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Would you ride a triple ring with stripped thread?

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Would you ride a triple ring with stripped thread?

Old 07-15-19, 03:40 PM
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noobinsf 
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Would you ride a triple ring with stripped thread?

I recently bought a used Sugino AT, and, upon disassembly, I realized that one of the 74bcd holes is stripped. I can still get a bolt lodged in there, but this sacrifices the bolt, and I'm unlikely to be able to get it out again (easily, or at all). Would you ride a ring secured there, assuming all of the other bolts work normally?

I have BBs in two different lengths, so I guess another option could simply be to make it a compact double with 52-34 rings on the 110bcd area, but I would like to have that 28t ring for occasional times I would need it.

I bought it from a charity bike shop, so I'm not going to seek any recourse -- I'm sure they had no idea, and my money is going to better use in their training programs.

WWYD?
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Old 07-15-19, 03:49 PM
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Originally Posted by noobinsf View Post
I recently bought a used Sugino AT, and, upon disassembly, I realized that one of the 74bcd holes is stripped. I can still get a bolt lodged in there, but this sacrifices the bolt, and I'm unlikely to be able to get it out again (easily, or at all). Would you ride a ring secured there, assuming all of the other bolts work normally?

I have BBs in two different lengths, so I guess another option could simply be to make it a compact double with 52-34 rings on the 110bcd area, but I would like to have that 28t ring for occasional times I would need it.

I bought it from a charity bike shop, so I'm not going to seek any recourse -- I'm sure they had no idea, and my money is going to better use in their training programs.

WWYD?
Seems odd the hole will get a bolt stuck in it . If there is still that much meat left, I would take another same thread bolt that is longer, file or cut some sharp slots to make a chaser, use anti-seize for lube and try to restore whats left. 2 steps forward, one step back till you get through, then clean and loctite.
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Old 07-15-19, 04:12 PM
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If it's a 5 bolt then 4 bolts should be sufficient to keep the ring on securely. I wouldn't worry too much.

If your OCD is going to bother you, I'd switch cranks or clean up the threads. If there's enough material left to simply chase the threads, I would get a bottoming tap of the appropriate size and use that. If there isn't, consider drilling and tapping a hole of the next size larger.
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Old 07-15-19, 04:15 PM
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Get yourself a tap for the hole and clean/retap the threads. If you go in straight, you should be able to clean the threads to usable again. I would loan you a tap, but you can most likely get one local for less than the shipping.
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Old 07-15-19, 04:30 PM
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I wouldn't ride it on 4 bolts. I've broken those bolts coming out of the saddle for a steep pitch. Fell to the wrong side and while I was not moving, the pavment was long ways down. Not fun.

(Aside on Avocet. They told me that was what I got for riding with the bolts loose (which I doubt). Since then, every other piece of Avocet hardware I've ridden has also broken. Retired those cranks for SunTours. Pulled them out "for the time being" to set up a new/lod bike and broke the crank across the pedal threads very early on.)

Sugino quality, even on their cheapest stuff, is good. You might get away with 4 bolts. I wouldn't try. Now, on a properly seated big or inner ring with 1) its far better support from the very short bolts and the nice fit on that shelf and 2) considerably lwer chain forces since the radius is higher - I"d ride that with no concerns at all, Juxt check the other bolts a little more often.

Ben
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Old 07-15-19, 04:48 PM
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Personally, I use the small ring infrequently enough that it might be nice to have it as an "escape gear" option, but I woudn't worry about it much.

Road Bike?
MTB?
Cargo Bike?
Gravel Bike?
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Old 07-15-19, 04:56 PM
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Nope! I tend to do my best to ensure that my bikes are completely sound, road worthy and safe to ride. Even if it is safe to ride with four bolts, the worry about potential failure would always plague me, thus interfering with my ability to enjoy the ride. So...

Cranks are not all that expensive. Though, like everyone else, I hate parting with my money, twenty or thirty dollars is not all that much to pay for peach of mind and enhanced safety. That said, I did spend the last few weeks in Jamaica, last winter, riding my old Bianchi with one missing rear spoke. That said, a wheel going out of true is not as prone to dumping me on the ground, something that a snapped off chain ring just might do.
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Old 07-15-19, 05:43 PM
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Originally Posted by seypat View Post
Get yourself a tap for the hole and clean/retap the threads. If you go in straight, you should be able to clean the threads to usable again. I would loan you a tap, but you can most likely get one local for less than the shipping.
+1.Tap it like a keg.

Or, on steep inclines in the granny gear, try not to imagine that ring buckling catastrophically as your chain falls off and your calf drives down through the outer ring.

Plus, rings missing bolts tends to go out of true, which affects shifting and can lead to dropped chains.
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Old 07-15-19, 06:04 PM
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I wouldn't.
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Old 07-15-19, 06:18 PM
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Originally Posted by noobinsf View Post
I recently bought a used Sugino AT, and, upon disassembly, I realized that one of the 74bcd holes is stripped. I can still get a bolt lodged in there, but this sacrifices the bolt, and I'm unlikely to be able to get it out again (easily, or at all). Would you ride a ring secured there, assuming all of the other bolts work normally?

