Fitting a Shimano HG70 11T-28T (7) cassette to a Shimano DX FH-M650 HUB (7)

[drexal77]

Hi guys,

Will try to keep to the point below as i tend to go into way to much detail and people get bored reading through.

Recently managed to buy a beautiful condition Shimano HG70 11T-28T 7 speed cassette (with red label still attached). Its for a mountain bike build i'm doing (i know it should be a 12T-28T).

Long story i wanted the 11T cog as i do a lot of flat and down hill roads and love standing up sprinting those sections as fast as i can for short burst ( i've been lectured about spinning etc and that i should stick with 12T cog etc but i really want to make this 11T work). I bought it in hurry with out researching it properly.

Now i have run into a load of issues. I want to pair it with the period correct Shimano DX FH-M650 7 speed HUB (that i haven't bought yet) but from my research (a lot of help from sheldon brown https://www.sheldonbrown.com/k7.html) he says the only way to get the 11T cog to fit to this HUB is if i buy one that is Hyperglide C version (which i'm not sure Shimano ever made this hub with a hyperglide C body) or i switch the body for a hyperglide C body. Its to do the splines being shaved off the edge of the C body which allows you to use the very small 11T cog. I've scoured the internet for hyperglide C hubs / free bodies but all it comes up is the hyperglide C cassettes. There are shimano bodies for sale that look similar to the Hyperglide C body with the splines shaved back from the edge, but they are all seem to be for 8/9/10 speed set-ups. I've searched the Shimano old parts technical drawing website, but nothing comes under hyper glide C (i think the C stands for compact, so i'm not sure if the body is shorter compared to the normal hyperglide body that comes with these hubs)?

Does any one of you own a Hyperglide C hub / body and would you happen to know the size of it? so at least i could measure it against one of these 8 speed bodies to see if they are the same size at least.

I've attached an image of the hyperglide C body and the normal hyperglide body.

If any of you can recommend a free body that would fit that i can add to the DX hub, that would be amazing.

The second issue is, i want the run the cassette & hub with the period correct RD-M650 rear derailleur, but i have just managed to find a service instruction for this derailleur and it says max cog 28T-32T & smallest cog 12T so it looks like this 11T-28T won't work with the derailleur i want to run also. Have any of you ever run a 11T cog on this exact RD-M650 rear derailleur?

Also i know sheldon says this:

• Alternately, you can grind a bevel on the ends of the splines of an older body. This is a five-minute job if you have access to a bench grinder. Clean up carefully afterward so particles of metal and grinding-wheel grit don't wear out the bearings.

Note, if you install an 11-tooth sprocket on an existing cassette that had a larger top gear, you must also replace the Hyperglide lockring with a Hyperglide-C lockring. The lockrings made to work with 11-tooth sprockets have a smaller outside diameter. If you use a larger lockring, the side plates of the chain will hit the edge of the lockring, and the chain will not run properly on the 11-tooth sprocket. (Hyperglide-C lockrings are compatible with 12-tooth sprockets though not always with larger ones.)

But i didn't really want to buy a vintage body and then try and file the edges down. So would rather try and get a hyperglide C body. Also the chain i bought is the CN-HG71 so need to check that won't have issues with an 11T as well.

I really hope it's possible to make this work.

Thank you so much for anyone that can offer any advice here.

 

[hamster]

I know the problem and can sympathise - I have done the same conversion. The easiest way is to get an STX hub and swap the body. Shimano kept the basic design the same but they did fiddle around with the seal / dustcover detail (different diameters etc), so sometimes you may need to prise the DX one out and swap it. It's easier to swap the cone/seal etc from the STX at the same time.

I've got a couple of decent STX rears kicking around in the toolbox, happy to sell the freehub body and matching RHS cone / seal for £10 posted.

 

[synchronicity]

Why wouldn't the RD-M650 rear derailleur work with an 11T cog?
Again, CN-HG71 chain will worth with 11T cog, why wouldn't it?

There are shimano bodies for sale that look similar to the Hyperglide C body with the splines shaved back from the edge, but they are all seem to be for 8/9/10 speed set-ups

Get that one. If it works with 8/9/10 speed, it can be made to work with 7 speed (with a spacer, see below). But not the reverse.

Of course, my memory is a bit poor now about the difference between 7 and 8 speed freehubs:

The width of early Shimano six- and seven-speed cassettes was 36 mm, and early eight-speed 40 mm wide. Shimano then changed again and standardised eight-eleven speed cassettes on 41.5 mm and second generation seven-speed to 38 mm. The widening of the sprocket carrier on the cassette hubs to 41.5 mm resulted in a decrease in the distance between the hub flanges.

