Ducati.ms - The Ultimate Ducati Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!

1 - 20 of 53 Posts

·
Registered
Joined
·
87 Posts
Discussion Starter #1
I saw some speculation on another website by a respected Ducati mechanic that his 900SS frame cracks (the usual place) might have been caused, or hastened, by his installation of Nichols engine mount bolts.

I've also seen on this forum people say that it actually should help prevent frame cracks.

Since I've got 25,000 crack-free miles on my frame and am considering getting some Nichols bolts, I'm wondering if there is anyone out there with experience or opinions one way or the other on this subject?

Thanks!
 

·
Registered
Joined
·
2,434 Posts
My opinion is that if the frame cracks after you install the bolts, then it would have eventually cracked anyway. It's kind of impossible to do a controlled experiment about this since you'd have to have a whole bunch of Supersports of various years with and without the Nichols bolts to get a statistical sampling of whether or not they caused the cracks. Anything else is pure conjecture :think:. I suggest you install the bolts (I hear a lot of good reports about them) and if your frame cracks, get it welded.
Joe
 

·
Chilehead
Joined
·
6,984 Posts
Isn't the whole point of installing them to AVOID frame cracks?

I've got 30k Miles on my ST2 with them, no problem.

Tom
 

·
Registered
Joined
·
1,263 Posts
Frames without the bolts crack. In light of this, saying the bolts cause the cracks seems, um, not brilliant to me, but I haven't seen the original post so can't comment specifically on what the mechanic said.

We do durability testing at work all the time. The test cycle is developed from shock loads the component sees in use. The front of the frame sees shock loads from the front suspension, not the engine. I'd be willing to bet improving the forks will do more to prevent cracks than engine bolts will...
 

·
Premium Member
Joined
·
748 Posts
I just posted some questions about the Nichols bolts a couple of days ago, and was just wondering the very same thing. As I understand it, the bolts tighten up any looseness between the frame and engine that might be causing the frame to flex. I'd be curious to hear from any mechanical engineers on this.

Does the frame flex caused by the movement of the engine in the frame with the stock bolts cause greater stress on the other critical points of the frame (steering head)??

or

Does eliminating the movement of the engine in the frame with the Nichols bolts lead to those forces being transferred to the other critical points points in the frame??

As previously posted, some frames seem to crack regardless, so I doubt you can point to any direct relationship. I'm pretty sure Nichols makes steering head reinforcement gussets, so it makes sense for anyone concerned enough with the handling of the bike to upgrade to the Nichols frame bolts to just go ahead and reinforce the frame while they're at it.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #7 (Edited)
im curious, what was the reasoning that the Nichols bolts caused the frame to crack ?
Yeah, kinda what josephvman said. If there is flex in 2 different areas of the system (the 2 known weak points of the system in this case), then stiffening one so that it doesn't flex anymore transfers the load to the area that wasn't stiffened, inducing more stress on it. That's the theory under question anyway.

I've heard 2 other examples of this. Regarding rider gear, wearing boots that stiffen and protect the ankle joint just transfers injuries to the knee.

Also, I've been a mechanic on the H-60 helicopter in the Coast Guard for 13 years and when the Coast Guard's H-60's got to about 4000 flight hours, they started getting all kinds of serious cracks in major structural beams. They had reinforcing kits installed, along with new beams, and some mechanics believe that this is just causing cracks to start appearing in other areas.

I'm leaning towards getting the Nichols bolt (the other one has already been replaced with Speedymoto's frame slider system). I just thought it would be an interesting topic to discuss and I was curious what the collective feeling of this forum would be on the matter. For all I knew it had already been discussed, although I couldn't find it by searching.

By the way, I can also see the other point, that having the engine to frame joint "loose" allows the system to "load up" and then transmit the shock extra hard on the steering head.
 

