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  1. #1
    Tandem Mountain Climber
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    Another disc brake on a Calfee thread.

    So I installed the Avid BB7 with EBC gold pads and Hope floating rotor (oh.. and the Power Brake Booster).

    Here's the basics:

    - I had to grind a little bit of material off of the caliper with my trusty die grinder to clear the rivets of the rotor (connecting the middle section to the outer section of the rotor. It wasn't a big deal, just a bit where the caliper pokes out near the rear caliper mounting bolt.

    - Wow the tolerances are tight on pretty much everything, but nothing rubs.

    - Man this stuff adds a lot of weight!!

    Notes/Thoughts:

    It took me a while to get it setup, but finally ended up with a decent lever feel, firm, etc.. However, it just doesn't stop well yet. Not very grabby, at all, and need a good deal of hand effort to get good power.

    Now I know they need to break in, and I hope they do so soon.

    I finished the bike on Friday, last week, and we were able to only get a quick 7 mile ride up and down some neighborhood hills, to test everything out, and help bed the brakes.

    Then on Saturday we did the Mt. Tam Double Century, which amounted for 200 miles and 16,700 feet of climbing. Most of which was steep up and down rollers... ugh.. not good terrain for testing I think I must have shifted over 2000 times, seriously!

    The bike did pretty well, I have to fix a couple things that bugged me, but the ride of the frame was nice!

    Thing that's bugging me, is the disc brake, it still doesn't have very much stopping power. Should it take more than 200 miles to break that thing in???

  2. #2
    hors category TandemGeek's Avatar
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    Quote Originally Posted by uspspro View Post
    Thing that's bugging me, is the disc brake, it still doesn't have very much stopping power. Should it take more than 200 miles to break that thing in???
    Unfortunately, I have no first hand experience with your Hope rotor and EBC brake pad set-up

    I can only speak to the break-in period for Avid's 203mm G2 Clean-Sweep rotor and their OEM pads which, at least based on breaking-in two different tandems with the same set-up, seemed to have two distinct break-in periods:

    1. Initial stopping power out of the box was non-existent but by over-using the rear brake during a short 30 mile / 2,300' ride from home the OEM pads bedded-in and seasoned the rotor to the point where I could drag the tandem to a near stop from 25 mph to about 4 mph on an 8% grade under full-braking at which point the rear tire finally locked-up the rear wheel and skidded the rear tire. From my journal....

    As for performance, on our first day back on the Calfee with the Avid rear disc I intentionally over-used the rear brake to accelerate the bedding-in process over our 30 mile / 2,300' regular loop ride from the house. By the time we were headed down the 8% grade into our community I was able to get the rear wheel to lock using only the rear brake. The following weekend we did an in-town ride with three other couples. For those who don't know, the city of Atlanta and its surrounding communities north of I20 are actually quite hilly in many areas. Anyway, as I did yesterday, I intentionally overused the rear disc brake and by about 1/2 way through the ride the stopping power was well on its way towards what I would call "normal" for an Avid BB7 with 203mm rotor. It had been over a year since we'd ridden our Avid BB7 equipped '02 Erickson and it was nice to have a really grippy rear brake back on the tandem. While we really don't need it for most of the rides we do locally, it's wonderful to have when we head up to the regional mountains.

    2. Once the brake pads have completed that initial bed-in process and the rotor is seasoned, our rear disc brakes have exhibited a further and somewhat progressive increase in braking power over a few hundred miles until somewhere around 300 miles or so there was a pronounced increase in brake bite. However, it's noteworthy that during this break-in period the Avid's caliper required a routine post-ride brake pad adjustment to compensate for the very quick, initial wear that occurs as the OEM pads wear down the higher contact surfaces (upper edge of inner pad, lower-edge of outer pad) and end up with an off-camber wear pattern that is essentially faced to match the rotor's position under full brake power: remember, the rotor is pushed ever so slightly inward against the inner, fixed brake pad by the actuating arm, hence the off-camber wear.


    So, getting back to the Hope & EBC pads, it could be that you've created a longer break-in period by going to the longer-wearing / sintered EBC Gold compound and perhaps the Hope rotor's lower-heating characteristics or differences in the stainless steel used for the rotors are further exacerbating the length of time it will take for the pads and rotor to bed-in. Again, it's been somewhat interesting to me that my break-in periods were not really that linear. There was some initial improvement that occured at a somewhat steady rate of progress as the brakes were used followed by an incremental 'jump' that took me by surprise when the brakes really started to bite. Again, I've also not had to use any type of an in-line brake booster (PBP or Travel Agent) on either of our Avid-equipped tandems so once again I can't comment on how they may or may not alter the break-in process and timelines.
    Last edited by TandemGeek; 08-03-09 at 03:29 PM.

