Swapping front and rear pads tomorrow on a 98 Super Glide. In case I need to top off cylinders with fresh brake fluid when moving pistons, I need a fresh can. This was in the front master cylinder, not sure if its DOT 4 or 5, heard bad stuff about mixing 4 and 5. Cap does say it's DOT 5 only, but wanted to make sure.

 

You don't need to top it off, you need to flush it!

 

^^^^^^ And use DOT 5 like the cap says, needs flushed badly. Probably need to flush the rear system also.

 

Bought it recently, shop said they bled it, guess not.

 

Simple water mixes with DOT 4 will not mix with 5. You already know mixing 4 and 5 bad news. If you wish to covert the 4 you must flush and clean system..
That brake fluid needs to be flushed.
Bleed and flushing is two different things.

 

I’d use Dot-4 and like said completely change it out. Brake feel will be so much better afterwards. You get used to it degrading.

 

I completely disagree. The day his master cylinder leaks all over the tank DOT 5 won’t peel the paint.

Completely flushing and removing the old fluid is a lot of work and there is no benefit on that bike.

They went to DOT 4 due to ABS, not because anything was better.

DOT 4 also absorbs water so he will be bleeding more often, opening masters and risking paint damage.

 

This is a bar hopper. No highways, no crazy long distances, just something to go to the beach, take on backroads. DOT 5 it is.

 

Nonsense.

All Harley OEM brake systems from 1976 through 2005 use DOT 5.

 

You still need to do a full flush on that bike . That fluid is nasty and will cause more issues and higher labor and cost to repair.