·
Registered
Joined
·
1,284 Posts
The Nichols bolts reduce flex by virtue of being slightly larger in diameter so the fit in the case is tighter and the surface area engaged by the nuts is larger allowing more clamping force on a larger area.Plus the steel used is a higher quality and much stronger.It is very unlikely the stronger joint created at the engine cases would contribute to cracking at a relatively unsupported area of the frame.If you look at the earlier F1 and the superbike frames you will see a cross bar between the top rails right where the tubes bend in to go to the steering head.On the SS's this tube was eliminated to make room for the airbox required mostly I think to meet the noise regulations.The lack of this crossbrace allows the top of the frame to flex side to side and that will contribute to the cracking at the steering head area.Welding a brace in this area really sharpens the steering response when the bike is ridden hard but it does require elimination or modification of the airbox.Then the Nichols bolts would be the icing on the cake.
 

·
Registered
Joined
·
322 Posts
in 98 ducati added an extra brace to the FE frame. where?
 

·
Registered
Joined
·
87 Posts
Discussion Starter #10
If you look at the earlier F1 and the superbike frames you will see a cross bar between the top rails right where the tubes bend in to go to the steering head.On the SS's this tube was eliminated to make room for the airbox required mostly I think to meet the noise regulations.The lack of this crossbrace allows the top of the frame to flex side to side and that will contribute to the cracking at the steering head area.Welding a brace in this area really sharpens the steering response when the bike is ridden hard but it does require elimination or modification of the airbox.Then the Nichols bolts would be the icing on the cake.
Very interesting. I did not know that.

That's why I started this thread - to learn stuff like that!
 

·
A&S Ducati
Joined
·
96 Posts
One more data point to chart. I've got 25k+ miles with Nichols motor mount bolts on a '98 CR. No problems.
 

·
Registered
Joined
·
3,448 Posts
Also, I've been a mechanic on the H-60 helicopter in the Coast Guard for 13 years and when the Coast Guard's H-60's got to about 4000 flight hours, they started getting all kinds of serious cracks in major structural beams. They had reinforcing kits installed, along with new beams, and some mechanics believe that this is just causing cracks to start appearing in other areas.
A buddy of mine, who I went to Clemson University with, went on to get his doctorate's in mechanical engineering and was working on this project as a civilian consultant a few years ago. Since he had all sorts of top-level security and had to keep quiet about his activities, that's all I know about it: that he was working on it. I thought it was pretty cool, though.
 

·
Registered
Joined
·
322 Posts
These F.E. frame pics I found might show the extra brace. I am not sure what to look for as I haven't seen the earlier frames.
i wonder if they added that diagonal brace across the horizontal cylinder?
 

·
Registered
Joined
·
116 Posts
41K miles on my '95 SS - no issue with the Nichols MFG engine bolts.
On another note, I did pull one of the engine case threads of the vert cyl using Nichols cylinder bolts. Those were installed after the one of the OEM bolts had snapped which was known to be a common problem at the time. What to make of that? Torqued too much? Overheating cylinder? Worn tap at time of mfg? Not enough flex in the bolt? We'll never know. 20K+ miles later no issue, so far so good...
 

·
Registered
Joined
·
818 Posts
Only if you fuck up the installation.

And, re: the rest of your post, the frame cracks that are prevalent on older SS models is at the headstock, not the frame bolts.

ergo, the frame bolts have absolutely nothing to do with it.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #17
i wonder if they added that diagonal brace across the horizontal cylinder?
Nope, my both my 95 and 96 have that. In fact, I don't see any differences between the one pictured and my 2 frames, and I've been pretty intimate with both of them in the past few days as I just pulled the motors out of both of them this week and was just doing some extensive cleaning on the front half of the 96 frame this morning.

Man, those welds are ugly!
 

·
Registered
Joined
·
87 Posts
Discussion Starter #18
These F.E. frame pics I found might show the extra brace. I am not sure what to look for as I haven't seen the earlier frames.
There is something mine don't have transversely above the shock. Looks like something to mount something to with 3 screw holes in it. Doesn't look structural though and would be in the wrong place for it I would think.
 

·
Registered
Joined
·
1,263 Posts
There is something mine don't have transversely above the shock. Looks like something to mount something to with 3 screw holes in it. Doesn't look structural though and would be in the wrong place for it I would think.

That's where you attach the gas tank.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #20
Oh yeah. Duh! Guess I didn't recognize it without the hinge piece.

Now, I get to wait for SFYamR1 to call me an idiot . . .
 
1 - 20 of 53 Posts
Top