Matt's pursuit of Suspension and wheels

[shogun32]

Do you think you're seeing 100-300 in/sec damper shaft speed in a Mustang? How are you measuring this?

no, those are not mustang (or even car) related. That said, a 1" bump at 50mph is about 150 in/sec at the tire, and the shock would see about 1/2 of that (MR=0.72) so 75 in/sec.

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[Norm Peterson]

Wouldn't it be less than 37 ips due to tire compliance (at minimum)?


Norm

 

[TeeLew]

no, those are not mustang (or even car) related. That said, a 1" bump at 50mph is about 150 in/sec at the tire, and the shock would see about 1/4 of that (MR=0.5) so 37 in/sec.

OK, I was hoping you didn't think you were seeing those numbers in a car. About the only auto related thing that will be operating on that order of magnitude is a Trophy Truck on it's way to Baja. Even the example you've mentioned is not really realistic. There just isn't enough energy to accelerate X mass at that rate. Tire deflection and chassis motion will reduce the numbers you've presented significantly (probably 50%, though I hesitate to give an exact amount).

Most cars don't see individual events over about 25 in/sec and even that is on the high end of things. The vast majority of time, car dampers move at <~10 in/sec. Handling events come in about 1/2 of that or less.

As far as dyno tests go, by the time you've gotten to 10 in/sec on most dampers, they're usually on the linear portion of their curve. Unless you have some blow-off shaft or something along those lines, in which case, you'll get a slope change at some point elevated point in the curve.

 

[shogun32]

I finally had the bright idea to film the EB (pro-Active + sport progressive) hood bouncing around. Will post the GT (pro-action + dual-rate) in a little bit. More videos on my channel.

 

[Norm Peterson]

You need a steadier camera mount, like something sticky-mounted to the top of the dash. Can't separate the hood bounce from the camera shake.


Norm

 

[shogun32]

alright GT vids are up for contrast. And I put some new EB up that I braced the camera against the wheel. And one that was stabilized with post-processing.
https://www.youtube.com/channel/UCvpR7IECFaP1XvZWSdoVW7g/

You have to watch carefully to notice the differences between the two. What should be fairly obvious is that the EB (green, actives) kicks upward and significantly more so after hitting a bump than the GT (blue, adj actions)

 

[Norm Peterson]

A lot better.

The EB's struts definitely look like they could be firmer in rebound. Am I also seeing where low speed rear bump damping could be a bit firmer?


Norm

 

[shogun32]

some extra comp in the rear might be helpful, yes. But the much bigger problem is rebound at both ends.

 

[shogun32]

added 1/8 turn to front Steeda pro-Action (might be too much)
added 1/4 turn to rear (need a tad more?)
Approaching less than 1/4 turn from fully closed at both ends.

Ride is improved esp at the back. These DR springs are just too damn stiff up front to follow contours properly. They are wonderful if you want very little nose drop when you stand on the brake pedal though.

Trying to damp that 800/1200 rear is troublesome. Suspect 800/1000 would have been better choice with 1/4-3/8" more stroke to the 800 section. It does G-out pretty good - you can feel the "support" when the rear is driven hard into the ground.

 

[Brian@BMVK]

added 1/8 turn to front Steeda pro-Action (might be too much)
added 1/4 turn to rear (need a tad more?)
Approaching less than 1/4 turn from fully closed at both ends.

Ride is improved esp at the back. These DR springs are just too damn stiff up front to follow contours properly. They are wonderful if you want very little nose drop when you stand on the brake pedal though.

Trying to damp that 800/1200 rear is troublesome. Suspect 800/1000 would have been better choice with 1/4-3/8" more stroke to the 800 section. It does G-out pretty good - you can feel the "support" when the rear is driven hard into the ground.

Lipstick on a pig....

 

[shogun32]

Lipstick on a pig....

grrr, quit reminding me!

 

[TeeLew]

some extra comp in the rear might be helpful, yes. But the much bigger problem is rebound at both ends.

Don't be so sure. You can't just increase rebound until you get a nice ride. Quicker response? Yes, if that's what you need, you can get a bit f that, but increasing rebound damping will make for a rougher ride and reduce mechanical grip.

There seems to be a group hesitancy to increase compression damping, which, to me, is unfounded. If you have the ability, trade some rebound clicks for compression (particularly low speed) and just see what you think.

 

[shogun32]

You can't just increase rebound until you get a nice ride.

the comment was regards to teh pro-Active which is unadjustable. After a bump it would oscillate instead of 1 or 1.5 cycles and done. It's underdamped for anything over stock spring rates. When driven hard it's less objectionable. It's the moderate effort or daily to-fro that is annoying.

I am firmly of the camp that high-speed comp should be very low. The only place you want any decent compression damping is up to about 2" a second. Anything over should be a "flat" line. If high-speed bumps are upsetting the chassis or feel anything more than a muffled whomp, the valving/piston orifice/oil viscosity is just plain wrong.

Racers may feel different. They apparently have no objection to their cars getting tossed around and going airborne. I believe in working the suspension, not the tire carcass or chassis.

 

[TeeLew]

Be careful with absolutes. It's a spring/mass/damper (ok, a little more, but when simplified) system. The mass is fixed. The spring stiffness and damping needs to match the road input. Regardless of the application, you want to reduce the contact patch load variation to improve grip and reduce body accelerations to improve ride. Sometimes that means reducing damping & others it's a matter of increasing it. It's all a matter of the type of input and how that relates to the spring stiffness.

 

[shogun32]

Unfortunately the dyno graphs FA posts are not 'real' in that they do not reflect what the S550 units have been dyno'd at.

Well now i have actual sweeps for the front. Though as you can see they show no hysteresis which is rubbish. I took one look at those curves and sent them an email to change a few things but that didn't go over too well. So I'm going to run them per their default valving and if I'm not satisfied I'm going to go pay them a visit in person. I guess when we do the 2/3-way R&D I will be in a better position to insist on valving revisions, if I don't just do it my damn self.

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