I have a 21 Street Glide Special with the RDRS. I
just checked my front pads, without removing
the caliper, and I see a good deal of the groves left on the set in the caliper on one side, but the set in the caliper on the other side are worn through and need to replaced. I'm planning on replacing both sets but is this a common occurrence or is there and underlying issue that needs to be addressed?

 

One side of the caliper is fixed, the other side is pressed out by the piston(s). It's normal to see one side wear more than the other some since only one side has the piston(s). The other side moves back a bit when the lever is released by the lubed pins. A great deal of wear on one side only can be attributed to many factors. Dirt, wear on the piston(s), dry caliper slide pins, sticky piston(s), are the most common.
A thorough inspection and cleaning are in store for you as well a pad replacement I would assume. Several videos and write ups on how to do that. As well as what's in the FSM.

 

Thanks for the response. I appreciate you helping me out with this. I was actually referring to the set in the left caliper compared to the set in the right caliper. It’s seems the pads on the caliper on the right caliper still have life left but the set in the caliper on the other side of the bike have to be replaced.

 

If you have the current Brembos they are 4 piston - no side is fixed.

That said, if your bike has "Linked Brakes" the front left caliper will activate when you press your rear brake in certain situations which... makes it wear faster than the right caliper. So, it's normal.

 

How many miles are on the bike? You must be riding the hell out of it...thats a good thing but just wondering what kind of miles it took to wear out brake pads on a year old bike.

 

Yeah I have. I’ve had it 7 months and I’m about to hit 15,000. I ride pretty aggressive most of the time.

 

Thanks. I just found it odd that the two separate calipers on the front weren’t wearing evenly. I’m probably just overthinking it.

 

There was also an issue where my front master cylinder was empty one morning. It ended up being from the Fat Baggers eEz Install Kit that was used for the Apes I had put on when l bought the bike. There is a splitter for the brake line extension inside of the fairing with a bleeder valve. It had loosened and leaked inside the fairing.

Shame on me for not researching it first and paying the to run it the stock way. Live and learn.

 

It will never be perfectly symmetrical. But it should be fairly close.

Either the caliper has pistons on both sides of the rotor (most motorcycles), or the caliper slides on greased pins (many cars).

When a piston sticks in the caliper, or the caliper sticks on pins, uneven wear takes place. Braking effect is reduced too.

 

Not necessarily. As LP says the brakes use a linked system.. As I understand it the pressing the rear brake actuates one of the front brakes also.. If you look at the SM, ABS brakes have separate lines from the ABS module to each of the front calipers. Front brake lever may actuate calipers differently..