Thucydides

No, he doesn't used to valve for Shaikh. Bernie's been in business since 1975.

Hard to define similar, but certainly not the same.

JasonC SBB

Arrrrrggggh!! When will this myth ever DIE?

Thucydides

Jason, do you have a link to a really good scientific (non-mythical) explanation of the motions rebound and compressive damping control?

JasonC SBB

Sorry, I haven't seen one.

I'm basing what I know on a series of spring/mass/nonlinear damper simulations I did just for my own education. Most of what I've learned has since been corroborated by snippets I've seen in different places (e.g. shock absorber handbook, by Dixon), various papers on the web, and by discussions with FatCat.

IN this thread, I wrote long missives on part of the myth:
http://forum.miata.net/vb/showthread...highlight=myth
Read the exchange between me and "andris".

Thucydides

UPDATE:

I sent Bernie my shocks, he's gotten them, and he's just about to re-tune the valving in response to my feedback. Based on comments from this thread, from Bernie, and from others - and recalling that this is a hard driven street setup on stock springs - this past Monday I sent Bernie the following e-mail:

Good morning, Bernie.

I’ve been diligently studying dyno graphs for a number of Miata shocks, both OEM and aftermarket, designed for comfort verses performance, and both successful and unsuccessful setups.

The conclusion I’ve reached is that the more successful high performance but not brutal shocks suitable for stock spring rates fall into the following damping ranges:

Bump:
@ 5 in/sec approximately 75 lbs force
@10 in/sec approximately 100 lbs force

Rebound:
@ 5 in/sec between 175 and 200 lbs force
@10 in/sec between 200 and 275 lbs force

Some designs make a distinction in damping between the front and rear shocks; others do not or show only a minor difference.

I think I’d be inclined to try a setup with the rear shocks set to the lower end of the range, and the fronts to the higher end of the range, so they’d look something like this:

Front:
Bump @ 5 in/sec approximately 75 lbs force
Bump @10 in/sec approximately 100 lbs force

Rebound @ 5 in/sec 200 lbs force
Rebound @10 in/sec 275 lbs force

Rear:
Bump @ 5 in/sec approximately 75 lbs force
Bump @10 in/sec approximately 100 lbs force

Rebound @ 5 in/sec 175 lbs force
Rebound @10 in/sec 200 lbs force

I know it won’t necessarily seem this way, but the values I’ve presented probably average on the higher end of the scale and there’s room to go lower with regard to force.

I spoke with Bernie this morning and he's planning of working over the shocks early next week. He hasn't any objection to my proposed numbers, but coming from the race side of the suspension field these are lower numbers than he's accustomed to. If anyone would like to propose alternatives I'm all ears. In lieu of compelling alternative numbers we've agreed to go with what you see here.

miatauser884

iTrader: (11)

Sorry, double post

miatauser884

iTrader: (11)

Is there an average car velocity and weight that the "race" rates are used on? If there is, then you could probably create a scale between car velocity/weight and damping rate, and see if your values for the miata fall within the range.

Thucydides

Car weight and velocity are certainly a big part of the equation, but for a street shock I think perhaps the biggest concern is the nature - usually abysmal - of the road surface itself. Race tracks are far better maintained and more forgiving as far as the surface is concerned.

JasonC SBB

See m.net thread. Damper stiffness front to rear should be proportional to spring rates front and rear.