Don't they bleed just like car brakes? Just get out the bubbles and adjust the pads so they aren't touching. Just my guess, I've never even looked close at them. I think I'm gonna end up with BB7's on my Trance just because of the cost difference and I'm going to Africa so if my bike gets stolen I'm not out quite as much.

I have heard this too, but only from other MTB riders who rode off-road--not from any specific manufacturer.

It is true that mounting huge disks on some weaker disk-brake forks can induce some scary flexing, but then again, a lot depends on the exact bicycle in question and how it's used. Do you ride hard off-road, is the bike a tandem, is the caliper hydraulic? Any of these increases stress a lot.

I have a street-only hybrid I went overboard and installed 200mm BB7's on.... I didn't bother to check if the forks were approved for 200's or not, because the bike is used pretty light most of the time. And in the few months I've been riding it, I've not seen it flex much or seen any evidence flexing was any problem.
~

I dont understand the logic behind this. It should be reverse. What happens when the 'rotor' gets so big it equals the diameter of the wheels rim..............Thats right, you get the same thing a bike with normal rim brakes gets. Why dont we ban rim brakes since they are working on a 27-28" disc, forks will be exploding everywhere !!!

Then again i may be wrong, but i don't see the logic behind thinking a larger disc causes a larger moment at the axle.

If you think about it, the higher on the fork (closer to the split in the fork), the stronger the fork is. So if you were to use a huge disc and the caliper was way up high by where a V brake would mount, the less deflection or flexing would occur. It's a leverage thing. But I'm not sure what that would do to the rest of the physics of the whole thing.

(I can see that this is kind of confusing so if you don't get it try this: Grab a fork at the dropouts and pull it apart, you get some flex and if you keep pulling you could possible damage it. Now grab it up higher, near the split, you get less flex. But I don't know what the effect would be on the QR/axle or the disc mounting bolts.)

Well, maybe you missed the part about finding hydro brake levers that fit on drop bars... ;)

Also, since this bike is my commuter/city bike, I don't want anything complicated. With the BB7, a regular allen key is all I need to adjust the cable, should I need to.


This is the bike:
http://img264.imageshack.us/img264/8781/discblt5.th.jpg

I thought BB5's needed the allen key? and BB7's had the red adjuster knobs? I have BB7's and have used the knobs and cable adjusters for all my adjustments, totally tool-less since install.

Adjusting the cable, not the pads. The cable is still connected the old-fashioned way with a bolt holding it in place.

I don't have any inline cable adjusters. The Dia-Compe 287-V levers don't come with them, and they're not available in any bike shops around here. But that doesn't matter with disc brakes. The lever itself has more than enough travel to spare, and all it takes is a small adjustment to the cable attachment to bring it up to the proper setting again.

Jarery/lucky53s: not only do rim brakes mount closer to the fork's crown,but they mount on both sides of the fork,so the stresses are spread out to both legs. Disc brakes concentrate stress at the end of just one leg.

mlh122: both BB5's and BB7's have knobs to adjust the pads,but BB5's have a fixed outer pad.

All: I can see where you'd need a stronger skewer for a bigger rotor. The skewer helps brace the bottom(tips) of the fork,so a stronger one would resist twisting better.

Nowhere have i seen concern of forks failing by snapping one fork on half due to too much stress. The concern is that the rotational force is sufficient to twist the spindle out of the fork past the lawyer lips. I may be mistaken but thats my take on the 'concern' of using disc brakes. In which case the larger the disc, the less the rotational force at the center.

Exactly!

When you apply a rim brake,the force is applied to the outer part of the wheel away from the skewer,and to both forks legs up by the crown. When you apply a disc brake,the force is applied to the center of the wheel near the skewer,and to just one fork leg at it's end. All the force is being applied in the same area,on only one side. This is why there's a twisting motion. I've never had a prob with any of my disc brake bikes(as you can see,I have quite a few),but I regularly check the skewers(both QR and bolt) for tightness.

Like I said, mine was just a guess. But I did some fun downhills yesterday with V brakes and was just fine stopping from 30+MPH. And my Pro Ouzo doesn't have disc mounts and I'm not interested in putting them on anyway. I am thinking of discs on an MTB. Either on a Fox or Reba fork. I just wanted to know if you liked the cable or hydros better in general.

Six of one,half dozen of another really. Mechanicals are easier to install,hydros require less regular maintenance. Hydros cost more and require special levers,mechanicals can use any V brake compatible lever. I'd ask over in the MTB forum which they prefer for off-road use.

Nashbar has a Juicy 5 front for $120 right now. Not the back though. And I think I saw the BB7s for $200 a pair there.

I got my front BB7 for like $70 shipped off eBay.

off topic . when did you buy this model ?
CHeers Timo

Soder = Söder? :)

The frame and rear wheel started out as a cheapo MTB-style bike (Crescent ETC 600 or something like that) in 2004. After a few months, I ordered the first of many parts to convert it to something else. After a conversion to a road bike in early 2005, I decide do start over with a new frame, and bought a Surly LHT. Most of the new parts from this bike ended up on the LHT, and the original (and only) pair of wheels from it went to the LHT as well.

After the LHT was built, I just let the frame and other parts sit and collect dust until this Spring, when I decided to build a singlespeed out of it. Which I did, using the original flat bar, and the original wheels (built a new set for the LHT the year before). Soon, however, I decided I needed drops, so another batch of new parts were bought. Finally, about a month ago, it was time for a new front wheel and a disc brake, and the result is what you see in that picture.

The only original parts left from the first bike are the frame, the headset, the rear v-brake and the rear wheel! Everything else is new. Fork, front wheel, disc brake, stem, handlebar, brake levers, seat post, saddle, BB, crankset, pedals, cassette-to-singlespeed conversion kit, chain tensioner and the tyres...

Oh, and I will very soon cut the steerer tube to a less obscene length... :D

This bike is now my designated bad weather/winter bike and general commuter, as well as a very good bike for leg training. Doing hill repeats in a 48-14 gear @ ~30 RPM is tough work, but my legs feel great afterwards. I can also safely say that this baby has made me a much better and stronger rider. I used to fear mashing - now I love it, and I'm much faster because of it!!!

In a few minutes, I'll take it out on another through-the-city ride at very high intensity. Plenty of hills in Götet, vetladu... ;)

i was going to ask about the above ^:D

anyway ,yeah Södermalm .its my turf :)

i have a Crescent ETC500 Mtn bike i have started to rip apart as well . .. throwing new parts at it here and there , but i havent really started to put the icing on the Crescent (YET) new cranks bars + stem + headset +brakes + tyres .. but i really need to get this project underway ,sommarsemester = ledigt :)

just thought i would say HI and see you in the forums .
Take it cool .
Cheers T

This link has some details on the problems of disc brakes
http://www.ne.jp/asahi/julesandjames...quick_release/

These links show the overwhelming advantage of using disc brakes

http://www.bikeforums.net/search.php?searchid=3904228

http://www.mtbr.com/techtalks/brakes/brakesfaq.shtml

http://en.wikipedia.org/wiki/Bicycle_brake_systems
http://bikezoneinc.com/page.cfm?PageID=39&faqid=42
http://www.redsofts.com/articles/rea...sc_Brakes.html
http://www.google.com/search?num=100...disc+brakes%22

I am familiar with it. Part of the reason I went with the largest possible disc was to minimise the issues mentioned on there.

CDCf.
IF your stoked , then all i can say is "WICKED m8" ..
Viva Lé Crescent ..

MVH T