Crank keeps coming loose.
#1
Senior Member
Thread Starter
Join Date: Nov 2014
Location: Saratoga calif.
Posts: 1,049
Bikes: Miyata 610(66cm), GT Vantara Hybrid (64cm), Nishiki International (64cm), Peugeot rat rod (62 cm), Trek 800 Burning Man helicopter bike, Bob Jackson frame (to be restored?) plus a never ending stream of neglected waifs from the Bike exchange.
Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 339 Post(s)
Likes: 0
Liked 632 Times
in
229 Posts
Crank keeps coming loose.
I have an old Trek 800 mtn bike that I ride sometimes and take to burning man every year. Last year , after riding it around all week the 14 mm nut that keeps the crank arm on the bottom bracket spindle came loose and the pedal an d arm fell of on the non drive side. Luckly the cap was in place so I didn't loose the nut. Back at camp I re installed the arm and tigtned the nut as much as I could with a socket wrench. The nut came loose again after another days riding and I tightened it again.
when I got home I again tightened the nut but this time also used blue lock tight.
Fast forward to this year and again after a few days use I had the same problem , tightened the nut, it came loose after about 1 mile riding , and tightened it again. Finally in desperation I found a repair camp in Black Rock City ( the temporary city built for 2 weeks in Nevada's Black Rock Desert) and had a guy spot weld the nut to the spindle in 2 places. I'm pretty sure the nut will never come loose again but I really need to give the bike a complete service if I want it to be reliable. I can grind off the welds and probably get the nut off at the shop but I can't figure out why it kept doing this.
If anyone has any idea why this kept happening I would like to know. I have access to any parts I need to fix the bike and could just replace the whole assembly when I tear it down but I would really like to understand why this happened. This pic is of the bike before Burning Man
when I got home I again tightened the nut but this time also used blue lock tight.
Fast forward to this year and again after a few days use I had the same problem , tightened the nut, it came loose after about 1 mile riding , and tightened it again. Finally in desperation I found a repair camp in Black Rock City ( the temporary city built for 2 weeks in Nevada's Black Rock Desert) and had a guy spot weld the nut to the spindle in 2 places. I'm pretty sure the nut will never come loose again but I really need to give the bike a complete service if I want it to be reliable. I can grind off the welds and probably get the nut off at the shop but I can't figure out why it kept doing this.
If anyone has any idea why this kept happening I would like to know. I have access to any parts I need to fix the bike and could just replace the whole assembly when I tear it down but I would really like to understand why this happened. This pic is of the bike before Burning Man
#2
Senior Member
Join Date: Feb 2014
Location: Pasadena, CA
Posts: 4,848
Bikes: Schwinn Varsity
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 1931 Post(s)
Liked 742 Times
in
422 Posts
After it comes loose the first time and you ride it until it fall off, it's ruined and will never hold again. You need a new crank arm on the Non drives side.
Install new ... correct torgue value, ride it 20 miles and re-torque one time. You can put threadlocker on if you wish.
Install new ... correct torgue value, ride it 20 miles and re-torque one time. You can put threadlocker on if you wish.
#3
Me duelen las nalgas
Join Date: Aug 2015
Location: Texas
Posts: 13,513
Bikes: Centurion Ironman, Trek 5900, Univega Via Carisma, Globe Carmel
Mentioned: 199 Post(s)
Tagged: 0 Thread(s)
Quoted: 4560 Post(s)
Liked 2,802 Times
in
1,800 Posts
For the sort of repairs you'd encounter at Burning Man, maybe a tube of Park SAC-2 grip compound might help.
But, yeah, what trailangel said. Supposedly once a crank arm has been enlarged, deformed or worn it won't hold securely.
But, yeah, what trailangel said. Supposedly once a crank arm has been enlarged, deformed or worn it won't hold securely.
#4
Senior Member
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,319
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1438 Post(s)
Liked 1,092 Times
in
723 Posts
After it comes loose the first time and you ride it until it fall off, it's ruined and will never hold again. You need a new crank arm on the Non drives side.
Install new ... correct torgue value, ride it 20 miles and re-torque one time. You can put threadlocker on if you wish.
Install new ... correct torgue value, ride it 20 miles and re-torque one time. You can put threadlocker on if you wish.
#5
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,092
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4207 Post(s)
Liked 3,874 Times
in
2,314 Posts
Now that the BB axle has been damaged by the spot welds, to try to keep the old arm on, it will likely need replacing too. If the nut can't be removed the assembly might need to be cut off. Andy
__________________
AndrewRStewart
AndrewRStewart
Likes For Andrew R Stewart:
Likes For trailangel:
#7
Senior Member
Join Date: Mar 2011
Posts: 3,094
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1034 Post(s)
Liked 1,290 Times
in
743 Posts
Did you clean the spindle and apply a small amount of grease when you reinstalled it? Sometimes the crank arm will band a bit before it is properly seated. It will then loosen up as you ride. A clean spindle surface with a little grease can helps nd it will keep it from binding when you want to remove it, stopping the corrosion you get with two dissimilar metals. Try that, and actually use a torque wrench to apply the proper torque instead of going blind with a ratchet. Look up the torque values online and go by that. Generally the torque for square spindle crank arms is 25-32 ft-lbs.
#8
Senior Member
Thread Starter
Join Date: Nov 2014
Location: Saratoga calif.
Posts: 1,049
Bikes: Miyata 610(66cm), GT Vantara Hybrid (64cm), Nishiki International (64cm), Peugeot rat rod (62 cm), Trek 800 Burning Man helicopter bike, Bob Jackson frame (to be restored?) plus a never ending stream of neglected waifs from the Bike exchange.
Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 339 Post(s)
Likes: 0
Liked 632 Times
in
229 Posts
Thanks everyone for the input.
I will just grind off the spot welds and remove the nut then do a service on the bottom bracket and replace the spindle/axle if necessary. We have boxes of crank arms at the shop to replace this one with.
Burning man Eats bicycles. I have worked at a bike camp there before. No one should buy a "Burner Bike" that has not been completely serviced after spending a week at Black Rock City.
I will just grind off the spot welds and remove the nut then do a service on the bottom bracket and replace the spindle/axle if necessary. We have boxes of crank arms at the shop to replace this one with.
Burning man Eats bicycles. I have worked at a bike camp there before. No one should buy a "Burner Bike" that has not been completely serviced after spending a week at Black Rock City.