Changing brake fluid dot4 to dot5 | GTAMotorcycle.com

Changing brake fluid dot4 to dot5

FattBoyy

Well-known member
I am going to put some old brembo caliper from a Ducati on my fatboy.

The brembo came off a dot4 set up and I will be running for 5.

I am going to take the calipers apart to clean. What is the best way to get the dot 4 residue off?

Thanks in advance for your replies
 
Interesting question. I don't know the right answer, Not knowing any better, I would go with dissassemble, clean with alcohol and flush with dot 5 while it is apart so you know there isn't any 4 left in it.
 
I would recommend against this. Dot4 is superior to Dot5 for motorcycle applications. There is a reason why no one uses it at the track. Dot5 has poor feel and is spongier. You would need to fully flush and clean the system. If this is for a performance application, use a high-temp dot4 like Motul RBF 660.
 
You need to clean EVERY drop of residue from the entire braking system in order to convert.
Calipers, cylinders, lines, everything.

It's probably easier to buy all new components vs trying to flush and clean them...

Dot 5 also requires more frequent changing and maintenance from my understanding.

It isn't worth the hassle. Stick to high quality DOT 4
 
I am going to put some old brembo caliper from a Ducati on my fatboy.

The brembo came off a dot4 set up and I will be running for 5.

I am going to take the calipers apart to clean. What is the best way to get the dot 4 residue off?

Thanks in advance for your replies

Harley's use DOT 5, for those above responses. Mixing the two can be catastrophic to clean up.

Completely disassemble the caliper, clean thoroughly with brake cleaner. At least 4 or 5 times, then reassemble with new seals. I don't think you would have any issues with the metals in the caliper, but I wouldn't trust the seals to be reused.
 
If you want to "upgrade" from DOT4, just go to DOT5.1 and make your life easier. If you really want a homogeneous setup on your HD, take the calipers apart, throw away & replace anything made of rubber, flush it with ???, and I guess that'll do it. Don't screw up the pistons or bores during the process

If JohnnyP636 weighs in, ignore what I said and do whatever he says instead as his word is law on brakes
 
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Op. It's a brake system and I wouldn't mess with it. Sure, it's cool to have a Brembo calliper but, it's still a FB and a single disc front rotor.


Not sure if the dot 4 would work well with HD master Cylinder? This why going with the dot 5?

Just paint the calliper red and put a sticker on. Jk.

Personally, I wouldn't make the change. But, your ride, you decide.

Good luck!




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Hey guys let me clarify a couple things I guess I was not too clear on because everyone is asking why .

Currently my bikes front brake is made up of single rotor with a single piston caliper. The system runs on dot 5 which is standard for older Harley's. The single piston caliper has very bad stopping power for a bike as heavy as mine

The brembo I purchased is a four piston caliper which came off a bike that ran dot4.

Because I am keeping my Mc and braided brake line. The only thing I need to do is do a real good cleaning on the brembo caliper to remove the dot 4 and attach it to my brake line.
 
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Like everyone is saying ... the calipers need to be disassembled and the individual parts cleaned with brake cleaner and/or alcohol. The pistons and seals need to come out - you'll never get traces of the old fluid out from between the crevices otherwise.
 
What year is the front end on this?
 
Like everyone is saying ... the calipers need to be disassembled and the individual parts cleaned with brake cleaner and/or alcohol. The pistons and seals need to come out - you'll never get traces of the old fluid out from between the crevices otherwise.

Yep a rebuild. Once I take it all apart I will put in ultrasonic cleaner. Then clean with alcohol and steam blast it. Then put all the new seals in. That's my plan
 
Should be good to go then.

Just keep everything spotless going back together. Post a pic or two after it's al done.
 
Something to consider as well. The master cylinder and the caliper/piston(s) are 'matched' in that if the ratio between surface area of the two are not in some ranges you can get really funny brake feeling. So though you have more pistons in the Brembo your master cylinder may not have the volume to make them feel all that much better.

I have used the info @ https://www.vintagebrake.com/mastercylinder.htm a few times when mixing and matching calipers and MC on older bikes and generally I found the ratios mentioned here did turn out OK though everyone likes a different feel for brakes.

I started to look into this when I tried to upgrade an EX500 front end and ended up with stronger brakes but had no feel to them.

Jeff
 
Something to consider as well. The master cylinder and the caliper/piston(s) are 'matched' in that if the ratio between surface area of the two are not in some ranges you can get really funny brake feeling. So though you have more pistons in the Brembo your master cylinder may not have the volume to make them feel all that much better.

I have used the info @ https://www.vintagebrake.com/mastercylinder.htm a few times when mixing and matching calipers and MC on older bikes and generally I found the ratios mentioned here did turn out OK though everyone likes a different feel for brakes.

I started to look into this when I tried to upgrade an EX500 front end and ended up with stronger brakes but had no feel to them.

Jeff
Good point. I did look Into this and these two part are a good match. Ofcourse we shall see


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One of forum members that I do work for brought this up...


So are you switching from DOT 4 to DOT 5.0 ? DOT 5.1?
DOT 5.1 is backward compatable but DOT 5.0 should' be mixed or come in contact with anything.
 
Classic GTAM.

"I'm switching to an incompatible brake fluid, what's the best way to clean my parts?"

- Don't do it, you'll die in a fiery crash!

- I'm on team DOT4, you should be too.

- Your socks don't match.

"Uhm, OK guys I'm going to use an ultrasonic cleaner, then alcohol, and finally steam blast it and use all new seals."

- Watch for zombies!

- I didn't read any of the thread, what's it about?
 

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