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Thread: disc brake ?

  1. #1
    Senior Member ClarkinHawaii's Avatar
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    disc brake ?

    OK, so I just put a new Avid BB7 road disc brake on the front wheel of my touring bike. I attached the rotor that came with the brake onto a brand new wheel that I have just built (my first, from scratch!).

    Naturally I was shocked and dismayed to note that the brake has almost no stopping power; but after reading up on the subject, I anticipate this situation will improve . So if I live through the break-in period, I'll be ok.

    I also purchased a new Shimano sm-rt64 rotor (centerlock) to use with the front wheel of the other wheelset I use with this bike.

    Here's the questions:

    1. Since i will be using 2 different front wheels with 2 different front rotors, should I purchase another set of brake pads, and keep the 2 rotor/padsets separated? (from what I've read, it sounds like rotor and padset get married and introduction of another rotor screws things up)

    2. What is the most effective brake padset for the Avid BB7 with 160 rotor? (to be used as an eventual replacement for the oem padset and, if recommended, the 2nd set of pads to be used only with the 2nd rotor)

    Thank you!

  2. #2
    Senior Member BCRider's Avatar
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    The BB-7 has only one moving pad as I recall. A big part of setting the caliper up is to retract the fixed pad and use the cup and ball washers to aid in aligning the caliper so that the pads are as close as possible to being in perfect alignment with the rotor.

    The steps I use for mechanical disc calipers is to line things up decently by eye and pinch the caliper bolts down semi snug. Then grab the brake lever firmly so the brake is fully on. Now loosen the caliper mount bolts which have the cup and ball washer and give them a bit of a wiggle to let the cup and ball washers move until the caliper is aligned with the rotor. This wiggling aligns the inner cup and ball washers but not the upper ones. To do those twiddle the caliper bolt down against the washer stack and then retract it using your fingers to spin the allen key a number of times. This locking and unlocking should jiggle the washers to a better seating. Finally pinch the allen bolts down and tighten. NOW you can finally let go of the brake lever. When done well the caliper and pads should line up with the rotor quite well. But you will likely still need to adjust the fixed pad towards the rotor a bit. Index it in until it lightly scuffs the rotor when you spin the wheel. If it only scuffs in one spot gently flex the rotor in that area so it bends very slightly away from the fixed pad. Adjust the fixed pad inwards again and keep tweaking the rotor in very small amounts until it scuffs overall equally. Back the fixed pad off one click. If it still rubs very lightly live with it. It'll soon go away.

    Only after all that is it time to go and "break in" your new pads. You'll want to find a long and fairly steep hill and really heat the snot out of them. Then after thay cool they should be fine. You'll very likely need to advance the fixed pad by a click or two to make up for the wear from the breakin.

    With the one side movement calipers such as the BB-7 mechanicals it's very important to keep that fixed side adjusted close to the rotor even if it scuffs very lightly when first adjusted. If it's too far away then you have to first bend the rotor over to contact the fixed pad and then force it into an "S"shape. All of this takes lever effort that goes towards bending the rotor instead of stopping you and the bike.
    Model airplanes are cool too!.....

  3. #3
    17yrold in 64yrold body
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    +1 on the breakin. I followed Avid's instructions to set up my Road BB7--loosen the mounting bolts, then tighten the adjusters (red knobs both sides of caliper) until you have 1/3 spacing on the inside (fixed) and 2/3 space on the outside (moving pad). Tighten the bolts, then back off the adjusters until you have just a little 'scuffing' of pads on rotor. Then ride hard to break in. Now adjust for minimum spacing without drag. Now you should be good to go!

    BTW--the oem pads had a fair amount of squeal, so I got some Kool Stops, and now they do not sound 'like a pig under a gate'!
    Attached Images Attached Images

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    Senior Member ClarkinHawaii's Avatar
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    Quote Originally Posted by BCRider View Post
    The BB-7 has only one moving pad as I recall. A big part of setting the caliper up is to retract the fixed pad and use the cup and ball washers to aid in aligning the caliper so that the pads are as close as possible to being in perfect alignment with the rotor.

    The steps I use for mechanical disc calipers is to line things up decently by eye and pinch the caliper bolts down semi snug. Then grab the brake lever firmly so the brake is fully on. Now loosen the caliper mount bolts which have the cup and ball washer and give them a bit of a wiggle to let the cup and ball washers move until the caliper is aligned with the rotor. This wiggling aligns the inner cup and ball washers but not the upper ones. To do those twiddle the caliper bolt down against the washer stack and then retract it using your fingers to spin the allen key a number of times. This locking and unlocking should jiggle the washers to a better seating. Finally pinch the allen bolts down and tighten. NOW you can finally let go of the brake lever. When done well the caliper and pads should line up with the rotor quite well. But you will likely still need to adjust the fixed pad towards the rotor a bit. Index it in until it lightly scuffs the rotor when you spin the wheel. If it only scuffs in one spot gently flex the rotor in that area so it bends very slightly away from the fixed pad. Adjust the fixed pad inwards again and keep tweaking the rotor in very small amounts until it scuffs overall equally. Back the fixed pad off one click. If it still rubs very lightly live with it. It'll soon go away.

