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scozim

My understanding of Simplex dropouts is they are not threaded and the Simplex derailleurs were designed to have a 5mm bolt screw into the derailleur from the inside of the hanger.

This begs a couple of questions:
1) Is Ebay about the only source for Simplex rear derailleurs (and then it's a gamble on condition) anymore?

2) Can the drop out be tapped to accept a threaded rear derailleur?

Scott

verktyg

Scot,

The all metal Super LJ rear derailleurs on eBay are "usually" in pretty good shape but tend to sell for a lot of money.

If you plan on riding a bike any amount, I would avoid the old Simplex derailleurs with plastic parts because 25 to 40 year old Delrin can have cracks, deterioration of the plastic or they are just plain worn out. If you get a good one they're OK for the occasional classic club ride or a display bike.

This weekend I installed what looked like an almost new 1972 Simplex Criterium derailleur on my 1969 TdF that I'm just finishing overhauling. The Criterium was the top of the line Simplex Delrin black plastic model used on TdFs and PX-10s until at least the mid 70s.

The derailleur wouldn't tension the chain properly so I disassembled the top pivot and found that the spring inside was bent. It may have come from the factory that way!

I had to drill a small hole in the red plastic plug and use a small wood screw to pry out the plug to access the 5mm hex socket so that I could remove and reassemble the top pivot. After re-bending the spring it works perfect now.

I don't know if I ever disassembled a Simplex rear derailleur before. If they didn't work properly we just replaced them. New ones were only ~$3-$4.

Simplex Criterium derailleurs were more expensive and less readily available. Sometimes you will see one of the standard Prestige derailleurs on a TdF. It was probably a replacement for a Criterium model.

Late 60s Simplex Criterium

1970s Criterium

late 60s, 1970s Prestige derailleur

Prestige with "claw" mount hanger. Most Simplex RDs with this kind of mount have to have the top pivot bolt replaced to work on dropouts with integral derailleur hangers.

I suspect that some of the new looking Simplex RDs on eBay may have been take offs that didn't work properly! Rolling Eyes

Note: the sprung pivots on Campy and some Japanese derailleurs are a bear to reassemble! The Simplex was really easy to put back together.

Simplex dropouts have a 9mm hole for the derailleur mounting bolt. Some of them have a recessed counter bore in the back side for chain clearance.

They can be easily tapped out with a standard M10 x 1.0mm tap.

No need for a batard, bastardo Campy 10mm - 26TPI tap as the thread pitch is almost identical.

These will probably require a backup washer to fill thr recess and a thin locknut because there wont be many threads.

To use an older Campy of similar style derailleur on one of the old Simplex dropouts the rear of the dropout needs to be filed or ground away a little for the stop on these derailleurs.

Some of the later Japanese and maybe even some Campy derailleurs don't require the modification to the rear of the hanger.

scozim

Chain tension is the issue I had with my SX410 on the Sprint when I swapped it out this winter. However, I'd like to be able to use the Simplex derailleur again because I liked the feel while riding. I may try to take it apart this weekend and see if I can find out what the issue is.

If I can't figure it out how are these for a replacement - S001 model:

I'm assuming a bike shop should be equipped to tap out the hanger if need be but most of the ones around me are new bike oriented.[/img]

verktyg

scozim

I grabbed my derailleur out of the shop tonight - SX630 and took the upper pivot spring out. It actually came out quite easily. (Side note: I was cleaning it off and my wife asked me a question. I looked up and heard a slight metallic "ting" and looked back down at my rag and Doh! - where's the ##&@*$& spring? Shocked

I finally found it under the wood stove.)

The spring looked in good shape and went back together fine after I cleaned it up.

So I'm wondering if the problem with not taking up chain slack may be the way it was installed on the bike. There's the little tang/pivot stop and I wonder if that was installed incorrectly and it kept the derailleur from pivoting back as far as it needed to. The primary problem was in the small ring - if I backpedaled you could see the chain flex down and hit the chainstay. I was always wiping grease marks off the chainstay.

So, here's the part I'm talking about:

Here's how it was installed on the bike right after I had picked it up from the bike shop I purchased it from:

verktyg

The tab goes to the front of the dropout. Several times I've had to look at another bike to double check when it's been some time between working on a Simplex (like this past weekend). Embarassed

There are two holes inside the Criterium derailleur to adjust the spring tension. I chose the tighter one but now the top pulley is too close to the 28T sprocket and drags a little. Mad

Another thing, you might try removing a link from the chain. I had to do that with the TdF I'm working on. I'm using a 14-28 freewheel with 50-38 tooth chainrings. 50T-28T is not a good combo but it wont go anyway.

Strange because back in the day we used to run 52-42, 52-40 and even sometimes 52-36 chainring combos with 14-28 freewheels. I've even seen Simplex Prestige RDs work with 14-30 and occasionally 14-32 freewheels. I think that I remember something about Criterium RDs were more race oriented.

scozim

Thanks for all the help Chas.

I'll keep working with the derailleur. I switched it out for an NOS Suntour this winter and the chain tension is perfect (i.e. no more greasy chainstay). I'm acquiring a mystery Reynolds 531 frame with french threads and would like to re-use the Simplex derailleur.

hnoor0044

I had to do that with the TdF I'm working on. I'm using a 14-28 freewheel with 50-38 tooth chainrings. 50T-28T is not a good combo but it wont go anyway.