Suspension Setup and Tall Gearing | Ask the Geek

Anthony's Suspension Woes
I have a 2009 Yamaha FZ1 with a Penske 8983 and the stock fork tweaked—read "clicked-out by my local suspension guy." The forks are showing 6mm above the top triple clamp, the shock is 6-7mm of threaded rod out of the ride height adjuster. Yes, I know you need to know how much longer that is than stock but that's all I have for you now. With this setup the bike seems like it still wants to run wide in the fast stuff, leaned over, knee on the deck. What would you suggest for a geometry set up? I weigh about 220 pounds with gear, and am at 35mm of sag in front with the preload cranked all the way in, 30mm rear with a 625 lb/in. spring. I know I need new springs in the front, but do I need a re-valve? A cartridge? Someone told me to junk the front end and go with an 06-08 R1 setup.
via SR Mail

Your FZ1 is sprung too softly for your weight, and it’s doubtful you’ll find a decent geometry compromise with the setup you have now. The stock springs on your FZ1 are .95kg/mm in the fork and 685 lb/in. on the shock, so you’ve gone even softer than stock with the Penske shock. Penske, according to its application chart, recommends a 750 lb/in. spring for a rider weighing between 190 and 225 pounds—significantly stiffer than what you’ve got now. Up front, you would be better off with 1.0kg/mm springs, especially for track riding. Because the rear spring you have now is so soft, your bike is squatting too much under acceleration and causing it to run wide on corner exits. Install some stiffer springs for a start and experiment from there. You can always look into some more elaborate modifications to the fork if you still have trouble finding a comfortable setup.

ZX-10R Gearing
I love my new Kawasaki ZX-10R. It does everything well, and with an ECU re-flash from Dynotronics, it is fast as hell. My question: Why did Kawasaki gear it so high? It is apparent while riding it, and from magazine shoot-outs, that it is geared too high. Why did they sell it that way?
Paul Taylor
Knoxville, TN

There are a couple of causes for the tall gearing on not only the new ZX-10R but also many other newer sportbikes. The attached graph is from our literbike comparison test earlier this year ("The Empire Strikes Back", July '11), and you can see the theoretical top speed of the bike is around 190 mph. We weren't able to test the bikes for top speed this year, but it's a safe bet the 10R tops out at about 185 mph, the unofficial limit. Generally, manufacturers ensure that the actual top speed of a particular model is a bit clear of the theoretical top speed; this stops the bike from running on the rev limiter for an extended period if you decide to go top-speeding. That explains the high top gear, but look at the rest of the gearbox on the chart—the ZX-10R's transmission ratios are all higher than the BMW S 1000 RR's, and much higher than the Ducati 1198's. Racing organizations require stock transmissions for most classes (even AMA SuperBike), and as sportbikes' power curves constantly shift toward the top-end, the transmission ratios are closed-up to match for best performance. Combine the tighter transmission ratios with taller overall gearing for a faster top speed as a bike gets more powerful, and the lower gears are doubly affected. SR

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