For Shimano and SRAM the cassette spacing developed as follows. Early Shimano seven-speed cassettes are 36 mm wide, with sprocket spacing of 3.65 mm, but levers and rear derailleurs are not compatible with later Shimano seven-speed cassettes, which are 38 mm wide and have 3.2 mm sprocket spacing. An eight-speed cassette is wider at 41.5 mm than a second generation Shimano seven. This results in functionally compatible shifters, but specific freehub bodies, or necessitating the use of a spacer with a seven-speed cassette on an eight-speed hub.
https://en.wikipedia.org/wiki/Cogset

The reason you can't find a hyperglide C freehub is because no one calls it that anymore.
Anything 8/9/10/11 speed is already automatically hyperglide C compatible. You already deduced this yourself I see, looking at the splines.

I think you are reading these shimano compatibilities too literally. Sometimes things can be made to work.

 

[drexal77]

I know the problem and can sympathise - I have done the same conversion. The easiest way is to get an STX hub and swap the body. Shimano kept the basic design the same but they did fiddle around with the seal / dustcover detail (different diameters etc), so sometimes you may need to prise the DX one out and swap it. It's easier to swap the cone/seal etc from the STX at the same time.

I've got a couple of decent STX rears kicking around in the toolbox, happy to sell the freehub body and matching RHS cone / seal for £10 posted.

Hello, thanks so much for fast reply. I new you guys would be able to solve this in seconds, when i've spent hours reading up. And thanks for generous offer on the body and cone etc. I would like to take you up on that. But could i first just check about the RD-M650 rear derailleur with the 11T cog. Have you ever used these to in combination. I really want this bike to have as many parts on it, that it originally came with. And i love the look of the RD-M650's?

 

[drexal77]

Why wouldn't the RD-M650 rear derailleur work with an 11T cog?
Again, CN-HG71 chain will worth with 11T cog, why wouldn't it?

Get that one. If it works with 8/9/10 speed, it can be made to work with 7 speed (with a spacer, see below). But not the reverse.

Of course, my memory is a bit poor now about the difference between 7 and 8 speed freehubs:


The reason you can't find a hyperglide C freehub is because no one calls it that anymore.
Anything 8/9/10/11 speed is already automatically hyperglide C compatible. You already deduced this yourself I see, looking at the splines.

I think you are reading these shimano compatibilities too literally. Sometimes things can be made to work.

Hello, thanks so much for replying, my bike building skills are none existent i'm afraid. But would love to do this has a hobby into my later life. Thanks for helping to clarify the Shimano hyperglide C body questions. Its all making sense now. Regarding the rear derailleur i read that information on another forum and i the guy uploaded the shimano service instructions and it states that 12T is the lowest you can use. As i'm so new to this. It took me a couple of days to get my front and rear derailleur set correctly (on my daily bike) and that was with the correct cassette and chain rings, so i was worried i would be at it for days again and it might not work as the rear derailleur might let you change down into that cog etc (please don't roast me on lack of knowledge) so just wanted to make sure i had all the right parts before i started.

 

[synchronicity]

I reckon it'll work (honestly, they're not that different). Shifting might be a tad slower into the 11T cog as a result.
Half the time shimano just says this to cover themselves. They have to put some written limits somewhere.

Don't believe everything they say. Try it! Make it work!
The key word they always use is 'optimum'.

 

[synchronicity]

The Shimano RD-M650 has a b-tension adjust screw. You use that to set the height/distance of the pulley wheel under the cassette...

 

[synchronicity]

I'm not sure but I have a hunch that your said derailleur predates 11T cogs.
If so, Shimano isn't/wasn't going to change all their instructions sheets to state that it works after releasing it.

Others will know better than me as I was really just starting out back in the early 90's.

 

[FluffyChicken]

The DX rear mech is classed as not compatible with 11T because it came before 11T and when 11T was released at that level, DX was phased out.

It works, just like M900 mechs work with 11T and they never had an 11T cassette to go with them.

If you hub is 7 speed and you want to put a 7 speed cassette on it, that is fine. As you want to fit a compact 11T one on you'll need a thin spacer at the back to allow the cassette to be clamped up correctly. If you have the old cassette, you take it apart (a few long bolts or crack the rivet out) and pinch the funny shaped thin one.

That usually does it.

 

[hamster]

No problem with older derailleurs and 11T. That's what the B-tension screw is for, adjusting the drop between cassette and top jockey.
Essentially Shimano didn't change the geometry of the design between 1988 and 2005 or so.

As an aside, Shimano have huge margins for error built into their compatibility. If they say it will work, it's pretty much guaranteed. However you can usually stretch things a fair bit. I bet the reason they put 12T min was because 11T didn't yet exist and at that time 13 or 14T was the norm for top gears from the time of freewheels. Freehubs were still a pretty new idea in 1989.