BunkFunk

Can someone please help me get out of a pickle...

I am building a bike and am looking for a front derailleur with these following parameters:

28.6 clamp on
top pull
compatible with 52-42-30 crankset (and 7-speed rear)

^ Question 1) does one exist?

I have been trying to search the web in general, but it is difficult when looking for all the above at once!
I've come across a few models that come close, but they are either bottom-pull or braze-on.

Shimano says they don't make any, (Question 2) but, did they at one time (i.e. - is there an older model that I can look for on Ebay?)?


In addition, I have seen a braze-on/clamp-on adapter online for purchase. It is a clamp to fit on my bike that a braze-on derailleur can fit into. Question 3) Are there any problems with using one of these if I find a derailleur that fits all the other parameters?

Thank you!

Retro Grouch 

The deal breakers in your equation are top pull derailleur that has a cage arc to match the 52 chainring.

With your 28.6 seat tube you might be able to kludge a clamp-on pulley from an old 3-speed bike to the bottom of your seat tube. This problem comes up frequently enough that I'm surprised that "Problem Solvers" hasn't marketed a part to fix it.

Cyclist0383

Shimano makes after market clamp on shims to fit 28.6 If you can find a FD that suits your other needs then with the shim you are in luck.

https://www.bike-components.de/catalo...da481ee0948c8e

AnthonyG

I'm running a front derailer with a 31.8 mm clamp diameter on a 28.6 mm seat tube with shims with no problems at all. If you use the Shimano specific shims use 2 of them, not just one.

Regards, Anthony

Gummee

Now yer getting into the 'way back stuff!' I do believe that Shimano (and Suntour) both made top pull derailleurs back in the late 80s/early 90s. XTR stuff 'should' work if you can find one.

M

Thor29

XTR won't handle the 52 teeth large chainring.

BunkFunk

yes, it appears that any MTB derailleur won't handle a 52 teeth ring and all road derailleurs are bottom pull. And all dual pulls that I've come across seem to max out at 46 teeth.

Unless I can find out that an older model that was top pulling and could do 52 teeth and find it on eBay, then I'm going to have to go with the pulley option to work with a road derailleur (which I've been trying to avoid...)

Thanks for all the help, though. This is a real head-scratcher.

Cyclist0383

Shimino makes an LX FD (FD-M581-3) that is dual pull and made for 48 teeth. They are usually very consertive on the max. teeth rating. Perhaps it would work.

https://bike.shimano.com/catalog/cycl...=1149228909070

AnthonyG

I have fitted a road 30-42-52 triple crankset to 2 Mtn bikes with standard Mtn deraliers and it worked fine despite all that everyone said and wrote. It may not have been ideal but I didn't notice any issues with the setup.

Regards, Anthony

LWaB

Sachs used to make exactly the front mechs you are looking for but that was pre-SRAM.

Gummee

It will, it just won't like it too much. There's been several guys I know of riding large mtn rings with XTR derailleurs.

Heck! Buy one used for not a lot, if it don't work, try something else!

'Course, I AM talking about late 80s XTR not the modern stuff! IIRC, XTR had ~48t rings back then...

M

BunkFunk

new development -
When I went to my local shop a few days ago to begin the project of attaching a pulley and bottom-pull derailleur, the owner was looking through his piles and mounds of parts and he found an old Suntour derailleur from a 3-speed that he had completely forgotten about.
It is working like a charm...and now my 1st bike build is done.

I hope this thread can help out someone in the future. It certainly wasn't easy trying to find what I needed.

Thanks!

edzo

A strong stick like a half broom handle will do the job

gotta ride a bit different though...just initially...and find a place
to keep the stick handy

merlinextraligh

Put a 50 front chain ring on, and an 11 in the back?