# L & H screws on derailleur



## fa66ster (20 Mar 2010)

Hi,

I have replaced cables on my bike recently and having difficulty getting the gears to operate smoothly, I was wondering what the L & H screws to the crank and rear derailleur do - are they fine tuning?

Cheers


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## Steve Austin (20 Mar 2010)

They are to adjust the end ranges of the mechs.

If you have just replaced the cables, then it is extremely unlikely to need to adjust the L/H stops to get the adjustment right


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## fa66ster (20 Mar 2010)

Steve Austin said:


> They are to adjust the end ranges of the mechs.
> 
> If you have just replaced the cables, then it is extremely unlikely to need to adjust the L/H stops to get the adjustment right



End ranges??


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## PatrickPending (20 Mar 2010)

fa66ster said:


> End ranges??




they govern how far the mech will swing to the left of right. If not set correctly they could prevent you from using cogs or allow you to miss the cog completely and throew the chain.

As steve said unlikely to need adjusting when replacing cable


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## Moodyman (20 Mar 2010)

Try fine tuning using the barrel adjuster on either the handlebar shifters or on the rear derailleur.

If that don't work, make sure you've got the right tension in your cable i.e. enough pulled out of the bolt that fastens it to the derailleur.

There's no easy rule - it's trial and error and bl88dy frustrating.


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## 2Loose (20 Mar 2010)

I found this article particularly clear and helpful on how to adjust your rear mech.

http://www.nsmb.com/2923-adjust-your-rear-derailleur


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## fa66ster (21 Mar 2010)

thx 2loose


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## 02GF74 (22 Mar 2010)

the L afjuster - determines how far past the big sprocket the mech cna move the chain.

get this adjustment wrong and the chain will get thrown past the sprocket into the gap between it and the spokes. this can result in spoke damage and the chain can get wound round pulling the mech off - not good things to have to deal with on a ride (assumes you do not have the plastic spoke protector fitted).


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## fa66ster (22 Mar 2010)

Is it conceivable that the front derailleur could be the wrong one on the bike?

It appears that no matter what adjustment I do the front derailleur (3 cogs) won't get down to the smallest cog with or without the cable attached!


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## PpPete (22 Mar 2010)

There are some front derailleur mechanisms that seem not to pull in far enough to get on to the granny ring. Or it gets there when bike is on the work-stand, but not on the road.

Did it work OK before you changed the cables?

If not, then either the mech isn't triple compatible, or maybe is triple but isn't compatible with your frame, or the BB isn't the right length.

You can sometimes get round it by adjusting the position of the BB a millimetre or so. Wind the RH BB cup clockwise (assuming English thread), then the LH cup (also clockwise to take up the slack)


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## fa66ster (22 Mar 2010)

porkypete said:


> There are some front derailleur mechanisms that seem not to pull in far enough to get on to the granny ring. Or it gets there when bike is on the work-stand, but not on the road.
> 
> Did it work OK before you changed the cables?
> 
> ...



I bought the bike with the set-up, I figured a bit of tweaking was all that was required as it wasn't changing down immediately but I guess it may not be triple after all!

What's BB?


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## shouldbeinbed (22 Mar 2010)

Front Mech then.

It's not just sticky is it, after all the crud of this winter and the roads generally, it doesn't take much to get bother with a bit of grit. Have you deluged it with degreaser, given it a good lube and worked it by hand to get oil into all the moving parts.

you could get someone to shift the gears whilst you get up close and personal with torch to make sure theres not something catching or displaced in there.

worn out or too weak spring?

Could it be that the actual derailleur is set in the wrong place on the tube? if you look from above does the guide cage look parallel to the chain? You could try lowering it down the tube a few mm and/or rotating it round a fraction.


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## PpPete (22 Mar 2010)

BB = Bottom Bracket

Strange name really - it's basically the axle that goes through the frame, and on to which the cranks/chainwheel assembly are attached.
Old style ones had a solid axle, bearings and cups that threaded in each side of the frame. Really really old one had an "axle" with one flat on the side and the cranks were held on with cotter pins. More recent "cotterless" ones have a tapered square end with either a threaded stud or threaded hole onto/into which crank retaining bolt/nut threaded. Example.

Newer ones still have integrated bearings, and come in several flavours, basically square taper (either JIS or ISO) , splined types like this. But beware there are also different threads and lengths of spindle...

Latest iteration is outboard bearings, unlikely you have those.


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## fa66ster (22 Mar 2010)

The cage is parallel to the chain yes. When shifting from 3 to 2 there is an obvious cage movement, however when shifting 2 to 1 the cage does not appear to attempt to move! I have degreased the spring and given it a good lube. I am inclined to think I don't have the correct derailleur on the bike.

When buying what does dual-pull mean? What should I be looking out for for my bike?

Cheers guys!


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## fido (29 Mar 2010)

I could be that you've pulled to much cable through making it too short. This with render it unable to release enough tension to change down.


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