Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125832
By John Huetter and Dave Schoonmaker One of the greatest sources of controversy and myth in motorcycling is motorcycle suspension. The bouncy, spring wound units that preven t a motorcycle from having a rigid frame are almost as big a subject of discussion, modification and dissension as the engines that propel the machines. And well they should be. Especially in off-road riding and racing, how well a motorcycle's suspension works and lasts is probably just as important as how fast the engine can make it go. As a matter of fact, you can't go any faster if your suspension is not up to the task of handling the maneuvers you need to perform and terrain your encounter. So...being only slightly less ignorant about shock absorbers and their merits, in a very honest no-BS sense, than the average competition rider we decided to test them. We selected the most prominent proprietary brands of shocks, including a couple of recent introductions that showed promise, and subjected them to a series of standardized performance tests. They are all familiar names to most riders: Boge, KONI, Arnaco "2ND", Girling, Curnutt, S&W, Betor and Ceriani. This is the report on the test of all these shocks (two at a time) installed on a 1968 Yamaha DT-1B and subjected to a comprehensive set of motocross and cross-country riding situations. o C"l t :9 o '" The Test Bed Why a DT-I? Because it is reliable, almost everybody owns one or has owned one therefore can relate to the performance and handling, and any of the shocks mentioned above will improve the performance quite a bit over the stockers that used to come ·on Yamahas. The other modifications to our "trick" test bed included removing the lights and instruments and fitting a new Dunlop 4.00 X 18 knobby on the rear. Nothing else was changed. All credit to the workhorse DT-1 engine. We never gave it a second thought or a plug change and it never let us down. /- What Was Tested Exactly what was tested about the shocks? Well, honestly, not everything. Our facilities do not include a des tructive or non-destructive test laboratory to determine sheer strength, warp under load, brittleness of metal or viscosity of fluid with temperature change, and all the things' that would constitute a truly scientific test. What we did do was bolt each set up to the old Dit Uno and 1) run them both directions over a third of a mile of sand whoop-de-doos, 2) through a bermed chicane on a motocross course consisting on a right-left-right-Ieft series of turns, 3) brake them very hard on the stutterbumps that lead into turns on most MX courses, and 4) bounce them over a three foot jump to a level landing. That covered just about all the riding conditions in dirt competition or cowtrailing that we could simulate. Indian Dunes Motor Recreation Park near Valencia, California offered the variety of terrain we required combined with a readily available motocross track that incorporated all the features, we were testing for sO that was the choice for a field evaluation site. It was convenient and they put up with us for more days than we care to remember. Dollars and Sense Start at the beginning. One of the first things that concerns a potential buyer of an accessory shock absorber is how much it will cost him to, hopefully, improve the handling of his machine. Shocks are not a particularly cheap item as bolt-on items go. The price per set, with springs, of the ones we tested follows. BETOR - $36.95. They are rebuildable and the rebuild kit costs $13.90. ARNACO - $49.90. Rebuildable with a price on the parts that varies according to what you need to fix. BOGE $36.60. There are three different models for smooth track, motocross or desert so price for each model may vary. • S&W - $37.8,0 for the shocks plus $12 -16 for the spiings depending on the wind for a total price of $49.80 to $53.80 based on your choice of spring. This is what we tested and what we tested them on. Top, left to right: Arnaco "2ND", Girling, Ceriani. Bottom, left to right: Curnutt, s&W, Boge and Betor. On the DT-1, KONI 80. CURNUTT - $39.00 for the 3.7 inch travel model we tested. Includes the springs which are always a constan t wind,. ,as are the Arnacos. (And they're bright red.) KONI - $50.00 plus $12 for the springs. S&W springs are recommended to go with the KONIs. They are rebuildable. G1RLlNG - Recommended price for two Girlings is $38.50, including springs, for the model we tested. They are consiqered a sealed unit and not rebuildable. CERIANI - $46.00 including springs for an Italian shock that is rebuildable, with a price tage of $3.55 for the rebuild kit for two dampers. You will pay anywhere from about $40 to about $60 plus any applicable taxes, etc. for a seol of shocks. That, in itself, seems reason enough to make sure the choice is the righ t one for your bike and your type and style of riding. And that's what this test is all about. Not which is the "best" shock because that's not a meaningful term with such a wide variety of bikes, events, tracks, courses, riders and riding ability but, instead, to provide enough information for you to make the best choice 'of a shock for your purposes. Fit to the Bike: Custom or Back to the Grinding Wheel? The second thing' you have to do after you've laid out YOur dollars is to put the shocks on your mo.torcycle.. We asked all the distributors for a set of shocks for a Yamaha DT-1B. We expected that they would all fit a Yamaha DT-1B. Some of them didn't. This got to be a real hassle as we scrounged around for a machine shop to grind, drill and otherwise shape the eyelets and bushings to fit the 10mm bolt with a shoulder that holds shock absorbers on to a Yamaha of our particular vintage. Now, for sure, the manufacturers are going to say, "The dummies. Why didn't they just change the bushings and spacers to make them fit?" We still think it's a lot to ask of a buyer to layout about fifty bucks and then not have the item fit his bike. Maybe the bushings aren't that easy to find if you're Joe Average and maybe you don't have a machine shop down the block. Even if you do have access to a place for modifications they're going to charge you a dollar or three per shock to shave the metal to the right dimensions. Surprisingly, the KONIs, Girlings and Cerianis came with bushings that were too wide for the shock mounts. Additionally, the Girling's metal eye spacer was too small to accept the bolt. The Betors we originally received were an inch and a half too long and would have destroyed the basic geometry of the bike but they did fit the mounting brackets. The Arnacos were the best slip-in fit with the Curnutts a close second. The Boge and S&W were somewhere in between the two extremes in terms of grunt and struggle. We ground and drilled them all to fit. It was not fun. Speaking of Dimensions The weight, internal design, shaft diameter and fluid capacity of the shocks varied widely indicating to us that there are still a number of schools of thought as to what makes a good shock absorber. Without going into the details of in tema! design, which most riders will never see anyway, some key dimensional statistics are detailed below. Coming Up Short How much suspension travel you have' at both ends of your motorcycle is going to determine, to a large extent, how controllable a ride you enjoy (or don't enjoy) over rough ground. Not all shocks for the same bike have the same actual travel, which isn't too surprising if you stop. to think about it. Some manufacturers, such as Curnutt, even make a point of selling shocks with markedly different travel for different riders' preferences. The distance the piston travels before it comes to a screeching or thumping hall isn't the whole story since internal valving design and rates of damping progression are more important in determining 27