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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 07-23-11, 07:27 PM   #1
recumpence
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11 inch brake rotor

Hey Guys,

I am developing a 11 inch rotor and caliper mount. This was originally intended for electric bike use. However, I began to realize that this may be a good item for tandem cyclists.

I have not run this prototype rotor yet. However, it looks like it will cost about $95 for the rotor and caliper mount kit.

Any thoughts?

Matt
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Old 07-23-11, 07:30 PM   #2
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Here is a picture of my 283mm (11 inch) rotor next to a standard 160mm rotor.

Matt
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Old 07-23-11, 07:30 PM   #3
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overheating an 8 inch rotor or what?
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Old 07-23-11, 08:05 PM   #4
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We have 8" discs on our road and off-road tandems.

The most abuse our road brakes have seen was a lap around Lake Tahoe. I suppose we could have used a bit more brakes, but I'd almost wonder if the loads would start to become to great for the structure securing the caliper.

For local road stuff, I'm probably going to reduce the rear to 185mm.

Off-road it would be nice to have a larger front disc than 8". 11" might be good , but may get caught in ruts. Any planned sizes between, like maybe a 9 or 10"?

PK
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Old 07-24-11, 09:23 AM   #5
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..We are using the BB7's with 203mm rotors for the first time after 20+ years of using the whole spectrum of brake on our Tandems. While the BB7's have a few irritating characteristic, the one thing they do very, very well is stop a tandem... right now!
If anything they border on too aggressive for most riding. Given that, I would not be a candidate for a larger rotor or anything with greater stopping power. Additionally, I'm not a fan of heavy wheel packages and I suspect the larger rotors would require something greater than what I have now which are already a bit much.
However... a noise free, drag free, easy to set-up replacement caliper for my BB7's would be of big interest.

Bill J.

Last edited by specbill; 07-24-11 at 09:24 AM. Reason: spelling error
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Old 07-24-11, 01:47 PM   #6
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The BB7's with the 203mm rotors are sometimes difficult to set up and not rub because the rotor is not true. Would the 11 inch rotor be even more difficult to be true and to set up without rubbing?
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Old 07-25-11, 06:38 AM   #7
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Thank for the input, Guys.

As I mentioned, I made this rotor for E-bike use and I figured I would see what the tandem community thought of it. I have a couple E-bikes that blue the rotors. That will not happen to this rotor.

The basis for my question to you here is that I remember a while back seeing a tandem with a custom large front rotor. That bike was used for mountain riding. So, when I made this rotor, I thought I would show it to the tandem guys and see if they have any thoughts.

Thanks for the input.

Matt
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Old 07-25-11, 04:35 PM   #8
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perhaps a aluminum spider with a steel, ring , the spider stiffens the disc ring.
and adds a Heat sink.. heat sinks are good, when heat is generated ..

Lots of rear tandem hubs made with a threaded mount .
The Drum Brake Arai was THE drag brake , so lots of hubs were made to fit those

Its a RH thread like a freewheel.. but of course since on the left , braking force tightens it on..

there are screw-on to 6 bolt adapters because of that..
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Old 07-25-11, 04:35 PM   #9
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double disc front wheels next?
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Old 07-25-11, 06:44 PM   #10
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perhaps an aluminum spider with a steel ring , the spider stiffens the disc ring, and adds a Heat sink.. heat sinks are good, when heat is generated ..



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Old 07-26-11, 09:31 AM   #11
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Yours?

If yours, make and how does it compare to Avids. Another disc I've been looking at are Magura Venti disc.
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Old 07-26-11, 06:47 PM   #12
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Yours? If yours, make and how does it compare to Avids?
Yeah. I started out with the Avid 203 mm, but needed more heat capacity because I am in Northern California, where steep and twisty descents abound, and because my stoker is preternaturally terrified of descending. I have to use my brakes to slow us way down, or find a new stoker. This stoker terror is a real demand on the brakes. For example, on the Death Ride our average 28 mph descent of West Monitor rendered my stoker visibly shaken. According to Strava, of 364 cyclists having descended West Monitor, the median speed is 35 mph, and our 28 mph was 344th (95th percentile). And it still was *too fast*. So, I need brakes.

