Magnum Metro: Freewheel Clanking!

L

LeftieBiker

100 kW
Joined
Nov 5, 2012
Messages
1,107
I've had this bike about 9 months, now. It has a Shimano Acera 8 speed, with a Das Kit 500 watt geared rear hub. Since it was new I've noticed that the freewheel will sometimes CLANK more loudly when engaged than my other bikes, but it is worse this Spring. I put it up on the stand last night, to make sure the derailleur was working properly, and it is. I lubed the chain and derailleur while I was at it. The noise is pretty clearly coming from the freewheel, but it is only happening on engagement - no slipping or juddering under load. I'm not in great health, so it's possible that I'm not keeping absolutely constant pressure on the pedals, but this has never been a problem before...

So, any similar experiences? Any suggestions to smooth it out? The bike is under warranty for another three months, and I'm also wondering if there is little or no grease in there...
 
I'm not sure what you are talking about, with the clank. It could be just slipping because of stuck pawls. Once a year or so, I just pour a bunch of motor oil into freewheels. Not the best method, but it flushes out the sand that packs in there when you ride in western desert.


Then of course, it pukes oil for a week or more, which means lots of clean up.


Remove it and replace is easy, once you have the tool. Or remove, clean, lube, replace.
 
What I'm experiencing is a fairly loud, metal-on-metal sound as the freewheel engages. Not a grinding sound, but the aforementioned CLANK, like tapping a solid piece of metal with a ball peen hammer. It doesn't do it until after I've ridden 5 miles or so, although I can reproduce it on the stand just by engaging the freewheel with the pedals. It feels to me like there should be grease in there, but isn't. It's starting to damage my riding enjoyment...
 
Except for a few that can be opened for servicing, freewheels usually don’t last very long. They last longer on pedelecs, and only one season on fast ebikes because they freewheel all the time.
 
The cheap freewheel that came with my bike did something similar. If you wiggled it, you could see that it would wobble a bit on its bearings. I just replaced it with a DNP freewheel and all has been fine. It also shifts nicer since the DNP has ramped tooth profiles and the cheap Chinese one that came with my kit has conventional straight teeth.
 
My bike only has about 1200 miles on it, is less than 10 months old, and I pedal all the time while riding. I really hope it isn't going to have to be taken apart. It's under warranty, but all Magnum is likely to do is send me another crappy OEM freewheel...
 
LeftieBiker said:
My bike only has about 1200 miles on it, is less than 10 months old, and I pedal all the time while riding. I really hope it isn't going to have to be taken apart. It's under warranty, but all Magnum is likely to do is send me another crappy OEM freewheel...
Click to expand...

Well, see if the new one is better. Maybe the original one was defective. Hard to say with a sample of one. The freewheel that came with my kit was junk but maybe I got a bad one? The DNP has been better in every way. If the OEM replacement doesn't fix things, consider going with a DNP.
 
The only 8 or 9 speed freewheels I would bother with these days are made by SunRace.
 
Chalo said:
The only 8 or 9 speed freewheels I would bother with these days are made by SunRace.
Click to expand...

Chalo has way more experience with freewheels than I have. So go with his advice if you end up changing away from the OEM and especially consider doing so if you don't need a small tooth high gear on the freewheel. SunRace may very well be much better than the DNP freewheel. But the DNP is a LOT better than the crappy freewheel that came with my kit.
 
http://www.sunrace.com/en/products/detail/mfe60

That's 13-34 8-speed.

They also make 11-32 9-speed and 11-36 10-speed freewheels. These require different shifters, but they are all the same overall width.

EDIT:

I just looked up "Das kit 500W". That is NOT A FREEWHEEL. It's a cassette, meaning the ratcheting part is integral to the hub. It's probably both janky and proprietary, because it's not made by a legit cycle components maker.

I say, contact the seller and see if they can supply replacement freehub bodies and any special tools or guidance on replacing them. It looks like it might be a Bafang motor, which would be good news.
 
When you say "integral to the hub" do you mean that the whole hubmotor assembly would have to be replaced? You later seem to imply that it can be replaced, with special tools. I'm confused...
 
LeftieBiker said:
When you say "integral to the hub" do you mean that the whole hubmotor assembly would have to be replaced? You later seem to imply that it can be replaced, with special tools. I'm confused...
Click to expand...

There is a difference between a freewheel and a freehub/cassette. The freehub has the ratchet system as part of the hub or in this case, hub motore. The gear cluster or cassette slides onto the freehub. A freewheel combines the ratchet system and gears as one unit that screws onto the hub or hub motor.
 
LeftieBiker said:
When you say "integral to the hub" do you mean that the whole hubmotor assembly would have to be replaced? You later seem to imply that it can be replaced, with special tools. I'm confused...
Click to expand...

Cassette freehub bodies are part of the hub, and often specific to a single kind of hub. This is especially true of those used on hub motors, because hub motors have oversized axles, and extra room must be accommodated inside the cassette spline. Shimano made the first successful cassette freehubs, and they're still the best in the business. The farther off in the off brands you go, the more likely the freehub body is to be unreliable junk.

Screw on freewheels are pretty much universal, at least in terms of thread mounting. Spacing for multiple speeds is another matter.

https://www.sheldonbrown.com/free-k7.html
 
Shimano made the first successful cassette freehubs, and they're still the best in the business. The farther off in the off brands you go, the more likely the freehub body is to be unreliable junk.
Click to expand...

The bike has a Shimano Acera 8 speed derailleur drive. Are you saying that the cassette isn't provided by Shimano, and that I have to find a cassette specific to the hubmotor (which, BTW, is stamped "Das Kit") and not to the derailleur...?
 
