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Just Ride!
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Their website describes it as vertically compliant, so I assume the chain stay runs solo to the down tube and does not actually tie into the seat tube? It sounds neat, but I'm not sure about the virtual top tube specs and seat height, they kind of lost me on that one!
 

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Nice looking bike, but ey, what's with the elevated chainstay? The last time I took a serious look at one was with the haro extreme in the early 90's.
 

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Cassoulet forever !
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awai04 said:
Nice looking bike, but ey, what's with the elevated chainstay? The last time I took a serious look at one was with the haro extreme in the early 90's.
Elevated chaninstays are good on a 29er because they allow for very short chain stays.

I like this design very much, but would have bent the seatube near the BB area the other way, like on a KM !!!
 

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Early morning Coffee

20.100 FR said:
Elevated chaninstays are good on a 29er because they allow for very short chain stays.

I like this design very much, but would have bent the seatube near the BB area the other way, like on a KM !!!
Maybe it's my early morning coffee. I didn't like this design just because of the seat tube bening the other way. But my guess is it's designed for shorter people. This design creates a shorter top tube without toe overlap. The thing is that front deraileur is designed to run on a seat tube at certain angles so it got to come off the bb like that. But still you'd need a post with lots of set back

So after bad mouthing that design months ago I can say

Front Deraileur mounted correctly -Check!
Short Top Tube - Check!
No Toe overlap - Check!
Minimize Chain slap - Check!

The only thing I can't figure out is if it's designed for shorter riders, why is the head tube length so tall. maybe that's a 20" and it's designed for a 400mm seat post. (Thompson laid back would de the trick).

Like I said. I haven't finished my coffee and I'm over looking something
 

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got an email from jeff at mrazek awhile back...

he's got a concept 29er in his possession now. doesn't have a seat tube. i'm guessing it is similar to their 26 concept bike, with normal chainstays and an a-frame type seat mast.
 

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Discussion Starter · #7 ·
Hexonxonx said:
Maybe it's my early morning coffee. I didn't like this design just because of the seat tube bening the other way. But my guess is it's designed for shorter people. This design creates a shorter top tube without toe overlap. The thing is that front deraileur is designed to run on a seat tube at certain angles so it got to come off the bb like that. But still you'd need a post with lots of set back

So after bad mouthing that design months ago I can say

Front Deraileur mounted correctly -Check!
Short Top Tube - Check!
No Toe overlap - Check!
Minimize Chain slap - Check!

The only thing I can't figure out is if it's designed for shorter riders, why is the head tube length so tall. maybe that's a 20" and it's designed for a 400mm seat post. (Thompson laid back would de the trick).

Like I said. I haven't finished my coffee and I'm over looking something
I had a 26 inch Mrazek years ago and the tt length is kind of tricky. When I had my post high enough I took a straight edge from the middle of the clamp to the bb and measured the tt from there and it was 24.3 not the 23.5 that is listed.

They say there is vertical flex in rear end, I don't believe that it was flexing but the frame did ride really smooth for a al hardtail.
 

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Cool looking bike...

But the bent seat tube doesn't create a shorter toptube in any useful sense. If that were the case, I could just build bikes with 80 degree seat angles, and 21" toptubes, and have no toe overlap. Unfortunately, since you still need to get your seat back far enough to be in your normal position over the BB, the cockpit would be WAY too long. Oddly enough, they list the seat angles as 73 degrees - which would mean TONS of toe overlap on every model except maybe the large.

I had a BOH FS for a while, and despite the fact that it was so out of alignment that the shock spring was wearing a hole in one of the struts, it rode great. I'm sure they can do a cool 29er too - just take the geometry numbers on the site with a grain of salt. Looks to me like they're still in the prototype stage.

-Walt

Hexonxonx said:
Maybe it's my early morning coffee. I didn't like this design just because of the seat tube bening the other way. But my guess is it's designed for shorter people. This design creates a shorter top tube without toe overlap. The thing is that front deraileur is designed to run on a seat tube at certain angles so it got to come off the bb like that. But still you'd need a post with lots of set back

So after bad mouthing that design months ago I can say

Front Deraileur mounted correctly -Check!
Short Top Tube - Check!
No Toe overlap - Check!
Minimize Chain slap - Check!