On this thread, PMK tipped me as to the Formula 220mm (8.7") rotor, which was discontinued in 2009, but still available.





I thought it might fit within the chainstay, but it would not. This is with the 220 mm rotor. Too tight.




Accordingly, I took the bike to Calfee when we did a ride in Santa Cruz. They did a chainstay modification (and took these photo's as well).



This got the 220 mm to fit.



They did a carbon repair.



So, now the 220mm rotor fits fine, and the chainstay doesn't look any different.



The Avid 203 mm and the Formula 220 mm weigh 190 and 217 grams respectively, an increase in 27 grams (14%). The diameter and circumference are 8.7% larger, and the surface area 17% larger. The aluminum spider may help in heat conductance and dispersion (and the different color and pattern break up what can look like a manhole cover with a large disc).

I'll report how it has worked out in a later post.
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Old 07-26-11, 11:45 PM   #13
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Quote:
Originally Posted by Ritterview View Post

I'll report how it has worked out in a later post.
Ritter,

Have you tried the Avids without the brake booster piece? For me, the difference was night and day (for the better) without it.

The booster made the brake engage sooner, but with less power... at least in my experience.
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Old 07-27-11, 12:32 AM   #14
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Ritter,

Have you tried the Avids without the brake booster piece? For me, the difference was night and day (for the better) without it.
Like I am going to take braking advice from uspspro, whose idea of a panic stop is for Ruth to adopt a slightly non-aero position. I've seen your descending videos, where the telephone poles look like a picket fence, but I think I'd have to go frame-by-frame to find where you use your brakes. 30 minute video, and if you freeze it at 16:45:32...there! ...a feather. You've probably forgotten that you have brakes.
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Old 07-27-11, 02:16 PM   #15
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I thought it might fit within the chainstay, but it would not. This is with the 220 mm rotor. Too tight.
I believe that would be the case with the majority of tandems out there - not enough chainstay room for anything much bigger than the 203mm Avid.

I've got front and rear discs on the CoMo - the bike stops incredibly well - especially with the addition of the front disc.
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Old 07-27-11, 07:15 PM   #16
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Formula 220mm has been great for past 3 years

We've been using the Formula 220mm rotor, BB7 (road) and EBC gold pads on our '97 Santana ... and there's plenty of chain stay clearance for a larger rotor.

It's been used (and abused) on extended descents down Independence, Monarch, Cottonwood, Rabbit Ears, Freemont, Vail, and Tennessee passes in Colorado, as well as Mt Evans. Some front range descents are considerably steeper, but shorter, and we haven't experienced fade.

FYI, we are a 280# team and EBC pads last about a year.

Cheers.
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Old 07-27-11, 10:08 PM   #17
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...how does it compare to Avids.
I've been very happy with the Formula 220 mm. It stops with better or equal power, and it has noticeably less fade. We've gotten it hot, but there has been no warping. It can be noisy, but not any more so than was the Avid. I have more confidence on descents that my rotor will be up to the task.

We put it to a real test in descending steep, twisty, and narrow King's Mountain Road. I needed to keep it slow enough to keep my stoker from wigging out (though other tandems have averaged 29.3 mph). The rotor did get hot.


[video=youtube;jahkXyv0izU]http://www.youtube.com/watch?v=jahkXyv0izU[/video]

Last edited by Ritterview; 07-27-11 at 10:13 PM.
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Old 07-27-11, 11:31 PM   #18
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Yes - that disc and the caliper assembly definitely gets HOT. On our Santana, we "deformed" the BB7 inboard plastic adjustment knob after braking from 50+mph to zero due to stopped traffic on a 15% grade in 90F heat ... brake functionality not impaired and as others have noted, the knob is replaceable.

Not trying to start a carbon vs metal frame war, but just wondering if there's any reason for concern about the heat from a hot disc caliper assembly damaging resin in the joint between the carbon frame and the metal dropout?

