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Discussion Starter #1
What's the difference between DOT4 and DOT5? My manual says use only DOT4, but I've already got some DOT5. I know you can't use sillicone fluid in ABS-equipped rigs, is it okay for bikes? The DOT5 that I have says that it's sillicone. Thanks for the help. :cheers
 

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second chimp in space
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You can use it, but you have to completely purge your system of DOT4. this might mean rebuilding the calipers with new seals and replacing the hoses (they soak the stuff up). In general I hear DOT5 is better in that it doesn't pick up water as much and lasts longer. But it's chemically incompatible with DOT4, so don't even think of mixing them.
 

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the chemical combination causes a break down of the thick fluid that holds the temp will explode if mixed ps just cyclinders
 

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Discussion Starter #5
It'll work with a good flush. But it won't work well whether you follow enos' directions or mine. Expect a spongy feel even when well bled.
Is that just the nature of the sillicone? A bit spongy? I used dot5 in my buddy's system and his brakes feel nice and firm (new hoses and completely flushed system), though they do feel like they actually get stiffer (like the fluid swells) when they get hot, is this to be expected? I kinda like the idea of the fluid expanding with heat, makes things feel fade-proof.
 

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DOT 5 has a greater propensity for absorbing air than DOT4 which can make it slightly compressible and spongy feeling over time. It does not absorb water which is why it uses silicon to inhibit brake system corrosion. Because it does not absorb water there is a remote chance that if you got water in you calipers it would flash and vapor lock at 212 F.

DOT3/4 and DOT 5 do not mix. No explosions just an oil/water type of thing.

If the manual says DOT 4 I'd probably use DOT 4.
 

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My fanclub is here
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I went with dot 5.1. Fully compatible with 3 and 4 and a much higher boiling point. And here is the brainy blurb.

LONG LIFE FORMULA : the high wet boiling point (185°c/365°F), superior to DOT 4 and DOT 3 fluids enables to use this product longer.
SPECIALLY DESIGNED TO ANTI-LOCKING BRAKE SYSTEM (ABS) : its viscosity (820 centipoises at -40°c / -40°F) lower than DOT 4 and DOT 3 brake fluids, allows MOTUL BRAKE FLUID DOT 5.1 an easier fluid circulation in micro-valves of anti-locking systems.
PERFECTLY NEUTRAL WITH SEALS USED IN BRAKING SYSTEMS. ANTI-CORROSION.

STANDARDS : FMVSS 116 DOT 5.1 NON SILICONE BASE & DOT 4 & DOT 3
SAE J 1703
 
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