LeftieBiker said:
Shimano made the first successful cassette freehubs, and they're still the best in the business. The farther off in the off brands you go, the more likely the freehub body is to be unreliable junk.
Click to expand...

The bike has a Shimano Acera 8 speed derailleur drive. Are you saying that the cassette isn't provided by Shimano, and that I have to find a cassette specific to the hubmotor (which, BTW, is stamped "Das Kit") and not to the derailleur...?
Click to expand...

The "cassette" is the stack of splined sprockets. That might be Shimano or not; it doesn't matter much. But the ratchet mechanism-- the "freehub body"-- on a hub motor is most assuredly not designed or manufactured by Shimano or any other reputable manufacturer. It might be discretely replaceable (with or without special tools), or you might have to replace the entire side cover to fix a busted one. You'll just have to ask the seller.

The cassette (stack of sprockets) doesn't contain any moving parts and isn't a source of noise unless it's loose or has bent sprockets.
 
I knew what the cassette is - I just didn't know that the freewheel mechanism is a separate part from it. I'll ask the manufacturer. So is the freewheel pressed into the cassette, or (I assume from what you wrote) pressed or screwed into the hub motor cover? Magnum seems to be almost a drop ship business; I should probably hope to get a whole new wheel assembly, as opposed to them just saying that they can't help me unless it breaks....
 
LeftieBiker said:
I knew what the cassette is - I just didn't know that the freewheel mechanism is a separate part from it.
Click to expand...

That's what differentiates a cassette from a freewheel, and why it matters what you call it. They do the same job, but with no parts in common.

So is the freewheel pressed into the cassette, or (I assume from what you wrote) pressed or screwed into the hub motor cover?
Click to expand...

If by freewheel, you mean ratchet clutch, customarily that's inside the splines the cassette fits onto. Here's what a normal Shimano freehub body looks like. The ratchet is inside it, along with the right side axle bearing:

51kcnLGr3aL._SX466_.jpg


But the freehub body of your hub motor isn't like that. It can't be, because there's only just enough room for a normal 10mm axle to fit through the middle of the Shimano mechanism. Whether yours is separately replaceable from the side cover is a matter of how they designed it, and I don't know that.
 
Greeeaaat. :( Thanks for the quick lesson - in why I'm probably screwed. My best bet may be to wait until it worsens, send Magnum a video of it, and hope I get a new rear wheel assembly, like what the Das Kit contains...
 
You say you've looked at the derailleur and lubricated it, so this isn't likely the problem - at one time when I noticed a lot of clunking from the rear gear, I found that the derailleur tension pulley wheel was pretty near frozen solid. I guess that led to some unusual chain tension. That has mostly gone away, though I couldn't swear it never clunks at all - I think to some degree that's just an attribute of this particular freewheel that came with the hub.
 
Tell that to them ebay sellers with words right in the title of "Shimano FREEWHEEL CASSETTE"

Chalo said:
That's what differentiates a cassette from a freewheel, and why it matters what you call it. They do the same job, but with
Click to expand...
 
donn said:
You say you've looked at the derailleur and lubricated it, so this isn't likely the problem - at one time when I noticed a lot of clunking from the rear gear, I found that the derailleur tension pulley wheel was pretty near frozen solid. I guess that led to some unusual chain tension. That has mostly gone away, though I couldn't swear it never clunks at all - I think to some degree that's just an attribute of this particular freewheel that came with the hub.
Click to expand...

The chain and derailleur were lubed when the bike was professionally assembled, I think I did one re-lube last Fall, and I just did it again. It was clean and there was no hesitation in the derailleur movement. The clunk can be replicated just by cranking the pedals forward with some force, with the bike on a work stand. When I ride (being careful to pedal smoothly) I usually get about half of my ride in or a little more (5-7 miles) before I start to hear it as I pedal. Even then it's frequent but not constant. That's why I was thinking "dry freewheel."
 
I was thinking of trying to spray some grease through a thin plastic tube into the free-whatever, from an aerosol grease can. Is white lithium grease safe enough to use with existing grease? As I understand it, it's just regular grease with zinc added for color...
 
LeftieBiker said:
I was thinking of trying to spray some grease through a thin plastic tube into the free-whatever, from an aerosol grease can. Is white lithium grease safe enough to use with existing grease? As I understand it, it's just regular grease with zinc added for color...
Click to expand...

Grease isn't the right lube for freewheels or freehubs, because it can make the ratchet pawls stick down. Light oil is fine. Keep in mind the mechanism only rotates when there isn't a load on it.
 
Chalo said:
LeftieBiker said:
I was thinking of trying to spray some grease through a thin plastic tube into the free-whatever, from an aerosol grease can. Is white lithium grease safe enough to use with existing grease? As I understand it, it's just regular grease with zinc added for color...
Click to expand...

Grease isn't the right lube for freewheels or freehubs, because it can make the ratchet pawls stick down. Light oil is fine. Keep in mind the mechanism only rotates when there isn't a load on it.
Click to expand...

I can also spray synthetic motor oil from an oiler can, but not as accurately. I was thinking light grease because of the hard metallic noise it makes, but I'll try the oil first. Thanks.
 
This week I put the bike on the workstand, awkwardly tilted the whole stand a bit sideways (they really need that axis added), and squirted quite a bit of synthetic motor oil onto the outer and inner edges of the cassette at the axle. The outer edge seemed to drink it in, but I'm not sure about the inner. I DO know that I ended up with quite a bit of oil on the rim and tire. I ran the pedal drive forwards and backwards a bit, then let the bike sit overnight. The result? While the freewheel mechanism still engages with a bit of a clank, it doesn't seem to be hanging up and making the sound repeatedly while I pedal. Fingers crossed...
 
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