Anyone know of a Shim/adapter to fit a round post in D shape?

Discuss light weight issues concerning road bikes & parts.
Mikedb
Posts: 19
Joined: Tue Apr 30, 2019 6:46 am

by Mikedb

Not sure if this is even possible, but I would like to use my kinekt bodyfloat seatpost in a new Roubaix.

Bodyfloat is a round 27.2 standard seatpost, while the new Roubaix used a d-shaped seatpost design.

Are there any Shim/adapters or any other methods out there I could use to make it work?

Thx in advance.

by Weenie


jfranci3
Posts: 706
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

The answer is going to be no. I don't see a way of clamping the post.

You should wait for pinarello suspension bike, put a 50psi 32c tire on the back of the roubaix, or wait for the front suspension dohickie makes its way into the Diverge. Have you tried the damperless Specialized shock? It's not bad.

AJS914
Posts: 3488
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

The new Roubaix has compliance designed in to the stock seatpost.

Mikedb
Posts: 19
Joined: Tue Apr 30, 2019 6:46 am

by Mikedb

jfranci3 wrote:
Wed May 01, 2019 4:33 pm
The answer is going to be no. I don't see a way of clamping the post.

You should wait for pinarello suspension bike, put a 50psi 32c tire on the back of the roubaix, or wait for the front suspension dohickie makes its way into the Diverge. Have you tried the damperless Specialized shock? It's not bad.
I kind of figured that.

I searched everywhere, with no luck, so I thought as one last effort, I would ask here.

joejack951
Posts: 631
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE

by joejack951

If you really wanted to make it work...

Machined a D-shaped 'shim' with a 27.2mm dia. blind hole in it, as deep as necessary to get the required seatpost extension with the shim all or mostly in the frame. Bond your seatpost into this 'shim' then clamp the shim in the frame. Probably heavy, and wouldn't be too cheap either for a one-off, but it should work.

mattr
Posts: 4673
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Or 3D print it.
Can do a few versions to see what works.

joejack951
Posts: 631
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE

by joejack951

mattr wrote:
Wed May 01, 2019 6:59 pm
Or 3D print it.
Can do a few versions to see what works.
For fitment purposes, sure. For the 'real' version, I'd be concerned with creep of the plastic over time with the constant stress of the clamp being applied, especially a non-completely dense 3D print (FDM). SLS (especially the carbon filled type) might work but wouldn't be cheap. SLA or other epoxy-type process...eh, I wouldn't bother. Machined using Delrin/Acetal or glass filled nylon may work, but you are likely spending just as much as you would for aluminum at that point.

mattr
Posts: 4673
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Oh, yeah, i'd finish up with something a bit more solid, i'd not be trusting a "Normal" 3D printed part long term, even at 100% fill.

And TBH, some of the hobbyist printing is getting *really* good. Theres a guy in one of the groups i'm in who has just spent ten thousand euros on a printer for his hobby room.

And then started modding it to do higher strength and higher precision parts........

Working in ABS, PLA, PETG, Poly Carb and Nylon. If you can get a decent design, he'll print it for you for at a very reasonable rate.
Just need to find your local hobby group!

Mikedb
Posts: 19
Joined: Tue Apr 30, 2019 6:46 am

by Mikedb

joejack951 wrote:
Wed May 01, 2019 6:41 pm
If you really wanted to make it work...

Machined a D-shaped 'shim' with a 27.2mm dia. blind hole in it, as deep as necessary to get the required seatpost extension with the shim all or mostly in the frame. Bond your seatpost into this 'shim' then clamp the shim in the frame. Probably heavy, and wouldn't be too cheap either for a one-off, but it should work.
Outside of weight (which I'm not concered about) any other cons to a setup like this?

Also, who would you recommend me going to in order to get something like this done?

Mikedb
Posts: 19
Joined: Tue Apr 30, 2019 6:46 am

by Mikedb

mattr wrote:
Wed May 01, 2019 9:13 pm
Oh, yeah, i'd finish up with something a bit more solid, i'd not be trusting a "Normal" 3D printed part long term, even at 100% fill.

And TBH, some of the hobbyist printing is getting *really* good. Theres a guy in one of the groups i'm in who has just spent ten thousand euros on a printer for his hobby room.

And then started modding it to do higher strength and higher precision parts........

Working in ABS, PLA, PETG, Poly Carb and Nylon. If you can get a decent design, he'll print it for you for at a very reasonable rate.
Just need to find your local hobby group!
What material would you recommend? Carbon seatpost going into a carbon frame.

AJS914
Posts: 3488
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Why do you want to reengineer a bike that was already designed for compliance? I recommend listening to the Cyclingtips podcast about the Roubaix with the Specialized engineers. They specifically ruled out seatpost suspension and designed the compliance into the stock seatpost and the lower seatpost mounting. If the stock bike is not compliant enough or if sizing up the tires won't do it for you then you are buying the wrong bike.


https://bikerumor.com/2019/04/10/2019-s ... shock-2-0/
While the new Future Shock 2.0 offers smoother, more controlled movement up front, a simplified Pavé post matches comfort at the back. With most of the weight on the rear, Specialized developed a new aero seapost design meant to flex more to better match the feel of the front end. That elongated D-shaped post claims to be the first truly compliance-oriented aerodynamic seatpost on the market. The Pavé post is held in place with a dropped seat clamp design, now accessed from the top, with clamping happing around the end of the seatstays.

