Twist grip gear changer on front deraileur

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johnk1
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Twist grip gear changer on front deraileur

Postby johnk1 » 11 Jan 2019, 11:17am

I have a twist grip changer on the front derailleur. It is OK going down the gears but very stiff coming back up, any idea why?

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NATURAL ANKLING
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Re: Twist grip gear changer on front deraileur

Postby NATURAL ANKLING » 11 Jan 2019, 11:31am

Hi,
Cable is a good place to start.
Pull the exposed cable that runs down the frame tube with fingers to see the Mech runs free?
Twist grip on front changers are particularly hard to operate generally.
Expose the cable that is hidden and slide the outer cable out of the way by disconnecting the outer cable ends from frame and examine the hidden inner cable for rust / dry appearance, lack of lubrication.
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alexnharvey
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Re: Twist grip gear changer on front deraileur

Postby alexnharvey » 11 Jan 2019, 11:32am

Springs, gravity, leverage and cable lubrication.

That is, when shifting up you are pulling against the derailleur spring and literally pushing the chain against and up the chainring.

When shifting down the spring and gravity both help, once nudged off the chain falls and the spring is now pulling the derailleur back to its next index point or final resting position.

It's always harder going up than down. A worn and or poorly lubricated cable makes it more difficult both directions but on the downshift you have help and on the upshift, hindrance from the spring and gravity.

With a grip shifter you don't have the leverage a shift lever provides. It's still harder to go up than down though on all shifter types.

johnk1
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Re: Twist grip gear changer on front deraileur

Postby johnk1 » 11 Jan 2019, 1:05pm

Thanks for that, I'll check the cables, is a weaker spring an option?

alexnharvey
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Re: Twist grip gear changer on front deraileur

Postby alexnharvey » 11 Jan 2019, 1:17pm

I don't think so. Certainly not without a change of derailleur as far as I know. It's possible there's some variation in spring strength between derailleurs. I've never seen it discussed or rated.

I would expect that as natural ankling said, cable replacement and or lubrication will be helpful in minimising the force required to upshift, as will ensuring optimal adjustment of the front derailleur in relation to the chainrings.

peetee
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Re: Twist grip gear changer on front deraileur

Postby peetee » 11 Jan 2019, 5:19pm

NATURAL ANKLING wrote:Hi,
Cable is a good place to start.
Pull the exposed cable that runs down the frame tube with fingers to see the Mech runs free?
Twist grip on front changers are particularly hard to operate generally.
Expose the cable that is hidden and slide the outer cable out of the way by disconnecting the outer cable ends from frame and examine the hidden inner cable for rust / dry appearance, lack of lubrication.


+1
Also check the outer cable strands are safely encased in the plastic sheath and have not pushed through the end caps.
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iandriver
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Re: Twist grip gear changer on front deraileur

Postby iandriver » 11 Jan 2019, 6:53pm

It's surprisingly easy to attach the cable to the wrong side of the bolt on some front mechs. It can make shifting hard in a way you wouldn't believe. You don't say if this has happened suddenly, or gradually. A little more info on the mech model and how the problem came about might help. Perhaps a picture if you can.
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johnk1
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Re: Twist grip gear changer on front deraileur

Postby johnk1 » 11 Jan 2019, 8:05pm

I was given the bike by my neighbour, it's been in his garage for years. I sorted out the rear derailleurs and still have to do the brakes. I'll have a look at which side of the bolt the cable is, I assume the straighter it runs the better.

MikeF
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Re: Twist grip gear changer on front deraileur

Postby MikeF » 11 Jan 2019, 10:44pm

As above. When you change down you slacken the cable which is obviously quite easy to do. When you change up you tighten and pull the cable against a spring and the chain, which is obviously much harder.
"It takes a genius to spot the obvious" - my old physics master

peetee
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Re: Twist grip gear changer on front deraileur

Postby peetee » 11 Jan 2019, 10:59pm

johnk1 wrote:I was given the bike by my neighbour, it's been in his garage for years. I sorted out the rear derailleurs and still have to do the brakes. I'll have a look at which side of the bolt the cable is, I assume the straighter it runs the better.


There are different designs of front mech and the cable attaches a particular way for each. We really need a photo to give sound advice.

Cable and pitch bolt aside a drop of oil on each of the mech pivots helps.

Don't expect the front mech to be as easy to operate as the rear. In almost every case the effort required is approx double.
Current status report:
Latter side of fifty and feeling less than nifty.
Too many bikes on pegs and too few miles in the legs.

johnk1
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Re: Twist grip gear changer on front deraileur

Postby johnk1 » 13 Jan 2019, 10:50am

DSCN2816.JPG
Here's a couple of photos. It looks like the cable should be clamped the other way round as it would give a straighter pull. The photo is in the middle gear position. Sorry, I can't get the photo to rotate.
DSCN2816.JPG
DSCN2816.JPG

johnk1
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Re: Twist grip gear changer on front deraileur

Postby johnk1 » 13 Jan 2019, 10:54am

Here's another shot the first 3 are all the same, that was through trying to rotate the image
DSCN2815.JPG

Brucey
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Re: Twist grip gear changer on front deraileur

Postby Brucey » 13 Jan 2019, 11:53am

IME that FD with a typical twist grip shifter will often be hard work anyway (*), but cables that are lacking quality/lubrication will always make it worse. The cable route appears to be correct in the mech; the cable ought to go to the right of a tab near the pinch bolt and it is as far as I can see. A shot from the rear would make this clearer.

(*) IIRC the 'correct' shimano twist type shifter that goes with that mech has some kind of fancy gearing in it so that the FD shift isn't too heavy. Unfortunately the whole thing is made very cheaply in plastic and it isn't 100% reliable. A simpler grip shifter (without the internal gearing) will make the shift about twice as heavy.

IME the most simple/satisfactory shifter to use with a mech like that is a basic thumbshifter. If the shift was still too heavy once I'd had a go at the cables (which are likely to be terrible as the bike appears to be a basic FS MTB which will involve lots of short lengths of cable housing, each of which lets the water in etc) then I'd probably fit a thumbshifter.

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johnk1
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Re: Twist grip gear changer on front deraileur

Postby johnk1 » 13 Jan 2019, 5:29pm

Thanks Brucie, I'll try and get a shot from the rear. I will lubricate all the cables as they're probably bone dry by now if they were ever oiled.

LittleGreyCat
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Re: Twist grip gear changer on front deraileur

Postby LittleGreyCat » 13 Jan 2019, 5:59pm

The other thing you could do (if your hands are big enough) is increase the diameter of the left hand grip so you get more leverage.

Similar to the principle of winding a towel round a Prosecco cork to get more grip and leverage.