So, I'm looking to build up a new frame that I'm getting, and for some reason, I'm really drawn to the old school Mavic stuff. I usually throw my bikes together with whatever I can get a good deal on without much regard to what it actually is. Now that I'm looking for particular parts it's looking like it's going to be expensive (relatively speaking anyways). I've come across a Mavic 851 rd for a really good price, but it's missing the washer mounting plate.

rd missing plate



with plate


Is this something I could possibly salvage from a less rare derailleur or am I just out of luck.


also, what kind of gearing should I be able to use this with. I know that it is shimano compatable. Will I only be able to use 7spd? Or might I be able to possibly go 8 or 9 speed with it?

You'll have to try it to run 8/9 with it but I've been able to run 10s (2x10) friction with early 80's Nuovo Record RDs, so chances are it'll work.

Without that plate you mention, it won't work at all.
And the plate is on backwards in the photo.

I am aware of it's necessity, but what I'd really like to know is if this is a mavic rd specific part or is it something I might be able to find off of another derailleur to use on the mavic...

I am pretty sure it is a not only a Mavic specific part but a specific part that one RD. I would not mind having one of them too but they are pricey

drats!

seller is only asking $40 for the one without the plate

BTW, the all silver version is called the model 801 not 851. It's totally identical mechanically and functionally to the 851 SSC just a finish difference where the 851 has the dark anodized parts.. No, it won't work if you do not have the limiter plate as the derailleur will swing too far forward on the hanger and possibly jamb tha jockey wheels and cage against your freewheel. I dont know if any other plates will work from other RDs, but I have seen some 851s and 801s for sale once in a while where the plate was copied/made from scratch from steel plate stock by the seller. I guess if one is skilled enough with metalworking, one can also copy it as long as you have one for a pattern.
Only used both these deraileurs for up to 7 speeds in combination with Simplex/Mavic Retrofriction shifters. I do have to tell you that at 7 speeds the Retrofrictions are at their limits and take almost the full stroke of the right lever to shift through the whole cluster, but it does work.
The washer plate shown in the bottom pic is indeed bacwards. The two legs pointing to the right should straddle the pivot barrell where it meets the hinge holes for the inner derailleur arm.
I love these RDs as you can see from my stash of 851s which I plan to use on my next French bike build projects.


Chombi

As stated, the part is Mavic specific to that type of Mavic rear derailleur. Also, as stated, this derailleur with corresponding shifters won't go beyond 7 speed.
Now if you get a Mavic 841 rear derailleur, that looks more like other modern derailleurs, and their corresponding DT shifters, it will handle 8 speed.

A month or two ago, I corresponded with an member on one of the forums about making extra "plates." He determined that the thickness of the metal and his tools or the lack there of would not be something he wanted to try.

If you can find someone who makes copies of those things, and could get them at a good price, you could make some money because is not uncommon for people to loose that part.

What does the plate look like, off the derailleur? Dimensions?

I'm thinking it could be cut from aluminum plate and the legs bent using a brake or similar.

Found this on the web.

Somebody has got to be able to fabricate one (or dozens) of those: between the uber-talented frankthewelder and the water-jet cutting Henry III I believe something could be done.

It is 2.44 mm thick and very hard. If more dimensions are needed, I measure tomorrow.
Cutting the metal will be the easy part. Bending the tabs without distorting the thing will be more difficult.

could be a tricky thing as you say, but maybe just has to be milled from thicker stock rather than cut-and-bent. Seems easy enough with CNC, but might become pricier.

PM if your interested I may be able to find a similar Mavic with the parts at the local bike coop really cheap.

Wasn't there a thread a few weeks or maybe a month ago about this? Wasn't someone looking for a Member to lend him the part to try and fabricate one?

I'd like a couple of slices of that pie.

That was me BG. Couldn't figure out how to bend 2.5 mm steel, let alone accurately, so I put the idea on the back burner. 2.5 mm is awfully thick material to be bending. And , it has to have a 15 mm hole bored in it, before bending I would presume. Not an easy part to make. Mill it on a machine? Might work, but probably beyond my capabilities.

Yep. I was willing to lend the part. After several emails, the project fell through.

I guess this would be a "labor of love" by somebody like Henry III who's taking a high-tech shop class and has access to a CNC mill... with no pressure to make a profit. Somebody like frank the welder has to cover his overhead and feed a family.

Without that part, the OP's derailleur is nothing but a paperweight or a donor of spare parts. There are two listed on ebay.
https://www.ebay.com/itm/VINTAGE-MAVI...item231a747426

and

https://www.ebay.com/itm/MAVIC-REAR-D...item4600d7dd7c

I have a good used one I'm willing to sell.

I wonder if the solution to making it is in the sequence of the metalworking.
Maybe, most of the bending is done before drilling out the hole for the mounting bolt as it ssems like most of the problem would be figuring out how to make the part without distorting the hole. I fifgre that one might need to leave enough material around the hole beofre the drilling is done to, then all the exess is trimmed. One can also maybe substitute smalll rods for the legs that screw on a large enough metal main plate, similar to the stop on the Campagnolo NR RD?? It can eliminte tha hole bending problem but then one will have to fabricate those rods. It won't look exactly like the original, but it might work.

Chombi

I'm not convinced it has to be steel. T6061 aluminum is fairly strong. The part of the derailleur that touches the ears is likely a softer aluminum. So one could cut and bend aluminum plate.

Or, cut a plate, then drill holes and press in steel pins, or screw in socket cap bolts, to serve the function of the ears.

Hey all, I realise that it's now 4 years since this discussion took place, but in case someone comes across this discussion & is also seeking this part, a NOS/NIP one has just come up for sale upon eBay for only $25 Or Best Offer, plus shipping...

here's the link: Vintage Mavic Rear Derailleur 801 851 Part 801 034 Very Rare | eBay

Cheers & best wishes to all from "Down Under"...Matt.

I know its been a while....
hopefully someone has one or can make some, any info leads would be greatly appreciated.
thank you

Hi there, I just received an email that informed me that someone else had posted upon this thread...I do actually have a spare one, along with my 8 851 derailleurs, each of which obviously comes with its own specialist 'washer'...I'll have a look for it tomorrow, although I'm 99% sure where I've stored it...cheers & best wishes for now from "Down Under"...Matt.