Have I mounted this Simplex RD incorrectly?
09-05-20, 09:02 AM
#1
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Have I mounted this Simplex RD incorrectly?
I switched the Simplex Criterium RD on this frame to a later, longer-arm, Simplex RD, to go with a 28tooth freewheel (which I switched in from the original 24T freewheel). But the derailleur pulley seems VERY close to the 28t cog. Do I have it mounted incorrectly, or is there something wrong with the RD? Or maybe I should back up the spacer screws? The derailleur stop tab is visible in the photo and is on the front edge of the hanger. It seems to be shifting okay on the stand but I'm concerned how it will perform on the road....
09-05-20, 10:35 AM
#2
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Hmm, I'd share your concern, looks stretched to (beyond) the safe limits...but one check: are you sure the chain length is correct?
Another thought: at a glance (and not reliable glancing) the largest cog looks larger that a 28t to me, but you are in best place to know what it is, and that particular Simplex RD "should" be able to handle 28t, but I think any more is beyond it, and depends on what your front (chainrings) are, too since the tooth difference is a factor..
On third thought: you might check out Chas's post in this thread (his usual great and helpful detail about the Simplex Prestige but I bet a lot applies to the Criterium as well)
https://www.bikeforums.net/classic-v...-capacity.html
Another thought: at a glance (and not reliable glancing) the largest cog looks larger that a 28t to me, but you are in best place to know what it is, and that particular Simplex RD "should" be able to handle 28t, but I think any more is beyond it, and depends on what your front (chainrings) are, too since the tooth difference is a factor..
On third thought: you might check out Chas's post in this thread (his usual great and helpful detail about the Simplex Prestige but I bet a lot applies to the Criterium as well)
https://www.bikeforums.net/classic-v...-capacity.html
Last edited by unworthy1; 09-05-20 at 10:57 AM.
09-05-20, 11:05 AM
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Firstly, if you can still turn the cranks backward smoothly with the chain on the small chainring and largest rear cog, consider it good as-is.
The angle can be adjusted by re-balancing the tensions of the B-tension and cage-pivot springs.
The one photo doesn't show this derailer's mechanical configuration in this regard, but firstly is there a locknut on the cage pivot shaft that locks the pivot shaft from turning relative to the cage? That was the way that the plastic Simplex derailers provided cage-pivot spring tension adjustment.
There are also generally holes or slots for the ends of the springs to anchor into, often there are two provided which allows a tension change upon reassembly. New holes can be drilled in some cases as well.
I have re-balanced the spring tensions on derailers (such as the Huret Rival and the Campag Gran turismo) by drilling alternate holes for the spring end peg or by forcibly relaxing one of the springs (as on the Rival).
In your picture, you can actually see spring end anchor holes in each of the large-head hex bolts at each pivot. It might also be simple to add a shim or sand down a seating surface in this area to slightly alter the rotational orientation of one of these bolt heads(???).
Note that disassembly may need to be done from the opposite (back) side to prevent mangling the spring (from turning the bolt head).
Also note that the needed direction of rotation of either anchored end of the spring might not be totally intuitive since it depends on which end of the spring is stationary (and which end actually rotates with the body or with the cage).
Welcome to the world of modifying old bike components. Hopefully some actual adjustment option is present on your particular mech.
The angle can be adjusted by re-balancing the tensions of the B-tension and cage-pivot springs.
The one photo doesn't show this derailer's mechanical configuration in this regard, but firstly is there a locknut on the cage pivot shaft that locks the pivot shaft from turning relative to the cage? That was the way that the plastic Simplex derailers provided cage-pivot spring tension adjustment.
There are also generally holes or slots for the ends of the springs to anchor into, often there are two provided which allows a tension change upon reassembly. New holes can be drilled in some cases as well.
I have re-balanced the spring tensions on derailers (such as the Huret Rival and the Campag Gran turismo) by drilling alternate holes for the spring end peg or by forcibly relaxing one of the springs (as on the Rival).
In your picture, you can actually see spring end anchor holes in each of the large-head hex bolts at each pivot. It might also be simple to add a shim or sand down a seating surface in this area to slightly alter the rotational orientation of one of these bolt heads(???).
Note that disassembly may need to be done from the opposite (back) side to prevent mangling the spring (from turning the bolt head).
Also note that the needed direction of rotation of either anchored end of the spring might not be totally intuitive since it depends on which end of the spring is stationary (and which end actually rotates with the body or with the cage).
Welcome to the world of modifying old bike components. Hopefully some actual adjustment option is present on your particular mech.
Last edited by dddd; 09-05-20 at 11:12 AM.
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09-05-20, 11:12 AM
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Check the difference, if any, between the mounting pivot point and the cage pivot point between the two RD's. One may be shorter than the other.
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09-05-20, 12:57 PM
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BTW, Just in case you do not know....please do not use the exterior hex to remove the D. This causes the washer mentioned above to strip.
Best, Ben
Best, Ben
