Two Wheels - Six Strings

Random news and thoughts about various two-wheeled projects and music, especially my band, Skull Full Of Blues.

Wednesday, January 21, 2009

Stumpjumper 29er

Okay, I'll admit it; I can be somewhat obsessive at times. I'll get an idea in my head, and it just won't leave me alone. Sometimes, I can overcome this, and other times I work for months on something which, really, is just not that important. This is one of those projects.

It's the StumpJumper I just built up, the other night, converted to 29 inch wheels and tires. I had only built it up because I was so aggravated that I couldn't get it to work as a 29er. Then...a breakthrough!

Let me back up a bit. A while back, Frankenbiker contacted me, looking for a frame and fork to use as the basis of a monstercross bike. He hoped to be able to run 29er tires, with a fixed/free flipflop wheelset. Unfortunately, the only donor bikes I had would only run 700x35c or 40c tires, and had vertical dropouts.

But, I have a plethora of vintage mountain bikes with horizontal drops. Would one of them work? I mounted up some 29x2.2" tires on a spare wheelset and started experimenting. I found that I could shoehorn the tire into the rear of the Stumpy, but the fork was a different story. So, I started searching for a 1" steertube fork which would accept a 29er tire.

After trying every fork around the place, I figured out that nothing I had would work. So, I started looking for one, online. Finally, I decided to try a Kenesis cross fork. I had used the 1-1/8" version on Dan's On-One, so I figured it might work. Eighty five dollars later, I had one on the way.

Unfortunately, the smaller steerer tube apparently moved the curves of the fork legs closer together, and the 2.2" tire just wouldn't work. Hmmm...

Here's where the obsessive stuff starts. The fork won't work with 2.2" tires. Fine. I'll get some 2.0" tires and see how that works.

I found a pair of Kendas, cheap, on eBay and hit the Buy It Now button. (One hundred ten dollars spent on this , so far.)

I hoped that they would arrive by the weekend. Unfortunately, they didn't. That's why the bike got built up with the 26" wheels.

The Kendas arrived, yesterday. And, with a bit of manipulation, they work in both the fork and the frame.

There's not a whole lot of clearance to be had at either the the fork crown...
or in the rear triangle. You certainly wouldn't want to ride in muddy conditions. And you'd better not knock your wheel out of true, either.

I was able to retain the XT V-brakes on the front, since the fork is built for 70oc wheels. The rear triangle of the frame, though, was obviously built for 26" wheels, and the brake studs are too close to the axle to allow the pads to line up with the rim.

But, again with the obsessive personality...I had made adapters, weeks ago, to move the brake pads on cantilevers up to 700c level on a mountain bike. Just because... y'know...

The two lower bolts mount the adapter plate to the Avid Shorty. The brake pad then mounts in a slot, allowing fine vertical adjustment, just like the original slot in the brake arm.

I had to use the cantilevers, rather than the V-brakes, because the tire is taller than the V-brake arms and the cable can't run across it. Luckily, the added leverage on the pads allows the use of the V-brake lever with the cantilever brake. Usually, that doesn't work, at all.

Another view of the brake pad adapter.

So, the bike is rideable, but not quite finished. I still need to do a bit of frame tweaking, and gearing (it's currently a freewheel, as I didn't have time to swap out the fixed cog from the other wheelset).

I don't know that I'll leave the bike set up as a 29er. It makes the bike a bit big (the freaking bottom bracket is 13-1/4" off the ground, and the standover height is a tad high). I may revert it to 26" wheels, and do the 29er conversion on a smaller RockHopper I have out in the storage.

But, the important thing is: I won! Yeah! In your face, Stumpy! I knew I could make you into a 29er!!! Bwahahahahaha!!!

x

6 Comments:

At 10:13 PM , Blogger katina said...

well, sometimes you have to take your victories where you get them. even if they are over inanimate objects... :)

 
At 10:57 PM , Anonymous red light green light said...

Jon,
You are a freekin Mad Scientist Madman... But we love you anyways....

 
At 5:52 AM , Blogger frankenbiker said...

I agree with red light green light,You can get just about anything to work eventually.You are the bike Mad Scientist!

 
At 8:40 AM , Blogger Brad said...

Dr. Dremel your patient is prepped and ready.

 
At 3:56 PM , Anonymous Anonymous said...

FYI: you can run v-brake levers w/ cantis if you use Avid Speed Dials--maybe other levers that have reach adjustment. I have a supercruiser (1971 Schwinn American) with speeddial 7s hooked up to a BMX brake in back and a canti in front (Surly CrossCheck fork). Works just fine.

 
At 7:34 PM , Blogger Jon said...

Yeah, I've used Speed Dials for that purpose. I was just referring to standard V-brake levers.

On the other hand, I actually kinda prefer standard canti levers with V-brakes, myself. You get a lot of modulation on the trail, even though they seem mushy on the showroom floor.

 

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