Rear Disc

[Bryan]

And if so, should I use a +40mm mount, a +43mm mount, or something smaller?

Discuss. Reasons for the opinions would be good, too. Mmmm, reasons.

This is on a stock.

[firewrx612]

What are your reasons for switching? I'd say if it's better braking you want, switch to V's. I've never tried rear discs on a trials bike, but a v-brake is probably an easier switch to make and I can't imagine any brake working better than the set-up I have now. My admittedly limited experience with discs, tells me they're more of a hassle to setup and maintain than V's as well.

[PJL]

I don't know about on a stock, but with 185 avids on my mod, it doesn't get much better. I pretty much stopped riding my stock bike now because the brakes suck so much in comparison.

Get the largest rotor you can; the mount's location isn't tooo important imo.

[eastside]

IMO, Disc is easy to set up. But will it be as hassle free as -V- or Maggies. Or will it have the shear locking power. I will try rear disc for a bit, just out of curiosity.

P.S. Magura make's a 210mm rotor upgrde for most of their brakes :eek3:

This is what I will most likely rock!

[RomanC]

I think there are a few threads on this topic already. Rear discs (read. Avid BB7s) are very hassle free and require almost no maintenance. They are however not as strong as soft pads/harsh grind, but they are quiet and work well in the wet. The downside is that you have to check the wheel more often than with rim brakes. (loose spokes)

[goose]

Ya, please search for threads, cause this debate has happened many many times:
http://www.observedtrials.net/vb/showthread.php?t=10704&highlight=rear+disc+silent

Personally, I found a rear 8" bb7 preferable to my grind/V setup. Megamo and Simtra frames both have well designed +40mm IS disc mounts, and they have both proven to withstand trials braking. Just going to +40mm IS isn't the only part of the equation, you also need a well aligned truss to prevent the torque rotation from tearing the welds. Look at the alignment of the truss on the Megamo mount, and notice that it's nearly tangential to the point of contact between the pads and the disc. That's smart, cause it requires, what appears to me to be a geometric minimum of force (thanks to FelixM for the picture):
http://www.observedtrials.net/otn3/megamo_felixM_side.jpg
(http://www.observedtrials.net/vb/attachment.php?attachmentid=862&stc=1&d=1104961143)

[chronic]

I tried it for a while on my simtra. I only tried a new juicy 7. And honestly, the braking power in terms of forward wheel motion was amazing.

But any weight on the wheel backwards it would not hold shit! I only used it for a bit over a month before I cut the line and put it on my front wheel.

But even a friend of mine has been using a rear disk now for quite some time, maybe two-three months. And his wheel has a really hard time holding when it rolls backwards. Thats why..I didn't even want to try anything else.

Maguras have never failed me. I just wanted to try disks. Maybe avid hydraulics weren't my best first g/f. But regardless, in my mind the comment "if it aint broke, dont fix it" comes in sight, So... I dont particularily fancy the idea.

[RomanC]

i find that you have to set the inner pad really flush with the rotor so that it doesn't loose grip too fast when rolling backwards

[Bryan]

Thanks for the responses so far.

I realize that this has been discussed before, but the main questions I would like to address here I couldn't find in older topics. I am going to switch to a new frame some time in the next six months or so, very probably custom steel. Because of this, I have the opportunity to run a rear disc on mounts that I design myself and therefore (knock on wood) will not break.

The questions not adressed elsewhere that I am specifically looking for answers on are the following:

Is it unwise to use a +43mm mount? Would there be any forseeable reason to want to run less than a 203mm disc?

What calipers would be recommended? I hear that the hope mono trial rear caliper tends to leak. I also would prefer not to run a mechanical disc. Is there any one of the magura offerings that is preferred? Or is it impossible to run rear hydraulic disc without having to replace calipers every six months or so?

Having to check wheel tension doesn't bother me. I am already a freak about having my wheels set to high tension.

Also, as for the movement with pads clicking back and forth within the caliper: this happens on my current set of maguras too, so it doesn't really bother me.

The main reason for switching is: Because I can. I am getting a new frame eventually anyhow. Aside from that, I am sick of buying a new set of pads every 1-2 months, grinding, using the turbo pad adjuster, resetting my 4- bolt mounts, etc. Also I hate Vs universally and admittedly somewhat irrationally. I have never felt a set of Vs I liked. I do love the feeling of my front hope disc. Having the same or similar in the rear would be a dream.

[Oskar]

I hear that the hope mono trial rear caliper tends to leak.

The front and rear calipers are the same, I have had a 2005 and a 2007 mono trial and none of them have leaked.

Also why would you want a +43mm instead of +40mm??? Get a normal +40mm...

[Juhan]

a 203mm OLDER avid rotor(not that ugly-as-fuck new curvy rotor, but the older one) fits a simtra with an 2006 hope monotrials rear...

[goose]

the difference between +40mm and +43mm equates to only 1.5mm on the radius of the disc. Riders of simtra and megamo have used used both 200mm (hope, magura) and 203mm (avid, hayes) discs. It's safe to say that a +40mm IS mount will work for both. Juhan's experience is consistent with many others who've done it.

I feel like for pure competition style trials, rear disc is sorta silly because good trials pads with a grind/score work so well, so many purists stick to magura/Vs. If you like streety stuff, or just want a change, maybe disc is a good call. I personally ride more than just trials, and I appreciate the modulation and lack of noise that a disc gives you. It certainly isn't as 'rigid' a feel as a rim brake is, due to spoke windup, and there is usually some amount of pad wobble.

[MultiRider]

The Hope Mono Trials brakes on my Simtra lock hard and are pretty much trouble-free and maint-free. I chose dual disc because I wanted low maint and silent running.

[RomanC]

I think a +40 mount is a way to go. Most rotors have a large enough surface area so that exact alignment is not required

[goose]

I think a +40 mount is a way to go. Most rotors have a large enough surface area so that exact alignment is not required

I agree on both counts:) I just measured my hayes rotor, at 18mm wide, and my ebc pads at 16.5mm wide, FYI.