mtb rear mech compatibility

[tufty]

So, I've been mainly forgoing the pleasures of road riding recently due to the inevitable advance of the years - my MTB with a lowest gearing of 22-32 is somewhat easier to ride around here* than my road bike with 42-24. Unsurprisingly enough

I'm currently set up with a "classic" 52/42 double up front, and 8 speed 14-24 cassette, 105 mechs and RX100 brifters. Ideally, I'd go compact triple and 9 speed, but that means a lot of €€€ I can't afford. Can't see any way to mod the LHS brifter to triple, which suggests my only other option is extending the range of the cassette to get some lower gearing.

AIUI, I can't throw a 9 speed cassette on an 8 speed freehub (and doing so would mean changing the RHS brifter to a 9-speed unit anyway, too much €€€), but I should be able to chuck an 8-speed cassette with lower gears on as long as I change the rear mech** to a long cage "mountain bike" unit, right? As a bonus, I figure that's gonna give me enough headroom to swap out the small ring for a 39T as well.

So, suggestions on a mech?

Cheers

Simon


* French Alps. My ride to work is 850m vertical over 12 km. Going to the local bar is 150m over 1km. I'm 47. You get the idea.
** Yeah, I know it's possible to run derailleurs "out of spec" if you're uber-cheap, as long as you're willing to avoid certain gear combinations, but it's the kind of thing you only need to get wrong once. Been there, done that, picked the gravel out of my knees.

 

[mattr]

8-9-10 freehubs are identical IIRC. Should be able to drop a 9 speed cassette straight on there.
But. Easier option is to get an 8 speed mtb cassette 13/32 or something and any 8 or 9 speed long cage mtb mech, that'll all work together. Something like an slx won't be too spendy. Deore is even cheaper.
And stick a 38 on the front for some extra climbing inches!

And you can mod a double shifter to do triple, but I've no idea where to buy the little widget that does the job.

 

[legrandefromage]

If you are really bored, you can take the long cage off an MTB mech and create your own 'long cage' road mech. Older generation road 105/ 600/ 500EXwith MTB DX/XT/LX/ Mountain LX mechs are good for this.

You can also run a longer chain with a chainstay chain tensioner (I used a Ging) and still use a short mech with a large-ish cassette and 52/39 up front

 

[legrandefromage]

Re:

Heres my M730 XT MTB mech with the cage off a 600

 

[tufty]

If you are really bored, you can take the long cage off an MTB mech and create your own 'long cage' road mech. Older generation road 105/ 600/ 500EXwith MTB DX/XT/LX/ Mountain LX mechs are good for this.

Would there be any advantage to doing this over just using a long cage mech beyond "it looks more stock"?

You can also run a longer chain with a chainstay chain tensioner (I used a Ging) and still use a short mech with a large-ish cassette and 52/39 up front

Oooh, never thought of that.

And you can mod a double shifter to do triple, but I've no idea where to buy the little widget that does the job.

Got any links on that? My google-fu seems to be coming up short.

 

[legrandefromage]

just different.

 

[Vino]

My ride to work is 850m vertical over 12 km.

Ouch. It's hilly around here, and I usually do that much climbing over 40 km or more.

Your proposed bottom gear of 39x32 is the same ratio as 34x28... how about a compact chainset?

 

[tufty]

Funny you should say that. I think there may well be a compact chainset in my future.

 

[dirttorpedo]

What's the vintage of your bike? Early mountain bike long cage derailleurs were effectively road bike touring derailleurs pressed into double duty. You could use an early Shimano Deerhead or a somewhat later Deore DX derailleur and it should work fine. Another option is to swap to a 110 bcd crankset from the early 80's - you could get a Sugino VT double and swap on some compact or sub-compact rings and you'd have a great set of climbing gears.

Another option is to just put on a long cage version of a vintage road mech - I've just bought a Shimano 600 long cage for my wife's bike and I know that they made long cage suntour Cyclone and VX derailleurs BITD. Those older road mech's are probably a bit more expensive than a mountain bike version though and the mountain bike one will probably let you go up to 34 teeth in the back so if you don't care what it looks like that might be a good bet. My friend is running a Shimano XT rear mech with her 9 speed ultegra touring bike and it works fine.

 

[tufty]

The bike I'm thinking about modifying is a '90s Bertin "Course" with a Vitus 999 lugged steel frame. Nothing to write home about, but the frame fits me. I'm currently thinking compact double up front as a first step, keeping an option on an MTB derailleur and cassette in the rear if necessary.

It's probably time to split out the vintage road stuff to pay for it...