Recommendations for Brake fluid.

B

Baza

Active member
 Oxfordshire
I am doing a overhaul of my brakes ( caliper painting / S/steel hoses etc) and will be changing the brake fluid , Dot 4 seems to be the standard spec for the vehicle but there is quite a bit of info about 5 or 5.1 spec any comments / experience on which spec and which supplier to use.
 
As you've probably found out DOT 5 and DOT 5.1 are very different products and will not mix. If you decide to use 5.1 the whole system will need flushing. I was advised to carefully consider it's impact on standard seals as it may be adverse in the longer term.

Harley's use 5.1 as a factory fill so the bike is made for it. Seems a shame it's not more widely used as 5.1 seems to offer many advantages. Need to look closely at boiling points, google is your friend.
 
bob4333 said:
As you've probably found out DOT 5 and DOT 5.1 are very different products and will not mix. If you decide to use 5.1 the whole system will need flushing. I was advised to carefully consider it's impact on standard seals as it may be adverse in the longer term.

Yes DOT 5 is a silicon based fluid and will not mix with any other fluid, however as far as I understand 5.1 is a glycol based fluid and is compatible with Dot3/4. The advantage being higher boiling points. I have not found any comments on damage to seals on 5.1 . However as I do not take to the track I really do not need the extreme higher temp. Although I do like the ATE Dot4 fluid as it does have a higher dry/wet boiling point to the OEM fluid and comes in two different colours so you can tell when the new fluid has reached the caliper being bled.
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Baza, spot on. Got my 5's and 5.1's the wrong way round.

In mitigation I'll say my Harley days were a long time ago.
 
At least you had one ! The best I could muster was a Matchless 650 twin ( Now showing my age) although if I kept it I guess it would be worth a bob or two now.
 
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