Oil level air gap tuning gen 3 - Kawasaki ZX-10R.net
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post #1 of 14 Old 06-11-2017, 03:39 PM Thread Starter
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Oil level air gap tuning gen 3

Just finishing a fork rebuild. I'm wondering what is the max i can adjust the oil level/air gap to stiffen the damping.

I the 10cc increment is the norm but whats max before I put seals in danger
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post #2 of 14 Old 08-22-2017, 04:10 PM Thread Starter
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In case anyone ever thinks about this one - it works - just a tiny amount of fluid makes a huge difference and it's very easy to to do .
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post #3 of 14 Old 08-22-2017, 04:54 PM
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Air Spring does not stiffen the damping, the valving does that. The Air Gap will not come into play until the very end of the stroke and is basically an extension of the coil spring rate although much more progressive.

If you are blowing through the stroke then you need more compression damping with the valving.

Additionally if you decrease your air gap by adding more oil then your rebound damping will suffer for it on larger bumps as you now have more spring force to counter as the forks extend

Last edited by LDH; 08-22-2017 at 04:57 PM.
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post #4 of 14 Old 08-23-2017, 01:46 PM
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As LDH mentions airgap works in conjunction with the main spring, not damping. As to the max you can put in, there really is no number. But again like LDH mentioned the higher you go, the more harsh it will feel. Generally for a street bike we'll stay somwhere around 170 to 190mm range. For racing it varies but we always go as low as possible, 190mm +.

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post #5 of 14 Old 08-24-2017, 09:38 AM
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Quote:
Originally Posted by evallarta1 View Post
For racing it varies but we always go as low as possible, 190mm +.
Eevallarta, what about race cartridges like DDS, RDS or Ohlins RT, do you generally try to stay at lower side of factory spec window too?

Gen4 race: high spec.
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post #6 of 14 Old 08-24-2017, 09:46 AM
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I know you didn't ask me, but I will throw this out there. It depends on the racer and the type of cartridge. When guys are "racing" at 15 seconds off the lap record they have completely different requirements from their suspension and geometry than those that are at or near the lap record. The faster they go the more unique their riding style and requirements are which means their set-up is more finely tuned.

Having said that, Generally YES less & less oil is used, but usually in conjunction with more coil spring rate and more damping. They want the most linear travel possible, but they also have to be able to support the front end to maintain geometry at all points on the track whether trailbraking to the limit or on the gas driving out at 100% throttle. Anyone ever notice how far Rea and Sykes front ends dive on braking on their current ZX-10RR? You have to really have your set-up nailed to pull that off without bottoming out which would be catastrophic.

With conventional carts at proper track pace 20-40mm less than spec is pretty routine, but with gas carts some of them have just enough oil in the actual fork tube to provide lubrication to the fork seals and that is about it.
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post #7 of 14 Old 08-24-2017, 10:15 AM
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post #8 of 14 Old 08-24-2017, 05:02 PM
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Quote:
Originally Posted by LDH View Post
I know you didn't ask me, but I will throw this out there. It depends on the racer and the type of cartridge. When guys are "racing" at 15 seconds off the lap record they have completely different requirements from their suspension and geometry than those that are at or near the lap record. The faster they go the more unique their riding style and requirements are which means their set-up is more finely tuned.

Having said that, Generally YES less & less oil is used, but usually in conjunction with more coil spring rate and more damping. They want the most linear travel possible, but they also have to be able to support the front end to maintain geometry at all points on the track whether trailbraking to the limit or on the gas driving out at 100% throttle. Anyone ever notice how far Rea and Sykes front ends dive on braking on their current ZX-10RR? You have to really have your set-up nailed to pull that off without bottoming out which would be catastrophic.

With conventional carts at proper track pace 20-40mm less than spec is pretty routine, but with gas carts some of them have just enough oil in the actual fork tube to provide lubrication to the fork seals and that is about it.
Thank you for good input.

Yes have noticed how WSBK riders compress forks and they STAY compressed in bottom 1/4th stroke while transfering brake load to cornering lean load.
Guess tuning that zone is very important to them.

Just looked up that K-tech recommended level settings for RDS (conventional) and DDS (pro level) are 145mm and 185mm respectively. Rod diameters (defining airgap volume) are about same, but still 40mm difference!

Gen4 race: high spec.
Suzuki GSX1300R Hayabusa 2013: stock.
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post #9 of 14 Old 08-28-2017, 10:31 AM
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Quote:
Originally Posted by LDH View Post
I know you didn't ask me, but I will throw this out there. It depends on the racer and the type of cartridge. When guys are "racing" at 15 seconds off the lap record they have completely different requirements from their suspension and geometry than those that are at or near the lap record. The faster they go the more unique their riding style and requirements are which means their set-up is more finely tuned.

Having said that, Generally YES less & less oil is used, but usually in conjunction with more coil spring rate and more damping. They want the most linear travel possible, but they also have to be able to support the front end to maintain geometry at all points on the track whether trailbraking to the limit or on the gas driving out at 100% throttle. Anyone ever notice how far Rea and Sykes front ends dive on braking on their current ZX-10RR? You have to really have your set-up nailed to pull that off without bottoming out which would be catastrophic.

With conventional carts at proper track pace 20-40mm less than spec is pretty routine, but with gas carts some of them have just enough oil in the actual fork tube to provide lubrication to the fork seals and that is about it.
Even for regular trackday riders who are just starting out we always run as low as possible. Like you mention we have to take spring into account but ultimately we run as low as we can go. We've done back to back testing and everyone can feel the difference. The one exception to the rule is street riders. It's not that they wont benefit from the lower oil level, it's just there are too many variables on the road to chance not having extra bottoming support.

While LDH and I have two different thought processes on this, neither one is wrong. It's just different ways to attack a problem.

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post #10 of 14 Old 08-28-2017, 10:55 AM
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Originally Posted by Carlos76 View Post
Thank you for good input.

Yes have noticed how WSBK riders compress forks and they STAY compressed in bottom 1/4th stroke while transfering brake load to cornering lean load.
Guess tuning that zone is very important to them.

Just looked up that K-tech recommended level settings for RDS (conventional) and DDS (pro level) are 145mm and 185mm respectively. Rod diameters (defining airgap volume) are about same, but still 40mm difference!
In this particular instance you are comparing apples to oranges, let me explain. The RDS is a open bath cartridge, so oil runs from inside the cartridge to the outside. In order for this to work the entire cartridge MUST be submerged in oil otherwise air will be sucked into cartridge and damping will be killed. In addition the oil level is setting air gap. So for an open cartridge (Ohlins 30mm, K-Tech RDS, GP suspension) the oil level serves two purposes, air gap, and making sure the cartridge is fully submerged.

The DDS cartridge is a fully enclosed pressurized system. What this means is the oil never leaves the cartridge and always stays full. This allows you to run extremely low oil levels without introducing air into the cartridge. So in this case when your setting the oil level you are ONLY using it for air gap unlike open bath cartridges.

You mentioned rod displacement, in this conversation rod displacement does not have an effect like you would think. In a pressurized system the rod displacement will not change the oil level height in the cartridge. In open bath like the RDS it would be minimal level, not enough to even worry about.

EXAMPLE - Anthony West this weekend at PittRace was on K-Tech DDS and Dave Anthony was on K-Tech RDS. We wanted to run 210mm on Anthonys forks but could not because we were too close to the top of the cartridge, so we ran 190mm. On Anthony's bike we have no issues so we can run 210 to 220mm all day long without any issues.

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