Ducati bolts...

[darthmoto]

Why is it that ducati bolt heads shear off so easily? 

First, I tighten one of my clutch pressure plate springs in too tight. Not even wrench-the-make the beast with two backser-down-and-jump-on-the-breakerbar tight. A bolt head seperates clean. Now I Im bolting my front tooth sprocket retainer on, and as I turn.. Its getting close, getting tighter, when is this bolt gonna stop turning, oh shit its starting to loossennnnFFFAHHCK!!! Another bolt head comes right off! Seriously- is this ducati's way to insure against stripped threads or something?? The bolt is so soft that there's hardly indication that its done and it wont go further... Are these made of lead or something? Or fancy ducati unobtanium? 

Sigh..... gotta get that piece of bolt out before the locktight hardens.

Not happy 

[Drjones]

There is no such thing as a "Ducati" bolt as most of what Ducati puts on their bikes is bought from third party vendors.  18-8 SST is normal for just about all general use bolts sold worldwide and yes it is a soft material.

Torque wrench.  Buy one and use it well.  It doesn't matter if the bolt is on a Honda, Harley, BMW, or Schwinn bicycle if you exceed the bolts yield strength you'll shear the head off.

[darthmoto]

I realize that they arent "Ducati" bolts. 

Amidst my extreme frustration with 5lb/sq in. torque spec'd bolts on of all things A SPROCKET, I called it a Ducati bolt. Because these bolts are what Ducati uses. Yes, I should be more religious in using a torque wrench on even the simpler things like sprocket retainer clips.

[ducatiz]

You can get a bum bolt.  It happens.  Shouldn't, but it does.

18-8 SST is normal for just about all general use bolts sold worldwide and yes it is a soft material.

18-8 is not a metric designation, that's stainless inch and probably there aren't any inch bolts on a Ducati..  Metric stainless comes in A2-x, A4-x, etc.  Most common is A2 and it is crap.  There isn't any A2 fasteners on a Ducati.  Period.  Ducati doesn't use stainless on any of the engine, brakes or ?.  Maybe on the gauges, but nothing structural at all.

Rotor and engine bolts on Ducatis are 10.9 steel with zinc chromate coating.  Stainless A4-80 is approximately as strong, but if you can find 12.9 with good coatings and it is the best.  A4-90 is available but rare.  Actually, I think the clutch spring retainers are 8.8, but I would have to look.  It's been a while.  Whenever I have to replace stuff, I always get coated 10.9 or better (mdmetric is a good source).  I never bother with stainless.

If you are anal and crazy, you can get 12.9 alloy with various kinds of coatings to resist corrosion and chemicals.  I bought a box of 12.9 coated button-head 8x20s for rotors.  it was a deal..

[darthmoto]

Thats great info. I'll make sure to source some steel bolts with 10.9 or higher designation for any of these future "mishaps".. Call me extremely crude, but I just replaced my clutch spring retainers with 6x16mm HD. HD stands for 'Home Depot'    They seem to be much tougher than the bolts I replaced.. Seem to work fine, I guess? I figured corrosion wouldn't be a problem since its always submerged in oil..

You can get a bum bolt.  It happens.  Shouldn't, but it does.

18-8 is not a metric designation, that's stainless inch and probably there aren't any inch bolts on a Ducati..  Metric stainless comes in A2-x, A4-x, etc.  Most common is A2 and it is crap.  There isn't any A2 fasteners on a Ducati.  Period.  Ducati doesn't use stainless on any of the engine, brakes or ?.  Maybe on the gauges, but nothing structural at all.

Rotor and engine bolts on Ducatis are 10.9 steel with zinc chromate coating.  Stainless A4-80 is approximately as strong, but if you can find 12.9 with good coatings and it is the best.  A4-90 is available but rare.  Actually, I think the clutch spring retainers are 8.8, but I would have to look.  It's been a while.  Whenever I have to replace stuff, I always get coated 10.9 or better (mdmetric is a good source).  I never bother with stainless.

