B Tension Bolt Missing

bill_gates

When fettling tonight I realised that my rear Shimano 105 derailleur has no b-tension bolt. It originally existed as I recall it being a pretty long bolt. I've no idea when this has either been removed or worked loose.

Any idea if this is totally necessary, I'm not totally aware of that much performance issues although my gear changes can always be a little temperamental.

ForumNewbie

It's a way of ensuring the top jockey wheel is not too near the sprockets, so I would try and find a replacement screw.

ugo.santalucia

It's quite simple... if your derailleur works fine without one, then you don't need it. If it doesn't, then you need it.

In 20 years of playing with rear derailleurs from the 1950s to the most recent ones, I can't say I've ever come across a problem that I could solve with the B screw.
It's a bit like those tiny hexagonal bolts that are supposed to adjust the brake caliper arms, but in reality don't do anything

bill_gates

I think the rear mech is working although it feels like it almost needs some finer tuning which I can't seem to get with the barrel adjuster or H L screws.

chris_bass

ugo.santalucia wrote:

It's quite simple... if your derailleur works fine without one, then you don't need it. If it doesn't, then you need it.

In 20 years of playing with rear derailleurs from the 1950s to the most recent ones, I can't say I've ever come across a problem that I could solve with the B screw.
It's a bit like those tiny hexagonal bolts that are supposed to adjust the brake caliper arms, but in reality don't do anything

Whilst I can't claim to have been adjusting rear mechs for 20 years, I completely agree, I can screw the B limit screw all the way in or out or anywhere in between and it will have no impact on how well the gears change.

chris_bass

Bill Gates wrote:

I think the rear mech is working although it feels like it almost needs some finer tuning which I can't seem to get with the barrel adjuster or H L screws.

the H and L screws only affect the extremes so would not affect shifting except for the highest and lowest gears.

I would suggest changing the gear cables and outers to see if that helps. Depending on how old/clean your chain and cassette are these may also be causing issues.

bill_gates

Its a new chain and not a new cassette so thats my next bit of fettling. I done a quick run tonight and rear chainging was not too bad.