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· $4000 bike - two bit legs
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Discussion Starter · #1 ·
OK..it's not a Huffy...but only a step or two above it.

I picked up a very slightly used "department store" MTB for my 9 year old son. He loves it 'cause it has front suspension, bunches of gears, and looks like Dad's MTB. Cool !!

One minor (it is minor) problem: the axle (spindle??) is slightly bent. Therefore, when he pedals, the big rings seem to wobble which makes shifting very difficult. It is usuable, but not great. it is a project for the two of us. You know...male bonding....tools, grease, farting, scratching, taking stuff apart, trying to put it back together again...male bonding. Regrettfully, he is too young for a beer...we'll wait until 10.

Remember..this is a basic bike. Where can I buy just the axle (spindle)? I can't seem to find them anywhere. When I find one, what measurements do I use??? Can I just spend $30 and buy a sealed bottom bracket?? Ifso, how do I figure on which size??

Since I have all the tools, most of the know-how, I am trying to avoid a $75 LBS charge.
 

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It is more likely that the bargain crankset has a bent spider (the part that holds the chainrings) than the BB spindle being bent. If the spindle was bent, the crank arm itself would have a noticeable wobble to it. If the crank arm itself runs strait, then its most likely the spider.
 

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What kind of bb/crank is it? Are you sure it's a bent spindle (very unusual, and would probably cause noticeable bearing binding), or could it be bent crank spider, as hayduke noted? If it's a 3-piece unit, maybe the crank isn't securely attached to the spindle. A lot of cheap bikes still have one-piece (Ashtabula) cranks, in which case your problem is more likely bent spider arms. Those are fairly easily fixed with the "inertial impact adjustment tool" (aka "hammer").

If it's really a bent spindle, and it's a loose-bearing separate-cup type (rather than sealed unit) you can find parts (loosescrews (http://www.thethirdhand.com/) is a good source. You have to match the length properly. If it's a sealed unit, you can get a replacement cheap, but you have to match thread type and length.
 

· $4000 bike - two bit legs
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1,434 Posts
Discussion Starter · #6 ·
Thanks

JCavilia said:
What kind of bb/crank is it? Are you sure it's a bent spindle (very unusual, and would probably cause noticeable bearing binding), or could it be bent crank spider, as hayduke noted? If it's a 3-piece unit, maybe the crank isn't securely attached to the spindle. A lot of cheap bikes still have one-piece (Ashtabula) cranks, in which case your problem is more likely bent spider arms. Those are fairly easily fixed with the "inertial impact adjustment tool" (aka "hammer").

If it's really a bent spindle, and it's a loose-bearing separate-cup type (rather than sealed unit) you can find parts (loosescrews (http://www.thethirdhand.com/) is a good source. You have to match the length properly. If it's a sealed unit, you can get a replacement cheap, but you have to match thread type and length.
100% sure it's a bent axle. I rolled it on the floor and noticed a 'bump'. I was thinking of trying the "IIA tool" on the axle, but have held off. I will try the online place first.

Thanks
 

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Okay

PaulCL said:
100% sure it's a bent axle. I rolled it on the floor and noticed a 'bump'. I was thinking of trying the "IIA tool" on the axle, but have held off. I will try the online place first.

Thanks
So it's a standard square-taper interface? I'd suggest you think about getting an inexpensive sealed unit rather than replacing just the spindle. For hardly any more money than a replacement spindle, a unit like the Shimano UN54 ($20) is better than the loose-ball unit, easier to install, and probably will be maintenance-free for the life of that bike.
 

· $4000 bike - two bit legs
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Discussion Starter · #8 ·
But will it fit??

JCavilia said:
So it's a standard square-taper interface? I'd suggest you think about getting an inexpensive sealed unit rather than replacing just the spindle. For hardly any more money than a replacement spindle, a unit like the Shimano UN54 ($20) is better than the loose-ball unit, easier to install, and probably will be maintenance-free for the life of that bike.
But will it fit into my bottom bracket??
 

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If its a 3 piece crank it is almost certain to be a 68mm shell width (possibly 73mm but unlikely)...even department store bikes use this size for three piece. Measure the width with a metric ruler or tape and also measure the spindle length and as suggested above, buy a Shimano UN54 and never worry about it again.
 
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