Qualify Your Suspension Vendor - 3 Added Advanced Questions to Ask (2/2)

#FCMElite #suspension #damping #automobile #handling
How to Qualifying Your Suspension Vendor, more questions to ask!

0:00 Shaikh Jalal Ahmad from Fat Cat Motorsports, going over a few more questions to consider asking a suspension vendor to gauge how well-optimized their suspensions may be for your needs.

0:22 Ask the salesperson at the dealership 'does this car have Flat Ride?'

0:49 VW original equipment suspensions are some of the best you're ever going to find (especially non-sport models!). Lots of intricate fluid dynamics going on.

1:03 Shaikh initially met Peter, a mechanical designer, on the Miata forum, who then introduced Shaikh to Phil Douglas, owner of Aftershocks Suspension. Both emphasized how important compression damping is to proper grip and also for performance.

1:38 Phil, a very adept rider and suspension builder, emphasized to me how 'compression damping is your friend.'

It is important and valid to gauge a vehicle's ride as an indicator of Quality. Many people's subjective experiences will lead to a consensus level of objective reality of what is 'good' or better.

2:24 What are the stiffness and length of your bump stops, front and rear?

3:17 Pitfalls of engaging bump stops too early, especially in the front, and the impact on handling consistency. Most aftermarket vendors will increase front spring rate to limit bump stop engagement BUT the front springs may become too stiff leading to pitch!

4:10 Handling consistency and bump stop engagement - an online conversation with Emilio from 949 Racing about the effects of bump stops.

6:40 Online comments suggested the Xida Gen 2 had a too-firm rear bump stop. Further confirmed via comments from an SCCA National-level autocrosser who contacted Shaikh for assistance in improved a Xida-equipped Miata he was co-driving. This experienced racers indicated the car was hard to control at the limit. Shaikh recommended using a soft density 58mm 'red' (cut down a bit). The follow-up was that the car was noticeably easier to drive at the limit with that single change.

5:23 Strange - why leave a bump stop in place if the car becomes too unstable? Brief overview of bump stop interactions based on stiffness.

6:00 The initial experiments Shaikh performed were limited to changing bump stop stiffness, length, and using 'packers' or bump stop spacers to further adjust when the bump stop engaged and to fine-tune spring rate.

8:12 Bump stop behavior out of sync along with damping bias can make for VERY unstable handling!

8:28 Are my struts inverted or non-inverted? Implications for gas force along with unsprung weight.

9:50 The cost of having high gas force on the damper is that 'Hidden Gremlin' that would affect your suspension whether you know it or not! Very common to have HIGH gas force with non-inverted dampers.

10:35 Example of Gas force / Rod force calculation (Gas Force = Gas Pressure * Shaft area). MCS with non-inverted strut and no head valve creates HIGH gas force! Lots of jitter, shaking, poor ride and reduced maximum grip.

11:18 Any good shock designer will use as little gas force as possible. Some high frequency filtering (aka 'Ripple Reducer') will reduce the negative impact of high gas force.

12:00 What type of pistons are you using in your dampers? The impact on ride and grip. Linear pistons will have soft initial response but continuing build-up at higher damper speeds. This can lead to jacking down and worsened bump absorption.

13:15 Illustration of linear damping behavior

13:59 Linear pistons can create a significant rebound-to-compression bias (3:1 or more) which can lead to strong jacking down, along with excessive high speed compression force due to a lack of proper blow-off behavior especially on street or track use (hitting curbing).

14:24 Illustration of digressive damping behavior.

14:50 Digressive damping has initial force ramp and then the force softens significantly above that knee point or blow-off point. Advantages of digressive pistons in terms of compliance and bump absorption, compared to the constant force build-up of linear pistons.

16:08 Linear pistons are cheaper to manufacture BUT less ideal for road or track use!

16:38 Bilstein digressive pistons are very sophisticated and capable, what's used in a majority of FCM Elite builds

17:22 With digressive pistons and valving there is less high speed force to prevent jacking down. How, not every vendor will build a setup that avoids jacking down even if they use a digressive piston! The dyno graphs and understanding rally vs. NASCAR damping profiles.

19:18 Tailoring Suspension Setups to Your Individual Needs. Expect this kind of interaction with a Quality suspension vendors. Avoid creative negative behaviors in their suspension products. As a customer, educate yourself and ask better questions to combat marketing hype.

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