Fork air pockets?

Would Roadholders, no matter their internal guts, benefit by controlling the over head air pressure spring or volume?
I just came across MX bike adaptation that turns handle bars into air tank that connects to both fork tops. Said to help fork action somehow. They fill before a run but Peel could change it on the fly. Why would I want to? Last report on this said Roadholder pump away their air pocket, hm.

hobot

Long time ago, beginning of the eighties, I fitted air valves to the top nuts, to increase height of the bike. This because it was to go through off-roads with a lot of luggage and spare fuel (jerrycans left and right of the motor). It did work, cannot remember how long the seals held it. Extra volume in itself would mean lower air pressure rise, I guess? That is assuming no restiction of some kind.

My RZ is suppose to run 7psi in the conventional forks. My KTM is suppose to be bled to avoid being pumped up, ( Upside down forks). The air volume acts as final damping before bottoming.

Also note air chamber refers to the space not filled with fork fluid. So air chamber size is used to convey oil level measured down from the top. The smaller the chamber - more oil - less travel. Really has more to do with long travel suspension.
What will extra volume/pressure get you on the Commando, my guess, not much. If you want better action I would look at the cartridge style internal conversions or better yet forks from the last decade. Say conventional R-6 forks.

Thanks for the educational confusing feedback. I'm also confused on which I like best, pavement flings or off roading zings on Commando.

I guess it depends on whether the fork type pumps up pressure like MX bikes or pumps it down like Roadholders. Roadholders were found to pump air PSI down.
I played with fluid levels til I got hydro lock 1/4 mile away from shed to almost get tossed over suddenly as I went over 10ish mph into counter steering zone. Barely ridable even below 10 mph on lumpy surface. I assume it took some bump pumping down to collapse to incompressible fluid.

I love the use of motorcycles as cargo mules over rough stuff so is main part of my ponder on this. I have not experienced cartridge upgrade in Roadholders but have in my SV650. At this point with excessive testing of my own mods I can't conceive desiring better fork action or travel and end stops, nor have I much respect anymore for Race Tech drop ins even though it did help my SV nicely, it still can't handle what it takes to send me to the orbits i get on obsolete Ms Peel.
On or off road. I'm withholding opinion till I spend and install John's hi end compete kit, dampers to bore restorer.

Can't get best out of fork if chassis is not tamed nor visa versa.
Still might be neat to hot shot air pressure at some brake lever pressure to help panic brake nose dives. Is braking ability considered to improve corner handling or is it just to keep form going around too fast for corner cripples? SURE is on every thing I've tired but you know who.

hobot said:

... Is braking ability considered to improve corner handling or is it just to keep form going around too fast for corner cripples? SURE is on every thing I've tired but you know who.

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On poorly suspended bikes, (not at race speed and on good traction surface), the use of the front brake through the corner is to take up some of the travel to keep the bike settled.
When pushing traction limit, tighter corners require lower speed to avoid overcoming tires, braking and corner forces on tires and suspension are kept constant by braking then releasing as corner force take over.
Try attacking tight twisties on a 300lb, 60hp bike with a foot of travel and you get an idea of what's going on. Travel, traction, geometry changes, etc. make for an interesting and fun ride. Might scare the sh*t out of some and I have had a few pucker moments myself but definitely worth a go for the experience. Give it a try. We might see a hillbilly Peel jacked high to the sky after. All the better for being able to see what's over the next rise.

slimslowslider said:

Extra volume in itself would mean lower air pressure rise, I guess?

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That's correct: http://en.wikipedia.org/wiki/Ideal_gas_law aka pV=nRT.

If the temperature stays the same (which it doesn't but the effect can be neglected) the IGL leeds to p_1 * V_1 = p_2 * V2 -> p_2 = p_1 * (V_1 / V_2) with "1" being the uncompressed and "2" being the compressed state. Obviously V_1 is V_2 plus the delta V_d which is determined by the fork travel and aera and doesn't depend on the total volume. Therefore the larger the total volume is the smaller the effect of the delta becomes.


Tim

It's an interesting discussion, but that's all it is until someone comes up with some roadholder seals that are airtight. Standard ones certainly aren't and as far as I know there's only Leakproof as an alternative and there's been a lot of talk about excessive stiction with those.

Interesting, if questionable feedback to apply to Peels hobot Roadholders.
I am mounting a child's passenger seat on front fender for infants and cargo so some sag compensation might be desirable if acted just to increase spring progressive rate. Kids can just put hands over eyes for bugs grit and zoomed in vistas.








The Roadholder air sealing issue is a booger I'd not considered - until John reported the PSI pump down instead of pump up as MX forks and mention of it here again. Still Peel has air station and 1/2 gallon reservoir to make up for some wastage. If fork action varies w/o pilot being aware of it, and what I've found is there's often a threshold that creeps up un-noticed to suddenly surprise ya. Might be worthwhile to have constant regulated pressure fed in. A pop off valve could blow off to prevent too high of PSI spikes. Might feel like stiff springs taking on full impacts but don't rebound back with same force as compression to bother bike control.

May tap bars anyway for extra volume over all and to have capacitor like air supply up close to the fork air muscles and valves.

