CRANK ARM WORKING LOOSE?

[sd]

The nut keeps working loose and on the other side there is no cover? I assume there was but it has come off?

Never seen the joint between the 2 pedal shafts before. Is something missing other than the cover? Notice its loose after about 20 miles. Any ideas about why it is working loose? Thanks SD

[sd]

[Danneaux]

Eh, boy, that is a sickening feeling, SD. All empathy and sympathy your way.

I presume this is for a square taper crank and internal bottom bracket?

For a taper - spindle crank to become noticeably loose often means it has been a little loose and fretting on the flats for some time, gradually enlarging the hole (socket) in the crankarm. Once that happens,  the result tends to be as you describe, where the crank chronically re-loosens.

In case you got really lucky and the bolt wasn't right enough and the crankarm freshly loosened and hasn't enlarged,  *then* tightening it to proper torque should drive the arm onto the tapers enough for it to hold snugly.

The recommended tightening torque should be sufficient to hold the bolt and arm in place. Any washers or dust caps usually have just enough clearance they wouldn't keep the bolt from loosening.  Their purpose is more to keep dust and dirt out of the threads so a crank puller can be easily fitted.

If 't'were me, if tighten the crank bolt to full specs using a torque and and check the result after riding not too far from hone. If it stays nicely in place,  you got lucky. Of it wobbles loose, then you may need to look for a new arm.

For what it is worth,  I once managed to get a friend home from a long day ride with a similar problem by stopping at a store to buy a tart so I could salvage the thin aluminum tray to make shims. They were hard to fit between crank and spindle and required a second tart be purchased  but the result was solid enough for the 75 mile ride home without incident. It took some doing to convince him this was *not* a permanent fix. For diagnostic purposes or an emergency way to get home,  it might be worth a try.

Fingers crossed for a good outcome!

All the best,

Dan.

[sd]

Trying to download pictures from photobucket but the pictures won't uploaded. There is an empty tube looking from the opposite crank arm?

[Danneaux]

Thinking about it more...

If the arm is still tight, then things are pretty much golden.

If it is just the bolt (or occasionally a nut, though that is rare these days), then it may have damaged threads on the bolt or spindle or may not be tightened to spec.  A small drop of blue LocTite might resolve the problem.

Best,

Dan.

[sd]

Yeah but should the shaft between the 2 cranks (arms) be empty. Should I undo the bolt and check the threads. I think there is lock tight on there. Is it a blue green colour? The cranks are fire fox. By the way I think I will stick with the Brooks saddle, the previous owner did 20,000km on it! Would like to tighten it bit more to see if iI can make it more comfortable. I assume if unhappy I can loosen it again and it would unstrech?  Thanks for all this help SD

[sd]

I am lost as to why the normal method (html) doesn't work? These are probably of no use to you but I don't care. As I have been trying to take these photos for an hour with my Nexus 7 camera which only faces the user! SO LOOK AT THEM
   as it has done my head in!

http://i1311.photobucket.com/albums/s661/noncitydweller/IMG_20140625_111838_zpszetrjjfq.jpg

http://i1311.photobucket.com/albums/s661/noncitydweller/IMG_20140625_112656_zps8mcwrrul.jpg

[sd]

Just noticed you don't have to put 2 addresses in as the rest are visible wit this method

[Danneaux]

Hi JB/SD,

I'm sorry you had such a rough experience linking photos. Your method worked okay, but the real culprit is the gallery view at Photobucket upsetting the applecart.  It should be possible to link to an individual photo by html but not to the whole gallery view.

As to the problem, seeing your photos helped me tremendously in helping you.

This is a Truvativ GXP ISIS-design crank similar to the Shimano Octalink but different in some key, critical ways.

I recalled a thread from awhile back on another forum that seems to address your entire issue: http://www.bikeforums.net/bicycle-mechanics/696248-stupid-truvativ-elita-gxp-left-crank-keeps-getting-loose.html

The news is not encouraging. The spindle is swedged to the right arm and can't be disconnected. The other end is splined, tapered steel with incomplete run-on. The left fastening bolt requires really high initial torque. If it wasn't tightened adequately to begin with or was not maintained,  it can work loose, fret,  and the hard steel spindle splines can chew at the soft aluminum of the crank arm, producing the sad and unfortunate results you describe.

The older models were (mis) designed in such a way that even normal pedaling could loosen the retention bolt. I'm not sure where yours fits in the chronology,  but this may be a case of "they all do that eventually". The design was clever, but less than ideal on some key ways.

If it were me, I'd try three things in this order:
1) tighten down that retention bolt to the specified high torque mentioned in the link above, using a torque wrench...and hope for an unlikely but good outcome. You'll know soon enough if it works or not and it is free to try.
2) search for a new left arm on eBay.
3) ditch it all and go for a decent but inexpensive crank and square taper BB,  something like Shimano's humble Alivio, which is available in black, looks similar,  would get you back on the road for little coin, and would run trouble free for ages. This is the course of take.

I wish I could be more encouraging, but I think that left arm may be unsalvageable. I'm hoping someone will disagree.

Best,

Dan.  (...who takes no joy whatsoever in delivering what is likely bad news)

[Danneaux]

...As for your saddle question, please use care when tightening the Brooks adjuster nut/bolt set in the saddle nose. 

Once stretched,  leather won't spring back...sadly, it stays stretched because the fibers have been pulled apart.  I have seen over tightened Brooks saddles develop a center ridge Jobst Brandt described as a hatchet for one's posterior. I have also seen the nosepiece rivets crack the saddle leather when the tension bolt is tightened too enthusiastically.

