Fitting gear shifter on tt frame



Rochefan

New Member
Aug 16, 2005
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20170321_192715.jpg

As photo shows, I can’t fit a downtube shifter on my TT bike ( I have a standard tri-bar shifter for the rear derailleur but don’t want that for front derailleur – long story). The photo shows a standard downtube shift that was designed for skinny round tubes and if I tighten, it will cut into the carbon of the flat surface. Anyone know a web site selling a suitable version? I could try filing down the connecting piece but its not the strongest material.

Appreciate any ideas
 

alfeng

Well-Known Member
Jul 23, 2005
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IF YOU ARE HANDY ...

FIRST, you need to cannibalize the receiving post from a (vintage) clamp-on downtube shifter ...

THEN, you will want to fabricate a DIY strap which will replace the original strap ...

Make a template from a manila folder OR whatever material is handy for you to use ...

Figure out where you will be "folding" the strap & (especially) where you will drilling the hole which will receive the post ...

CONSIDER installing an auxiliary steel washer between the strap & the post's base ...​

You will ALSO want to epoxy a small "stop" on the frame's downtube which is effectively a cleat which will keep the DIY strap from slipping down the downtube!!!!

Depending on your sensibilities, you can use EITHER a 12" piece of brass stock (¿ 3/8"-to-1/2" wide ?) OR cut-and-fabricate a strap from a large tin can (!?!) ...

Round the corners & coin-and-debur the edges!!!

Secure the ends by mimicking the standard clamp.
PAINT the DIY strap if you use almost any type of steel ...

DONE!!

 

Rochefan

New Member
Aug 16, 2005
55
0
6
IF YOU ARE HANDY ...

FIRST, you need to cannibalize the receiving post from a (vintage) clamp-on downtube shifter ...

THEN, you will want to fabricate a DIY strap which will replace the original strap ...

Make a template from a manila folder OR whatever material is handy for you to use ...

Figure out where you will be "folding" the strap & (especially) where you will drilling the hole which will receive the post ...

CONSIDER installing an auxiliary steel washer between the strap & the post's base ...​
You will ALSO want to epoxy a small "stop" on the frame's downtube which is effectively a cleat which will keep the DIY strap from slipping down the downtube!!!!
Depending on your sensibilities, you can use EITHER a 12" piece of brass stock (¿ 3/8"-to-1/2" wide ?) OR cut-and-fabricate a strap from a large tin can (!?!) ...

Round the corners & coin-and-debur the edges!!!

Secure the ends by mimicking the standard clamp.
PAINT the DIY strap if you use almost any type of steel ...

DONE!!
Thanks but not sure what to make of your suggestion! is there not a version I could buy!!
 

alfeng

Well-Known Member
Jul 23, 2005
6,723
252
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Well ...

If you think about it, there isn't a standard down tube size for TT bikes ...

So, while it isn't impossible for one to exist, I think it is implausible to expect an off-the-shelf "clamp" which will allow an individual to use a down tube shift lever since YOU are possibly the only individual who wants to use one on his/her TT bike.​
So, just exactly WHY don't you want to use the companion, front shifter for your triathlon bars?
 

Rochefan

New Member
Aug 16, 2005
55
0
6
Well ...

If you think about it, there isn't a standard down tube size for TT bikes ...

So, while it isn't impossible for one to exist, I think it is implausible to expect an off-the-shelf "clamp" which will allow an individual to use a down tube shift lever since YOU are possibly the only individual who wants to use one on his/her TT bike.​
So, just exactly WHY don't you want to use the companion, front shifter for your triathlon bars?

you are right of course. its a TT bike I built up from ebay as only do 1 or 2 TT's a year. I don't have a front shifter for tri bars and only need small chainring for warming up/down. I like the simplicity & look of it on downtube also. anyway it seems I need to go down the conventional route and put one on the tri bars.
cheers for your thoughts
 

alfeng

Well-Known Member
Jul 23, 2005
6,723
252
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OKAY!?!


IF the seat tube on your TT frame is ROUND or the actual seatpost is ROUND ...

THEN you may be able to clamp a "traditional" downtube shifter clamp onto it.​

You will need to figure out WHERE you can mount it so that it doesn't intrude with either your foot or your leg ...

And then, you will PROBABLY want to add a "CLEAT" (i.e., EITHER epoxy a small tab OR insert a screw which has a reasonably large head ... OR, you may be able to simply use a piece of old inner tube between the frame & clamp) which will keep the clamp from slipping down the seat tube.