wad06

Let me say that this forum was invaluable for choosing a bike, and I have enjoyed reading people's threads about their rides and goals.

That said, I am still a very noobish bike rider. I have a Cannondale System6 with a Ksyrium ES wheelset. The brakes have been upgraded to zero-gravity brakes (I have no idea what this mean, I bought it used, and this is what I was told). Anyway, I have never done any bike maintenance, but I don't think I've ever had the need before (this is my first season, and a tune-up was done prior to purchase).

Anyway, for the first time, I decided to drive somewhere to go for a ride - I have been just going out the front door. To fit the bike in my car, I took both wheels off. When I put them back on, I noticed that the brake pads were hitting the wheels at different times (left before right on the front wheel and the opposite on the rear wheel). So, being the idiot I am, I starting toying around, trying to fix this problem myself. After untightening and retightening lots of screws with my allen tool, I've made things worse, and I am at a loss for what to do now.

At this point, the front brake pad is constantly touching the wheel on one side and the entire brake refuses to stay centered. When I nudge it over, it goes right back. The rear brake has the same problem, but now doesn't touch the wheel hard enough to stop it.

Also, there is a little lever on each brake that I can move with my fingers to point either up or down. Which way do I want it pointing?

I know, I know, I'm an idiot. But, even knowing that, I'd appreciate any advice.

Oh, and I also noticed that the center screw on the rear brake is easy to loosen or tighten, while the center screw on the front is much harder to turn either way and is squeeking when I try to turn it. I don't know if I should even be playing with that screw.

Thanks a million,

Wad

idcruiserman

I'm not familiar with those brakes, but they should operate like any other dual-pivot caliper type. The center bolt mounts the caliper to the fork/frame, and once it's in place and tight, leave it alone. The lever is for opening the caliper when removing the wheel. It should be pointing down when the wheel is in place.

There should be another allen bolt for adjusting the side-to-side pad location.

Start here.

mayukawa

I don't know the details of the ZG brake calipers (not a weight weenie), but if the centering screw doesn't work, your other option is to loosen the caliper bolt and then manually center and re-tighten the bolt.

Dellphinus

ANd it sounds like the original problem was your wheels need truing.

Al1943

When you mount your wheels on the bike do it with the wheels down and full weight of the bike on the wheels. Be sure the axles are fully seated.

You may need to learn how to adjust your brakes. Search for bicycle brake adjustment instructions for the type of brakes you have.

It is possible that your wheels need truing, but going out of true is usually a gradual process.

Your dealer should make various adjustments on a newly purchased bike at no cost to you.

Al

neil0502

I'm with Al.

Quickly in your OP, I thought your wheel wasn't fully seated in the dropouts.

I'd check that first, and then see where you are with brake centering.

rm -rf

The replies above are good advice.

See the Park Tool brake adjustment page. If one brake pad is closer than the other, use the little adjustment screw to re-center them. If they are too close or far away from the rims, use the adjuster knob where the brake cable housing meets the brake, to lengthen or shorten the brake cable.

A quick google shows your brakes might be "self-centering" (if everything works correctly), and fussy about bolt torques. In general, a bit tricky to adjust correctly.


Zero Gravity brakes are lightweight and expensive. That's why most of us don't have any first hand experience.

Is your wheel out of true (a side-to-side wobble in the rim)? Spin the wheel while off the ground. Does the distance to the brake pad change as the wheel makes a full revolution? If the brakes didn't pulse before, it's probably OK.

If you don't get any first-hand Zero Gravity adjustment replies, try a new post with "Zero Gravity adjustment problems" as the title.

Oldpeddaller

If this was yje first time you have removed your wheels, are you sure the rim was centred in the forks/ rear drop outs when you replaced them? It's unlikely they are out of true if the brake pad on one side makes contact with the rim all the time (all the way around the rim). More likely that either the wheel or brake is not centred. Check the wheels are centred in the fork/ drop outs first. If this doesn't fix it, loosen the brake mounting bolt and adjust the calliper so the brake pads are an equal distance from the rim on both sides. If the clearance on one side then needs adjusting there should be a tiny allen screw in the longer arm that you turn one way or the other to move both pads to the left or to the right. The small lever simply slackens the brake cable when you turn it upwards to increase the gap between the pads to allow space for the tyre to pass through when removing/replacing the wheel. When the wheel is back in place and centred, turn the lever so it points down. Good luck!