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Old 02-04-12, 11:05 AM   #1
BikeToronto
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Shimano HG70-C Cassette replacement

The rare Shimano HG70-C 7-speed compact cassette (with 11-tooth inner) on my 20-year old 54cm Concorde 700c hybrid needs replacing. I haven't found any stock here and it seems that only a couple places in the US list it on their product list might even have it. This compact cassette requires the "Hyperglide C" freehub body and lockring. I don't need a replacement for that.

I've done a lot of research but still have these questions. I am hoping some people on here can answer each of them. Thanks.

1. This cassette was sold with the 7 speed LX Hyper-C parts groups. Is this part group still manufactured and sold?

2. The 11 tooth inner is needed for the Hyper Drive-C compact cranksets to have a full gear ratio range (so I guess I must have such a crankset on my bike as I haven't changed anything since I bought it). Therefore I have to stick with the HG70-C unless I change my crankset. But, if I do change the crankset too is it possible for me to change both the freehub body and cassette without changing the rear wheel itself (sorry if that's a stupid question)?
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Old 02-04-12, 11:19 AM   #2
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Quote:
1. This cassette was sold with the 7 speed LX Hyper-C parts groups. Is this part group still manufactured and sold?
probably not.
not familiar with that hub specifically..

Id just look for a replacement wheel & not fuss over discontinued stuff ,
another 7 speed width wheel.

prior postings say there are screw on freewheels with an 11 top cog,
a freewheel hub wheel would be cheap,
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Old 02-04-12, 11:44 AM   #3
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Here you are and only $17: http://www.loosescrews.com/index.cgi...d=689537919823

BTW, buy and install a new chain when you get the cassette. Also, 7-speed groups have been obsolete for years and only a few components are readily available.
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Old 02-04-12, 12:01 PM   #4
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fietsbob: Thanks, but I don't want to replace the wheel and freehub if I don't have to. I actually just found the cassette online at two different places and confirmed that one of them does have it in stock brand new for $30.

Hillrider: The $17 Shimano HG41 cassette you pointed out indeed does have an 11-tooth inner/top cog and is 7-speed just like my HG70-C cassette, but the listing says it is compatible with the Shimano Hyperglide, not the Hyperglide-C version which is the compact version of the hub and is the one I have. Correct me if I am wrong but I don't think it would work and so I should get the exact same HG70-C cassette.

Thanks for reminding me about the chain. I will get a new one. The crankset I have has the label Shimano biopace-SG and 'for NARROW chain only' on it so I'll have to get a narrow chain (whatever that means).

Last edited by BikeToronto; 02-04-12 at 12:23 PM.
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Old 02-04-12, 01:29 PM   #5
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You've got it backwards-

The "C" or Compact Free Hub is required to use an 11T cog.
It will accept larger top cogs no problem.

"Standard" bodies won't accept an 11T cog.

The 11T cog doesn't have the splines running all the way through, so it won't fit all the way on to a "standard" body.
The C type bodies have the outer end beveled, so the 11T can fit all the way on..
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Old 02-04-12, 01:30 PM   #6
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Originally Posted by BikeToronto View Post
Hillrider: The $17 Shimano HG41 cassette you pointed out indeed does have an 11-tooth inner/top cog and is 7-speed just like my HG70-C cassette, but the listing says it is compatible with the Shimano Hyperglide, not the Hyperglide-C version which is the compact version of the hub and is the one I have. Correct me if I am wrong but I don't think it would work and so I should get the exact same HG70-C cassette.

Thanks for reminding me about the chain. I will get a new one. The crankset I have has the label Shimano biopace-SG and 'for NARROW chain only' on it so I'll have to get a narrow chain (whatever that means).
Hyperglide-C was the freehub body with the ends of the splines shortened to accept an 11T small cog. The regular Hyperglide body (no C) had full length splines and would not accept an 11T, a 12T was the smallest that would fit. If you had an 11T small cog on your current freehub, the casette I referenced will also fit.

