Rear dual pivot caliper alignment problems

[NickNick]

I'm having real problems with my rear caliper (Tiagra dual pivot), for the last couple of weeks I will set the alignment using the screw, get it all centred properly and without fail by the time I get home one of the pads is against the rim and the other is miles off.

I've tried loosening the mounting bolt, realigning and the mounting bolt is as tight as it will go so I don't think its shifting about on the bolt (I've checked a number of times after its gone out of alignment and the nut is still rock solid).

I then thought maybe the alignment screw isn't staying in place, so I marked it up on the caliper with a fine point sharpie went for a ride and whilst the caliper was out of alignment the screw hadn't moved.

The only thing I can think of is its something to do with the brake cable outer. The frame is a Specialized Allez (from the Zert insert era) that I put together myself about a month or two ago. The outer is router round the left hand side but the bit of the caliper that the outer goes into points towards the right, could this have anything to do with it?

e2a: will get a photo up of it in the next hour or so when I can get to the camera.

 

[Ajax Bay]

Photo will make diagnosis easier but could be the outer length. Quite normal for the cable to be routed down the right side of the top tube (it makes the radius of the curve from (under tape) outer exit to the first cable stop on the top tube better) and then across to the caliper (anchored on the left). If you have that outer a bit short there may be a pull on the caliper which would cause the symptom described. With the brake lever not being operated, the ferruled cable outer should leave the cable stop horizontally (ie not up nor down) before bending round the lug. I'm guessing yours is 'down'.

 

[raleighnut]

Why not just re-centre the caliper using the screw once it has 'settled down' into position, it's all very well setting it initially at home but that doesn't take road vibration into the set-up.

 

[NickNick]

Photo will make diagnosis easier but could be the outer length. Quite normal for the cable to be routed down the right side of the top tube (it makes the radius of the curve from (under tape) outer exit to the first cable stop on the top tube better) and then across to the caliper (anchored on the left). If you have that outer a bit short there may be a pull on the caliper which would cause the symptom described. With the brake lever not being operated, the ferruled cable outer should leave the cable stop horizontally (ie not up nor down) before bending round the lug. I'm guessing yours is 'down'.

Tried to take pics that cover all angles, what do you think?

rear caliper 1

• NickNick
• 18 Nov 2017

rear caliper 2

• NickNick
• 18 Nov 2017

rear caliper 3

• NickNick
• 18 Nov 2017
• 2

Why not just re-centre the caliper using the screw once it has 'settled down' into position, it's all very well setting it initially at home but that doesn't take road vibration into the set-up.

Because it doesn't stay settled, last couple of longish rides I've been on I've stopped to align it 2-3times throughout the ride and it just doesn't stay centred. I had to realign the front one after I'd been out on the road for the first time and its stayed aligned since, so think there's definitely something not quite right with the rear one.

 

[raleighnut]

Tried to take pics that cover all angles, what do you think?

rear caliper 1

• NickNick
• 18 Nov 2017

rear caliper 2

• NickNick
• 18 Nov 2017

rear caliper 3

• NickNick
• 18 Nov 2017
• 2

Because it doesn't stay settled, last couple of longish rides I've been on I've stopped to align it 2-3times throughout the ride and it just doesn't stay centred. I had to realign the front one after I'd been out on the road for the first time and its stayed aligned since, so think there's definitely something not quite right with the rear one.

That outer is too long.

 

[NickNick]

That outer is too long.

I started with a shorter outer after reading Sheldon's site which state they should be pretty close to flat but then the inner was getting caught inside and there would be a good 5-10mm of travel on the lever before it would engage the brakes (you could pull the pads away from the rim and see the inner shifting back to its proper resting position). The bit the outer rests in on the caliper points towards the right, with a shorter outer coming from the left hand side (which afaikt is the correct side to route it from) you seem to end up with a tightness at that spot which is where I think the inner was getting caught (sorry if thats not very clear, finding it difficult to describe)

Maybe I need to get it somewhere between the two, how much shorter do you think it needs to be?

 

[raleighnut]

I started with a shorter outer after reading Sheldon's site which state they should be pretty close to flat but then the inner was getting caught inside and there would be a good 5-10mm of travel on the lever before it would engage the brakes (you could pull the pads away from the rim and see the inner shifting back to its proper resting position). The bit the outer rests in on the caliper points towards the right, with a shorter outer coming from the left hand side (which afaikt is the correct side to route it from) you seem to end up with a tightness at that spot which is where I think the inner was getting caught (sorry if thats not very clear, finding it difficult to describe)

Maybe I need to get it somewhere between the two, how much shorter do you think it needs to be?

Not much, best way is to offer it up and get a nice smooth curve then cut to that length but don't forget that where you mark it is to the bottom of the recess in the adjuster or you'll cut it too short.

 

[NickNick]

Not much, best way is to offer it up and get a nice smooth curve then cut to that length but don't forget that where you mark it is to the bottom of the recess in the adjuster or you'll cut it too short.

Luckily I bought an extra meter of outer so have some to play with! Will maybe try cutting off 5mm at a time until I reach a sweet spot. Thanks for the advice.

 

[raleighnut]

Luckily I bought an extra meter of outer so have some to play with! Will maybe try cutting off 5mm at a time until I reach a sweet spot. Thanks for the advice.

you don't need to fit the inner each time, you just need to get the gentlest curve possible on the outer.

 

[accountantpete]

That looks like an ordinary washer between the knurled locknut and the frame.

You need a serrated washer in that position to grab hold of the nut and frame to keep the brake in position. If you don't have a serrated washer then a bit of rough emery paper folded with a hole punched in it will do the job.

 

[NickNick]

Thanks for the advise @raleighnut & @Ajax Bay , have cut off 10-15mm and found a sweet spot between how I had it at first (almost completely flat) and how it was in that photo and that seems to have done the trick. Have done a couple of test rides up and down the road which is normally enough to throw the alignment out and it hasn't budged. Will put it through its paces when I go for my late night couple of hour ride tonight but its looking promising!

 

[Ajax Bay]

I hope the trial proves that the OP has solved this. I can't tell from the photos. Is the cable stop under the top tube, directly under the top tube (ie 180 degrees) or is it offset (and if so, to which side)?

 

[alecstilleyedye]

i had a rear tiagra caliper go stiff that no amount of lubricant or jet washing would free. wore a rim down on one side before i realised, and now resides in the junk pile…