Working limits of a DX short cage mech - advice sought

[paddy311]

Can anyone offer a bit of advice on this ?

I have a short cage DX m650 rear mech I am planning on using. It is stamped up with 28t max........ but the cassette I want to use has a 30t low gear

Will it work or am I just setting myself up for a right pain in the arse that won't work properly ?

 

[drystonepaul]

I run a 13-30 cassette with a 26-38 double chainset set up with a short cage DX rear mech on my 1993 Univega.
No issues as long as the chain is the correct length.

 

[paddy311]

Thanks Paul.

Sorry - I should have made it clear about both ends of the gears. I've got a 13-30 cassette and 26/36/46 rings. So (30-13)+(46-26)=37.

I guess my question is - can I run this safely on the rear mech as long as I don't shift into gears with a ridiculous chainline ? Or, in the real world am I best just getting a long cage mech so I don't have to think about it while I'm riding ?

 

[drcarlos]

Thanks Paul.

Sorry - I should have made it clear about both ends of the gears. I've got a 13-30 cassette and 26/36/46 rings. So (30-13)+(46-26)=37.

I guess my question is - can I run this safely on the rear mech as long as I don't shift into gears with a ridiculous chainline ? Or, in the real world am I best just getting a long cage mech so I don't have to think about it while I'm riding ?

I run a 11-28 Cassette and a 24/36/36 chainset with a short cage XT M735 mech, my setup will not do the big crossover (you should never do this anyway) but will work fine up the second sprocket (not that i'd advise it), I would imagine you would be in a similar situation as the mech can't wrap enough chain to do all the gears.

Carl.

 

[bodrobert]

Hello,

I've used 24-36-46 in combination with a 13-30 cassette and a short cage XT derailleur (RD-M735), and it worked well. Just make sure that the chain length is correct.

 

[paddy311]

Thanks guys - I'll give it a go.

 

[Raging_Bulls]

A cassette with a 30 tooth big cog might be a problem.

I recall that my M735's manual mentioned that it could only be used with a 28 tooth safely, or with a 32 tooth if the hanger was a certain distance from the wheel axle.
The M650 is from the same era and DX was one step below XT back then, so I assume it might be the same story there.

Give it some dry runs in your workstand, carefully checking for clearance if you go near the cassette's big cog. If it doesn't work out, just spend a tenner on a modern 12-28 cassette. The 7-speed ones (Alivio HG50 and the like) are pretty much the same as the good cassettes were back then.

 

[WD Pro]

I ran 12-28, 735 short cage rear, with standard XT crank ratios (whatever they were - now gone so I can't check). Set the chain length to be safe on big / big and had no problems. The chain was slack when on small / small but at least it was 'safe' and you would never have any problems with panic miss shifts etc.

Mums orange is set up the same but with a specialised crank. If you are interested you can count the teeth or if you want, I will check next time I am down :



WD

 

[paddy311]

I've just bought two cheapy hg41 11-28 cassettes on ebay to give me an option. I need one for another build anyway. Will give it a crack and see how I get on Cheers everyone.

 

[Unclejack]

7 speed 11 - 34 to 24/ 38 no issues for a dx short cage retro fitted to a same period lx mech upper.