    Only after all that is it time to go and "break in" your new pads. You'll want to find a long and fairly steep hill and really heat the snot out of them. Then after thay cool they should be fine. You'll very likely need to advance the fixed pad by a click or two to make up for the wear from the breakin.

    With the one side movement calipers such as the BB-7 mechanicals it's very important to keep that fixed side adjusted close to the rotor even if it scuffs very lightly when first adjusted. If it's too far away then you have to first bend the rotor over to contact the fixed pad and then force it into an "S"shape. All of this takes lever effort that goes towards bending the rotor instead of stopping you and the bike.
    WOW--Comprehensive! Thank you. I just followed the instructions for set-up that came with the BB&, but I'm going to use your method tomorrow.

    Is there any significant difference between pad brands/models?

    What about rotor/padset exclusivity?

  5. #5
    Senior Member ClarkinHawaii's Avatar
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    Quote Originally Posted by badamsjr View Post
    +1 on the breakin. I followed Avid's instructions to set up my Road BB7--loosen the mounting bolts, then tighten the adjusters (red knobs both sides of caliper) until you have 1/3 spacing on the inside (fixed) and 2/3 space on the outside (moving pad). Tighten the bolts, then back off the adjusters until you have just a little 'scuffing' of pads on rotor. Then ride hard to break in. Now adjust for minimum spacing without drag. Now you should be good to go!

    BTW--the oem pads had a fair amount of squeal, so I got some Kool Stops, and now they do not sound 'like a pig under a gate'!
    So the Koolstops are better noise-wise. How about braking capability?

    Is there any benefit to be gained by keeping rotor/padsets segregated?

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    Single-serving poster electrik's Avatar
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    Quote Originally Posted by badamsjr View Post
    +1 on the breakin. I followed Avid's instructions to set up my Road BB7--loosen the mounting bolts, then tighten the adjusters (red knobs both sides of caliper) until you have 1/3 spacing on the inside (fixed) and 2/3 space on the outside (moving pad). Tighten the bolts, then back off the adjusters until you have just a little 'scuffing' of pads on rotor. Then ride hard to break in. Now adjust for minimum spacing without drag. Now you should be good to go!

    BTW--the oem pads had a fair amount of squeal, so I got some Kool Stops, and now they do not sound 'like a pig under a gate'!
    Gotta be careful who your bicycle squeals like a pig around... "Hey boi, you look just like a hawg."

  7. #7
    17yrold in 64yrold body
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    The Kool Stops feel like they have a little more grip. I have also installed a 203mm rotor and adapter for more power, so it is kind of hard to say which makes it haul down so good!

    Can't really speak to using different rotor/pads--I only have the 203.
    Last edited by badamsjr; 08-10-10 at 10:39 PM.

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    17yrold in 64yrold body
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    Quote Originally Posted by electrik View Post
    Gotta be careful who your bicycle squeals like a pig around... "Hey boi, you look just like a hawg."
    I used to feel like one too, before I dropped 35lbs!

  9. #9
    Senior Member BCRider's Avatar
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    I've used both the OEM Shimano pads as well as EBC pads on one set of brakes with no noticable advantage. Other than that I've used some Hayes brakes and found that the OEM pads, which I have not worn out yet, worked excellently. I've since sold both those bikes and my new all purpose mountain bike has some Avid Elixir brakes which I have yet to try thanks to moving house. So I'm hardly a good authourity to ask about different pads. But I can confirm that the pads I've used worked better after a good long hill heating run to where things were hot enough that even a lightning like tap of the rotor left a greyish charred flash of surface skin on my fingertips.....
    Model airplanes are cool too!.....

  10. #10
    Senior Member ClarkinHawaii's Avatar
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    Thanks, Guys. I've been very conservative with my application of braking force--clearly a mistake--but I seem to remember that with automotive disc brakes you're supposed to be sure not to keep steady pressure applied since that causes the pads to glaze, thus losing stopping power. Maybe i remember wrong . . .

  11. #11
    Senior Member BCRider's Avatar
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    No, you're remembering right. That practice came out decades ago when friction materials technology was young and the materials used for brake pads were not as good as now. And like so many old practices it has been faithfully handed down through the decades to now when our materials are not the same as then and do not respond the same. The pads used now will polish up and look shiney early on but it's all but impossible to actually "glaze" them unless you get some external contamination on them and that stuff bakes onto the pads and messes them up. When I got my first set of Hayes disc brakes I went out to the local steep park and went up and down the hills there twice using the brakes liberally. On the way to the park stopping took a pretty fair squeeze. After the runs down the hill and the systems cooled off it was a one finger wonder to use them.

    Similarly back when I was racing motorcycles to "break in" the new pads it was a case of a combo of seating the new pads to the rotors as well as getting them hot. The first few laps were to seat the pad faces to the rotor shape and then the next few were to heat them up. Come in and let 'em cool off and then they were fine for the rest of the season.
    Model airplanes are cool too!.....

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    Senior Member ClarkinHawaii's Avatar
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    Thanks for explaining.

