The DT-3i. Values outside the target are isolated and adjusted. When the variance falls in the target range, in our example. More detailed instructions are included with the DT-3i. Trade Resources. For the highest level of accuracy, a dial indicator: DT-3i. There are two quick things to check before getting started: Wheel alignment if you have open drop-outs.
Seating the wheel properly may solve the issue. Bearing play at the hub is also easy to check for by rocking the wheel back and forth as shown. Wheel that is misaligned in the dropout — loosen and re-seat Visible play at the hub. Set the bike in a stand or upside down on the ground in order to get the wheel spinning freely. Watch for wobble at the caliper between pads. Look for the opening and closing of the gap.
Find a section of the rotor that needs truing, and note which way it needs to be bent to correct the runout. Here, a flashlight can be useful. A sheet of paper can also help make the lateral deviations, called runout, more visible as the rotor spins. Rotate this section of the rotor out of the caliper. Use a rotor truing fork tool to flex the rotor in the appropriate direction in order to improve the bend. Always begin with a small amount of effort on the tool, and then apply more effort if no improvement is seen.
Spin the wheel and sight the rotor again. Repeat as necessary. When the rotor is not rubbing the pads as it spins, it is adequately straight.
Deviation to the outside Flex the rotor towards the inside. You can see in the photo how this tool has two ends that slip over the rotor for excellent and precise leverage. You can slip the top of the tool over the top of the rotor to pull out or push in to remove a side-to-side wobble. You can also use the end with the short horizontal slot to remove a twist in the rotor by slipping that notch over the twist and pulling or pushing the tool as you hold it 90 degrees to the rotor.
If it helps, you can mark the bent area of the rotor so you can keep track of your progress. With the wheels on the bike, you can sometimes sight through the brake and watch the rotor come through. You then rotate the wheel to bring the wobble outside the brake so you can straighten just the right spot. Another trick that can work is holding a flashlight just so, to light the inside of the brake so that you can spot the bends.
Something as simple as a pencil for the pointer and a rubber band to hold it in place might do the trick in a pinch. If you come up with something that works well, please share it in the Comments section. See the photo. It still takes time and patience to find and true wobbles, but because the indicator shows you exactly how true the rotor is becoming, the trial and error is greatly reduced. Great article.
Since my wobbles are sometimes apparent on week long tours and I might not be near a LBS, I do carry a small vise grip. TSA damaged the rotor on my tandem on a trip to Canada. I wish I had known how to do this then. By the time I figured out what was wrong, the pads were damaged as well.
It made for some scary down hills with only my rear brake on a tandem. Hello Dave. However, for minor or impromptu rotor truing jobs, you have all the truing tools you need with you all the time, your thumbs.
Sight through the brake caliper to find the spots that are rubbing, then turn the wheel to get them out in the open. Cover the rotor with a clean cloth, cardboard, or even just paper, to keep skin oil off the rotor, then press or pull on it as necessary with your thumbs.
Spin the wheel again to check your results and repeat as necessary. I use this method out on the trail all the time mostly for people I ride with. Note it probably will not work on rotors that are kinked from an accident, but most rotor truing is about removing minor warping, which is easy to do by hand. Your email address will not be published.
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