Brake fluid

[tomo]

I've seen people talk about Dot 4 and Dot 5 brake fluid.  Is Dot 5 worth the extra cost ?  It says its for cars with ABS so does that mean I don't need it ?

[jamie]

I have used dot 4 in my cosworth sapphire for 10 years with ABS and it's been fine

I remember that when I got my kit from westy there was a slip of paper in a booklet stating that they did not recommend silicon brake fliud I think it was somthing about water absorbtion

but if you can afford dot 5 i dont think it will harm?

[chazpowerslide]

Dot 5 has a higher temperature rating than dot 4 (about 300 deg c boiling point versus about 260 for the dot 4). Dot 5 is also reputed not to eat your paintwork as well. Assuming that your brakes are not on the marginal side to start with (ie you are using quality pads, the system is in good nick and they are big enough to do the job yoyr asking them to do) dot 4 should be sufficiant as you should not be generating the temperatures needed to boil the fluid. If your fluid is old it will have absorbed moisture and this can reduce the boiling point apparantly by up to a third, it's good practice to flush the system annually with fresh fluid. If you are hard on your stoppers and you are getting fade (track days are good for stressing standard brakes in this way) you may want to move to dot 5 as a precaution as the temps are higher, but in my experence it's normally the pads that give out prior to the fluid boiling. Incidently I've been using silocone fluid in my Kawasaki ZZR1100 that's dot 5, paint work friendly and does not absorb moistue.