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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 09-26-04, 04:31 PM   #1
Jonnny
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I hope this is the appropriate place to ask this question.
I just purchased a new Trek Navigator 200 and the crank or Bottombracket is slightly off so that if you look at the front derailleur you can see the chain moving approx. 1/16" from side to side when turning.
The bike shop said that this is normal for that type of bottom bracket. Bolted on I guess-no spline??
I have my doubts as all of the other bikes I have ever purchased have straight and true cranksets .
they checked it to make sure it was tight.
I guess this is why I got that brand of bike
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Old 09-26-04, 05:14 PM   #2
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more likely, the chairings are less than perfectly true. not at all uncommon, nothing to worry about if it doesn't affect shifting or rub the derailleur.
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Old 09-26-04, 05:30 PM   #3
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If there is no play in the BB(Easy check, just try to rock the crank arms back and forth) then the chainrings are a little bent. This is not unusual in a less expensive bike. I tap them straight with a rubber mallet
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Old 09-26-04, 06:58 PM   #4
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An adjustable wrench clamped down on the chainring works for me.
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Old 09-26-04, 08:27 PM   #5
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I don't think it is the chain rings as they are all off in the same spot.
the guy at the bike shop said it was becasue of the way that the crankset mounted to the bolt on BB.
He was not trying to sell me another BB but said a splined would more than likely elimnate the problem and I guess that would mean a new crankset that was splined but maybe not the chainrings. Thinking maybe those chainrings would be used with a new splined crankset and BB???
Not sure but what gets me is that cheaper bikes don't have that issue and I feel like it should not be that way on this new Trek.
Maybe I am wrong?
I hate spending that much money on something to have it off like that???????
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Old 09-26-04, 09:26 PM   #6
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What the mechanic is suggesting is A) the cranks were cast poorly, which is possible for any design, or B) the spindle was bent from the start, which is possible but not likely.

the chainrings on that crankset are almost certainly riveted and cannot be transferred. cranksets cost not much more than crankarms anyway, and for what you'll pay for a splined crankset and matching BB, you'd probably be leaving a good deposit on another bike.

if the chainrings are all off in the same spot, the spider on the crank is probably bent. i'm pretty on those cranks the middle and inner chainring are simply riveted to the outer ring. just whack it with a drift and hammer in the appropriate places until it suits you.
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Old 09-26-04, 10:10 PM   #7
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it is a Shimano C203 48/38/28 so how much to replace that do you think.
I will have to look to see if the sprockets are riveted.
I am writing to Trek....not holding my breath....got any suggestions
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Old 09-27-04, 07:31 AM   #8
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If you really want to do it... LX crankset, 48-38-28, $93, matching BB, $37, plus labor costs. These are priced off of Harris cyclery's QBP catalog, the LX crankset is frankly a little underpriced if you go by normal markup standards. So pay a third of the bike, or hit it with a hammer. In my mind there's no real decision here, use the wrong tool for the right job.
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Old 09-27-04, 10:46 AM   #9
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Not sure what I am going to do other than Trek has replied saying that it should not be that way.
I was curious however and tried to find the items you advised and I found the following only:


Shimano LX M572 175mm 26-36-48 Silver & Black Crankset***(CR5666)
$92.95
Specifications:
BCD: 64/104
Color: Silver/Black
Length (mm): 175
Rings: 26-36-48
Spindle type: Shimano Octalink V2
Spindle Width: 121/126
Weight (grams): 656


I did see the 28-38-48

thank you very much for all of your assistance, you have been very helpful
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Old 09-27-04, 04:18 PM   #10
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I looked at a bike identical to yours today while on a call at a local college. The owner spun the crank for me and the chainrings exhibited no wobble.

If your bike is, in fact, new, the lbs fromwhich you bought it should make it right. Either they boogered it up in assembly or the crank spider is bent..

Nicely insist they correct this.

Doc
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Old 09-27-04, 04:25 PM   #11
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Quote:
Originally Posted by dafydd
What the mechanic is suggesting is A) the cranks were cast poorly, which is possible for any design, or B) the spindle was bent from the start, which is possible but not likely.
The crank/spindle interface may not be prefect. Sometimes you get a worst fit case,that might be made better by removing crankarm rotating 90* and rechecking.
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Old 09-27-04, 04:25 PM   #12
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Quote:
Originally Posted by DocF

If your bike is, in fact, new, the lbs fromwhich you bought it should make it right. Either they boogered it up in assembly....



Doc
Not likely as cranks come installed from the factory.
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Old 09-28-04, 08:13 PM   #13
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well I am now considering the LX as I looked at the crank closely and I was surprised to find that it was spot welded or riveted and did not look like that quality of a piece.
I may not have purchased that bike knowing about that.
I just assumed that it was high quality.

Don't assume anything!!

So I guess I would like to get an opinon of this crank:
Shimano LX M572 175mm 26-36-48 Silver & Black Crankset***(CR5666)

The one you suggested that is not to pricy

Thank you
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Old 10-01-04, 10:42 AM   #14
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also any ideas on the BB width (73x118mm, 113mm, 121mm, 126mm,) for that crank (Shimano LX M572 175mm 26-36-48) on that bike (Trek Navigator 200)
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