Quote:
Originally Posted by DannoXYZ
I think we'd need to measure the knuckle's angle relative to the dogbones and use an inverse-sine function to arrive at leverage-ratio. When knuckle's parallel with 90-degrees motion to dogbones, we'd get most leverage (swingarm to shock). Then as it moves away from centre, leverage decreases more and more.
With different shock-length and spring-rate, the resting-position of the knuckle & dogbones are no longer parallel and shock has less leverage. Combined with stiff spring, this adds even more effective spring-rate at rear-wheel.
I found spreadsheet with various GSXR shock options.
I think you want to go with '04-05 GSXR-750 shock with longer length if you wanted to raise rear-end. And the 7.3kg/mm spring is more appropriate for a street bike with your weight. Spring of 8.4kg/mm is what you'd use on race bike. The 9.5kg/mm spring is more fitting for +200-lb rider on race bike. |
I bought a 05 GSXR 750 shock from ebay, should be here in a few days. I verified that it does have the 7.3k spring through other sources and all of your info on length looks correct.
My original 250r shock was 323mm. The '09 750 shock is 317mm. The '04 750 shock is 332mm. Ten milimeters longer than stock.
I have the original 250 linkage (164mm), and the aftermarket (152mm) linkage so I will have options to experiment with.
If it's important -- the '09 GSXR shock gave me 120mm of suspension travel with the aftermarket dog bone links. 127mm of suspension travel with the 250r links.
The 250r shock gave me 130mm of suspension travel with the 250r links. Never measured travel with aftermarket dog bone links and the original 250r shock.
Didn't seem to have any clearance issues with anything -- the rear tire came within 3/4" of the fender when it was all the way up -- and my rear tire is pretty worn. A fresh tire would certainly be taller but I don't think it would rub the fender. I'm also running the 140 tire in the rear instead of the recommended 130 tire.
And none of the suspension travel tests were done with bumpstops. None of these shocks have bumpstops. They have all rotted and fallen out. The bumpstop should come into action before the rear wheel gets that high.