New 'Metric' Shock Sizes Demystified - What Does It Mean? 19

​RockShox, in conjunction with five other suspension brands, just announced a new sizing system for rear shocks that will be used on some 2017 bike models. What does it mean?

The press release reads:

Today marks a very important day where six of the bicycle industry’s main suspension manufactures, including RockShox, are making an announcement concerning the future of rear shocks and bicycle frame design. Each of the brands involved in this will announce their specific plans separately according to their own product release timing schedule. We are excited to be a part of this and for the improvements it will bring to suspension products and bicycles in the near future, which have been broadly recognized throughout our industry. Expect exciting new product announcements from RockShox surrounding this innovative new approach to rear shock design soon.

Confused? We don't blame you. This brain buster did drop just hours before April Fools' Day. In an effort to demystify the announcement, here's a rundown of some basics. We'll be diving far deeper into the topic and some of the new products next week. There's still much to be told...

What is "Metric?"

Shocks have been produced in several convenient imperial eye-to-eye and stroke sizes for years (6.5x1.5", 7.875x2.0", 8.5x2.5", etc). While these numbers can certainly be converted to the metric system using some simple math (1" = 25.4mm, ya dummy), "metric" isn't just a switch in listed dimensions, and this whole thing has little to do with metric versus imperial systems. "Metric," as it's referred to here, is actually a new set of sizes for rear shocks that have been agreed upon by suspension and frame manufacturers. That means new eye-to-eye and stroke measurements are coming soon, and, given the name, they'll likely be in conveniently chosen increments of millimeters. The press release also hints at new "fitment options," which may refer to mounting types and hardware.

Why might this be a good thing?

Surely some of you are grumbling, "If it ain't broke, don't fix it." While current shock sizes certainly get the job done, a move to different shock sizes could increase the space inside, allowing designers to make a better product. Most of us just see the relatively simple outside appearance of a shock, but what goes on internally is very complicated. One of the most commonly used air shocks on enduro bikes, 7.875 x 2.25" (200.025 x 57.15mm), is a particularly hard one to make work well given current internal space restrictions. Turns out every millimeter is precious.

Also, with what seems like a bajillion different hardware sizes to choose from, simplification of the system would certainly be nice. Ever been into a bike shop in search of hardware for your new shock, or perhaps a spare shock so you can keep your riding trip alive? Did it end in you walking out the door empty handed or by filing/grinding down something that was too big? This is one frustration we'd be happy to see gone.

What suspension brands are participating?

The press release listed six suspension companies that will produce metric shocks - RockShox, DVO, Cane Creek, Manitou, SR Suntour, and X-Fusion. While the companies have all agreed to make shocks in the new sizes, product development will continue to happen independently. This means that how one company takes advantage of the new sizing may differ to the others.

What about FOX?

FOX is notably absent from the press release issued by RockShox. Curious as to why, especially when this is being billed as something from the "bicycle industry's main suspension manufacturers," we reached out to the brand. The company's official response was that "FOX will continue to work with its customers to provide specific rear shock applications that best suit their frame designs. This support includes imperial, as well as metric based applications."

So yes, FOX will make new metric size shocks as well, but they've chosen to let the market dictate what is best.

What bike companies will make the switch?

We've been asked to stay hush about specific names for now, but we know of 15 bike companies that plan to use metric shocks on their 2017 models. The frames will use new eye-to-eye measurements and stroke lengths, and likely new rear shocks as well.

Will the old sizes still be available?

Yes. In fact many bikes will continue to run the current shock sizes. The six companies listed in the press release will keep making them until demand falls. Time will tell if this catches on, but with the backing of several suspension brands it's likely to take hold.

What new shock sizes will be offered? How will shocks change? How will frames change? Does it ride better? Are there any downsides?

Ah yes, the juicy questions. Stay tuned for the answers to all these and more as we dive into the new system and take a close look at some fresh RockShox products in an upcoming Vital MTB feature.

Update: Read our in-depth guide to Metric and the new RockShox Super Deluxe shock