jonwvara 

My search for an affordable long-cage Simplex derailleur having failed to bear fruit, I decided to build up my TdF project with a Simplex SX610 I have on hand. This is the "touring"--as opposed to "grand touring"--version, which has the cage pivot near one end, rather than in middle, as for the racing version. (The GT version has a long cage.)


My goal was to build it into a 49-42-32 triple, with a 14-28 freewheel. (That didn't give an ideal set of ratios, but to paraphrase Donald Rumsfeld, you build bikes with the parts you have.) According to Velobase, the SX 610 will handle a 28-tooth rear cog and has a total capacity of 28 teeth, so I figured that with any luck I could use the small ring with the 28, 24, and 20-tooth cogs before chain slack got to be a problem. (Of course, that assumes a long enough chain to handle the 49-28 combo.)


Long story short, not only did it not work, it didn't come close to working. After a bunch of fussing around with various front chainrings and different freewheels, I determined that the SX610 in my possession has a total capacity of 23 teeth. And that's only after I removed a stop pin threaded into the side of the cage that limits the rearward travel of the cage. With the pin in place, the capacity was something like 18 teeth.


I'm kind of confused. The derailleur I have seems to function normally, and is rotated as far to the rear as possible in the hanger. What am I not understanding here?

CliffordK

Photos of the derailleur in the big/big and small/small combo?

The Specs show that the GT should wrap 38T, and the 610T should be 28T.

Simplex SX610 GT derailleur
Simplex - La Nouvelle Generation scan 3

The article above, however, isn't so kind to the derailleur.

pastorbobnlnh 

Jon, sounds as if something is wrong with your particular RD and not the model in general. That is an amazing lack of chain wrap.

Barrettscv 

I agree, possibly the pivots are not free to extend the derailleur fully.


Several of the Simplex short cage models had a generous 30 unit chainwrap specification. I had good luck with the SX100 when used with a 46,42 & 30 chainring set and a 13-30 rear freewheel.

VeloBase.com - Component: Simplex SX100 T


It provides a 30 unit chainwrap specification and has a safety margin. It worked well on the 3 largest cogs while on the granny gear. It also takes a 30 cog easily. It's a basic unit but shifts perfectly. Both pivots are sprung, its a good quality design.

iTod

Could it possibly be a tension issue? I mean with the derailleur itself. As I'm sure you're aware, there is sometimes a need to tension these where they mount to the dropout, so it might need to be de - tensioned or re - tensioned as needed. I ran into that with the SLJ 410 I have on my Mercier. It's a short cage and handles a 32 rear x 36 front, ans long as I don't try big/big. Good luck!

jonwvara 

Good idea--I hadn't looked into re-tensioning the spring at the dropout.


Not trying to be a busybody, but it's probably only a matter of time before you shift into the big-big by mistake. I once went for several years without using that combination, but then one day I did.

Lascauxcaveman 

I've read this on some other thread, but haven't figured out how to do it yet. Swapped mine with a VGT in the interim). It has to be relatively simple; just haven't taken the time yet.

iTod

You use 2 5mm allen wrenches - one on either side of the mounting bolt. By turning the outside mounting bolt, You can adjust tension. I believe that you're not really supposed to monkey with the outside mounting bolt, but when you have used stuff that someone else has surely installed/uninstalled incorrectly at least once before you got it...

iTod

Yeah, I hear ya.
I have found myself going into big/big on more than one occasion. Usually, I'm not going all that fast when it happens, and I'm certainly not hammering. I actually think that if I added another link to the chain, and changed the BB spindle for a slightly shorter one, it might alleviate the problem. I'll get it (closer to being) sorted out after I tear it down and take the torch to it later thiis year or next...

verktyg 

@jonwvara, @CliffordK, @Lascauxcaveman

Please look at my posts under verktyg in this thread, it may answer some of your questions:

https://www.bikeforums.net/classic-vi...-capacity.html

I spent quite a bit of time researching the info I posted in those messages.

@pastorbobnlnh Sometimes the problem is due toa broken or weakened pivot spring. This causes low chain tension.

@iTod Over the years Simplex used several different pivot tensioning methods. Your suggestion to use two 5mm hex keys only works on the early style Prestige and Criterium derailleurs (also the later S001T model). The inboard end of the tension spring fits in a hole in the Delrin plastic body.

Trying to adjust the tension that way will damage later style derailleurs by rounding off the weak lips of the upper pivot bolt. Same thing happens when someone removes the nylon plug in the upper pivot when trying to remove these derailleurs. (see last pictures that show the problem and how to fix it).

When Simplex introduced their all metal Super LJ derailleurs in 1973 they changed the spring tensioning mechanism. In many models, there were 2 holes to locate the end of the tension spring but they were not designed for adjustments. One hole is for short cages marked T and the other for long cages marked X or GT. Most of the later models were not adjustable. See pictures.

