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Old 04-09-11, 12:27 PM   #1
Guitarrick
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Are larger rotors possible?

I'm a new guy to disc brakes, and I've searched around but can't come up with an answer. I have a Sojourn that came stock with Avid BB5 brakes, 160mm front and 140mm rear. I'd like to upgrade them both to the BB7s, and would really like to get larger rotors while I'm at it.

Here's the hard to explain part. Is it possible to go from 160mm/140mm to a larger sized rotor on both the front and rear, or am I stuck with the same size rotors that the caliper mounts are already located for? Basically, I just don't know whether mounts are located in different places depending on caliper/rotor size or if calipers are designed differently to be mounted in a universal/standard location.

One more question, an easy one. Are the BB7s no-modding bolt-on replacements for BB5s? I'd love to have the 203mm on both the front and rear, if that's not possible I'm still upgrading to the BB7s in my stock size.

Thanks in advance.
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Old 04-09-11, 12:34 PM   #2
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I'm no expert on disc brakes, but the ones I've seen don't have much (if any) latitude on rotor size. The design of the caliper and position of the mounts determines where the shoes are, and the wiped area of the rotor has to pass through there for the brake to work.
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Old 04-09-11, 12:48 PM   #3
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If the frame/fork has IS caliper mounts (bolts to the frame/fork horizontally from side with two bolts 51mm apart) then you can run pretty much whatever size you want with Avid brakes.

You simply swap the small black bracket out that is between the caliper and the frame or fork. If you were buying new brakes you just buy the new ones with the larger rotors and they will come with the new adapter brackets.

The Avid BB7 calipers are universal, the only thing different is the adapter and rotor they come packaged with.
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Old 04-09-11, 12:55 PM   #4
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You simply swap the small black bracket out that is between the caliper and the frame or fork.
+1. I did this with my mountain bike that's equipped with Avid BB7's. I started out with 160mm rotors front and rear, and later switched the front brake to a 185mm rotor. All I had to do was change the black mounting "adapter" to put the larger rotor on.
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Old 04-09-11, 12:59 PM   #5
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Yes, all you need is the appropriate adaptor to take you to 203mm,

BUT - Do you need it? for a road tourer, would suggest not.

The fork will have been designed for a 160mm rotor, and putting anything bigger could lead to frame / fork failure, and with the rear, you may also have issues with any more than 160mm, and also with the rack / mudguard mounting.

Larger discs are only really needed for Mountian Biking, and not on the road. 203mm are normally only use on the front, and then for full on DH, North Shore or AM bikes , on an XC bike, 180/160 or 160/160 are normally used.

Would stick with the rotors you have, as if the cailpers are correctly set up, you should not need anymore braking power to stop a road tourer.

For the BB7's upgrading from BB5's, there should be no issues with a straight swap of these.
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Old 04-09-11, 01:04 PM   #6
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The Avid BB7 calipers are universal, the only thing different is the adapter and rotor they come packaged with.
No they are not, they come in Road and Mountain versions, which have different cable pull length.

You have a Sojourn http://www.raleighusa.com/bikes/steel-road/sojourn-11/

You will need the Road version, this will work with STI's (Brifters) and Road or Canti brake levers

The Mountain version will only work with V-Brake type levers
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Old 04-09-11, 02:28 PM   #7
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...simply swap the small black bracket out...
Ah-ha!! How did I miss this in the design?! Piece of cake.

Being new to discs I'm used to V-brakes that you can pretty much lock up in a split second if needed. I don't ride at 25mph on the MUP or anything, but as much as I can possibly pay attention out there, sometimes it's still needed. Compared to V-brakes, are discs just "wimpy"? Sure they stop the bike, but not RIGHT NOW like I'm used to. The BB7s have an adjustment on both sides of the rotor, not just the inner side like the BB5s, and I've heard they're a much better brake because of this.

So is it the inferior design of the BB5s, small rotors, or the general nature of disc brakes that has me not stopping on a dime?
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Old 04-09-11, 02:42 PM   #8
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Setting up disc brakes is a fussy process but once set they work well for a long time. The key is to get the caliper set up so that the pads are totally parallel to the rotor in both axis to a very low tolerance. Then to set up the fixed inside pad so that it's riding as close to the rotor as you can get without actually skimming. Some flexing/bending of the rotor to true it up may be needed. But keep at it until you get an even scuffing sound all the way around and then back up one click. It's also important to keep on top of that fixed pad adjustment. As the pad wears the gap will open. And when the gap opens much of your lever effort goes into flexing the rotor arms to allow the pads to push the rotor braking track to the side and only then do you get full pressure contact. Keeping that fixed pad close to the rotor means less lever effort is needed to flex the rotor and more goes into stopping.

Until this bit of fiddly setup is done your disc brakes won't show their better side. But once it's done they will feel a LOT nicer than any rim brakes. Typically lever effort will be about the same but the big improvement comes in the ability to modulate consistently across the pressure range and rotational speed like rim brakes all seem to do to some extent.

So take some time to learn the ins and outs of working with the slotted adjustment holes in the mounts and to properly center the brakes using the cup and ball washer sets that Avid uses to allow full adjustments. It's not any harder than setting up V brakes, it's just different. So at first it may seem confusing until you figure out the tricks. But that was the same for V brakes when we got them initially.
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Old 04-09-11, 02:44 PM   #9
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I'm guessing you havn't bedded the pads in, if you don't do this, the braking power will feel poor.

taken from the user manual - http://www.sram.com/_media/techdocs/95-5015-008-000.pdf

pad break in



It may take anywhere from 20 to 40 complete stops to break in Avid pads. You may begin to notice

an increase in braking power after the first ride. Brake noise can occur not only during the break-in

period but off and on throughout the life of the brake pads. Noise is dependent upon factors such

as brake setup, rider weight, riding style, braking style, and riding conditions (i.e. dust, soil, and

contamination of friction surfaces).



