auxym

Right, so my girlfriend owns a 2013 Opus Largo touring bike. It came with Tektro Oryx cantilevers which had poor braking performance. Even with the full force of my man hand, I can't lock up the front. Skidding the rear required considerable force. So, less than ideal for my petite girlfriend carrying full touring kit.

I read up a bit all over the internet, replaced the pads, replaced the link wire with adjustable yokes set as low as possible, etc. Slight improvement but nothing dramatic. So I gave in and ordered a full set of tektro CR720s which appeared to come highly recommended.

I have to say, I am much disapointed, I think they are slightly worse than the best set up I could achieve with the Oryxs. Once again, I set them up with the yoke as low as possible (as fenders allow). Tried the stock brake pads and aftermarket (jagwire mountain pro). I feel they are still not getting enough mechanical advantage: The lever travel is relatively short and feel stiff. Even with large-ish rim gap, I can't bottom out the lever.

The rims are Mavic A119, levers are Sora brifters. I'm at wit's end getting this bike to brake. Aren't cantis supposed to be strong brakes, used on tandems and such? I've read most of what the internet has to offer (notably, Sheldon's pages and that thread in the CX forum). I'm anticipating the first answer here to be to get Kool Stop Salmon pads. It was my first intention, but my LBS doesn't stock them, which is why I ended up with the jagwires. I may end ordering a set off amazon, but I feel that the fundamental issue here is the lack of mechanical advantage.

Any insight? What am I missing here?

bikeman715

with your setup how close are the pads to the rim ? closer the better . check to make sure all housing is seated and any and all adjustment barrels are half way .

FBinNY 

You nailed the problem right there. Short lever travel vs shoe travel means minimal leverage. I don't track the specs on every component, but it may be that you have a poor match between lever and brake. This is one of the side effects of the move from brake levers (which may be designed as optimal mates for brakes) and brifters which are bought according to derailleur, and may not be optimal for the brakes.

Obviously, contact friction between the shoes and rim, and overall rigidity of the system are important, but like most mechanical systems brakes are about leverage and you don't have any. I don't know if anybody still makes hanger mounted multiplier/demultiplier devices, but if they do, that may be your best option. That or scrap the brifters and buy a set of levers that pull less cable.

headasunder

I converted my old 80s mtb to a drop bar commuter, the brakes are cantilever with the original pads...braking is average at best, following the 90 degree rule gave me the best perfoemance. I bought a mini-v brake(tektro) to try on the front but it didnt clear my mud guard (it is a bodge and sits high but essential to wet commuting) so it is untried but did have good reviews....I guess its an option since v-brakes are generally a lot easier to set up

dsbrantjr

Have you tried Kool-Stop Salmon pads?

I have used these cable carriers with Tektro CR-720s and am happy with the results: Problem Solvers

techsensei

JMHO, Shimano's old low profile cantilevers work better than other designs, and better than even their current CX cantis. Their link wire set-up guarantees an excellent balance of feel and leverage. XT and LX grade are long discontinued, but used copies are always out there, and sometimes even new old stock.

fietsbob

Aero levers have more Mechanical advantage, they pull less cable with lever swing..

LARGO - Collection Adventure | Opus | Opus Bike but thats what you have,,

want to buy a different caliper?

aggiegrads

If the lever does not travel very far in the current setup, then I would try a longer straddle with the 720s. It sounds like you have plenty of mechanical advantage (lots of pad movement with little lever movements), but what you need is the ability to apply a large force to the pads. A longer cable will provide a larger yoke angle which will keep the effective "lever arm" of the brake at its longest. The closer to the bottom of lever travel you can apply the force, the better braking will be, because this is where hand strength is greatest.

SkyDog75

I've got Tektro CR720's on a bike, paired with Shimano Sora ST-3400 9-speed levers, and they stop really well. The bike on the Opus web site linked above has slightly newer ST-3500 levers, which have a small paddle for shifting instead of a thumb button, but I don't think the brake cable pull ratio is different. With a straddle cable of appropriate length, you should be able to get this dialed in.

For whatever it's worth, I've got about 11.5 cm of exposed straddle cable on each side between the yoke and the cantilever arm. I'm using the stock yoke that comes with the CR720's.

Camilo

Linear pulll (AKA V brakes) will probaby work a lot better. Someone above mentioned the compact/miniature ones which work fine with your current brake levers - but might not clear the tires and /or fenders you have.

If so, just get some full size linear pull brakes and use Travel Agents to adapt the pull of your current brake levers to the different pull of the linears. I do that on my cross/commuter bike and the brakes work very well.

