Why no titanium forks?
 

Maybe a crazy question but why don't you ever see titanium forks? Titanium is supposted to be lighter and more forgiving than steel. There are hundreds, maybe thousands, of steel bikes with steel forks.

Tim

Actually, planet-x/on-one make a Ti fork for mountain bikes.

I think the accepted wisdom is that Ti is too flexy as a fork material.

Check out Morati and Sibex for starters. TiCycles also offers a titanium fork. Note that the prices on these forks can run pretty high... more than twice the cost of a CF fork.

MRC used to make a nice carbon fibre reinforced titanium MTB fork. That was a sweet fork.

http://www.singlespeed.net/images/ar...s/DSCN0038.JPG

AXCD used to make a Ti MTB fork too as did IRD.

Isn't the accepted wisdom that steel is flexier still than titanium?

I can't help wondering why titanium forks aren't popular on road bikes as well.

I betcha the cost-weight ratio of a Ti fork is what makes it unattractive for use as a fork. Ti is heavier than aluminum, and you only get away with making it lighter by using less of it. I think you can make a CF fork lighter and cheaper than a Ti fork, and since people are weight weenies, the CF fork is what the market gravitates toward.

Mostly economics...not only raw material but manufacturing costs. CF hits the sweet spot for weight, flex, strength and cost. Ti is available as noted by the examples above but typically at higher cost. As to stiffness...have to be careful about considering any material properties in isolation. It comes down to stiffness relative to section or mass. Steel has twice the modulus of elasticity that Ti has or is twice as stiff. But thinning steel out to make it comparable to the weight of Ti or at least close to it...stiffness relative to section really goes up for Ti. Same for Al which is regarded as typically stiffer then Steel but from a material standpoint the opposite is true. Al has 1/3 the modulus of elasticity that steel does. In summary it comes down to a balance between modulus of elasticity versus yield strength....objective being to develop as light a product as possible that will not permanently deform (yield strength). Overall stiffness or elasticity is as much a function of resultant wall section as it is modulus of elasticity.
George

Yup, multiple factors at stake. Ti weighs about 1/2 of steel, yet is 1/2 as stiff. Alloy is 1/3rd of steel and 1/3rd as stiff. So typically when you end up designing parts from steel, titanium and aluminium to be of similar stiffness, you end up with similar weights. This is a stiffness-to-weight measurement and they're all about the same.

Strength is a completely different matter and you can use stiffness-to-strength as a measurement metric. Depending upon the alloy, ti may or may not be as stiff as steel for the same strength, same with aluminium.

Ken Carpenter, a super-burly track racer from the '80s through '90s was always complaining about whippy wet-noodle bikes. He had a custom titanium track bike built with ti forks. They used thick oversized tubing everywhere and he was finally satisfied and declared, "Now that's stiff!" after a test ride. Of course, the bike was not significantly lighter or heavier than a similary-stiff steel or aluminium bike.

Due to the military usages of titanium, costs tends to be high due to mil-spec testing and manufacturing specifications. It's come down tremendously over teh past decade due to many military-contractors making products for the private-sector. But Ti is still much more costly of a material than either steel or alloy to use. So another measurement we can come up with is perhaps stiffness-to-cost ratio or strength-to-cost.

Only with a material with higher modulus and strength than steel can you make something stiffer, stronger, and lighter. This brings up another measurement of stiffness-to-strength-to-cost ratio (not sure how to plot 4D graph)...

Here's summary of materials properties that I came up for some other discussion:

http://i42.photobucket.com/albums/e3...Comparison.gif

This hasn't even touched upon the design of the structures. Which has a bigger impact on the strength & stuffness of a shape than the materials used. If you want a light stiff fork, you can make one out of 1" tubing in either steel, titanium or aluminium and it'll be light, strong and stiff. It'll also rattle your teeth loose over bumps as well and give your wrists, elbows and shoulders carpal-tunnel syndrome or RSI... :(


Well... look at the materials properties. Let's say you make a steel and titanium fork for comparison and you make them of exactly the same shape and design to remove 3D geometry from the comparison. Making it from 6al-4v titanium would result in a fork that is about 1/2 the weight of steel for roughly the same strength. It'll also be 1/2 as stiff as well... hench where the "forgiving" nature of titanium comes from; its higher-strength allows less material to be used for the same strength at the cost of stiffness.

They are out there!
http://www.dmcx.com/en/a127.html

Most bike design issues (except at small "custom" builders) are decided by the guys in the marketing department, not the guys in the engineering department. Carbon forks have prestige with unsophisticated customers and are light. Customers see them as a "prestige" item. Yet, in recent years, Asian factories, especially those in communist occupied portions of China, have been wholesaling carbon forks at very low prices. So, bike companies can buy cheap carbon forks, slap them on a $600 bike, and market the bike as a premium product. Ten years ago, did anyone think they would ever see a carbon fork on a $600 bike?

Heck, as cheap as some carbon parts have become, it is only a matter of time before Wal-Mart will be selling a bike with a carbon-something-or-other on it, to go with their genuine Ti colored paint jobs. For $59 bucks, you'll get a Ti colored bike with a bell that has a carbon ringer button.


If anyone is selling Ti forks cheap, I haven't heard about it. Don't think it is ever gonna happen either.

Very classy.

Alan, good to see you back at BF with your large bug in your arse about CF and your hilarious fabrications. The unsophisticated customers of CF forks include the entire 2005 and 2006 Protour, and every Litespeed customer.

Excellent primer Danno...enjoyed it...design is truely a balance.
George

Did a search and the only one I found was for $1200US

because, is it worth it? thicker steel ones or aluminum ones would work right?

Because Ti is a vanity thing, not an engineering thing.

Holy zombie btw...

8 years.