Thursday, February 5, 2009

Q&A: Frozen carbon seatpost, front derailleur trouble, new helmet?

Q: Hope you can help, Jim. The local bike shop cannot remove the Campagnolo carbon seatpost from my Litespeed. They have lubed it and heated the seat tube of the frame and still can't budge it. Any suggestions?


A: It'll sound a little strange, Ed, but you can try removing the crankset and bottom bracket from the frame. Then tip the bike upside down and pour some Coke (yes, the drink), down the seat tube of the frame with a funnel to get plenty in there. Now leave your bike upside down with the Coke in there and wait a few days and if you're really lucky, the Coke will penetrate and break the corrosion that has bonded the seatpost to your frame. You can tap on the frame and the seatpost with a rubber mallet (don't damage anything) to vibrate the parts and get the Coke to work its way in between. You can also try ammonia but Coke is safer to handle.

If that doesn't work, you could try freezing the seat tube of the frame with some dry ice, which might do it, too. And, I'm sure you already know that you can cut the post out, too, though that's a pain that takes a bit of work and time. You would cut off the top of the post and then either machine the seatpost out with a bit the same diameter as the post, or you would cut the post with a hacksaw that fits inside the post by making vertical cuts around it until you can break out slices of the post and eventually get the whole thing out. A lot of work, but doable. Wear a good face mask, though. You don't want to breathe carbon dust.

I'll keep my fingers crossed that the Coke trick works for you,

Q: Jim - When shifting from the big ring to the small ring on my triathlon bike (Felt B2) the chain will sometimes drop off the big chainring but not engage the small chainring. It will stay up against the side of the big ring and I can spin the cranks freely like I've shifted into neutral! The motor (me) is disengaged from the transmission and there is no power to the rear wheel. It's very frustrating and when it happens I've got to shift back to the big ring and try again (as I start uphill, or fall off my rollers!).

The front derailleur is a Shimano Dura-Ace, the chain is a Shimano Ultegra 10 speed and the crankset and rings are FSA SLK 53/39. The shifting is friction, not indexed. If an agressive shift is used to throw the chain over farther, faster, the chain may drop (off the inside ring). I've always heard that double front chainrings are simpler and more trouble free than triple, but I never had problems with my road bike (triple) like I've had with this. I've been told to ease up on the pedals to reduce chain tension, (but that's not always gonna happen) Can this be fixed?

Thanks in advance,

Front derailleur adjustment is tricky A: Thanks for writing, Aaron. It's essential to ease up on front shifts so that would be the first thing to try. You should always take all pressure off the pedals when shifting the front derailleur. Any other shifting technique is asking for trouble. The jumps between rings are just too big and the power you can put on the chain and rings is just too extreme. Keep in mind that when you push on the pedals the chain becomes a solid steel bar and it does NOT want to move sideways. It's only when you take all the pressure off that the chain gets flexible and has the sideways lateral play to shift smoothly from ring to ring. Experienced racers know this and even in the heat of a race, if they're smart, they will baby the front shifts to ensure no problems. Doing anything else is risking losing the race.

Having said all that, front derailleurs are among the most difficult parts to adjust on a bicycle and even pro mechanics have trouble with it. You might find that if you bring your bike to an expert mechanic they can solve the problem by fine-tuning the front derailleur (a common mistake is incorrect positioning on the frame - see diagram). Be sure to explain to them the problems you're having and also insist that they take a real test ride to experience the shifting on the road, not just on the repair stand. If they balk at this request, or seem disinterested, find a shop that really wants to figure out the problem and help you out. And, even if they're super nice and helpful, if they can't fix the problem, you should consider trying another mechanic to see if he/she has more experience with front derailleurs. (They seem simple, but they're anything but.)

One more thing to check is your cable. If it's sticky (like would happen if energy drink dripped on the frame and got on the cable or the cable guides), that will make the derailleur shift slowly or even not at all. Cleaning and lubing the cable is easy and might also solve the problem if you have a sticky cable. It could be worn or rusty, too. If so, replace it.

The whole thing could very well be your shifting technique, though, so you should try shifting with finesse and seeing if that solves the problem right away. It might. Good luck!


Q: Howdy Jim,
The foam pads on my Giro Transit II (mfg. date March 04) helmet have become so stinky that when sweat drips down over them onto my face, I can hardly stand it. I live in Santa Cruz, CA, not too far from Bell Sports, the company that makes Giro helmets, so I called them about replacement pads and they told me they are unavailable. Furthermore, they told me that the helmet should be replaced every 3 years anyway, because the material breaks down and is no longer safe. This is nuts! Is it not possible to design a good helmet that will last longer than 3 years? I'm sure thousands of years from now, Giro/Bell will be well-represented and studied by archaeologists digging through the mountainous middens of debris created by our throwaway culture. Any thoughts on the short life-cycle of the bicycle helmet?


