Cyclocross newbie looking to build light CX bikes

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LouisN
Posts: 3512
Joined: Mon Feb 19, 2007 3:44 am
Location: Canada

by LouisN

HI all,

I introduced my daughters to CX this fall. They loved it :D !!
Started by mixing up bike parts with their grand parents's hybrid frames, and eventually found some cheap CX frames (boat anchors !! 1850g frames and 850g forks for size 50cm) to end the season .

Now I'd like to find budget friendly solutions to build 2 lightest possible CX bikes for CX racing.

Here are my thoughts:
1) Find and buy two Open mold generic CX frames with 130 mm rear spacing (canti brakes).
2) build them with 1 X 10 Sram with X7 clutch rear der (XT or the like 11-34 cassette and 38T narrow wide front chainring on whatever 110mm light crankset I find.I have lots of SRam 10S parts.
3) Use my low profile alloy road tubular wheels an glue CX tubs on them.I have tons of Shimano/Sram 10S, 130mm rear wheels.

What do you think ?

Louis :)

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FIJIGabe
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Location: The Lone Star State

by FIJIGabe

Do they have to match, and how long are you willing to wait? We're getting near the end of CX season in a lot of places, which means that parts should start coming off and eBay sales will start soon.

Personally, I'd look for some aluminum canti frames, and build them up along the lines of what you're thinking. I know if my wife decided to get into it, that's what I'd probably do (personally, I'd look for a 50cm Trek Crockett).

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LouisN
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by LouisN

The project is for september 2016, so yes, I'm patient. They don't have to match, they're road and MTB bike don't either...
Here the season ended last weekend, and it's already pouring CX bikes and bike parts on FB groups and local ads, etc...
I already purchased a few bits I needed :D

So yes, I'll keep an eye on the missing bike stuff I need.
Was looking at older CAAD X frames too, though the real weights are high...
I know the Trek Crockett is supposed to be around 1250g (size 56), with an Under 400g fork, but I'm sceptic...

Louis :)

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FIJIGabe
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by FIJIGabe

Remember that there's the original Crockett disc with the QR fork, and now a "2nd" gen disc version with the TA fork. Every version of the new bikes, other than the Crockett 5 has the full carbon fork. Also weights are subject to brake type, obviously, since disc brakes are heavier than canti's.

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LouisN
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by LouisN

Thanks, I'll have a deeper look at what's available.
Definitely looking for a QR frameset (for wheelset compatibility), and full carbon fork prefferably.

Louis :)

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the_marsbar
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by the_marsbar

Disc brakes are the way to go, if the bikes should last a while. You also won't wear down the rims as fast... The Reflex rims on my previous bikes had to be replaced after two seasons.

grover
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Joined: Mon Jul 26, 2004 1:06 pm

by grover

You're spot on with your aim. I became a weight weenie trying to get my own bikes light for racing. Those days are gone and I'm much more of a reliability then weight guy now. Therefore I love project bikes for kids (or my 50kg 150cm partner when she got into cycling). I'm still a weight weenie at heart and these light and little people NEED a light bike to enjoy it when starting out to ensure they get the bug (and I get my hit of weight weenieism). Plus they tend not to break stuff.

I know the Crockett is closer to 1600grams in a 56 for the frame. I 100% support the open mould asian carbon frame. You should easily be able to save 500grams on the frame alone versus any aluminium frame at the price point. As an aside, they're fairly worthless second hand so go to town. Let your daughters have a crafternoon with some glitterpaints/paint pens etc and put a personal touch on it. Then just spray a clear coat over it.

Canti vs disc. Personally, discs are the business. I'd never ride cantis again. However, at a risk of stereotyping, I'm thinking your riders are light and won't be riding super fast. They're also going to outgrow the bike. Cantis will again make for a lighter bike and save you a heap of money as the brakes themselves can be found cheaply and you already have wheels. It's easy to find cheap light road wheels if you need more. Cheap light disc brake wheels are practically non existent.

Also 100% support 1x10 sram with an x.7 clutch derailleur. Saves a heap of weight and left levers with broken shift internals are really cheap on ebay. The sram leavers are great for small hands, very easily adjustable. The fixed brake lever (versus shimano) is more solid for braking for those starting out and the double tap shift mechanism is very intuitive for anyone I've given it too starting out.

I'd have a rethink on the gearing. The mtb derailleurs work best with a 32 or 36 biggest cog on the cassette. That's great for getting some easy gears. However I found even a 38 tooth single may be too big. Really take note of what gearing they use most now when you go for a ride. I found a 34 single chainring was better and probably would have gone 32 if the crankset would accept it. Make sure you've given them easy enough gears and allow them to ride up things comfortably. Not much is scarier than being overgeared and stalling up a steep incline on a cx bike. By the time they've spun out a 34-11 they'll be going plenty fast. Think about length too, I had my eye on ebay for a while to score a cheap, light, compact, 165mm length crankset.

Good luck, sounds like a fun project. Sub 8kg definitely doable. Sub 7kg if you find a few weight weenie bargains.

Marin
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by Marin

Get Mini V brakes, they actually work, as opposed to cantis.

Your plan sounds great, go Asian open mould for frames, and I think Grover has a point re gearing. Theoretically, I could ride most road rides in the 34t chainring...

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LouisN
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Joined: Mon Feb 19, 2007 3:44 am
Location: Canada

by LouisN

@grover, lots of good comments, thanks.
For cranksets I was also thinking about a 104mm 4 bolts crank, to be able to put a smaller than 38T chainring in the front, maybe a 32 or 34.
Wondering if a MTB crank designed for 73mm BB shells is fine (with a few 2.5 mm spacers) on a Cyclocross frame.

Louis :)

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Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

MTB cranks have a really wide Q-factor.

You can go down to a 33 on a 110 BCD road compact.

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