Asking because some early carbon frames were reported to have delamination issues if left inside a car on a sunny day ... any idea what the heat range is for modern resins?
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Old 07-27-11, 11:51 PM   #19
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just wondering if there's any reason for concern about the heat from a hot disc caliper assembly damaging resin in the joint between the carbon frame and the metal dropout?

...what is the heat range is for modern resins?
Hmmm...that is a good question. The first thing to do will be to measure the temperature of the titanium dropout. I'll have to bring along my IR thermometer, and find out.

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Old 07-28-11, 05:24 AM   #20
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If the frames are made from prepreg with the required heated cures, will handle more heat abuse. Frames that are layed up wet and cured either at room temp or or slightly elevated temps will see more heat concerns.

The concern will never be heat affecting the carbon fibres, but rather heat affecting the resins system.

Additionally, many, but not all times, owners see the paint or clear coat separating from the composites and beleieve the frames structure is failing. Not saying that frames can't delaminate, but most often it is the cosmetic layer.

Beyond the heat concern is the torque applied into the brake mount / frame or fork from good brakes in general.

I do like those red rotors though and don't even own them...yes I'm jealous of the bling.

PK
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Old 07-28-11, 07:56 AM   #21
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Thanks Ritter.

I just upgraded one of our CoMo's with front disc (already had rear) and am less than impressed with braking performance. For example, can't come close to locking up rear . Currently using Avid G3 discs with standard Avid sintered pads. Front disc is a wee bit out of round too.

Haye's has a new al spider disc and there is Magura's Venti disc as well.

By the way, with Wound Up Duo Tandem disc I too had to modify (shave) the caliper adaptor mount so that the caliper would move further out from centre.
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Old 07-28-11, 11:38 AM   #22
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Quote:
Originally Posted by sine View Post
Thanks Ritter.


Haye's has a new al spider disc and there is Magura's Venti disc as well.
Had good luck with this magura rotor http://www.cambriabike.com/shopexd.asp?Item=100027198
and this Hope rotor http://www.jensonusa.com/store/produ...oth+Rotor.aspx

But they have both been on mtb tandems... I am looking to try the 2 piece rotor with the Avid BB7 on our Calfee, we'll see how it goes.
The two piece rotors have a much greater tolerance to warping.

My .02 cents
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Old 07-28-11, 01:06 PM   #23
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The Magura you linked was 180mm, but it available in 203 mm? Magura has some interesting rotors.

The Hope is also 203 mm.

I figured that increased diameter was what I needed, as our limitation was disc heat capacity and dispersion, which requires rotor surface area, and surface area increases with the square of the radius (A = πr2).

Quote:
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I am looking to try the 2 piece rotor with the Avid BB7 on our Calfee, we'll see how it goes. The two piece rotors have a much greater tolerance to warping.
I like the idea of a two piece rotor, as the aluminum spider is lighter, has better heat conduction, and can be anodized in fetching colors. I have seen it asserted that warping is reduced, and we have certainly put the Formula to the test in that regard, but I haven't seen the proof that a two-piece is less warpage prone.
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Old 07-28-11, 01:25 PM   #24
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I am running the Hope vented 2 piece rotor, it took some work to open up the BB7 caliper wide enough to accommodate the disc but the results are worth it. I ride the same hills and am probably of similar weight to ritterview and I have not had problems with warping since going to the Hope rotor. I use the Avid organic pads as the metal pads can be noisy, we are riding about 5000 miles a year and change the pads 3 or 4 times a year.

It is my understanding that the benefit of the two piece rotor is that it gives the hot braking surface the ability to expend independently of the center which is cooler.

Judging by the responses that braking threads tend to get it appears that tandem riders are not happy with the current choices. Seems like there may be an opportunity here but I do not believe increased diameters is the solution. I am hoping that with disc brakes coming to cyclocross we see some interesting solutions integrating hydraulics and road style brake levers.
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Old 07-28-11, 02:08 PM   #25
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I am running the Hope vented 2 piece rotor...
To clarify, the 2 piece rotors linked above are not dual rotors such as the Hope vented. The two pieces refer to the outer steel braking surface with an inner alloy spider.

This two-piece Hope 203 mm is lighter than the Avid. If it resists warping better, what's not to like, as it is pretty as well.

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