26" Long Haul Trucker 650b conversion

[Christopher Watts]

Will just leave this here for now. Updates to follow after I've had chance to ride her properly.

[Igor Belopolsky]

Which bars are those?

[Mark in Beacon]

Looks sharp! I'm a fan of the Belt saddles, I think that's what you have on there?

I can't make out the brakes that allow you to go up that amount to get from 26" to 650b--I know the Paul touring has a lot of vertical adjustment, but that's not what these are? I see you really strung up the transverse cable on the rear brake to get rid of some of the excess mechanical advantage created by the low profile cantis with drop bar levers. Whoa! If you wanted to drop it down a bit, you might try a wider yoke (although maybe you already are, can't see it 'cause the tail light is in the way.)

I don't know what the frame specs are for the LHT, but how high does the conversion put the bottom bracket? 

On Monday, March 12, 2018 at 6:16:54 AM UTC-4, Christopher Watts wrote:

[Brad]

Nice.

On Monday, March 12, 2018 at 6:16:54 AM UTC-4, Christopher Watts wrote:

[Christopher Watts]

On Monday, March 12, 2018 at 12:03:21 PM UTC, Igor Belopolsky wrote:
> Which bars are those?
>
> On Monday, March 12, 2018 at 6:16:54 AM UTC-4, Christopher Watts wrote:Will just leave this here for now. Updates to follow after I've had chance to ride her properly.

Bars are On One Midge bars. Saddle is a Spa Nidd which is a Brooks B17 copy but with much thicker leather.
Brakes are Tektro Oryx Cantis. They have the necessary adjustment to go between rim sizes without any kind of tinkering.
Not sure about the bottom bracket height. These tyres are 650bx38 and was running 26x2 so doubt there is much difference.
Will post further updates after I've had chance for a couple of rides.

[Andy Beichler]

That looks great and it is interesting that the brakes have enough adjustment.  I probably won't follow through, but this answers my question about whether or not I could convert my old Diamond Back Apex to 650b without having to get frame work done.

[mitch....@gmail.com]

On Thursday, March 15, 2018 at 9:40:17 AM UTC-6, Andy Beichler wrote:

That looks great and it is interesting that the brakes have enough adjustment.  I probably won't follow through, but this answers my question about whether or not I could convert my old Diamond Back Apex to 650b without having to get frame work done.

FYI, cr720 cantis have 13mm up-down adjustment so they work for a 559 > 584 conversion if the 559 posts are brazed in the proper (lowest) position. Moving up the pads reduces mechanical advantage and braking will feel different/weaker than with pads in the lower position.

I did this conversion on an MB-1 a few years ago to try out Hetres/BSP. The LHT looks great Christopher.  

Too many good tires in 559 now to justify it for me anymore (higher BB and increased trail).  

--Mitch

[Christopher Watts]

Thanks guys. Been riding on the Trucker to work for a couple of days now and have to say it feels great. Handling is virtually the same, maybe a bit more lively. The bb is raised by 5mm but putting the change in feel to dropping 1.5kg in weight from the wheels. Previously was running heavy duty touring rims and 2" Marathon Mondial tyres and moved to Pacenti Brevet rims and Panaracer Gravel King slick 650bx38 tubeless. Speed on the flat has increased by 10-12 kph so well impressed. Added bonuses are still retaining the LHT comfort, zero toe overlap (US size 12 on a 58cm frame) and can still fit a large Kleen Canteen on the underside of the down tube. So far she's a winner.

Back to brakes apart from Tektro Oryx, Shimano CX50 Cantis also work on conversions as do the larger Promax P1 V brakes.

[Christopher Watts]

Just re-reading this. Yes have to agree brakes don't feel great. They work but don't feel as good. I did have Paul Neo Retros on there previously and they sere just sublime.

[Tai C]

Nice conversion, great to hear that it's working out for you! What's the angle of your brake cable (to left and right side)? It looks less than 90 degrees, so increasing the angle would help increase leverage/braking power. Just to add to your list, I've found that TRP Revox brakes also work well with 26 to 650b conversion.

[mitch....@gmail.com]

On Thursday, March 15, 2018 at 12:59:06 PM UTC-6, Christopher Watts wrote:

Just re-reading this. Yes have to agree brakes don't feel great. They work but don't feel as good. I did have Paul Neo Retros on there previously and they sere just sublime.

Like Tai C says, the fix is to increase mechanical advantage in other areas of the braking system. You've lengthened the lever between the canti pivot (braze-on stud) and the pad which means you've effectively shortened the proportional lever length from from pad up to the end of the canti arm. That reduces the leverage and mechanical advantage of the canti-arm segment of your braking system. 

