I know I know, get the manual. The manual for my last bike (a 2002 Dyna) says DOT 5, but other threads on the forums give misleading info.

Some say DOT 4 and some say DOT 5 from the factory. Which is it?

 

What does the master cylinder cap say?

Rule of thumb. Dot 3 and 4 are clear to amber colored. Dot 5 is usually deep blue or purple in color.

 

Don't have the bike with me right now...long story short, I'm switching to used Tokico calipers that had DOT 4 in them. I believe the FXDX runs DOT5.

I've got some free time tonight so I'm debating cleaning all the DOT 4 out of the Tokico calipers and prepping them for DOT 5 conversion (which I'm nervous about not knowing much about these sport bike brakes and seals.....or just flushing the DOT 5 out of the master cylinder and going with DOT 4 from now on.

 

And let me add this...I'm doing all new lines and fittings with these calipers so would it be easier to go to DOT 4? Run denatured alchohol through the master and and call it good? I could give a damn about what happens south of the handlebars as everything below the master cylinder would be new anyhow.

My thought is flush whole stock system (get the master cylinder really clean), change all lines and and add calipers, then add DOT 4.

If I change to DOT 4, any issues with the seals in the stock Master?

 

the 01 FXDX came with DOT 5 , clean the Tokico calipers and use DOT 5

 

I was with you on switching to DOT 4 until HDS4me said it came with DOT 5. That means the MC cover will say DOT 5. Clean out the calipers and run DOT 5 so in the future there is no confusion. Last thing you want is to mix DOT 4 and DOT 5.

Seals don't care if you have DOT 4 or 5.

 

This is what I would do. It did come with DOT5, but you should have no issue flushing with plenty of denatured alcohol and switching to DOT4.
This is what I did and it's commonly done when switching to the Harley Brembos because the calipers are not supposed to use DOT5. Also, much easier to flush the master than the calipers, too.

edit: sure, your cap may still say DOT5, but you can always buy a different cap. Also, you just have to remember that your rear is still DOT5, but sounds like you do your own work so that shouldn't be a problem.

 

This is exactly what I did. I pondered the choice for awhile, and I spoke with Speed Merchant (who made my brackets) and with Spiegler (who made my lines). I kind of wanted to use DOT4, but there were too many factors that pointed towards 5. One thing that both suppliers said was that the seals in the M/C would be less forgiving to a DOT4 swap than the Tokico calipers would be to a DOT5 swap. They both recommended that the M/C be completely disassembled and rebuilt if going to DOT4 (which I wasn't averse to, but my M/C really seemed in good shape), whereas the calipers were easy to clean and prep for DOT5. I ran a lot of denatured alcohol through them, and then blew a lot of air through (in both directions).

Sticking with DOT5 gives me the following bonuses:

-The fluid type matches what the resovoir lid says (important if someone else decides to add fluid)

-I don't have to use two kinds of fluid when performing maintenance

-DOT5 doesn't eat paint (and skin) if accidentally spilled

With new lines and a good bleeding, the lever is every bit as firm and positive as any DOT4-equipped bike I've ridden (including my "faster" bike).

 

Thanks everyone. Yeah still pretty torn, both sides have good arguments. Probabaly going to end up doing DOT 5 for continuity...

 

If you do go with DOT4, I would strongly recommend rebuilding the M/C instead of just flushing it. I don't have first-hand experience, but I've read that a sludge is created when 4 and 5 come in contact with each other. A good flushing will remove most fluid residue, but the seals are still heavily impregnated with the original fluid type.

Maybe the risk is low, but I really don't like risk when it comes to brakes.

Either way, good luck with it. Looking forward to pictures and impressions when it's done!