Rear mech limit screws?

Manc33

I setup my high and low limit screws on the rear mech by just lining up the jockey wheel with the smallest and largest sprockets, without a chain on.

Once the chain was on and I had used the gears for a while, I did an accidental front shift onto the granny ring as I went from 2nd largest to largest sprocket, this made the chain come off at an angle in between the wheel and cassette. I was going really slow and stopped to see whats up, only then realizing the front shifter had shifted it down.

Then I thought is the low limit screw not quite right for the rear mech... what I found was that with a chain on I can actually screw the mech in quite a bit more before it "makes" the chain jump onto the 2nd biggest sprocket while being on the lowest gear on the shifter.

Does this mean you should adjust the limit screws WITH a chain on and don't just do it by eyesight lining it up?

Now the rear mech will only just get shifted to the biggest sprocket, whereas there was some play in it before (enough to mean an accidental front shift combined with the last upshift can make it go off at the back). That play didn;t involve it moving though, after the last click.

I know "Don't accidentally shift front and rear at the same time" lol. Think about it though, its like the full chain is all being moved to the left front and rear and it can't handle it.

Really starting to hate this triple and want a double 42/28 setup. Still gives 42x11 which on a flat bar bike not racing... I think is alright. Then I would have the luxury once more of just having a nice thumb shifter for the front mech, one way is one chainring, the other the other, always felt miles better than having a triple. I don't know why they were ever indexed or ever made a triple! Well not if we have 11-32T cassettes anyway.

If I was racing I would have that setup, a thumb shifter on a double chainset with a big spread at the back like 11-36 or something.

Ben6899

I don't quite *get* a lot of what you're discussing here, if I'm honest, but the whole premise seems to be based on the fact that you're not sure if you have the rear mech limit screws set correctly.

This explains how to do it: http://www.parktool.com/blog/repair-hel ... derailleur

trailflow

Yes you need to put the chain on. There is more tension on the spring with it on. Set it up as a guide at first without a chain.

desweller

You can't rely on eyeballing the derailleur without a load on it; you need to fit the chain. That way you can get a really precise assessment of how close the chain and cage are actually going to get to the spokes.

You should also be able to shift simultaneously at both ends without too much bother; as long as you remember to ease off until the gear shift has completed.

Nothing wrong with triples, by the way...

Manc33

The short version is, it seems after lining it up with the biggest sprocket, you can further adjust it in when a chain is on, without it making it skip to the 2nd sprocket. Thing is now its set that way, am I risking snapping the gear cable? I mean the shifter can get to its click and change up, but it and the cable feel like they are on the limit. The cable would get stretched if the limit screw wasn't able to stop it.

I am sure most problems I have are because of the gear range. :roll:

Who else has a 28-39-50 with an 11-32T?

What does bringing the jockey wheel away from the cassette do apart from make gear changes less crisp around the smaller 2 sprockets? Something funny is going on with the middle chainring and the biggest 2 sprockets. If I back the jockey wheel off in the "lowest" gear on the bike, it seems on the middle chainring the rear mech is just too "packed in" towards the cassette, its fine in the lowest gear, its the middle ring it seems the jockey wheel is too close, hence what is the bad thing about loosening that jockey wheel off more?

The worst one was when the chain was flipping on and off the biggest two sprockets, I think caused because I had the rear mechs jockey wheel setup "properly" (close to the sprocket in lowest gear).

I'm not sure it will ever be right lol. Its the bloody range on it I think. Nothing is meant to work with anything else, MTB rear mech, road chainset with even smaller 28T granny ring fitted etc etc etc.

I am really enjoying riding the thing now I am in 100% comfort on it and lost about 25lbs. Its taken months of adjusting stuff lol.

desweller

Hang on, now you seem to be talking about the B-screw, not the limit screws?

Anyway, yes you are correct ref. the bottom limit screw; the cable will be acting against the screw in the lowest gear. You are looking to find the point where you can't accidentally overshift into the wheel. Make small adjustments; 1/2 turn at a time. You won't snap the gear cable, they are very strong.

Manc33

I'm just going to leave it for now since it does click up to the biggest sprocket although the limit screw is right on the limit.

Yeah the b-tension is another issue, it seems if I set the jockey wheels close to the sprocket in the lowest gear like it is meant to be, thats all fine, but then the chain can randomly catch the 2nd biggest sprocket too soon shifting down from the biggest sprocket - when on the middle chainring. Hence that jumping from sprocket to sprocket.

Its as if the b-tension needs screwing in that little bit more just to bring the jockey wheel a few more mm away. Bringing it too far away will of course introduce more problems. I guess too far away and it wouldn't shift at all off the biggest sprocket. Also I think my rear mech hanger is some sort of "strictly road only" and they only expected road mechs to be used, hence the extra screwing in of the b-tension, meaning a double whammy. With an old mech it was unworkable even turning that screw around. My other cheap road bike had a hanger perfectly setup and I never had any of these problems. Looking at the two I can see straight away why I can never get it to cope with a 32T low sprocket. Ended up ditching the Alivio rear mech with those stupid 13T jockey wheels and replacing with XT one with 10T. That solved the b-tension-can't-screw-in-enough issue but I am still pissing about getting it setup even now. :roll:

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