Wanted: 7 speed cassette - low numbers

I'm after a 7 speed shimano fitting cassette, the ideal is this:

11 - 12 - 13 - 14 - 19 - 20 - 21

So if you have anything similiar which I can modify, or some spare cassette sprockets, I'd be interested.

Don't want to spend too much, have some stuff for trade too if that's of interest.

Thanks!

I've got a new shiny chromed steel 13-23 if it's of interest (23/21/19/17/15/14/13), has removeable bolts which screw into the the 14t sprocket, you'd need to get an 11T lockring and sprocket of course.
£14 posted

Generally I'm pretty certain 7 speed road cassettes never came with an 11T sprocket back in the day, but you could rape an mtb cassette like the HG41/HG30 or somesuch and file off the ends of the supporting bolts (which have the rounded off ends) so you'll be left with 11, 13, 15, 18 & 21 and then 2 sprockets to fill in between. Obviously none of these sprockets have the screw in thread due to the slightly cheaper design comparative to the road specific ones so will be a little looser on the freewheel but not unduly so
Cheap HG41s here http://www.ebay.co.uk/itm/SHIMANO-HG30-7-SPEED-CASSETTE-BIKE-CYCLE-11-28-TEETH-/130626095808#vi-content

Hi hope you’re well,

I’ve customised several 7 speed Shimano cassettes to ride 11-21. The initial spend is about £35 but you can just keep switching out top cogs instead of buying new cassettes if you keep an eye on chain wear so you make the money back.

Sorry for the length of reply… I hope it helps.

I’ve been starting with a Tiagra HG50 7speed 12-21 cassette. Then I get a new 12t sprocket (3notch - see image), and an 11t sprocket (ideally without built in 1mm spacer) and an 11t lockring if needed.

You then

remove the spacer and 13t penultimate cog from the Tiagra HG50 cassette
insert the new 12t cog; and,
insert the new 11t cog and lockring

You now have an 11-12-14-15-17-19-21cassette.

Here are the issues / problems to avoid.

Lockring

You must use/get an 11t lockring. The old 12t lockring that came with the Tiagra CS HG50 will fit and secure your cassette but it’s too big in diameter and will stop the chain engaging with the top cog fully. It will just skip dangerously all the time.

Also you must get the type of 12t cog with the 3 notches/recesses shown in the photo. These correspond to the 3 raised points on the main cassette body from where you have removed the 1mm spacer.

Don’t be tempted to leave the existing spacer on and try to just move the 12t that comes with the Tiagra Cassette up one as it’s not notched.

If you do not buy and use this type of notched cog the indexing on your top two cogs will be off beyond tolerable limits because a lot of 11t top cogs come with built in spacers. So by the time the indexing gets down to the 11t top cog it will be 2mm out and this will cause lots of hassle setting up the rear derailleur.

The ideal is to source a top cog without a built in space. However, if it’s just the top cog with this extra 1mm then the indexing can handle it.

Money Saving

The reason I mention that the built in spacer 11t top cog is ok is because it can save you money. Some of the cheapest Shimano cassettes HG20 HG30 and other HG50 have this type of 11t top cog. The advantage is that they cost about the same price as an 11t on it’s own and you get the right size lockring for free. However, they will wear a bit quicker than the one linked below.

As you can see from my diagram of it fully assembled I’ve gone for the 11t with built in spacer this time as I’ve got NOS cassettes lying around for my GFs bike and other projects. So when I needed a new top cog I just popped this on and it runs just fine. You can also see one of the 12t notches interfacing with the main cassette body.

Shimano Tiagra Cassette 7 Speed HG50

http://www.chainreactioncycles.com/Models.aspx?ModelID=38302

**11t cog **

http://www.swinnertoncycles.co.uk/ProductInfo.aspx?productid=11F%201129-1

http://www.slanecycles.com/shimano-spares-cshg-sprocket-11t-p-6735.html

12t cog

http://www.slanecycles.com/shimano-spares-cshg-sprocket-12t-e-group-p-6736.html?language=en&currency=GBP

Remove top row replace with bottom row

cassette body - note 3 raised points

reverse of 12t - note corresponding notches

Assembled

Amazing post! thanks for your help.

My only problem is, I definitely need a 20t in there. Is the 21t separable from the block? it would be ideal to just swap that out if it's possible.

Hi Cohen, thanks, you're welcome.

The main body is held together to effectively be one piece. Those 3 raised points run through it like bolts securing the sprockets together.

Give me a couple of hours and I'll see if there's a way to get you that 20t.

Ah, that makes sense.

Well don't worry too much about it, 19 and 21 is pretty good too

thanks again

Have found that fix for you - not sure how many are available so pm'd you details, good luck!