SuspensionTruth

SuspensionTruth

#StepIntoSmoothness #FCMElite #FatCatFootwork #MinimizeJerk #MaximizeGrip

'Too much oscillation - too much bouncing - causes a reduction of friction, a reduction of contact patch - both in terms of climbing up a wall as well as taking your car and going around turns,' - Shaikh

Segment of video from 'Neil Gresham Climbing Masterclass - Technique Introduction' used under Fair Use copyright doctrine:

"The doctrine that brief excerpts of copyright material may, under certain circumstances, be quoted verbatim for purposes such as criticism, news reporting, teaching, and research, without the need for permission from or payment to the copyright holder."

https://en.wikipedia.org/wiki/Fair_use
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"If you want to fnd the secrets of the universe, think in terms of energy, frequency, and vibration." - Nikola Tesla

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I've been thinking about how to draw more analogies between the various frequency and amplitude domains a suspension works within and how to relate it to real-world behaviors. While driving to get lunch (and thinking about climbing after work), I remembered a great training video I saw which described certain bad behaviors in climbing technique.

The video I've linked below and shown in my video helped me relate 'poor foot technique' when rock climbing (e.g. a bouncing foot when stepping onto a foothold) to 'poor suspension tuning' such as a having damper with too much gas pressure, or too much low-speed compression or rebound damping. In each case, there's BOUNCING present. You can also call it JERK! That JERKING or BOUNCING reduces the consistency of contact patch. BOUNCING reduces the friction you need to produce MAXIMUM grip! There's an inherent NERVOUSNESS which is unfortunately often expected with a 'sporty' or 'racy' suspension but it's demonstrably NOT the smoothest and fastest way!

Bouncing or jerking means less consistent friction and contact with the ground (or the wall!). Bouncing means less grip, less smoothness, MORE JERK. You don't ge..

“If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.” - Sun Tzu, 'The Art of War'

I got a call today from Aaron who is the new head of Motorsports Division in Bilstein East. He asked me about Spec Miata bump stop specs and behavior. I wanted to know what was going on. He said some people in the Spec Miata community have asked about shortening the Spec Miata shocks, apparently to get more suspension travel. I told him I feel that's unnecessary and potentially a bad idea, as there's a high likelihood of tire-to-fender contact up front. I also told him that the damping wasn't well optimized to which he agreed.

Later, after our conversation, I recalled the potential for metal-on-metal contact in the rear suspension, which is even MORE insidious and dangerous! This could happen between the upper-control-arm-to-frame if there was too much suspension travel in the rear. I noticed this years ago when using the Flyin Miata rear spherical shock mount setup. In this video, I point out that experience with the Flyin Miata rear shock mount that essentially shortened the shock body about 1 inch by moving the bump stop contact point upward.

Whenever you shorten a shock, it becomes even MORE important to manage the bump travel. That introduces more problems and places to mess something up on the Spec Miata. I'm all for improving the state of Spec Miata, but you need to understand the pros and cons of a change before diving in head first. Otherwise that change is taking you backwards instead of forward. Not every change is an improvement, folks!

It's important to understand what deficiencies may exist in any design before applying what amount to bandaids. The Spec Miata shock tuning is NOT ideal for race track use. By design the SM Bilstein shock tuning SEVERELY ..

Attention suspension nerds, this video is for you! I visualize (via shock dyno data) and quantify (via spreadsheet calculations for damping ratio, rebound to bump ratio, including influence of gas force) the differences between the Mitsubishi Evolution X GS-R (with KYB dampers) and MR version which has Bilstein dampers.

In summary, the Evo X GSR dampers provide a better-tuned setup, still with drawbacks but on an overall smooth surface will handle well and ride well. The Bilstein MR suspension is highly-biased toward rebound on the front strut and will aggressively pull you down into the front bump stops. Bilstein MR rebound to bump ratio (including gas) is about 3.2 : 1 on the front, compared to 1.9 : 1 for the front GSR KYBs.

o/~ Summertime and the valving's easy! o/~

Sharing some assembly and tuning notes for this B8 series Audi S4 FCM Elite Stage 2 build with H&R Street Performance coilovers.

