27.2mm seat post in a 27mm frame
- Thread starter Adam_S
- Start date
Adam_S":3nvxv8f6 said:
As far as you can discover???? Maybe if you can get an accurate measurment then you may find it is 27.2mm But as far as forcing in a larger seatpost into a smaller diameter frame i wouldnt!!! you may trash both seatpost and frame!!!!
The hoop stresses will be massive, you'll either split the frame, crush the seatpost, or if the tolerances fall *just* right. You'll end up with a seatpost that is permanently fixed in place as the fit is so tight.
I mean, you wouldn't try and run a 1/4" thread into an M6 hole, they are almost the same size........
I mean, you wouldn't try and run a 1/4" thread into an M6 hole, they are almost the same size........
Try the post. Don't force it in. The post may be at the extreme small end of its tolerance. If the post slides in with a little grease then use it.
I've come across (and owned) a couple of Konas which took a post 0.2mm bigger than the usual dimension listed. It happens when you get a frame with no distortion from welding.
I've come across (and owned) a couple of Konas which took a post 0.2mm bigger than the usual dimension listed. It happens when you get a frame with no distortion from welding.
It's an interesting debate that, greasing carbon especially as they seem to have an equal ability to get stuck. I used the guidelines here:
http://velonews.competitor.com/2005/10/ ... arbon_9023
Thankfully! An opportunity to dispel the myth that one shouldn’t greasea carbon post!I don’t know where the myth started, but carbon composites are not affectedby grease. Our advice is simple: If the seatpost fits tight,grease it. If it slips, de-grease it. As has been known formany years, when aluminum and carbon fiber contact each other, galvaniccorrosion can start. That is why Calfee uses a fiberglass sleeveas a seat tube shim. Aluminum seat tube (or sleeve) and a carbonpost will result in corrosion of the frame and possible seizure of thepost within the frame. A carbon sleeve on an aluminum post will resultin corrosion of the post. Salty environments accelerate this corrosion.Anodizing merely slows it down. About the only common chemical thatwill hurt carbon fiber is paint remover (which attacks the resin betweenthe fibers). But there are many solvents that will dull a nice paintjob.
Craig Calfee
http://velonews.competitor.com/2005/10/ ... arbon_9023
Thankfully! An opportunity to dispel the myth that one shouldn’t greasea carbon post!I don’t know where the myth started, but carbon composites are not affectedby grease. Our advice is simple: If the seatpost fits tight,grease it. If it slips, de-grease it. As has been known formany years, when aluminum and carbon fiber contact each other, galvaniccorrosion can start. That is why Calfee uses a fiberglass sleeveas a seat tube shim. Aluminum seat tube (or sleeve) and a carbonpost will result in corrosion of the frame and possible seizure of thepost within the frame. A carbon sleeve on an aluminum post will resultin corrosion of the post. Salty environments accelerate this corrosion.Anodizing merely slows it down. About the only common chemical thatwill hurt carbon fiber is paint remover (which attacks the resin betweenthe fibers). But there are many solvents that will dull a nice paintjob.
Craig Calfee
It's an interesting and ongoing debate, especially when you see "About the only common chemical that will hurt carbon fiber is paint remover" from the "carbon guru".
Hmmmmm. A) what about the clearcoat (thousands of different types, all of which have wide ranges of application methods that will work, but give differing properties), B) what about the resin (as opposed to the fibre) same story as the clearcoat, does Calfee know about ALL of them (No) C) Depending where you live you can get far far more aggressive chemicals than paint remover. I've got some stuff that i bought over the net that will dissolve certain grades of resin. Unfortunately i found out the hard way. (toy car parts, not bike parts)
Hmmmmm. A) what about the clearcoat (thousands of different types, all of which have wide ranges of application methods that will work, but give differing properties), B) what about the resin (as opposed to the fibre) same story as the clearcoat, does Calfee know about ALL of them (No) C) Depending where you live you can get far far more aggressive chemicals than paint remover. I've got some stuff that i bought over the net that will dissolve certain grades of resin. Unfortunately i found out the hard way. (toy car parts, not bike parts)
I don't know of any greases that destroy structural epoxies though, which is what is used in carbon seatposts.
I agree that a cheap post (especially a counterfeit) is likely to be made with polyester resin (still OK for grease, after all they make fuel tanks out of it) but the varnish could be anyone's guess.
I agree that a cheap post (especially a counterfeit) is likely to be made with polyester resin (still OK for grease, after all they make fuel tanks out of it) but the varnish could be anyone's guess.
