Despite Shimano and SRAM refusing to make any sort of wide range 11-40t 10 speed cassette, there are a number of smaller manufacturers now offering solutions.
40t range "extender"
The "classic" way. Add a 40t cog to your existing cassette and drop one of the smaller cogs. To avoid a big gearing jump in the smaller cogs, the 15t is often replaced with a 16t.
Absolute black 28-40t
This is a mini-cluster, machined as one piece out of aluminium and incorporating 28, 32, 36 and 40t cogs.
Leonardi Factory General Lee adapter 25-40t
- Range: 25-29-34- 40t;
- Compatible with: SRAM 1030, 1050 and 1070 cassettes;
- Weight: 190g;
Praxis Works 11-40t cassette
11-40t cassette with:
- 11-13-15-17-19-21-24-28 stamped steel construction; and
- 34-40 7075-T6 machined AL with hard anodizing.
Response Free Ranger 11-40t cassette
- 11t high tensile steel;
- 13-15-18-21-24-28t one piece CrMo;
- 32-36-40t one piece 7075-T6 aluminium;
- weight: 253g.
Recon 11-40t cassette
- 11, 15, 15t steel;
- 18, 21, 24 titanium;
- 27, 32, 36, 40 aluminium;
- weight: 296g.
IRD 11-40t cassette
All steel construction and heavy (~440g).
Sunrace 11-40t cassette
Couple of versions, lighter version with alu carriers for 6 largest cogs (CSMX9) 380g and all steel version (CSMS8) at 429g. Not much info currently available. I can now confirm the Sunrace MX3 wide range 11-40t cassette weighs 386g on my digital scales. Although not the lightest option, it's certainly the best value for money - at less than $60 for the entire cassette its about the same price as an expander cog.
|XT/XTR 11-36t with 40t extender cog||387g||11||13||15||19||21||24||28||32||36||40|
|XT/XTR 11-36t with absolute black mini-cluster||286g||11||13||15||19||21||24||28||32||36||40|
|SRAM 1070 with General Lee adapter||?||11||12||14||16||18||21||25||29||34||40|
|IRD Elite 11-40t cassette||~440g||11||13||15||17||19||21||25||29||34||40|
|Praxis Works 11-40t cassette||322g||11||13||15||17||19||21||24||28||34||40|
|Response Free Ranger 11-40t cassette||253g||11||13||15||18||21||24||28||32||36||40|
|Recon 11-40t cassette||296g||11||13||15||18||21||24||27||32||36||40|
|Sunrace MX3 11-40t cassette||386g||11||13||15||18||21||24||27||32||36||40|