The forgotten part of car suspension design - minimising pitch 

Excellent presentation! Very much appreciated. I knew about GM’s research in the 1930’s and knew they had a famed researcher and now I know his name. Absolutely wonderful. I happened to read maybe 20 years ago that a Buick engineer was the first to systematically understand understeer/oversteer and it’s relationship to slip angles, suspension stiffness and roll bars (sway bar in the USA) maybe it was Maurice Olley as well? Somehow I believe ride comfort (or boulevard ride as Cadillac named it) will be more popular in the future tha it has been in the recent past. Days when the highest aspiration for a daily motorist was to lap the Nürburgring at highest possible speed must be coming to an end! I have noticed that Citroën have decided to re find it’s roots and focus on more comfort oriented suspension setups. During this summer I managed to try a C4 e (electric) and it was a delight due to the calming effect of silent “engine” and supple suspension and good seats. Had it been built on a dedicated electric platform it could have been better still as it would have allowed a longer wheel base and a lower center of gravity. Regarding the delights of interconnection of front to rear suspension I think it’s only going to happen with slightly more expensive cars because it most likely will require self leveling suspension. Another item which strangely have lost popularity. Somehow car producers must believe customers are more willing to pay for big diameter wheels with absurdly low profile tires than self leveling suspension. 🤔Strange. Thanks once more for this uplifting presentation.

I design racing suspension for a living. The reason you see a stiffer front suspension than rear: Drivers struggle with traction loss. Vehicles with a stronger rear spring bias are more likely to oversteer, especially off throttle. The engineers have no forgotten about pitch, but rather, the whole car is designed to car nose-first into objects. The entire crash structure is designed under the assumption it will hit nose first, because the most common collision is a front end collision. So you ensure that the car is going to understeer and lose front traction first, they bias car suspension for stiffer front springs and softer rear so that the car is more likely to collide in a manner that the crash structures are designed to absorb energy, but also in a manner to push the drivers into the common direction of the airbags. This all comes at a sacrifice of sporty, oversteering handling, and at a sacrifice of pitch consideration. It's also part of the reason speedbumps are so effective at traffic calming as the pitch sensation is now a greater discomfort.

Always enjoyed your articles on autospeed over the years. Looking forward to more of your RU-vid content!

Love these videos. I rented a Renault Alliance way back in the 80s, and despite its small size, it is the best riding car I've ever driven. No idea what kind of suspension it had, but it handled okay as well

I have found the videos nearly as good as the book for aerodynamics, but I will buy this one also. Thank you for your innovation and analysis of so much automotive and physics. I have enjoyed your works since the Autospeed days.

You're making a good argument for me to find an engine conversion to put in my Morris 1100S! Hydrolastic and mini's rubber cones seem much undervalued, Moulton was a bit of a genius, it's a shame his contributions aren't a larger part of modern suspension.

Very interesting. Thanks for sharing.

Tesla could do with a lot of improvement in this area.

I feel like most consumers these day are so focused on all those silly electronic gadgets in cars and care so little about the way a car drives that most car manufacturers don't bother to put much effort into developing certain basic components of a car anymore, like a car's suspension. Not to mention the obsession to cost cut the hell out of everything and throw their cars together as quickly and easily as possible seems to be stronger than ever. Just my observation, but the ones that get negatively affected the most from this seem to be mostly regular cars.

If someone made a car today with a suspension you talked about it would make speed bumps useless

I knew something about this but not much when i got aftermarket springs for my truck they said "frequency tuned" now that i think about it i would pass a peice of undulating road and my truck would stay level while everyone else would be bouncing like a boat.

awesome!

Great, great video and presentation. Suspension comfort/ride has been an interest of mine since I was 6 years old (seriously) and the interest has never left me. On my 2012 Toyota Camry, I attached 6 concrete blocks (4'X4"X15") just behind the front radiator (within the engine bay) to try further reduce the natural frequency of the front. I quickly noticed the improved ride, it felt like I stepped up to a more plush luxurious riding car. I just don't get why people want a more "sporty" ride and more road feel. Tires can also make a big difference especially to the higher frequency bumps and quietness. I got Pirelli P7 ASPlus3 tires which I think just came out in early 2022 for my current 2018 Camry Hybrid XLE which made a nice improvement to the ride and reduced road noise. Now I'm planning on installing about 40 to 80 lbs of lead (Pb) in the front or near the radiator to try further reduce the natural frequency of the front of the car. I'd love if a car was made with 0.5 Hz natural frequency - it would be interesting to see how may are actually susceptible to motion sickness at that frequency and it would be fun to experience this frequency on challenging roads. The downside of the higher weight (if you don't get a longer spring) is the reduced suspension travel if you hit a really big bump. I'm guessing the reason the car manufacturers don't reduce the natural frequency further is that they don't want to be scolded by motor journalists who in their quick test drive will report the ride as being floaty or soft which they have convinced motorist to be a negative. i.e. Stiff ride = Sporty and cool, Soft ride = out of style grandpa car that is a lot of emotion and little logic. You see this with all the aftermarket damper "shock absorber" ads where stiffer is better - They should rename the dampers "shock producers" with the stiff damping settings that seem to be the fashion nowadays.😀

