Rear Sprocket Carrier | Failed Studs

TownsendsFJR1300

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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.

Tks for the update and claification.

Can you neasure the EXACT mm size of the old stud (where its NOT damaged, the threaded part). Its likely 14mm or 12mm. If you still have the old part. I tried measuring mine with the sprocket on, not enough room.. That would help pin down an acceptable torque value with some scientific method.. Thanks..


Note:

A 14mm bolt, per the Yamaha General torque values (see scale) is 85nm. Yours making it to 90nm is above that, but held, verifies your at the limit of the stud/nut. Its failing after / above that, just confirms the general torque value is safer than the recommended sprocket torque, which is just slightly too high and will occassionally fail..
 
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AdamFZ

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It's neither.

I just measured it with my vernier caliper and the outage diameter was 9.8mm and the inner (inside of the thread) was 9.2mm
 

TownsendsFJR1300

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It's neither.

I just measured it with my vernier caliper and the outage diameter was 9.8mm and the inner (inside of the thread) was 9.2mm

Thanks, its a big help.. 10mm it is.

Once again, checking the Yamaha general torque values for a 10mm is 22' lbs or 30 nm's.



I'm open as to why, from the above scale, the specified torque for the sprocket is over 3 times what is recommended for that stud/bolt??? Why is there such a large discrepancy??
 
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FinalImpact

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You have to keep in mind that the chart is for "General Purpose" and the quality of bolt used to say secure the side cover to the engine or the pod cover to the frame is a lower grade than those like the connecting rod or these studs in the hub.

Hence the words saying: use the written text on the topic vs that chart.

Speaking of charts here's another that has much more detail. Take a look. https://www.fastenal.com/content/feds/pdf/Torque-Tension Chart for Metric Fasteners.pdf

This is in ft/lbs, under DRY for 10mm bolt:
CLASS 10.9 = 53.2 ft/lbs for a clamp load of 8115 lbs
CLASS 12.9 = 62.2 ft/lbs for a clamp load of 9484 lbs


Much more conservative than the first chart found and they specified this: Clamp loads estimated as 75% of proof load for specified bolts. Meaning a standard bolt that meets that class still has some room to go.

So, does that mean yamaha has there own recipe for studs and nuts and if not, are they taking it to 90% or 100% or proof load? Also, I've seen this repeated SEVERAL TIMES; "using a torque wrench to set tension on a bolt introduces +/-30% error. For example compared to measuring stretch which is something like +/-5% error. Which further supports most fasteners not being used to their potential.
  • Hence the reason why engine assembly of Head bolts, Rod bolts, crankshaft main bolts have yield to torque bolts which often times ARE NOT MEANT TO BE REUSED. Most of those are torque'd to say 30 ft/lbs (example) and then turn them 90 degrees for one time use.

Also, if you have a pitch gauge it would be nice to know the actual pitch.
 

TownsendsFJR1300

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Makes some sense, however, we don't know the grade stud (likely high). In this application, bolt stretch cannot be measured for obvious reasons so we're resigned to standard torque values/ procedures

As you posted, even at the highest grade, a 10mm bolt, dry, per the chart is 62.2 ft lbs, (easier seen enlarged).

Re a torque wrench being off +/- 30% is an aweful wide variance and I don't know how (short of recalibration montly) most torque wrenches, unless seriously abused, will not be off that far. (Thats like setting for 60 and getting 90' lbs.. That is an extremly large jump) and frankly, IMO, not realistic..(but that's fine)

None the less, torquing that fastener to 72ft lbs is still above the chart, (even with a dead on, accurate TW). So is Yamaha pushing the accepted torque spec's OVER 100% above the standards, (62' lbs to 72'lbs)?

Hence taking that nut to an exact and accurate 72 ft lbs, with a brand new, just calibrated, Snap on wrench, (best case scenerio) you just OVER TORQUED that fastener pushing it to its limits (and somewhat beyond), and hence some failures with the threads?.