If you are anal and crazy, you can get 12.9 alloy with various kinds of coatings to resist corrosion and chemicals.  I bought a box of 12.9 coated button-head 8x20s for rotors.  it was a deal..

[ducatiz]

IMHO the best coating is Dacromet, but it is a proprietary process and fairly expensive.  Impervious to corrosion, acid, etc.. Something like 100000000 duty hours of salt spray, it is freaking unreal.

[He Man]

for the majority of stuff on the bike, stainless is okay. its not going to be torqued to an insane number, and the point is to just prevent the 2 metals from fusing. Thought stainless is pretty soft, you shouldnt snap it from torque it down....nt unless your over torqueing it to begin with or your using super strong locktite.

[koko64]

Back in the day when I was young and strong (State weight lifting champion), I had my first 'big' bike, a Truimph Bonneville, not known for strong alloys. I was like "Duh.. I broke another one". I really had to make a concious effort to take it easy and use a torque wrench. That old Bonneville was covered in helicoils! . A mechanic friend told me to use just finger strength on small bolts if there was no torque value available!

Now I'm old and frail (and use a torque wrench on clean, greased bolts) I don't have that problem.

A good friend of mine was a monster of a guy and used to break off door handles, car gear sticks, etc and was always having to apololgise for breaking stuff, such was his hand strength (and lack of 'touch'). Some people have great, natural hand strength and need to back it off a notch.

I remember being livid every time I broke a bolt or stripped a thread. I can laugh about it now over a beer.

Take it easy tiger!

[suzyj]

A big part of doing mechanical things is learning what different torques feels like, and knowing what the appropriate torque is for different sized fasteners.

I have a set of T-handle allen key drivers that I use on my bike - their relatively short handles combined with my relative lack of hand strength ensures that I get an appropriate torque on most-all allen headed bolts.  An exception is 8mm stuff for suspension linkages etc, where I often use a short lever for extra torque.  The length of most of my combination spanners is also appropriate to provide an acceptable amount of torque.

It's only very special bolts (rotor bolts, head nuts, etc) that need special attention.  For those, break out the torque wrench.

[koko64]

A big part of doing mechanical things is learning what different torques feels like, and knowing what the appropriate torque is for different sized fasteners.

I have a set of T-handle allen key drivers that I use on my bike - their relatively short handles combined with my relative lack of hand strength ensures that I get an appropriate torque on most-all allen headed bolts.  An exception is 8mm stuff for suspension linkages etc, where I often use a short lever for extra torque.  The length of most of my combination spanners is also appropriate to provide an acceptable amount of torque.

It's only very special bolts (rotor bolts, head nuts, etc) that need special attention.  For those, break out the torque wrench.

+1
The feel or touch for a sense of torque.

[RAT900]

The other thing to consider is the design of the assembly you are working on.

For instance the pinion gear retaining plate actually sees very little stress despite its locale

its job is to prevent lateral movement of the gear on the spline shaft...the majority of the stress is between the splines on the shaft and the gear

and none of those really translate to anything meaningful in the way of energy to the retaining plate bolts

[ducpainter]

Another consideration is the quality of the part being installed.

The aftermarket sprocket I put on my 900 had terrible threads for those screws.

If I hadn't been paying attention I could have broken a screw easily.

[koko64]

Yeah, it's all true.
I've had some crap bolts give up in my time, including engine studs.

[scott_araujo]

I still kinda prefer the head shearing off to stripping the threads on a piece of the bike.  When I'm tightening something and feel it start to give way I pray it's the bolt a and not the aluminum threads on the hole it's in.  I can extract a stud pretty easily, even better now that the Duc has given me so much practice   But yeah, it always leads to a round of cursing, and then a second one when I have to get out the Dremel and cut down the new bolt I bought since they didn't have exactly the length I wanted.

Scott