Showa Big Piston Forks

     Unlike normal telescopic upside down forks, the Big Piston Fork by Showa certainly is a nice addition to modern motorcycle technology.  Before I proceed on what the Big Piston Fork does, let me start by introducing the black art of suspension settings which is eliminated with the Big Piston Fork.  Normally for the front fork, rider sag is set to be between 15mm to 20mm for track to 20mm to 25mm for road riding, with figures differing by fork manufacturers and make, normally +5mm in between meeting the rule of thumb that the front fork should operate in between 25% to 30% of it's total travel.

Comparison Between Conventional and Showa BPF

     We're not going to talk about how the forces goes through a suspension as it will be a chapter in the black arts of suspension settings, but in short, when we brake, we dive the forks and when we open the throttle, we unload the fork.  Bottoming out occurs when the forks completes its travel, ending it's ability to spring operate over the pressure acted towards it, and topping occurs when we accelerate, unloading the front tire off its required weight to keep it on the ground. 

Fluid movement during Tension (throttling) and Compression (braking)

     The Big Piston Fork introduced by Showa is lighter and more stable than the conventional forks. What actually happens is that it has an additional springs that prevents the forks from topping out and bottoming out.  The tension and compression is set on the top while the ride height is set at the bottom of the forks.  Unlike conventional fork setup, there is not a precises sag settings.  Setting up the height of the forks is accomplished by putting cable tie to the front fork, and then decide if it is enough after test riding the bike.  Even on 3 clicks (low to high) is sufficient for the bike to operate properly.  The normal setup height is around 10 clicks to 20 clicks (low to high) range.  

     As the big piston forks does not work on the standard travel idea of the front forks, altering the height of the suspension also alters the geometry of the motorcycle, lowering it to increase turning (reduces the rake) and heightening it to increase stability (increases the trail) which for normal telescopic forks is done by altering the yoke of the motorcycle.  As for the tension and compression settings this is subjective to the rider. However, the proper compression and tension damping setup will be discuseed later on in this blog.

Tension and Compression settings on top. Settings is from Tension -> Soft for the Big Piston Forks

   The Big Piston Fork is lighter than conventional forks and performs astoundingly consistent through its torment.  Winning the Suzuka 8 hours race on a GSX-R1000 in 2007,  it weights 720 grams than the lightest conventional forks and it is currently seen to gain popularity being spotted in the latest release of sportbikes, with the Kawasaki zx6r 2009 model being the first middleweight superbike to be equipped with this beauty. 

     Personally, I must say the Big Piston Fork is a very nice suspension to have but bear in mind, the feel of the motorcycle changes with the Big Piston Forks. As it doesn't bottom or top out, when tormenting the motorcycle to the limits , the activating springs gives a numbing feel to the rider which is debatable whether it is good or bad.  I myself am familiar with the feeling of the fork bottoming out as a sign to let go of the front brakes a little.