Remote Reservoirs?

[rsportvolvo]

correct, they just released those, what 4 months ago?

they have a twin tube double adjustable, and a mono-tube single adjustable non-RR

Nah, it's been at least 18 months as I spoke with them about it at the PRI show in 2007 and they were available then. When they became available is not the point. They are currently available and a good option for the IT crowd. Some Pro teams even run these twin-tube JRZ's on occasion, that is from the JRZ USA reps.

 

[jimmyc]

Nah, it's been at least 18 months as I spoke with them about it at the PRI show in 2007 and they were available then. When they became available is not the point. They are currently available and a good option for the IT crowd. Some Pro teams even run these twin-tube JRZ's on occasion, that is from the JRZ USA reps.

hmm interesting i thought they became available first of 09...


I have a set of the mono-tube single adjustable, as soon as my car is back together im going to do some testing with them.

 

[Tak]

Damping tuning in the lower shaft velocities is more beneficial. High speed adjustments are good for curbs and other large imperfections (overly simple examples). The damper spends most of its time in the lower shaft velocity ranges. To back my arguement up take a look at a damper histogram. It looks like a flattened bell curve (er, should). So having the low speed adjustments is what you want. Why have an adjustment that effects 25% of your overall damping?
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Bottom line is if you don't corner balance your car regularly and change setups at the track you're wasting time and money on adjustable dampers.

RSportVolvo-
I agree with your bottom line, but disagree with your reasoning on the high speed/low speed part. Recall that high speed or low speed refers to the damper controlling either chassis movement (low speed) or wheel movement (high speed). The four combinations are:
1) high speed compression--bumps or kerbs.
2) Low speed compression--chassis roll, loaded side.
3) Low speed rebound--chassis roll, unloaded side.
4) High speed rebound--extending the tire toward the ground.
Every DA shock I have seen or looked into adjusts high speed compression and high speed rebound. The strategy for adjustment is to increase compression damping until the car 'skates' on bumpy surfaces, then back off two or three clicks. Rebound is increased to control the rate of body roll--and to adjust turn in / exit understeer/oversteer. Managing bumps and kerbs is vital to sustained traction--in my opinion it is the most important adjustment on a damper!
There is a great description of shock tuning at http://www.koniracing.com/rrtuningguide.cfm
To your point on the damper histogram, yes, high speed is a smaller percentage of the histogram. But on the track, every time you are at the traction limit, that high speed portion of the histrogram really matters!!!
Here is a link that shows a few dyno curves for adjsutable shocks--see that the high speed is where the adjustment is happening.
http://farnorthracing.com/autocross_secrets6.html
(The curves from the koni site require downloading a 5MB pdf...).

Enjoy
Tak

 

[rsportvolvo]

Tak,

I inserted my responses below.

RSportVolvo-
I agree with your bottom line, but disagree with your reasoning on the high speed/low speed part. Recall that high speed or low speed refers to the damper controlling either chassis movement (low speed) or wheel movement (high speed). The four combinations are:
1) high speed compression--bumps or kerbs.
2) Low speed compression--chassis roll, loaded side.
3) Low speed rebound--chassis roll, unloaded side.
4) High speed rebound--extending the tire toward the ground.

Depending on what you define as low speed and high speed, you are agreeing with me (we're saying the same thing). Please define what you mean by low speed and high speed, i.e. specifc ranges with numerical values.

Every DA shock I have seen or looked into adjusts high speed compression and high speed rebound.

Most low speed adjustments will affect the high speed section of the curve. Did you look at the low speed ranges?

The strategy for adjustment is to increase compression damping until the car 'skates' on bumpy surfaces, then back off two or three clicks. Rebound is increased to control the rate of body roll--and to adjust turn in / exit understeer/oversteer. Managing bumps and kerbs is vital to sustained traction--in my opinion it is the most important adjustment on a damper!

Your thinking is quite common. You're trying to use the damper to mask other problems. I prefer actual data (dyno plots). Please read through the Far North Racing link you posted as the writer and I are in complete agreement. You're take is not inline with ours.

There is a great description of shock tuning at http://www.koniracing.com/rrtuningguide.cfm

Good entry level primer, nothing detailed. Koni's 28 series manual is better along with Penske's and the Ohlins TT-44 manual (much more detailed.)

To your point on the damper histogram, yes, high speed is a smaller percentage of the histogram. But on the track, every time you are at the traction limit, that high speed portion of the histrogram really matters!!!

High speed damper velocites only occur if you're on kerbs and bumps. You can lose traction on smooth sections too. It's car/track/setup specific. I think you're confusing damper shaft velocity with peak cornering speed.

Here is a link that shows a few dyno curves for adjsutable shocks--see that the high speed is where the adjustment is happening.
http://farnorthracing.com/autocross_secrets6.html
(The curves from the koni site require downloading a 5MB pdf...).

Enjoy
Tak

That link proves my point and disproves yours. The author is stating that the key range to look at is the low speed range, specifically 3.0 in/sec and lower. The Penske speed range is only to 3.0 in/sec (Penske rebound sweep & Penske 8760 sweep), the Penske 8100 compression adjuster (auther states as being "junk") range is 10 in/sec and the Koni is in excess of 10 in/sec. You can only compare the same ranges, otherwise it's apples to oranges. I highly recommend you reread the Far North Racing link (all pages are a good read) and review what you posted. They are not inline with each other.

Thanks for posting the links and making me re-think my current position on damper tuning.

 

[Tak]

Hi David-
Not looking for an argument, just voicing a difference of opinion. And to a very large extent, yes, we are saying the same thing.
My definition of 'high speed compression' is anything higher than the chassis roll rate. 'high speed rebound' again, is anything higher than the chassis roll rate. Assigning a number is pointless, as it changes from car to car, and changes with spring rate and damper rate on the same car. Physically for the damper, high speed is after the knee, low speed is before it. I believe the knee should be above the chassis roll rate. I do agree with what the farnorth racing guy is saying--especially the .65 critical damping at lower damper speeds (to dissipate stored energy in the spring). Do keep in mind that he is talking autocross, where the lower average speed results in lower damper piston speeds over bumps. His cited data is from Topeka, that I have heard is fairly smooth (or was before a few winters), I've not been there.
Some real life examples of why I think adjusting high speed damping is more important
1) Thunderhill turn 2 (bumpy ~80mph 180 degree sweeper). With too stiff compression, the chassis bounces noticably (upsets my onboard video too) and the tires skate over bumps after the car takes a set. Soften the compression damping front and rear, the chassis smoothes out, and tires grip. Turn in feels marginally better with the stiffer compression. Stopwatch shows approximately 0.5 to 0.7 sec faster through T2 with softer compression all around. Are the bumps and undulations moving the dampers at 2, 3, 4, whatever in/sec? I don't know, I don't have that kind of data acq. The fact that the chassis doesn't bounce as much suggests that wheels are moving and the chassis is not--i.e. high speed compression damping lets the wheel come up without upsetting the chassis.
2) Turns 3 and 4 at Laguna Seca (smooth ~90 degree corners with dragons teeth apex berms). These corners can be done with either soft or hard compression damping equally--because the track is smooth. BUT, with softer compression, I can use ~6" more apex berm, and that makes it MUCH easier to keep tires out of the dirt on the exit. Especially useful when following someone closely, or being followed by a car that is not as compliant over the berms...

If I changed springs for each track, adjusting low speed damping might be more important...I don't know.

Good dialog, thanks for the pointer to the Ohlins setup page.

Tak