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Shimano 105 brake bleed questions

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Shimano 105 brake bleed questions

Old 06-15-21, 07:53 AM
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GBK233
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Shimano 105 brake bleed questions

Time to bleed the Shimano hydraulic brakes on my Giant Defy…as my levers have a bit more travel than I’d like.

Bike has only about 500 miles on it, so doubtful I’ll need to completely flush the system. Probably just going to have to fill the brake bleed cup….and flick the levers repeatedly to expel air bubbles. Tons of cheap brake bleed kits on Amazon…so need some advice of what kits are good and what ones to avoid.

Do I need Shimano branded mineral oil or can I simply use the Magura mineral oil I use for the hydraulic clutch on my motorcycle?
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Old 06-15-21, 09:05 AM
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Before you even go that far, I'd just orient the bike so that the lines are running uphill, from the caliper to levers, and without any "traps," give it some vigorous lever flicks and maybe some tapping on any exposed areas of the brake line.

Bubbles in the reservoirs aren't a problem, it's just a problem when the bubbles get between the master cylinder and the calipers, so if you can coax those bubbles up, you should be fine. IOW, unless something is very wrong, there shouldn't be significantly more air in the system than was there when you bought it 500 miles ago - it's just that the air is in a problematic area, now.
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Old 06-15-21, 12:50 PM
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Originally Posted by WhyFi View Post
Before you even go that far, I'd just orient the bike so that the lines are running uphill, from the caliper to levers, and without any "traps," give it some vigorous lever flicks and maybe some tapping on any exposed areas of the brake line.

Bubbles in the reservoirs aren't a problem, it's just a problem when the bubbles get between the master cylinder and the calipers, so if you can coax those bubbles up, you should be fine. IOW, unless something is very wrong, there shouldn't be significantly more air in the system than was there when you bought it 500 miles ago - it's just that the air is in a problematic area, now.

I bought the bike “used”. Had 400 or so miles on it when I bought it and have put over 100 miles on it myself.

No idea what a hydraulic brake lever is supposed to feel like on a bike, but on a motorcycle the brakes engage after about 1/4” of travel.
Haven’t measured but seems as tho I’m getting at least 1/2” or more of travel before I feel the pads engage the rotor. The bike seemingly stops well, but I’m just not used amount of travel before feeling that the brakes are engaging.
Don’t know if maybe pads are set too far away from the rotor….or there is air in the system….or maybe this is just normal for hydraulic bike brakes.
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Old 06-15-21, 12:57 PM
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Air in the lines produces a mushy feel, rather than increased dead travel and then a good bite.
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Old 06-15-21, 12:58 PM
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Originally Posted by MoAlpha View Post
Air in the lines produces a mushy feel, rather than increased dead travel and then a good bite.
no mush…just a lot of dead travel
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Old 06-15-21, 01:06 PM
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Originally Posted by GBK233 View Post
no mush…just a lot of dead travel
I sometimes feel as though my hydro brakes (105 and Ultegra) have too much travel too. There's a screw to adjust the lever position, but I don't think it does anything about the travel. WhyFi would know. Fat new pads definitely help.
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Old 06-15-21, 01:19 PM
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Originally Posted by MoAlpha View Post
I sometimes feel as though my hydro brakes (105 and Ultegra) have too much travel too. There's a screw to adjust the lever position, but I don't think it does anything about the travel. WhyFi would know. Fat new pads definitely help.
My understanding is that DA and Ultegra allow adjustment of brake lever free stroke, but 105 does not. I have the same issue on my Canyon, that over the 1500 miles I've ridden it, the free stroke has increased, especially at the front. I THINK what's happening is that as the pads wear the return springs are still pushing the pistons back to the same place, so the free stroke increases. It's a little disconcerting when I switch from my rim-brake bikes, because I like to keep the pads close to the rim so I get bite with just a little lever travel.

I know people will tell you that disk brakes are supposed to be self adjusting, but I think that's if there's no return spring, like in cars. I should take pictures of the gap when I change pads and then look at it a couple hundred miles later.
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Old 06-15-21, 01:33 PM
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There is going to be a bit of travel before the initial bite; if the lever is firm upon contact and if the wing of your small shift lever isn't overlapping the drops of your bars, I wouldn't worry about it.

And yes, hydro will automatically adjust the gap between the pads and rotors. And no, no way to adjust free stroke on 105.
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Old 06-15-21, 01:39 PM
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Originally Posted by genejockey View Post
My understanding is that DA and Ultegra allow adjustment of brake lever free stroke, but 105 does not. I have the same issue on my Canyon, that over the 1500 miles I've ridden it, the free stroke has increased, especially at the front. I THINK what's happening is that as the pads wear the return springs are still pushing the pistons back to the same place, so the free stroke increases. It's a little disconcerting when I switch from my rim-brake bikes, because I like to keep the pads close to the rim so I get bite with just a little lever travel.

I know people will tell you that disk brakes are supposed to be self adjusting, but I think that's if there's no return spring, like in cars. I should take pictures of the gap when I change pads and then look at it a couple hundred miles later.
Unless the pistons are sticking, the gap should stay consistent throughout the range of pad wear. If you're seeing more lever travel than before, and if the lever isn't really firm, I'd suspect a little bit of air in the lines. Is this one of the stable that gets hung on the wall pretty regularly? Hanging it with the bars down or, heaven forbid, both wheels up, could certainly encourage reservoir bubbles to work in to the lines.
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Old 06-15-21, 03:21 PM
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Originally Posted by WhyFi View Post
Unless the pistons are sticking, the gap should stay consistent throughout the range of pad wear. If you're seeing more lever travel than before, and if the lever isn't really firm, I'd suspect a little bit of air in the lines. Is this one of the stable that gets hung on the wall pretty regularly? Hanging it with the bars down or, heaven forbid, both wheels up, could certainly encourage reservoir bubbles to work in to the lines.
No, the Canyon is the one bike I don't hang up.

No lack of firmness of the lever, no squishiness. Professionally bled a few months ago. Just progressively greater free stroke over time, more obvious with the front than the rear, correlating with wear on the pads.
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Old 06-15-21, 03:30 PM
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Originally Posted by genejockey View Post
No, the Canyon is the one bike I don't hang up.

No lack of firmness of the lever, no squishiness. Professionally bled a few months ago. Just progressively greater free stroke over time, more obvious with the front than the rear, correlating with wear on the pads.
I get that too and it goes away with new pads. Minor thing, but definitely noticeable.
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Old 06-15-21, 03:45 PM
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Originally Posted by genejockey View Post
No, the Canyon is the one bike I don't hang up.

No lack of firmness of the lever, no squishiness. Professionally bled a few months ago. Just progressively greater free stroke over time, more obvious with the front than the rear, correlating with wear on the pads.
Hmm, weird. The rear pads on my Cervelo are nearing their min thickness, as is the rotor - the travel is no greater than when they were new. Lever travel on the Haanjo (RS505s) has been the same for 5 years over multiple sets of pads.
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