I remember those old cars with different rate suspensions front and rear. Yes they were smith riding over bumps, but the additional bouncing after the bump was traversed was annoying. That is where the term boat and float came from. The packard and citron suspension worked surprisingly well. The packard one was poorly received because it was too different and misunderstood. Plus’s it has a self leveling system which was prone to failure.

Toyota x-reas and KDSS come to mind when you say that no mass produced vehicles have connected front and rear suspension. Though x-reas was the only system that was used to reduce front/rear pitch. Love your videos, thank!

Excellent channel, love the content. I agree that car manufacturers now have a bias for firm suspensions, but there have been solutions for minimizing pitch and improving ride comfort. Improvement in electronics have made mechanical solutions for this problem obsolete. The Mercedes Magic body control or Audi's predictive active suspension are able to adjust springing and dumping to each wheel without any special mechanical link and with scanning the road surface they are even able to prepare the suspension for the road ahead.

Hi Julian, I recently discovered your channel. As a professional mechanical engineer with a youth spent undertaking automotive mechanical repairs,... I absolutely love your lessons. I wanted to bring your attention to the 2010-2012 Mazda 6 (GH-series 2 Australian model). It's has Double wishbone front and multi link rear suspension,... but most importantly I believe it is a modern example of option 2 for pitch control with significantly softer front suspension than rear. I have the manual hatchback model, and it was the pitch, ride and roll control that I first noticed along with the low revving torquey engine. These were deciding factors for me, which my brother then tried and bought the same vehicle. I have had the opportunity to test drive many different makes and models over the years before and after this Mazda, yet I plan to hang into this one for a very long time. If you have the opportunity, I would appreciate your opinion on whether this truly is a modern example of this method of pitch control.

Good vid

I think one of the reasons why there's less talk about this today is because damping probably has increased in cars across the board so even if the frequency response doesn't hold that perfect level-ride ratio, the damping kills the oscillations fast enough for you to not really care.

Todays car manufacturers would love to add pitch control etc, the problem is the sheeple do not understand how this improves the ride and handeling, hence they are not going to add the advancements to the vehicles due to the pass on costs to the consumer, as they will not want to pay for something they do not understand.

Hi Julian, interesting video as always. I think you are correct that OEMs no longer have good suspension design as a priority. That said, do you have any factual evidence that OEMs are not utilising flat-ride in most modern cars? The pitching you observe could be caused by many things, for example: 1) The car may be set up to flat-ride at a certain speed, so going faster or slower than that target speed would impact how much flat-ride that particular vehicle has. 2) Another aspect could be the weight of the car, if it's fully loaded up with people in back seats, luggage in the boot etc then that predominantly increases the rear weight and so the rear axle suspension frequency would be lower. This would then mean the car flat-rides less than when it only has the driver in it.

Its probably just a side effect, but in my shelby with magnetic ride dampens i had nearly the same feeling as level ride. Its just stopping dampening when i hit a speed bump and then firms up again as soon as the wheel is over it.

Hi Julian, may I have an OT question: Are you familiar with 1st generation Honda CRX (front torsion bar MacPherson)? In your opinion, is there any benefit to adding a strut brace here? I know in a convetion macpherson strut there is, but here since the struts are only there for shock absorbing and don't carry the weight of the car, I feel like it might not be very benficial and might as well save the weight. Thank you in advace!

OH my God .... what a channel! Damn.. that is amazing... F..ck... I've been looking for that on youtube... That is real level up in comparison with eng.explained. Thanks!

Maybe you can shed some light on this. I am planning on using some nice Ohlins shocks to get the adjustability and a quality product but I want to convert the front McPherson struts to air suspension specifically a sleeve rolling air spring type. The rears are standalone shock with another larger rolling lobe air spring as well. This is for a Tesla model 3 btw. Effectively if I understood your video on air suspension based off of my larger rear air spring and smaller front air spring I should have already inherently softer spring rate for the front and larger for the rear which would reduce pitch. I would just need to adjust damping to smooth out the oscillation after the bump hit etc. Any recommendations on how to properly set up damping?

