B52 stealth bomber CX build

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B52 stealth bomber CX build

Postby m@ » Mon Sep 01, 2014 4:44 pm

So a while ago I picked up a cheap carbon CX frame via Fleabay, with the plan of swapping over the original wheels from my Giant Anthem 29er and groupset from my Kona Honkey Inc.

Last week, after a few setbacks, new parts and ultimately outsourcing the hard work to the awesome folk at my LBS, I picked up the first incarnation of this weapon 8)

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The wheels worked like a dream with @silentbutdeadly's help to convert the front down to a 9mm QR; 3T stem and bars were donors from my CELL roadie, along with 105 brifters and BB-7 cable disc calipers and rotors from the Kona. A few surprises along the way - 31.9mm seat tube gave me the excuse to buy a matching 3T carbon post; I discovered that ten-speed MTB derailleurs use a different cable pull ratio to ten-speed road shifters, so it is running a nine-speed cheapie until I get around to modifying my XT shadow plus RD. Also had to buy a new front derailleur as the cable routing is top-swing and the seat tube diameter wider than either donor bike... Gearing is a tad esoteric at this stage - standard road chainrings with the 12-38 cassette from my 29er to give useful ratios.

The Schwalbe Evo RaRas are running tubeless, though not marketed as tubeless ready... Took longer to seal up than the MTB variant, but pretty much stopped losing air after the first ride. Roll well with plenty of grip on the trails, so should be great for actual CX.

Got it dirty the next day on a roll along the Yarra Singletrack and Hans's Loop - looking forward to some real CX!
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by BNA » Mon Sep 01, 2014 5:00 pm

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Re: B52 stealth CX build

Postby mitchy_ » Mon Sep 01, 2014 5:00 pm

very nice. a well set up CX is a great bike to have... mine is soon becoming a favourite in the fleet.
for what it's worth, sram road and mtb 10 speed play nicely.

my only gripe, your valves aren't perfectly lined up between the 'W' and the 'A' of Schwalbe :lol: damn OCD.
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Re: B52 stealth CX build

Postby m@ » Mon Sep 01, 2014 5:21 pm

It is heaps of fun to ride - I am seriously reconsidering whether I need a 29er XC MTB now...

Hmm, another excuse to upgrade to those R700 hydro brifters... only problem is it'd cost almost as much as the entire build to date.

Haha, I will point out the valve misalignment to the guy who built it on the next shop ride ;)
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Re: B52 stealth bomber CX build

Postby mitchy_ » Mon Sep 01, 2014 5:41 pm

i've been tempted by the same hydro shifters... however if i was going to lay down that sort of coin, i'd splurge a bit more and go for 11 speed as well. (sram 10spd road & mtb, 11spd road only is interchangeable as well. :wink:)
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Re: B52 stealth CX build

Postby silentbutdeadly » Tue Sep 02, 2014 10:01 am

m@ wrote:It is heaps of fun to ride - I am seriously reconsidering whether I need a 29er XC MTB now...

Hmm, another excuse to upgrade to those R700 hydro brifters... only problem is it'd cost almost as much as the entire build to date.


Glad to have helped...even just a little.

You still need a 29er XC MTB...mine is still faster than the cross bike on the same courses!!

As for the shifters...if you can cope with SRAM then Apex or Rival brifters play well with X9 Type2 MTB rear derailleurs (and will still work with the new FD).

However, my cross bike runs a stock road RD (Rival) and the commuter has non clutched XT 1x10 (without a chainguide) and neither has problems with chain drop and slap despite bashing around our riverfront XC tracks...so I'd just go a stock 105 instead.
Ours is not to reason why...merely to point and giggle
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Re: B52 stealth bomber CX build

Postby Calvin27 » Tue Sep 02, 2014 11:38 am

My current frankenbuild was going to stick to shimano (cheaper) but could only manage to wrangle 32t max. I didn't fully run it, just borrowed a wheel/cassette and tried it out with my derailleur from another bike shifted on the stand and didn't ride it. It should be fine though I've seen some 10sp shimano RDs go up to 32t on stock bikes. 30t is very common on sportif (relaxed) roadies. I didn't have a 34 but 36 was not having any of it. In the end I just went to SRAM.
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Re: B52 stealth bomber CX build

