DOT4 vs DOT5
Road Master
Joined: May 2008
Posts: 1,196
Likes: 14
From: connecticut
Do not use dot 5 fluid. Find a high temp Dot4 fluid if youd like to upgrade or flush your current fluid.
http://www.raceshopper.com/brembo_lc...ke_fluid.shtml
http://www.raceshopper.com/brembo_lc...ke_fluid.shtml
Ultimate HDF Member
Joined: Nov 2007
Posts: 6,716
Likes: 13
Personally I don't think it would make a GD bit of difference. Use what the manufacturer suggests and you can't go wrong. You know the saying - if it aint broke don't fix it.
Sure if you're running a stock car at 200+mph where the brakes glow a bright red from the heat in the corners then you have to figure out the best fluids to use.
We have over grown lawnmowers in comparison. Run them for several hours in a straight line then gently apply the brakes to slow down for a light. We're not talking perfomance here, we're talking harleys.
Sure if you're running a stock car at 200+mph where the brakes glow a bright red from the heat in the corners then you have to figure out the best fluids to use.
We have over grown lawnmowers in comparison. Run them for several hours in a straight line then gently apply the brakes to slow down for a light. We're not talking perfomance here, we're talking harleys.
Outstanding HDF Member
Joined: Mar 2009
Posts: 2,216
Likes: 102
From: Central Illinois
Back in the late 70's-early 80's I worked at a Chevrolet dealership as a mechanic with several years working on very many Corvettes. Vettes back in those days had cast iron 4 piston calipers that were famous for leaking, mainly because so many Corvettes sit around for many months and driven only in good weather (kinda like our bikes), so the brake fluid would get moisture which would rust the caliper cylinders and when the brakes were used, the piston seals would slide over this rust causing leaks. We would rebuild these calipers in the early days, then in later years we began replacing them with stainless steel sleeved calipers, and in all cases put in DOT 5 silicone brake fluid, after flushing the system. The moisture problems went away and there was no problem with high speed braking or any other braking problems. We did not use any different seals in the calipers when we used the silicone brake fluid.
I am not sure if there are any side effects from using DOT 5 in a Harley, but if I was putting on new calipers, lines, etc I would not hesitate to go straight DOT 5 rather than 4. 5 does not harm the paint and also does not draw moisture. On my bike I change the brake fluid every 2 years, although I am using DOT 4 since there is no way for me to thoroughly flush out the 4 to put in the 5.
I am not sure if there are any side effects from using DOT 5 in a Harley, but if I was putting on new calipers, lines, etc I would not hesitate to go straight DOT 5 rather than 4. 5 does not harm the paint and also does not draw moisture. On my bike I change the brake fluid every 2 years, although I am using DOT 4 since there is no way for me to thoroughly flush out the 4 to put in the 5.
Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
With respect, Guntoter, take 5 minutes and do some google research about the compatibility! We have no idea what seals (material) are fitted, and with ABS on newer bikes these are now very complex systems.
These are brakes we are talking about here, not what tint shield we should be using. Why on earth would you want to even consider taking such an unnecessary risk?
These are brakes we are talking about here, not what tint shield we should be using. Why on earth would you want to even consider taking such an unnecessary risk?
Supporter
Joined: Sep 2006
Posts: 1,245
Likes: 69
From: Northford, CT
If a bike has ABS don't use DOT5 brake fluid.
The reason they switched away from DOT5 is that under ABS application small air bubbles form in the fluid. Low and spongy brakes are the result.
The reason they switched away from DOT5 is that under ABS application small air bubbles form in the fluid. Low and spongy brakes are the result.
Outstanding HDF Member
Joined: Mar 2009
Posts: 2,216
Likes: 102
From: Central Illinois
Thanks diesel and moe, did not know these things. I guess DOT 5 on ABS is a no go. Back in the days I did mechanic work we had no ABS. In fact I still don't on my Harley, although I wish I did.
Seasoned HDF Member
Joined: Jan 2006
Posts: 11,477
Likes: 3,006
From: Charleston, SC
I just had the front master cylinders off of both my bikes. I put some "Harley" brake fluid in and noticed it was some cool looking purple color. The old stuff was yellow.
I just now realized after reading this thread that I screwed up big time. Now I know what I'll be doing all weekend...cleaning out all the DOT 5 out of my DOT 4 systems...
Friggin great.
lp
I just now realized after reading this thread that I screwed up big time. Now I know what I'll be doing all weekend...cleaning out all the DOT 5 out of my DOT 4 systems...
Friggin great.
lp
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Seasoned HDF Member
Joined: Jan 2006
Posts: 11,477
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From: Charleston, SC
I know man. I'm totally blaming you too! You could have posted this a week ago! 
Anyway, I hope it'll be ok. Lot of work ahead of me I guess. Oh well. Thanks for the FYI. Least now I know to get it out of there. Something bad could have happened...Thanks much.
lp
Anyway, I hope it'll be ok. Lot of work ahead of me I guess. Oh well. Thanks for the FYI. Least now I know to get it out of there. Something bad could have happened...Thanks much.
lp
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Ultimate HDF Member
Joined: Nov 2008
Posts: 6,682
Likes: 12
I wonder if the thanks will go on my thanks counter thing? Lol I don't think it'll cause any damage to your bike but it think the two fluid curdle like old milk when mixe together. Maybe you can avoid a crash by flushing your system. And if this helps the new lamo thanks system, thanks for thanking me. 
Last edited by 1931jamesw; Dec 16, 2010 at 06:57 PM.