By the way, friend and past neighbor Toshihiko had remarkably good luck reblocking vintage Brooks and Ideale saddles that had deformed because they were ridden wet. He got them cheap and started his experiments figuring he wasn't risking much.

Basically,  he loosened the tension bolt and soaked the saddle overnight in a bucket of water. After removing it from the water,  he allowed the water to sluice off naturally, then stuffed the underside/interior with newspapers and rags, which he changed periodically.  He used a variety of clamps to ensure the saddle skirts formed and dried close to the saddle rails. He placed the saddles out of direct sunlight in an area with good ventilation.

Once dry and covered with a thin skim of Proofide, the saddle looked nice and proved functional without any issue other than some added tension to make up for the water stretching.

This is different, however, from overtightening the tension nut. That can cause damage that us pretty irreversible,  so go at it a little at a time in small increments. More isn't always better.

In fact, more direct results can sometimes be achieved by punching three holes in the margin of each side skirt and lacing them together across the underside. This can do wonders for restoring splayed sides and sagging tops,  making the saddle more comfortable as a result and without the risk of over tensioning.

Best,

Dan. (...who remembers that with great power comes great responsibility...and it is possible to wield great power with that tension nut)

[sd]

2) search for a new left arm on eBay.
Any or exact match? Sorry if that makes no sense as I generally do as little work as possible on bikes!

[Danneaux]

I think in this case, JB, it had better be an exact match. There are several versions of Truvativ GXP cranks out there,  and I'm not at all sure they are compatible between generations.

My phone screen truncated the title on your post in the email update notification and I got all excited, thinking for a moment it said "Crankarm working" but alas, it was not to be.

Best,

Dan.

[Danneaux]

JB,

See: http://m.ebay.co.uk/sch/i.html?_nkw=truvativ+firex&isNewKw=1&_pgn=1&epp=24&itemId=&isRefine=true&mfs=GOCLK&acimp=0&sqp=truvativ+firex&trksid=p2056088.m2428.l1313.TR1.TRC1.Xtruvativ+firex

Best,

Dan.

[Andre Jute]

That crankarm is a bottomless pit in the making, like looking for a windscreen for a three-cylinder DKW from the first half of January 1954; it'll cost more in the end to find a match than buying several good, long-lasting new setups. A good setup would be a square-taper bottom bracket and a matching crankset. This would be a first class, cheap setup:

A bottom bracket found under the original maker's name on my Utopia, a bike that costs BMW money, here for twelve quid near the bottom of the Stronglight range (that's another good brand name!)
http://www.spacycles.co.uk/products.php?plid=m2b0s110p141
Nothing wrong with the plastic cup model of the same thing, if you want to save another couple of quid. There is also a more expensive ali cup model in case your bike frame is ali. Look at the photo and find the spec to know which tool you need; that looks to me like it needs a common Shimano bottom bracket tool. You should have one in your toolkit if you're to be a cylcist.

Cranks like some of the better-informed forum members have on their bikes (and that many people paid four or five times this much for -- they're out of the back door of the Sugino factory):
http://www.spacycles.co.uk/products.php?plid=m2b0s109p3051
Note that you have to buy crank bolts as well (unless the old ones fit -- does anyone know if they fit?).

There is zero point in spending any more than this for a bottom bracket and cranks unless you're aesthetically ultra-sensitive or so fashionable you just must have a poncey brandname on your cranks or so rich you can afford a Royce bottom bracket (which also has its fans here -- I don't do the mileage to justify one).

This is given on the assumption that your chainring is good and fits.

If you need a new chainring and chain as well, I suggest you do the job right and get a Surly stainless steel chainring and a KMC X8 which is a fave here (with the more expensive X1 coming up fast). That would later let you add a Chainglider which will keep your ankles clean and cause your drivetrain to run forever without much attention or wear.

All of this is conservative engineering, unlike the [troublesome model fitted to your bike*]. This is a perfect example of why most experienced cyclists won't touch the hyped "improvements" and "new standards" that bike marketers come up with to corner a piece of your money.

*Minor language edit by Dan to reduce possible libel concerns for Thorn Cycles, who host this Forum.

[JimK]

the hyped "improvements" and "new standards" that bike marketers come up with to corner a piece of your money.

I went out last weekend on a ride that was reasonable long for me - 47 miles, my longest so far this year...

http://www.mapmyride.com/routes/view/449813514

Coming down from Lake Hill into Bearsville, I passed a dozen riders or so who were going the other way, up the hill. They looked like serious folks but were a bit spread out and not going super fast. Hmmm. Then in Woodstock I saw there was a kind of rest stop set up at the bike shop, so I stopped by to see what was going on, which turned out to be a 600K ride:

http://thehudsonvalleyrandonneur.blogspot.com/2014/06/the-catskill-600k-perfect-brevet.html

wow! Anyway I hung around and chatted a bit with Brian B, who is a serious randonneur himself. He was waiting for two more riders to go through so didn't mind the distraction. He asked me whether I had had my Rohloff long enough to verify its cost-effectiveness. Hmmm. I will probably never be able to get a real sense of that: I just don't have enough other experience, etc.

But now Andre reminds me of what lead me to that hub. It was the STI shifter failing on my Trek 520. A 7 speed shifter. Nope, they can't be repaired, and they don't make them any more! I managed to switch to downtube shifters so that bike is still in reasonable shape - some funny dents in the rims so maybe I will cut my wheel building teeth on it. But this whole migration to 10 and 11 speed clusters.... I don't really have anything particularly against derailleurs. But these monstrous 10 speed things? The whole direction they are going is nuts. The Rohloff is sturdy and practical. Yeah, unfortunately the price is a bit different than that of a square taper bottom bracket!