Upgrade to rear mech on 1992 Raleigh Dynatech

[Laowai_1]

I have just completed a refurb on my 1992 Raleigh Dynatech Encounter. I have the impression that the mechs really are end of life but I guess I won't be able to get a replacement 7 speed rear mech, will I? I assume that 8 speed is still available, but would an 8-speed cassette fit on the hub body? The hub is Exage on Mavic X618 NOS rim. See attached photos. It looks to me that there is a gap of about 4 to 6 mm between the largest sprocket and the ends of the spokes, which should be enough for another sprocket - yes? The gap between the dropouts is 130 mm.

If I can't fit an 8-speed cassette, and associated mech, what other options are there to renew/upgrade the rear?

[NetworkMan]

Just because you have a 7 speed system you don't have to have a 7 speed rear mech. You can happily use an 8 speed one (or even a 9 or probably a 10 speed one if you want). You just need to consider the capacity and sprocket sizes. What chainrings and cassette do you have? that will enable us to suggest a replacement.

You may find something like an 8 speed Acera will suit which is what I have on my 8 speed tourer.

Your Raleigh is contemporary with my Dawes Horizon which also had a 7 speed Exage hub. An 8 speed cassette will not fit, but you don't need to change to 8 speed as explained above.

[Brucey]

you can normally use an 8s cassette with one sprocket removed in place of a 7s one.

You can use any shimano mech that is 6s,7s,8s (but not RD-7400 series) any 9s mech, and any 'road' 10s mech (but not RD-4700), capacity allowing.

cheers

[tim_f]

May be a Shimano Claris RD-R2000 8 Speed Rear Derailleur - Silver - SS / Short Cage or SG /Long cage would be a good match. As the other posters have said it will work fine with a 7 speed chain and cassette - and will work with your shift leavers the same as a 7 speed one.

[Laowai_1]

Just because you have a 7 speed system you don't have to have a 7 speed rear mech. You can happily use an 8 speed one (or even a 9 or probably a 10 speed one if you want). You just need to consider the capacity and sprocket sizes. What chainrings and cassette do you have? that will enable us to suggest a replacement.

You may find something like an 8 speed Acera will suit which is what I have on my 8 speed tourer.

Your Raleigh is contemporary with my Dawes Horizon which also had a 7 speed Exage hub. An 8 speed cassette will not fit, but you don't need to change to 8 speed as explained above.

I find this most informative; thanks. I guess I don't need the 8 speeds per se - not with a triple at the front; I just need to find a newer rear mech. But I really don't understand how the indexing will work if I use a derailleur with (in this case) more 'steps' than there are sprockets on the cassette; surely the mechanism will not move far enough between depressions of the 'up' and 'down' shifters? But if I can use a modern 8-speed Acera rear mech that would be good enough.

The chainrings are Biopace 48/38/28 (original, but not so worn as to require replacement); the cassette I have is also the original 12/25 one, again not seriously worn (your comments based on the photos would be appreciated). The rear mech is Deore LX M550, medium cage I assume. So, could I replace this with an Acera M360 (8s) or even an M390 (9s) ?

Furthermore, if possible, I want to retain the shifters/brake levers, which are Deore-XT; they feel better than the original Deore LX ones. I have completely disassembled and cleaned them. The front mech (M550) is in pristine condition but suffers from being quite worn at the cable clamp and seems to me to have a return spring that is so strong as to put a lot of strain on the shifter. It sounds like a gun firing when I shift to a smaller ring! Could I replace this with Acera too? How would the quality of a 2008/2009 Acera compare with an early 19902 Deore DX/LX component?

[Brucey]

…. Could I replace this with Acera too? How would the quality of a 2008/2009 Acera compare with an early 19902 Deore DX/LX component?

Not even close. Deore DX and LX were near the top of the shimano heirarchy and acera is near the bottom. Anything new is likely to be better than anything worn out, but acera is a fair step down. I'd suggest deore LX or XT parts if you want them to work well and to last well.

cheers

[Laowai_1]

you can normally use an 8s cassette with one sprocket removed in place of a 7s one.

You can use any shimano mech that is 6s,7s,8s (but not RD-7400 series) any 9s mech, and any 'road' 10s mech (but not RD-4700), capacity allowing.

cheers

Thanks for this advice. I am guilty of not explaining my aims clearly: I do not necessarily need to replace the cassette as I don't think it is so worn as to require this.

The rear mech (Deore LX M550) might need replacement though: firstly it doesn't line up well with the rest of the drive train. By this I mean that the plane of the cage/pulleys is not parallel to the plane of the upper and lower chain length between the cassette and the chainring. The hanger on the frame is not bent; the problem seems to be where the cage is fixed to the rest of the rear mech. In addition, I had the Hi and Lo limit screws drilled out (the Philips heads had worn away) and replaced with much harder Allen headed bolts. But even so the Lo limit screw seems to have no effect, so there is something wrong there.

I am not aware of the RD-4700 mech; it is not listed in the reference article on Shimano groupsets I have been using ( https://en.wikipedia.org/wiki/Shimano). What is it?