Postby m@ » Tue Sep 02, 2014 2:48 pm

Electronic/hydro SRAM would be the aspirational choice ;) I have a SRAM X9 type-2 RD, but that's going onto the MTB with gripshift to hopefully sort out my wrist problems... if I don't like gripshift, I guess it could go onto the back along with those SRAM S700 brifters and Red brakeset, and the Anthem can keep its XT :mrgreen:

Saint 9-speed (clutched, but not as good as shadow-plus) was the recommendation of the mechanic who built it up for me... the mod to shorten the effective lever length of a Dyna-Sys RD looks relatively achievable though, so I might give it a go as I will have a spare anyhow. A clutched RD is no doubt unnecessary, but I'm a touch particular about the frame, especially being CF... reminds me that I need to get an old road tube onto the stay before tonight's ride...
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Re: B52 stealth bomber CX build

Postby silentbutdeadly » Wed Sep 03, 2014 11:23 am

m@ wrote: A clutched RD is no doubt unnecessary, but I'm a touch particular about the frame, especially being CF... reminds me that I need to get an old road tube onto the stay before tonight's ride...


Even with a clutched RD you'll get chain slap. How much depends on your ride style. The 'clutch' only controls the chain coming from the crank - the bottom half. The top half is free to slap if you aren't putting the power down...and any look at an unprotected chain stay will show you that this is where most slap comes from anyway...
Ours is not to reason why...merely to point and giggle
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Re: B52 stealth bomber CX build

Postby m@ » Thu Sep 04, 2014 1:57 pm

Good point... dang, guess I still have to work on my skillz. Got a fair amount of chain slap riding some singletrack on Tuesday (Hans Memorial Loop for Melburnites); really must get a tube on that stay! Doesn't really help that unless I crosschain, it's hard to keep pedaling through rough stuff in the big ring (guess I need to work on putting down more powaaaa).
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Re: B52 stealth bomber CX build

Postby mitchy_ » Thu Sep 04, 2014 2:18 pm

silentbutdeadly wrote:
m@ wrote: A clutched RD is no doubt unnecessary, but I'm a touch particular about the frame, especially being CF... reminds me that I need to get an old road tube onto the stay before tonight's ride...


Even with a clutched RD you'll get chain slap. How much depends on your ride style. The 'clutch' only controls the chain coming from the crank - the bottom half. The top half is free to slap if you aren't putting the power down...and any look at an unprotected chain stay will show you that this is where most slap comes from anyway...


even if you're not pulling on the top chain with the crank, the clutch will keep the entire chain tight as the hub's freewheeling motion will allow it to tension the chain backward as well.
the clutched mech on my MTB never used to get chain slap on the top anyway...

feel free to sell me the X9 however, M@. ;)
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Re: B52 stealth bomber CX build

Postby silentbutdeadly » Fri Sep 05, 2014 2:13 pm

mitchy_ wrote:the clutched mech on my MTB never used to get chain slap on the top anyway...


It almost certainly slaps/slapped but it may well be one of those frames that has decent chain/chainstay clearance. Neither of my MTB frames is one of them but the cross bike & ghettograveller have a large gap due to the bigger rings and smaller BB drop (?) and the chain rarely contacts the top of the stay.
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Re: B52 stealth CX build

Postby jazgtir » Sun Sep 28, 2014 11:55 pm

m@ wrote:It is heaps of fun to ride - I am seriously reconsidering whether I need a 29er XC MTB now...


Just throw some flat bars on it and...SNAP we could have matching bikes and you get basically a 29er:)

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I'm now running an X9 in the rear. Other pics with slicks are in the gallery.
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Re: B52 stealth bomber CX build

Postby m@ » Mon Sep 29, 2014 6:29 am

Right down to the eggbeaters and Fyxo bidon - awesome! Wonder if the frames are from the same guy??

Almost tempted to go flat just to run some nice Shimano hydros rather than those BB7 roads... but then I couldn't race cx ;)
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