Titanium engine bolts- Less vibration? More flex?

Joko
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Joko
Considering replacing the steel engine mounting bolts on my KX500 with titanium, not so much for weight reduction, but thinking that it may reduce engine vibrations and provide more chassis flex considering modulus of elasticity is half that of steel, hence less stiff and more flexible. Thoughts or actual experience? Thanks…
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Gravel
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Gravel 12/7/2021 6:04pm
12/7/2021 6:04pm
When I was racing KX500s the trick was to find bolts that were just barely too big to fit in the holes and drill them out to fit snugly. Use the highest grade bolts possible, then torque the crap out of them. Cut vibration noticeably and the motor mounts and the rest of the bolts didn’t come loose nearly as often. Also use blue locktite on everything.

I wouldn’t think more flexibility would help..
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SilverSpurs
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SilverSpurs 12/7/2021 7:22pm
12/7/2021 7:22pm
∆ Precision fit steel bolts and shim any frame to engine lug gaps and clearance any squeeze fit mount points.
Use flanged head bolts and nuts.
Fanatics sometimes sleeve engine mount lug holes and make push fit top hat washers to re-do worn frame brackets and drill for bolts as an assembly. Long series drills usually required.
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spimx
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spimx 12/7/2021 9:01pm
12/7/2021 9:01pm
If you want to use ti use ti. They will never corrode or rust and they weight less. I have ti motor mounts and I don't notice any difference but they look cooler.
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RussB
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RussB 12/8/2021 12:05am
12/8/2021 12:05am
I've replaced engine mount bolts with titanium on both a steel framed RM250 and Ally RMZ450... didnt notice a difference flex wise on each frame. Did look cooler and saved weight though

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seth505
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seth505 12/8/2021 8:35am
12/8/2021 8:35am Edited Date/Time 12/8/2021 11:14am
I'm currently trying this on my RMZ rather than drilling/changing the mounts themselves. So far so good but I can't measure an actual improvement at the moment. I put Ti in my front and upper rear engine mounts and used less torque than specified in the manual.

*edit* I switched out a bunch of fasterners to Ti to just look better and save a pound or two. My chassis is known to be "overly stiff" so I wondered if there were any other advantages to be had which as I said is doubtful, I can't measure any improvement.
Falcon
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Falcon 12/8/2021 8:45am
12/8/2021 8:45am
Wait... isn't titanium less flexible than steel? I thought that was one of the negatives, even though it is lighter.
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seth505
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seth505 12/8/2021 9:15am
12/8/2021 9:15am Edited Date/Time 12/8/2021 11:16am
Falcon wrote:
Wait... isn't titanium less flexible than steel? I thought that was one of the negatives, even though it is lighter.
Young's modulus (elasticity) of Ti is about half of carbon steel and stainless steels. Basically, this means it'll deform/stretch more than steels.

*edit again* I assume the downvote is for saying the Ti bolt will act like gumby compared to steel. I am not saying that at all. It was a general response, not saying in the application of a bolt it will deform and have the engine bounce around.
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Luxon MX
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Luxon MX 12/8/2021 9:58am
12/8/2021 9:58am Edited Date/Time 12/8/2021 9:59am
If the bolts are properly torqued (tensioned really), it won't make a difference whether they're made of steel or titanium, they'll feel exactly the same.

You won't hear this from people trying to sell you titanium bolts or other chassis mods, though...
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Grouper
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Grouper 12/8/2021 10:34am
12/8/2021 10:34am
What Luxon said, plus, it is a misnomer that bolts hold things in place. Bolts tighten joints, friction holds them in place (largely). There's even more to this, but short story, just don't waste the money lol.
SilverSpurs
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SilverSpurs 12/8/2021 10:36am
12/8/2021 10:36am
Falcon wrote:
Wait... isn't titanium less flexible than steel? I thought that was one of the negatives, even though it is lighter.
Ti is more flexible than steel, about twice as much but has similar strength in our motorcycle applications.

If you tighten your bolts by torque to the same amount a steel and a Ti bolt will have the same clamp load on the joint- but the Ti bolt will have elongated twice as much as the steel bolt.
Falcon
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Falcon 12/8/2021 11:10am
12/8/2021 11:10am
Falcon wrote:
Wait... isn't titanium less flexible than steel? I thought that was one of the negatives, even though it is lighter.
SilverSpurs wrote:
Ti is more flexible than steel, about twice as much but has similar strength in our motorcycle applications. If you tighten your bolts by torque to...
Ti is more flexible than steel, about twice as much but has similar strength in our motorcycle applications.

If you tighten your bolts by torque to the same amount a steel and a Ti bolt will have the same clamp load on the joint- but the Ti bolt will have elongated twice as much as the steel bolt.
I stand corrected. Thanks, Seth and SilverSpurs.

Ti is more brittle than steel, though - right?
Bruce372
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Bruce372 12/8/2021 2:46pm
12/8/2021 2:46pm Edited Date/Time 12/8/2021 2:46pm
Does anyone know why 200HP Ducati with a single side swing arm can do 200mph in a straight line, but a vet novice can feel a ktm with a integrated rear axle and chain adjuster going sideways?
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SilverSpurs
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SilverSpurs 12/8/2021 11:00pm
12/8/2021 11:00pm
Falcon wrote:
I stand corrected. Thanks, Seth and SilverSpurs.

Ti is more brittle than steel, though - right?
Depends on the grade and often the details of the heat treatment and hardness.

Ti is very tough though not as tough as the sort of steel an axle shaft or a good suspension bolt or engine stud is made from.

If it wasn't 50 times the price and harder to process just about everything steel on your bike would be made from Ti.


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