case cracking and aftermarket bolts

[rhubarbray]

I`m thinking of getting the TPO engine bolts for my ST2 but I had a couple of questions to put out there.
It appears the OEM bolts are necked down in the shank area. If I put in bolts which are not waisted and are are of a stronger material to start with,...would that not put an even greater compressive stress on the cases when the engine is up to operating temp?

Or would I be better off ensuring the OEM bolts are properly torqued say, once a year at the spring unwrapping?

Of the cracked cases we do know of, how many had the stronger bolts?

Ray

[va duc]

From what I have seen they are all susceptible to cracking if not kept at proper torque. I was of the opinion that once they went to the 12mm bolts the problem was non existent. Recently that appears to be suspect. As my machine had the 10mm bolts I upgraded to the 10mm Nichols and re-torque and apply lock tight yearly as per installation instructions. 5,000 miles this year and the bolts were at specified torque when checked. I still cleaned the threads and re-torqued to be on the safe side and will continue to do so yearly.
YMMV.

[tonered]

Making an educated guess, I'd say that the cases are happier when they are tight in the frame. I believe there are examples where failed bolts cause cracked cases. Your 2002 ST2 should have 12mm bolts to start with, similar to my 2001. I just check mine every 6k service and now keep a routine eye on the rear of the case near the mount.

All ST3 should have had the 12mm bolts. Although, they supposedly use a different crankcase than the early STs.

When you check yours, does the nut turn at all? Mine never has.

Have a good one.

[strider3]

Originally Posted by va duc

From what I have seen they are all susceptible to cracking if not kept at proper torque. I was of the opinion that once they went to the 12mm bolts the problem was non existent. Recently that appears to be suspect. As my machine had the 10mm bolts I upgraded to the 10mm Nichols and re-torque and apply lock tight yearly as per installation instructions. 5,000 miles this year and the bolts were at specified torque when checked. I still cleaned the threads and re-torqued to be on the safe side and will continue to do so yearly.
YMMV.

When I got my 2004 ST3 3 years ago the first mod I did was to install Nichols engine bolts based upon the recommendation of a shop tech. He said that the factory bolts moved a bit in the casting and could cause cracking. He stated that he had seen several STxs have this problem and that the repair is expensive. The second mod he also recommended was the DT case guard. They both went in at the same time within days of buying my bike. These went in even before I addressed the slipping clutch.

I too check the torque annually or whenever I think about it. The bolt stares right at me when the bike is on the lift as you cannot put a cap on these aftermarket bolts. Kind of yells at you to check it.

[stryder]

Originally Posted by rhubarbray

I`m thinking of getting the TPO engine bolts for my ST2 but I had a couple of questions to put out there.
It appears the OEM bolts are necked down in the shank area. If I put in bolts which are not waisted and are are of a stronger material to start with,...would that not put an even greater compressive stress on the cases when the engine is up to operating temp?

Or would I be better off ensuring the OEM bolts are properly torqued say, once a year at the spring unwrapping?

Of the cracked cases we do know of, how many had the stronger bolts?

Ray

The amount of compression is based on the torque applied on the nut, not the material of the bolt. The straight through shape of the aftermarket bolts *may* allow less up-down/shear movement if the nut backs off, which would be a good thing IMO. The aluminum will always expand more than the steel bolt IMO re expansion concerns.

Checking the torque on the nut annually is good PM. We have posts in other threads that state some feel the bolt stretches over time. If so, then they *may* have a service life and *perhaps* should be replaced at certain intervals. I've never had to torque mine down in 6 seasons, but am thinking of replacing them to aftermarket ones anyway since they seem so much stronger, and I'll be approaching 30+K miles next season. Some have looked at the mileage of failed cases and it *seems* the average is approx 35Kmiles. There *may* be a relationship between failed cases, and "used" bolts. YMMV.

There's a member who stated he may try organising a TPO group buy, so you may want to hold off on that order a little longer.

[C-simian]

Stryder,

Thanks for reminding everyone that I'm trying to get a group discount - still trying to put it all together (the fact that my nearby Ducati dealers went out of business hasn't helped) but I expect to be able to present figures to people at the end of next week.

