询问 MXPERTS：为什么他们不能制造防漏叉形密封件

WHY CAN’T THEY MAKE A LEAK-PROOF FORK SEAL?
尊敬的MXperts，
Perhaps it is because I race mostly at sand tracks, but I blow fork seals once a month. It has gotten to the point where if the leaking fork seal is on the right fork leg, away from the front brake rotor, I ignore it. This is a messy solution, but why can’t they make a leak-proof fork seal?

We know you won’t believe us, but the problem is not the fork seals, it is you. The next time you think your seals failed too soon, remember that state-of-the-art seals rarely wear out from use. They wear out from outside contaminants egressing the seal’s territory, and the most common cause of seal failure can be found by running your fingers up the back of your fork leg. We bet you’ll find a ding in the chrome that nicked the seal’s lip.

每个铁杆越野摩托车赛车手都讨厌他的前叉密封件。 在越野摩托车上可能出现的所有问题中，前叉密封件是最具破坏性的——不仅因为修理它们是一个巨大的痛苦，还因为在您将全新的密封件放入前叉后，无法保证它们会成功不要在下一次骑行中耽误 15 分钟。

Fork seals have failed for as long as forks have been on race bikes. So, why doesn’t some enterprising company make one that works? Surprise! The fork seals on your bike are incredible. They are self-lubricating. They work in both directions. They have specialized chemistry that makes them tough and resilient. Best of all, modern fork seals are rated for millions of cycles. Millions! Fork seals don’t leak without a reason.

As racers, we expect our fork seals not to leak, yet we also require them to move with minimal “stiction.” In other words, they can’t fit tightly against the fork legs. Why not? Stiction is the enemy of fluid movement of the forks in bumps. Reduce stiction and your forks will glide through the clatter of a race track’s terrain; however, reducing stiction increases the potential for a fork seal leak, because the seals aren’t as tight. Paradoxically, we are asking the fork seal manufacturers to build lightweight, long-lasting, UV light-resistant, tear-proof, flexible, compact fork seals that barely touch the fork legs. A few years ago, it couldn’t be done. Today, under the right circumstances, it can be done.

Fork seal designs are constantly changing. Most current seals are bidirectional with an internal metal backing to create a firm seal structure. This design prevents the pressure from extruding the edges of the seal away from proper edge position on the fork tube. Some seals use garter springs to keep a good seal at low pressures while maintaining seal position when the seals are misaligned due to fork flex. The garter spring on the leading edge can also act as a secondary scraper to prevent contamination from entering the fork; however, garter springs reduce fork performance by adding friction.

In defense of the rings of rubber, the majority of fork seal leaks are not caused by design flaws in the fork seals; they are caused, inadvertently, by the fork tube’s chrome plating. Most modern fork tubes are manufactured using a special steel alloy that creates good resilience, high hardness and ultimate yield strength. The alloy creates a uniform grain structure in the tube that is hardened just enough to bend before it breaks. Producing a high-quality tube starts with grinding the outer diameter to a high-quality finish. A precise grind minimizes wavy diameters and, at a microscopic level, creates a broad, flat surface with small troughs or valleys that lay at an angle to the seal’s leading edge. These valleys allow for a thin film of lubrication to be present on the tube’s surface. That layer of oil improves seal function and reduces friction. Contrary to popular opinion, if a fork tube’s surface is too smooth, the seal will remove the oil from the surface, increasing friction and wear.

管子表面准备好后，在磨光的表面上涂上一层非常薄的工业硬铬闪光。 铬，当应用非常薄时，会反映它下面的准备好的表面。 硬铬产生非常坚硬和光滑的表面涂层，可以抵抗磨损。 前叉管的表面处理可以包括类金刚石碳 (DLC) 和物理气相沉积 (PVD) 涂层。 虽然这些类型的涂层在外观上差别很大，但它们的总体目标是提高外层的表面硬度和管子在高负荷下的润滑性。 提高的表面硬度可在更长的时间内保持理想的表面光洁度。 这带来了额外的好处，即提高了密封件和衬套的使用寿命。

What can you do to help your fork seals? The aftermarket makes fork guards that encompass the fork leg almost completely to ward off rock dings. They also make neoprene fork guards that slip over the chrome fork legs and are held in place with a zip-tie around the bottom of the fork stanchion tubes, There are people who will tell you that these Seal Savers will hurt your fork’s performance, but those people won’t be coming over to your garage to help you change your leaking fork seals. You can also pull down the fork’s dust cover, located just below the fork seal, to make sure that area is perfectly clean. Additionally, at regular intervals, run your hand up and down the chrome fork leg. If you feel any kind of nick or dent in the chrome, you can carefully buff it out with an emery board—because that nick will tear the seal, and if you replace the torn seal, the same nick will tear your new seals.