rear disk brake and frame breakage?

[beedo]

I have heard this is a problem, yet when I did several searches I couldn't find anything about it. So, how big of a problem is this? Please share your experiences, both good and bad, about the longevity of your rr disk mounts. I would really like to do rr disk on my 2005 norco evolve because the narrowness of the frame prevents me from using the best braking options for rim brakes - no clearance for my dx-32 rim which I am not going to part with.
Thanks in advance.....

[Gunner]

you can try it the frame just won't last thru it for to long...

[RomanC]

Many frames had the disc option but very few were designed for it. I think currently Monty, Simtra make frames that can handle the disc. (or if you can find an old Megamo)

[Sondre]

KOT MS2

[Oskar]

MBK t1000

[RomanC]

And the upcoming BT 7.0. I guess I should have consumed more coffee before I made this post.

[rav]

Ciguena 20" and Ciguena 24" fits rear disc as well

[beedo]

It looks like there is a good collection frames that can handle it, mine not being one of them!
Really, I want a good strong rim brake setup because I like the quick, responsive feel of the rim brakes on my bike. But with my wide rim and narrow frame, it looks like I can't use HS-33's, and I cannot fit my plaz crv's onto my avid v's anymore, and.....I have been advised that the plaz spanish fly v's also won't fit.

Seriously, I would really like to have someone with a similar setup as mine prove all the above info wrong by giving me advice on a setup they have used successfully......

[free_rideman]

what do you mean you can't fit your plaz crv pads on your avid rim brakes? I have two sets of avids with them right now, on my bike that I am building up.

I also don't know why you have to run a hs33?

Anyways, my front fork has a spacing of 81mm between the bosses, and my front rim is 31mm. With such a small space, I still fit the crvs. Its uber wide looking, but no reason it won't work...

(I hope I understood your prior post, and that my response makes sense)

[MultiRider]

As I understand it, the issue with disc brakes is that most frame manufacters designed the mounts with forward stopping stresses only, they didn't design for the backward pressures of trials. This resulted in the mounts ripping out of the frame when hopping in place or hopping backwards, particularly on the rear wheel. I have heard from folks on this board and Tim at Trialsin that Simtra, KOT, MBK, Monty, and the new BT Raven 7.0 all designed their rear disc mounts with trials stresses in mind. I haven't heard anything about whether Norco designed for rear stopping stresses or not.

[beedo]

what do you mean you can't fit your plaz crv pads on your avid rim brakes? I have two sets of avids with them right now, on my bike that I am building up.

I also don't know why you have to run a hs33?

Anyways, my front fork has a spacing of 81mm between the bosses, and my front rim is 31mm. With such a small space, I still fit the crvs. Its uber wide looking, but no reason it won't work...

(I hope I understood your prior post, and that my response makes sense)

You see that's part of the problem. If my rim was only 31mm wide, everything fits fine. But my rim is an alex dx-32, it is 38.4mm wide and that's where I lose my freespace. So, 38.4mm rim + my frame's bosses at about 82mm and I cannot fit my crv's anymore. I like my rr brakes with the avid/crv combo, but I can't get it rigged up anymore. Right now I am using the avid rim wrangler II's with belt dressing which works awsome, except I practice in my backyard which has alot of sand and dust. So, after a while the dust builds on the rim/pads and my brakes deteriorate quickly. This didn't happen on my other rim using the crv's. So I guess that's a :down: for the belt dressing.

I considered HS-33's as a possible option, but I don't really want a hydraulic timebomb on a trials bike, and....initial measurements by a helpful store owner sugessted that they won't fit. But, it's within a mm or two of being useable, so.......???????

Yes, I know....get a new frame.....use a narrower rim....forget that for now.

Does anyone have a narrow 80mm rr brake boss frame with a wide rim rigged up for rim brakes? What's your setup?

[RomanC]

You can file the pad spacers down or just chuck them.

[beedo]

You can file the pad spacers down or just chuck them.

