Rear Sprocket Carrier | Failed Studs

AdamFZ

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Hey all,

Was doing my chain and sprocket change today and i was in the process of doing the rear sprocket nuts up to 100nm when some suddenly went loose. Looks like the threads on the studs gave way :eek:



Anyone seen this before !?
 

TownsendsFJR1300

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Yep! There have been several failures (Not a lot)

Its been discussed before between myself and FinalImpact that the factory torque spec's IMO, are way too tight.

I posted I wouldn't go tighter than maybe 40-45 ft lbs..

Its an aluminum hub with steel studs. Most of the torque is sideways, NOT pulling away.

In either case, those studs are designed to screw in. Your threads are likely stripped. You should be able to spin them out(may need some help with a lever under two nuts locked together to remove the studs. Just to verify the thread failure.

The fix, a new hub and less torque on the nuts, helicoil (that'll support more torque, Time serts (++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread repair stripped sparkplug's, Ford sparkplug blowouts, threaded inserts threaded, repair stripped threads, stripped threads, inserts threaded inserts, Ford spark plug repair, ) , etc..
 

AdamFZ

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Thanks Scott, i did think that was way too tight. The rear shaft nut is only 120nm !

I've managed to get a 2nd hand hub of ebay for £20 so will do them up to 60nm.
 

TownsendsFJR1300

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Thanks Scott, i did think that was way too tight. The rear shaft nut is only 120nm !

I've managed to get a 2nd hand hub of ebay for £20 so will do them up to 60nm.

I'm trying to find the thread... I truly believe its one more FSM screw up that SHOULD be a sticky so this does NOT happen again.

However, it did NOT happen and failures will occasionally happen unfortunatly..

Not the thread I was looking for but the same issue:

http://www.600riders.com/forum/fz6-...que-specs.html?highlight=rear+sprocket+torque

Since the re-naming of the forum, most of the links DO NOT WORK...
 
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FinalImpact

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Its moot point w/ a new one on the way so i have this ask; Are the roads salted there and how were the threads on both the nut and the stud after the nut was removed?
- were they damaged in anyway?

It seems in many cases the self locking nut does such a great job of "locking", it either leaves shards behind which compromise the install, or damages threads on ONE or BOTH parts. If not addressed before install, threads will be pulled.

If you havea welder spin the damaged nut on the stud, burn in a puddle fusing the nut & stud and when cooler back the stud out w/a ratchet or impact gun. Save the hub as there is likely nothing wrong with it.

As for install:
Clean both the stud and nut making sure there are no shavings left behind.
Torque; Criss cross in steps at least 3 stages to final torque.

Hub is used on many Yam's R6, R1, spec is correct as the tension from the fastener is supposed to be great enough to stop rotation of the sprocket under load. The studs sticking out are not the key ingredient in stoping rotation or they would have used dowel pins. They didn't. The clamping force created by applying the suggested torque is there for a reason. I mean would you torque a rod bolt 50% less than spec because one stripped? NO! You'd fix the problem!
That said, Get as close to OEM torque w/out going over with a value you think is adequate. I'd shoot for no less than 60ft/lbs myself.
 

TownsendsFJR1300

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That's the one I couldn't find, tks John..


Now, he was installing the nuts, not taking them off, they were fine until he hit the higher torque values!

And I have to, AGAIN, totally disagree ^^..

Dowel pins will move, thats not even an option.

The studs, TIGHT, in the hub, is what's keeping the sprocket from spinning on it. 40'lbs, 80'lbs, 200'lbs, doesn't make a difference in stopping that sprocket from spinning on the hub, period..

The issue is: Can you put that much torque on that size steel nut in an aluminum thread??? Obviously NO... As posted, those locking nuts work very well. I have not seen, in 5 years here, of ONE REAR HUB bolt vibrating loose... Hummm

As there are other errors in the FSM book and parts fisch book (another post just today re headlight adapters).

The other link posted above, with other broken hubs when torqued down, ignore all of those??

If you really have to have such a high torque on that sprocket, to "FIX" the problem, Yamaha should have/would have made the hub steel, or perhaps put in HD steel threads in that aluminum hub, a deeper hole with much more threadsand MORE surface area-would be the easieist "fix" actually to be able to apply such high torque #'s..

Unfortunatly, someone following the manual religiously WILL potentiall screw up their engine turning it the wrong way per the BOTH service manuals (as you found and posted). Their also very likely strip their oil drain screw torquing it to 30' lbs..

