[w00dy]

Curious if any of you industry-types could toss me some details on the different coatings used on fork stanchions.

To my knowledge the gold finishes are Titanium nitride, the black ones are black hard ano presumably with teflon impregnation, and the silver/chrome ones are a nickel process also presumably with some kind of lube impregnation.

How about bushing material? Are they just steel/brass/PTFE DU bushings?

 

[boogenman]

Curious if any of you industry-types could toss me some details on the different coatings used on fork stanchions.

To my knowledge the gold finishes are Titanium nitride, the black ones are black hard ano presumably with teflon impregnation, and the silver/chrome ones are a nickel process also presumably with some kind of lube impregnation.

How about bushing material? Are they just steel/brass/PTFE DU bushings?

hey guy email craig at avy.

 

[LMC]

check out DLC as well, Diamond like carbon.

 

[NY_Star]

hey guy email craig at avy.

If your not going to spend any money with the guy why bug him for information?


Most of the bushings are a DU material. The way the black stays on my Manitou makes me believe that it is a Class II died Coating not a Class III Type II Black.

 

[ohio]

I'll try not to get into the chemistry, and I'm working from memory so I may have to come back and correct a few mistakes. In order of hardness...

Hard-anodizing: The type just refers to the thickness, and Type III is considered "hard anodizing." This is the champagne colored anodizing used on most forks (I believe it is also the black coating used on some Marzocchi forks). Back when, this was usually a teflon-impregnated hard anodizing. Self-lubricating, fairly hard, and somewhat cheap. I'm not certain that teflon is still the common practice.

Nickel or chrome plating: These deposit a new metal surface via electroplating. Similar to anodizing, "hard chrome" refers to a thicker plating. They are not as hard as Ti-N, but are more durable than anodizing (and maybe harder... not sure). They should also hold oil better than Ti-N. I'm not sure what Rockshox slippery silver was, but this applies to some Marzocchi forks.

Ti-N: Titanium Nitride (there is no Nitrate) is the shiny yellow gold (like ohlins moto forks). It's very hard and not that cheap. Super smooth but not self lubricating and doesn't hold oil well, so it works best in upside-down forks. Some variations on this are TiCN, which is black and even harder, but I don't think that's been used for stanchions.

DLC: Diamond-like carbon is a whole family of materials. It's hard as hell and super durable, and to my knowledge has only been used in moto forks, not MTBs. It's used on Gilette Mach3 razors though... I have no idea it's surface smoothness or lubricity, but I suspect it's no better than the others and more that Showa/Suzuki needed a gimmick to avoid shelling out for TiN. The version used for forks is black, and I suspect has the same problems as TiN.

All of the above are really hard to scratch (think "sand"), and so thin that they will gouge (think "rock"). I don't think any of the harder coatings offer a real performance advantage, maybe even a disadvantage because a Teflon hard ano doesn't need the oil cycled to feel smooth. Your bushings, seals, and oil will make a much bigger difference.

Basically, two things can lubricate a stanchion - teflon-impregnation or oil captured in the microtexture. Friction coefficients are mostly meaningless as they are either between like materials or sometimes on a specific metal... not oil-lubricated. The smoother the finish, the less oil captured and you need an upside down format or foam rings to try to get an oil film at the seal.

 

[w00dy]

Ohio, thanks for all the detail. You filled in several gaps I couldn't glean just from surfing tubes.

I'm interested because there is concern that the hard ano we're using could cause fatigue issues because it forms microcracks in the surface of the material. I wanted to learn more about TiNi because it's deposited on the surface instead of changing the properties of the metal.

I don't know if chrome plating would be better or worse. The DLC stuff sounds interesting. It's worth a look.

 

[ohio]

I wouldn't worry about microcracks. It's such a perfect polished surface there really isn't anywhere for it to start, not to mention the chances are much higher of you gouging the surface or buckling the tube before a crack could form and propogate. I don't think I've ever heard of a fatigue failure in a stanchion.

It's more of an issue with irregular surfaces like a welded frame, but even then I've never heard of a true fatigue failure... think of all the anodized handlebars out there.

All of these coatings were developed for truly intense, high-cycle, high-wear environments like inside high-performance engines (crankshafts, pistons, valves) and industrial cutting tools. We're not taking them anywhere near their limits (until we crash).

 

[w00dy]

It's not for stanchion tubes, it's for a seatpost with irregular angles and machined surfaces which has to pass a rigorous fatigue test battery. We've got something which passes and does it well, but if I confirm my suspicions during testing that the anodizing hurts the results I want to have other options.

 

[boogenman]

If your not going to spend any money with the guy why bug him for information?

People in the industry some times shoot the poop with other industry guys on the phone or in person to kill time or to take a break. Calm down care bear.

 

[Old_Sckool]

People in the industry some times shoot the poop with other industry guys on the phone or in person to kill time or to take a break. Calm down care bear.

Agreed. Unless you catch him at the wrong time. It's pretty hard to get Craig off the fricken phone. That guy will talk suspension till you bleed.