Chassis flex & dampers

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10-16-2008, 04:33 PM
rsportvolvo

Chassis flex & dampers

I wanted to start a new thread on this subject so as not to thread-jack the x-brace thread.

The debate was IT cars having so much chassis flex that it renders a good damper useless.

Here's my stance:

With a properly design and fabricated roll cage a chassis can be stiff enough to benefit from better dampers (i.e. driver can feel damper adjustments). Said design would need to include a decent chassis to begin with (why I'm using a Volvo 240, both my E30 M3 and E36 M3 a flexi-flyers in comparison), a roll cage that picks up most load points (i.e. suspension mounting points), and proper fabrication techniques. With some thought, stealing with your eyes (look at current designs from top engineered cars) and attention to detail one can have a very good chassis. An engineering degree helpful here, but not required to do this well.

The dampers need not be the latest 4-way Moton/JRZ/Penske/etc. designs. Most of the IRL teams use a head valved dual bleed Penske damper (VBP-45) along with the new A1 GP cars --> completely IT legal! The adjustments allow cheaper tuning in the long run, but most folks never even mess with the adjustments making that feature a complete waste. With Koni Challenge requiring only Koni dampers for 2009 and one could get Koni 28 series dampers for a reasonable price. The Koni 28 series is a very good damper (used by the Prodrive run Aston Martin DBR9's) in the right hands (as with most modern dampers).

Here's a list (not exhaustive) of decent IT legal dampers that hands down beat the standard Bilsteins and Koni street twin-tubes many folks use. Most of these dampers are user rebuildable with some special tools and require nitrogen charging (periodically depending on the leak rate).

Afco R series - 0 adjustments
Afco T2 series - 1 adjustment

Bilstein SN - 0 adjustments
Bilstein ASN - 0 adjustments
Bilstein ASB - 0 adjustments
Bilstein BG - 1 adjustment
Bilstein BGT - 1 adjustment

Carrera GP (RIP, good if you can find them)

Fox - 0/1/2 adjustments

Ground Control Advanced Design - 0/1/2 adjustments

JRI - 0/1/2 adjustments (Jeff Ryan's new damper company)

JRZ RS - 0/1/2 adjustments

Koni 28 series - 2 adjustments
Koni 30 series - 2 adjustments

Öhlins STJ - 0 adjustments
Öhlins MCJ - 1 adjustment
Öhlins WCJ - 1 adjustment

Penske 7100 - 0/1/2 adjustments
Penske 7300 - 0/1/2 adjustments
Penske 7400 - 0/1/2 adjustments
Penske 7500 - 0/1/2 adjustments
Penske VBP-45 - 2 adjustments

QA1 6x series
QA1 82 series
QA1 92 series

Sachs - 0/1/2 adjustments

If you know of anymore IT legal 'modern' dampers please post.

**Many of these dampers can be made into struts without too much work.
10-16-2008, 05:32 PM
JimLill

not sure you can always pick up "most suspension load points" with a IT legal cage.
10-16-2008, 08:12 PM
tderonne

Three points:

Don't forget tires are springs too. Spring rate is in the neighborhood of 1200 pounds/inch. The higher the spring rate (and/or wheel rate depending how you want to look at it) the more the tire rate comes in to play. 1200 pound wheel rate on the back of that trick FWD World Challenge car? 50% of the total real spring rate is uneffected by the rear dampers!

And, in my opinion (and many others - but lets not not start a debate) the suspension load paths you want the cage to reinforce are the spring perches. And in the path of the spring axis.

As far as dampers go, more to the point of this thread, how about some used whatever from all the teams that weren't using Konis in the Koni challenge series? Dynamic/Multimatic stuff comes to mind, lots of Mustangs will be ditching that stuff. It's essentially all custom, it can be completely taken apart. You could build just about anything with it (if the length and travels are close I guess).
10-16-2008, 09:12 PM
rsportvolvo

Quote:

Originally Posted by tderonne

Three points:

Don't forget tires are springs too. Spring rate is in the neighborhood of 1200 pounds/inch. The higher the spring rate (and/or wheel rate depending how you want to look at it) the more the tire rate comes in to play. 1200 pound wheel rate on the back of that trick FWD World Challenge car? 50% of the total real spring rate is uneffected by the rear dampers!

And, in my opinion (and many others - but lets not not start a debate) the suspension load paths you want the cage to reinforce are the spring perches. And in the path of the spring axis.

As far as dampers go, more to the point of this thread, how about some used whatever from all the teams that weren't using Konis in the Koni challenge series? Dynamic/Multimatic stuff comes to mind, lots of Mustangs will be ditching that stuff. It's essentially all custom, it can be completely taken apart. You could build just about anything with it (if the length and travels are close I guess).

Good point on tires.

Dynamic makes very nice dampers. The only issue is that remote reservoir dampers aren't allowed and you would have install the canister dividing piston in the main damper housing. Also used damper's are not always that cheap, especially the higher end ones.

Another good point brought to my attention by EXE-TC's owner is the damper has to move to work (master of the obvious, but is it so obvious?). So if you are running high spring rates a nicer damper is worthless. The suspension doesn't move enough to utilize the damper as a tuning tool.