  3. #3
    Tandem Mountain Climber
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    One more note I should add:

    Despite the Hope rotor being spec'd at 203mm, I needed to run one thin washer on each caliper mounting bolt to space the cailper outward just a tad.
    Last edited by uspspro; 08-03-09 at 04:46 PM.

  4. #4
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    I recently tried Swiss Stop pads with the Avid rotors, not happy with it at all, lever feels mushy, braking feels nonexistant. Pads have had a reasonable time to season, 300 + miles at on hills in the Santa Cruz mtns. I will switch back to the Avid organics. I have been working on parts for the Hope floating/vented disc,I should have some results soon.

  5. #5
    Tandem Mountain Climber
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    another question...

    How true are your rotors?

    This one seems slightly out of true...

  6. #6
    hors category TandemGeek's Avatar
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    Quote Originally Posted by uspspro View Post
    How true are your rotors?
    Very true, +/- .5mm

    And, I'll make a confession to another stupid human trick that I've used: I throw new rotors in the oven and anneal them at 500* for about 10 minutes and let them cool before mounting. I'm not sure how much it reduces the hardness (I'm guessing not much), but it seems to make the rotors mount-up and run true and it also gives them an interesting bronze-gold tint.

    I'm not recommending this to anyone because, as I said, I'm not smart enough to know if there is any downside to the process or if what I think happens really does. Given how hot rotors get in use, I simply assumed it was a safe bet that there was no down side.

    Now, as to why I even thought to stick a rotor in the oven... The rotor on our '02 Erickson was a wobbly mess and I got fed up trying to true the thing. So, after pulling it off and staring at it sitting there on the work bench I had a flash of brilliance: I wondered if the stainless steel alloys used in rotors didn't have a little bit of 'memory' such that any cold-set bends created during shipping, storage or handling might not go-away once heat was applied to the rotor. So, into the oven it went.

    Anyway, so far so good. I haven't cracked any rotors or observed any other ill-effects and it did seem to make the rotor spot-on for trueness after the oven treatment.

  7. #7
    Senior Member
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    Sounds like this was the maiden voyage of the new bike. Congratulations.

    Might you do a write-up comparing old bike to new bike?

  8. #8
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    Quote Originally Posted by uspspro View Post
    another question...

    How true are your rotors?

    This one seems slightly out of true...
    Are you saying the new hope rotor is out of true or are you refering to the original Avid rotor? My vented Hope is still stting at the shop, I have not checked it for trueness.

    Also when attaching a rotor it should be tightened in a star pattern similar to what you do when mounting a car wheel.

    Dropped off the modified Avid S/S clips at the machine shop today. Hopefully my vented disc will soon see some use other than a coffee coater.

  9. #9
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    Has anybody actually blown a tube using rim brakes?
    In 20 years of tandeming I never have.
    When I read about all the issues with disk brakes plus the extra weight and cost I don't think I want to go there. I could see how they would be nice to have in the rain but I don't ride in the rain normally.

  10. #10
    Senior Member rdtompki's Avatar
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    Didn't I see a thread discussing improved performance of even the non-vented Hope rotor over the standard Avid rotor? My wife and I are satisfied with braking performance so far (rear avid disk) and we're not racers, but you can never have too much braking for a given weight penalty.
    Rick T
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  11. #11
    hors category TandemGeek's Avatar
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    Quote Originally Posted by jnbrown View Post
    Has anybody actually blown a tube using rim brakes?
    In Question #8 of a survey I conducted last winter, 17 of 291 respondents (6%) indicated they had suffered a tire blow-off due to rim heating. Another 19 (7%) indicated they had experienced total brake fade / loss of stopping power.

    Looked at another way, and given that 212 of the survey respondents did not report any serious tandem component failures, 45% of the 79 folks who reported serious problems cited brake-related issues.

    You can find the survey results here: http://www.thetandemlink.com/surveys/fallsurvey_08a.htm

    My Survey Archives can be found here: http://www.thetandemlink.com/surveys/surveycentral.html

  12. #12
    Tandem Mountain Climber
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    Quote Originally Posted by chichi View Post
    Are you saying the new hope rotor is out of true or are you refering to the original Avid rotor?
    The Hope.

    I never bought the Avid rotor.

