Dear MBT,
I have a coil Rock Shox fork that’s making a clank whenever I hop things. What do you think this could be? Is my fork shot?

-Greg White

It sounds to us like what you’re experiencing is known as topping out - which is rather what it sounds like: the opposite of bottoming out. Bottoming out is the harsh metal on metal contact that comes from blowing through all of your suspension’s travel too rapidly. Topping out is the metallic clank that comes from your suspension rebounding too heavily and returning to the top of its travel too quickly.

There are typically two factors to remedying this: An air spring (rather than an internal metal coil like your fork has) can be pressurized to compensate (through a negative spring, which counteracts the compression forces). Additionally most medium to higher end forks have a rebound adjustment circuit, which further controls the rate at which the suspension returns to full travel.

Lower end units usually lack both of these luxuries and thus the metal spring overpowers the compression function’s ability to slow the rebound and that’s the clanking you hear when the unit tops out.


Dear MBT,
Help me understand how fat bikes work. Wouldn’t a fatter wheel and tire push more weight and push a lot more through snow and sand? What am I missing here?

-Harold Drewn


You’re partially right that there is often a weight penalty associated with the wider componentry but to summarize the physics broadly, it’s the same principle why a boat doesn’t sink even when fully loaded with cargo: Distribution of mass over a wider surface area.

The wider footprint attempts to keep the mass atop of loose surfaces rather than cutting into it like a knife.

The physics work to an extent but, as you pointed out, too much weight and momentum can make the front end “dig in” especially during aggressive cornering. Like all things, mastering the skills required to push the pedals through loose surfaces is an art unto itself.

Dear MBT,
Wondering why you guys don’t start reviewing e-Bikes. It’s really becoming the hottest segment right now. It seems like there’s something missing in the mags and sites that don’t bother acknowledging them.

-Corey Urban

It seems that for every litter like yours chastising us for “ignoring” the segment, there is another praising us for not promoting the impurification of the sport. Does this mean we’re against any and all forms of electric-propulsion here at MBT? Of course not. E-assist in particular has a very practical function for those individuals who, for whatever reason, lack the physical ability to enjoy all aspects of the trails but wish to participate.

Of course we entertain the counter argument as well that electric powered bikes are, by definition, no longer bicycles but rather motorcycles. Less an issue for us personally, this creates a whole lot of gray area with land management organizations; many of which tolerate mountain bikes but strictly prohibit ATVs. Public riding areas shut down over this overlap is certainly something to which we hope never to contribute.

Even over all of these heavy issues, the simplest explanation we can offer is that to date an e-powered test bike has yet to manifest at our office. If one were to arrive, we’d be glad to put it through its paces and deliver the results here in our pages so that the consumer can make up his or her own mind.

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