Friday, November 13, 2009

Jefe's TA fork

I get a lot of questions about 20mm through axle forks (rigid ones, that, is). Here are some thoughts and a few photos of Jefe's fork before it went off to powdercoat.

-I really think through axles are mandatory for any fork over about 100mm of travel, especially for big folks and especially on 29ers. The difference is really night and day. That's suspension forks, of course. For rigid forks, most people won't notice a huge difference in the ride - rigid setups are already really laterally stiff, even with a standard 9mm QR axle. For big or aggro riders, or folks who really want the ultimate in steering precision, though, there's no argument from me that this is the stiffest setup you can get, short of doing a rigid fork with a TA AND a 1.5" steerer.

-It's a lot of work to build the dropouts and attach them. Really small stuff (ie, pinch bolt dropouts for 20mm axles) is always a pain. It probably takes me an extra 2-3 hours of work to do a TA fork versus a standard dropout model. Consequently, they cost an extra $100. Not cheap. Probably only worth it if you're a serious snob or have a *really* fancy TA front wheel you want to swap back and forth from a suspension fork.

-The actual build process is the same as for a standard fork, but I cut off the bottoms of the fork blades at a 35 degree angle, cut a piece of .065" 4130 sheet to fit, fusion weld, and file smooth, then make a 7/8" miter for the actual dropout, which is made from (you guessed it) 7/8" 4130 tubing and a seat binder. I like to use the seat binders because the M5 bolts are a lot harder to strip or screw up than the M4s you find on a lot of stem clamps and such. The dropout has to be welded in *really* carefully (and mitered perfectly) to keep the fork in alignment and make sure the axle will fit smoothly and securely when installing the wheel. It's much, much touchier than doing a standard DO fork.

-Weight is about identical to using standard dropouts. There's probably a 10g or so difference one way or the other, depending on what 9mm configuration you compare to, but for all practical purposes, the weight is the same.

So anyway, I build a decent number of these, and I'm happy to do them in any configuration you can dream up, as always.

10 comments:

Paul T said...

I was just gonna ask you about this configuration. Freaky, must be some kind of Friday the 13th thing.

Vertigo Cycles said...

Very nice, Walt. Isn't that an M6 bolt? ;)

Walt said...

Er, uh, yes. I am clearly thinking well this fine Friday. M6 is what I meant. Duh.

Tison said...

My Waltworks 135 mm spaced front fork REALLY stiffens things up. There are more reasons for the fat fork than just the ability to run a funny looking front wheel.

Rob Young said...

Awesome. I'm considering building a segmented fork some day, I might end up doing something like this.

Rob Young said...

Ps: for ultimate stiffness.. what about a 1.5" head tube and a 135mm thru axle hub?

Walt said...

Rob -

Yeah, I mentioned the 1.5" steerer in there somewhere. Does anyone make a 12 or 15 (or 20)mm axle front hub in 135mm? I know Risse used to make a 120mmx20mm hub that was pretty nice (I have one) but I'm not up to speed on super-wide 20mm front hubs, really.

Rob Young said...

Hey Walt.

I was thinking there were single speed thru axle rear 135mm spaced hubs available, so you'd get the dishless wheel and the thru axle... It appears that most (all?) thru axle rear hubs are either 150 mm spaced, or have a cassette body (and therefore not dishless.) I guess you could go with a 150mm thru axle hub... but that seems a little wacky. I guess I'm not up on those hubs either!

I think when I make my fork, I'll go with a 135mm spacing, and use bolt on rear single speed hub. Seems like a good compromise.

Walt said...

Honestly, I think the Paul 135mm (standard 9mm QR) is probably a better solution. Bolt-on SS hubs tend to be pretty low quality items, in my experience. Plus the flanges aren't that much farther apart than the ones on a normal 110mm TA hub. Dish isn't the important thing - the spoke angle is what matters. Besides, if you're building the fork yourself, you can just build it a little offset to make a dishless setup if that's what you're after.

Rob Young said...

Interesting thoughts on building in some offset! That's a neat idea.

I suppose you're probably right about single speed hubs. Something like a surly single speed hub or a DMR single speed is about the level of gear I usually buy, so I think it'll do for me. Maybe on fork # 2 or # 3 I'll try a TA one for fun.