Brakes not working
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Intermediate
Joined: Jun 2018
Posts: 33
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From: Grand Rapids Mi
Brakes not working
I recently changed the front dual disc brakes and single rear brake. But now the brake handle goes all the way to throttle and rear brake pedal goes all the way down. My motorcycle is a 1997 harley davidson ultra classic and any help would be appreciated.
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Joined: Mar 2021
Posts: 18,272
Likes: 3,684
From: backwoods
The silicone based brake fluid goes limp. Doesn't last as long as new stuff. I get dot 5 and 3 mixed up. But if it was good before it should be good stiill. But bleeding is probably not a bad idea in general. The silicone stuff needs to be flushed more often. $$$
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From: San Diego, CA
I think you have your fluid types mixed up....
When DOT 5 fluid (silicone based) was introduced in 1972, it was considered an improvement over the DOT 3, DOT 4 (Glycol based) fluids. It had higher wet & dry boiling points, does not absorb water, and does not hurt paint. Because DOT 5 (silicone based) fluid doesn't absorb water like DOT 4 (glycol based) fluids, it usually has a longer service life than DOT 4.
In fact many people with older vehicles and/or vehicles that that will sit for extended amounts of time (vehicle collectors), will often choose to use DOT 5 (silicone based) brake fluids.
The reason DOT 4 (glycol based) fluid is the main fluid used today, is that DOT 5 (silicone based) didn't play well with ABS systems. Basically it forms micro-bubbles when agitated, causing issues with ABS systems. DOT 4 (glycol based) does work well with ABS systems. Harley went back to DOT 4, from DOT 5, when they introduced their ABS system into the model line-up in 2005ish.
DOT 5.1 (glycol based) fluid is a more recent attempt to make a glycol based brake fluid with boiling points comparable, or sometimes better, than DOT 5 (silicone based) fluids.
Now, there are even some high quality DOT 4 (glycol based) brake fluids with really high wet & dry boiling points, like Motul 660 or Motul 700.
But because DOT 4, or any other glycol based brake fluid is "hygroscopic" (meaning it readily absorbs water), the DOT 4 family (glycol based) of brake fluids will generally need to to be flushed sooner, and their wet & dry boiling points will degrade sooner than DOT 5 (silicone based) fluids.
Last edited by hattitude; Apr 20, 2025 at 11:20 PM.
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From: Lititz Pa
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Seasoned HDF Member
Joined: Mar 2021
Posts: 18,272
Likes: 3,684
From: backwoods
New brake fluid, even though you should flush more often, will keep pedal/lever hard longer, again my experience. But I don't like working with it cause caustic,
Last edited by Rounders; Apr 21, 2025 at 06:30 AM.
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Seasoned HDF Member
Joined: Aug 2006
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From: Pennsylvania
I think you have your fluid types mixed up....
When DOT 5 fluid (silicone based) was introduced in 1972, it was considered an improvement over the DOT 3, DOT 4 (Glycol based) fluids. It had higher wet & dry boiling points, does not absorb water, and does not hurt paint. Because DOT 5 (silicone based) fluid doesn't absorb water like DOT 4 (glycol based) fluids, it usually has a longer service life than DOT 4.
In fact many people with older vehicles and/or vehicles that that will sit for extended amounts of time (vehicle collectors), will often choose to use DOT 5 (silicone based) brake fluids.
The reason DOT 4 (glycol based) fluid is the main fluid used today, is that DOT 5 (silicone based) didn't play well with ABS systems. Basically it forms micro-bubbles when agitated, causing issues with ABS systems. DOT 4 (glycol based) does work well with ABS systems. Harley went back to DOT 4, from DOT 5, when they introduced their ABS system into the model line-up in 2005ish.
DOT 5.1 (glycol based) fluid is a more recent attempt to make a glycol based brake fluid with boiling points comparable, or sometimes better, than DOT 5 (silicone based) fluids.
Now, there are even some high quality DOT 4 (glycol based) brake fluids with really high wet & dry boiling points, like Motul 660 or Motul 700.
But because DOT 4, or any other glycol based brake fluid is "hygroscopic" (meaning it readily absorbs water), the DOT 4 family (glycol based) of brake fluids will generally need to to be flushed sooner, and their wet & dry boiling points will degrade sooner than DOT 5 (silicone based) fluids.
When DOT 5 fluid (silicone based) was introduced in 1972, it was considered an improvement over the DOT 3, DOT 4 (Glycol based) fluids. It had higher wet & dry boiling points, does not absorb water, and does not hurt paint. Because DOT 5 (silicone based) fluid doesn't absorb water like DOT 4 (glycol based) fluids, it usually has a longer service life than DOT 4.
In fact many people with older vehicles and/or vehicles that that will sit for extended amounts of time (vehicle collectors), will often choose to use DOT 5 (silicone based) brake fluids.
The reason DOT 4 (glycol based) fluid is the main fluid used today, is that DOT 5 (silicone based) didn't play well with ABS systems. Basically it forms micro-bubbles when agitated, causing issues with ABS systems. DOT 4 (glycol based) does work well with ABS systems. Harley went back to DOT 4, from DOT 5, when they introduced their ABS system into the model line-up in 2005ish.
DOT 5.1 (glycol based) fluid is a more recent attempt to make a glycol based brake fluid with boiling points comparable, or sometimes better, than DOT 5 (silicone based) fluids.
Now, there are even some high quality DOT 4 (glycol based) brake fluids with really high wet & dry boiling points, like Motul 660 or Motul 700.
But because DOT 4, or any other glycol based brake fluid is "hygroscopic" (meaning it readily absorbs water), the DOT 4 family (glycol based) of brake fluids will generally need to to be flushed sooner, and their wet & dry boiling points will degrade sooner than DOT 5 (silicone based) fluids.
My 2003 Sportster has DOT 5 and it is a bear to bleed the system, particularly the rear line.
There also is DOT 5.1 (why they ever called it that is anybody's guess) that is glycol based.
Check the filler cap on your front and rear master cylinder reservoirs and it should tell you the type of DOT fluid to use.
DOT 5 does not absorb water but does degrade over time and needs flush/bleeding from time to time. Reminds me I should flush the brake fluid in my Sportster as it has been 4 years since I did it last.
OP - report back if you got the brakes working or not.
NOTE:
The above information, while credible, is worth what you paid for it and should not be considered gospel.
Do due diligence, research and have a H-D Field Service Manual before working on your bike.
You will probably have many opinions and suggestions presented; make sure you research the person providing the helpful information as there are some who provide good information that is useful and some who speak out of other orifices with gibberish. You will figure out this quickly.
Last edited by CoolBreeze3646; Apr 21, 2025 at 07:41 AM.