Dot 3 or Dot 4 ?, that is the question.

Michael R · Nov 20, 2016

I have a 1974 850 Commando with a Japanese master cylinder and an OEM front disk brake. My Norton Guru say I should use Dot 4. My Owners handbook say Dot 3. I would value the opinions of this forum. Dot 3 or Dot 4 ?

pantah_good · Nov 20, 2016

I'd use this.
http://www.castrol.com/en_us/united-states/other-fluids/brake-fluid/brake-fluid-dot-4.html

Rohan · Nov 20, 2016

The Owners Handbook for what though ?, since you are mixing your hardware.

Dot 3 and Dot 4 are both heavy alcohols, its just that Dot 4 boils at a higher temp.
So in theory should be better.

kommando · Nov 20, 2016

Dot 5.1 is higher boiling point than 4 and backward compatible to 4 and 3, DOT 5 is not compatible with 5.1, 4 or 3.

MS850 · Nov 20, 2016

kommando said:
Dot 5.1 is higher boiling point than 4 and backward compatible to 4 and 3, DOT 5 is not compatible with 5.1, 4 or 3.

I'm suprised they used 5.1 designation seems it might get confused with dot-5

dave M · Nov 20, 2016

As Rohan says, Dot 4 boils at a higher temperature and Dot 3 and 4 can be mixed without any ill effects, so no need for special flushing if changing from one to the other.

WZ507 · Nov 20, 2016

pantah_good said:
I'd use this.
http://www.castrol.com/en_us/united-states/other-fluids/brake-fluid/brake-fluid-dot-4.html

+1, this product replaced Castrol's GT/LMA and is perfect for your application.

Deets55 · Nov 20, 2016

I have been using this for a while

http://www.motosport.com/product?psrefe ... aQodLXcBdg

Probably over kill for my Norton but riding two up with luggage on steep grades my Gold Wing front brakes get pretty hot. Considering how often I change the fluid and the amount used its really not too expensive. Everything else I use Dot 4
Pete

Dot 3 or Dot 4 ?, that is the question.

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