Re: Rear shocks on a 1979 R100 RT
Posted: Mon Sep 23, 2013 1:55 pm
My thoughts as well. 5" of rear shock travel would mean about 8" of rear wheel travel. Your rear suspension bottoming would result in the rear tire trying to make it's way through the rear fender.khittner1 wrote:Interesting point about the shock travel comparison. I don't remember enough of my geometry and/or trigonometry to compute this myself, but there's at least a little bit involved in converting the shock's compressibility to a "suspension travel" figure at the axle. My Haynes manual agrees with Garnet that the /7 bikes had rear suspension travel of 4.92 inches/125mm, unless they had Nivomats, in which case it had a suspension travel of 3.37 inches/85mm. Ikon's chart does show the "Travel inches to bump stop" of their 7610-1298 shock absorber to be 2.95 inches/75mm. I'll leave it to more recently-practiced geometricians to determine what the "suspension travel" at the wheel axle would be with an Ikon shock that can compress only that much. Given the similarity in appearances of the progressive spring windings of the OE Boge shocks and present-day Ikons, it doesn't seem intuitive to me how the OE non-Nivomat Boge shocks would have had so much more travel before their springs and shock bodies would be fully compressed.
I think I know where this misunderstanding comes from. Phil Hawksley lists the specs for the R100 this way:
Spring Travel Front/Rear
200 / 125 mm (7.87 x 4.92 in)
If one did not know better, this could leave one thinking that the spring, or shock absorber assembly, travels 4.92", when it is clearly speaking of what we 'Mericans refer to as "rear wheel travel."
Silly English.
