Forum

[Paulk]

Thack (again) that's made me laugh. Don't know if you are aware but I've had a couple of long running difference of opinion threads with folk telling me how wrong I am when I've said the same as you. The thought that (until now hadn't occurred to me) fact of the air pressure means people we're doing the exact opposite to what they we're trying to achieve - apart from the pointless changing of the ride hieght, has made me smile. Thank you.

[Thack]

Hi @Paulk. Yes, the physics is perfectly straightforward and simple, both for the "only the ride height" issue, and for the air spring characteristics. As I say, I don't know how much the air spring contributes to the overall spring force. If it is only a small percentage, the softening as you raise the ride height is probably imperceptible. But the "pre-load" nonsense has been comprehensively dealt with numerous times already, not least in Sportbike Performance Handbook, 2nd edition, by the renowned Kevin Cameron. Here's a quote from p115: "A fair number of people intuitively believe that increasing the preload makes the suspension stiffer. It does not! All the preload adjuster does is raise or lower the point at which the bike rides on its suspension. [...T]he only way to make the spring stiffer is to replace it with a stiffer spring."

[Thack]

By the way, I've written to SonicSprings pointing out that the article is misleading at the end (although not technically incorrect because they say the effect isn't "magical", which is obviously true). I'll let you know what they say, if they reply.