Brake Fluid Dot 3, 4 or 5??

**Gontour** · 30th September 2005, 12:08

I am going to change Brake fluid, and have been advised to use Dot3 Fluid rather than the so called higher spec alternatives, because the Dot 3 doesnt 'Boil' when its old, and as a bonus doesnt Strip you paint as effectively as the others should you spill some on paintwork, any comments would be appreciated..........

**Sniper** · 30th September 2005, 12:11

Use the fluid specified in the manual. I would suggest you stay away from DOT5 though.

**bugjuice** · 30th September 2005, 12:15

why stay away from DOT5? I did my brakes with DOT5.1 the other month. fukme, does the bike stop fast now.

DOT5.1 has the higher boiling point. DOT4 is for use on 90% of everything on the road. DOT3..?? Didn't think you could buy that any more... I'd just get DOT4 and replace it every year, cos you don't want 'old' stuff full stop.

I've used DOT5.1 in my bike, to see if I can stop some of the brake fade when I'm giving it a bit of shit in the twisties and track.. But I would happily go back to DOT4 next time..

Who said to use 3 out of curiosity?

**Grinner** · 30th September 2005, 12:20

The following is off the belray web site should answer all your questions.

"Years ago, many road race teams used DOT 5 silicone brake fluid to get higher boiling points than the DOT 3 & 4 brake fluids of that era. DOT 5 silicone is not hygroscopic, meaning it won’t absorb water from the air, so it retains its high boiling point over time. On the other hand DOT 3, 4 and 5.1 brake fluids are glycol based and do absorb water from the air, which then lowers the boiling point. That is why you will see wet and dry boiling points, with the dry boiling points always being higher. Glycol based brake fluids may start out with a fairly high dry boiling point but as they absorb moisture the boiling point decreases. So every time your brakes get really hot and then cool, condensation occurs and moisture is absorbed. That is why it is important to replace your brake fluid regularly. It may seem obvious that DOT 5 silicone is the best choice, but not so. Today most road race teams use DOT 4 or DOT 5.1 glycol based brake fluids because the dry and wet boiling points today are very high and in some cases higher than DOT 5 silicone. The number one reason not to use DOT 5 silicone is a slightly mushy lever or pedal feeling as compared to glycol based brake fluids. This is the nature of the product. Street riders may not feel the difference, but the race teams prefer the precise feeling of glycol. The only motorcycles that I know of rolling off the production line with DOT 5 silicone are Harley-Davidson® and other American made motorcycles; and that is mainly where we sell our Bel-Ray Silicone DOT 5 Brake Fluid. I recommend you stay with the DOT 4 fluid for performance, not to mention the enormous job it is to switch your system over from glycol to silicone. If that job is not done properly, you run the risk of coagulation if remnants of DOT 4 are mixed with DOT 5 silicone."

**Ixion** · 30th September 2005, 14:14

Today most road race teams use DOT 4 or DOT 5.1 glycol based brake fluids

So DOT 5 is silicone , and DOT 5.1 is glycol 9as is DOT 4) ? How silly

**SimJen** · 30th September 2005, 14:22

remember to replace the fluid on a regular basis too.
I replaced my Gixxers the other day and it was the exact same colour as Pepsi Max. I even stored it in a Pepsi Max bottle as I had no other containers......just waiting for someone to drink it now

Put Motul 5.1 in and it feels a lot better.
I'd always go for a higher grade if possible. It won't hurt. I don't think I'd put Dot 3 in it though, as the manual specifies Dot 4.

**Bartman10** · 30th September 2005, 14:36

Brake fluids are backwards compatible.

So, if your manual says dot 3, then anything with a higher number should work. Don't mix brake fluids. I always drain and replace all the fluid in the system.

If there has been any polymerisation (ie you see solid snotty loking bits in your fluid) you will need to clean the entire system out. This might mean taking the calipers and master cylinder to bits if its very bad.

Replace you brake fluid one a year and you will not have these problems.

I find Spectrol very good. Its about $18 per bottle. Buy a new bottle every year when you replace the fluid. Don't use stuff thats been sitting in a bottle with a broken seal for a long time.

All the best.