42 psi max fork pressure?

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42 psi max fork pressure?

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42 psi max fork pressure? - 4/27/2008 2:26:53 AM

Gearloose

Posts: 75
Joined: 9/12/2007
Status: offline

Hiyas. My owner's handbook recommends 0-6 psi, and says not to exceed 42psi. It says high air pressure settings provide a firmer ride and are for heavy loads and rough road conditions.

Has anyone had any experience with running higher fork air pressure than 6psi on twisties or the track? I'd like to know...

1. Does higher pressure than 6 psi cause any problems?
2. I'm thinking of how it might improve handling in the twisties - but does it make the bike more unpredicatable?
3. Is there a good pressure for a 200lb/90kg rider and standard front springs?
4. Why go for harder springs (recommended by some suspension and emulator manufacturers) if higher air pressure can achieve a similar result?
5. Do emulators make any difference to what air pressure should be run?

(I'd rather someone told me if higher air pressure creates problems than find out myself!)
Thanks team!

< Message edited by Gearloose -- 4/27/2008 3:12:12 AM >

Post #: 1

RE: 42 psi max fork pressure? - 4/27/2008 10:39:12 AM

michigan_313

Posts: 674
Joined: 2/24/2006
Status: offline

what part of the owners manual says that? 42? the only thing that should be getting 42 is the rear tire.

1. yes. a lot higher than 6, you could blow the seals.

2. no. predicatability will stay the same since height has not changed.

3. no. this is rider preference and depends on the current state of fork action and internals.

4. higher air pressure will only work to a limited extent. as stated in #3, depends on current state of fork and internals (spring, bushings, oil, etc.).

5. no. emulators help with the flow of oil. better oil flow means better fork action.

there is no fork, oem or aftermarket that will allow you to put 42 psi of air into it. you could put a little bit more than 6, but 6 is the limit. by the time you have finished riding, there will be more than 6 psi in your forks. why? because the air in the fork tubes will expand from the heat that the forks are absorbing from the radiator, air temp, and fork action (some slider friction). on a real hot day, you could have as much as 15 psi due to thermal expansion. adding air is only for minor adjustment, not to make a major change in fork performance. that's what springs are for.

have you rebuilt your forks? if not, do you know the state of the springs and oil? if not, no amount of air is going to help firm up the front end if your springs are shot. for instance if you go over a bump and you hear a "thump", or under hard braking the front end dives excessively, that's the forks bottoming out.

from experience, i had my forks rebuilt with heavier springs, emulators, and stock oil weight and amount. fork feel was much firmer and action was much better. this was with no air added. the performance is night and day going through canyons. no front end dive under heavy braking, great front end feel, better action through mid corner turns over bumps.

yes, the rebuild was pricey, but worth it. all internals are from racetech. i ran it for 3 years without a hitch. now i run a '04 600rr front end. bigger brakes, 4 piston calipers, proper width rim for a 120 section tire, and fork preload, rebound, and compression adjustable.

< Message edited by michigan_313 -- 4/27/2008 10:46:48 AM >

(in reply to Gearloose)

Post #: 2

RE: 42 psi max fork pressure? - 4/27/2008 10:34:34 PM

Gearloose

Posts: 75
Joined: 9/12/2007
Status: offline

Thanks Michigan - 42 psi seems huge but it's what the book says. I only just got the manual - its definitely for the CBR600F1 - photos of a couple of the pages attached. I'd never heard of anyone going over 6 psi either, but wanted to check in case someone's tried it and found it good or bad.

I rebuilt the forks when I fitted the emulators - springs were within spec. The forks do occasionally bottom out when under heavy braking on bumpy roads.

Good point about the air pressure increasing with heat. Springs will be more consistent, for consistent handling.

Anyone else go any ideas?

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< Message edited by Gearloose -- 4/28/2008 12:36:13 AM >

(in reply to michigan_313)

Post #: 3

RE: 42 psi max fork pressure? - 4/28/2008 10:31:21 AM

michigan_313

Posts: 674
Joined: 2/24/2006
Status: offline

after you rebuilt the forks you used the stock springs, correct?

mine are rebuilt with heavier spring rates. you may or may not want to do this, but get heavier springs for your weight. this will stiffen or firm up the forks. find out what you weigh with everything on (helmet, jacket, boots, etc.). this will be sorta like preloading.

so for example, if you weigh 200 lbs w/o riding gear and 210+ w/, then get springs for 215-230 lbs. back when, i got mine between 150-160 lbs. worked out very well.

as for what the manual has printed, can't say i really would put 42 psi into the forks. my tank sticker says 6 psi max. either way, i recommend getting stiffer springs.

(in reply to Gearloose)

Post #: 4

RE: 42 psi max fork pressure? - 4/28/2008 3:53:41 PM

cbreric

Posts: 107
Joined: 8/3/2007
Status: offline

it actually says that the GAUGE will be damaged above that pressure, must be for the air gauge that came with the too; kit for the bike. thats my guess at least

_____________________________

'88 Hurricane 600. getting it back to the way it SHOULD be, one piece at a time!

(in reply to michigan_313)

Post #: 5

RE: 42 psi max fork pressure? - 5/22/2008 4:37:38 PM

danothedinosaur

Posts: 4
Joined: 5/6/2008
Status: offline

It says there in picture 2 "0-40 KPa" (not psi) or "0 - 6 psi".

I think the 42 psi reference on the 3rd picture is the maximum pressure the line to the guage should have.

(in reply to cbreric)

Post #: 6