When correctly set up, and this includes bedding in the pads, the braking performance will be equal to your V's, and far superior in the wet.

The BB7's are regarded as better than the BB5, due to both pads being adjustable, as you have already noted; but the rotor size will not have an effect on performance with the way you are using it.

One thing which could affect the brake feel, is that you were previouly using v-brakes, and dependant on how you had the levers attached to your handlebar, you may have been able to apply more pressure on the brake lever than you can now on the Sojourn.
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Old 04-09-11, 03:05 PM   #10
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Ah-ha!! How did I miss this in the design?! Piece of cake.

Being new to discs I'm used to V-brakes that you can pretty much lock up in a split second if needed. I don't ride at 25mph on the MUP or anything, but as much as I can possibly pay attention out there, sometimes it's still needed. Compared to V-brakes, are discs just "wimpy"? Sure they stop the bike, but not RIGHT NOW like I'm used to. The BB7s have an adjustment on both sides of the rotor, not just the inner side like the BB5s, and I've heard they're a much better brake because of this.

So is it the inferior design of the BB5s, small rotors, or the general nature of disc brakes that has me not stopping on a dime?

I have a Sojourn with the stock BB5's, and can easily do an endo if I'm not paying attention. So it's got to be your setup.
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Old 04-09-11, 03:50 PM   #11
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Really? That's good news (unless you do an endo!) I've heard the BB7s were so much better I just figured our BB5s sucked. I've learned about the discs, at least the initial installation setup. I need to play with them and learn the fine tuning like you guys said. The bike doesn't have much time on it at all (thanks, weather), if discs can be finicky I'm sure cable stretch and rotor/pad wear-in all comes into play. So the best advice is to go out and ride the hell out of my bike?

Looking forward to flying over my handlebars soon. Thanks for the tips.
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Old 04-09-11, 05:17 PM   #12
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I'm told Avid is a quick setup initially .. if the disc is flat , loosen the bolts into the adaptor,

grab the brake lever, then tighten the bolts while holding the grip of the caliper to the disc.

160 -140 sounds like a road single bike set..
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Old 04-09-11, 06:24 PM   #13
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I just put an avid BB7 on my touring bike, 160mm rotor and I"m 245lbs and it works great. I have a nashbar cyclocrossfork and it was listed as 160 mm max rotor size, I wasn't sure if it was for clearance purposes or design purposes but I didn't bother messing with it and it's great as is.

I would recommend trying to tweak adjustments as others have mentioned before upgrading.
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Old 04-09-11, 07:30 PM   #14
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And here I was thinking I was going to have to point to Santana's 250mm diameter rotors:
http://santanatandems.com/Techno/MechVsHydro.html

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Old 04-09-11, 07:57 PM   #15
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And here I was thinking I was going to have to point to Santana's 250mm diameter rotors
I don't see your point here, the OP's post was about disc brake rotors for a single person bike, Santana only manufacture Tandems and tandem related parts, so their propietary disc has no purpose on a normal bike.
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Old 04-09-11, 08:48 PM   #16
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I don't see your point here, the OP's post was about disc brake rotors for a single person bike, Santana only manufacture Tandems and tandem related parts, so their propietary disc has no purpose on a normal bike.
The OP's subject line reads "Are larger rotors possible?". I was answering that question.
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Old 04-09-11, 11:03 PM   #17
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The OP's subject line reads "Are larger rotors possible?". I was answering that question.
Ok, but if you read his post, you would have worked out that what you posted was not relevant his question; as it was about brakes for a specific bike, not a generic rotor size question.
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Old 04-09-11, 11:09 PM   #18
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Ok, but if you read his post, you would have worked out that what you posted was not relevant his question; as it was about brakes for a specific bike, not a generic rotor size question.
Since when does everything have to be relevant... especially on the Internet? Who are you anyway- Al Gore?
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Old 04-09-11, 11:31 PM   #19
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The OP asked a question, you answered a totally different one, not much help there!
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Old 04-10-11, 10:06 AM   #20
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The OP asked a question, you answered a totally different one, not much help there!
And here I thought Brits had a sense of humor.
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Old 04-10-11, 11:23 AM   #21
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LOL Jim C you are one to talk, You COMPLETELY didn't read my post a couple days ago and started answering a whole bunch of ridiculous shyte so can it please.
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Old 04-10-11, 03:02 PM   #22
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It also looks like the Santana disc has a standard bolt-pattern that can be mounted to most disc-brake hubs. All that is needed is a brake-adapter to place the caliper at right location. Certainly easier than my experiment with mounting motorcycle-brakes on my bike.



Or the the motorcyle wheel and brake.

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Old 04-10-11, 03:58 PM   #23
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You COMPLETELY didn't read my post a couple days ago and started answering a whole bunch of ridiculous shyte so can it please.
I did, and you made a bad job of asking a simple question, so you got more than you asked for, ask a simple question, get a simple answer, not as you put it; your a little close to being real offencive there.
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Old 04-10-11, 06:03 PM   #24
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Danno, you forgot the upper zip tie dude! That "mount" would fail and toss you into the weeds without it! Com'on, do it right!

And that's a nice shot of the motorcycle wheel "in" the forks...
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Old 04-11-11, 12:20 AM   #25
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Danno, you forgot the upper zip tie dude! That "mount" would fail and toss you into the weeds without it! Com'on, do it right!

And that's a nice shot of the motorcycle wheel "in" the forks...
Heh, heh...

At the time, I was looking at building a downhill-specific road-bike. Ended up modifying a downhill MTB instead. Lets me use fat 26x2.5" slicks...
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