So I have a Gary Fisher Tassajara MTB three weeks old that I bought to perhaps do some Xterra-type racing next year. I’ve been pounding the hills hard and using the hydraulic brakes a lot on some fairly serious drops. This morning, after about 18 miles in, my brake handles go all the way to the handle bars and I almost have the “Flintstone” it to the bottom of the gulley. I’ll bring it to the dealer tomorrow, but what’s the diagnosis here folks? Air in the brake lines? It’s my first experience with hydraulic discs and admittedly I’m a bit green on them.
First off…your bike isn’t built for big drops (your fork will blow up), so don’t tell the bike shop about that part.
I’m guessing you have Hayes Nines on the bike. Typically, a lever to a bar means there is not enough pressure in the line…which could mean either a leak or air.
However, if you’re been crunching the brakes…it might be within the tolerance of break-in (pads/lines). So, there is a little adjustment screw where the line goes into the lever (that doesn’t really explain it well…so look on the Hayes site). Give that a shot before taking the bike in…
Good luck.
So I have a Gary Fisher Tassajara MTB three weeks old that I bought to perhaps do some Xterra-type racing next year. I’ve been pounding the hills hard and using the hydraulic brakes a lot on some fairly serious drops. This morning, after about 18 miles in, my brake handles go all the way to the handle bars and I almost have the “Flintstone” it to the bottom of the gulley. I’ll bring it to the dealer tomorrow, but what’s the diagnosis here folks? Air in the brake lines? It’s my first experience with hydraulic discs and admittedly I’m a bit green on them.
You most likely have an air bubble in your brake lines. Most of the time you won’t notice it because the air is safely living in your brake fluid reservoir (next to the levers). On steep, rough descents, the bubble can travel down into your brake lines. The brake lever goes all the way to the bar because you are just compressing the air bubble (air compresses easily, while brake fluid does not). The solution is to bleed your brakes. Your shop should do this because it’s their fault the bubble was there in the first place.
As a temporary measure in this situation, I’ve had success tapping the brake lines with my hand to get the bubble to travel back up into the reservoir. This at least gets your brakes working again until the next bone-rattling descent…
If both front and rear brakes failed at the same time, it might not be an air bubble. Instead, it could be brake fade, which can occur when they get too hot. Not much you can do about this except to stay off the brakes until they cool down a bit.
The third possibility is that you have a leak in the system. This could be your fault if you crashed and damaged something, or (more likely) a defect or improper setup. The shop should take care of you in either of the latter two cases.
… after about 18 miles in, my brake handles go all the way to the handle bar …
“handles” as in both?! If so that’s odd because they are two independent systems. If one, then what the others said 
Yes, my friend. Both front and back brakes can be put to the ‘floor’ at this point. It’s just like cable stretch sans the cables.
I don’t want to mislead anyone- I’m not dropping 15 footers, just a lot of rocks and roots on the way down 35-40* declines with a lot of bumpty bumpty bumpty on the way down. Lots of sharp turns at bottoms of these decents make braking a necessary evil. Otherwise I would eat bark.
Hayes Sole XC hydraulic disc brakes w/6" rotor
.
Hmmm… do you store your bike upside down (i.e. hang from the ceiling) or was it upside down for any length of time before this ride?
Other than this sweet back flip I did on it today, no. It remains perfectly upright all the time. Just checked out Hayes site on it and it reads as follows:
- I have no braking power, what is wrong?
There are 2 things that can cause a problem with braking power. The first is a problem with the hydraulic system. This will be evident when you squeeze the lever and it goes to the handlebars. This could be caused by air in the system or by a leak. To fix this, bleed the system or repair the leak and bleed the system. No power could also be caused by the pads being contaminated with oil. Once the pads are contaminated, there is no way to clean them. To fix this, replace the pads, and clean the disc with alcohol.
You overhateated your brakes. It’s actually quite common in the endurance mtn. bike races I do. The question is, how badly did you overheat them?
At a certain point, the friction you are applying to your rotors is so great that they cannot dissipate the resultant heat, and they begin to boil the hydraulic fluid in your caliper bodies, and even the brake lines. Depending on the type of reservoir system you have, and how hot the fluid has gotten, the reservoir compensates for the expansion of the fluid by expanding or blowing fluid out through a safety valve - or by catastrophically blowing fluid out through the seals.
What does this mean for your situation?
If you didn’t blow any seals, and just had “boil bubbles” in your line, you may not have to do anything; if your brakes are working fine right now, don’t worry about it, and learn to brake less on the descents.
If your brakes are still f***ed, either you have boiled air into the lines, and need to bleed and feed them, or you have blown the seals, and need to replace them, and then bleed and feed. The first step in either case is to bleed and feed, and if this doesn’t solve the problem, you then do a seal job.
.
