My 2008 xl1200C has sensitive rear brakes (they lock up easily in a panic stop). Would longer shocks help, currently the rear is on 10.5 inch not the stock 11.5 inch length.
Any ideas to improve the rear lock up problem?

 

Have you made sure your rear reservoir isn't over filled, if it doesn't have enough room for expansion/fluid return, then your rear brakes are never completely released, and would be overly sensitive

 

Practice panic stopping so you know how to react.

 

Its a good point, but I have checked it by validating the rear wheel turns freely both when cold and after some use.
I was thinking maybe as you stop and your weight shifts forward the rear may be feeling lighter due to the shocks hitting the top of their travel with the shorter springs.

 

If that's the case, then consider either stiffening up the front suspension a bit, so you will dive less, therefor keeping more weight on the rear wheel. Or practice panic stopping with less front brake initially let the rear bite without locking up, then smoothly add front brake, and it should dive less, and not lock the rear..... Maybe? That's how I did it on hard pack trails on a dirt bike, and it worked..

 

How old/hard is your rear tire by the way?

 

With your rear wheel turning freely and no obvious awkward behaviour of the rear brake mechanics, I am also getting a bit curious about your 'panic stops'.

Do you apply a proper braking technique? Braking power should mainly go to the front, in emergencies just short from blocking the wheel to get max effect. The front brake is so important, because all the load will be on the front while you're braking. Use both brakes, but heavy braking to the rear (not only emergencies) will easily make the rear wheel block and the rear swerve away under your butt, so you gotta be cautious there.

 

I try to avoid panic stops, but if you commute they can happen.
Its also a relative thing. I have two bikes and the sportster just seems more prone to locking the rear wheel. I think it really just comes down to getting the feel of the bike.

 

Slow down..If you have slid your tires a few time lately, you are driving way to fast and not looking out ahead unless you can blame it on someone just pulling out in front of you from not looking. It takes a lot of practice to not do it since you tend to go fwd in a panic and come down on the foot brake that much harder.

 

It's easy to lock the rears. Fortunately under most situations its perfectly stable until you hit a slick oily spot and then you have to dirt track leg down to keep it up. I lock it up a few times a year usually when I'm hard on the brakes for one reason or another. No harm no foul.