By Jim Langley
A guy with a Sparrow frame came to me at my shop in Vermont around 1978. His exquisite steel hand-made American frameset was so nice I couldn’t believe it needed any work. But when he told me the seatpost had become part of the frame and no one could get it to budge, I knew I was in for a battle.
After trying all the “easy” remedies, I finally had to cut the top off the Campagnolo seatpost and, using a hacksaw blade holder and working inside the post — while carefully avoiding cutting the frame — saw lengthwise through the post. Then I knocked the pieces out with a punch. That was a delicate, scary and expensive repair, but all was well in the end.
Tip: This is obvious, but just in case, before you take any drastic measures to remove a “frozen” seatpost, double check that the seatpost binder bolt in the frame is completely loose.
The thing to understand is that it’s dissimilar metals that tend to have corrosion issues. So if you have a steel frame and seatpost, a little lube will usually keep corrosion at bay.
As soon as you put an aluminum post in that steel frame, though, you’ve got the potential of corrosion forming due to a reaction between the two metals. So, it’s even more important to lubricate the seatpost so that there’s a protective layer between the two metals.
As I mentioned last week, with carbon frames, there are issues, too. An aluminum seatpost can react to the carbon in some cases and corrode. The same thing can happen with a carbon seatpost in an aluminum frame. For aluminum posts in steel frames, greasing the frame/seatpost will do the trick.
Tip: It’s easier to put the gooey stuff inside the frame than to smear it on the post because inserting the post will scrape it off and spread it all over the place. When the grease is inside the frame that doesn’t happen.
You never want to use grease on a carbon seatpost or on an aluminum seatpost used in a carbon frame. Why? Because it can make the carbon too slick and prevent you from being able to tighten the seatpost securely. It won’t freeze but it will likely slip when you’re riding — and that’s an even worse problem.
The same is true of a carbon seatpost in a carbon frame. So, if it’s carbon on carbon, use what’s called “carbon assembly paste or compound” instead of grease. It looks like grease, but it has grainy particles in it that provide the grip to hold and stop the slippage.
Tip: The most common cause of frozen seatposts is forgetting that they need a little TLC every now and then. Partly, this is because nobody wants to change their seat height all the time. But, to protect your bike and prevent a frozen seatpost, you should pull the seat out of the frame at least yearly and make sure that the post/frame are lubricated. If you marked your post or have your seat height memorized, it makes the job easier.
So you went to raise your seat or to remove an old post and install a new model, and it won’t budge. Now, what do you do?
First, don’t panic and do anything rash. You might get lucky and be able to pull it out by resting one foot on a pedal, gripping the seat with both hands and forcefully rocking, pulling and slightly twisting to extract the post.
Tip: If your seatpost isn’t round (maybe you have an aero model), you can’t twist it much. Instead, you have to rock it. And, with a carbon post, it’s best not to twist it very much because any corrosion inside could score and damage the carbon.
When a post doesn’t move, don’t try to force it out with brute strength because you could break the top of the seatpost off, bend or break the rails on your expensive seat, or even possibly damage the frame.
Instead, what’s usually needed is patience and perseverance. Sometimes it takes a little time to get it to break free, but since the days of that Sparrow I talked about fixing, I’ve learned a few tricks you can try.
One of the best ways to free many frozen bicycle parts, including seatposts, is by heating them. This will make the part swell as it heats and shrink as it cools, which usually breaks the corrosion bond between the parts.
How you heat the post depends on what you’re working on and what you have on hand for tools. A propane torch can work for an aluminum seatpost. But you wouldn’t want to use it on a carbon one. If your carbon seatpost is frozen in a carbon frame, you’ll want to use a heat gun or a hairdryer. That’ll heat it up and should break it free.
Work carefully with heat, though. You don’t want the flame or hot air to burn any paint, decals, body parts, etc. And don’t touch anything you’ve heated. To protect things in the heat-affected zones, wrap a damp towel around them.
After heating and cooling, you can usually extract the post using the foot-on-the-pedal and pull/rock technique.
If you don’t like the idea of using heat or don’t have a propane torch or heat gun, use penetrating lubricants to break the corrosive bond between the post and frame. They take longer to work their magic than heat and they require careful handling, too. But they will usually work.
Liquid Wrench is one that’s been around forever and works well. You drip it on the crack where the seatpost enters the frame and tap on the seatpost with a rubber mallet or block of wood to vibrate it, which will help draw the penetrant between the parts. Sometimes you have to do this for a few days before it breaks the bond.
Something you might have around the house can work, too: ammonia. Use it just like the Liquid Wrench is used, but read the warning label and be careful.
Tip: If the penetrant doesn’t work and you decide to use heat, clean the seatpost and frame first to avoid breathing the burning chemicals.
Even whenusing heat or penetrants, it can take plenty of oomph to remove a frozen seatpost. A good way to get the leverage needed is to use a solidly attached bench vise. It can’t swivel or move, and the bench should be bolted to the wall so it can’t move either.
If you have a vise like this you can remove the seat from the seatpost, remove the clamp parts from the top of the seatpost, invert the bicycle (remove the wheels to make it easier), and clamp the top of the seatpost in the jaws of the vise (using copper/soft jaws to protect your seatpost). See the accompanying photo.
Tip: Some seatposts have tops that can be held nicely by the vise. If yours doesn’t, you may be able to fashion wood blocks to hold it firmly. In some situations, such as with an older post that’s badly corroded, you may want to simply clamp it in the vise however possible and risk ruining it since you need a new one anyway. But, always clamp it so as not to break it.
With the bike inverted in a vise as described, you can hold onto the frame with both hands and turn it to put pressure on the seatpost and break it free. But, do this after you’ve used either the heat or penetrant approach to break the corrosion.
You may have to heat or apply the liquid to the post several times before if finally breaks free, but it usually will. Also, you have tremendous leverage on the seatpost with the bike held like this. Don’t yank or jerk the frame because you can break the top of the post off. Instead, gently rock it left and right to try to persuade the post to turn in the frame. If you can get it to turn even a tiny bit, you can get it out. Good luck!
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s streak of consecutive cycling days has reached more than 8,000. Click to read Jim’s full bio.