Don’t Hayes brakes use Dot 4 fluid? And doesn’t Dot 4 require a boiling point exceeding 450 degrees farenheit? I’m just guessing but I think that’s correct, and if so I doubt that he could generate that much heat on a XC bike.
assuming no leaks in the lines bleed the brakes front and back. that should fix pretty much any problem that is or isn’t there. Your brakes are probably self adjusting so it’s not pad wear and at least with my XTR disks it’s pretty damn hard to heat up my brakes no matter what type of terrain I’m riding. Are you a big guy? More weight equals more work for the brakes. We did about 4,000 feet of climbing today and one of the climbs, maybe 1,300 ft or so is a good 13-17% grade or so up for around 4-5 miles. It’s all turns the whole way down so you’re riding your brakes like crazy, never had a problem here yet. I can see brake overheating on a big heavy downhill bike but on an XC bike where you’re probably on and off the brakes again and not slamming down on them hard going 40-5mph to make a turn, I wouldn’t think they’d overheat. I’m not an expert though, but I’d agree with the air bubble problem so bleed them out and you should be good. Never store your bike upside down and make sure your resevoirs are fully topped off. Good luck!
You are correct about the DOT fluid, but you are miles off base on the heat generation.
You can get a bicycle disc brake rotor so hot that you kill the temper, cherry red from edge to edge (I’ve done it.) I have also boiled out the reservoir on a Hayes, blown seals and all…
Seriously, this is really common at races like the TransAlp and TransRockies, where you are doing technical descents that can last 15, 20, even 30 minutes… It’s a bit of an accomplishment to do it on your typical garden variety descent, but you can…
.
.
You are correct about the DOT fluid, but you are miles off base on the heat generation.
You can get a bicycle disc brake rotor so hot that you kill the temper, cherry red from edge to edge (I’ve done it.) I have also boiled out the reservoir on a Hayes, blown seals and all…
Seriously, this is really common at races like the TransAlp and TransRockies, where you are doing technical descents that can last 15, 20, even 30 minutes… It’s a bit of an accomplishment to do it on your typical garden variety descent, but you can…
Man… work on your descending skills… you’re using your brakes too much
"Man… work on your descending skills… you’re using your brakes too much "
Yup - I do. Then again, when I did this, I was riding TransRockies with a 1-legged guy, and we were passing (literally) dozens of people on the descents. It took a while to learn how to do that without braking :0)
- Oh - I also had a dragging pad from a slightly bent rotor, which is pretty common, but on long descents it means that your brakes never have a chance to cool, even when you get off them.
Good learning experience, actually; I ride with much longer lever throw/greater pad-rotor distance now, to keep drag down as much as possible, even when the cylinder expands from heat. 8000 feet of descending with no rear brake teaches you stuff like that…
.
with a 1-legged guy
Is that the same guy that did Xterra? Have you ever clipped one foot out and tried to climb a technical climb with one foot? How about a technical descent? Amazing, is all I have to say about that!!!
I was riding with a guy named Brett Wolfe - we did Trans Rockies and Trans Alp together, and he has also done Cape Epic, La Ruta, and multiple 24 hour solo races. He finishes top 20 in Sport Class Mtn. bike races, and rides without a prosthetic.
Brett is a legend in Europe - cover story in Bike (the German mag) later this year. He just “retired” from racing to go back to school/spend time with his family.
Get this - his 1 hour wattage hovers around 300 watts. With 1 leg.
.
sure you’re not talking about “one armed Willy?” The guy with the Fox Shox mechanical arm. He’s damn amazing, don’t know how he rides some of the technical downhill stuff. Racing near him at Big Bear last year, as we get to the top of a climb he hops off, pulls off his arm and dumps the sweat out of the little cup that his arm fits into, retightens it and goes in like 15 sec…
Then I see him out here for the Honolulu Tri earlier this year. I’m talking to him as we kinda know each other from all the Xterra races, well I think he remembered my girlfriend more than me;) We had this 8m trail run the Saturday before the tri, it’s a killer 8miler with lots of hills and roots, really beats you up. So he figures he’s in hawaii he might as well check out the trails. A fun run turns into a race to the finish as he realizes that he might be able to win the race and he hammers the whole run the day before the tri. Then he raced Sunday!
There is no fluid coming out of the valve or the seals. It’s a clean as day 1. To another’s point, I’m feathering the brakes on the way down, not trying to stop a steam train run away on the tracks. Brakes still go to the bars, so I’m not so sure I boiled the lines. I think the bleed and feed route is going to be the way to go on this one. Thanks very much for your reply and input!
Your assessment is exactly on. I’m 205 lbs and max speed down hills on the trails are in the 15-18 mph range- too many turns to risk broken bones going any faster. Average speed for the trip is 10 mph given the climbing. I’m in Michigan, so no mountains are being climbed and certainly no 1,300 ft climbs at a time. I did not know about not storing it upside down, which I never have done, but one would have thought the LBS would have warned me about that, eh? Learn something new every day!
I did not know about not storing it upside down, which I never have done, but one would have thought the LBS would have warned me about that, eh? Learn something new every day!
Storing your bike upside down is not a problem. If you have air in your system, storing your bike upside down may allow the air to travel from your brake fluid reservoirs into your brake lines (as mentioned earlier). Then you will notice that your brakes don’t work. But storing the bike upside down is not the source of the problem…it just reveals it.
Bleed the brakes properly and you should not have any issues, whether you store your bike upside down or not.
Note: if you do store your bike upside down and notice that your brakes don’t work, it’s not the end of the world. Tap the brake lines with your fingers (to get the air bubbles back up into the reservoir) and your brakes should work again in a few minutes. You’ll still need to bleed them to fix the problem permanently, though.