[the desmondo]

I'm a total beginner in bike maintenance, especially when it comes to brakes. Could anyone tell me why brakes for downhill bikes need to be bled so often, or is this a big misconception that I have? Why is it that cars brakes don't need to bled as often as bike brakes?

 

[marshalolson]

1. dh brakes use WAY smaller MC's and pictons than a car (or moto), and displace much less fluid so they are much more sensitive to small air bubbles.

2. good brakes do not need to be bled often.

3. most modern brake systems can just be burped (ie pull the top cap, pump u the system, release the air bubbles, re fill the MC and close), not fully bled.

 

[Sandwich]

PS brake systems on cars do need to be bled often. People just don't do it.

I forget exactly what the schedule is, but fluid should be completely bled and replaced at some silly interval like 30k miles....but people rarely if ever pay attention to that, and most don't race their cars to within 10% of their possible performance, as often happens with dh bikes.

 

[slowitdown]

it always looks to me like people who talk about needing to bleed often are people who don't know how to bleed properly. in other words, if you do a poor job of bleeding a brake you can actually make it worse, which means you have to bleed it again, which is another opportunity to screw up the bleed.

it seems most who bleed a lot suffer this problem, and they'd probably be better off learning how to bleed a brake, or letting someone else do it for them.

example: I needed to install a different pipe/hose/line on my Formula K24. I measured the line, cut it, installed it, bled the brake without reading the Formula bleed instructions. seemed to go okay. then on the first ride it got spongy. went home, ate, re-bled the brake, this time following the instructions perfectly, VOILA! perfect performance. if I'd just gone on the first no-instrxns bleed I'd say the Formulas suck but after reading and following the instrxns I have to say that it was me who sucked.

 

[Uncle Cliffy]

OP- What kind of brake are you running?

 

[GTIgor]

PS brake systems on cars do need to be bled often. People just don't do it.

I forget exactly what the schedule is, but fluid should be completely bled and replaced at some silly interval like 30k miles....but people rarely if ever pay attention to that, and most don't race their cars to within 10% of their possible performance, as often happens with dh bikes.

the deal is in the propety of brake fluid to absorb water from air - thus the procedure is a must every year - no difference bike or car

even an once opened bottle of DOT fluid looses its temperature qualities with time

 

[IH8Rice]

it always looks to me like people who talk about needing to bleed often are people who don't know how to bleed properly. in other words, if you do a poor job of bleeding a brake you can actually make it worse, which means you have to bleed it again, which is another opportunity to screw up the bleed.

it seems most who bleed a lot suffer this problem, and they'd probably be better off learning how to bleed a brake, or letting someone else do it for them.

example: I needed to install a different pipe/hose/line on my Formula K24. I measured the line, cut it, installed it, bled the brake without reading the Formula bleed instructions. seemed to go okay. then on the first ride it got spongy. went home, ate, re-bled the brake, this time following the instructions perfectly, VOILA! perfect performance. if I'd just gone on the first no-instrxns bleed I'd say the Formulas suck but after reading and following the instrxns I have to say that it was me who sucked.

bingo