You can get more mechanical advantage in several ways, but from your photo the easiest, quickest way is to lower your straddle cable so it's just above your fender. That gives a more direct angle of pull on the canti arms and will increase mech adv, and is what Tai is talking about with his cable recommendation. You'll notice immediately a different stronger braking feel with the low cable, and it may be the only thing you need to do to fix brake feel. Looks like you already have quality (red Eagle Claw?) pads so that's good--upgrade to good pads if you have not already. 

You might need to get longer brake cables if they're not long enough to let you lower the straddle cable that far. 

The high straddle cable set-up you have now (from your photo) is a good set-up for increasing modulation in a braking system that already has plenty of canti-arm mech advantage. It's also commonly seen with center pull straddle cables on bikes where it helps with clearing racks, etc. Height of straddle don't really affect mech adv with centerpulls much, but it makes a lot of difference with low profile style cantis on your bike. Keith Bontrager wrote about this in a piece you can find on the internet where he recommends this low straddle set up to increase mech adv. The photos attached are from Keith's article and the green monkey is showing you that lower is better. 

--Mitch

[Mark in Beacon]

Hmm. I was under the impression that he had raised the transverse cable in an attempt to decrease the mechanical advantage, as per Sheldon. But it's entirely possible I'm missing something here:

"People with brake problems often think that they need more "power," when they actually need less! In particular, when modern low-profile cantilever brakes are used with drop-bar type brake levers, the combination produces excessive mechanical advantage...

Excessive mechanical advantage can often be reduced by raising the cable yoke and lengthening the transverse cable, so that it makes a sharper angle around the yoke. Unfortunately, there isn't always room to raise the yoke far enough, especially in the rear of smaller frames. A special wide yoke sometimes helps with this. It causes the transverse cable to run at a sharper angle than it would with a conventional yoke.

If you have too much mechanical advantage, as with a touring bike or tandem with drop-bar-type levers, you can, in some cases, use a pulley adaptor to convert your conventional cantilevers into direct-pull units. Note however that a pulley will result in fatigue failure of the cable sooner or later, so check it frequently.

It almost seems like Bontrager's super low setup is trying to mimic the conversion thing above. Neither solution is likely to work with the fenders on the OP's bike (and possibly be dangerous without them?) 

[mitch....@gmail.com]

On Sunday, March 18, 2018 at 8:11:19 AM UTC-6, Mark in Beacon wrote:

Hmm. I was under the impression that he had raised the transverse cable in an attempt to decrease the mechanical advantage, as per Sheldon. But it's entirely possible I'm missing something here:

You're right that Keith's piece wasn't recommending maximum mechanical advantage for canti straddle set-up, he was just demonstrating how you could get maximum mechanical advantage with the most common low profile canti brakes. IIRC, the context was at the time people were rushing to V-brakes, saying they gave the feel of more braking power, and Keith was saying (as you point out): mechanical advantage isn't everything [you need modulation too] and that cantis can have as much mechanical advantage as V-brakes if that were the right goal... I'm glad you mentioned this so I don't misrepresent Keith's main point.  

But in the OP's case, he's reduced the mechanical advantage of his cantis by raising the pads from bottom to top of the arm in order to accommodate the extra 12.5mm radius of 584 rims, and he reported the braking doesn't "feel as good" as it should. I noticed the same thing in a 559 > 584 conversion when I raised the pads to the top on cantis, and I'm taking a guess this might have something to do with the poor braking he reported. In his case, because he has a really high straddle cable and somewhat low-profile canti arm shape, he can benefit from Keith's demonstration of how to get max mechanical advantage with straddle height.

I had the same concern you have about a low straddle height with fenders, and he couldn't get the straddle as low as in Keith's monkey demo. But from the OP's photo of his set-up, it looks like he could lower his straddle to just above the fender and reduce height by several inches, significantly closing the angle of canti-arm to straddle cable and increasing his mech adv a lot even if not to the maximum. Since it's easy and cheap, it's the first thing I'd try. In general, I think a high straddle height like that is not a good idea with lower profile canti arms anyway, so I would have suggested this on his build even with 559 wheels, unless he was trying to reduce mech adv intentionally. That straddle height works fine with wide high profile brakes because you want the angle between the cable and canti-arm about (not more than) 90 degrees.

--Mitch

[Christopher Watts]

Evening Guys

Thanks for the information regarding the straddle cable height. Right now the brakes aren't the greatest so will heed your advice. Brakes work fine but you do need to give them a good squeeze to get the best braking.

The bike itself does ride very well. Managed to fit in a 100km ride after work last week to get a proper feel for the wheel change. The lighter wheels do make a big difference. It is a Trucker after all so is definitely more cruiser than sprinter. Totally sold on the 650b concept now