Ask a J&P Tech: How to Measure Motorcycle Cable and Brake Lines


February 17, 2010 | By: Bud Milza

Some of the most frequently asked questions we receive [through the J&P Cycles Chat Service] are about extended control lines for oversized handlebars. For example, “I would like to put a set of 20” Wild-1 Psycho Chubby Apes on my bike. What length cables and brake line do I need to order?

If there were a scientific formula to calculate the proper cable and brake line lengths for every possible combination of bars and risers, on every single model of bike, it would make ordering a bit easier. Unfortunately there isn’t, so we always recommend to customers that they mount the bars first, then take an accurate measurement for the proper length cables and brake line.

One method for measuring your cables is through the use of thin gauge wire. Once you have the bars installed and in position:

  1. Route the wire in the same manner that you would like the cables to run.  For example, with throttle cables, start at the carburetor (or throttle body) and route the wire up to the throttle housing on the bars.
  2. Be sure to turn the bars all the way to the left and then back to the right to assure that you will have enough cable to cover your full turning radius.
  3. You are now ready to take your measurement. Use the same method to measure for the clutch cable and your brake line.
  4. Once you have these measurements, subtract the length of your stock cables and brake line to find out how many inches over stock you will need to order (for example, +6 or +8 over stock). Cable and brake lines are measured by the casing length only so do not include the cable itself of the fittings at each end.
  5. Finally, do not overlook the fact that you will need to extend your handlebar control wiring. This method of measuring will work for them as well.

Here at J&P Cycles, we offer handlebar wiring harness extension kits that are available in +4 through +24-inch lengths. These kits are also available for 2008 and later Harley-Davidson touring models with the electronic throttle control.

Comments: 8 Comments | Categorized Under: Tech Tips

Comments (8)

I have another question guys. I have a1982 HD roadster 1000. It has two throttle cables. The closed cable has been removed for some unknown reason. The website lists cables as THROTTLE and IDLE. I presume the CLOSE cable is the idle cable.

Please advise.



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[...] our previous blog posts about extending your motorcycle cables and brake lines, and another about measuring for comfortable bars, we thought it’s about time to take on the [...]

very helpful article. many thanks

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