front derailleur seized

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Number_35

Number_35

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Jul 7, 2014
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Winnipeg MB CA
So, I put the fat bike away last April after washing the winter muck off, and it sat for a few months until I got it out about just over a week ago. To my dismay, the front derailleur (Shimano SLX) was frozen in place - that is, likely rusted. When I try to shift down to the lower chain ring, the derailleur stays in place. I'm afraid the pivot points are rusted. Dumb, and completely preventable - I should have lubed it before putting the bike away. Anyway, I started out by spraying a bunch of Boeshield onto the pivot points, which helped a bit, but not enough. I followed up with a bunch of Sea Foam spray, using the shift lever to pull the derailleur up to the high gear, returning the lever to low, and pushing the derailleur back to low. Did this a number of times which seemed to help a bit, but not enough for the spring to overcome the resistance of the rusty pivots. Finally I took the derailleur off and soaked it in MMO for about an hour. Reinstalled it, and continued to work it by hand. It seems to be moving better, but is still not returning to its default rest position. Any other ideas short of replacing the derailleur? Thanks!
 
My go-to is Triflow for that situation but it sounds like you have pretty much lubed the [censored] out of it already. When I usually do is remove the derailleur from the bike and work it by hand; you can back off the limit screws to get a little longer swing while doing this as well. Do not forget to pay attention to your cable system as well. At a minimum drop the housings out of your braze on's and make sure them move completely freely. Any stiction here can make a big difference. Even better, if your der's are that rough I'd bet its a good time to slap new cables and housing on as well. Slick stainless ONLY, of course.
 
Maybe follow-up with a better lubricant (i.e oil) now you've got it partially freed, and continue to work it by hand until its freed off enough. I've freed off very corroded bike transmissions by working them with vegetable oil (which is pleasanter on the hands and a good lubricant) but you have to clean that off with solvent (I use kerosene or diesel) once its free (after maybe using it a little) otherwise it'll gum everything up worse than before. Stuborness really. When they're that bad they've already suffered damage and perhaps in that situation it isn't really worth the trouble.
 
Originally Posted By: buck91
My go-to is Triflow for that situation but it sounds like you have pretty much lubed the [censored] out of it already. When I usually do is remove the derailleur from the bike and work it by hand; you can back off the limit screws to get a little longer swing while doing this as well. Do not forget to pay attention to your cable system as well. At a minimum drop the housings out of your braze on's and make sure them move completely freely. Any stiction here can make a big difference. Even better, if your der's are that rough I'd bet its a good time to slap new cables and housing on as well. Slick stainless ONLY, of course.
I wondered about the cable, but it seems to still be in very good condition. May change it anyway.
 
Originally Posted By: Ducked
Maybe follow-up with a better lubricant (i.e oil) now you've got it partially freed, and continue to work it by hand until its freed off enough. I've freed off very corroded bike transmissions by working them with vegetable oil (which is pleasanter on the hands and a good lubricant) but you have to clean that off with solvent (I use kerosene or diesel) once its free (after maybe using it a little) otherwise it'll gum everything up worse than before. Stuborness really. When they're that bad they've already suffered damage and perhaps in that situation it isn't really worth the trouble.
Well, I am persistent - and that goes a long way to compensate for a lack of talent. Good thought on the veggie oil - I may try it.
 
I've never seen a derailleur rusted fast! Always the cable restricting movement. When it's on the small ring can you move it by hand to the big ring position and does is spring back when you let go of it? Did you try the cable for free movement when you had the mech off? Also did you check the shifter? They can get mucked up inside. I have one rear shifter that needs a squirt of lube inside every so often.
 
Oh yes, I've rehabbed dozens of shifters! Usually its not a corrosion issue, though. Usually its time. Eventually, after many years, the grease turns to glue and won't let the pawl swing freely. Some take more work than others but the trick is solvent and a fine pick to move the mechanisms around.
 
Originally Posted By: buck91
Oh yes, I've rehabbed dozens of shifters! Usually its not a corrosion issue, though. Usually its time. Eventually, after many years, the grease turns to glue and won't let the pawl swing freely. Some take more work than others but the trick is solvent and a fine pick to move the mechanisms around.
Yep. Some Liquid Wrench or WD followed by a light lube gets it going again. Check your shifter OP.
 
Originally Posted By: ragtoplvr
soak in evapo rust Rod
I did the EvapoRust soak - it helped a bit, but ultimately the resistance in the four sets of pivot points (not three as I'd said earlier) remains too much for the spring to overcome. I bought a new one yesterday and installed it. It works great. (Went with another Shimano SLX from my favourite local bike shop.) Will keep the old one around though, and will keep working it. It would be good to have it as a backup. Replaced the cable as well - it was in good condition other than the frayed end which I couldn't thread through the stop on the derailleur. Bonus: The EvapoRust did a good job on an old set of Craftsman needlenose pliers.
 
Originally Posted By: buck91
Just a tiny drop of your favorite oil in each pivot before storage will prevent a recurrence!
An ounce of prevention ... lesson learned! I'll probably overdo it from hereon.
 
Originally Posted By: Number_35
So, I put the fat bike away last April after washing the winter muck off, and it sat for a few months until I got it out about just over a week ago. To my dismay, the front derailleur (Shimano SLX) was frozen in place - that is, likely rusted. When I try to shift down to the lower chain ring, the derailleur stays in place. I'm afraid the pivot points are rusted. Dumb, and completely preventable - I should have lubed it before putting the bike away. Anyway, I started out by spraying a bunch of Boeshield onto the pivot points, which helped a bit, but not enough. I followed up with a bunch of Sea Foam spray, using the shift lever to pull the derailleur up to the high gear, returning the lever to low, and pushing the derailleur back to low. Did this a number of times which seemed to help a bit, but not enough for the spring to overcome the resistance of the rusty pivots. Finally I took the derailleur off and soaked it in MMO for about an hour. Reinstalled it, and continued to work it by hand. It seems to be moving better, but is still not returning to its default rest position. Any other ideas short of replacing the derailleur? Thanks!
Silikroil (Kroil) with silicone has excelled in frozed rusted stuff for me. PB Blaster and WD-40 failed.
 
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