balindamood

I have read several accounts here and elsewhere equating the Shimano Deore 'Deerhead" Super Plate (M-700SP) derailleurs to Suntour Mountech of the same vintage; and in doing so, implying they should be trashed as they gum-up and are effectively unserviceable. I have found this to be untrue.

Backstory:

I picked up an original '85 Schwinn Cimarron last year that was well taken care of, but also reasonably well used. The second owner from which I had purchased it had bought it from a doctor in the early 1990's. The bike clearly had been sitting for a while. My intention was/is to upgrade my current utility bike ('85 Schwinn Sierra) and I have finally gotten around to stripping it down for a thorough re-build before pressing it into service. The M-700SP RD was VERY full of crud. Although the pullies would turn, it would not drop into the bottom two gears. I was left with the dilemma as to wanting to keep it relatively original, but the rear derailleur clearly needed a full tear-down which conventional wisdom would suggest is a waste of time.



Differences between the M-700SP and the Mountech:

I have rebuilt Mountechs before...sometimes even successfully, but it is a royal pain. In looking at the M700, there are some clear differences. First, the upper jockey wheel on the Mountech is plastic, but it is steel on the SP. I have seen many a Mountech where the upper jockey wheel was trashed, broken, or even missing. Once the jockey wheel locked up, it was metal (chain) vs plastic (jockey wheel) and metal always wins. Secondly, the lower pivot spring in the Mountech is actually a clock-spring sort of affair within the upper jockey wheel. The chain provides an ample amounts of crud that, over time, accumulates inside the jockey/pivot mechanism, gumming that up and the derailleur no longer tensions properly. This is also a real PIA to re-construct once it is cleaned.

The SP is different. While both derailleurs have a third sprung point for the jockey cage (which is why they are probably considered the same), where the Mountech has a 3rd spring, the SP has a cable that connects it to the lower spring such that both pivot points operate from a single spring within the derailleur body, thus eliminating the third spring. There is really little or no room for crud to accumulate inside the upper jockey wheel, and if it did, the impacts would be far less significant.

Noticing this, I decided to simply re-build the derailleur and see how hard it would be compared to any other derailleurs. What else would I have to lose other than an hour or two?

Tear-down was relatively simple. Thankfully there is a complete diagram for the M-700SP on Disaeli Gears to work from. There was enough crud in the lower cage that I was not sure what was plastic and what was just caked on grease and dirt.


After three 20-minute sessions in an ultrasonic cleaner and further touch-up with degreaser, putting it back together was simple. I will further note that while it is a little more effort than a standard derailleur, the upper pully can be removed and cleaned out without completely taking the derailleur apart.

Here is the rebuilt derailleur, ready for another 35-years, hopefully.

merziac

Well I'm not normally a fan of them either just because but the Ritchey build required their consideration as I had them in stock and just about any C+V MTB build discussion brings them up.

Mine were not too bad and I tore them down as to shine them up the best I could, the rear is not a specific Deerhead but same as or very close I think. the front is a Deerhead and the better condition of the 2 I had in stock. Both cleaned up well and seemed to adjust and function just fine with very little drama.

So they work fine and look the part as they should. I always think things like this are dependent on the skill and maintenance of the operator, if you're going to muck them up and ignore them, they will protest like many things. You can bet many who raced with them learned soon enough that you will take care of them or else, they seem to work well if maintained, its not rocket science or surgery.

scarlson 

Wow, a Superplate teardown!! I don't think I've ever seen inside one.

Is the top pulley of yours all-metal? Or just the "fence" riveted to it? Some of them (earlier ones I guess) had a plastic "fence" on the pulley and these were prone to coming apart. Not sure how shifting performance was affected by that, but it must be there for a reason.

I toured on a Superplate in the early 2000s, which I guess is like touring on a M952 XTR today?? It worked fine! Even survived the 2001 tornado in Siren WI. We were camped nearby but luckily the campground was not hit directly. I remember the sky turning green, our tents being blown down on top of us, and seeing lightning and hearing thunder at the exact same time. A testament to the Superplate mech's durability!

balindamood

Yes. The top pully is all metal. Seems to be a steel outer ring riveted to a steel pully wheel. That one piece is almost as heavy as the entire derailleur body.

flipchip

Holy how tall are you? Those wheels almost look like 20 inchers on that frame.

merziac

Yeah, I get that a lot, no sense of humor about fit, I never raced or wanted to be hunched over at all. I go to great lengths to get the bars in my comfort zone.

6 ft tall, 38 in inseam, my daily rider is a 66cm so....

tricky 

The problem with mine was that the little internal linkage that's made out of a cable and two little cable ends had snapped. If that little cable goes then you are SOL unless you make yourself a whole new linkage somehow. I would be fine running one otherwise. They are pretty cool except for that stupid little point of failure.

bamboobike4

There goes any self-esteem I had left as a bike wrench.

merziac

Used to be some motorcycle shops made cables from scratch, pretty sure some restorers still do it, whether they can or will do this would be the question.

tricky 

I've watched a few vids about how to do it. It would of course need to be adapted to the tiny little cable ends on that linkage though. https://www.youtube.com/results?sear...orcycle+cables

merziac

You might be able to start with a standard brake cable, trim the barrel end as it looks to be a smaller version of that and then only have to cast the other one.

scarlson 

I think that the overbuilt steel pulley may have been a later update, based on experience with the plastic ones degrading on Shimano Superplate and possibly even the competing Suntour Mountech derailleurs. Although I'm not sure if there ever were all-plastic versions, I'm sure early ones came with a plastic outer ring (or as I called it, a "fence"). But I'm not sure if there ever was a plastic pulley as well. This is probably the secret to these things holding up. The Mountech pulley was plastic and degraded horribly after very little use.

scarlson 

I don't like casting cable ends. Casting is finicky. If it's a simple shape, I usually will crimp a piece of brass or copper around the cable (in approximately the right shape) and then solder it on, and finish up with some filing. This usually works and requires less dedication than casting.

merziac

I know its tricky, mc shops used to do it all the time, never seemed like a good idea to me, oldschool craftsmanship lost to the sands of time like so many things.

This might be a good candidate for that if the recess is not too small, drill a hole in a small piece of tubing, jam the cable in and go one way or the other, cut it flush and solder it up.

balindamood

This derailure has a Jan '85 date code. The only other deerhead bike i have down right now is not a super plate. I will have to climb up in the barn and look at the '83 and '85 Montare and the '85 Ascent and see what they have. Perhaps later this weekend.

bikemig 

Now I feel the need to take my deerhead RD out of my parts stash and clean it up. But then I'd have to buy a bike for the it . . .

Nice job of explaining what you did to get it running.

balindamood

Okay. After digging about, I have only one other super plate; also with a steel upper jockey wheel and a 1985 (september) date code.