A: Thanks for the great questions, David. Here's what I'd do: take your helmet on down to the great folks at the Spokesman in Santa Cruz and ask if by chance they can break out their replacement pads box and see if they have any old pads you can put in your helmet. That's what I did not too long ago on my 4-year-old Giro and they had just what I needed - the exactly right pads. I think the pads cost me about $5, a lot less than a helmet.

And, yes, the helmet companies say you have to replace the helmets for max safety, but most riders don't... especially with the escalating cost of the fancier helmets. Maybe in the worst accident you'd be at more risk, but I haven't seen any scientific proof of this. It sounds logical because the impact material in the helmets is polystyrene foam that protects less over time supposedly, but I don't really know if it's true. If you'd like to learn a lot more about helmets and possibly the facts on how long they will protect you you might visit the Bicycle Helmet Safety Institute a good online resource.

I think the Spokesman will be able to help you out.

8 comments: said...

awesome post. t'anks, jim.

Jim Langley said...

Hi Jim,

In response to David in Santa Cruz: I live in Phoenix, AZ. The foam pads in my helmet get quite sweaty after only 2 or 3 rides so I simply throw them in the washing machine with colored clothes. I've done this for years. They come out nice and fresh. One could put them in a small net bag and then in the washing machine, but I don't bother with the net bag.

Hope this helps.


Jim Langley said...

Jan wrote with a couple more great helmet pad and strap tips:

"Obviously, the pads don't need washing as often in the winter. They can also be washed by hand - be sure to rinse well. I also rinse the straps periodically since salt can weaken them over time."

Thanks a lot, Jan!

Anonymous said...

thanks for the comment about the front derailler....thankyou Ben - Perth West Aus

bikes for sale: said...

hi jim, very interested to hear the coke tip. would this work with a steel frame/alloy seatpost too? or another acid/solvent you could recommend for that? thanks.

Jim Langley said...

Yes, you could certainly try the Coke trick on a steel frame and aluminum seatpost. Those are much more common and I've heard of people having success w/Coke. But, I would first try Liquid Wrench penetrating liquid that's made for this purpose. First loosen the seatpost binder bolt completely and stand the bike up so gravity causes the Liquid Wrench to work its way down between the seatpost and frame. Then, after applying the LW, tap the seatpost with a hammer or block of wood to vibrate it (don't damage it). This will help the LW get all around and down between. You may need to do this for several days and wait for the LW to break the bond. Keep trying to twist the post by grabbing the seat and firmly trying to turn the post in the frame. Don't force it so hard you break the seat. Just keep trying and over time the LW will break the bond and you'll be able to turn and twist out the seat. If you have a bench- or floor-mounted vise, you can also invert the bike. If you remove the seat, and you have a quality seatpost you'll have a flat section to put between the vise jaws. Use wood or copper vise jaws so as not to damage your seatpost top. With the bike upside down, put this flat part of the post between the jaws and tighten the vise firmly. With the bike like this you can gently twist the bicycle left and right to put a tremendous amount of force on the post to break the bond. But, don't go crazy. You don't want to break the top of the post off. But, by applying LW and twisting like this, over time the post will come free. Another approach is to heat the post with a propane torch. Do this BEFORE applying LW or else you'll be breathing the fumes of the chemical and you don't want that. If you choose to heat it, heat the post not the frame or you'll burn off your paint. Also, don't get it too hot and don't burn yourself. There's also the dry ice approach which would be packing the post in dry ice to freeze it, shrink it and break the bond, but dry ice has its dangers too, more to you than your bike. In any case, one of these approaches will almost always work if you're patient. The LW one is the one that's easiset but it can take the longest. Hope this helps,

redvic said...

thanks, appreciate the tips. had never thought to tip the bike upside down and leave it that way for a while, while adding LW regularly.
the two times i've been unable to get a stuck seatpost out, i've (1) cut the seatpost and sawn it out with a hacksaw blade - very tedious. i had already tried the vise trick and broken the top off the 'post, and (2) cut the frame off with an angle grinder, as the 'post was worth more to me than the frame!

Jim Langley said...

To clarify, you would put the LW on the seatpost/frame when the bike is standing up and let it sit like that for awhile. Then you would invert and put it in the vise to try to twist it out after the LW had a chance to get down inside. When the bike is inverted, obviously, the LW won't run down inside... though you can remove the bottom bracket and put it in there that way if you want. One key thing to remember about bike repair is that they're not like most other things like cars. They're much, much lighter and more delicate because they have to be or else we'd be pedaling around on heavy awful-riding bikes. And, this means that when working on bikes you have to be gentle and patient. The parts will break super easily, the threads strip simply by using too long a wrench, the frame can be damaged just by leaning the bike against something too hard etc. So, when trying to troubleshoot something like a frozen seatpost, patience is your best ally. If you take your time and finesse things you can almost always fix them, but on a bicycle if you try to use brute force or hurry you will almost always ruin the part. But, I realize how frustrating it can be to have to spend 2 weeks to get something apart, which has happened to me before. It sure was satisfying when I saved that classic Campagnolo seatpost and was able to reuse it though. The customer was very happy.