As to Gravel Travel on light bike/pilot combo with torque response enough to break loose at will, I'll take a lifted unloaded floating front tire every time over the low loaded front of road racers. Corner cripples are like that though, just can't handle real power planting when leaned so might as well unload rear while trying to avoid up-settling bike by using brakes or forward weight shift, but for sure nil power before apexes, pashaw, very dangerous with threshold creeping up un-noticed to suddenly surprise ya, Not on Peel thankyou.
I've nil respect for the elite performance of cycles in 45+ leans, I've total awe of the racers who try to control those dangerous beasts, but no more for me as so little extra thrill for such spikes in risks, none of that for me and Peel thankyou.


I get annoyed by the reflex response that Peek seeks-needs any further handling improvements, beyond tank slosh foam and ground effects bleeders.
NOT ON YOUR LIFE!
Main thing I get out of the feedback is there is no real danger down side to messing with air pocket as long as there is still some air pocket left.
This is for rump linked Ms Peel, not ordinary handling bikes, so fork improvements is not needed to solve any thing I have detected as a hinderence maneuvering way harsher than seen in video unless pilot tossed off saddle. If ya pay Close Attention you will see bike self correct at ridiculous accelerations - tank slapping to hi side flings, too bad them hot shot bikes can't take any throttle on purpose to induce and ride like that at will getting max hook up at least point of apex traction.

Just class me from another planet along with Bob Patton hands off rough road surfing, until you too experience the wonders of rump controled isolastics.

It's sort of a solution to a problem that doesn't exist . . . . that is, if you want more spring, then get a different spring.

That said, if you want to add spring without buying a spring, then yes, you can simply add a Schrader valve to the top nuts of a Norton (and somehow drill a small passage off center to get the air/pressure past the damper rods?) and put, say I dunno? 10 psi? of air in there. But . . . . then the rate of pressure rise in those small diameter forks will be too high, you might hit "air bind" before the forks' maximum travel is reached. You can experiment with oil level too and that will affect the rate of rise dramatically. Then too, it is VERY hard to set and re-set and experiment with the psi when you are dealing with such a small volume; easy to overfill and hard to bleed down slightly.

On the other hand, if you add a reservoir, such as the handlebars, to increase the available volume, then the rate of rise will be slower and it will be easier to set the pressure. Another bonus is that, since both forks "tee" into the handlebars, then the forks' internal air pressure will be balanced.

The Roadholders, bless them for their perfomace back in the day, but now, compared to other front ends . . . . . well, they need modifications. Mine are oversprung and clanky.

Thanks for helping me wrap my mind around air function in fork action. You are right about it being, a solution in search of a problem, as concerns Peel's simple modified forks ala the kit Greg Fualth provides. Two features beyond what Greg supplies are adding to my RoadHolder joys, custom 4 rate progressive springs [plus air pocket] and a robust RGM fork brace-slider-bush extension.

Yet seeing MX bars air tank-hose kit for rough riders and reflecting on the pump down phenomena reported by John has made me wonder if I've encountered-induced this a couple times for scary surprise. It felt and came on suddenly one corner fling to the next, very similar to when I'd over filled forks and got 1/4 mile away before forced into tippy toe ride back to drain 10-15 ml out. Locked forks tend to fling opposite direction expected by surface bumps or in-putted by pilot to aim where intended. So my concern is pushing beyond phase 2 handling and having fork action change w/o me noticing until suddenly does something un-expected. I don't think normal phase 2 - leaned counter steering on highway or tracks is enough to cause Roadholders to pump down enough to be noticed.
Spirited phase 2 riding into corners does not compress forks but extends them.

Peel has two holes in each Al fork cap to fill-vent, so already have air ports to tap. Peel is set up to supply air to front anyway, so may try it along with other 'secret' air features. Peel had decent resistance to fork dive trying to do stoppies, and apparently with the extra stability of the rear linkage, was able to ride locked front a few bikes lengths varying the brake pressure trying to get best grip to lift rear to show. W/o the rear link back was almost impossible to keep in line with the front. If I was not delicate increasing brake force I'd get lifted out of seat to toss butt over the forks, no matter how I prepped against that. So besides nil respect to other bikes corner ability I also don't much respect their ability to slow up well either.

On the other hand i may have to tap handle bar volume as OIF pressure vent
baffle. I've heard of head lamp oil leaks from oil gauge there, but Peel may be 1s to report leak out the bars - well maybe not as folks in past have routed hot oil to bars to warm hands.

I added air valves to the top of my forks one day in a fit of over inventiveness.

I added about 8 PSI and the ride did improve slightly. A bit firmer and the damping seemed a bit better over bumps.

I checked the pressure an hour later and it was back to zero. Seems the forks are not even close to being air tight.

Acknowledging your interesting report Don. Got me wondering more now. Isolastic Commando are the most prone to fork-chassis hinge state on long sweepers by increasing speed or steady state just below hinge state, gives time for the resonance or rear patch slapping the front mount jiggling forks to built up. What I found on non-linked Cdo was everything seem fine till some seconds then got to wiggling more and more till back off or else. Maybe thats the last air pump down and helping to over whelm iso stability. Also noticed on tri-linked Peel hobot Roadholders, was noticing more fork blurring tire scuffing action after a few good peg scrap chicane turns. Maybe its last air going away. When traction is at very limits every little bit of stability helps. Maybe there is something to be gained keeping a stead head of air in there. At least if letting hair out on pavement or off road. If forks hit a hard stop while maneuvering it tends to fling front or bike way over unexpected. Will be awhile before attempting, so don't hold breath.