I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here? Shim the post? Shim the inside of the seat tube? What material should I use for a shim and how can I keep it in place?
Or is a sturdier clamping collar a better choice? I'm worried about over-clamping on the carbon.
I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here? Shim the post? Shim the inside of the seat tube? What material should I use for a shim and how can I keep it in place?
Or is a sturdier clamping collar a better choice? I'm worried about over-clamping on the carbon.
The first thing to do is see what the actual dimensions of the post and the seat tube opening are - ie, unless you have calipers, take it to a shape so they can measure the post and the opening (or use sizing rods on the opening.)
I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here? Shim the post? Shim the inside of the seat tube? What material should I use for a shim and how can I keep it in place?
Or is a sturdier clamping collar a better choice? I'm worried about over-clamping on the carbon.
I used to have a sliping seatpost problem once, could never get it to hold, till I read somewhere to apply a bit of grease to the post; I was doubtful, because I thought it would just make the problem worse, but I tried it and it worked ! Your current collar might be designed to apply the required torque for your post, and no more. You have nothing to lose by just trying a bit of grease as I did.
I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here? Shim the post? Shim the inside of the seat tube? What material should I use for a shim and how can I keep it in place?
Or is a sturdier clamping collar a better choice? I'm worried about over-clamping on the carbon.
I used to have a sliping seatpost problem once, could never get it to hold, till I read somewhere to apply a bit of grease to the post; I was doubtful, because I thought it would just make the problem worse, but I tried it and it worked ! Your current collar might be designed to apply the required torque for your post, and no more. You have nothing to lose by just trying a bit of grease as I did.
I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here? Shim the post? Shim the inside of the seat tube? What material should I use for a shim and how can I keep it in place?
Or is a sturdier clamping collar a better choice? I'm worried about over-clamping on the carbon.
New carbon frameand seatpost?? Two things are 'wrong' first, the seatpost 'may' be undersized, not unusual, measure it and warranty if too small. Second the frame might be oversized...again, not unheard of...warranty issue if it is.
I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here? Shim the post? Shim the inside of the seat tube? What material should I use for a shim and how can I keep it in place?
Or is a sturdier clamping collar a better choice? I'm worried about over-clamping on the carbon.
I used to have a sliping seatpost problem once, could never get it to hold, till I read somewhere to apply a bit of grease to the post; I was doubtful, because I thought it would just make the problem worse, but I tried it and it worked ! Your current collar might be designed to apply the required torque for your post, and no more. You have nothing to lose by just trying a bit of grease as I did.
Isn't there a rule about NOT greasing carbon?
Ron
The rule we follow is no grease only on carbon-carbon-mixed materials, yes use grease or it will get stuck eventually-Recently saw ruined Giant and Trek with stuck aluminum posts...
According to Craig Calfee, there's nothing destructive about grease and carbon fiber contacting each other. The grease won't attack the resin.
There's a possibility that aluminum will corrode when in contact with carbon fiber; the two materials have different galvanic potentials and the aluminum can corrode and possibly freeze the seatpost in place. So there's some rationale for greasing an aluminum seatpost going into a carbon fiber frame. With a carbon seatpost the grease is optional; use it if it's a tight fit.
I've got a carbon seatpost on the way, but I'm using aluminum now.
The first thing to do is see what the actual dimensions of the post and the seat tube opening are - ie, unless you have calipers, take it to a shape so they can measure the post and the opening (or use sizing rods on the opening.)
With my brand new nifty digital calipers (never pass up an excuse to buy tools) the frame measures as 27.25mm with no torque on the binder, seatpost #1 (Salsa) as 27.15mm, and no-name post #2 as 27.17mm.
The solution was a sturdier seat post binder, in this case a Salsa Lip-Lock, http://www.salsacycles.com/comps_skewers.html. It's a better design than the old one, though a few grams heavier.
New carbon fiber seat post as well. No grease on the pin.
That style is much better since it doesn't bend the bolt.
I stuck some strips of teflon plumbing tape down the seat tube of my bike recently... leaving the ends draped over the top. Hold onto the ends as you stick the post in, and snip off the excess. I was trying to solve a creaking problem (didn't work) but it should work well for snugging up a loose post or making sure it doesn't get corroded in place.
The solution was a sturdier seat post binder, in this case a Salsa Lip-Lock, http://www.salsacycles.com/comps_skewers.html. It's a better design than the old one, though a few grams heavier.
New carbon fiber seat post as well. No grease on the pin.
A suggestion, turn the clamp around so that the split in the frame is opposite the split in the clamp-keeps the 'hole' rounder to prevent crushing of the seat pin...
I've got a new carbon frame. Obstensibly the seat post diameter is 27.2, but the carbon at the clamp area is pretty thick, and the clamping collar is aluminum and fairly flimsy. I can't get enough clamping force to keep the seat post in place. When there's no clamping force at all the seat post slides very easily up and down. I don't have any grease on the post.
I'm thinking I may have to shim something to get it to stay in place. What are my options here?
You are lucky, indeed. Get yourself a little bit of mylar film of suitable thickness; cut out a piece in the shape of a trapezoid to be inserted, inverted, between the post and the frame tube. You will force it in just as far as need (to be trimmed off later). That shim will improve the fit and prevent any corrosion due to interface contact.
