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Replacing a front derailleur
#1
My wife bought a bike from Facebook market place yesterday, its not in wonderful condition and I have been asked to help out make it fit for use.

I don't know much about bikes and everything I have learnt has been in the last 24hrs - so apologies if any of my terminology is off!

This is the bike:

https://www.thebikelist.co.uk/apollo/xc-26s-17-ladies-2009

It is ok to ride but it is impossible to shift the front gears. I had originally thought it was the gear shift, however I have tried to manually adjust the front derailleur and it is seized solid. No movement in it at all! It is all rusted up, I have tried adjusting some of the screws but they are completely shot with rust and strip when I try to adjust them.

I have ordered a new grip shift (which looks a straight swap) of what is already on the bike.

https://www.halfords.com/cycling/bike-parts/gears-drivetrain-and-cables/sram-mrx-comp-3-speed-front-derailleurs-and-spares-gear-shifter-778274.html

I am also trying to find a new front derailleur to buy. I took off the seat post and measured the diameter of the frame and think it is 31.8mm. I think I need a 7 speed derailleurs (based on the number of gears on the back wheel), I think the current derailleurs is a top pull but was looking at a dual pull so I can have it work either way. I was looking at this on ebay:

https://www.ebay.co.uk/itm/Shimano-Tourney-TX51-Front-Derailleur-Gear-Mech-Dual-Pull-31-8-34-9-63-66degree/202474169125?epid=3024918509&hash=item2f2466a325:g:-T4AAOSw6M9bthVn

It looks right, but then talks about an angle!? 63-69 what is that in reference to and what do I need .

I have attached a couple of photos but can upload more if needed.

   
   
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#2
(08-02-2020, 03:46 AM)ekim Wrote:  My wife bought a bike from Facebook market place yesterday, its not in wonderful condition and I have been asked to help out make it fit for use.

I don't know much about bikes and everything I have learnt has been in the last 24hrs - so apologies if any of my terminology is off!

This is the bike:

https://www.thebikelist.co.uk/apollo/xc-26s-17-ladies-2009

It is ok to ride but it is impossible to shift the front gears. I had originally thought it was the gear shift, however I have tried to manually adjust the front derailleur and it is seized solid. No movement in it at all! It is all rusted up, I have tried adjusting some of the screws but they are completely shot with rust and strip when I try to adjust them.

I have ordered a new grip shift (which looks a straight swap) of what is already on the bike.

https://www.halfords.com/cycling/bike-parts/gears-drivetrain-and-cables/sram-mrx-comp-3-speed-front-derailleurs-and-spares-gear-shifter-778274.html

I am also trying to find a new front derailleur to buy. I took off the seat post and measured the diameter of the frame and think it is 31.8mm. I think I need a 7 speed derailleurs (based on the number of gears on the back wheel), I think the current derailleurs is a top pull but was looking at a dual pull so I can have it work either way. I was looking at this on ebay:

https://www.ebay.co.uk/itm/Shimano-Tourney-TX51-Front-Derailleur-Gear-Mech-Dual-Pull-31-8-34-9-63-66degree/202474169125?epid=3024918509&hash=item2f2466a325:g:-T4AAOSw6M9bthVn

It looks right, but then talks about an angle!? 63-69 what is that in reference to and what do I need .
I have attached a couple of photos but can upload more if needed.

Welcome ekim!

Although front derailleurs are fairly simple overall, there are still some considerations that should taken into consideration.
One quick thought would be to replace the part with the exact same thing, thus eliminating any issues that may result from incompatibility if using a replacement part. That part, in good condition, is probably available at low cost (approx $15-$20) used on eBay or similar sites. The Shimano model number should be stamped on the driveside of the cage.
The 31.8 is a common size so you have that correct.
I am not sure why you want a "dual pull" unit for that bike since it would appear from your photo that it is a "bottom pull" configuration having the cable routed from the bottom of the frame up to the derailleur. You would only be able to utilize the "top pull" option on a "dual pull" unit if your frame is configured for it (proper fittings, guides, cable housing stops, etc.). You can probably convert your bike for "top pull" routing if that's what you really want.
Without me going into technical details, I would reference Sheldon Brown's "All About Derailleurs" (sheldonbrown.com) which I believe can clarify what you need to know. It should explain why the seat tube chainstay angle is important so as not to have the derailleur be interfered with, as well as other issues. I would contact a bike shop and have them verify compatibility if you replace the unit with something different.
Due to the obvious exposure to the elements, I would highly recommend a full service of the bike after getting the front derailleur issue resolved; whether you do the work or have another do it. I think it may be advantageous to replace the chain also seeing it appears to be rusted a bit, and an improperly maintained chain (even if not worn out) can effect shifting to a great degree. The chain may be quite useable, but it needs an extensive cleaning while off the bike which may be outweighed by just replacing it (get it checked for "stretch" and save as a spare if still useable).
Take care,
Jesper

"I am become Death, the destroyer of bicycles." NJS
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