Dot 4 or Dot 5 brake fluid what's the difference?

ramstein-dh · Jan 11, 2012

I'm going to my local car spare's shop in the morning
before i go and buy my brake fluid what would you
guy's recommend?
Dot 4 or Dot 5.1?

What is the difference and will it really matter , this is for hope brakes
and for downhill and will not be used all the time.
Also does the brand make a difference?

cheers

jamabikes · Jan 11, 2012

1.1

5.1 is designed for high performance cars so over kill on a bike imho.

i use what ever i have at the time. you can use either in a bike brake designed for dot. not sure you can mix them so best flush the old stuff out first to be sure. to be sure.

lewis1641 · Jan 11, 2012

5.1 is a higher boiling point so will be more useable. not sure how important that is on a pushbike

cyfa2809 · Jan 11, 2012

But its also slightly thicker isnt it? Not sure if you would notice but many have used either/or with no problems. DOT 5.1 is more expensive though i expect.

I paid £10 for a litr of mobil dot 4 fluid.

ramstein-dh · Jan 11, 2012

thanks for the info peeps

price will be my guide i guess , but i don't need 1 litre.

Are all makes the same as i suspect a well known name will be more
expensive also.

cyfa2809 · Jan 11, 2012

Yeah price varies by brand. Mine was just teh cheapest biggest on ebay. I dont like to run out of things! I have used 20% or so in a year i guess. Probably eaten most of it.

02gf74 · Jan 11, 2012

try Wilkinson for the DOT brake fluid if you want cheapness - but still good as it needs to meet the spec.

bren · Jan 11, 2012

dot 5.1 is synthetic. dot 4 and lower is mineral based. on older cars dot 5 is a no-no as it can rot the seals. i can't imagine that is an issue on bikes, but to be honest, the benefits of dot5 are wasted on bikes, they just dont generate the extreme heat that high performance car brakes do, so save your money and use dot4, you wont get close to the limits of dot4, not even nearly, not even if you heat your discs to to a nice shade of blue

cyfa2809 · Jan 11, 2012

Ah so thats why people saybrake fluid will eat paint yet when i eat my brake fluid (dot 4) i dont die.

gradeAfailure · Jan 11, 2012

Always remember that DOT4 and DOT5.1 can be mixed but DOT5 is completely different and not used on bikes at all.

Oh, and Shimano use Mineral oil which can't be mixed with DOT stuff and vice-versa.

Dot 4 or Dot 5 brake fluid what's the difference?

ramstein-dh

Retro Guru

jamabikes

Old School Grand Master

lewis1641

cyfa2809

ramstein-dh

Retro Guru

cyfa2809

02gf74

Old School Grand Master

bren

Retro Guru

cyfa2809

gradeAfailure

Senior Retro Guru

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