    I'm going to persist with this other question.

    Hypothetical Situation: When I have the current pad/rotor combination broken in and all is well, I get a flat and need to substitute my other standby wheel with a different rotor. Should I change pads and keep the first set for exclusive use with the rotor it broke in with?

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    another retro grouch Mr IGH's Avatar
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    I like the stock pads, they last a long time and I've heated my rotors until they turned blue and they didn't fade.

    Quote Originally Posted by ClarkinHawaii View Post
    Hypothetical Situation: When I have the current pad/rotor combination broken in and all is well, I get a flat and need to substitute my other standby wheel with a different rotor. Should I change pads and keep the first set for exclusive use with the rotor it broke in with?
    If you can swap out disc pads you should be able to put a new tube in and keep your stock wheel/disc on your bike.

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    Senior Member ClarkinHawaii's Avatar
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    Quote Originally Posted by Mr IGH View Post


    If you can swap out disc pads you should be able to put a new tube in and keep your stock wheel/disc on your bike.
    Oh God, that was just an example--Let me change my hypothetical situation: When I have the current pad/rotor combination broken in and all is well, I need to do some extensive maintenance on the wheel which requires its removal for a week (because I'm missing a part) and need to substitute my other standby wheel with a different rotor. Should I change pads and keep the first set for exclusive use with the rotor it broke in with?

    I know, I should be able to foresee what parts I will need and therefore this situation should never arise, but hypothetically!!

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    Senior Member BCRider's Avatar
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    Bicycle pads and rotors don't wear in to the same extent or patterns as car or motorcycle rotors. You can safely just stuff a different wheel and rotor in there and carry on. Or at least you COULD if these were dual piston hydraulic units. Because you're running a mechanical caliper where the inside fixed pad fit is critical you'll likely need to take a minute and retune the inner pad seating with the wheel swap since it's highly unlikely that the rotor will be in exactly the same spot to that level of accuracy.
    Model airplanes are cool too!.....

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    Senior Member ClarkinHawaii's Avatar
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    I think I'm going to take the Kamehameha Highway from home (elevation 1000') to the North Shore, a drop of 1000' in 10 miles. Ride the brake the whole way. I can put the bike on the bus rack for the return trip.

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    another retro grouch Mr IGH's Avatar
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    Quote Originally Posted by ClarkinHawaii View Post
    Oh God, that was just an example...hypothetically!!
    it's not that convenient to swap pads, I find it easier to keep the same wheel/rotor/caliper on a particular bike. BTW, I have 4 disc brake bikes plus two for my kids, this isn't hypothetical

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    Senior Member ClarkinHawaii's Avatar
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    Quote Originally Posted by Mr IGH View Post
    it's not that convenient to swap pads, I find it easier to keep the same wheel/rotor/caliper on a particular bike. BTW, I have 4 disc brake bikes plus two for my kids, this isn't hypothetical
    You're absolutely right--it would be easier, more convenient, more sensible, more logical, to use the same pads/rotor.

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    another retro grouch Mr IGH's Avatar
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    Quote Originally Posted by ClarkinHawaii View Post
    You're absolutely right--it would be easier, more convenient, more sensible, more logical, to use the same pads/rotor.
    Now you're getting it. The BB7 rotor isn't an FI carbon fiber disc brake system, it's pretty robust. I swap wheels/rotors and don't change the pads...Did I mention it's a PITA to change pads, hypothetically

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    Senior Member ClarkinHawaii's Avatar
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    Quote Originally Posted by Mr IGH View Post
    Now you're getting it. The BB7 rotor isn't an FI carbon fiber disc brake system, it's pretty robust. I swap wheels/rotors and don't change the pads...Did I mention it's a PITA to change pads, hypothetically
    Well now, from what I read, changing the pads is just slide 'em out and slide new ones in--no tools required. adjust clearances. If it turns out to be a PITA, that's a whole different ball game.

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    17yrold in 64yrold body
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    Is that like the saying "if you think sex is a PITA, you're doing it wrong"?

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    Senior Member ClarkinHawaii's Avatar
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    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by ClarkinHawaii View Post
    Oh God, that was just an example--Let me change my hypothetical situation: When I have the current pad/rotor combination broken in and all is well, I need to do some extensive maintenance on the wheel which requires its removal for a week (because I'm missing a part) and need to substitute my other standby wheel with a different rotor. Should I change pads and keep the first set for exclusive use with the rotor it broke in with?

    I know, I should be able to foresee what parts I will need and therefore this situation should never arise, but hypothetically!!
    I used to follow this hypothetical idea in actual practice. The main issue is the human variable. It was impossible to remove a set of pads+rotors and re-install them back with exactly the same alignment. There always ended up being a break-in period immediately after swapping back in the other pads+rotors. Even though they supposedly were a matched set.

    After a while, it was more hassle than it was worth to swap the pads. I just left the same pads on there and swapped just the wheels.

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    Senior Member ClarkinHawaii's Avatar
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    Thank you. I've learned a lot from this thread. This is my first experience with disc brakes . . . of course.

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