30 secs. on bench grinder
3. the chainrings have 'profile shifting' ramps or whatever shimano calls them, presumably to smoothen shifts between chainrings. reversing them would mean losing the benefit of those - no big deal i'm thinking?

has anyone else tried this? spare chainrings are not that cheap and my brother isn't about to enter the Tour de France so i thought i'd save a buck.
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by BNA » Sat Jul 21, 2012 6:00 pm

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Re: reversing worn chainrings

Postby trailgumby » Sat Jul 21, 2012 6:00 pm

The pin on the outside of the big ring is to stop the chain jamming under the crank on an over-shift. I managed to overshift somehow this week, with a car up my clacker. I'm very glad the pin was in the right spot. :D

I'm not sure I'd contemplate the idea. Maybe upgrade yours now and give him your hand-me-downs :idea:

On the other hand, if you really don't like your brother ... go for it ;)
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Re: reversing worn chainrings

Postby jules21 » Sat Jul 21, 2012 6:05 pm

trailgumby wrote: The pin on the outside of the big ring is to stop the chain jamming under the crank on an over-shift. I managed to overshift somehow this week, with a car up my clacker. I'm very glad the pin was in the right spot. :D

so it is.. oh well, his problem ;)

trailgumby wrote: I'm not sure I'd contemplate the idea. Maybe upgrade yours now and give him your hand-me-downs :idea:

mine's pretty new Deore. this is my commuter bike so i don't really do upgrades, it's too expensive to put quality bits on it, as i wear them out pretty quickly. chainrings last ~ 1 year.

trailgumby wrote: On the other hand, if you really don't like your brother ... go for it ;)

could be funny :)

i've still got a bit of time to play around before i hand it over.
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Re: reversing worn chainrings

Postby trailgumby » Sat Jul 21, 2012 6:14 pm

Maybe just stick a matching worn chain on it?
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Re: reversing worn chainrings

Postby jules21 » Sat Jul 21, 2012 6:16 pm

trailgumby wrote:Maybe just stick a matching worn chain on it?

i replace my chainsets when they will not transmit any decent torque anymore, with a worn chain. they're pretty useless by that stage - they just slip.
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Re: reversing worn chainrings

Postby foo on patrol » Sat Jul 21, 2012 6:17 pm

Plus the rings are recessed for the ummmmmmm I can't remember the correct name for them :oops: but the bolts that hold them in place!

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Re: reversing worn chainrings

Postby Oxford » Sat Jul 21, 2012 6:26 pm

short answer - No
long answer - No

unless you're SSing the bike or going 1x??, even then, the profile of the teeth will cause problems.
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Re: reversing worn chainrings

Postby il padrone » Sat Jul 21, 2012 7:06 pm

Yes, if you're running Rohloff, Alfine or SS and you have a Thorn chainring (designed for reversability - no ramps or pins, and the ring is symetrical side to side)

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Re: reversing worn chainrings

Postby Mark Kelly » Sat Jul 21, 2012 10:53 pm

Don't cut the chain drop pin off, drill it out from the other side with a 2.5mm drill. You can then tap it to M3 and install it on the other side of the ring. To keep it clean, use a countersunk screw.

I did this when I was fitting new 10 speed rings to an old C-Record crankset and didn't want to pay Record prices. The C-record cranks' arm position differs from the usual crankset so the pin ended up 36 degrees out of kilter.
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Re: reversing worn chainrings

Postby rkelsen » Sun Jul 22, 2012 9:39 am

You probably shouldn't reverse alloy chain rings.

When the current one on my 1x8 setup wears out, I'm going to replace it with a stainless steel one. These have a longer life, and are reversible on top of that.
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Re: reversing worn chainrings

Postby ozdavo » Sun Jul 22, 2012 8:14 pm

Maybe try a WTB thread. There are plenty of guys on hear with lots of old parts. I've got a couple of old NOS Shimano 5 bolt MTB Chainrings that I'd give you for post cost if they suit.
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Re: reversing worn chainrings

Postby jules21 » Sun Sep 30, 2012 10:37 am

ok i can confirm reversing the chainrings doesn't work :)

the chain still slips
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Re: reversing worn chainrings

Postby ironhanglider » Sun Sep 30, 2012 12:52 pm

Ribble usually stocks Stronglight chainrings which are pretty cheap.

Keep your eye out though sometimes whole cranksets on sale are cheaper. I have been known to buy a crankset just for the rings before.

Cheers,

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