  13. #13
    Tandem Mountain Climber
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    Quote Originally Posted by jnbrown View Post
    Has anybody actually blown a tube using rim brakes?
    In 20 years of tandeming I never have.
    When I read about all the issues with disk brakes plus the extra weight and cost I don't think I want to go there. I could see how they would be nice to have in the rain but I don't ride in the rain normally.
    Depends where/how you ride in determining whether or not the disc is worth it.


    I am willing to do a little test & tune to figure it out and see what kind of results I get.

    If in the end, I don't see a worthwhile increase in performance/confidence. I have a rear caliper ready to go on. But, from what I know and have read, the disc has potential to be quite nice for the terrain/type of riding we do. So, because of that I am willing to put up with some initial growing pains.

  14. #14
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    Quote Originally Posted by TandemGeek View Post
    In Question #8 of a survey I conducted last winter, 17 of 291 respondents (6%) indicated they had suffered a tire blow-off due to rim heating. [/url]
    What is meant by a tire blow off? Is it the inner tube blowing due to heat and then the tire coming off rim due to on air in the tube? Or is it the heat directly affecting the tire?

  15. #15
    hors category TandemGeek's Avatar
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    Quote Originally Posted by jnbrown View Post
    What is meant by a tire blow off? Is it the inner tube blowing due to heat and then the tire coming off rim due to on air in the tube? Or is it the heat directly affecting the tire?
    I don't believe a conclusive test or analysis of incidents has been conducted to come up with a definitive answer to that mystery.

    My personal unproven theory is that wire-beaded tires seem to be involved in most all of these incidents and acts as a heat sink that when conditions are just right (e.g., very high brake heat, thin-wall or well-worn or aged inner tube mated with an older tire) the inner tube will be weaked along the bead and eventually fails in a dramatic way and with enough force that it unseats the bead and/or blows-out the tire sidewall.

    It also occurs to me that it's the cautious descenders who will usually experience the blow-offs, not the folks who bomb the descents and reap the benefits of rim cooling vis-a-via air flowing over the rims at a fairly high velocity in between moderate check-speed braking and short, but very aggressive braking at the entrance to corners. Conversely, the cautious riders will apply constant braking throughout the descent at low to moderate speeds that don't help to bleed-off heat from the rims, thereby allowing rim heat (and, in turn, wire bead heat) to build up to higher temperatures for longer periods of time.

    In fact, one of the more interesting things I've seen on at least two occasions that I can remember are teams who made controlled descents without suffering a blow-off during the descent but who immediately came to very aggressive dead stop at the bottom of the hill and within moments thereafter "BOOM"; the rear tire blew. Again, I theorize that it's the cummulative heating and lack of air flow that will allow a wire rim bead to weaken an inner tube to the point where it bursts and, clearly, if you come to a dead stop after using maximum braking at the bottom of a long descent, your rims and the wire beads will be about as hot as they'll get at any point in time.

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    Thanks for the detailed explanation. Of course its something we all want to avoid.
    I do try to avoid braking when possible on long hills.
    I have been using wire bead tires (Gatorskins) for many years because I had an experience with a folding tire that blew off the rim due to pressure several times. I believe it was due to the tire / rim combination. I didn't realize the wire bead could be involved in transfering heat to the tube. Right now I am trying a Rubino Pro folding tire on the back and have only ridden it once so far.

  17. #17
    Senior Member Homeyba's Avatar
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    Quote Originally Posted by jnbrown View Post
    Has anybody actually blown a tube using rim brakes?
    I've never had one blow off on my tandem but I did on my single bike back a few years back. I think it really depends on the type of riding you are doing. I was on a long, steep (6-15%) curvy descent. It was fast too, 50+mph. Luckily I felt the tire go out of round (ie thump,thump, thump), got the bike stopped and got off just in time to watch it go BOOM! The tub actually pushed the nearly new tire (Conti GP3000?) right off the rim before it exploded.

    I agree with jnbrown that variation in wheel diameter/tire diameter can be a significant contributor to the problem. Some tires go on some wheels very easy and not on others. On that bike it was always very easy to put the tires on by hand. I personally feel that contributed to my case.

    Since I've had that happen on my single bike, I take no chances on the tandem. I do a lot of fast technical descents and that is something I don't want to have to worry about.
    Last edited by Homeyba; 08-04-09 at 04:58 PM.
    It doesn't get harder, you just go slower.

  18. #18
    Tandem Mountain Climber
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    I popped a tire on a Downtube Mini, 16" wheeled, folding bike going down Alpe d'Huez

    Damn little wheels!!

    Of course it was coming down the mountain after the TdF stage, so there was LOTS of braking.. that plus small wheels = BOOM!

