I think I understand your situation. I'm also partial to the front hole, but I would like to keep access to the rear hole just in case. Although I have never experienced a bunch of "material" around the rear hole?? Maybe you should try to clean it out. I don't think it's supposed to be there.

Well if I do go this route, I will most likely buy a second post and by material I mean the actual post material that makes up the second hole.

Once I have the bike partially back together I will show you want I mean.

Yup, I think you are doing the right thing. Two posts sounds like a reasonable solution. One for each hole. That should keep everything nice and tidy.

To be honest I just want a back up in case I really screw up the first post.

As for the second post, I will just use some carbon sheets that I have to create a nice plug for the back hole so you will not even see it.

Ahh, a plug for the back hole. I never even thought of that.

Cervelo doesn't supply a plug for the hole anymore?

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Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca

Yes they do but I have a sheet of carbon and can make my own discs that will fit amazingly well.

I opened the slot up on the bottle holder with a file. Seemed cheaper and easier than messing with the seat post. I have my saddle pretty far forward (2/3's)and level. do you have enough room to do that?

Don't rule out the rear hole. I know it's not supposed to be in there, but if you keep it clean and free of material, it can still be quite functional. Though I usually only use the rear hole about once a month. Rest of the time it's the front hole for me!

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_____________________________________________________
"Oh man, it's going to take days to kill all these people!" - Jens Voigt

I don't see why it matters. As Vanilla Ice said, a hole is a hole.

Ok. I got that out of my system. PM me. I have an extra seatpost I am not using. If you are interested I would give you a deal for your project.

After looking at the seat interface with the post I am sure that I can just round the back like the front and it would work but just.

That being said, I am a weight weenie at heart and if I can lower the weight anywhere I will.

Just my overly-cautious $.02, I'd be worried about changing the load path within the carbon.

It's $$$ but you could get a saddle/seat post combo from Dash Cycles to satisfy your needs :D

I am 100% sure that the top of the post is not carbon. I am sure that it is aluminum covered with carbon.

I was able to get a post on Ebay for $25 so I am going to modify that one just to see if I can match the back front to the front. The front is nice and rounded around the hole while the back comes to a more pointy end.

I will take it to work and round it on the belt sander or disc sander. Then touch it up with some black paint on the exposed aluminum that I assume is inside the top of the post. From looking at the big holes and the small holes for mounted the drinking systems off the back, the holes clearly have aluminum inside so I am assuming that the whole top of the post is aluminum covered with carbon.

At that point if it all works with the Sitero, I will most likely just leave it at that but make some carbon covers for the back hole and glue them in place. I will lose the ability to use some aftermarket options since I will be getting ride of one of the small mounting holes but that is alright since I believe the Sitero BTS mounting option is more aero than what I could get otherwise.

LOL. It seems that the front hole is less fragile too, using the rear hole too much can definitely cause problems, certainly on longer rides.

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__________________________________________________
If it's hit, it's history.
If it's missed, it's mistery.

Hi BMANX,

Yep, there is an aluminum plate inside the whole top. In the right light you can often see the outline inside the carbon.

You should know that temperatures over ~200F will damage most epoxies. I'd guess a belt sander, if used aggressively, would easily get too hot. A band saw (with a new-ish blade) might keep the temperature low enough, and a light touch up on the belt sander (again, with a new-ish belt) could be okay.

We've not tested a post modifed as you're planning to do, so I'm not endorsing it. Just providing some facts that might be important when working with cured carbon/epoxy in general.

Cheers,

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Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Thank you Damon. My thoughts were to trace out what I wanted to do and then cut as much as possible away then just touch it with the sander to finish the shaping. So most of the material will be cut away and I could most likely do it by hand and then just finish it carefully by hand. I know that I just have to knock off the back end of the post to match the front to endure that it works.

So I got my used seat post that I paid $25 for today in the mail. Right home and plotted out my course of action. With the dremel cutting disc on a slow speed, I started to cut away the material at the top back corner to match the profile of the front top corner.

I did not realize how much carbon was around the aluminum so I was glad that I was wearing a mask and eye protection. After I cut away the bulk of the material I used a dremel sanding drum on low speed but that was not getting the effect I wanted so I went with the good old sandpaper and file and managed to get the shape that I wanted.

I took my time cutting the bulk of the material away as to not get it very hot. It was warm to the touch but not hot. I think it was a good idea to do the shaping with a file and sandpaper. I had some plasti dip kicking around in the garage so I masked off the exposed area and painted it which is drying right now.

All in all if I did not have a $25 seat post from Ebay, I would never have done this and I still have the original post ready to go if there are any issues. Now I just have to make some carbon disc to fill in the back hole and all should be good and aero.

The modification allows me to have the Sitero with the bottle holder attachment as far forward on the post as possible so I should be able to get a fairly steep STA on this set up.

I thought you've learned this by now, pictures!

IT WAS DRYING! Wow you guys are tough.

Not too shabby.

But next time put your chain in the big ring. ;)

That would be hard since the cranks, chain, pedals, FD, RD, brakes, shifter, brake levers and cassette are not even on the bike.

Well geez there's your first problem.

I too am at the building a (budget) bike phase. I'm farther along than you, but I'm sure it'll be good. What type of components if you don't mind me asking?

Build will be as follows.
54cm Cervelo P2 with modified behind the stem shifter cable entry. That was the other item I was modifying today.
Cervelo Modified seat post with clamps for carbon rails.
TriRig Omega Front brake with EE rear brake.
TriRig Sigma Stem.
TriRig Alpha Bars.
Sram TT 500 shifters and levers.
Sram Force RD
Shimano Dura Ace FD
Carbon railed Sitero
FSA carbon cranks with Fibre-Lyte full aero carbon compact rings
Speedplay X2 with Ti spindles, aluminum butterflies and ti bolts
ENVE 45 carbon clinchers with Conti 4000s 23mm tires and Latex tubes.
Sram 1090 11/25 cassette
KMC X10SL gold chain
KCNC skewers.

I think that is it. Not sure if I will even run bar tape on this set up.