Newbie Needs Help With Troubleshooting
 

Hello, I'm just starting to get into biking and I'm a complete noob so please forgive me if I don't use the proper terms etc.

I have a 2008 Giant Yukon and it won't shift onto the large chainring. I was trying to adjust the front derailleur when I noticed that it won't even reach the large chainring. What I mean is, if I pivot it by hand, with the chain off and the H screw backed off completely, it doesn't rotate enough to even move the chain onto the outside ring. I was a little puzzled by this until I noticed some exposed threads on the drive side of the BB (see attached pic).

I think the BB has backed out about 1/2" and therefore the crank and chainrings have too, preventing the front derailleur from reaching the large chainring.

http://bikeforums.net/attachment.php...hmentid=206476

Does this seem right? Would it cause my problem?

I assume I need special tools to remove the crankset and fix the BB. Is it worth trying to fix it myself or should I take it to my LBS?

BOTTOM BRACKET: TruVativ Powerspline
CRANKSET: TruVativ ISO Flow 3.0, 22/32/42

Thanks for your help!

tools needed: to remove crankarms , and remove the BB ,
Price out the cost of those tools, and make up your mind.

Option: taking it to the shop that you bought the bike from,

inadequate torque on installation? may have an 'OOps',
from the mechanics that assembled the bike.

assuming it is a recent purchase ..
LBS here does after-sales, new bike services for 6 mos.

If the BB is unscrewing itself, that's most likely the problem. You might want to get it looked at fairly soon, as the BB won't be properly supported on the non drive side if it's moved out on the drive side, so it might damage the drive side threads if you ride it hard. I got my splined BB tool for about £4, and my crank puller for about the same, as I recall. If you intend to work on bikes a lot, it would probably be worth buying the tools.

Simple repair with the right tools. You decide whether it is best to buy the tools, or have a shop do a quick repair for you. The repair should be cheaper than the tools, but I always like to do work myself, so I would be buying the tools.

Are your crank arms making any clicking noises, or seem loose? if the BB cup is backed off enough to screw with the alignment, the spindle should be loose enough to rattle around. This may cause some damage.

No noise and they seem tight.

I forgot the mention that the exposed threads have rusted over time. Do you think they can still be threaded back in? Should I just install a new BB?

Not if it's a cartridge BB, which all the Powerspline BBs are as far as I know. It won't rattle unless it actually comes out of the threads, although the non-drive crank will hit the frame if it moves too far over.

And reyemka, you should be able to thread the BB back in, although it might be a good idea to clean the threads with wire wool or something.

I'd be willing to bet you've hit the nail on the head. The crank has moved outward beyond the ability of the derailleur to accommodate. Solution is to remove crank, re-install BB (clean and grease threads), torque to spec, reinstall crank.

Definitely a fairly easy DIY, but you'll need a BB tool and probably a crank puller. Neither is expensive, but would total more than the shop will charge, let alone time doing it the first time. The job itself is easy using online guide or a basic repair book. You'll have to adjust the FD, but it sounds like you already have an understanding of that so it shouldn't be hard for you to do that properly, again with simple guidelines available online or in a good book.

If you're a complete Noob, the path of least resistance is to take it to a reputable bike shop. Should be a minimal charge ($5-$25, depending on minimum charges, etc.) if the BB is still OK (and a reputable shop will determine that and not try to sell you something you don't need).

If the BB is shot, it will add another $25-$30 to the cost. Either way, shouldn't be a big deal.

If you really like repairing things and like buying tools, do it yourself. If the shop is backed up and they will want to hold it for a week, you might want to do it yourself. If you just want to get it done and don't have a burning desire to learn this stuff, just take it to a shop - should be an easy, quick, cheap fix for them.

Thanks for the replies. I'll try and do it myself if I can find the tools locally (Postal Strike currently in Canada :mad:). If not, I'll take it to my LBS.