Opinions on trail, 650b tires >42mm, and gravel

[Daniel Jackson]

There is a current iBOB thread that is drifting in and out of this topic, but the OP is specifically about bikepacking. I'm starting this thread here to query the group on experience with fatter 650b tires and low trail gravel machines with the goal of designing a custom.

I've been experimenting with two machines on loose dirt and gravel in the far reaches of the rural northeast US of A:

1. a 700c 38mm tire, light tubed machine with a trail of 40mm (someone else's custom reject)

2. a 700c 60mm tire, relatively heavy tubed machine with a trail of about 68mm (Rivendell Hunqapillar)

Rutted out roads, variably graded with the odd patch of large (golf ball) sized stones are the norm. We've also got solid dirt packed tight in areas with better drainage. And there is pavement here and there that is heaved to high heaven. I typically front load about 15-25 lbs. for any ride. With the Hunqapillar I'm often carrying another 10 lbs. in the trunk for overnights, etc.

The low trail machine climbs like a champ, tracking straight at slow speeds with little corrective input needed. On pavement, it turns gracefully at speed with little input, holding a line until you change it. Straight lines at very high speeds (40 mph) hint at shimmy. On dirt, the bike tends to washout quickly up front and steering even at speed is generally vague - a sensation almost akin at times to riding on ice. Without a front load, these cons are exacerbated. 

The Hunqapillar climbs less champ-like, the front more apt to wonder like a mind chock full of social media. On pavement, it turns itself - you just suggest a direction and the turn begins. BUT, lest you be taken to some dark dark place where Grant Petersen's B-Stone demons reside, you better continue to direct the bike through the turn, for it will otherwise tend to sink with ever decreasing radius into a black hole. Of course, this flopping tendency in exacerbated by high loads up front. On dirt, there is never any washout, steering at speed is rad, straight lines at high speed are bomber, and the aforementioned black hole tendency is rare. Interestingly, a load up high behind the steering axis (aka a toddler), improves slow speed handling. 

Of course, there are other variables besides trail that must determine the ride on these bikes - where my weight is distributed, tire size, chainstay length, tubing, etc. - but I have a sinking feeling that trail is the main determinant of the handling traits I've described above.  

I'd like a bike that bridges the gap here, designed specifically for dirt with front loads. Compass Switchback Hills are the name of the game, and I'd like help picking a trail number. If you would, please pitch in here about your preferences and experiences with trail. Your descriptions might touch on the following themes that I've outlined above:

- washout tendency

- climbing prowess

- stability at speed

- tendency to hold a chosen line

- are current low trail trends biased by there less than or equal to 42mm tire past?

And if I just have to pick my demons and roll with them, then let me know that too...  

Thanks folks,

Danny J. in Vermont's Northeast Kingdom where the pavement never begins.

  

 

[Brad]

Your experience with low trail tracks mine with wider 650B tires.  I like it.
Where in the Kingdom are you?
I am over in the North Country (New York) where the rivers also flow north.
Howard Frank Mosher actually moved to the Kingdom from around here.

[Daniel Jackson]

I'm at the Kingdom's western edge along the Green Mountains - Montgomery Ctr./Westfield line. Where is this mythical Mosher? Where are you in NY?

[Guy Washburn]

I'm liking SwitchbackHill tires on my Elephant NFE which uses a fork rake of 65 (trail of 36, head tube angle 73degrees). Very nice with minimal to moderate front bag weights. Haven't owned it long enough to have a heavier weight up there but I'll bet that would be fine too...

[mitch....@gmail.com]

On Monday, August 15, 2016 at 7:41:44 PM UTC-6, Daniel Jackson wrote:

There is a current iBOB thread that is drifting in and out of this topic, but the OP is specifically about bikepacking. I'm starting this thread here to query the group on experience with fatter 650b tires and low trail gravel machines with the goal of designing a custom.

I've been experimenting with two machines on loose dirt and gravel in the far reaches of the rural northeast US of A:

1. a 700c 38mm tire, light tubed machine with a trail of 40mm (someone else's custom reject)

2. a 700c 60mm tire, relatively heavy tubed machine with a trail of about 68mm (Rivendell Hunqapillar)

I like how you framed the question better. 

 

Rutted out roads, variably graded with the odd patch of large (golf ball) sized stones are the norm. We've also got solid dirt packed tight in areas with better drainage. And there is pavement here and there that is heaved to high heaven. I typically front load about 15-25 lbs. for any ride. With the Hunqapillar I'm often carrying another 10 lbs. in the trunk for overnights, etc.

The low trail machine climbs like a champ, tracking straight at slow speeds with little corrective input needed. On pavement, it turns gracefully at speed with little input, holding a line until you change it. Straight lines at very high speeds (40 mph) hint at shimmy. On dirt, the bike tends to washout quickly up front and steering even at speed is generally vague - a sensation almost akin at times to riding on ice. Without a front load, these cons are exacerbated. 

The Hunqapillar climbs less champ-like, the front more apt to wonder like a mind chock full of social media. On pavement, it turns itself - you just suggest a direction and the turn begins. BUT, lest you be taken to some dark dark place where Grant Petersen's B-Stone demons reside, you better continue to direct the bike through the turn, for it will otherwise tend to sink with ever decreasing radius into a black hole. Of course, this flopping tendency in exacerbated by high loads up front. On dirt, there is never any washout, steering at speed is rad, straight lines at high speed are bomber, and the aforementioned black hole tendency is rare. Interestingly, a load up high behind the steering axis (aka a toddler), improves slow speed handling. 

This is the contrast I'm interested in too: moderately fast wide-tire descending on loose dirt. Your experience has been similar to a few reports I've read. Other reports show low-trail wide tire descending on loose dirt is solid and stable, or at least without problems.

There aren't that many low-trail wide tire bikes so maybe there is limited experience. Some members have lots of experience on dirt with low trail customs, and Mike S reports all is good. Some builders seem to favor low trial generally but choose high trail for their bikes they intend for speedy dirt descents. Seems like we would have heard of problems from the many NFE riders here. 

My own experience with low trail dirt descending is recent (recently set up two bikes), and has been marred by braking limitations so I don't have your clear impression yet.

I'm thinking of this as mainly a trail-figure issue but maybe there are other more controlling variables that result in the different reports. 

--Mitch 

[Marc Pfister]

On Sunday, August 21, 2016 at 12:20:06 PM UTC-6, mitch....@gmail.com wrote:

This is the contrast I'm interested in too: moderately fast wide-tire descending on loose dirt. Your experience has been similar to a few reports I've read. Other reports show low-trail wide tire descending on loose dirt is solid and stable, or at least without problems.

I have a custom low trail (31mm) bike with Rat Trap Pass tires. I don't notice the front end prone to washing out.

On dirt and gravel roads the low trail works well for me. If the front wheel slips sideways the bike doesn't try correct and tank-slap. I can correct as needed or just shift my line sideways a little. I think the fat tires help too - the bigger contact patch seems to reduce the amount of sliding around which I assume is when the road surface can no longer support the load. It's especially noticeable in sand.

In more technical situations with things like ruts and rocks, I don't think it's as good because it requires too much active management. You can't devote as much attention to picking lines. In really rough spots on a high trail bike you can use your arms to hold the front end steady and make adjustments with hip steering. It will also tend to at least go in the same direction when you're not able to pay full attention. 

- Marc