Ron

[rhubarbray]

Originally Posted by stryder

The amount of compression is based on the torque applied on the nut, not the material of the bolt. The straight through shape of the aftermarket bolts *may* allow less up-down/shear movement if the nut backs off, which would be a good thing IMO. The aluminum will always expand more than the steel bolt IMO re expansion concerns.

Checking the torque on the nut annually is good PM. We have posts in other threads that state some feel the bolt stretches over time. If so, then they *may* have a service life and *perhaps* should be replaced at certain intervals. I've never had to torque mine down in 6 seasons, but am thinking of replacing them to aftermarket ones anyway since they seem so much stronger, and I'll be approaching 30+K miles next season. Some have looked at the mileage of failed cases and it *seems* the average is approx 35Kmiles. There *may* be a relationship between failed cases, and "used" bolts. YMMV.

There's a member who stated he may try organising a TPO group buy, so you may want to hold off on that order a little longer.

While I agree with the initial torque statement, what happens when the cases heat up? The coefficient of expansion of aluminum being quite a bit more than steel would put more tension on the TPO bolt as it will resist the expansion while the stock one may stretch just a little bit and then return to normal when cooled down. Another example I`ve seen would be many of the inline four cylinder air cooled cylinder studs. Every one that I can recall have waisted bolts.

And thanks for the reminder for the group buy, but if I recall it`s for the titanium bolts. I didn`t need the Ti ones and they`re nearly twice the price of the steel ones right now. I just put on a NOS rear trunk mount and trunk.

thanks,
Ray

[C-simian]

Originally Posted by rhubarbray

And thanks for the reminder for the group buy, but if I recall it`s for the titanium bolts. I didn`t need the Ti ones and they`re nearly twice the price of the steel ones right now.
thanks,
Ray

Ray, the steel bolts are no longer available from TPO. I verified that with Allan last month, when I inquired about them. His reply, "We have discontinued the hardened steel studs that would fit your ST4. The steel studs were much less popular than the Titanium version, and we simply were not selling enough of them to justify ongoing production."

Some have looked at the webpage from the old catalog that lists the hardened steel bolts at around $90, but that catalog is not current and (apparently) there are no more hardened steel bolts for sale for our bikes. Allan indicated that he still has them for the 848/1098/1198 series, but those don't fit ours.

I'm not an engineer, but from what I understand the expansion coefficients of titanium alloys is a bit closer to aluminum alloys, but still not the same: Expansion Rates of some Materials. The titanium bolts have been employed successfully in racing, but that is a different environment than long-term use in our Ducatis, so I'm not in a position to comment on their longevity.

Hope this clarifies things.

Ron

[stryder]

Originally Posted by rhubarbray

While I agree with the initial torque statement, what happens when the cases heat up? The coefficient of expansion of aluminum being quite a bit more than steel would put more tension on the TPO bolt as it will resist the expansion while the stock one may stretch just a little bit and then return to normal when cooled down. Another example I`ve seen would be many of the inline four cylinder air cooled cylinder studs. Every one that I can recall have waisted bolts.

And thanks for the reminder for the group buy, but if I recall it`s for the titanium bolts. I didn`t need the Ti ones and they`re nearly twice the price of the steel ones right now. I just put on a NOS rear trunk mount and trunk.

thanks,
Ray

Well, I must say that I too wondered why Ducati's OEM bolt was waisted as opposed to the aftermarket variety. I don't think it has much to do with expansion concerns, and more to do with shear forces, and price point.

I think the OEM's waisted bolts might be designed to handle shear forces by flexing somewhat using a lower quality, less expensive part, as opposed to the higher strength steel/Ti of the ridiculously priced aftermarket bolts, ie if the less costly OEM material wasn't waisted, it would crack/break under the forces at that point if not allowed to flex somewhat.

You can always just replace your bolts with OEM parts if you have concerns. I may do that if the price isn't right with aftermarket ones. IIRC, the TPO site mentions their bolts are used for racing applications without failure. I imagine the bolt is exposed to more shear forces than expansion forces in racing appplications, and therein is their value IMO.

Maybe an engineer/metalurgist might chime in and enlighten us.

[erikrichard]

Ducati should have used more that 2 mounting points for the engine. I wonder if its possible to add a mounting point at the bottom of the engine..