The front spring adapter from H&R allows the spring to move a bit on the perch. I'd suggest gusseting up this gap with steel shims and possibly a thin section of rubber hose to prevent the spring from directly rubbing on a shim. I just don't like having springs move around on the spring perch!

Good news on the spring selection front is that per my measurements (I checked various Audi forums but I found the quoted value not very accurate) the spring provide Flat Ride with ride frequencies around 1.7 Hz front and 1.9 Hz rear.

On the rear, H&R says you need to re-use the factory upper mount and bump stop. If you wanted, I believe you could trim some of the rear bump stop at the upper end, but that's your call.

In terms of rebuildability, I asked Tire Rack to check with H&R whether their Street Performance kit for the B8 Audi S4 was a rebuildable monotube style. They said the fronts were but the rear were twin tube. With that information, I recommended my Audi S4 customer Jermaine to buy some rear B8 Bilstein Sports which were a monotube style.

Once I had the H&R Street Performance coilover setup in my hands, it turns out that the rears ARE a monotube, although the small body and 14mm diameter shaft. They may have assumed that the smaller body means twin tube, but Bilstein makes monotube in both 36mm and 46mm body diameters.

Given the high weight of the car, you end up with a bit of a dilemma (as I found) when attempting to valve the rear small body H&R for good grip, good ride without jacking down (meaning an excess of rebound damping compared to compression), and low surface reactivity (which comes from excessive nitrogen gas fill pressure and the associated gas force pushing upward on the shock shaft).

I'll go into this more in another video, but I saw more hysteresis when trying to..

4th and final part of Kevin Pankhurst's comprehensive track talk on Sonoma Raceway, recorded June 10th, 2018 at Edge Motorworks in Mountain View by Shaikh of Fat Cat Motorsports.

He continues from Turn 3 and finishes going over each turn and how to link them together for the best and safest lap.

Link to his 50% speed lap is here: https://www.youtube.com/watch?v=LYuGk4ahh3w

Continuing with Part 2 of 4 of an excellent track talk by Kevin Pankhurst covering Sonoma Raceway, recorded June 10th, 2018 at Edge Motorworks in Mountain View by Shaikh of Fat Cat Motorsports. He goes into what to bring to the talk and discusses the importance of choosing the correct brake fluid, dealing with brake fade, how frequently to flush your brake system, and more. We take a break after this session and return for parts 3 and 4.

There are two bump stops present on this Mitsubishi EVO X. One bump stop is a 29mm soft density stop that lives on the shaft of the strut insert and isn't viewable unless you take the strut insert out of the strut housing. I've never seen this style bump stop on any Bilstein strut except the Evolution X. It has a comparable density to the standard black soft density bump stop Bilstein sells in their catalog, p/n E4-B36-556A, Jounce Bumper, JOUNCE BUMPER,3RIB 40X32MM.

The second bump stop, which is visible resting on the strut, is ~77mm long and secures to the outside diameter of the strut insert. This bump stop also holds the dust boot in place and keeps the boot high on the strut tube. From driving observations (terminal understeer!), I feel the factory suspension travel on the Evolution X is is unnecessarily limited so additional bump travel up front will help smooth out the ride and reduce the understeer. With our Stage 2 revalve that has more 'rally style' damping profile, a slightly shorter bump stop will give more comfort on bigger road hits while still providing enough protection at full compression. I've tuned the damper to have more compression damping which resists bottoming out, and I've reduced rebound damping across the board to allow the tires to follow the ground better instead of the high rebound force causing 'jacking down' into the bump stops.

I'm going to trim the upper ~21mm section of the outer, longer bump stop to gain some additional suspension travel while still having the outer bump serve its function of retaining the dust boot. You never want to trim the lower portion of a progressive bump stop as that makes the bump stop spring rate increase quickly and leads to a harsher ride.

The standard shafts diameters are 11.0 mm and 14.0 mm, so know what you're working with and machine your brass or aluminum soft jaws / vise inserts accordingly. You could substitute a sturdy vise for the shop press though the press makes this SO much easier! We have 17.5T press and I use 3 tons of force.

I spray the shock shaft and soft jaws with brake parts cleaner and wipe clean to improve the friction on the chromed shaft. If your bushing housing is dirty, clean that but with a milder solvent, not brake parts cleaner.

