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Discussion Starter · #1 ·
I just bought a Co-Motion Americano with STI shifters and Avid 203mm mechanical disk brakes. Despite repeated adjustments, the rotors rub against the disks when either wheel is spun and the brake levers are uncomfortably close to the handlebar when they are compressed to stop the wheels. My LBS agrees that this is unacceptable.

My question is this: Should I have the LBS install in-line travel agents to fix both problems or should I just revert to Durace bar end shifters and a compatible brake lever such as the Diacompe 287?

Please disregard cost for the time being. Also, I am aware of the Cannondale testing of both wound and braided cable. Thanks in advance for your opinions!
 

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Cyclesafe said:
I just bought a Co-Motion Americano with STI shifters and Avid 203mm mechanical disk brakes. Despite repeated adjustments, the rotors rub against the disks when either wheel is spun and the brake levers are uncomfortably close to the handlebar when they are compressed to stop the wheels. My LBS agrees that this is unacceptable.

My question is this: Should I have the LBS install in-line travel agents to fix both problems or should I just revert to Durace bar end shifters and a compatible brake lever such as the Diacompe 287?

Please disregard cost for the time being. Also, I am aware of the Cannondale testing of both wound and braided cable. Thanks in advance for your opinions!
Get the Avid road disc brakes. - TF
 

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Do you have the road version of the Avids?

Cyclesafe said:
I just bought a Co-Motion Americano with STI shifters and Avid 203mm mechanical disk brakes. Despite repeated adjustments, the rotors rub against the disks when either wheel is spun and the brake levers are uncomfortably close to the handlebar when they are compressed to stop the wheels. My LBS agrees that this is unacceptable.

My question is this: Should I have the LBS install in-line travel agents to fix both problems or should I just revert to Durace bar end shifters and a compatible brake lever such as the Diacompe 287?

Please disregard cost for the time being. Also, I am aware of the Cannondale testing of both wound and braided cable. Thanks in advance for your opinions!
I can't imagine Co-Motion installing the wrong brakes on your bike, but you never know. I don't think the mountain version of the Avid disc would even work with road levers (lever would probably go straight the bars before the pads even touch the rotor). The 203mm rotors can be tricky to set up if they aren't very true out of the box. I would first make sure the rotor is as straight as possible. You can look at the disc brake FAQ on MTBR for truing techniques, but I've had the best luck just using my fingers and making small bends near the spokes to straighen any hops (then cleaning the rotor with isopropyl afterwards). The larger rotors are really sensitive and don't require very much bending at all to get them straight (you typically don't have to push the rotor more than a couple of centimeters to make corrections).

Once the rotor is true, you'll want to adjust the inboard pad as close as possible to the rotor without rubbing. If the inboard pad is too far away, the brake lever will feel really mushy like you describe. In almost all cases, the rotor can be adjusted until it's silent while riding straight, but you'll still get a little zing when going into corners hard that is attributed to a small amount of axle flex. The rotor often rubs the pads so lightly that it causes neglible if any losses in speed. At most the noise is a little annoying.

I've set up quite a few sets of Avids on tandems, and I can usually get them working pretty well. The brakes will never feel as firm or have as little throw as a rim brake, because discs have a huge amount of mechanical advantage at the caliper compared to rim brakes. Even if you can pull the lever close to the bars while the bike is in the repair stand, that amount of pressure would have you sailing over the bars on a real ride. They're quite powerful and only require a light touch once the pads bed in. I haven't tried an inline travel agent with this set up, so I can't comment on that. I don't know how well those allow you to tune the cable pull ratio, but any decrease in lever throw means a decrease in mechanical advantage and thus a decrease in brake power. A brake that feels mushy is often more powerful than one with a firm feel at the lever, if set up with similar cables and housing runs. Hope that helps.

-R
 

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Discussion Starter · #5 ·
Thanks for the responses so far...

The road AVID is only available with a 160 mm rotor. I've got the mountain bike 203 mm version. I agree that Co-Motion most likely knows what it is doing. Perhaps the frame or fork cannot accommodate the former (?).

I think that my LBS has trued the rotor. I can deal with zinging while standing in the pedals, but the current rubbing is totally unacceptable. Also, I probably can get accustomed to the mushier feel, but when the brakes lock (at least on the bike stand), I have less than a cm between the brake lever and the handlebar. I am concerned that this allows little margin for wear, cable stretch, and wet conditions.

My question really is whether in your opinion the advantages of STI shifting over bar end shifting outweigh the risks of using a travel agent adapter to make the STI shifters work with Avid mechanical mountain brakes - assuming that swapping out for a Avid mechanical road 160 is not possible. I will be touring with a BOB trailer many hundreds of miles from bike shops.
 

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Cyclesafe said:
The road AVID is only available with a 160 mm rotor. I've got the mountain bike 203 mm version. I agree that Co-Motion most likely knows what it is doing. Perhaps the frame or fork cannot accommodate the former (?).

I think that my LBS has trued the rotor. I can deal with zinging while standing in the pedals, but the current rubbing is totally unacceptable. Also, I probably can get accustomed to the mushier feel, but when the brakes lock (at least on the bike stand), I have less than a cm between the brake lever and the handlebar. I am concerned that this allows little margin for wear, cable stretch, and wet conditions.

