Noob Q - chain "movement" while coasting?

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7/8/2014 8:15 AM

I got my kid a used MCS Holeshot for racing. It looks to be in decent shape, but there's something I don't understand going on with the rear wheel/freewheel.

When it's in a bike stand and coasting/freewheeling I notice the chain "moves," it basically gets tighter and looser. I don't understand how that's possible if everything is perfectly round, but it's obviously happening. I looked at another, older bike and I see it doing the same thing, but not quite as much.

Is there a word to describe this? Is it more common on lower-end bikes or do all bikes do it? Is it anything to worry about?

The rear hub doesn't sound great when it's coasting on the stand, it sounds kind of crunchy, but it spins pretty smoothly.

Thanks for any tips you can send my way.

-Mike

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7/8/2014 9:11 AM

It's the sprigs and pawls in the hub. There is un even tension between the pawls and the engagement ring. This isn't a problem, but if your paranoid you should grease the hub or even replace the springs. Your issue may also cause the bike to pedal by itself when your walking it around.( aka ghost pedal)

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Ref: Mario.villegas90, Williambreathes

7/8/2014 9:14 AM
Edited Date/Time: 7/8/2014 9:15 AM

There may be a little play in the pawls/springs of the rear hub, which allow a little fluctuation like that. It is incredibly common in racing (mostly because people pay attention to everything), especially with a 2 piece driver that can accomodate different sized cogs. If the bearings in the driver are even SLIGHTLY off axis on the axle, this can also show up.

Try cleaning out the driver and rear hub area, check ALL bearings for stiff spots or play as well.

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"Hey anybody ever make that mistake like right when you wake up in the morning and you believe in yourself?" -Kyle Kinane

"BIKES!" -Tom Segura

7/8/2014 11:15 AM

This is great info, thank you! I was getting some ghost pedaling, the freewheel wasn't spinning very freely, but that mostly went away after I put some tri-flow in it (dripped through the gap on the dust cover). I know that's not a real solution, but I wanted to see if it would help.

When you guys refer to checking and greasing bearings and springs, are you talking about the ones in the freewheel, the hub (the axle cups/cones/bearings), or both? The pawls/springs would only be in the freewheel... I'm thinking a new freewheel might be a decent investment, since I don't think they're too expensive, and I don't have any experience trying to overhaul a freewheel (regular hub bearings, yes, freewheels/freehubs, no).

Again, thanks for the replies!

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7/8/2014 12:32 PM

tmnutan wrote:

This is great info, thank you! I was getting some ghost pedaling, the freewheel wasn't spinning very freely, but that mostly ...more

Now before I start, is it a freewheel or a cassette hub? The difference is that a freewheel threads onto the hub, and the cassette uses the internals for the hub as part of the mechanism.

Freewheels are typically cheaper in price, however they use smaller internals and fail more often.

Cassettes cost more but have more interchangeable parts.

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"Hey anybody ever make that mistake like right when you wake up in the morning and you believe in yourself?" -Kyle Kinane

"BIKES!" -Tom Segura

7/8/2014 12:33 PM

But greasing anything that moves against another part is always a good idea.

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"Hey anybody ever make that mistake like right when you wake up in the morning and you believe in yourself?" -Kyle Kinane

"BIKES!" -Tom Segura

7/8/2014 12:49 PM

I'm almost certain it's a freewheel, one of the 4-prong (notch?) kind. I say "almost" b/c I'm not familiar with cassette hubs on BMX bikes (but I know what they look like on MTB and road bikes). It's a relatively inexpensive bike, the hub is some no-name thing that came on an MCS bike. The non-drive side of the hub is also threaded, I guess just in case you want to put a different size freewheel on the other side and be able to flip-flop. Does that help?

I've pulled the cranks, BB, headset, and stem bolts and greased everything, but I haven't touched either hub yet.

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7/8/2014 4:02 PM

tmnutan wrote:

I'm almost certain it's a freewheel, one of the 4-prong (notch?) kind. I say "almost" b/c I'm not familiar with cassette hubs ...more

Yep!

Triflow or other lubes will help smooth things up. Ultimate worst case, you need a new freewheel, and they are typically about 20-25 bucks.

The springs are inside the freewheel in this setup, so you don't have to worry about adjustment on those, just a little triflow into the freewheel for now.

Bearings get some triflow when you put it into the freewheel too, BUT there are bearings in the hub as well, don't neglect those.

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"Hey anybody ever make that mistake like right when you wake up in the morning and you believe in yourself?" -Kyle Kinane

"BIKES!" -Tom Segura