|While most bicycle designers are convinced that four-bar linkages are the best solution for mountain bike rear suspension, the simple single-pivot swingarm type has persisted, even flourished, right under their noses. Trek's entire off-road range uses it, as does Devinci and Cannondale, and your pick, the Santa Cruz Heckler, has been a high ranking member of the single-pivot swingarm club which has survived in spite of the fact that SC has invested heavily in its four-bar VPP System. The staying power of the single-pivot swingarm hinges on its simplicity. It has fewer moving parts and that means it can either be made stronger, lighter, or more reliable - or a combination of all three. Technically, the single-pivot swingarm's long lever arm can be used to minimize leverage rate changes as the suspension compresses, which suspension tuners love, especially in the case of longer travel bikes. Efficient pedaling is equally important, and the exact placement of the forward swingarm pivot largely determines how firm or mushy the suspension will feel under power. Magically, this secret spot has evolved to be somewhere at or in front of the bottom bracket centerline and aligned with the chain pretty close to where it intersects the top of a 30-tooth front sprocket. A single-pivot-type suspension configured as such, and designed to drive the shock with a slight rising leverage rate is tough to beat.|
Four-bar suspensions can offer marginal improvements because their forward pivot locations are not fixed. As the suspension compresses, the point that the wheel pivots around migrates. Clever designers can manipulate the various lengths and pivot locations of each suspension member to control or enhance the way the suspension affects braking, pedaling firmness and suspension sensitivity. The possible combinations are limitless and thus, four-bar cycling suspension has spawned a zillion patents along with a never-ending spiel of marketing claims. In real life, however, four-bar suspensions are nearly as limited as the old fashion single-pivot types, because manipulating the linkage geometry to achieve gains in one arena, like uncoupled braking or pedaling firmness, for example, erodes the suspension's performance somewhere else. It should come as no surprise then, that the best performing four-bar suspensions today are compromises - careful blends of the positive and negative attributes that come with migrating pivot locations and leverage rates. And it also should come as no surprise, given the fact that the customer wants the same things from both systems - efficient pedaling, bottomless suspension action and accurate braking - that the performance of the better four-bar and single-pivot bikes available today varies by only a few percentage points. So, if you like simple and the Heckler floats your boat, I'd recommend it. - RC
The Heckler's single-pivot swingarm and simple suspension design doesn't require a Ph.D. to tune and rest assured, Santa Cruz wouldn't sell it unless it pedaled well and descended faster than an aging rap star. Santa Cruz photo
|The past few seasons have seen internal cable routing come back in fashion, for no real reason other than achieving the clean, sleek look that hiding shift and brake lines inside the frame allows. Luckily, most bike manufacturers are using some sort of internal guide or sleeve to make housing installation and replacement easier, a welcome change from the earlier attempts at internal routing that required the hand and eye coordination of a bomb squad technician to deal with. While it is easier slightly easier for water to get into the frame with this design, I wouldn't say it's that much of a detriment. As you mentioned, many bikes use a rubber grommet of some kind to help keep moisture out, as well as to prevent the housing from rattling against the frame. Also, there's often a drain point located on the bottom bracket shell that will give water a place to exit. If you do happen to go on an extremely wet ride, or got a little zesty with the pressure washer, removing the seatpost and turning your bike upside down will allow most of the water that entered the frame to drain out. Even here in the Pacific Northwest, where riding in wet weather is a fact of life, I haven't run into any major problems with water collecting in frames due to the internal routing. |
As far as Scott's new Voltage FR 710 goes, the amount of internal routing on that bike is fairly minimal - the housing is routed externally on the downtube, with only the rear derailleur housing entering the frame briefly on the driveside seatstay. - Mike Kazimer
It might not look like it from this angle, but the majority of the Voltage 710's housing is routed externally.
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