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Customising a cassette

by theSplund
Tue, Jun 14, 2016 13:24
6

Hi.
The 'scenario': I'm currently riding a Thorn Audax with 46-36-26 and a 12-27 9spd Ultegra block but would like a bit more 'bottom end' when I do the LEJoG (with panniers incl. tent/bag etc) and I'm tempted by either the 11-32 or 11-34 XT M770 9spd blocks but don't really need that '11'.
The question: I was wondering if it is as dead simple as it appears to drop the 11 from the 11-32 and replace it with either a 13 between the 12 and 14, or a 15 between the 14/16, or go for a 11-34 and drop the 11 in favour of a 12. I believe the spider holds the six largest on the M770s.

Here's the teeth (hopefully the formatting isn't lost when I post)
11 12 14 16 18 21 24 28 32 (drop 11, repalce with 13 or 15)
11 13 15 17 20 23 26 30 34 (drop 11, repalce with 12)

I am favouring the 11-32 as I may replace my chainset soon too and go with a 46-36-24 (ie the limit of the 105 FD) and can revert back to the 12-27 or maybe something closer next time. I'm aware of the Harris custom cassettes but they're a lot more expensive as both M770s can be had for less than £40 and individual cogs seem to be £3-£6 each.

And if anyone needs to ask, the rear mech is a long cage Deore LX (RD-M563) and the front is a 105 triple (FD5504) both currently working quite happily with my Ultegra STi levers.
And sorry for the mention of 'Deore' and 'XT' in a road forum!

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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6 comments

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theSplund | 8 years ago
1 like

Thanks all.
The points about not dropping the 11 and going for a 24 on the front are quite valid. Good info (incl link) in your post boRed.
I've just checked and I hadn't realised Wiggle were doing it so low - good shout.
I've checked the purchase date of my existing cassette and have now realised it's got a few thousand miles on it so a new cassette is definitely on the cards (prob the 11-32) but I think I really need to consider new rings too and maybe go for a 24 when I do.

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RR | 8 years ago
1 like

Both the 11-32 & 11-34 XT cassettes are available from Wiggle and CRC for £32.49 at the moment.

The 11-32 XT has the 5 largest fixed on the carrier, and the 11-34 has the 6 largest fixed (I have had both).

The custom options mentioned will work but the shifting may not be quite as smooth, especially if you insert a new cog in-between two designed to work next to each other.  It can be better to split and combine two cassettes so there is only one shift affected, e.g. 3 smallest from one cassette and six from the other.

11T cogs use a smaller lockring than the 12T and above.  Either re-use the lock ring from your existing Ultegra cassette or you can buy it separately.  All the 12T cogs have the ridges for the lockring to grip.

HG50 cassettes are very good for the smaller cogs: One starting with a 12T will have all the small cogs you are interested in as well as the lock ring and spacers, and at the moment only costs £12/£13 from Wiggle/CRC.  SJS Cycles are very good if you are looking for individual parts.

HG80 and HG50 cassettes are cheaper than XT for just a bit of extra weight and maybe worth considering instead, especially if you take the cassette off after LEJoG.  HG80 has the 3 largest on a carrier, and the next 3 or 4 in a block.  As mentioned above, the HG50 also comes in an 11-30 which still has a pretty low gear but avoids the worst of the big jumps.

For diagrams of the cassettes go to: http://si.shimano.com/#.  Search for the code of the cassette and look at the exploded view diagrams.

Also, it's probably obvious but remember to make sure your chain is long enough!

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rjfrussell | 8 years ago
0 likes

you may just like making it just hte way you like it, but is this really necessary?  once you have your desired low-gear (be it the 32 or 34) in play, does the interval at the top end really make much difference.  And, even if you are taking it slowly, might you not want a top gear of 46x11?

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theSplund | 8 years ago
0 likes

Thanks Woldsman & CXR94Di2 - useful feedback and a good link too. I will consider veering towards a larger small tooth, ie a 13, based on your combined feedback - for the LEJoG I won't be looking to go that fast (and getting up hills will be more important). I'll pay attention to the locking ring too.

FYI re the 11-34 - there's a seller on ebay called ' allterraincyclesltd' selling both 11-32 and the 11-34 for £40, but the 11-32 can be had for £35 from 'highonbikes'

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CXR94Di2 | 8 years ago
0 likes

I have done this a few times. I used cs6800 cassettes. I used a 11-32 and a 12-28 cassettes created 14-32. Worked perfectly. I have also fitted a 11-40 with a custom derailleur hanger to my setup. Again useful for very hilly rides

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Woldsman | 8 years ago
0 likes

Not quite that straightforward, but not difficult either. 

Your smallest sprocket needs to accept the lock ring (and the adjacent one might need to have an integral spacer).  I prefer a 13-34 9spd custom cassette, but the method for 12-34 is much the same as described here:

http://cycleseven.org/customising-shimano-hg50-tiagra-deore-cassette

I've had a very quick Google and can't immediately see a 9spd cassette with a 34T largest sprocket available online.  32s are easy to come by. The 8spd cassettes have the same width sprockets, I believe, so if you got one with the correctly sized larger sprockets you could make your custom cassette using one of those and the smaller sprockets from a 9spd cassette.  You just need the correct spacers from a 9spd cassette if you don't go with a donor spidered M770.   

Hope this helps.

 

 

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