If you have rubber or poly bushings, take care not to overheat the housing when applying heat. Also, remember to add a few drops of removable threadlocker upon reassembly.

To install a dust boot, slip the top of its cone over the lip of the bushing or bearing housing. I neglect to install the dust boot for our customer Brodey's rear dampers, hence making his video per his request as an intermediate DIY!

Checking out these Bilstein HD front our new VW Tiguan customer. Front strut inserts have pretty high gas force, about 70 lb! Rear gas force is 45 lb, also high. We'll get that down especially by incorporating Ripple Reducer which lowers the pressure created by the shock piston moving through the oil.

The front damper is a symmetric rebound:compression curve which is good to not jack down, but the forces are high. The rear has pretty good compression levels I'd say but the rebound is very strong so there's definitely jacking down happening.

Overall, the Bilstein HD dampers for the VW Tiguan look surprisingly like the PSS Bilsteins on the Mk6 Golf GTi we did a couple years ago. That's not necessarily good, but it helps me understand the ride complaints our customer have and also helps me toward a solution - FCM Elite damping optimization, reduced gas fill pressure (and lower measured gas force at the shock shaft), and Ripple Reducer. This will be a Stage 2 FCM Elite build, so no KBO but still will be very effective. It'll ride smoother and have better grip when we do our FCM Elite magic!

To get in touch to experience our vision of Ride Harmony, send us an inquiry here: http://www.fatcatmotorsports.com/contact_elite.htm

This one is kind of a heart-scratcher and I definitely intend to follow-up and seek more feedback from Porschephiles. What I know regarding Cayman vs 911 is there's some bad blood between the two on which is the better-handling car, which is more 'truly iconic Porsche', and who knows what else. I think they're both great sports cars, but I really had to wonder 'what were the engineers thinking?!' when I saw the factory rear Cayman damping forces!

It's very very VERY stiff on compression - to the point that nearly any mild bump (over 5 inch/sec, which is quite low speed) will cause the rear suspension to JUMP up and reduce contact patch with the ground. This will lead to a VERY BUSY ride, and an unforgiving suspension over any kind of broken or uneven road.

In stark contrast is the Porsche 911 (997), which is contemporaneous to the Cayman. The 997 rear shock (nearly a 1:1 motion ratio but just slightly lower) is supporting even more weight than the Cayman rear strut. So theoretically, the 997 rear should be a little stiffer but it's actually MUCH softer - or rather let me say, the 997 rear is less harsh. It's still overdamped on both compression and rebound, but not to the degree that the Cayman is.

If someone wanted to make the theoretically 'better-handling' Cayman suffer a ride quality penalty for outshining the 997, you can make that happen by overdamping the suspension. That's exactly what I see, and there's no good reason for it other than to make the Cayman ride worse than the 997 on rough roads.

What are your thoughts? Please pass this video along to any Porsche enthusiast you know, in case this information and dyno graphs aren't already available and have been discussed.

To get in touch for your own FCM Elite Project, send us an inquiry:

http://www.fatcatmotorsports.com/contact_elite.htm

In evaluate the Ohlins DFV coilovers for a Porsche Cayman. The dampers were loan by my customer Murat once he put our FCM Elite-optimized H&R Street Performance coilovers on.

Strangely, the front Ohlins have very limited extension or droop travel, and 2 inch total bump travel. So effectively you are riding around on the bump stops once the suspension is loaded. You can also see from the dyno test that the bump stop comes into play near the end of the 2 inch minimum required dyno stroke.

Also, Murat was running the dampers at FULL SOFT to get a decent ride. The front gas force on the Ohlins was 48 lb, which is quite high considering we could get down to 20 lb with the Bilstein-based H&R Street Performance coilovers using our FCM Elite methods.

The original spring rates were 70 N/mm front and 80 N/mm rear, or 399 and 456 lb/in, which he found FAR too stiff! He went down to 50 and 60 N/mm, or 285 lb/in front & 342 lb/in rear, which worked better but he was still missing the benefits of KBO and Ripple Reducer along with our gas pressure optimization.

He also complained of always scraping the front bumper's air dam going into / out of driveways and over speed bumps. We're adding a longer front shaft to the H&R setup to improve this further but having the ability to extend travel is a big plus!

