Monday, January 29, 2007

switch to coil springs?

Seems that I've got a mystery on my hands that requires a scientific explanation and so far I am a little clueless. Realizing that cold weather affects air density making it less dense, particularly under high pressure like in a fork or shock. But some shocks seem more susceptible to loosing air in frigid temps than others...and once the air is lost you can't just pump it back up? actually under some circumstances a pump will still read high pressure when the shock or fork is totally collapsed? Very strange indeed...that's where the mystery lies and why I need help from the science savvy skills of the Myth Busters or at least Beekman's world to explain what happens to render them bunk.
Take for instance last weekend. Large group leaving the lot for what will undoubtedly be the best three hours in the entire weekend and blam! Lou's shock looses all of it's cush. Hell, it was worse than that, it collapsed like the positive air chamber leaked into the neg chamber and sucked the shock in on it self. It sucked to be Lou. We tried putting excessive air into the pos chamber (200psi) and the shaft didn't budge. Just stayed bottomed..and come to think of it, I think there was only one chamber you could adjust air volume!
wow, maybe I just talked my self through this nonsense. Is a large volume of high pressure air in the pos chamber slowly leaking into the very small volume neg chamber and sucking the whole thing closed? Lou said that this same thing had happened to him last week and the shock company (to remain nameless) sent him a replacement.
My thoughts on this...well it sucks...Literally! I don't think it's a good idea to ride my dual air bike tomorrow cause it's going to be 9 degrees at seven a.m. Although with this theory in mind you can reverse the over-inflated (small volume) neg chamber if the shock or fork has an adjustable neg air chamber...unless the seal just blows under the pressure...but then it'l just go back into the pos chamber leaving all the spv'ness (pedal bob characteristic) gone and it'l be like your riding back in the day on your '96 Pro-flex all over again! Oh yeah, hope there's people out there that remember that bike! She's a beauty.What prompted me to think about this was Christopher just called asking why his fork is dead and the pump is reading 150 psi...Put on one of your rigid forks for tomorrow Igleheart, it's going to be a bumpy ride! I think I'll take Brad's hardtail out for tomorrow's loop.

7 comments:

wraith said...

if its a fox, unscrew the end it will go pop! and re-assemble. The assembly will automaticlly set you neg. travel

Andy said...

unscrew the end of what.
your talking about a shock not fork right?

This 'pop' sounds an aweful lot like why they have the "warning high pressure, don't mess around" sticker on the outside.

wraith said...

I,ll call you whith the poop on the pop.

Andy said...

is that like poop on the potty?
you should know about that.

wraith said...

Your seals may blow by when cold. The act of assembling the shock compresses the neg. air chamber to a set value. Blow by goes from the positive side to the neg. side and the shock gets sucked down.Unscrew the shock eye from the main body after you(LET THE REMAINING AIR OUT OF THE POS. SIDE). The trapped neg. air escapes with a pop or more depending how much pressure is trapped. Reassemble and air up. Happy endings for all. p.s. not all shocks work like this.

Andy said...

thanks bro.
I'm pretty much a do it your self mechanic but this one scares me a bit. I'll just send any ailing shocks north-ward along with a sixer and let you take a look. Deal?

Untill then I'll be riding rigid when it's frigid..

wraith said...

yup!