BC6260

Hello bike experts: I am trying to replace the cassette for my Trek 3700. My existing cassette is a Shimano MF-HG37 13-28t, which I can't find new anywhere. I bought a Shimano CS-HG200-7 12-28t but it won't fit on the existing HG37 hub body. The HG37 uses a variable diameter hub body with wave-shaped spines whereas the HG200-7 requires a uniform diameter hub body with rectangular spines.

What hub body does the HG200 require? Are the threads compatible with the HG37? Any other suggestions on how to restore my bike?

Thanks,
Bob

noobinsf 

Hmm, the part number MF-HG37 matches up to a freewheel. Is that what you have? Here is a reference: https://www.sheldonbrown.com/free-k7.html

...and a pic from the reference below. If you really need a freewheel, then you can search eBay for "shimano tourney freehwheel 13-28" and you should get some relevant results.

noobinsf 

If it turns out you need a freewheel, Sunrace also makes a nice 13-28, which I am using on one of my bikes.

BC6260

Thanks for the reply. I studied that tutorial before buying or posting and, as I understand it, mine is a cassette. After removing the lock-ring, the rear cogs can be removed individually, leaving just the variable-diameter hub body. Unfortunately, as a newbie, I am not allowed to post my photos nor links...

noobinsf 

Were there a million loose ball bearings when you disassembled? I have the nagging feeling that you disassembled the freewheel rather than remove the whole unit.

Did the process you followed look something like this: https://restoringvintagebicycles.com...ewheel-part-i/

And did the part left on the hub look like this?

BC6260

Thanks for your help. No, there were no ball bearings, just a lock-ring, cogs, spacers, and a hub with spines.

noobinsf 

Sorry, I'm of no further use without pictures. As far as I know, there was no one-off Shimano standard beside freewheel and freehub. There was Uniglide before Hyperglide, but Uniglide was very similar to Hyperglide, and in the part number you gave, HG refers to Hyperglide.

On the upside, this back and forth is helping you get your post count up. Once you get to 10 (limited to 5 per day for new members), you can then post pics!

BC6260

Yep, getting that post count up!

Just revisited the official shimano page for the MF-HG37 and they refer to it as a "Multiple Freewheel" (hence, one presumes, the "MF" in the part number). But otherwise it seems to fit the description of a freehub cassette per Sheldon Brown's excellent reference.

noobinsf 

"Multiple" refers to the freewheel having more than one cog (vs. a single-speed freewheel, which would have a single cog). If the image on the Shimano page matches what you have, then I have a hard time envisioning what else could have happened besides your taking apart the freewheel. I'll have to wait for pics...

BC6260

Thanks. I am more and more convinced that you gave me the right answer with your first reply, but I had worked hard to convince myself that mine was a cassette/freehub system, so it's taking some effort to unconvince me. Clearly it's pretty out-dated...

BC6260

After revisting Sheldon Brown's tutorial, I have definitively determined via the "spin test" that the MF-HG37 is indeed a freewheel. The removable sprockets on the splined body had me believing otherwise, but it looks a lot like the Shimano Hyperglide Freewheel photo from the tutorial. The lock ring I removed is the one the photo caption says "it is never necessary to remove".

So, the Shimano MF-TZ21 14-28t looks to me like a good replacement, as does the Sunrace 13-28t you mentioned.

Thanks again for your help. If you're interested in seeing the photos of my disassembled freewheel, I'd be happy to keep chatting until I reach 10 posts.

noobinsf 

I’m actually curious to see the internals since you said that there were no bearings visible when you disassembled. In any case, I’m glad to know the mystery is solved. Good luck with the renovation!

BC6260

I notice that your username implies SF but your profile mentions Oakland. Are you an NFL fan?

noobinsf 

Neither team stuck with its city. They are dead to me. I'm not so much into sports for sports' sake, more for civic pride. I do love an A's game or a Giants' game on a sunny day.

BC6260

My wife and I followed the Panthers out to see them get massacred by the 49ers at Levi's in Oct. Disdain for the stadium and location seemed almost universal among the fans, but I enjoyed visiting my old SJ stomping grounds from my years in the integrated circuit biz. Saw the Giants play at candlestick in '74...

BC6260

Ended up buying the Shimano MF-TZ500-7 14-28t with which I am perfectly happy despite the 1 tooth difference on the small cog.

BC6260

My local bike shop had the part in stock. They removed the old freewheel and installed the new one at no additional charge. By saving me the cost of the removal tool, it was actually cheaper than Amazon.

BC6260

Here are my photos from my disassembled old freewheel, the MF-HG37.


28 tooth cog from MF-HG37


"hub body" from MF-HG37, showing "wave-shaped" splines and variable diameter