Bicycle Mechanics - 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.

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.

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.

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.

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.

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

...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?

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.

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.

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.

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.

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..

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.

And here I was thinking I was going to have to point to Santana's 250mm diameter rotors:
http://santanatandems.com/Techno/MechVsHydro.html

http://santanatandems.com/images/DiscBrake.jpg

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.

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.

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.

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?

The OP asked a question, you answered a totally different one, not much help there!

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.

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.

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.

http://i42.photobucket.com/albums/e346/DannoXYZ/Cycling/DiscBrake.jpg

Or the the motorcyle wheel and brake.

http://i42.photobucket.com/albums/e346/DannoXYZ/Cycling/DiscBrake2.jpg

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.

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! :D

And that's a nice shot of the motorcycle wheel "in" the forks... :D

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! :D

And that's a nice shot of the motorcycle wheel "in" the forks... :DHeh, 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... :thumb:

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.I don't think anyone actually answered your question fully? The answer is yes, yes and yes. Different mounts are needed for different rotor sizes. But the real question would be why? And would it be worth it? A custom-mount can be made to accommodate any size rotor and any caliper you want.

There are two benefits to larger rotors. One is increased leverage so that you can use less finger squeeze-force to generate any given deceleration-G. Given that even the smallest 140mm rotor can generate enough braking force to lock up the front-tyre or throw you over the bars with just a single finger's squeeze, leverage is not an issue.

The second, probably more important reason is rotor mass. To absorb any given amount of decelerating-force at a given G, would require generating a certain amount of heat. Larger rotors have more metal and more mass, thus they will heat up less for any given amount of heat-input. Obviously, when you've got 300-400lbs on a tandem, slowing down at the same rate will generate more heat. So a larger rotor would heat up less. I'm not sure single bikes ever heat up their discs enough to be of concern?

What is your goal with larger rotors?

http://www.jensonusa.com/store/product/BR291C01-Avid+Bb7+Mechanical+Disc+Brake+10.aspx

I just ordered two of these sets, in the mountain 185mm sizing. Both brakes came with all the brackets to fit the included rotors, whether they were installed in the front or rear.

I'm going to put them on my trike, in place of the BB5's, for much the same reason. Although I'm moving up from 160's to 185's since I'm about to add an electric hub motor.

I don't think anyone actually answered your question fully? The answer is yes, yes and yes. Different mounts are needed for different rotor sizes. But the real question would be why? And would it be worth it? A custom-mount can be made to accommodate any size rotor and any caliper you want.

There are two benefits to larger rotors. One is increased leverage so that you can use less finger squeeze-force to generate any given deceleration-G. Given that even the smallest 140mm rotor can generate enough braking force to lock up the front-tyre or throw you over the bars with just a single finger's squeeze, leverage is not an issue.

The second, probably more important reason is rotor mass. To absorb any given amount of decelerating-force at a given G, would require generating a certain amount of heat. Larger rotors have more metal and more mass, thus they will heat up less for any given amount of heat-input. Obviously, when you've got 300-400lbs on a tandem, slowing down at the same rate will generate more heat. So a larger rotor would heat up less. I'm not sure single bikes ever heat up their discs enough to be of concern?

What is your goal with larger rotors?

There's no way my brakes can be set up correctly, then! I'm not even close to being able to lock either one of the wheels up, unless I'm not on the bike and I'm just pushing it. Under load it's not even close. It stops, but the levers bottom out and it doesn't stop NOW like I'm looking for it to do.

When I picked up my bike and brought it home, the first thing I noticed was both of the wheels made a grinding sound when I spun them to check the wheels for true. Wheels are true, so are the rotors. The shop set up the brakes so the pads were constantly contacting the rotors, there was my grinding sound. The wheels would spin by hand maybe 3-4 revolutions then stop. Figuring the brakes were set up wrong, I went on a youtube disc brake learning spree. After watching a few vids, I went to work. Here's the part where you guys tell me I'm an idiot and it's all my fault. Not a problem, flame away! :D

I noticed the pads weren't parallel with the rotors on both the front and rear. The contact that was being made with the rotor was only on one side of the pad, they were "out of square".I loosened the calipers, held the brake levers and tightened the calipers back up. The grinding went away, but the levers bottomed out and had hardly any braking force. I loosened the cables at the calipers and pulled them tighter, to close the calipers more in towards the rotors when no braking was being done. Then I clicked the rear (only on the BB5) pad adjustment behind the rotors until it was as close as possible without touching.

This is as good as I can get them. They're ok for a few pulls, then the levers want to bottom out again. It's like the brakes keep loosening up on me. I've heard that new cables have to break in and slacken, but do they stretch THIS much? This is crazy.

It's kind of pointless for me to look for bigger brakes anyway, at least in Avids. I don't think Avid makes Road BB7s outside of 140 & 160mm ! The bigger ones are MTB only. If my brakes can work the way you guys keep telling me they can, I'm sure I'll be happy with the ones I already have. As soon as I figure them out!

Thanks for all the help!

There's no way my brakes can be set up correctly, then! I'm not even close to being able to lock either one of the wheels up, unless I'm not on the bike and I'm just pushing it. Under load it's not even close. It stops, but the levers bottom out and it doesn't stop NOW like I'm looking for it to do.

When I picked up my bike and brought it home, the first thing I noticed was both of the wheels made a grinding sound when I spun them to check the wheels for true. Wheels are true, so are the rotors. The shop set up the brakes so the pads were constantly contacting the rotors, there was my grinding sound. The wheels would spin by hand maybe 3-4 revolutions then stop. Figuring the brakes were set up wrong, I went on a youtube disc brake learning spree. After watching a few vids, I went to work. Here's the part where you guys tell me I'm an idiot and it's all my fault. Not a problem, flame away! :D

I noticed the pads weren't parallel with the rotors on both the front and rear. The contact that was being made with the rotor was only on one side of the pad, they were "out of square".I loosened the calipers, held the brake levers and tightened the calipers back up. The grinding went away, but the levers bottomed out and had hardly any braking force. I loosened the cables at the calipers and pulled them tighter, to close the calipers more in towards the rotors when no braking was being done. Then I clicked the rear (only on the BB5) pad adjustment behind the rotors until it was as close as possible without touching.

This is as good as I can get them. They're ok for a few pulls, then the levers want to bottom out again. It's like the brakes keep loosening up on me. I've heard that new cables have to break in and slacken, but do they stretch THIS much? This is crazy.

It's kind of pointless for me to look for bigger brakes anyway, at least in Avids. I don't think Avid makes Road BB7s outside of 140 & 160mm ! The bigger ones are MTB only. If my brakes can work the way you guys keep telling me they can, I'm sure I'll be happy with the ones I already have. As soon as I figure them out!

Thanks for all the help!

Whoops, never saw that there were follow-ups here.... You might want to check out http://www.mtnbikeriders.com/2008/06/12/thursday-tech-tip-adjusting-avid-bb5-disc-brakes/ . I found that their technique worked very well for the BB5 setup.