Yeti ARC Seatpost Sizes

[kccourtney]

Hey there RB crew. Realized I originally posted this in the wrong thread so sticking it here.
I'm building an ARC and ARC-AS. Tried to put my 26.8 into the seat tube and won't fit. I measured and it looks like it's actually 26.6! Could that be right? I've never heard of that. I thought these only had 27.2 or 26.8 in the 90's. The 26.8 fits fine in the AS. Cheers.

 

[danson67]

They've always been 26.8 AFAIK.

Worth checking that the clamp bolt hasn't been done up too tight sometime and squashed the top of the seat tube.
If you look at the clamping slot, are the sides nicely parallel, or tapering in towards the top.
the 0.2mm difference in diameter should be visible as a 0.6mm difference in the slot width.

I've seen a couple of ARCs where a 26.4mm post has been used at some stage, and the top of the seat tube is distorted (or worse ).

All the best,

 

[kccourtney]

Cheers Dan. Seatpost actually goes in the first 3/4" or so but then just binds up. Without the clamp, the top of the seatpost measures about 26.6. Wierd. Maybe it was cracked and repaired improperly.

 

[elite504]

26.8 for sure.
Later new millennium were 27.2, but for what you're talking about 26.8.
Sounds like it needs a ream.

 

[Prodigal Son]

26.8 for sure.
Later new millennium were 27.2, but for what you're talking about 26.8.
Sounds like it needs a ream.

Yup. Ream the seat tube. Carefully.

 

[kccourtney]

Thanks guys. I'll see if I can find a local frame builder to have a crack at it.

 

[gtturbo]

If it's anything like my Ultimate then certain 26.8 seatposts fit such as Shimano or Tioga but my Syncros wont. I think it was @Once A Hero who had a similar experience.

 

[kccourtney]

Cheers. It's just a Ringle Moby which tons of people have on their Yetis so hopefully I can get r in there.

 

[Once A Hero]

Yes as @gtturbo alluded, I found that not all my 26.8 diameter posts would fit my Ultimate without binding up after partial insertion, and in fact the post needed to be a good bit under 26.8 rather than spot on - so it’s worth checking the post as well - especially as Mobys aren’t marked. Anything over 26.8 and it’s probably actually a ‘27.0’ post.

 

[Once A Hero]

https://www.retrobike.co.uk/threads/yeti-ultimate.420017/page-7A ‘26.8mm’ Shimano Deore DX post actually measuring 26.67mm was the best fit.