Rear derailleur with a difference; lets call it 'Blinky'

[fastpedaller]

To me it looks ok on the bike in the advert

[Brucey]

Looks are highly subjective; it can't be a look that everyone loves else they would have sold gazillions of the things.

As a practical proposition, unless my eyeballs deceive me, there is a significant issue with these mechs; the third pulley appears to be a 9T one. Good luck trying to find another one of those when it wears out....?

cheers

[Brucey]

unusual rear view (From Hilary Stone's website)

No shortage of metal there...?

cheers

[Brucey]

also XC sport

[dim]

I have an old touring bike (Miyata 1000), with Shimano deer head groupset (6 speed freewheel)

The rear derailler is starting to give problems, and I went on the bikeforums.net forum asking for advice on the best replacement

just about everybody said Suntour .... I went to my LBS (one of the best in Cambridge and an older guy with years of experience and regarded by many as the best LBS in Cambridge for older bikes) .... first word he said .... Suntour

[Brucey]

this picture (from Disraeli gears)



shows that there is a leetle problemette; at first sight it looks as if the cage could swing further backwards and keep the chain tensioned. However if it swings much further back than illustrated one of the two lower pulleys may hit a sprocket. The isn't a similar problem when the chain is shortened (there is nothing -except maybe the chainstay- for the mech to hit when it swings forwards) . But the capacity increase may be a bit less than expected...? I would say that the capacity increase is -at best- about the same as the distance between the bottom two pulleys? If so this would be about 3 and a bit teeth more on total capacity...? [edit; this is wrong, it is 3 chain links of slack so about 6T total capacity; the logic regarding mech dimensions below is mostly correct though, I hope...]

If the chain falls off the chainring and the mech swings into the sprockets this can be pretty bad news; some SRAM mechs on some bikes do this and the results are rarely nice to look at.

To get a similar (~3T (I mean 6T...)) increase in capacity by other means would require a ~3/4" longer cage or a larger pulley (say a 16T rather than a 10T) which would hang down about 1/2" more if mounted on the same centres.

FWIW if you wanted to increase the capacity of the three-pulley system, you might choose to use a larger diameter guide pulley, fitted on a slightly lower centre. This would preserve the largest sprocket capacity and wouldn't get in the way when the chain is nearly slack; the movement of the RD is restricted by the possibility of a sprocket clash anyway.

I note with interest that the third pulley in the illustration above is a 10T one; the change to a 9T one was presumably a later one, after they had filed the patent.

cheers

[fastpedaller]

Looks are highly subjective; it can't be a look that everyone loves else they would have sold gazillions of the things.

As a practical proposition, unless my eyeballs deceive me, there is a significant issue with these mechs; the third pulley appears to be a 9T one. Good luck trying to find another one of those when it wears out....?

cheers

Well spotted. An odd choice by Suntour not to use 3 identical pulleys.

[Brucey]

I have an old touring bike (Miyata 1000), with Shimano deer head groupset (6 speed freewheel)

The rear derailler is starting to give problems, and I went on the bikeforums.net forum asking for advice on the best replacement

just about everybody said Suntour .... I went to my LBS (one of the best in Cambridge and an older guy with years of experience and regarded by many as the best LBS in Cambridge for older bikes) .... first word he said .... Suntour

The 'Deer Head' RD-M700 deore mech came in at least three versions, which vary in complexity and reliability. The last (simplest and most reliable) version is very similar to a rebadged 600EX-GS RD. These are OK but (like many twin sprung RDs ) they can eventually suffer problems with top pivot wear. The earlier versions had various extra pivots which can seize up or wear out. The second 'superplate' version is the most complicated, shifts best when new and is capable of giving the most trouble with wear and/or lack of maintenance.


RD-M700, second 'SuperPlate' version

the extra bits.

If you have a 1980's japanese touring bike then really it ought to have either Shimano or SunTour mechs on it, if you are keeping it vaguely 'period correct'. if you talk to a real SunTour fan, they will obviously be very likely to suggest a SunTour mech. They are simpler in some respects but you will be dealing with something that is not only ~25 years old, it will also have virtually zero spare parts availability. When the pulleys wear out you will discover that they use a different fitting on SunTour mechs and on the GT versions of their mechs often the guide pulley is secured in a very non-standard way, often requiring special tools to get the mech apart. Usually this means fitting Tacx pulleys, with difficulty.

cheers

[Brucey]

EV techdocs for the various versions of RD-M700 are here

First (centron lever) version
https://si.shimano.com/pdfs/ev/EV-RD-M700-0561A.pdf

superplate
https://si.shimano.com/pdfs/ev/EV-RD-M700-SP-0615B.pdf

final versions
https://si.shimano.com/pdfs/ev/EV-RD-M700-0698A.pdf
https://si.shimano.com/pdfs/ev/EV-RD-M700-EX-0655B.pdf

RD-6207-GS
https://si.shimano.com/pdfs/ev/EV-RD-6207-GS-0614E.pdf
uses the same pulleys, cage plates etc as RD-M700-EX

cheers

[Mick F]

which is more than slightly horrifying....

Would that be Suntagnolo or Camptour?

Nice one Gaz!

[Brucey]

Campagnolo + LePree has to be

"CamPree"

surely....?

Still horrible though!

cheers