Does the b-tension spring pull the upper jockey wheel...

[Manc33]

On the older Shimano rear MTB mechs with a sprung b-tension, does the b-tension spring pull the upper jockey wheel away from the cassette (can't see that lol) or does that spring pull the upper jockey wheel towards the cassette?

If you grab a mech on a bike and turn it it can only rotate clockwise away from the cassette and is sprung that way (so it wants to spring anti clockwise towards the cassette) so it seems the b-tension spring is holding the mech... tucked into the cassette?

So if that spring were to be relaxed (drilling a hole in the b-tension washer to make the spring relaxed a bit) the upper jockey wheel might then clear the largest sprocket?

I am already using a reversed allen head bolt in my b-tension. That spring can alleviate it I reckon but do I make it stronger or weaker? Its the M952 on a 34t and is known for not clearing the 34t in the lowest gear, been mooching around for ages trying to find out if the spring needs weakening or tightening.

[Brucey]

if you take a few minutes with a mech that is mounted but without a chain fitted, it is very clear that the B tension spring is pushing the mech CW (as viewed from the right side).

Thus to clear larger sprockets the B tension needs to be increased, not decreased.

cheers

[Manc33]

if you take a few minutes with a mech that is mounted but without a chain fitted, it is very clear that the B tension spring is pushing the mech CW (as viewed from the right side).

Thus to clear larger sprockets the B tension needs to be increased, not decreased.

cheers

Sorry Brucey I wasn't thinking of it that way, yes it rests on a bike "folded up backwards" without a chain on.

If B-tension force is applied CCW to a mech under no tension (to pull the upper jockey wheel into the sprockets) then the upper jockey wheel wants to be pulled away by the b-tension.

Then maybe I can get away with having a normal b-tension screw in and the right way around but its wishful thinking.

Cheers Brucey.

[Manc33]

Drilled a hole about 3.5mm to 4 mm around from the other hole on the b-tension washer (2mm diameter drill bit).

The spring went back in under more tension as intended and it worked to great effect.

Its an old mech and I could tell the last bit of tension wasn't there much in the spring on the original hole, which explains why it couldn't spring the mech away from the low sprocket - as Brucey has already explained, its relying on the weaker/first part of the spring tension when the mech is in that position.

Now after modifying it, in the lowest gear it easily clears the 34t.

It clears the 34t with only about 4 threads of the b-tension screw screwed in and at last it has a normal Shimano screw in the right way round.

None of the shifting has been affected down the smaller sprockets either. Now it would probably even work on a 36t but I don't want those gear jumps (on 9-speed).