Did I mention, on my Yamaha, 4 stroke OB engine, aluminum block, EXACT SAME DRAIN PLUG, THE TORQUE IS 20' LBS...? (see below spec's)??? Why would the same manufacturer, same size bolt, same threads, etc, use different torque values??? I stongly suspect a screw up in the manual which is not un-common..

Obviously, we won't agree but ignoring something that has happened to many folks, IMO should be brought to others attention. ldt them decide.

At least its not a major catastrophe .
 
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Cali rider

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Snipped.....

Hub is used on many Yam's R6, R1, spec is correct as the tension from the fastener is supposed to be great enough to stop rotation of the sprocket under load. The studs sticking out are not the key ingredient in stoping rotation or they would have used dowel pins. They didn't. The clamping force created by applying the suggested torque is there for a reason. I mean would you torque a rod bolt 50% less than spec because one stripped? NO! You'd fix the problem!
That said, Get as close to OEM torque w/out going over with a value you think is adequate. I'd shoot for no less than 60ft/lbs myself.

And you will probably find that you will strip a stud. It's about 12MM diameter for the stud. You actually think that it's correct to tighten that steel nut/aluminum stud to 72 ft/lbs. when the manual specifies to tighten the steel 18MM front sprocket nut to only 65 ft/lbs.?
 
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FinalImpact

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And you will probably find that you will strip a stud. It's about 12MM diameter for the stud. You actually think that it's correct to tighten that steel nut/aluminum stud to 72 ft/lbs. when the manual specifies to tighten the steel 18MM front sprocket nut to only 65 ft/lbs.?

Fasteners have many applications. Most are not used to capacity so its not a fair statement to compare dissimilar applications. In the case of the front sprocket, the splines are doing 99% of the work of preventing rotation. Plus the shaft is hardened so its just not an apples to apples thing.

Lets do a quick recap:
Aluminum hub carrier.
Steel studs with course threads into aluminum.
Steel plated nuts with SS self lock and fine pitch.

I have not seen a case where someone has pulled the studs from the aluminum hub. IMO - this is off the table. Its not an issue. The aluminum can withstand the force.

See M10 X 1.25 @ class 10.9, Notice how "lube" plays a huge role....
attachment.php



Where used: 2003 - 2011 FZ6, R6, R1 -->5SL-25366-00-00 YAMAHA CLUTCH, HUB

FWIW this is not about being right as its not worth the BS that comes with it. Really, its about not jumping to conclusions based on a bad experience, design, application, and ultimately safety. That said, I know countless owners have had issues. Every forum using this hub assembly and the FSM has a few where it didn't go as planed. I'm guessing not every WIN was recorded either so take DIY wrenching w/a grain of salt.

Point: my best guess is something is being missed, or not done proper (silicone, kerosene and chain lube come to mind {see chart under lube section}). Although it may be as simply as replacing the nut with a new one every time, or cleaning the metal shards from both parts. IDK...
The one thing I will stand firm on is this: engineers DO NOT USE STUDS TO STOP ROTATION of a disc they retain. The fastener on the stud applies CLAMPING FORCE! That clamp prevents rotation. Rely on the stud to prevent rotation and at the very least, you'll be walking at some point in time.

So, if someone is sold on 35 ft/lbs as the safe and correct value to tq the nuts too, - set yours to that value and ride for couple years. Report back what type of failure you had. Yes, I said years! They anticipate what 20,000 miles of service before the hardware is messed with??

Bottom line: Clean, dry, and as close to the spec in stages and most will be fine!
 

Kenfz6

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I have been able to unscrew the studs by locking the damaged stud in a bench vice and spin the carrier. I have found (temporary) studs at the auto supply, toyota exhaust manifold studs, in the self help section. The length needs to be cut down to clear the swingarm.

Ken
 

TownsendsFJR1300

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If you look at post #1, there are TWO STEEL STUDS with stripped threads. Thus, the steel nut and steel stud CANNOT take that high torque. You'll also notice its not stripped the full lenth, just to where it tightens to the sprocket

Also, to say that just the nuts are taking all the torque is NOT TRUE, the nuts are attached to the studs, the studs are holding the nuts(their obviously attached to the nuts and getting the same "PULL").

*To say the clamping force is the ONLY thing keeping the sprocket from spinning on the hub, is also flat wrong, ie;

Put that sprocket on the hub with NO NUTS (just for S&G's). Now, lets try and rotate the sprocket to the hub! It ain't going to happen!

