Adjusting front mechs
- Thread starter Alison
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scottproonly
Retro Guru
Re:
I always use friction on the front mech as front indexing means you usually end up with chain rub. As I understand it,you can trim the front mech on road bikes so why don't they give you that option on mtbs?
Kes
I always use friction on the front mech as front indexing means you usually end up with chain rub. As I understand it,you can trim the front mech on road bikes so why don't they give you that option on mtbs?
Kes
I've found, with mid-90's front mechs, at least, on 7 and 8 speed bikes, the cage is wide enough usually to allow rub-free running in all but the extreme combos.... For instance
In granny, it can be set up so it only rubs in small-small - which you should avoid anyway. In the middle ring, it'll typically rub only in the largest and smallest cogs, which I take as a signal that it's time for a different chainring. In the large, I trim it to not rub in the smallest cog, which means it will rub in the largest 1 or 2 cogs, again a combo to be avoided.
As always this assumes a good chainline and proper mech location, and matching the mech to the chainrings. The shorter the bike's chainstay, the harder it will be to achieve good FD setup, as the chainlines are less ideal in crossed situations.
I do wish the front shifters in MTB had the half-clicks for trimming, like my wife's 105's. No idea why they don't.
J
In granny, it can be set up so it only rubs in small-small - which you should avoid anyway. In the middle ring, it'll typically rub only in the largest and smallest cogs, which I take as a signal that it's time for a different chainring. In the large, I trim it to not rub in the smallest cog, which means it will rub in the largest 1 or 2 cogs, again a combo to be avoided.
As always this assumes a good chainline and proper mech location, and matching the mech to the chainrings. The shorter the bike's chainstay, the harder it will be to achieve good FD setup, as the chainlines are less ideal in crossed situations.
I do wish the front shifters in MTB had the half-clicks for trimming, like my wife's 105's. No idea why they don't.
J
michael franks
Retrobike Rider
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FSXStumpy wrote:
Some of the SRT type Gripshifts have several clicks on the front mech shifter.
Some of the SRT type Gripshifts have several clicks on the front mech shifter.
True, that, but I've found vintage Gripshift, which I rather liked BITD, to be rather brittle now, subject to cracking rather easily. ISTR about 3 clicks per 'ring on my old gripshift... My son's little 20" bike has 6 clicks between granny and middle ring (Shimano Revoshift). But that's not a great solution for real riding (cheap, low quality shifter, IMHO).
J
J
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Lots of Shimano mtb front shifters had a trim function.
I put together an FD-310 with a Shimano M570 shifter - the bloody thing was set exactly! I was not expecting that.
I put together an FD-310 with a Shimano M570 shifter - the bloody thing was set exactly! I was not expecting that.
We_are_Stevo
Old School Grand Master
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Re:
So long as the axle isn't too wide, so putting the mech. out of adjustment range, the setup should be fairly straight forward:
I always do mine by line of sight BEFORE fitting the chain: put the band round the seat tube and push the mech. cage across with your fingers to make sure it clears the outer chain ring by 1-3mm. Adjust until it does then nip up the clamp bolt.
Depending on the mech. the alignment of the outer cage is either parallel to the outer chainring, or the inner cage slightly toed in at the front. tighten the clamp bolt.
As the mech. automatically springs to the granny ring, adjusting the limit screw is easy - centre the cage on the granny ring.
Now push the cage across to the outer ring and adjust the limit screw so it will only go so far as to centre on the ring again.
Now fit your cable: I start with the shifter adjuster in the middle of its travel. pull the cable tight through the bolt on the mech. and tighten. Try the lever op. and sight it to make sure it looks 'right.'
NOW fit the chain for sizing: All the way round biggest ring/cog, not through the rear mech., plus two links - or one link and a speed link.
Fit the chain...
The next bit is easiest done with two people: get someone to hold the rear wheel off the ground by the saddle so you can turn the pedals by hand and work the shifter. Run the mech./chain across the rings (best to use the middle cog at the back) and adjust the limit screws if necessary to drop it onto the granny and push it onto the outer smoothly; get these two right and the shifter will take care of the middle ring
I've always followed this process, and I very often don't have to make ANY adjustments after fitting the chain...
...it's like everything else (apart from REAL rocket science I guess, and brain surgery, and...), there's no 'dark art' to it, just following a few instructions and a bit of practice.
Don't let your mind beat you before you even start...
...unless you have Alzheimers, in which case the answers to your original questions are 'Cheese on toast,' 'The red wooly ones,' and '1964'
So long as the axle isn't too wide, so putting the mech. out of adjustment range, the setup should be fairly straight forward:
I always do mine by line of sight BEFORE fitting the chain: put the band round the seat tube and push the mech. cage across with your fingers to make sure it clears the outer chain ring by 1-3mm. Adjust until it does then nip up the clamp bolt.
Depending on the mech. the alignment of the outer cage is either parallel to the outer chainring, or the inner cage slightly toed in at the front. tighten the clamp bolt.
As the mech. automatically springs to the granny ring, adjusting the limit screw is easy - centre the cage on the granny ring.
Now push the cage across to the outer ring and adjust the limit screw so it will only go so far as to centre on the ring again.
Now fit your cable: I start with the shifter adjuster in the middle of its travel. pull the cable tight through the bolt on the mech. and tighten. Try the lever op. and sight it to make sure it looks 'right.'
NOW fit the chain for sizing: All the way round biggest ring/cog, not through the rear mech., plus two links - or one link and a speed link.
Fit the chain...
The next bit is easiest done with two people: get someone to hold the rear wheel off the ground by the saddle so you can turn the pedals by hand and work the shifter. Run the mech./chain across the rings (best to use the middle cog at the back) and adjust the limit screws if necessary to drop it onto the granny and push it onto the outer smoothly; get these two right and the shifter will take care of the middle ring
I've always followed this process, and I very often don't have to make ANY adjustments after fitting the chain...
...it's like everything else (apart from REAL rocket science I guess, and brain surgery, and...), there's no 'dark art' to it, just following a few instructions and a bit of practice.
Don't let your mind beat you before you even start...
...unless you have Alzheimers, in which case the answers to your original questions are 'Cheese on toast,' 'The red wooly ones,' and '1964'
Re: Re:
wow - all that knowledge/experience, and you still haven't discovered the beauty of a bike work-stand ... ??
We_are_Stevo":1b4v942b said:The next bit is easiest done with two people: get someone to hold the rear wheel off the ground by the saddle so you can turn the pedals by hand and work the shifter.
wow - all that knowledge/experience, and you still haven't discovered the beauty of a bike work-stand ... ??
We_are_Stevo
Old School Grand Master
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Re: Re:
I have one, but I wasn't going to automatically make the assumption that someone needing a 'walk through' would...
...the original post was a request for guidance on something they have difficulty with: something that is actually quite easy if you approach it the right way, and sometimes all it takes is a little effort on the part of those of us who DO find it piss easy to pass that knowledge on.
Yes?
k-rod":1v74e5q6 said:We_are_Stevo":1v74e5q6 said:The next bit is easiest done with two people: get someone to hold the rear wheel off the ground by the saddle so you can turn the pedals by hand and work the shifter.
wow - all that knowledge/experience, and you still haven't discovered the beauty of a bike work-stand ... ??
I have one, but I wasn't going to automatically make the assumption that someone needing a 'walk through' would...
...the original post was a request for guidance on something they have difficulty with: something that is actually quite easy if you approach it the right way, and sometimes all it takes is a little effort on the part of those of us who DO find it piss easy to pass that knowledge on.
Yes?
