I had one go bad after 50,000 miles they where Accel glass race wire won't use them on a hog again. Not just the heat but the vibration is hard on them. Friends bike had one that was bad can't remember the miles but under 100,000 by 20- 30,000. I have mororso 8mm wires from summit racing on it now and a stock set barely used as spares on the wall. Like was mentioned checking ohms is a good idea after the miles add up or just replace.

 

I change ‘em every time I rotate my shifter peg.

 

I don't know the wear rate. What I don't like is when people say they are working so why change, or still good. Things wear over long period, and you don't notice. Look at tires and brakes. If you ever do do a lot of miles in short period, it will shock you.

Does it really matter about the plugs, I dunno.

 

This^ I just replaced the wires on my RK a couple weeks ago. No problems and they seemed to be working fine but they had wore to the point they were no longer in spec, I replaced my coil at the same time for the same reason. I would rather do preventative maintenance than roadside maintenance if I have a choice.

 

as long as the plug is being fired and your leg isn't.....you're OK

some here gave me chyt about swapping over to 10mm heavy insulation wires.....until I asked them if they had ever been busted by a cracked or worn out plug wire.
they fell silent then.

 

I have no idea, I changed mine right after I bought the bike cause I wanted the pretty orange ones...

 

Spark plug wires never go bad. Only the insulation dries out overtime causing them to go bad.

 

After reading this ,I’m going to order some new used plugs that aren’t old or dried out . Maybe like just 3 or 4 years old for $10 bucks .

 

Yeah, wait for it to take a dump in the middle of BFE on a dark, rainy Sunday morning at 2 am.

 

It really depends on the application. Some are only a few inches long while others are almost two feet in length.