Really informative video, as always! Not sure how others feel about it, but looking at a videos of yours really hurts eyes because of the white background 😆 Maybe you could choose one that is a little darker.

Also diagonal pitch. Take a 4 wheel IRS SUV off-road and you will spend a lot of time on three wheels. This is not stable. On the street when an diagonal pitch situation arises they tend to hunt for stability across their diagonal axis. In these situations I prefer my 4 link coil sprung live axle. The rear axle articulation allows much closer to a 3 point suspension that is stable in diagonal pitch.

Are these factors be applicable to performance-oriented cars, particularly when it comes to tarmac motorsports?

I wonder how much those systems would worsen the pitch under heavy breaking.

Julian, what about the McLaren 720S and their interconnected suspension system? I know you point out no cars with significant production numbers, but the 720S is not that low of a production vehicle.

Cheers for your vids! Another YT channel called Suspension Truth by Fat Cats Motorsports is a huge proponent of this, very much worth checking out.

mid engined cars like the F1 or an Elise do hardly change weight distribution over load. The varying load is mainly near the centre of gravity of the car. With such cars the focus is one handling and feel, less on comfort. In therms of feel, different natural frequencies front and rear lead to a feel of disconnection. The rear of the car feels different to the front. It does not drive as one car, but two. You turn in, the front turns and you get the feeling of the rear following moments later if the rear frequency is lower than the front. On the road during mundane driving, this is hardly an issue, but on track or spirited road driving it is very annoying.

My 2015 Mazda SP25 is a kooky example of WTF suspension thinking. The front has very little compression damping and lots of rebound damping. This makes the front freq appear to be very low, especially when compared to the rear end. It gives the front a slow 'wallowing' feel that is straight up nasty. It also has the effect of 'jacking down' the front end when subjected to repeated bumps - the suspension never gets a chance to recover from the previous bump. Going over a speed bump, the front wallows while the rear is very rapid. Speaking of flat ride, FatCat Motorsports in the USA is a HUGE proponent of achieving this in your custom ride and he will work with you until the goal has been achieved. Not cheap, but very good. If I can get the $$$ together, I'll send my Bilsteins over there to be valved properly, because if you want to see what pitching is, come for a drive in my e30! Aye!! :-/

Doesn't the still in use Hydractive (tm) suspension connect the front to rear?

The spring rate idea sounds great until you realize that a properly damped car should only cycle once when going over a bump. Not only that, but how different can the McLaren F1's front and rear frequencies really be if the occupants all sit roughly in the middle and therefore don't change the weight distribution that much. What I'm saying is, does the F1 have the 70% thing or not, since passengers and fuel won't change that 70% to be equal regardless of whether the car is full up or only with the driver. And aside from that, how would a front that's 30% softer than the rear affect handling in general on any car? Seems like that's a high enough discrepancy to lead to a lot of strange and unoptimized handling characteristics. Like I said, if a car is properly damped, it shouldn't be "pitching" a lot anyway since the suspension will only complete one half to one whole cycle with optimum damping, anyway.

the higher class of current mclarens interconnect the front and rear suspension. or cross ways i remember

Africar = Wrongthink.? . Then ? NOW ?. plyhduralasticity in a suspender unit ?.. the fluid got stoopid hot.. needed a suspension cooler ? or better/newer .. materials.

this was just been discussed in the (german) auto-motor-sport review of the model y: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE--orKmOSYErA.html

That front rear hydraulic is fundamentally not true lexus landcruiser uses it. It's just not in the manner your talking about along with Lamborghini. Lexus uses a hydraulic piston attached to the front and rear sway bars.

To many horse power does not allow cars to have soft suspension, so manufacturers have to choose between stay on the road and comfort. Sadly.

So that's why hitting a bump in my RAV4 is so jarring compared to what it was in my Focus.

Please don't advocate driving off road vehicles. Thanks to Chrysler's marketing team, they convince the American populace that Jeeps are the off road king and the last thing we need is even MORE Jeeps coming in the shop since they're giant piles of junk. Other than that, great video.

You're just wrong on this. EVERYONE still uses Flat Ride on road cars, mostly to their detriment. Your conclusion just isn't supported by the cars on the road. Actually calculate the ride frequencies of most modern road cars. They are almost *all* with the rear ride freq. ~10% higher than the front. This *destroys* the handling of the car because it paints you in a corner with supporting driver-induced chassis motion. Flat Ride only calms down the passive pitchy nibble you get cruising on the freeway. It makes pitch due to braking events worse and induces rear instability while braking.