The "narrow" chain reference was the standard 7-speed chain and was narrower than the former 5-speed and standard space 6-speed chains. These days will be listed as either 8-speed or 6/7/8-speed. They will all work.
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Old 02-04-12, 03:23 PM   #7
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Originally Posted by Bill Kapaun View Post
You've got it backwards-

The "C" or Compact Free Hub is required to use an 11T cog.
It will accept larger top cogs no problem.

"Standard" bodies won't accept an 11T cog.

The 11T cog doesn't have the splines running all the way through, so it won't fit all the way on to a "standard" body.
The C type bodies have the outer end beveled, so the 11T can fit all the way on..
So since that ad at http://www.loosescrews.com/index.cgi...d=689537919823 says that the HG41 7 speed Cassette listed 'Fits all Shimano 7 speed hyperglide cassette hubs' does that mean all Shimano 7 speed hyperglide cassette hubs are compact ones, ie Hyperglide-C hubs? Because, as you say, standard bodies, ie Hyperglide (no C) hubs won't accept an 11T cog.

I found it even cheaper at Amazon at $12.45: http://www.amazon.com/Shimano-HG41-S.../dp/B005QSFE5W

Last edited by BikeToronto; 02-04-12 at 03:27 PM.
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Old 02-04-12, 05:20 PM   #8
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I actually don't know if all 7 speed bodies are "C".

This link shows their only 7 speed body and it is compatible- maybe just to keep inventory down for a slow moving item or???
http://sheldonbrown.com/harris/k7.html#bodies

http://sheldonbrown.com/k7.html#hyperdrivec

All that said, IF you seldom use the 11T cog, you can use a cassette with a 12 or 13T top cog.
That was the point I was trying to get across, that an 11T cog WASN'T "required"-
In answer to your statement -

"2. The 11 tooth inner is needed for the Hyper Drive-C compact cranksets to have a full gear ratio range (so I guess I must have such a crankset on my bike as I haven't changed anything since I bought it). Therefore I have to stick with the HG70-C unless I change my crankset....."
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Old 02-04-12, 06:31 PM   #9
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Ok, now I get it. Thanks. I do use the 11T cog a lot so I'd like to stick with it.

I'm going to order the HG41 cassette. I did a bit more research and from Sheldon Brown's Bicycle Glossary at http://sheldonbrown.com/gloss_ho-z.html#hyperdrivec for 'Hyperdrive-C' it indeed says that 'Specifically, this refers to cassettes which feature an 11 tooth sprocket, and the bodies designed to accommodate them.' so I guess indeed all 11T sprockets are designed only to fit on Hyperdrive-C compact cassettes and this is why the HG41 cassette will be compatible. Also, I am sure HillRider knows what he is talking about.

Thanks to you both. I'm a bit more educated about all this now!
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Old 02-04-12, 07:44 PM   #10
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Yes, now you've got it. ANY seven speed Shimano/SRAM Hyperglide cassette will work on your wheel regardless of # of teeth. Definitely replace the chain too. Any 6/7/8 speed chain will work fine.

Quote:
Originally Posted by Bill Kapaun View Post
I actually don't know if all 7 speed bodies are "C".
Not all 7 speed bodies are compact. I've had non-compact 7 speed bodies and also Hyperglide/Uniglide compatible bodies with the threading for the last cog. I even have an 8 speed (Ultegra) Freehub body with the Uniglide threading.
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Old 02-07-12, 10:37 AM   #11
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Thanks for everyone's help. When I finally worked out the price to get it shipped from the US (even the least expensive one) and added the Canadian HST, shipping, duty and brokerage (unfortunately we have to pay a minimum flat rate for a shipment regardless of the cost) I decided to check a few retailers in Toronto. I found one for $44, which was only a few dollars above the landed cost to me in Toronto for a US supplied one. Also I could have it instantly. The retailer had about 30 of them and only sells a couple a year.
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Old 02-07-12, 06:13 PM   #12
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$44 for a 7 speed cassette? I get these on ebay for less than $20.
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