Fitting A New Front Mech. How Do You Set The Height And Rotation With Only Two Hands?

Lovacott

Über Member
So you've got the height right using the supplied guide but now you need to set the rotation by looking down from above (or underneath if you are working with your bike on its head).

So you loosen the clamp bolt, adjust the rotation and at the same time, alter the height without meaning to.

So you loosen the clamp bolt, re-set the height and bugger up the rotation without meaning to.

After an hour of buggering about this morning, I got fed up and had a dig in my toolbox where I found an old jubilee clip. I fixed it under the mech clamp once I'd got the height right.

I was then able to loosen the mech clamp and concentrate on the rotation without worrying about the mech sliding down the seatpost by a millimetre or two.

Are there other ways around this?
 

Ming the Merciless

There is no mercy
Location
Inside my skull
When height is right put a bit of electrical tape on seat tube below clamp. Also only undo clamp enough to rotate , not so much that it freely rotates or drops.
 

Sharky

Guru
Location
Kent
So you've got the height right using the supplied guide but now you need to set the rotation by looking down from above (or underneath if you are working with your bike on its head).

So you loosen the clamp bolt, adjust the rotation and at the same time, alter the height without meaning to.

So you loosen the clamp bolt, re-set the height and bugger up the rotation without meaning to.

After an hour of buggering about this morning, I got fed up and had a dig in my toolbox where I found an old jubilee clip. I fixed it under the mech clamp once I'd got the height right.

I was then able to loosen the mech clamp and concentrate on the rotation without worrying about the mech sliding down the seatpost by a millimetre or two.

Are there other ways around this?
Think I must have made the right decision when I changed to 1x10 gearing.
 
OP
Lovacott

Lovacott

Über Member
When height is right put a bit of electrical tape on seat tube below clamp. Also only undo clamp enough to rotate , not so much that it freely rotates or drops.
I tried the tape thing to start with but the mech would still move down a bit when I was doing the rotation. Maybe the tape wasn't thick enough?

The jubilee clip worked very well though.

Just trying to sort the indexing now. Brand new chain as well.

Hesitates a bit going from the big ring to the middle ring but the change from middle to small is sweet.

The changes up the rings are pretty much perfect.

I'll take it for a test ride in the morning and no doubt be back on here afterwards asking even more questions.

😄😄😄
 
OP
Lovacott

Lovacott

Über Member
Think I must have made the right decision when I changed to 1x10 gearing.
I won't be bothering with a three front ring setup again. My old Raleigh ten speed (2 x 5) never gave me any trouble after years of commuting and indexing was a piece of piss.
 

Ming the Merciless

There is no mercy
Location
Inside my skull
I tried the tape thing to start with but the mech would still move down a bit when I was doing the rotation. Maybe the tape wasn't thick enough?

The jubilee clip worked very well though.

Just trying to sort the indexing now. Brand new chain as well.

Hesitates a bit going from the big ring to the middle ring but the change from middle to small is sweet.

The changes up the rings are pretty much perfect.

I'll take it for a test ride in the morning and no doubt be back on here afterwards asking even more questions.

😄😄😄
The tape was to mark the correct height, so you can get it right if necessary as you retighten.
 
OP
Lovacott

Lovacott

Über Member
The tape was to mark the correct height, so you can get it right if necessary as you retighten.
The problem I had was that alignment is done from the top whilst spacing is done from the side so you can't see both at the same time. When you adjust one, you risk throwing out the other.

I've got past that bit now and I am now at the point of thinking I have it as perfect as I could get it.

I get a very slight rub at certain points of rotation in the naughty gears, but it is literally a very slight rub. Maybe a less than perfectly lined up crank?

I should point out though, that I have installed a brand new chain and I have not oiled anything yet so any contact is going to be noisy.

I would assume that the mech and chain will wear in and take out these minor contacts?
 
OP
Lovacott

Lovacott

Über Member
In that case the tape could had been placed aligned to top of clamp so you can see both. But if you don’t unduly loosen the clamp you can turn it without it dropping down seat tube.
I was finding that if I loosened off the clamp bolt enough to adjust alignment, It was also enough to cause half a millimetre of travel up or down.

Now I've done it once, it will probably be easier next time around.
 
Last edited:
OP
Lovacott

Lovacott

Über Member
Half a mm will not matter in function. A derailleur does not need to be that precisely fitted.
I find that with the triple up front, tiny adjustments make a difference.

A half millimetre drop down in the clamp height caused the inner rail to skim on the middle ring when shifting up to the large ring. Half a millimetre too high and shifting down was slow. I used the height alignment tape fitted to the mech to set the height and I have to say that Shimano have got it bang on. If you get the alignment right, the rest is easy.

One thing I have learned today is to set up the new mech with the old cable. The number of times I've had to clamp up the cable and then unclamp again whilst setting and then checking the height and alignment isn't good for a cable so it's better to do it with the old one.

Now I've got the mech alignment and stops set properly, I can swap out the cable for a brand new one and once it's bedded in, hopefully I can forget about indexing gears for a month or two?
 

Paulus

Started young, and still going.
Location
Barnet,
So you've got the height right using the supplied guide but now you need to set the rotation by looking down from above (or underneath if you are working with your bike on its head).

So you loosen the clamp bolt, adjust the rotation and at the same time, alter the height without meaning to.

So you loosen the clamp bolt, re-set the height and bugger up the rotation without meaning to.

After an hour of buggering about this morning, I got fed up and had a dig in my toolbox where I found an old jubilee clip. I fixed it under the mech clamp once I'd got the height right.

I was then able to loosen the mech clamp and concentrate on the rotation without worrying about the mech sliding down the seatpost by a millimetre or two.

Are there other ways around this?
Sounds like you are loosening the clamp too much.
Just slacken the clamp enough so you can rotate it, having first put some tape on the tube to mark the correct position.
 
  • Like
Reactions: C R
OP
Lovacott

Lovacott

Über Member
Sounds like you are loosening the clamp too much.
Just slacken the clamp enough so you can rotate it, having first put some tape on the tube to mark the correct position.
I used electrical tape and only loosened the clamp enough so that it would rotate with a firm twist. I must have been a bit ham fisted.

I ended up putting a jubilee clip underneath the clamp once I got the height right. It made setting the rotation easy.
 
Top Bottom