    See tube! ()




  19. #19
    PMK
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    Is the rotor hub showing runout side to side, or the disc. Being a floating design, it may not be exact but should remain more true under heat of braking.

    PK
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  20. #20
    hors category TandemGeek's Avatar
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    Quote Originally Posted by jnbrown View Post
    I didn't realize the wire bead could be involved in transfering heat to the tube.
    Like I said, it's a theory of mine driven mostly by the disproportionate number of wire-bead vs. folding kevlar beaded blow-offs on tandems... and the higher heat loads.

    I do agree with the other problems associated with mis-matched tire & rim combos. I recall that back in the late 90's there was a raft of problems with Specialized tires, the Armadillos at first and then the Turbo/A's and there have been a few other rim and tire combos that just didn't work well.

  21. #21
    Senior Member VaultGuru's Avatar
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    +1 on TG and Chichi's comments. I am also using the Hope rotor with the standard Avid pads and notice a significant difference in both stopping power and the rotor remaining true, even after really heating it up. I also run very tight tolerances. We descended some long, steep grades in CO this summer that required me to be on the brakes a lot due to slow traffic. When I finally stopped, the Hope rotor was so hot that it was "ticking" from the sound of the rotor and spider cooling down. No rotor warp. You might want to go back to the standard Avid pads and give them a try.
    To improve the brake response, I replaced the typical 5mm spiral wind brake cable housing with BMX linear wire brake housing. The spiral wind produces a lot of cable housing distortion when squeezing hard on the brake lever. The linear wire brake cable housing literally stops the distortion. I am able to contact the rotor with very little level movement and feel the bike slowing with very little additional pressure.

  22. #22
    Tandem Mountain Climber
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    Quote Originally Posted by VaultGuru View Post
    To improve the brake response, I replaced the typical 5mm spiral wind brake cable housing with BMX linear wire brake housing. The spiral wind produces a lot of cable housing distortion when squeezing hard on the brake lever. The linear wire brake cable housing literally stops the distortion. I am able to contact the rotor with very little level movement and feel the bike slowing with very little additional pressure.
    Even the run of housing to the handlebar? Does it flex enough?

  23. #23
    Senior Member VaultGuru's Avatar
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    Change the handlebar housing also. The rear housing on the handlebar is as long, or longer, than the rear housing. I even changed my front brake cable housing. You won't notice as much difference since the length is so short. Forgot to comment on your BPB. There is an upper and lower hole to insert your brake cable housing. Since you are using (I presume) road levers, make sure you insert the cable housing into the lower hole. You will have greater travel distance of the cable when you squeeze the brake lever. Thus, you are able to apply more pad pressure to the rotor.
    Forgot an additional comment on our descent in CO. Yes, the rotor got hot enough that I could hear the ticking sound while the rotor cooled off, but I also got no fade on the brake. Maybe another reason to go back to the original Avid pads.

  24. #24
    Tandem Mountain Climber
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    Quote Originally Posted by VaultGuru View Post
    Change the handlebar housing also. The rear housing on the handlebar is as long, or longer, than the rear housing. I even changed my front brake cable housing. You won't notice as much difference since the length is so short. Forgot to comment on your BPB. There is an upper and lower hole to insert your brake cable housing. Since you are using (I presume) road levers, make sure you insert the cable housing into the lower hole. You will have greater travel distance of the cable when you squeeze the brake lever. Thus, you are able to apply more pad pressure to the rotor.
    Forgot an additional comment on our descent in CO. Yes, the rotor got hot enough that I could hear the ticking sound while the rotor cooled off, but I also got no fade on the brake. Maybe another reason to go back to the original Avid pads.
    - Yep, I am using the lower hole on the BPB.
    - I heard the pinging after a long descent (while stopped at a rest stop) last weekend. Pretty cool actually (function of the floating rotor)
    - Compressionless housing seems like a good idea. I can see the spiral housing flex A LOT, when I squeeze the lever.
    - I will give the EBC pads a couple more rides, then swap in the Avid pads, if they aren't working out.

    Thanks,
    Marco

  25. #25
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    This does sound like a compatability problem. 203 mm discs will stop you quick enough with the extra leverage with the large disc. But somehow stopping power is not there. Don't know the pads you are using but try another make/grade to see if it makes a difference. But to me it sounds like the Brake lever is incompatable with the caliper. Somehow you are not getting enough leverage on the brake pads. perhaps the leverage is is wrong or the brake booster not working right.

    And on preheating the discs. It has been noted on a few Dusk rides- that after heavy braking my Discs are giving out a dull orange glow. Didn't believe it till I put a gloved hand on it and the gloves started smoking.
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