High shaft speeds are road induced, low shaft speeds are driver induced. That is a generalization but the basic reason that being able to separate controls for low and high shaft speeds is desireable.

 

On the shock dyno, is the "OEM" line the standard damper or the suspension package Bilstein?

 

But any shaft speed on rebound is set by the spring right? I can see how deeper in the stroke the wheel will want to return faster. I totally get that how sharp or tall a bump is will cause compression speeds to change, but it can only return as fast as the spring pushes it back down. You only get a certain amount pushing down once you crest the bump.

Dont mean to derail too much here. This is obviously a very focused thread. Just more research on my end needed I suppose. Growing up riding dirt bikes I'm quite used to 3 ways. Now you got me thinking about 4 ways

 

I'm a software guy, not an ME, but here's my understanding. Think about what happens over the bump. The wheel moves up, some of that motion translates into compressing the spring, some into moving the body upwards. Since the body weighs a lot more than the wheel, most goes into the spring.

Now the wheel crests the bump, and the wheel is no longer moving up. The energy in the spring pushes the body and wheel away from each other, with the wheel moving a lot faster because it's lighter.

So yes, the wheel will only go down at fast as the spring and gravity will pull it, but that's plenty fast enough to make a difference in driver vs road induced rebound because it is light compared to the body.

--Ian

 

OEM Showa, not Bilstein.

 

Study what Emilio said. Make sense out of it. Then you will understand.

 

Mazda put a belly pan and an 8mm Allen key for the oil drain plug.

They've ruined the Miata forever.

 

high speed rebound adjustments are pretty much useless in my opinion. Maybe an F1 team can find gains using them, but for the average consumer it just adds confusion, cost and another hole for the damper fluid to leak out of.

I played with some of these (4 way adjustable mountain bike shocks) for days and couldn't really tell wtf the high-speed rebound was doing. Smart to leave it off the shock IMO.

 

Yup. Very rare situation when you need more high speed rebound in a sports car. At higher shaft speeds, the bulk of the energy acting on the damper is just the stored spring energy and unsprung mass.As those remain effectively constant (inertial effects notwithstanding) the damper can be valved
to deal with them without requiring further adjustments. Driver input and road surface are out of the picture. In off road suspensions, high speed rebound can be tuned to change how the vehicle performs near full droop. I see that high speed rebound adjustment employed in rally cars and off road trucks/buggies.

NA/NB and also ND Xidas for example, have digressive pistons that bleed off most of the high speed rebound. This allows an adjustable low speed segment where driver input, roll moment (grip) and vehicle weight are highly variable and
often require tuning. The high speed portion is tuned by yours truly with a range of wheel assemblies. On a vehicle with much heavier wheels/tires, less or no digression is needed. On the NA/NB at least (low unspuing mass), the only way to get the suspension to work without digression is to have too little low speed rebound so that the entire rebound side is weak. This has the added benefit of being able to pressure balance more easily and also reduces hysteresis. Problem is handling ultimately suffers with race tires when there is inadequate low speed rebound so we don't do it. Typically, we'll focus on a typical track setup but also test a super light and also heavier wheel setup just to make sure we don't uncover any anomalous behavior. The Tecna's for example, have been carefully dialed to work with OEM weight wheels/tires but still cope with the now standard 225/45/15 EHP on 15x9 6UL. At the relatively low price point they're targeted for, that has proven a challenge. Many prototype valving sets rejected.

So yeah, decisions made for function reasons, not cost or bling factor.

 

So what you are saying is Tecna's are still being worked on slowly and might one day become a reality for the consumer?

 

I sure hope so. Please don't let them go the way of the rev9 or whatever it was you were going to name those wheels.

 

take my money meow?

 

That has always been the case, never stated otherwise. We just don't publish ETA, price, spec or anything else. We'll announce them when they are in stock and ready to ship. I only mentioned here to illustrate how that particular area of the damping curve receives specific attention in relation to it's intended usage.

 

After this statement I am surely going to wait and give my moneys to you when the time comes.

 

Just give me 2 weeks advance notice on the Tecna's so I can sell my budget Bilsteins.

 

No problem. Consider this thread your 2 year notice

 

I'll be sure to backorder your set.

 

well played

 

Anyone have reliable lap times that ND's are running? Actually being driven to the limit on 200tw tires? I'm curious how they stack up, and haven't seen any at our tracks around here yet. If so, mods list would be helpful.

Has the ECU intrusion/limitations during constant track use been permanently dealt with? I've been following this thread pretty close for the last year and don't recall updates on these items.

 

The car is still new enough that there are very few that are both well prepared, tuned properly and driven by an advanced level pilot. That said and given the same level of mods, the ND is quicker than any other year Miata, the FRS and close to an S2000.