Need help finding a new rear derailleur

[sergei791]

Here's my repair situation: I have a what seems like a relatively nice road bike which I found for free on the side of the road years ago. Around three years ago, while cycling, there was a stuck link in the chain that caused it to jam. As I was pedaling uphill, the force caused the metal near the mount screw on the rear derailleur to shear. I have recently wanted to repair this bike. Unfortunately, it seems I threw out the broken derailleur so I can't use it as a reference for "what would fit," and instead have gone on a researching adventure to see what would fit my setup.

In the meanwhile, I tried to replace the derailleur with one from another broken bike I have started to cannibalize. If we take this picture (https://imgur.com/BumRwWJ), if I mount the bolt-on derailleur on hole 2, I get this result: https://imgur.com/NsxwnmX. The parallelogram is completely blocked from shifting out of 6th or 7th gear by the hanger. If I mount the derailleur on hole 1, I get this, https://imgur.com/dRdD2U6, where the rivets on the side of the parallelogram also get caught on the hanger between 4th and 5th gear. Slightly more workable, but still far from ideal

Unlike the hangers on what seems like every other bike I've seen on the internet, this one doesn't seem to come off. Therefore, I'm looking for a new derailleur to buy to mount off the hanger (non bolt-on, to avoid the problems I encountered). Here's my current setup:

*I checked and the front derailleur (still working well, albeit rusting) is a Shimano Exage 300 LX. It seems these are no longer in production, and the used ones on eBay are out of my price range (~$60, I would like to keep things under $40).
*The tooth capacity I need is (48-28)+(28-12)=36, with a max rear of 28 teeth. This would require a medium cage from what I've read.
*There are three chainrings up front.
*I'm not 100% sure, but it seems I'd need a direct mount derailleur, not one with a hanger (can I have confirmation on this?)
*It's a 7 speed cassette, but I don't know the model or pull ratio of the shifter - I would assume it's a standard 2:1 for Shimano?

Could you guys recommend a derailleur to buy for these specs? Searching online is cancerous because none of the websites I have visited allow you to filter on this level of detail of specifications, and some don't even list these specifications in the part description either. Thank you so much, this endeavor has currently brought a lot of frustration with it so far!

[Painkiller]

look for a shimano rd-2300 rear derailluer. It is recommended that the rear wheel be trued and the derailluer hanger alignment be checked before installation.

[Jesper]

(07-02-2020, 06:56 PM)sergei791 Wrote:  *I checked and the front derailleur (still working well, albeit rusting) is a Shimano Exage 300 LX. It seems these are no longer in production, and the used ones on eBay are out of my price range (~$60, I would like to keep things under $40).
*The tooth capacity I need is (48-28)+(28-12)=36, with a max rear of 28 teeth. This would require a medium cage from what I've read.
*There are three chainrings up front.
*I'm not 100% sure, but it seems I'd need a direct mount derailleur, not one with a hanger (can I have confirmation on this?)
*It's a 7 speed cassette, but I don't know the model or pull ratio of the shifter - I would assume it's a standard 2:1 for Shimano?

Could you guys recommend a derailleur to buy for these specs? Searching online is cancerous because none of the websites I have visited allow you to filter on this level of detail of specifications, and some don't even list these specifications in the part description either. Thank you so much, this endeavor has currently brought a lot of frustration with it so far!

I agree with Painkiller. I also think that the price for your front derailleur is 2 to three times too high. I might try the same group model rear derailleur (Exage 300LX). I would think you could get both derailleurs for about $40-$60 (plus shipping) in decent condition. I know I've seen your same FD for $15-$25, and the RD for $25-$50. Definitely want a direct bolt-on the dropout style with a med. to long cage. If you are just replacing the rear derailleur you should certainly be able to keep costs under $40 if everything else is functioning properly. I don't know if you have a bike collective/Co-op in your area, they usually have a fair amount of used parts hanging around for cheap. Even at a regular bike shop they shouldn't charge the prices you quoted. Call around and see what's available, this should be a fairly cheap repair if your frame and wheel are okay.

Take care,
Jesper