With the chart, your above post, assuming the bolt is a grade 12, seems to re-inforce that 62' lbs, with a dead on torque wrench would be the max.

Also, something not noted, these particular locking nuts, for a 10mm bolt stud, height wise(or thickness), are a bit shorter than a regular nut with less surface area ( and less threads). With that in mind, say 25% shorter, you now have 25% less thread, lowering the amount of torque accordingly, that fastener may handle...
 
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FinalImpact

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Scott,
There seems to be confusion with the intent of the "+/-30% error". My statement was not to say the measuring device had a 30% error. Its saying the average fastener tension has a error percentage of 30% when a tq is used to set tension on the fastener.
For a fastener to work it has to stretch (that stud has to stretch), thus the question is "how much does it stretch?" Just like you said its not practical and we don't know as the method to determine is too complicated.

But the only way to know fastener tension is to determine force applied or fastener stretch. That's why I said, fastener stretch has 5% error while a torque wrench method (not actual tq applied) has a 30% error. Meaning rotation friction (break away friction) can cause the clamp load error of up to 30%. Just like different platings, lube, dry, and contaminants can alter what the tq wrench acts on....

ALSO - you must keep in mind that some manufactures will (our company does) spec different components with greater yield strength than the "normal standard". It is common practice and the main reason why off the shelf parts can not be substitute as they DO NOT meet the manufactures standard. Like I said early, they have they're own recipe but we don't know what it is and are just guessing with no facts...

EVEN MORE DETAIL: http://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf

More fasteners: Proof Loads for Fasteners | Fuller Metric Parts Ltd.
Has both 1.25 and 1.5 proof strength, as well as the nuts. As stated it means little though as we don't know what yamaha used.
 
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TownsendsFJR1300

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I've seen either this product or a similar product as this on the "Powerblock" (when still on TV) for engine assembly;

[ame="http://www.amazon.com/ARP-100-9910-Torque-Assembly-Lubricant/dp/B004XJRFCK"]Amazon.com: ARP 100-9910 Ultra Torque Assembly Lubricant - 10 oz. Brush Top Container: Automotive[/ame]

I know Yamaha spec's their bolts being dry when tightened, however would this product give a more accurate reading?

Or would the actual #'s be higher as its helping to eliminate surface to surface friction, etc?
 
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FinalImpact

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I've seen either this product or a similar product as this on the "Powerblock" (when still on TV) for engine assembly;

Amazon.com: ARP 100-9910 Ultra Torque Assembly Lubricant - 10 oz. Brush Top Container: Automotive

I know Yamaha spec's their bolts being dry when tightened, however would this product give a more accurate reading?

Or would the actual #'s be higher as its helping to eliminate surface to surface friction, etc?

I think you would be even more likely to pull threads. Notice the nut has a built in washer. I know that Cerclip lock embedded in the nuts is very had on the stud. I've seen them used before and I'm very suspect of them causing damage on the way off.

IMO - during removal some lube (engine oil etc), should be applied to ease the bite of the lock nut. Then remove the nuts, clean them and the studs repeatedly and prepare all points for install.

This washer....
attachment.php
 

TownsendsFJR1300

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So rather than throwing words back and forth lets bring some proof beyond the STANDARD ISO 898 CHART (which says its OK)!

Just as an FYI, I did a quick search on the R6, R1, FZ, etc and found NUMEROUS failures of the hub studs, ie too tight per spec. Its not apparently related to just the FZ;

Stripped stud on rear wheel hub?

Rear Sprocket Studs - Wheel Hub ?? : Yamaha R1 Forum

99 R6 Rear Axle Torque Spec (108ft lbs, is this right???) : Yamaha R6 : R6 Forum

Rear Sprocket Bolt Trouble : Yamaha R6 : R6 Forum

http://www.600riders.com/forum/fz6-technical/12290-rear-sprocket-nut-problem.html
 
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Motogiro

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There are other Japanese bikes that seem to have this same torque specification discrepancy with similar outcome.

Here's a simple and handy tool to have to remove stubborn or damaged studs.

kd1708.jpg
 
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