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Old 09-20-12, 07:16 PM   #1
rangerbill
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Chainring Bolt Help!***UPDATE - FIXED IT!

My 16 year old son has a 1993 Shogun Trail Breaker, According to BikePedia.com it features Shimano Tourney components, Front Chain ring is Shimano Tourney, 28/38/48 teeth, Specs say FC-TX71 or FC-TY33. Rear is a 6 speed. Now the front chainring, the 48 is solid with the crank arm and mounted to the crankset. However the 38 and 28 are solid together but no longer connected to the 48. just spin freely, flopping on the spindle. I believe it needs new chainring bolts to bolt the 38 to the 48. Bolts are there but are pulled through the holes in the 38.

LBS has been scratching their heads for over a week and a half. Say they never seen anything like it and can not find any bolts and suggest I purchase a complete new crankset for $75 to $85 installed or try the hardware store. (purchased the bike at Goodwill for $14.95)

In checking the web, Amazon in particular I find a multitude of chainring bolts.

Question: could someone recommend the the correct bolts? by model numbers or links, Please.

Thank You!

Last edited by rangerbill; 09-29-12 at 02:07 PM.
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Old 09-20-12, 07:25 PM   #2
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Post a close-up photo of the hole on the inside of the crankarm where the inner-rings would attach. Shimano doesn't list any replacement bolts for holding the inner chainrings on. They may just be riveted on and the rivets have pulled out on yours.

Easiest repair would be getting a new crankset. Can typically pick them up at shops for free or $5-15 bucks from their used-parts bins. College bike co-ops are also a good source for used parts. Or you can pick up an entire bike from thrift stores or garage sales for $10-20 and end up with lots of spares.

More difficult repair would be to tap the hole in the crankarm for bolts. Measure the bore-diameter and find the next size up metric threading. Probably 8x1mm or some such. If you don't want to drill all the way through crankarm, you'll need a blind tap.
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Old 09-20-12, 07:45 PM   #3
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My Apologies on the Picture. I haven't picked it back up from the LBS. As for the crankarm, no problem with it, not being rude, just clarifying. If he wished he could ride it with the chain on the 48. The crank arm is attached solid and the 48 pulls as normal, could ride like normal. however the 38 and 28 are loose and flopping/spinning. I will pick it up tomorrow and do the photo. Thank you Sir, as i said just clarifying about the crank arm.
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Old 09-20-12, 08:28 PM   #4
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I am pretty sure that crank was riveted or stamped and spot welded. If you or the shop can pull the crank I am sure you could get rid of the 2 smaller chanrings and just use the big one if you wanted to. Otherwise previous suggestions for used cranks are good too!
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Old 09-20-12, 10:09 PM   #5
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Thanks Everyone, I will post photo's tomorrow. Good Night
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Old 09-20-12, 10:53 PM   #6
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Baby bolts??
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Old 09-20-12, 11:21 PM   #7
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Originally Posted by bikeman732 View Post
I am pretty sure that crank was riveted or stamped and spot welded. If you or the shop can pull the crank I am sure you could get rid of the 2 smaller chanrings and just use the big one if you wanted to. Otherwise previous suggestions for used cranks are good too!

Agreed. Tourney-level parts had stamped and riveted chainrings. If all you want to use is the big chainring, just leave the broken ones off.
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Old 09-20-12, 11:53 PM   #8
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Hmmm, why should this be so hard??? Either bolt it together in the old rivet holes or re-rivet the chain rings back together.

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Old 09-21-12, 02:41 PM   #9
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My apologies to the LBS. It wasn't that he head never seen chainring bolts etc, just he had not seen any like these.
The heads are hex like a regular bolt head. then a spacer then a "nut" that is round and sits in the hole of the 38. now that nut appears to have an allen socket in the center. It may not be Tourney it says "custom" on the crank arms. Photos to follow:
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File Type: jpg 0921121455.jpg (94.9 KB, 30 views)
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Old 09-21-12, 03:21 PM   #10
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Ok Got the unknown "Bolts" out they are a soft, pliable type metal shell filled with white plastic. suspect I have a case of the "Rivots" now that I have an example I will make a trip to the Hardware store and try to find something workable. I know the head will have to be thin to allow the chain to seat on the 28. But Thanks Guys, If anyone has any more tip, all are appreciated!
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Old 09-29-12, 02:17 PM   #11
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Thank you all for the help, and encouragement!

It was a major rebuild of the chainring. The bolt heads that hold the 38 to the 48 had to be ground to the thickness of a washer to fit between the rings and allow the chain a space. then I had to drill the rivets that hold the 28 to the 38 to get the bolts into place and then bolt the 28 to the 38. I then had to grind down the nuts on the inside to stop from rubbing against the chain stay. the bolts protruding on the crank arm side I left, I told my sin he could get a hacksaw if he wished. but he wanted them left. Here is a pick of the completed product. BTW: starting my bike tool collection. I just paid $20 for a bottom bracket service at a bike shop on my Perigee. Now due to this, I have the tools and knowledge to do that myself!

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Old 09-29-12, 08:10 PM   #12
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Great work! Very innovative solution to an uncommon problem!
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Old 09-30-12, 08:36 AM   #13
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You did $100 worth of work to salvage a $25 crank but the learning experience, satisfaction and future savings were worth twice what you contributed. Nice work.
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Old 09-30-12, 08:44 AM   #14
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At least the steel rings mean it'll keep on kicking for a long time ; )
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