The only thing I can't figure out is if it's designed for shorter riders, why is the head tube length so tall. maybe that's a 20" and it's designed for a 400mm seat post. (Thompson laid back would de the trick).

Like I said. I haven't finished my coffee and I'm over looking something
 

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luddite
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Not a fan of elevated chainstays

I have seen many a weed sucked into bikes with elevated chainstays. 'Round these parts tumbleweeds and sagebrush present a clear and present danger to rear derailleur health and safety.

Despite my (now solved) rear derailleur problem, I have never lost a rear derailleur due to weedsuck but my buddy who just built a Rocky Mountain ETSX-70 has gone through three derailler hangers this season due to the local shrubbery. We both ride the same trails at the same speed, and even on the same day, and though I sometimes catch a weed or two on a ride I have never seen so many broken hangers in one season. The rest of our group rides bikes with normal chainstays and avoided such catastrophies. Mr. ETSX never had such destructive weedsuck prior to becoming Mr. ETSX (he used to be Mr. Cannondale).

Left with no better option we have settled on the idea that elevated chainstays don't offer much protection from ne'er-do-well flora.

Sweet yellow paint, though.
 

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Full Circle

Walt said:
But the bent seat tube doesn't create a shorter toptube in any useful sense. If that were the case, I could just build bikes with 80 degree seat angles, and 21" toptubes, and have no toe overlap. Unfortunately, since you still need to get your seat back far enough to be in your normal position over the BB, the cockpit would be WAY too long. Oddly enough, they list the seat angles as 73 degrees - which would mean TONS of toe overlap on every model except maybe the large.
I was saying that if you built that bike with 80 degree seat tube, the front deraileur wouldn't work like it should because the trailing edge would be tilted/rotated about the BB too far up. but then I guess the seat is still too far forward of the BB so you'd end up with a laid back seat post to push the reach back to where you begin.

So now I've come full circle. Yea the seatube is on backwards.
 

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Now all tht needs is some kind of bolt-on mud screen that sends all the mud coming of the rear tire over the left side of the frame back on the trail.
I wonder how big the role is of the seat tube to make a frame laterally stiff, and thus how much engineering it takes to win lost stiffness of this setup back.
 

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Some "realistic" #'s to think about

These are some crude #'s because the only 29ers we have are frames. So, we bolted on a fork and measured away. Large frame.

Measurements are based on Maverick DUC 32 fork 6" so you can adjust accordingly.
(The Mav was the only fork we could quickly bolt on)

Eff TT: Range from 23 1/4 (Seat post down) to about 25" (Seat post raised about 5")
Seat Tube 18.5"
Chainstay 17"
Seat Angle 72 deg
Head Angle 69.5 deg

Our guess is that you'd change roughly 1 deg by swapping to a normal 4" fork.

Here's the ride scoop on the one we've ridden (have raced 26" for years now)

It's pretty forgiving. Those tubes are beefy, so it's a solid ride. The frame does weigh 4.73 lbs.

As far as vertical compliance, it does has a forgiving side, but you'd be hard pressed to notice it. It's enough to smooth out the ride a bike, especially for an aluminum bike with such big ass tubes.

We like this bike because there seems to be better power transfer when hammering the pedals (we're on SS's) and standing up than on our other 29er's. We have a Niner Scandium, which is definitely more flexy, and some GF's. Now if you want stiff, the Van Dessel Buzz Bomb we have is stiff.

Like any other bike, it depends on what you want. Mrazek hangs in there with all the others in all aspects and looks better (IMO) than the rest. It's all personal opinion anyways.

(Disclaimer, we did our measurements with a piece of twine tied through the fork dropout and the rear dropouts, so before we get called out on it, I'm sure there is plenty margin for error in our method)

alphabicycle.com
 
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