Of course you need clamping force to keep the sprocket to the hub, how much, that's the bottom line. (To re-inforce this, just look at the picture in the first post, (at least two of the stud threads failed.).

For a 14mm bolt, below are te GENERAL torque values (Yamaha specifies dry) which specifies 61' lbs.

How many oil pans, with a larger bolt yet, finer threads, CRACK when torqued to 30 ft lbs?? This is per the FSM. Obviously too much torque. Per my FSM, posted above, the same drain bolt is 20 ft lbs.

I personally torque that drain plug to 12' lbs as well as the oil filter (K&P) (much sturdier being cast, finned aluminum). No issues BTW in over 3 years with this filter, 5 with the lower drain plug torque (which is basically good and snug).

When I replace my rear sprocket, I agree with John, 45 ft lbs is plenty and its not going anywhere.

As this won't be a sticky (although there's plenty of failures) and IMO, should be.

For others looking for info re the hub /sprocket install / torque, here are some some search words for this thread so they can decide on their own; hub, torque, stripped threads, rear sprocket torque, rear sprocket replacement, stripped studs, how to repair stripped studs, stripped hub.

Once again, the torque value has been beaten to death, opinions given and respected, and no ones feelings hurt, (just agree to disagree). Hopefully this thread will help others down the road. :thumbup:
 
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FinalImpact

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From the link provided...

The thing to keep in mind for an assembly like this is that the studs themselves do not transmit power between the sprocket and wheel hub. They just provide a clamping force between the two. The friction between the sprocket and wheel hub is what keeps the two parts from moving against each other.

If the studs were transmitting the engine's power to the wheels directly, they wouldn't last very long at all, as the sprocket would hammer against the studs every time you got on or off the throttle.

And in the end, it's your bike and you're responsible for deciding what is safe.

Fred


Also - do a little search on "sheared stud" <<== primary cause is almost always the lack of torque applied to clamp the sprocket with enough force to prevent rotation of the sprocket on the hub.

Bolts/studs can withstand far more stretch than they can shear. In fact they rely on stretch to maintain tension. Its when parts settle and tension is lost that friction is decreased and joints fail. As said, this isn't the kind of failure that happens over night. Its creeper and one day you'll look back and see the holes elongated and studs missing.

What I found alarming was the lube vs no lube change of 19ft/lbs. Add this and any damage from the removal process and your in trouble.

As Fred so kindly placed it, I will use his words: " in the end, it's your bike and you're responsible for deciding what is safe."​

Lastly - where is the case which "pulled the stud" from the hub carrier while torque to the nuts was applied?
 

dpaul007

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Funny this just came up. I'm doing my chain and sprockets this weekend. I'll be torquing the rear sprocket to 40-45 ft-lbs. I have enough other stuff to fix.
 

TownsendsFJR1300

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"Originally Posted by Fred

The thing to keep in mind for an assembly like this is that the studs themselves do not transmit power between the sprocket and wheel hub. They just provide a clamping force between the two. The friction between the sprocket and wheel hub is what keeps the two parts from moving against each other.

If the studs were transmitting the engine's power to the wheels directly, they wouldn't last very long at all, as the sprocket would hammer against the studs every time you got on or off the throttle.

And in the end, it's your bike and you're responsible for deciding what is safe.

Fred"

Who is Fred (from two years ago with the BMW and was selling his FZ?) and what are his credientials? Please show that.

No one is arguing the sprocket needs to be tight, its a matter of how tight.

You keep on ignoring points brought up, with no anwers. Ie the oil drain broken pan's torqued to 30' lbs (need documentation?). The copied the PDF for the exact same bolt, same material, same manufacturer, is 20' lbs.. The different torque spec's FROM YAMAHA. Please address that. Why is it different?..

Please also address WHY, the first post of this thread, in black and white,(SECOND request) there are CLEARLY, at least TWO STRIPPED STEEL STUDS?? Its right there in front of you but your ignoring it... SEE BELOW.




The closest stud and to the left are BOTH stripped, (can't see the furthest)
 
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FinalImpact

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I see the threads have been damaged where the nut came to torque. That DOES NOT MEAN it can't handle the torque. I asked, "what was the condition once the parts were removed", as that information is critical factor in why they failed. At this time we lack details... And I fear this one stacks up in details.

In short I'm saying there is more to this than meets the eye. So rather than throwing out an arbitrary ##, lets find some proof that either discounts the OEM spec or supports how a reduction is acceptable. IMO telling everyone to drop the tq value by 40% is a liability. The ISO chart says a common metric bolt of 10.9 or better can handle it. To me that implies the threads are compromised OR the process or final torque value are in excess!

