“Tell me how you’re gonna crash, and I’ll tell you what to buy.”
I hear that a lot from Bobby B., our in-house race guru. He says it to prove a point: Every crash is a symphony of infinite variability. I can't tell you what kind of chassis protectors will be perfect for your situation, because I don't know how you plan to crash. Careful consideration and education, though, may enable studious riders to formulate answers by asking the right questions.
What kind of bikes are sliders for?
Off-road crashes and street crashes usually differ in terms of impact surface and speed, so the methods for protecting the bike vary. Sliders work best where they can actually slide — that’s on the tarmac. Because off-road surfaces are usually softer, a single point of contact like a slider would “dig in” and increase the probability the bike could begin flipping during the crash, which in turn increases violent impact. See Spurgeon's story on crash bars for a discussion of protection that's appropriate for off-road bikes.
What will the slider protect?
The idea behind frame sliders is to disperse the impact from a crash across the frame and through the engine, which is usually a more rigid structure than the bike’s frame. It should be noted that the bike itself would probably slide best in most crashes without any type of a slider, but the downside to that is that there’s no way to keep the chassis from being harmed structurally or gouged in the crash.
Because the slider protrudes from the motorcycle, it is in and of itself a compromise: The goal of the slider is to elevate the bike just enough to keep crucial parts from being ground away to dust, but not so much that it promotes the bike flipping or rolling.
However, some riders aren’t worried about totaling the bike. Instead they are concerned with smaller parts — busted engine covers, snapped shift levers, or gouged fairings. These items sometimes suffer if a bike gets tipped over at low-speed or even just knocked off a stand. A slider can offer a less obtrusive protection option than a cage or crash bars.
The reason this matters is because sliders come in different lengths. For maximum frame and engine protection, shorter sliders shine. Because they don’t “lever” the bike up off the ground very far, it’s harder for a short slider to make the bike flip over in a crash. Short sliders are also less likely to bend or snap off.
However, if you’re more concerned with saving your plastics or making sure your tank doesn’t get dented, longer sliders may be the way to go. Long sliders keep more of the bike off the ground. In a long-distance slide, too, they also have more material to sacrifice and be ground away before bike parts start being abraded.
Understand that both designs have their strengths.
Do you mind modifying your bike permanently?
If you have a sport bike and you install frame sliders, you might have some cuttin' to do.
If you’re riding around on a naked bike, life is easy. Installation is usually a snap, because one merely needs to fasten the slider to the engine mount bolts. However, for faired bikes, the process becomes more difficult, because the plastics often must be removed for installation, and sometimes require holes to be cut in them to allow the sliders to pass through. As such, sliders usually come in two flavors, usually called “cut” and “no-cut.”
“Cut”-type sliders, require a hole to be made in the fairing to access a mounting point. Engine mount bolts are usually the strongest and best way to anchor the slider to the bike. Being fastened directly to the engine and frame helps disperse the impact load of the crash.
“No-cut” sliders usually mount to a bracket that is cantilevered or offset around bodywork so plastics do not have to be permanently modified. The downside to this approach is that the mount also becomes a weak point. Because of the additional leverage exerted by the mount, it’s possible that the slider could actually damage the frame — the direct opposite of the slider’s intended task.
Generally speaking, “cut” kits are for folks who aren’t shy about modifying things or possibly have a set of easily modified track plastics on their bikes. “No-cut” kits can be better for riders who aren’t facing conditions quite as brutal as track crashes and/or who don’t want to slice up expensive OEM fairings.
There’s a third kind of slider, too, and that’s the under-body frame slider. These sliders actually sit between your chassis and plastics, so they are “invisible” to the eye. These offer chassis protection, but nothing for the bodywork.
How is the slider constructed?
Some sliders, usually aluminum ones, mount integrally. Others have mounts secured by fasteners, like washers, nuts, and bolts. Still others have a metal sleeve that’s “pressed” into a plastic slider body. Press-fit items may fare better in a bending scenario and help keep some forces from being transferred to the frame, but they may also tear away just when you need them most. A more positive mount setup may be more durable, but could transmit impact or bending forces to the frame more efficiently, which is the opposite of what you’ve got them on there for.
What material are they made of?
By and large, sliders are made of some form of aluminum or plastic, or possibly both. Aluminum sliders will typically wear down more slowly over a given distance than plastic, but the coefficient of friction is higher, so it may be more apt to flip the bike over. In general, aluminum sliders transfer more shock load to the bike’s chassis when it first makes contact with the ground.
Plastic sliders typically glide over the surface better, but they wear down faster. Plastic-based sliders also are far more susceptible to melting, depending on what polymer is used. Common materials include Delrin and UHMWP.
Sliders that utilize both materials attempt to marry the best features of each, but harbor a potential weakness at the joint where the two materials meet.
How many points of contact do you need?
We’ve geared this article primarily to frame and chassis sliders, but there are other types of sliding protection.
Bar-end sliders usually take the place of the weights at the end of a sport bike’s clip-ons, providing another point of elevation during a get-off. Axle sliders can be installed on the front fork, and their counterpart, swingarm sliders, can be installed for some rear peace of mind. Axle block sliders are a derivative of the swingarm style and integrate the rear axle into the overall protection plan. The axle and swingarm types of slider are also available as spool sliders, providing even more function. (Spools are small items shaped like their namesakes that serve as lifting points for paddock stands.)
More points to slide mean less potential for bike parts to touch pavement, but more chance of the bike “digging in” and flipping.
Keep in mind there are other types of protection, like case guards, if you want to protect more than just your chassis.
What kind of hardware is being used?
Hardware is usually described in terms of its “grade,” or hardness. Common hardware grades in the United States are grades 2, 5, and 8, with strength increasing with number. Bolts are made stronger through the amount of carbon in the alloy, as well as the specific heat treatment of the fastener. Bolt hardness is gained at the expense of flexibility. A strong bolt is also usually fairly brittle.
Higher grades of hardware may better resist the initial impact and shearing forces, but they may also transmit too much of the force to the motorcycle’s chassis, allowing another component to break rather than being sacrificial. Lower grades of hardware may deform or break, failing to protect the bike.
There are no right or wrong answers when it comes to protecting your bike. However, understanding the range of materials and designs that exist will aid in the selection of a part that will be best tailored to an individual riding style. You can’t plan for everything, but you can plan for what’s likely.
Or you can just tell Bobby how you are going to crash, and he can tell you what to get!