Late 180 Rear Brake System Bleed

That's good to know Piet. I may even give the 5.1 a go next time I change out the fluids. Seems slightly less toxic than dot4 if it's easier on paint work
 
Lots of chatter on the Bevelhead site about using Dot 5. When it first arrived there were major issues with seal swelling. They love it now, but I think a complete cleanout of Dot 4 is needed. Its funny how these things do a total swop over the years.
 
Vince said:
Lots of chatter on the Bevelhead site about using Dot 5. When it first arrived there were major issues with seal swelling. They love it now, but I think a complete cleanout of Dot 4 is needed. Its funny how these things do a total swop over the years.
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Like unleaded fuel.
And ethanol added fuel soon  :D

Paul
 
In the bicycle world, there's either DOT or 'mineral'. DOT for me is a pain in the arse, mineral just seems easier, particularly when it spills. Whether psychological or not - the fact that it's more benign means we hate DOT because it's not.

I don't know what sort of temps bicycle and moto brake fluids have to tolerate but it'd be great if they could come up with effective mineral fluiud for motos.
 
Vince said:
Lots of chatter on the Bevelhead site about using Dot 5. When it first arrived there were major issues with seal swelling. They love it now, but I think a complete cleanout of Dot 4 is needed.
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You've got, Vince.  there's nowt wrong with DOT 5.  In fact, like Piet, I find it 's kinder on seals than glycol based stuff like DOT 4, most probably because it isn't hygroscopic.  Used in my Sunbeam Alpine for 15 years, never had to touch it.

But you mustn't let it be contaminated in any way by any residual DOT 4.  If you do, the seals swell up straightaway.

So that means a complete seal change, a complete change of brake lines, and the master cylinder and calipers cleaned and dried like you've never cleaned and dried anything before!  Or even better, simply replaced.

So in practice, best done during a rebuild.  When people try to use it in place of DOT 4 as part of a servicing operation, it always ends in tears ...
 
I think KTM uses Mineral oil in their Hydro clutches.
Quote from another site.

Unless they have changed since I had a ktm back in 02, you could use the stuff Magura use in their MTB brakes, think they called it Magura Blood. Just DONT use normal brake fluid, seals don't last 5 minutes.

Also used mineral-based suspension fluid in the past.
End Quote.


This question is from me.

The highest temperature rated Mineral Oil I have used was what was recommended in the Automatic Transmission on the Husquvana Automatic Dirtbike, that is Esso Univus J26. I have used Ohlins 2.5wt suspension fluid can be used in a pinch, very high heat tolerant fluid or oil. Very very hard to find. Is it the heat generated in braking systems that mandate Brake fluid only?


 
Vince, I think it is actually the capability of brake fluids to keep water in solution why they are used in brake systems (even DOT 5 does it AFAIK). The water content will cause the boiling point to drop, but never free droplets of water are in the system. If you have oil in the system, any water inside the system will not mix with the oil, and even worse, the water will, by gravity and time, handed through down to the lowest point of the system, wich is usually just behind the brake pistons, where it will accumulate with time. Boiling point of water is 100?C, one hard braking and the brake will be gone. Freezing would be an issue, too, as well as corrosion. Viscosity could be an issue as well. Hydraulic bicycle brakes filled with oil are designed in a way to work somehow around those issues, and for the remaining risk they just don't give a shit, no DOT is having an eye on their product, and in case the shit hits the fan it will be end user failure anyway. Some manufacturers of hydraulic bicycle brakes like AVID prefer to use DOT4 fluids in their systems BTW, probably for a reason.

Regards,
Stefan






 
Yep, as mentioned, DOT5 can ruin your day...

I was an early adopter of DOT5 synth and it did indeed bugger up the seals in my Jota. I cleaned the system out well before filling with DOT5, but it all went tits up anyway.  Obviously old seals were impregnated with DOT4. The reaction was quite unexpected and impressive, within a day or so it was all locked up tight.

The whole system was then re-sealed and filled with ATE SL6 DOT4, which I have stuck with ever since. When the tin runs out, 5.1 will be next.

 
Hi Paul
I was just about to say that 5.1 is OK to use with Dot4 due to them both being glycol-based brake fluids.
5.1 has an higher boiling point basically.

Andy
 
Gravelroad said:
Some manufacturers of hydraulic bicycle brakes like AVID prefer to use DOT4 fluids in their systems BTW, probably for a reason.

Regards,
Stefan
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And Shimano, arguably the largest producer of bicycle brakes uses mineral oil. I guess both function fine when correctly employed.
 
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