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Bicycle Repair/Roadmaster loose front gear set

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Question
I bought a friend a ladies Roadmaster MTN SportrX. The front gears wobble and I do not see where to tighten them. The pedals do not wobble - they turn true.

Perhaps there is a missing piece that is needed to keep this three gear cassette in place.

Thanks for your help.

Doug.

Answer
The problem of wobbling chainrings-the big gears attached to the cranks and pedals-can be attested to these culprits:

1. The crankarm is loose on  and/or installed crookedly onto the crank spindle. Try tightening the fixing nut/bolt in the crank arm. If the arm/rings still aren't straight, then the arm must be removed-requiring a special tool-then re-installed.

2. The chainrings and/or the piece(s)  which mount them to the crank arm-called the "spider"- are bent due to impact,etc. Do all three rings seem to wobble "together" around a common "orbit"? If so, the cause is likely related to #1, above. If only one or two rings appear to wobble, or wobble at different points, then they are likely bent.  Straightening the chainring(s) and/or spider is a decidedly  variable endeavour, and may lead to replacement.

3. The crank spindle is bent, requiring replacement.  Usually, in this case, the wobble  symptoms are similar to cause #1.  

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James Novak

Expertise

I can answer most inquiries with respect to bicycle assembly, repair, tuning and maintenance. I am less than inclined to speak on such questions as "What kind of bike should I buy?", &/or "What is this bike worth?", etc. Any answers to these types of questions may correlate poorly to an acceptable "fact/sarcasm" ratio.

Experience

7 seasons of "Professional" bicycle service/repair, etc. 4 seasons as Instructor, Professional Bicycle Mechanic training college. n-1 seasons of riding, cracking, crushing, mutilating and breaking bikes of any & all varieties, and thus requiring intense and at-hand skills development, etc.

Education/Credentials
Certified Professional Bicycle Mechanic; Winterborne Bicycle Institute/Conestoga College

Past/Present Clients
The Hub Bicycle Shop, Hespeler Winterborne Bicycle Institute

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