WPH

My 2006 Fuji tandem came with flat bars, 8sp triple and Tektro v-brakes, which worked very well. But I ride that bike a lot with my son and I changed to drop bars and used Ultegra 9sp STI brifters. Brilliant cheap conversion and the gears worked perfectly from the get go.

I got Travel Agents to correct the cable pull so that the v-brakes would work with the roadbike levers. Functionally the Travel Agents have been fine, even the setup process wasn't horrible. But the front brake squealed a lot, I imagine because the addition of the Travel Agent made a long lever even longer and much more prone to those high pitch high frequency vibrations, and because on a tandem the front brake is subject to some particular stresses.

I decided I needed to try cantilever brakes on this bike to get rid of the squeal. I've worked on lots of cantis over the years, they are always a bit fiddly to configure but I have been satisfied with their performance. I am familiar with the Sheldon Brown information.

Now I've installed Tektro CR720 cantilever brakes - on the front only so far. These particular brakes are quite nice out of the box. I was happy with the braking on my test ride: no squealing, right amount of travel at the lever etc. But in order to get the pads to contact the rim at the same moment I've had to set the straddle wire off-center - see the picture below.

My question is: how do I get that straddle wire centred? I've read thru a bunch of threads here on BF and have already tried putting the NDS spring in the top hole on the fork boss but it was just too stiff. Then I tried putting the DS spring in the bottom boss hole but it was just too weak. The middle holes are recommended by Tektro and work best for return and resistance at the lever. I have also wound the adjuster screws in and out as shown in the instructions but the calipers are so off-centre it made no difference.

Advice welcome.

huka

This could be due to your front cable stop didn't align properly to front tire

Paramount1973 

You can also try swapping positions of the thicker concave washer for the thinner one on one brake pad.

WPH

The cable stop is centred over the tire. You can see from the picture that the main brake cable starts in the middle (at the top) and heads off to the left. Alignment of the cable stop is simple - it's a threadless stem, the hanger slides onto the steerer above the headset and below the stem.


W

cycle_maven

Wheel doesn't look centered in the fork. Fix that first- check that the wheel is all the way down in the dropouts, if it is, check for wheel dish, if the wheel is dished well, then check for fork alignment. If the fork is aligned, then you can file the dropout on the short side by a fraction of a mm to get the wheel centered.

You'll find that the brakes are a lot easier to center then.

Barrettscv 

I would install a Tektro brake cable hanger on the fork. It will improve the accuracy of the cable run. It will also improve the braking performance and reduce shudder. See: Tektro Brake Cable hanger, frame mount

You can adjust the spring tension on each arm, that will provide some fine tuning once everything else is corrected.

I have a fork mounted hanger on two of my bikes: I'm using a Tektro Front Cable Hanger like this on my all-carbon fork from Pedal Force along with CR-720: Amazon.com : Tektro Front Cable Hanger Black Canti Fork Mount : Bike Shift Cables And Housing : Sports & Outdoors



And an Origin 8 Front Cable Hanger (made by Tektro) on my steel Surly fork: Amazon.com : ORIGIN8 Brake Hole Mount Cable Hanger : Bike Brake Accessories : Sports & Outdoors

WPH

Thanks for all your input.

The wheel is definitely centred - don't be fooled by the mudguard/fender.

I have a fork-top hanger which I might try. Will mean changing the front cable outer = re-taping the bars = a drag. And I don't think it will fix this issue.

Based on other reading I think the underlying problem here is that the spring tension is uneven so I am gonna bend the spring a bit with pliers first.

W