FWIW: i'm planning on adding teeth to the rear so I'll verify my actions by doing what I wrote.

  • Clean, inspect, verify no damage.
  • Decide if components can be reused.
  • If so - reuse them!
  • From there, assemble, torque in criss cross pattern over three steps to final torque. Oh - Dry, no lube, no loctite, no anti-seize.

I have a Snap-On 1/2" drive Tq wrench that was calibrated about 4 years ago but hasn't done much but tq wheel studs. I also have 3/8" Snap-On clicker but I don't think it goes to 72 ft lbs.

So rather than throwing words back and forth lets bring some proof beyond the STANDARD ISO 898 CHART (which says its OK)!
I understand a sample of ONE is of little value, so my goal would be engineering evidence that supports the population base of millions hubs, that 72 ft lbs was the intended value AND IT WORKS WHEN DONE PROPERLY.

Does that seem reasonable?
 

Carlos840

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Not trying to add fuel to the fire here, but i recently changed my rear sprocket.

Before torquing the bolts i used brake cleaner to clean the studs and the nuts, checked the threads were clean and in good condition, got all the nuts finger tight (nothing applied to them).

I then torqued them to 50Nm in criss cross pattern, once all of them were done i went around a second time torquing them to 75Nm, then a third time at 100Nm.
I never once felt like something was about to give or that i was applying a large amount of torque, everything went smooth as can be.

Like Randy i can't help but wonder how many of these stripped bolts come from cross threading, or badly calibrated torque wrenches, or not using a criss cross pattern, or more importantly greasy threads or bolts, that result in a lot more torque being applied inadvertently.

Considering these nuts are in a place that will get pretty greasy it's not impossible that some people try to torque the nuts to a dry setting when they are actually lubed.
Just look at the carrier in the original post, it looks like it is covered in chain lube and crap, it's not impossible the threads were greasy and that caused them to strip.
 
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TownsendsFJR1300

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I did a search for the stripped aluminum hub itself and could not find any stripped HUB failures. My mistake there..

I did, while searching, find at least two dozen stripped studs(different posts), exactly the same as in this thead. ALL STRIPPED STUDS (same place) and issues removing them for replacement. One had a nut stuck/stripped to the stud (stud still locked in the hub). Is two dozen failures in several years a major problem? Perhaps not, but if it happened to me ONCE, its an issue that is preventable.

Cali riders, John, (as I recall) was back from 2009, so its got roughly 5 years at 45 ft lbs and apparently NO issues. There was also mention from an OP that his mechanic, never goes that tight but to about 45. (that thread is several years old too)

Just looking at the Yamaha general torque values listed below, for a 14mm bolt, the torque is 61'lbs

Anyone that has done any wrenching for any lenth of time, knows, for that size stud, is too much... The stripped part of the stud is NOT the entire stud, JUST where the nut tightens down. The threads above and below are fine, its NOT cross threaded.

Everyone that experianced this failure has NOT retorqued to the specified factory torque but a lower #.
I did not see anything (searched for about a half hour) re the lower torqued hub, having a later failure/loosening up, etc.

The nuts used on that hub (as you likely know) are very heavy duty and not likely to loosen up, even wth a torque of say 45.

Fortunatly, even thou we disagree on this issue, folks are reading this when looking for a torque value (for rear sprocket replacement) and hopefully deciding on their own, how far to tighten those nuts.

Just for S&G's, I have the service manual (PDF) for a Kawasaki KLR 600 and looked up the rear wheel sprocket, axle, etc. Yes, its no where near the HP of the FZ however, just for comparison, (and the axle is MUCH larger on the KLR than the FZ nut). One FZ sprocket nut torque is 72' lbs. The rear axle nut, again, much large,r is 69' lbs! You don't even want to look at the sprocket bolt torque for the KLR..

 
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greg

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I only torque my rear wheel up to about 90 or 100nM. Same with my car tyre nuts. No way I'd go that high on the sprocket carrier with it's much smaller stud size
 

AdamFZ

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The bike has covered 35k and is a 2005 model.

The studs were in a good condition but i don't know if it was over tightened by the previous owners.

I did exactly as the manual said for tightening.... criss cross pattern and i also did it in stages.

They got to 90nm and then while trying to get to 100nm they failed.

I've done the new ones up to 70nm.
 
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