Flinstone

I would say exactly the opposite of everything you said. First a high mechanical advantage means you get a SMALL output motion (pad movement) even for a big input motion (lever travel). This is what lets you get a big output force.

Second, to achieve that, you want a short straddle cable, exactly as the OP set it up. When the straddle cable is very long, you can almost move the pads independently of any motion in the main cable. That's a LOW mechanical advantage. I would also steer clear of all the arguments about moment arms. It's possible to think of things that way, but can be (and I think has been already ) very deceptive in this situation. Motion ratios give the same information and are far easier to think about here.

It's possible force is robbed in friction somewhere, cable housing. Is it also possible that the advantage is too high.. and you are running out of lever travel?

Likely a bad combination of lever and brake for your needs. As for the comment about the ST-3400 working well, yes actually shimano has been trickling down the LOWER mechanical advantage pull ratio in newer models and from their charts it's clear that the 3400 is compatible with older model brakes, where the 3500 is compatible with newer ones. I'd say it's almost certain the 3500 has a lower advantage than the 3400. The idea here was probably to shift toward generating more force at the brake caliper lever (higher advantage brakes) and less in the cable(lower advantage hand levers), to reduce cable friction. A jtek device might get you a little help but might cost as much as new brakes.

The funny thing to me is shimano lists the new levers as being sort of compitble with old brakes.. but with lower braking force. They won't list old levers as being compatible with new brakes. I guess if someone gets hit by a car they can blame the cyclist for stopping to late. If the brakes lock up and the person loses control... they get sued.

fietsbob

the change in Shimano brifters pull ratio, was mirrored in TRP mini V brakes, going from 8.4 to 9 cm in length.


Going to Straight bar levers gets you into Magura's Hydraulic Rim Brakes .

Kopsis

However it's worth noting that wide profile cantis like the 720s are relatively insensitive to yoke height (straddle cable length). This, plus the relatively low MA is what makes 720s popular for CX racing. The limited traction on a CX course usually means that absolute braking power is of little concern (and, in fact, less power is better so you're not constantly locking the wheels on loose surfaces). However, modulation (the ability to have very fine control of braking power) and mud clearance is critical and the 720s have that in spades.

If OP is looking for power, the 720s are definitely not the way to go. The Oryx with a low straddle is actually pretty good (as far as cantis go) in terms of power. The high-end setups like Shorty Ultimates or TRP ReVox may provide marginally better power (and significantly improved modulation), but if you can't lock the wheels with the Oryx setup, there's a problem that different cantis won't solve.

Miele Man

Practical Tips For Cantilever Adjustment

Adjusting Traditional Center Pull Cantilever Bicycle Brakes

Cantilever Brake Setup

The Geometry of Cantilever Brakes

Cheers

SkyDog75

I'm aware that there's a different brake pull ratio for Shimano's newer "SLR EV" brakes, but didn't think that had trickled down to Sora by the time 3500 came out in 2012. So I did some Googling to clear things up and wound up confusing myself more. Shimano's docs describe the 3400 lever pull as "Super SLR: No". Sora 3500 is listed as "New Super SLR". So they're supposedly different, but neither uses the new "SLR EV" cable pull, so how different are they?

Someone attempted to find out in this forum thread by measuring the cable pull of different levers. Scroll down to the section that talks about measuring levers' pivot length to calculate cable pull and we'll see that Shimano non-series R700 levers, which are listed as "Super SLR = no" like the Sora ST-3400's, have a cable pull between "Super SLR" levers like the 105 5600 and "New Super SLR" levers like the 105 5700. If the "non Super SLR" R700 and ST-3400 levers have similar cable pull (which I can't confirm right now), then the Sora 3400 and 3500 levers ought to be pretty darn similar in cable pull. Certainly within the ballpark that can be tuned by straddle cable length. It would be interesting to take some measurements.

Banzai

Gonna say it:

Mini-v. And don't look back. Tektro RX-5, or if you wand more bling, TRP CX-8.4. For the blingiest bling, Paul Mini-Moto.

If you get the TRPs, don't even mess with the 9.0, even with new Gen STI. Just get the 8.4.

Agent Cooper

Properly adjusted and maintained cantilever brakes will stop your bike just fine.

I would first make sure they are adjusted correctly, somebody above gave two links for that. Cantilevers can be a bit finicky to get set up but with practice it gets easy.