This continues the idea of allowing a longer lever arm for more flex, with the post arcing front to back within its toptube opening, sealed shut with a flexible rubber cap. It is also the same shape that from the Tarmac, suggesting that bike will get some more comfort as well.

Mikedb
Posts: 19
Joined: Tue Apr 30, 2019 6:46 am

by Mikedb

AJS914 wrote:
Wed May 01, 2019 10:28 pm
Why do you want to reengineer a bike that was already designed for compliance? I recommend listening to the Cyclingtips podcast about the Roubaix with the Specialized engineers. They specifically ruled out seatpost suspension and designed the compliance into the stock seatpost and the lower seatpost mounting. If the stock bike is not compliant enough or if sizing up the tires won't do it for you then you are buying the wrong bike.


https://bikerumor.com/2019/04/10/2019-s ... shock-2-0/
While the new Future Shock 2.0 offers smoother, more controlled movement up front, a simplified Pavé post matches comfort at the back. With most of the weight on the rear, Specialized developed a new aero seapost design meant to flex more to better match the feel of the front end. That elongated D-shaped post claims to be the first truly compliance-oriented aerodynamic seatpost on the market. The Pavé post is held in place with a dropped seat clamp design, now accessed from the top, with clamping happing around the end of the seatstays.

This continues the idea of allowing a longer lever arm for more flex, with the post arcing front to back within its toptube opening, sealed shut with a flexible rubber cap. It is also the same shape that from the Tarmac, suggesting that bike will get some more comfort as well.

To answer your question....

After testing the Kinekt bodyfloat, I really fell in love with the product and wanted to use it on a Roubaix (I really like the Future shock as well).

I've also rode both the new and old Roubaix. The bodyfloat blows both out of the water when it comes to rear compliance.

IMHO, Kinekt at the rear and future shock at the front would be the perfect setup as I plan on using this is a commuter/daily bike.

New Roubaix would be the choice (Future shock feels smoother) but I would giveup the option of using the Kinekt.

I got a good deal on the old Roubaix and it's possible to get both the 2019 and 2020 Roubaix, but I would rather pic one and use the money on a Venge in a few months.

joejack951
Posts: 631
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE

by joejack951

mattr wrote:
Wed May 01, 2019 9:13 pm
Oh, yeah, i'd finish up with something a bit more solid, i'd not be trusting a "Normal" 3D printed part long term, even at 100% fill.

And TBH, some of the hobbyist printing is getting *really* good. Theres a guy in one of the groups i'm in who has just spent ten thousand euros on a printer for his hobby room.

And then started modding it to do higher strength and higher precision parts........

Working in ABS, PLA, PETG, Poly Carb and Nylon. If you can get a decent design, he'll print it for you for at a very reasonable rate.
Just need to find your local hobby group!
I agree that 3D printing has gotten really good. I've been using it for nearly 20 years now and what comes out of a $10k printer these days matches/exceeds what used to need a $150k printer. And the really good printers (HP Multijet Fusion for one) can make amazing parts that are economical to boot.

Any unfilled plastic is going to creep over time when subjected to a constant clamping force. Delrin/acetal is one of the few that doesn't do it terribly even in the unfilled state but I would only even attempt to use a part machined from a block of it, even if it could be printed (I don't think anyone is at the moment). Aluminum is the best option here, ideally anodized to prevent corrosion between it and the frame and/or seatpost.

joejack951
Posts: 631
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE

by joejack951

Mikedb wrote:
Wed May 01, 2019 9:27 pm
joejack951 wrote:
Wed May 01, 2019 6:41 pm
If you really wanted to make it work...

Machined a D-shaped 'shim' with a 27.2mm dia. blind hole in it, as deep as necessary to get the required seatpost extension with the shim all or mostly in the frame. Bond your seatpost into this 'shim' then clamp the shim in the frame. Probably heavy, and wouldn't be too cheap either for a one-off, but it should work.
Outside of weight (which I'm not concered about) any other cons to a setup like this?

Also, who would you recommend me going to in order to get something like this done?
PM me. I can possibly help.

Mikedb
Posts: 19
Joined: Tue Apr 30, 2019 6:46 am

by Mikedb

joejack951 wrote:
Fri May 03, 2019 1:40 pm
Mikedb wrote:
Wed May 01, 2019 9:27 pm
joejack951 wrote:
Wed May 01, 2019 6:41 pm
If you really wanted to make it work...

Machined a D-shaped 'shim' with a 27.2mm dia. blind hole in it, as deep as necessary to get the required seatpost extension with the shim all or mostly in the frame. Bond your seatpost into this 'shim' then clamp the shim in the frame. Probably heavy, and wouldn't be too cheap either for a one-off, but it should work.
Outside of weight (which I'm not concered about) any other cons to a setup like this?

Also, who would you recommend me going to in order to get something like this done?
PM me. I can possibly help.
Since I'm new to this site, it won't allow me to PM anyone.

Can you shoot me an email at:

MikeDB1984@gmail.com

by Weenie


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