15 replies to this topic

[rally1380]

Bleeding and rebuilding my wifes mountain bike brakes (Avid Elix R) and going to replace all the fluid.

 

Is bike brake fluid any different to automotive stuff??

 

Bike stuff is expensive for the small amount you get, and i've got a big bottle of decent Castrol high performance stuff for my car....can it be used?

[Gremlin]

It will say mineral or DOT4 on the resovoir somewhere, if it says mineral you cannot use your castrol stuff (likely to be DOT4) as the seals won't like it

[creakyjaws5533]

http://forums.mtbr.c...-cr-775641.html

[rally1380]

It will say mineral or DOT4 on the resovoir somewhere, if it says mineral you cannot use your castrol stuff (likely to be DOT4) as the seals won't like it

 

It says DOT 4 or DOT 5.1, but wasn't sure if mountainbike fluid was specific to them or if brake fluid was similar throughout.  The Castrol stuff is DOT 4 performance and i've never got it to boil on my rally car so figured may as well use that seeing as i've only just opened a container.

[creakyjaws5533]

Most take mineral oil should say on the resivoir cap on the brake lever

[samsfern]

I use dot 4 car stuff in my downhill mtb. Works fine.

[RossKnight]

yeh dot 4 is alright

[glyn]

I like the way your trying it out on your wife's bike 1st, top marks.

['Chop']

I have been in the trade for over 20 years (for my sins) . Only use dot 4 or 5.1 NOT mineral.

 

The mineral will attack the seals leading to a brake failure.

 

You need to bleed the system by repeatedly pumping the fluid from caliper to lever and vice versa. Use 2 syringes for this. If you have got the available spare cash, buy the bleed kit. The cheaper 'home' use is fine, but I use the pro workshop one- it's just a little quicker.

 

Make sure you dont round the torx bolts on the lever and caliper, they can be real swines.

 

If you only have one syringe available. it's just possible to bleed the system... Refill the system from top to bottom. Refit the top torx bolt (lever) and then remove the pads and pressurize the system from the bottom (the pistons will be forced out part way). Open the top torx bolt and a little air will bleed out the top (lightly tap the lever). Close the system. and with a plastic tyre lever push the pistons back into the caliper (otherwise the brake will feel spongey) and refit the pads. OK, so this isn't anywhere ideal, but it will give you a brake..... It'll get you out of trouble....but use the double syringe technique for a proper job.

 

Use 5.1 if you can, it's less hydroscopic than dot 4.

 

Best of luck!

 

Andy

['Chop']

Oh..... and bike stuff is the same as automotive stuff.....

 

It's just that in the bike trade we sell tiny pots of overpriced fluids!!!

 

Get your self a 500ml or 1 litre bottle from a car/ motorbike shop....

 

and make sure you keep the lid on.....

 

and DON'T shake the bottle (which is what a lot of my customers do just after they buy a bottle!!)

 

I use the 1 litre bottles as I get through a lot of the stuff.

[Black.Ghost]

Chop - many hydraulic brakes for bikes say Mineral Oil on them. Why would the manufacturers put that on if they could damage the seals and lead to brake failure?

[Gremlin]

He means some circuits are designed for mineral oil, the seals included, so putting normal DOT 4 in will cause damage

['Chop']

He means some circuits are designed for mineral oil, the seals included, so putting normal DOT 4 in will cause damage

Exactly that!

[Domneon]

I just bled the front brake on my mountain bike, Avid Elixir 3's and they are nice and easy to do really. Syringe at each end at kind of draw fluid through the system which pushes the bubbles out.

 

Avid are a bit annoying in that there is only enough fluid for them to work with no reservoir 

[nicklouse]

OP you do have the bleed kit?

If not you can make your own up but with it they are so easy to bleed.

And as stated MTB DOT is the same as car DOT.