This is another ready why I don't like the 'adjustable body length' feature because you can't use a long-enough strut tube or shock body length that allows enough extension / rebound / droop travel.

To begin your own FCM Elite Project, send us an inquiry here:

http://www.fatcatmotorsports.com/contact_elite.htm

For those who may be curious how you take a Bilstein apart, here's the process in all its glorious (gory?!) detail! We're using a customized Accu-Force shock fill machine with custom 36mm accessories / adapters. I show how to access the upper and low snap-rings, considerations for fluid overflow and maintaining as low stress as possible on the rod guide and seals when disassembling the damper. Oh, and you'll want to drain / wipe the inside of the damper body of excess oil once you're done 'cause there will almost certainly oil in there!

This procedure is useful if you want to set up the proper tooling to refill the damper without adding an external Schrader valve, which we don't do any longer. The OE-type nitrogen fill / shock assembly process gives better durability and more worry-free operation than you get with an external valve.

Keep in mind when you are servicing a Bilstein-based damper that you need to grind down any part of the nut / swaged end of the shaft otherwise you will ruin the threads. For newer builds, the nut is usually secured via a threadlocker so grinding isn't necessary.

If you'd rather have us take care of this for you, or want to begin an Elite Project, you can send us an inquiry here:

http://www.fatcatmotorsports.com/contact_elite.htm

Do you hear a clunk or thunk from the front suspension when using H&R Street Performance coilovers on your Porsche Cayman, Porsche 997 911 - or another application? You might be hearing the front H&R spring slapping into the H&R aluminum upper spring perch. The tolerances could be tighter...

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During a fun initial test drive a few days, my customer pointed out (and I also heard) noise from the front suspension when we went over sharp / large bumps. I had a feeling either something in the front strut / sway bar mounting was loose, or there might be a larger-than-ideal clearance between spring and coilover adapter. He was sure he'd tightened everything up well so we needed to diagnose the noise examining clearance on the H&R Street Performance coilovers.

I went down to his house where he had his Cayman jacked up for easy suspension access. I also wanted to test the front bump travel so he initially removed the spring so we could put the car into full bump. This video shows the front Cayman suspension in that position.

My estimate for the bump stop stack was pretty good!! I had used 2 soft-density Bilstein segments (~40mm) and the medium-density progressive 'cone' from the original H&R bump stop (~20mm). This gave a nice two-stage behavior to the suspension and we could verify there wasn't any contact between the tire and the fender liner. This custom bump stop arrangement definitely gave more useful and safe suspension travel than the Ohlins DFV had as well as the OE Cayman suspension. The factory always is more conservative in their travel estimates which I can understand when using softer OE springs vs. the higher rates we're now using.

The short video on my custom bump stops for this '07 Porsche Cayman project is here:

https://www.youtube.com/edit?o=U&video_id=01AVpU0YxAs

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Regarding the noise, we found about 2mm total clearance (1mm per side) between the H&R 60mm spring OD and the ID of the aluminum upper spring adapter they provide. Not good. I kne..

Introduced my nephew and brother-in-law (aka B.I.L.) to indoor climbing today! My nephew had a great time, seemed to enjoy falling as much as ascending! Later my B.I.L. asked me to climb something harder so I went for my favorite black V3 in the upper bouldering room. It originally took me quite a few attempts before I could get it done without my arms burning out. Now, the callouses have formed so I can get up it pretty quickly!

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Created 2 months, 3 weeks ago.

14 videos

CategoryEducation

In his seminal book 'Zen and the Art of Motorcycle Maintenance' Robert Pirsig wrote 'Quality eliminates Subjectivity.'

My goal is to eliminate the subjectivity, confusion, and mystery behind how a vehicle suspension works - and how we can make them work better.

I create videos based on Fat Cat Motorsports (FCM) Elite projects for my customers, HPDE (High-Performance Driving Experience) track days, autocrosses, personal thoughts, and how-to videos.

I'm happy to engage and answer questions within reason, however I cannot answer questions in great details specific to a particular vehicle. If you want my focused attention, please sign up for consulting here:

http://www.fatcatmotorsports.com/contact_elite.htm

I welcome your ideas, comments, support, and engagement! Let's explore this awesome area and pursue my goal of Harmonizing Your Ride!