Aside from that, from what you've written it sounds like you took care of the usual suspects (worn cables, worn pads etc) so my best guess is to suspect the brake levers. Be sure you have the correct type of levers for the brakes. Some brake levers don't work with cantis as they aren't designed to provide the right amount of "pull." If the levers are not compatible, no amount of adjustment will help. So maybe take a second look at that.

Some levers will work with both V and Canti brakes. If your levers accommodate both there will be two places to attach the brake cable to the lever. In that case consult the manual to see which attach point to use.

And yes, I use Kool Stop Salmons with my cantilevers and they've worked well for me.

SkyDog75

If he was using a flat bar, you'd be absolutely right. But auxym is using Shimano Sora ST-3500 STI levers for road bike drop bars. Shimano STI levers for drop bars are meant for caliper brakes and are generally compatible with cantilevers since they typically require similar cable pull.

Banzai

If you MUST use cantilevers (but why?), then go with the new Shimano CX-70. Follow the directions exactly. They've taken the guessing out of it. And they work.

Flinstone

Best way to measure it is to simply measure measure how far the lever moves, and how far the cable moves. Of course pivot length is related, but so is the cables entry angle into the pivot attachment. I stick with my general philosophy that measuring movement is easier than measure moment arms. Anyway, yes it sounds a mess. I was trying to remember the super EV designation and couldn't, but that's right. I did see though that the dura ace 7900 levers are marked as having lower braking power when used with any brake compatible with the 3400 levers (including the br-3400). The 3500 however is listed as fully compatibile with BR-7900 brakes. Both nashbar and chain reaction describe the 7900 stuff as either SLR EV or nashbar lists the calipers as super slr and says they work best with the new "long pull" super SLR brifters.

So how much difference? I don't know, but there should be some difference.

fietsbob

Cable out the top road levers fall in the Middle, aero levers more mechanical advantage , pull less , V type levers pull More cable (lower MA)

Relative length of the arm, of the brake, to the pivot .. longer requires more cable Pull , Greater MA , shorter is Less.

auxym

Okay, looks to sift throught in this thread, but my main takeaway is that Shimano changed the pull ratio on the "New Super SLR Brakes/Levers", which results in poor performance with cantis due to lack of MA. Gotta leave it up to the bike industry to mess with perfectly fine standards. Plus, this fact is very little advertised, I hadn't really found out even after hours of googling. In fact, it seems even some bike manufacturers aren't aware.

So, it seems that an actual solution would involve moving away from either canti's or brifters. Or switching out the drivetrain + brifters to SRAM or microshift, who possibly still have standard short pull, but that'd be prohibitively expensive.

My partner quite enjoys brifters and isn't really interested in switching to barcons. That leaves us (well me) with finding a workable brake option. Mini-v's are an option, but compability with "New Super SLR" pull ratio seems hit and miss, except for the TRP CX-9 which isn't on TRP's website anymore (discontinued?). Shimano CX70 is an interesting option though rather expensive at over twice what I paid for the CR720's. Last option is traditional v brakes, which are rather cheap (and even plentiful on the used marker) with travel agents which add 20$ per wheel to the price, so still likely the most reasonable option (after already dropping money on yokes, pads and two sets of cr720).

I might also go back with the Oryx+yoke sitting on fender setup, it was somewhat workable. Kool-stops should help a bit more, might even reinstall some new cabling, even if they're not old, I suspect the routing is less than ideal.

Still haven't made a decision, but good to know I have options. Even better is finally figuring why I couldn't get these #### cantis to brake worth anything, when every source says they should be work fine. Thanks everyone, this forum rarely disappoints

Banzai

You don't need/want the cx-90, "super slr" or not. CX-8.4 are what you need. Tektro RX -5 are the EXACT SAME LENGTH, and are available for $20. And I can personally attest that they work GREAT. I swapped them for cx-8.4 simply for the vanity.

Google a comparison of mini-vs and cantis. It's illuminating

RubeRad

I recommend a picture of the current setup (and a picture of the previous oryx setup, if available). Maybe something is geometrically out of whack that's not coming across just in text. And if not, then all the naysayers who insist OP just set it up wrong can be quiet (or more specific)

FWIW, I have CR720s on a CrossCheck, it's 60cm and I'm 250lbs with large-ish hands (dare I say 'strong'?), and they stop me "just fine," in the sense that I am never worried about my safety, although I wouldn't say it's easy. It is quite difficult to get the rear wheel to skid, and I"m not sure if I would be able to squeeze the brakes hard enough to endo.

Banzai

Just try some RX-5s. It's a $20 gamble that you won't regret.