[Laowai_1]

Not even close. Deore DX and LX were near the top of the shimano heirarchy and acera is near the bottom. ..I'd suggest deore LX or XT parts if you want them to work well and to last well.

cheers

Just as I feared; yep, 'work well and last well' is what I have come to expect on this bike - but can I really use a 9s or 10s rear mech from say an M770 or M660/T660 ort M590 groupset as a sort 'plug replacement' for my M550? What about the shifters?

[Laowai_1]

May be a Shimano Claris RD-R2000 8 Speed Rear Derailleur - Silver - SS / Short Cage or SG /Long cage would be a good match. As the other posters have said it will work fine with a 7 speed chain and cassette - and will work with your shift leavers the same as a 7 speed one.

Forgive my ignorance, but isn't Claris for road bike use? And it seems to be a the bottom of the Shimano options for road bike groupsets, whereas the Deore LX I have on my mountain bike is near the top.

[Brucey]

I've already explained RD compatibility upthread. You have XT shifters already, so use them. Don't buy 9s or 10s shifters and expect them to work with a 7s cassette; they won't.

That the FD sounds a bit clunky on some shifts is not that unusual.

If the FD ever wears out, it won't be that difficult to replace, even though you really need a 7/8s one (a 9s one will work but will rub more easily). The reason is that FDs normally last a long time and furthermore frame fashions change often, so spare parts are not all used and soon go obsolete. Thus you can easily find a NOS or good used FD that is 25 years old on ebay.

cheers

[Laowai_1]

You can use ... any 'road' 10s mech (but not RD-4700), capacity allowing.

cheers

Oh, sorry about my previous post about not knowing what RD-4700 is. I assumed it was a mountain bike groupset, not having fully read your post and - embarrassingly - having forgotten that it is exactly what is fitted to my road bike! Ooops.

[NetworkMan]

I'm not sure if we made it clear upthread but it is the shifter that determines how far the jockey wheel moves when you change gear one step. With only a few, mostly recent, exceptions all rear Shimano derallieurs shift the jockey wheel the same distance for a given amount of pull on the cable and this is true for both road and mountain bike ones. What's more the cage is wide enough for 7/8, 9 or 10 speed chain.

Deore XT is above my pay grade but I have an LX on one bike and an Acera on the other. If anything the Acera works better (it's newer) but essentially they are both fine. The jockey wheel bearings are both plain ones - no real difference I can see. The LX has more plated parts than the painted parts on the Acera but I can't really see anything that would make it last any longer. The LX is older and does have a little rubber bellows to try to keep dirt out of the cable end but I suspect they may not be fitting that now.

My feeling is that mostly the differences between the cheap RD's and the mid priced ones are cosmetic. Perhaps the XT and XTR have ball races in the jockey wheels but I've never seen one so I don't know.

My 25 year old bike has a 25 year old Exage 300LX relatively cheap FD and it is still working fine too.

It's a brave man who'll disagree with Brucey - he's almost always right! I'd buy whatever you fancy.

[Brucey]

with RDs there are lots of small differences that add up to a real difference overall; certainly in terms of longevity. For example

- coated link pins (eg in XT mechs) so the parallelogram works smoothly and doesn't wear out
- more rigid parallelogram parts (cheaper mechs use pressed steel or even plastic)
- better seals (cheap mechs have none)
- stronger/lighter cage plates (some cheap mechs are positively flimsy)
- better pulley bearings

In shimano mechs there are the flowing different types available
a) plastic on metal bushing, no dust caps
b) plastic on metal bushing, with dust caps
c) plastic on metal bushing, with seal
d) sintered metal on hard metal bushing, with dust caps
e) sintered metal on hard metal bushing, with seals
f) ceramic on ceramic bushing, with seals
g) sealed cartridge bearing with additional seals

So Claris has b/d pulley bearings with plastic/pressed steel parallelogram parts (and so does acera) whereas XT has f/g pulleys and far stiffer parts in the rest of the mech. They usually work better for longer.

cheers

[Bez]

Not even close. Deore DX and LX were near the top of the shimano heirarchy and acera is near the bottom. Anything new is likely to be better than anything worn out, but acera is a fair step down. I'd suggest deore LX or XT parts if you want them to work well and to last well.

A fair point but one which is offset to a large extent by trickle-down over the years. Certainly I think even low-end modern stuff works much more smoothly than anything I remember from 25+ years ago, although I doubt longevity will have seen the same trickle-down. (Though—hubs aside—durability doesn't feature highly in my memories of very early 90s Shimano drivetrains.)

[NetworkMan]

Just back from the shopping on Spa Tourer with magic Vic. Hypers on super Kinlin XR22T/XR22RT rims and 8 speed faultlessly shifting Acera rear and Claris front mechs

All four of my Shimano RD's up to and including LX look like b/d. That is to say metal on metal at the top, metal on plastic at the bottom, with a dust cap each side which makes a sort of labyrinth seal, running in a groove in the pulley. I try to remember to take them apart, clean and re-grease every year. It's a real chore. If I bought an XT would that be unnecessary?