Inquiry: Precision billet proshift derailleur bolt function

[estuche]

Hey, I have a Proshift derailleur that is missing a tiny bolt (see attached pic for example).

Anyone knows what that bolt does? Will the derailleur not work without it? If so can I remove a bolt from another location that is not essential? I assume I cannot get that online can I (already reached out to Toronto Cycles but no response yet)?

 

[ferrus]

Re:

All the bolt does is push against the end of the parallelogram-spring to increase its tension. I don't think it's important at all really.

You could probably buy a replacement online though, try searching for 'grub screws'.
But check the size, as Proshift mixed metric and imperial bolts on those mech's!

 

[estuche]

Re: Re:

All the bolt does is push against the end of the parallelogram-spring to increase its tension. I don't think it's important at all really.

You could probably buy a replacement online though, try searching for 'grub screws'.
But check the size, as Proshift mixed metric and imperial bolts on those mech's!

This is very helpful, thanks so much!!

Would I be able to measure the bolts with a caliper or is something else needed? Am I looking at length and width or something else (sorry for the rookie question)

 

[ferrus]

Re:

Ok I've measured the diameter at 3.82mm or 0.15'' - so I assume it's imperial (?)
I didn't have any imperial hex keys to hand; a 2mm removed it but was slightly loose fitting.

Personally, if you can't find a grub screw in the right size, I wouldn't worry. I've just been looking at a couple of NOS mech's and it's hardly screwed in on either of them and isn't even pushing on the spring.
Seems a fairly pointless feature to me. If a mech really needs more tension, the spring probably wants replacing - or maybe the mech just needs a good clean + lube!

 

[Graham_hkr]

3.82 = 4mm grub screw .

 

[elite504]

Re:

Yup, M4 it most certainly is.

 

[ferrus]

Re:

thank's for the correction chaps, that should be easy to find then.

I forgot to measure length: 8mm

 

[mdvineng]

Re:

It's probably there to stop the spring tang from wearing away the alloy.

 

[Graham_hkr]

Re: Re:

It's probably there to stop the spring tang from wearing away the alloy.

Yes, I'd probably screw it in until you can just feel it contact the tang then probably another quarter of a turn. might be worth putting a dab of 222 Loctite on it as well.

 

[ferrus]

Re: Re:

It's probably there to stop the spring tang from wearing away the alloy.

Wouldn't they have used a much shorter grub screw if it's just a stop? They've also machined walls about 6mm deep (and threaded) each side of the tang - presumably to keep it in place as it's pushed in by the screw.
Agree about preventing wear in the alum though - prob its most useful function!