I have BBs in two different lengths, so I guess another option could simply be to make it a compact double with 52-34 rings on the 110bcd area, but I would like to have that 28t ring for occasional times I would need it.

I bought it from a charity bike shop, so I'm not going to seek any recourse -- I'm sure they had no idea, and my money is going to better use in their training programs.

WWYD?
How about some pics?
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Old 07-15-19, 06:25 PM
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i'm surprised no one suggested a heli-coil. quick, easy, and a correct fix! never worry about it again.
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Old 07-15-19, 06:26 PM
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I'm surprised that nobody has suggested the obvious solution. Buy a helicoil or similar type stripped-thread repair kit of the appropriate size and follow the directions on the package.
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Old 07-15-19, 06:35 PM
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Originally Posted by merziac View Post
How about some pics?
Are you wanting pics of the crank for a diagnosis, or just pics of an AT crank? I just got one in that I can post pics of.
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Old 07-15-19, 06:59 PM
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Originally Posted by seypat View Post
Are you wanting pics of the crank for a diagnosis, or just pics of an AT crank? I just got one in that I can post pics of.
Mug shot of the offender.
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Old 07-15-19, 07:19 PM
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Great minds think alike!
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Old 07-15-19, 07:47 PM
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Originally Posted by merziac View Post
Mug shot of the offender.
That definitely would help with assessment of the situation.
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Old 07-15-19, 08:09 PM
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Sorry, pics coming tonight -- work, kids, etc
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Old 07-16-19, 12:15 AM
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Originally Posted by noobinsf View Post
Sorry, pics coming tonight -- work, kids, etc
I kind of doubt that a Hei-coil with such fine threads exists for this application.

First thing though is to measure the length of the shank of the bolt that pulled out the threads.

Then find a longer one and see how far you can thread it in past the damaged threads, and as merziac mentioned you could then cut sharp slots in the longer bolt's threads so that it becomes self-tapping if the threads need to be extended. Hopefully there is enough hole depth to play with.

Longer bolts are available, I would use steel but might settle for aluminum. I doubt that such a fine-threaded tap would be easy to find.
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Old 07-16-19, 02:00 AM
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Here are a couple of shots of the hole in question, and a couple of shots of the bolt that I threaded in after an effort to clean the threads.




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Old 07-16-19, 02:03 AM
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This is the original bolt with the head snapped off, which happened after two days of soaking with Liquid Wrench.

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Old 07-16-19, 02:06 AM
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I really appreciate everyone’s advice so far. I am thinking I’ll go the route of a compact double to avoid issues.
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Old 07-16-19, 03:26 AM
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A new CR bolt that is long enough to go to the bottom of the threads plus carefully cleaning out the threads in the crank and removing any partial bits of threads, de -grease then assemble with a strong Loctite thread locker - not the blue designed for easy disassembly.

Should work OK.

I'm like @randyjawa I like to know that everything is properly assembled and works correctly. When I notice something doesn't feel or sound right, when I come off a ride, I take the bike into my shop and check it out to find the cause before I ride it again.

BTW, back in the 80's I went through 3 Loctite Engineering Seminars where I learned about their complete product offerings and how to properly apply them. I've seen Loctite products used in the assembly of bulldozers and other heavy equipment, large diesel engines used to power ocean going ships and parts down to micro electronics.

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Old 07-16-19, 06:10 AM
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Those threads are still usable. Retap/clean them to the bottom and do what verktyg said.
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Old 07-16-19, 07:48 AM
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Yeah, from the looks of things (good photos btw) it's the bolt here that seems to be the worse for wear, not the crankarm! Surely that's an alloy bolt for the threads to be leveled as shown, no?

Loctite is useful, I've used the Red (high-strength) formulation to secure a mountain-bike pedal in a stripped crankarm and it never let go even after nearly a year of riding!

But I will advise that bolts 1) whose threaded engagement is longer, 2) that are hollow 3) are made of soft metal and especially 4) are of relatively small diameter should be used with a weaker grade of LocTite, unless there is the option of applying considerable heat to the parts when disassembly is required. This assembly can be heated, though I suspect that with a good steel bolt reaching in far enough to achieve good tightening torque, that the assembly is likely more than strong enough without use of any "liquid lockwasher".
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Old 07-16-19, 08:00 AM
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Randy said "I tend to do my best to ensure that my bikes are completely sound, road worthy and safe to ride. Even if it is safe to ride with four bolts, the worry about potential failure would always plague me, thus interfering with my ability to enjoy the ride. So..."

and I agree. But why not get a helicoil kit and put a helicoil in there ? it will be stronger than the original.

this kind of failure DOES happen. I had a TA Carmina strip out like this. Fortunately the spider is replaceable. Wasn't deep enough to helicoil.

Mark Petry
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