Monday, September 13, 2010

Bike check: Skippy's (demo) LenzSport PBJ.

A little over a year ago I convinced Devin Lenz to build a 7" travel 'park bike'. Almost immediately after taking delivery I pointed myself north and rode it for a few days in Whistler. The experience of riding in Whistler is not likely to be duplicated in many other places on the planet--so big, so fast, so steep, so much slippery rock, often so little traction. And the trails--so much variety, all of it challenging. It is the most demanding riding I've ever done when you factor in bike, body, and mind. Body and mind get to rest and recover *a little* every night, but the bike just keeps getting pounded relentlessly.

So it was with mild elation that I finished last year's trip unscathed and reported back to Devin on how the proto park bike performed. Devin took that feedback and mixed in a little mojo to create some more refined prototypes. These were disseminated last fall and ridden heavily from Denver to Moab and lots of mountainous places in between. Over the winter Devin took that feedback and made some final tweaks to the geometry before releasing them to the public this spring. I bought one of the first production bikes to have as a 'shop demo' of sorts.

Which has worked out pretty well for Skippy. He piloted it a few times at Trestle Bike Park this summer--enough 'to get a feel for the way it flies', which seemed to be his main concern. He's ridden rental 26" DH bikes on all of his previous trips to Whizzler, so he has some basis for comparison. When we started hammering out the details of this year's fall Whizzler trip, he expressed (significant!) interest in an extended demo session on the PBJ. I didn't see a good reason to leave this bike at home when A. We had room in the truck and 2. It was/is tailor made for the riding we'd be doing. So we brought it, and he's been riding it.

And I dare say he has been ripping on it. I'll have some video after the trip is over that shows (far better than my words ever could) how big, how fast, and how far he's been pushing this bike. For now, a few pics to answer the nitty gritties about the bike itself, accompanied (below) by some words from the horse's mouth.

The frame is a size medium. The fork is a White Brothers Groove 200. That's 8" of fork travel to match the 7 inches out back.

About the only 'personal tweak' he's made to the bike is to rotate the bars into this position:

They look uncomfortable as all get out *to me*, but I don't have to ride it and they sure aren't slowing him down any.

Front hub is a 36h DT 440 in 20mm thru. Rim is a Sun MTX 33. Spokes are DT Competition butted, laced 3x. Nips are DT aluminum.

Saint 170mm cranks, 32t ring, MRP G2 guide, and Mallets.

Vivid coil shock with 550# spring and medium drop-stop bumper.

One of the more unique features of this bike is the rear hub. It is a very rare iteration of the DT Swiss 440 FR. This one is 150mm spaced, but uses a single-speed freehub body, so you get (duh--LOOK at it!) MASSIVE flange spacing, which gives you a ridiculously stiff, strong, and durable wheel. This hub is actually only available in 32h, and I've laced it to a Salsa Semi rim (that's a light XC rim, folks) using DT Comps and DT alloy nips.

I've seen what Skippy has done to this wheel the past few days (think landing sideways at 25mph about 150 times per day...) and I've checked it over to find it still perfectly round and true. From that I can only conclude that it is the most durable wheel necessary for this sort of thing. And even though the rim is but a scant ~550g, this is probably the most durable wheel I've *ever* built. Really. Sure, I could build it heavier, and for a 350# rider I just might. But for Skippy it's plenty.

The SS freehub body means you're somewhat limited with gearing selection. I wanted to keep this setup simple and functional and duplicable (in case of crash or failure) so I just mined 5 cogs from a stock SRAM road cassette. That's a 12-27 spread on there--plenty of range for park riding and even *some* self-shuttling. Rear mech is a Saint short cage, moved by a SRAM Attack twist shifter.

Brakes are Avid Code, 8" up front and 7" out back. The rear brake has had a disconcerting resonance from the get-go. Fine-tuning the relationship of the caliper to the rotor has made no difference. Swapping sintered pads for organic made no difference. Replacing rotors *and* pads at the same time has made no difference. Plenty of power, plenty of modulation, just a really, really annoying noise that can be felt *and* heard when riding.

Rock Shox 12 x 150mm Maxle ties the rear end together. These seem to get overlooked or glossed over for some reason, but I think they are one of the brighter bike inventions of the past few years. Simple, durable, even elegant, they add stiffness where maybe you didn't even realize it was lacking.

Post is a cheapie Truvativ cut pretty short. Saddle is a big honkin' Bontrager Earl because bigger is better for park riding.

Cane Creek 110 HS, Funn direct mount stem, Sunline V1 semi-flat (not-so-rise?) bars, inverted to keep the front end height where he wanted it. Full/unbroken housing run from the shifter to the rear der. Clean.

Shod with WTB Dissents in 29 x 2.5", and running Bontrager 29 x 2.1" XC tubes at ~25ish PSI.

Great--that's the machine, but what does the rider think of it?

Here are some of his random thoughts:
Fork? "Buttery smooth on small stuff, bottomless on big hits. Normally after a few days in the park my hands are killing me. Not this year. Only complaint is the thru-axle install/removal seems not very well thought out."
Rear shock? "Invisible--just does it's job without noise or complaint. Very nice."
Tires? "Great in the slop, great in the dry, no complaints."
Brakes? "Noisy. Power is good, modulation is good, just too noisy."
Gearing? "Perfect for park riding. On occasion I wish I had a few easier climbing gears so that I could self-shuttle. But then I'd have to pedal a 40lb slammed-post bike uphill!"
Wheel flex? "None. Zero."
Chain guide--any noise, slap, derailments? "None--seems to be a zero-maintenance system. I like that I haven't thought once about it 'til you just asked me."
Given a clean slate, what would you change? "Brakes, to something that doesn't scream at me, and the fork thru-axle to something quick and easy like a Maxle."
Any interest in going back to a 26" DH bike? "My only interest would be to compare them in the air on big booters, tables, gaps. But I don't see going back to 26".
Care to comment on 26" vs. 29" for park-sized braking bumps and chop? "No comparison, 29" is worlds smoother."

Great to get such unfettered feedback.

And now, it's getting to be that time--lifts open in 45 minutes!