baron von greenback
Retro Guru
What is the smallest seatpost you would use with shims for instance 31.6 to 26 what is the max you would go cheers
Seatposts
- Thread starter baron von greenback
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25.4 or 25.0, in reality you would just use a 27.2mm, 30.9mm for ease of shim buying or whatever you have that looks nice. Though 31.6 is a standard side anyway.
baron von greenback
Retro Guru
That what I mean it looking wrong or something breaking just thinking about using what you already have before having to buy or wait for the right one and size to come along
bikeworkshop
Old School Grand Master
Use a long shim, preferably 100mm min.
The short shims break frames, especially if they have an elevated seattube.
USE plastic shims are forgiving.
You want a tight fit along the length
The short shims break frames, especially if they have an elevated seattube.
USE plastic shims are forgiving.
You want a tight fit along the length
Black_puma
GT Fan
I have only ever had one bike where I used a shim, which was my 1993 GT Zaskar. At the time I had a U.S.E green anodised seatpost (with matching handlebars) which was too small a diameter for the Zaskar so I got a shim to fit.
Since then I have learned that it isn't really worth wrecking your frame for the sake of fitting a fancy seatpost that is too small to fit correctly.
In my short time volunteering for Comac (from which I have now resigned for personal reasons) I have seen and worked on a number of bikes where the frame got wrecked due to an incorrectly fitted seatpost either with or without a shim.
This is sad as some of those frames were quite nice.
bikeworkshop
Old School Grand Master
The USE titanium posts came in 25.4 with shim supplied to take it to the right overall size.
Iirc the thinnest shims were aluminium.
The benefit is that the post can supply a little compliance.
Additionally, in my orange Vitamin T frame and most others, the internal seatpost surface is neither exactly 27.2 nor perfectly tubular, partly due to the welds in this area.
So additionally the plastic shim can distort a little, and I select the size 0.2mm too thick, and then sand it down to an extremely snug fit.
As a result, I'm more confident there aren't any point loads or stresses on the seat cluster and collar.
Many well used ti and aluminium frames (and plenty of steel) have expired due to stress failure in this area, even with the right size post.
Iirc the thinnest shims were aluminium.
The benefit is that the post can supply a little compliance.
Additionally, in my orange Vitamin T frame and most others, the internal seatpost surface is neither exactly 27.2 nor perfectly tubular, partly due to the welds in this area.
So additionally the plastic shim can distort a little, and I select the size 0.2mm too thick, and then sand it down to an extremely snug fit.
As a result, I'm more confident there aren't any point loads or stresses on the seat cluster and collar.
Many well used ti and aluminium frames (and plenty of steel) have expired due to stress failure in this area, even with the right size post.
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