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Discussion Starter #1
The manual says dot 4. Susie the svc mgr at arlen ness said dot 5. Now I'm thoroughly confused. Says dot 5 is not compatible with abs which the hb doea not have so is dot 5 ok ?
Help now please !

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The manual says DOT 4 for a reason. DOT 5 is not compatible with rubber parts designed for DOT 4.
DOT5 has nothing to do with "not compatible with rubber parts".

Dot 5 is a SILICON based fluid (therefore having NO EFFECT on ANY PARTS FYI) However its primarily used in racing applications for higher boiling points with HEAVY braking over long periods of time.
OR the classic car guys who don't want to take the chance to ruin a paint job... however this application is not just put new fluid in with a simple flush.

I will tell you this... if you are asking this question on a forum... DO NOT USE DOT 5 FOR ANY REASON. If you don't know what it is for then don't use it because you WILL screw up and you WILL have to replace your entire braking system.

Unless you are track racing your Vic then there really is absolutely no reason to be using a 5 or a 5.1 fluid... you simply do not need the high boiling points or the chance to junk your system.
 

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Discussion Starter #4
yeah confirmed dot 4 and that was my original assumption. Didn't know why the gal said dot 5. Just replaced my pads and didn't even touch the fluid anyway. will exchange the 5 for the 4 and top off today. Easiest damn pad job i've ever done btw. nice job vic.
 

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Yes, what the other guys said. Use DOT 4 not DOT 5. And don't ask Susie any more technical questions. :D
 

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Lesson learned, eh Steve? Very few production vehicles use DOT5, but most racers do due the higher boiling point. However, they install it in new or completely rebuilt brake systems and change out the fluid after each race session. Big problem with using DOT5 in street vehicles is water collecting at the low points, the calipers and causes corrosion. DOT3 and 4 are hydrogenous and hold the absorbed moisture in suspension until you do a fluid change as you should every second year.
 

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You got me thinking so I did some Internet searches. For the most part I stayed away from opinions on forums. I did find three references that sounded like they knew what they were talking about:

1. DOT 5 Brake Fluids on Greater Atlanta British Motorcycle Association website

2. Selecting Brake Fluid on Buckeye Triumphs website

3. Silicone-based DOT5: busting the myth on (of all things) Mountain Bike Review's website.

The last one was the only forum I referenced but I compared all three to the information found on EBC Brake's and Brake Tech's websites. Both of the brake websites seemed to confirm the other sites information but just didn't explain it as well.

DOT 3, 4 and 5.1 are glycol-based fluids and play nice with each other. DOT 5 is silicone based and doesn't play nice with the others.

The main advantages of DOT 5 seem to be it doesn't destroy paint and it doesn't absorb water. These traits make it ideal for classic vehicles that aren't used too much since you don't worry about damaging the paint and you don't have to change it out every 2-5 years. Also it has superior lubrication of master cylinder and caliper pistons which could result in nearly zero component wear.

The disadvantages
  • It is more susceptible to air bubbles which will reduce performance
  • It is less compressable so it doesn't work in ABS systems and may feel softer
  • Allows water to pool in the calipers which could cause corrosion
  • A lot more expensive
  • Has negative effects if used in a DOT 3/4/5.1 systems that wasn't properly purged.
Every single reference I could find agree that DOT 5 will NOT harm the brake system seals or any other rubber parts.

Personally I'll stick with DOT 4 as recommended in the owners manual.
 

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Good work Sherlock.
 

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Unless you are track racing your Vic then there really is absolutely no reason to be using a 5 or a 5.1 fluid... you simply do not need the high boiling points or the chance to junk your system.
Not true-DOT 5.1 is completely comparable with DOT 3&4 fluid systems. It is a full synthetic with some of the best/ highest boiling points of any fluid on the market & I've been using it for years with excellent results- it's especially good in ABS systems. Been using Motul 5.1

Edited to DOT 3 & 4
 

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DOT 4 can damage paint, if you spill it and prone to water contamination. DOT 5 does not harm paint and is not prone to water contamination.

At least that is my understanding.

BUT

I've also been told you cannot mix the two.

I say go with MOM (motorcycle owners manual).

Ride safe.


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Not true-DOT 5.1 is completely comparable with DOT4/5 fluid systems. It is a full synthetic with some of the best/ highest boiling points of any fluid on the market & I've been using it for years with excellent results- it's especially good in ABS systems. Been using Motul 5.1
You're half right. As stated above, 5.1 is compatible with DOT 3/4. However, it is NOT compatible with DOT 5. :)
 

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Not true-DOT 5.1 is completely comparable with DOT 3&4 fluid systems. It is a full synthetic with some of the best/ highest boiling points of any fluid on the market & I've been using it for years with excellent results- it's especially good in ABS systems. Been using Motul 5.1

Edited to DOT 3 & 4
Goatlocker is exactly right.

5.1 is glycol based it is NOT SYNTHETIC AT ALL. however, the only reason to run a 5.1 glycol base is to have a higher boiling point.... you know for HEAVY BRAKING... Like found here... https://www.youtube.com/watch?v=y2Q4OpGCfME

if you are racing your bike at a place like this... you are PROBABLY already using a high boiling point fluids in ALL parts of the machine.



again... I use DOT 5 in my sports car, primarily so I don't screw up the $10,000 of body work I have (doesn't matter anymore after hitting the deer in the thing) but also to feed my huge piston brakes when I'm on the track... That's why people use the full Synthetic, to save their paint on classic cars, and to keep the "car show track queens" as shiny as possible...
 
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