Wednesday, April 23, 2014

At long last: a geometry post!

Interestingly enough, I've had people start asking me *not* to do the shortest possible chainstays they can get. I tallied up the last 6 months or so worth of 29ers and the favorite length seems to be settling in around 420-425mm... which is funny, since that's what every single bike available from about 1990-2003 had. History repeats itself... but is it tragedy or farce this time around with chainstay length?

Yeah, I just dropped Karl Marx on y'all. How do you like me now?

Ok, so back to the topic at hand, which is Jackson's frame. Jackson wanted something that would inspire confidence when *charging* stuff - and didn't care too much if it suffered when ridden slowly or timidly. I have a feeling riding with Jackson is never easy.

So, the vitals:
-68.5 HTA and 98mm of trail. 65.5cm front center. Should be good if you're in attack mode, not so good for spinning slowly up a steep climb.
-60cm toptube
-42.5cm chainstays (or you can use the sliders to go back to 44.5cm)
-For a 120mm fork with a tapered steerer
-Boring 305mm/12" BB height. Jackson's local terrain would normally favor a higher BB but he doesn't like the bikes he has that sit higher so this was as low as I was willing to go.
-Clearance for fattish (2.4) tires if he wants and cable routing for 1x or SS use. Does anyone use front derailleurs anymore?
-Relatively normal XC tubeset. This bike is for hard fast riding but not hucking or taking on the chairlift.

So in short, a bike that likes to be ridden hard and fast. And a HUGE change from what he's used to (relatively steep angle XC bikes with long chainstays), so we'll hope he likes it as much as we both think he will.


Anonymous said...

WRT "does anyone really use front derailleurs anymore?"

I do...they work great. Haven't figured out all of the front derailleur hatred...maybe people just need to learn to set them up correctly. I can't remember the last time I broke or wore one out, nor had to adjust one. I have one that's been on probably 4 frames, is starting to rust through the chrome plating, and still works like a champ. I think 1x11 is great...look forward to trying someday, and the simplicity is a great thing (although the cost...yikes!). One situation where I might want to eliminate the front derailleur is on one of my short chain stay 29ers, I get occasionally get a tiny amount of tire-to-front-derailleur-cage rub when running 2.4" Maxxis Ardent tires. Other than that, no complaints with my front derailleurs...

Eric N. said...

Its not front derailleurs hatred, just simplistic 1x10 love. I have front derailleurs on a couple of bikes, but after riding a poor-mans XX1, (30t chainring and modified rear cassette 11-40t), I dont think I'll ever go back. The added advantage is less cable clutter, close to a pound in weight savings and better frame geo, in that you dont have to make comprimises on CS length and tire size/volumes.

Anonymous said...

I DO dislike front derailleurs, and I've been cycling for 27 years and a mechanic for 6 of them. A front derailleur is a fairly crude mechanism. It's biggest weakness is that has to move the chain on the side that is under pedal tension, and has the tendency to "suck" the chain into the chainstays when shifting under load. This can obviously damage a carbon fiber stay, and even an aluminum stay, in addition to often bending/breaking the chain. I admit that Shimano chainrings/derailleurs work pretty well most of the time, but front derailleur adjustment is still usually the most difficult part of setting up a bike. There is no chance of chainsuck happening while shifting under load with the rear derailleur, although it is conceivable that one could break a chain under extreme pedaling load. A single ring system allow a rider to shift through the entire range of gears when needed, under load! Obviously, shifting is a skill that is should be learned, but the more idiot proof the system, the better. And a small single ring system gives more ground clearance, to the point where I rarely need a bash guard!