My question really is whether in your opinion the advantages of STI shifting over bar end shifting outweigh the risks of using a travel agent adapter to make the STI shifters work with Avid mechanical mountain brakes - assuming that swapping out for a Avid mechanical road 160 is not possible. I will be touring with a BOB trailer many hundreds of miles from bike shops.
Aftermarket it's only available w/ a 160mm, but a manufacturer can spec the 203mm rotor with the road caliper. I don't mean to be pedantic, but does the caliper say road on it? If you infact do have a mountain caliper, you basicallyneed a travel agent to make it work properly. The travel agents work pretty well IME. The inline one for disc brakes supposedly has less friction than the ones for V-brake/Aero lever use and should work better.

Without the travel agent, a mountain caliper and road levers gives you rediculously large amounts of leverage and mechanical advantage and correspondingly huge amounts of lever throw and mushiness. It's just like using canti-lever brake levers with V-brakes.

One other note: the road and mountain version have identical design specs, so if you want to switch the calipers to road calipers and forgo the travel agent, they will bolt right up to the current IS standard adapters you have. More expensive than travel agents, but it makes things simpler.
 

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Discussion Starter · #7 ·
Wow, making lots of progress here...

Antigravity: I am assuming that I have the full mountain version and not the road caliper with the 203 mm rotor. The bike is at the LBS and since it is Sunday, I can't call the good folks at Co-Motion.

Without the in line travel agent, the brakes work with the STI shifter except there is severe zinging caused by rubbing and the levers are compressed to about 1 cm from the handlebars. If you say that travel agents are required with mountain calipers, then maybe I have road calipers after all. That would make sense, again, because it is not likely that Co-Motion would make such a mistake.

Assuming this is true, that I have road calipers, would travel agents allow me to adjust the pad/rotor distance to eliminate rubbing, while at the same time reducing mushiness and allowing more distance between the lever and the handlebars when the lever is fully compressed?

These commemts have been most helpful and are better defining what I can do to solve my problem. Awesome!!
 

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Cyclesafe said:
Antigravity: I am assuming that I have the full mountain version and not the road caliper with the 203 mm rotor. The bike is at the LBS and since it is Sunday, I can't call the good folks at Co-Motion.

Without the in line travel agent, the brakes work with the STI shifter except there is severe zinging caused by rubbing and the levers are compressed to about 1 cm from the handlebars. If you say that travel agents are required with mountain calipers, then maybe I have road calipers after all. That would make sense, again, because it is not likely that Co-Motion would make such a mistake.

Assuming this is true, that I have road calipers, would travel agents allow me to adjust the pad/rotor distance to eliminate rubbing, while at the same time reducing mushiness and allowing more distance between the lever and the handlebars when the lever is fully compressed?

These commemts have been most helpful and are better defining what I can do to solve my problem. Awesome!!
It's more than likely that you have the road calipers, Co-Motion isn't known for making dumb mistakes like that. They're pretty meticulous with their component selection.

I haven't used a Travel Agent with a brake set up that already had compatible levers and brakes, so I don't know if this will improve the situation or make it worse. Travel agents can either be set up to increase cable pull (decrease leverage) or vice versa, but in a single step; there isn't any fine tuning for the cable pull. Using one to increase the cable pull might might make the brakes too on/off feeling with a weak amount of power.

I think something is wrong with the setup. Not trying to speak ill of your LBS, but the setup of discs and road levers might need some more work as it can be real finicky. Housing runs that are too long will flex and make the brakes feel mushier; housing should be as short as possible and only long enough to allow complete rotation of the handlebars in the event of a crash. It's also a good idea to grind the housing so that it is nice and square after cutting it (with a bench grinder or Dremel tool). Again, it's very important to have the fixed inboard pad as close as possible to the rotor; as much as a couple clicks too far out can make a substantial difference in lever throw and firmness. Every so often as the pads wear you will also have to adjust the pad inward to maintain the same lever throw.

If the brakes can't be adjusted any better, then give the Travel Agents a try and let us know if/how they work. I'd be interested to know.
 

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Discussion Starter · #9 ·
Co-Motion Rocks!

Co-Motion confirmed that the calipers are indeed road calipers, even though the rotors are 203mm. They also said that the rubbing is due to a combination of a need to break in the brakes and further adjustments of the system and that the bottoming out of the levers could be a matter of adjustment. In-line travel agents may help this problem, but they will reduce the mechanical advantage on the brakes, perhaps to the point of reducing their effectiveness. Anyway, Co-Motion will coordinate with the mechanics at the LBS to ensure that all bases are covered. I really can't imagine that aftermarket fixes will be required to make a Co-Motion safe to ride. Will keep you posted.
 

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Discussion Starter · #10 ·
Alls well that ends well.

Finally accepted delivery on the Americano with STI's and Avid disk road brakes. What was required for the system to work were stiffer brake cable housings. The brakes now work like a dream. And no Travel Agent or Brake Power Booster was needed.

Thanks to Antigravity for his advice!
 

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Cyclesafe said:
What was required for the system to work were stiffer brake cable housings. The brakes now work like a dream. And no Travel Agent or Brake Power Booster was needed.
Do you have any specifics about the brake cable housing?
 

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Discussion Starter · #12 ·
Sorry. Other than being slightly thicker and stiffer than my derailleur housings, I can't say much about how they differ from the originals. The LBS wasn't specific about what they did to make things right and I was just happy to get my ride (after waiting three months) that I didn't quiz them on it.
 
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