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DOT 5.1


kosmonooit
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Anyone know where I can get hold of some DOT 5.1 Brake fluid here in Jozi to bleed for my lovely new Hope Tech M4 brakes? This is what they specify to use, and from what I have read one cant just use DOT 4 (which is the norm here) unless you flush the 5.1 first. And there might be issues with seals. DOT 5 is another story all together.

So it would be easier if I could source some DOT 5.1 locally but motor spares places here never heard of it as have a few LBS that I have called. ..? "DOT what?"

Thanks in advance.

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You can buy DOT 5.1 from any motorcycle spares dealer.

 

I bought mine from Mosskays in Blairgowrie.

 

Full Throttle in Cresta would also stock.

 

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sort of hijack but related* why must you flush it first? I have 5.1 in my Elixirs but have 4 for when I need to rebleed for whatever reason.

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Can't really answer you on that one Mutt but I suppose its like mixing Whisky and Brandy in the same glass. Both are alcoholic spirits but......

 

 

 

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After doing some crawling on the interweb, that was the advice from more than one source (incl. some mtb forums)? not to mix the two: flush first. Maybe its not an issue but I'd rather go 'by the book' as it were, as much as most of the information on the net can be regarded as 'fact' but for lack of other sources or references - I will stick to the side of caution.

There is possible some chemical incompatibility that can damage seals though it seems the bigger issue was incompatibility between 5 and 4 or 5 and 5.1 ?

5.1 seems to have a higher boiling point than 4, but is that really a big deal for a mtb brake lol.?

kosmonooit2010-03-23 08:07:45

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I suppose when in doubt follow popular consensus. It is an expensive thing to wreck.

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Anyone know where I can get hold of some DOT 5.1 Brake fluid here in Jozi to bleed for my lovely new Hope Tech M4 brakes? This is what they specify to use' date=' and from what I have read one cant just use DOT 4 (which is the norm here) unless you flush the 5.1 first. And there might be issues with seals. DOT 5 is another story all together.

So it would be easier if I could source some DOT 5.1 locally but motor spares places here never heard of it as have a few LBS that I have called. ..  "DOT what?"

Thanks in advance.

[/quote']

I buy from Mossakys - they usually can't find it, but if you look on the shelves yourself, you'll find it...

 

You can use DOT4 in most bike brake systems (definitely Avid is OK). The problem is that DOT4 boils at 230degC and DOT5.1 at 270degC. I have boiled my brakes twice on DOT4, and since switching to 5.1 have not done so again...

 

You are quite correct in stating you should not mix DOT4 and 5.1 (Motul state their 5.1 is "compatible" with 4, but I wouldn't try it, personally). If you're doing a fluid change, you'll be flushing anyway, so moving from one to the other won't be an issue...

 

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I think Dot 4 is mineral based and the higher heat range stuff (5 plus) is synthetic so it would not mix that well.

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5.1 seems to have a higher boiling point than 4' date=' but is that really a big deal for a mtb brake lol. 

[/quote']

I've given my opinion above! Wink

 

Going down the Gamkasberg in the Epic without front brakes is a experience I do not wish to relive!!! I also managed to boil DOT4 going down the Sani Pass and lost my front brakes...

 

Maybe I'm a little too heavy handed... LOL

 

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Thanks again - got a 500ml at Mosskays today, dont think I need it all but always best to err on the side of excess beside the dont sell smaller. It was about R120

Also curious to know how do you know you boiling ur brake fluid? Doed this blow seals and thus you loose your brakes?

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Umm, if you boil your brake fluid GUARANTEED you will know.  OuchOuchOuchOuchOuch

 

Boiling fluid creates an air bubble which you can compress - so when you grab for the brake you will find there is suddenly no resistance and no slowing down..

 

All you have to do is wait a bit until the fluid cools again, the trouble is it's not nice to wait when you're already going down the hill at 75kph.

 

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I boiled the brakes on my Mille (Aprilia 1000cc Sportbike) once and it then caused the brake lines to soften and swell as soon as the pressure built whilst grabbing a handfull of Brembos. Not funny - switched to braided hoses straight afterwards.

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Just as well I ordered the braided lines option with the new Hope brakes I got then, besides looking the business .....

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