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Cervélo aero post tuning

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Re: Cervélo aero post tuning

Postby Soloist Assassin » Sun Nov 13, 2011 2:56 pm

Bringing this thread back from the dead. Well, after the machinist guy took my broken carbon halfpipe, now he won't answer my calls, and I've never heard from him since. So the other day I felt like tuning the factory lower pig iron. I got 6g off of it. Not bad, but a custom made part wold of been better. I could also grind more aluminum away, but I was trying to be conservative. I basically cut the extensions off where it cradles the rail, and I ground it smooth. I also ground out the inside of the half pipe too.

before:
Image
after:
Image
this got the whole post with hardware down to:
Image
here is a close up of the new assembly. The original aluminum insert was starting to get worn. So I switched it out for the gold one shown, I harvested it from a broken KCNC seatpost collar. I had to drill the post out the next size bigger, but it works great, and I can now use the next size smaller bolt too. Went from a 5mm allen bolt to a 4mm.
Image
Everything all together, The saddle weighs 133g, even know it says 125g on it. Damn fibbing Italians. I still want to see if I can get a machinist to make me one, or if I pick up another pig iron, I might go a little more radical with this one. I am sure I can get it down sub 15g
Image
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Re: Cervélo aero post tuning

Postby pritchet74 » Sun Nov 13, 2011 4:10 pm

:party:

Nice job! Are those the KCNC yokes? Also, what bolts did you use to get the yokes to the seatpost head?

Parts list please. I want to do that to mine!
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Re: Cervélo aero post tuning

Postby Soloist Assassin » Sun Nov 13, 2011 5:16 pm

Nope they are just some yokes I got off ebay, but KCNC would work. The bolts I believe are m5 thread, and the rear one is countersunk with a 3mm head, and the front is m5 thread with a 4mm head. The yokes were 6g each, but I modded the front one. It has been ground down, and the threads have been drilled out so I could run the bolt through it it weighs in at 4g now. I've been kicking around the idea of a few lightening holes in the rear yoke to get it down to 4g as well. I can check on the bolt lengths. I would guess they are 15-20mm long.
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Re: Cervélo aero post tuning

Postby BMANX » Sun Nov 13, 2011 5:23 pm

Yes please keep us updated as it would be interesting to see this tuning.
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Re: Cervélo aero post tuning

Postby Soloist Assassin » Sun Nov 13, 2011 5:26 pm

BTW the oem Cervelo hardware is M6 thread, so these bolts are all basically down a size in diameter.
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Nov 13, 2011 5:31 pm

I've been running KCNC yokes successfully for the entire season.

BTW, I'd have thought it would be lighter to cut off the head of the front bolt instead of drilling out the yoke.
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Re: Cervélo aero post tuning

Postby Soloist Assassin » Sun Nov 13, 2011 5:43 pm

You can't because the front bolt threads into the gold KCNC nut thingy. It's gotta have a head to be able to tighten it.
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Nov 13, 2011 6:20 pm

You don't actually have to tighten the front one. Adjusting the saddle angle becomes trial and error, but hey, it's lighter.

Here's how I mount mine:

Screw headless bolt into kcnc thingy. You can do it by hand or make a slit for a screwdriver.

Mount front yoke from top. You can adjust the angle by half turns of the yoke.

Put in cradle.

Hook saddle under front yoke.

Mount and tighten rear yoke and bolt.
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Re: Cervélo aero post tuning

Postby Soloist Assassin » Sun Nov 13, 2011 6:27 pm

Yeah, you could definitely go that route too. I thought about that too, but it would have meant a considerably more inconvenient way to make adjustments. For the sake of ease of use, I'd rather keep it this way. You are definitely correct though. Your way will work fine, and save a gram or two.
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Nov 13, 2011 6:35 pm

Not sure if it would even save an entire gram. And if you're planing on dialing in your position, it will drive you nuts, as you have to remove the saddle every time.
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Re: Cervélo aero post tuning

Postby pritchet74 » Sun Nov 13, 2011 8:16 pm

OK, I am convinced that I want to do this for Victoria. Apparently my brain isn't working though because I am not seeing how you replace the front bolt that's part of the seatpost head. Andy - how did you do it? With the existing bolts being M6 and the yokes needing M5, how did you make that connection?

I just saw these on the FWB website though:
http://fairwheelbikes.com/parts-of-pass ... -3799.html

A pair of these is a simple swap for the upper cradle part and they come in either M5 or M6 versions. I have a ti bolt already for the rear bolt. So the front bolt on the existing Cervelo thead is just a headless bolt (just a threaded rod), right? Does is just un-screw from the head? I could take apart my seat / seatpost, but I am too lazy right now...
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Re: Cervélo aero post tuning

Postby Soloist Assassin » Sun Nov 13, 2011 8:47 pm

I had one of these, and it broke. I stole the gold insert nut thing from it, and then drilled out my post to the next size bigger to get it to fit.

Image

It uses m5, whereas the Cervelo factory part is m6. It also makes it look a bit trick, and is also .5g lighter too. . However, it only matches my Vuma Quad cups, and my cable ends, so I need more gold on my bike now. So I might be getting gold chainring bolts, jockey wheels, and who knows what else.
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Nov 13, 2011 8:48 pm

Hmm, my bolt fit right away. I guess Cervélo changed that at some point? Or I have a KCNC M6 yoke? I guess I could measure it, but the seat post is next door. You'll have to wait til the next commercial break.
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Re: Cervélo aero post tuning

Postby pritchet74 » Sun Nov 13, 2011 8:55 pm

My seatpost is definitely the newest model as it's uni-directional carbon. Bolt looks like M6 to me. I might need to order those POP yokes. Sounds like the easiest mod.
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Nov 13, 2011 8:55 pm

My Cervélo part is M5.
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