@jonwvara On most of my triples I only use the 3 largest FW sprockets with the small chainring. One reason is chain drag on the middle chainring when there's too much difference between the small ring and middle ring e.g. 49-45-30 1/2 step gearing.

On doubles I like to be able to use a big-big combo as an occasional bailout gear when I hit a sudden steep section of road and I'd loose momentum dropping to the small chainring.

I've used standard cage Simplex RDs with 28, 30 & 32 tooth freewheels and 36T 37T and 38T chainrings. An important factor is the chainstay length.

49-42-32T chainrings may be too much of a difference for the chain to wrap up with a standard length cage.


verktyg

An ounce of knowledge is worth a pound of guesses!

Chas.

The Golden Boy 

Yup. Been there, done that. Bought the t-shirt. Even a little snow globe.

I felt "dirty" for the sounds my bike made. And it wouldn't shift out.

jonwvara 

Chas, thank for the reply and for the link to your post on SLJ 6600 real-life capacity. I've referred to it many times in the past couple of years.


It's evident to me now that there's something seriously amiss with this derailleur. The cage has good spring tension, but the body of the derailleur seems to sit too far forward, so that it points slightly upward towards the chainstay. It can be rotated further forward--to the point that it comes into contact with the chainstay--but it won't rotate backward at all. That makes it almost impossible to remove the wheel once the chain has been installed. I had to remove the skewer and work the chain around the end of the axle to get it off. I didn't notice this problem at first, because the chain wasn't yet in place when I installed the wheel for the first time.


Possibly the main pivot spring is installed incorrectly? It doesn't appear to be broken, since the body has spring tension in one direction.


The above information probably isn't of any use without photos, I realize. I will try to post some later today or tonight.

CV-6 

I ran my SLJ touring model with a 51-46-30 and 14-28 combination without issue. It shifted nicely and I was rather surprised the front derailleur handled the 30-46 jump without complaint.

Lejeune Pro by L Travers, on Flickr

jonwvara 

Hey, you didn't crash or break anything, right? You got off easy!

attylah

I recently bought a box of random derailleurs, and in it is a long cage Simplex. I don't know much about Simplex, but does this look like something that might work for you?

jonwvara 

Here are a couple of photos of the SX610 as installed.

The first shows the interface between the derailleur and the dropout. As far as I can tell, it's oriented properly, with the tab on the derailleur hooked over the rear of the integral hanger.

In the second photo, you can see the weird postion of the derailleur body--seeming rotated too far forward. In fact, it can be rotated further forward--against a fairly normal-seeming amount of spring tension--until the cage comes into contact with the freewheel. But it won't rotate at all in the other direction--that is, toward the rear, as one ordinarily rotates a derailleur to remove the rear wheel.

In the second photo, the chain is hanging slack on a 32-tooth chainring and a 22-tooth freewheel cog. I didn't take a picture of the big-big position, but shifted into that--a 45 chainring and a 26-tooth freewheel cog--the derailleur is stretched to its limit. If I'm doing the math right ((45+26)-(32+22)), the derailleur is failing to handle a total capacity of 17 teeth.

Obviously, something is rotten in Denmark.

Does anyone have any idea what's going on here?

jonwvara 

Thanks so much for the offer. That is indeed a long-cage Simplex--maybe a 410 or 810--but it's the model with the mounting claw, whereas I need the direct-mount version without the claw (I forget the letter codes that designate those variants). There's no easy way to convert from one to the other. There were parts for that at one time, I think, but they're unobtainable today.


Also, the plastic body seems to have a big crack--look on the right-hand side of the second photo.


Thanks again! I really appreciate the offer of help.


JV

USAZorro

Looks like the issue is with the spring, the pivot, or both.

jonwvara 

I think it was Frank Zappa who said "Stupidity has a certain charm. Ignorance does not."


I just figured out (or think I did) that I had the derailleur tab on the wrong side of the dropout. It seems to work fine now that I've moved it. Oops.


Write this one off to what a commercial pilot friend of mine used to call "a short circuit between the headphones."

jcb3

I'd be interested in the Simplex GT if no one has spoken for it - from the picture, the bottom housing looks cracked -

I've been keeping my eyes out for a spare long cage.

Thanks

Joe

jcb3

Should work - the tab must be in front of the hanger.

iTod

Oh, snap! I didn't even think of that. I should have, as I had the same issue, but I think I just sort of worked it out, after studying the Simplex posts here (thanks, Chas!)
I think you'll find that derailleur punches above its weight, and shifts very nicely.

Lascauxcaveman 

@verktyg @jcb3 Thanks; bookmarked for when I decide to put the long cage SX610 back in service.