Rear mech positioning screw issue on steel bike frame...

[gentlegreen]

2020 was a bad year to have my old MTB frame break and somewhat hastily I ended up buying a second hand steel-framed bike (Ragley blue pig) which I transferred all my road-friendly parts to...
It's the wrong bike in many ways but it got me to work and back and back in the summer worked well for my daily exercise on a rough cycle track and my hope is that it will again come the spring...

I fitted a new SRAM rear mech as the jockey wheels were worn and all seemed well until yesterday when I needed to ride it for the first time after several months...

The rear mech seemed wedged on the big rear cog and I assumed the return spring had failed - but when I got it on the stand today I realised that the rear mech limit screw had forced its way past the ridiculously small flange on the frame - which being steel, presumably is not intended to use a mech hanger and didn't come with one - (original mech was Shimano)
I have hopefully improved things by fully-screwing the screw in .. but I can see this happening again... perhaps it was careless manhandling of the bike that caused it to happen...

Since I don't have access to a friendly welder, all I can think of is epoxying some sort of wedge behind the plastic boss on the mech ... (being plastic, the coarse threaded screw doesn't immediately suggest fitting a nut on it ... and I don't have a suitable one or washers...

The mech this replaced was metal and had a fine-threaded screw with a small unthreaded spigot for a tip...

 

[beesonthewhatnow]

Fully working bikes can be found on FB marketplace for less than whatever bodge you come up with will cost.

Just sayin’…

 

[keybored]

which being steel, presumably is not intended to use a mech hanger and didn't come with one

Some steel frames (including some Ragley and at least some Blue Pigs) do indeed use a mech hanger. What year is yours?

 

[Silas Loom]

Fully working bikes can be found on FB marketplace for less than whatever bodge you come up with will cost.

Just sayin’…

The amalgamated union of bicycle thieves and fences have their own Dwyer now?

 

[gentlegreen]

Some steel frames (including some Ragley and at least some Blue Pigs) do indeed use a mech hanger. What year is yours?

It must be at least 10 years old ...
It's steel and certainly takes a mech directly and I can't see how the geometry would work..

 

[keybored]

It must be at least 10 years old ...
It's steel and certainly takes a mech directly and I can't see how the geometry would work..

2016 models onward seem to use a hanger but I don't know about older. You should try asking on singletrackworld, lots of current/former owners there. Looks like a well-liked frame so could be worth persevering with.

 

[DownwardDog]

That's not the "limit screw" it's the B-Gap Tension screw.

1. Clean everything to surgical standards so you can see what the fuck is happening.
2. Make sure the derailleur bolt is tight - 8-10Nm.
3. Measure your B-Gap. It should be ~6mm for SRAM but depending on the derailleur/cassette combination you may need the SRAM tool to get it right.

I suspect the rear derailleur has rotated and because it appears to be covered in manure and pitch it has stuck in the incorrect position.

E2A: when you buy a car I think I am going to sell my computer on Gumtree because I don't think I'll be able to handle it.

 

[Sue]

weepiper is our resident bike expert. If anyone has good advice, it's her.

 

[gentlegreen]

That's not the "limit screw" it's the B-Gap Tension screw.

1. Clean everything to surgical standards so you can see what the fuck is happening.
2. Make sure the derailleur bolt is tight - 8-10Nm.
3. Measure your B-Gap. It should be ~6mm for SRAM but depending on the derailleur/cassette combination you may need the SRAM tool to get it right.

I suspect the rear derailleur has rotated and because it appears to be covered in manure and pitch it has stuck in the incorrect position.

The mech pivots freely on the bolt, and shifting is fine with the screw where it is now ...

I've been known to use the supplied plastic guage to set the FRONT mech...
Mostly I've always done both by feel...

I've fitted quite a few mechs over the years because my riding is utilitarian and it's cheap SRAM ...

 

[weepiper]

The cheap SRAM 8 speed mech doesn't like the shape of the built in steel gear hanger. The B tension screw isn't lined up to hit the back of the hanger in the right place. Edit to add that's not to do with how far it's screwed in or out it just doesn't work very well on this frame. A Shimano Altus M310 mech would probably sit better on it because it has a differently designed back plate and screw assembly.

 

[gentlegreen]

The cheap SRAM 8 speed mech doesn't like the shape of the built in steel gear hanger. The B tension screw isn't lined up to hit the back of the hanger in the right place. Edit to add that's not to do with how far it's screwed in or out it just doesn't work very well on this frame. A Shimano Altus M310 mech would probably sit better on it because it has a differently designed back plate and screw assembly.

Thanks

I already took your advice and switched to Shimano for the front mech, but before I sacrifice the 1:1 AR, I think I'm going to try to clean it up, smear with release agent and make a mould with silicone or something and see if I can fettle an adaptor out of metal ... as a stopgap I might even just try using hot-glue to fill the gap...

I also don't want to spend any money ...

I look forward to when I'm settled elsewhere and can get a new bike - a small fleet for guests if my plans work out ...

EDIT:- I see I can at least get an Altus mech and a shifter pretty cheaply ...

 

[gentlegreen]

First attempt using a short bit of stainless steel tube...
The hot glue makes it difficult to inspect, but it's the best I can do at the moment...
If it doesn't last, I suppose I'll take the mech off and see if I can secure the tube with more precision...

 

[gentlegreen]

That fix seems to be working - and it's been working fine during 6 or 7 weeks of daily 8 mile exercise rides roughly equivalent to my old commutes.
I got it up on the stand the other day for a service and realised it also didn't like getting onto the smallest rear sprocket - it's an 8 speed mega-range but came with a 9 speed .. so I've adjusted the limit screws accordingly...(48 front, 26 inch wheels).
It doesn't seem to be cramping my style at the moment and I probably needed to pedal faster in any case.