Just a quick disclaimer: I've searched here and Googled for a good hour now but just can't seem to find a solid answer. I'm not running a front brake so it's pretty important I get this right!

I'm at the final stages of building a custom rigid chopper using a 2001 Sporty 1200 Custom as a donor bike. I ended up reusing the rear caliper as it was in good shape, both mechanically and visually. The rear master cylinder however looked horrible. I ended up replacing it with an aftermarket chrome one from J&P Cycles (V-Twin Manufacturing / J&P Part: 2400653). I have both mounted to the bike and just received my new hose and fittings today. So, to recap - brand new master, fittings, hose, brake disc.. everything but the rear caliper itself.

So here is my question (finally, right?) - The chrome cover on my master cylinder says to only use DOT 5. I could swear (albeit that both my bike and shop manual are at home and I'm at work) that a 2001 Sportster calls for DOT 4(?). If that is indeed the case, do I use DOT 4 or DOT 5? My lines and fittings could care less. I know from what I read that people say DOT 4 has better stopping power. DOT 5 is safe for paint (but that doesn't concern me). My '76 Shovel uses DOT 3. DOT 5.1? Do we need another option?

Can anyone help me out here?

UPDATE: Someone just looked in their shop manual and verified that a 2001 Sportster uses DOT 5. Crisis adverted. Thanks!

 

It is not so critical as to what type of fluid that you use as long as the system is clean and free of contaminants ... then flushed ( you can use denatured alcohol to do this ) to ensure that there is no fluid left in the system ... Then you can use which ever fluid you are comfortable with ... Yes Dot 5 is silicone based and will not harm painted surfaces nor will it absorb moisture ... It does not work well in ABS systems as it tends to foam during repeated duty cycles ... Dot 4 is the more common fluid ... If it's just a basic scooter and it does it's share of sitting for extended periods DOT 5 would be the better fluid to use .... Here come the haters ... :>)

 

+1 there.

I like DOT 5 as you can just forget about it once its all in and setup. I have gone 20 years on my rear without having to take the top off the master cylinder.

 

The choice really is yours IMHO. If as Larry suggests you flush any parts that have previously had brake fluid in them, use whichever you fancy. DOT3 is an early spec and may still be available, but I would pass and use DOT4 instead. DOT 5.1 is an alternative to those two, but best left on the shelf IMHO - don't confuse it with DOT5!

My Glide has a mix of brake components and I am about to do some further changes, but as it was born in the days of DOT5 I will continue to use that. In your shoes I would do the same, but you could alternatively toss a coin!