With the crv's on the brake arms are at such an angle away from parallel to the frame that the alignment spacers don't even tilt far enough to align the pad. Chuck them? I tried that. When I take the spacer out completely, the pad backing goes flush with the arm surface, which fits on but is still way far from alignment with the rim. I finally saw a post about filing the spacers at an angle sort of wedge shaped to align the pads proper, but without having tried it I have some doubts about how securely the pad can be tightened so it won't move under pressure. I guess I can get a peice of aluminum rod and cut my own non-adjustable wedge spacers that make a proper angle, but what a pain in the ass............:squint:

[jmkimmel]

you could possibly grind down the pad material on the CRV to get some more room -

Also, spanish fly's are much thinner than CRV's - I'll sell you an old-ass pair for 1$ plus shipping if you want to see if they'll fit (but they're pretty much the same thickness as any regular vee pad - avid, shimano, koolstop etc.). They pretty much suck unless you keep your grind fresh though.


My vote: since you 'won't part with' the DX32, it sounds like your rear wheel is more important to you than your frame. Buy an avid BB7 with a 7 or 8" rotor, and just ride it until the thing breaks. Then, buy a proper dual disk frame.

[Meteor]

not really sure if it will help you but check out this topic : http://www.trials-forum.co.uk/forum/index.php?showtopic=85776

a guy named ''inur'' made some sort of disc adaptor on his own, would be quite cheap to make and easy to replace when your old one has broken

[reine]

In my point of view, the only frame where I can actually see that it will handle the backwards stress from trials braking is the KOT where the cylinder is mounted between the chainstay and seatstay. This must by far be the strongest method. But then again Monty and BT 7.0 etc are desiged for trials so I hope they are made to handle it! Only time will tell! I would actually be interested in trying a 7.0 with dual disc if I had the money.

[carnagr]

lol... Maybe you haven't been following the Simtra, but I haven't heard of one even breaking yet, nevermind breaking due to braking forces.

[Free-Ride-Junkie]

lol... Maybe you haven't been following the Simtra, but I haven't heard of one even breaking yet, nevermind breaking due to braking forces.

You beat me to it. I am running the HS-33 on the rear of my Simtra for now but sometime I may switch to the Hope Trial Disk....

[beedo]

The damn site logged me out and I lost my entire reply I just typed..... AARRRRGGGHHHHHHHHHHH !!!!!!!!!!!!!!!!!!

I sanded my crv's to fit - they work great now. I found out I can run rr disk on my frame from norco themselves - they have had no problems with breakage. jmkimmel - thanks for info about the flys. I don't need them, but in the future it sounds like they'd fit well. The post about the rr disk adaptor is great. I have been thinking about the same thing for a while now. Seeing someone else do it reaffirms my idea. I may barrow from the idea a bit if I go rr disk.

Thanks to All - your ideas lead me to a good solution.
Case closed.....

[goose]

I definitely believe that norco did extensive testing on the rear disc mount on their trials bike to see if it can handle months of wheel locked trialsin.

Not


That being said, good luck. Rear disc is awesome until it breaks, which it has done for me twice.

[carnagr]

I have a 203 BB7 on its way, along with a Hope laced to a Zhi :noes:

[r464]

I have a Santa Cruz Jackal that I use for urban and dirt jump, but as I progress with trials I will likely be doing some trials moves on it while I am riding. While it is not the ideal geometry to work with, it has such beefy stays that I am not really concerned about the effects of a rear disc brake being the only option.

I would be leary of doing too much on a standard mountain bike frame with ISO disc tabs that would stress the stays. I am sure that the design of trials frames in the future can take into account the forces that a disc brake will enact upon a frame. The truth is that a rim brake is essentially the same as a disc brake; it is just that the entire rim is being used as a rotor. You are getting a much larger rotor by using HS-33s or v-brakes. A disc brake can never compete with that (as long as the rim is clean, and a grind helps even more).

I have an XC hardtail with a v-brake on the rear and a disc in the front. It doesn't have disc tabs on the frame, but for riding on the trails you do not need rear brake power, so it actually saves me weight. For my trials bike, I like the huge leverage that my HS-33s give me, so I am sticking with them for now.

I have personally never seen a frame break from use of a rear disc brake. I am sure that it is possible, perhaps even probable, but I do not think it is as prevalent as the talk of it would lead you to believe. But there are a number of arguments for and against different types of rear brakes apart from this, so take them all into consideration.

[carnagr]

It's not the chainstays that get raped, it's the seatstays (not sure which you were referring to, but generally stays means chainstays).

[beedo]

I definitely believe that norco did extensive testing on the rear disc mount on their trials bike to see if it can handle months of wheel locked trialsin.

Not


That being said, good luck. Rear disc is awesome until it breaks, which it has done for me twice. :wuteva:

Hmm...I did say I'm using rim brakes and I like those best.....but hey..........