Seatpost shims on frames with tall seat masts?

[Fleming]

I am wanting to get a Rapide dropper for my Trek Roscoe 7 but need a 31.6mm post and they only offer a 30.9mm with a 100mm long shim.

 

Generaly I have no issues with seatpost shims however my bike has a relatively tall seat mast. The seat clamp is roughly 100mm above the top tube seat tube junction which makes me a bit worried however the min insertion mark on the seat post is quite a lot less than 100mm.

 

Below is a picture of the area. What is the general consensus on shims and frames similar to this.

[Grease_Monkey]

I don't know what the consensus is, but I would just use 2 shims - that way you get 200mm of shimmed post. Just cut the ridged area off (the part that keeps the shim from sliding into the frame. Just pop a layer or two of insulation tape right at the tip of the seatpost to avoid the bottom shim slipping off the post and into the frame.

[Fleming]

I don't know what the consensus is, but I would just use 2 shims - that way you get 200mm of shimmed post. Just cut the ridged area off (the part that keeps the shim from sliding into the frame. Just pop a layer or two of insulation tape right at the tip of the seatpost to avoid the bottom shim slipping off the post and into the frame.

That actually sounds like a bloody good idea.

 

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[PhilipV]

Maybe just get an appropriate sized seatpost from Lyne Components?

[Grease_Monkey]

Maybe just get an appropriate sized seatpost from Lyne Components?

Much easier solution. And Lyne make really good quality droppers, have one and I am very happy with it.

[Fleming]

Maybe just get an appropriate sized seatpost from Lyne Components?

Yeah that's obvious answer but I have Rapide bars and stem so would prefer a matching seatpost.

 

Its also a fair chunk of change cheaper on a 150mm travel option.

 

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[Bos]

Yeah that's obvious answer but I have Rapide bars and stem so would prefer a matching seatpost.

 

Its also a fair chunk of change cheaper on a 150mm travel option.

 

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Ahoy Stew, I've got a Rapide seatpost with shim as you're looking at getting on a carbon frame. Quite an extension on the post, and Its had me thinking as well. However so far so good. It did slip in the beginning but I got a allen key screw collar instead of a QR, which seemed to have made the difference. 

 

So on that Ali frame I doubt you'll have issues. 

[Captain Fastbastard Mayhem]

Yeah that's obvious answer but I have Rapide bars and stem so would prefer a matching seatpost.

 

Its also a fair chunk of change cheaper on a 150mm travel option.

 

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Lyne post is user serviceable, and has mucho replacement parts. Rapide is like the giant... not very serviceable. 

 

I'd go Lyne, honestly. If you're worried about the branding, there's an easy solution to that. 

[Jewbacca]

Buy some tipex and a permanent marker.

 

Colour over the Lyne with the marker, then write Rapide in tipex.... It's a pleasure

[Fleming]

Ahoy Stew, I've got a Rapide seatpost with shim as you're looking at getting on a carbon frame. Quite an extension on the post, and Its had me thinking as well. However so far so good. It did slip in the beginning but I got a allen key screw collar instead of a QR, which seemed to have made the difference.

 

So on that Ali frame I doubt you'll have issues.

Thanks bos. I am not worried about it slipping down. My main concern is with only 100mm of contact between the inside of the seat tube and the shim and the seat tube extending 100mm above the top tube there would be a lot of leverage applied to the top tube / seat tube junction.

 

The idea of 2 shims seems good though as it would allow much greater contact length.