What type of brake fluid?

[gossie]

DOT 4.
Don’t put DOT 5 in it. It’s silicone fluid but only if the complete system is properly cleaned out.
We used it when rebuilding old cars with all new everything.
It does not take in water that’s important in these old classics that get little use.
Also using DOT 4 or 5 that will take in water from the atmosphere so important to flush your brakes every two years or you may get serious fade

 

[Deuce]

Dot 3 is old and you can just use dot 4 in place of it.

Dot 5 is a completely different kettle of fish and not compatible in anyway whatsoever. It has a higher boiling point. But requires less water contamination for it to be considered wet and therefore require replacing. Say 1 Yr interval instead of 2yr.

A system that is switched between types of fluid (4 to 5 for example) will have seals swell or shrink, leak, and basically become useless. All rubber seals would need replacing, and all lines flushed and metal surfaces cleaned.

Dot5.1 also exists and is an upgraded version of dot4.

For a stock vt I would use any cheap dot4, and anything that will see track time, use high performance dot4 (penrite offers one for example)

In summary: DOT5 ONLY FOR DOT5 SPECIFIED VEHICLES

 

[losh1971]

It gets confusing because dot 4 used to not be compatible I'm lead to believe but dot 4.1 was ok, I'm also lead to believe. Some dot 5s are compatible with for 4. I had some in the bike. Rockoil make one that I used and it was compatible as it wasn't silicone based. It caused no issues on the bike and the bike brakes get extremely hot, when you come from 170kph to 10kph in under 80m.