The definitive guide to Anti-Dive and Anti-Lift in suspension systems. What it is and how it works.

[@frederickphilips9442]

Thanks! A cool and simple enough explanation. Keep up the good work! And most importantly, do not pay attention to unreasonable criticism

[@ehcantremember3360]

This channel makes me feel like a genius and a moron at the same time

[@k.bellingham8335]

I cant say this eloquently so I'll say it from the heart, love your damn lessons, I'd stay late after every school day to pick your brain. More please.

[@spiky29]

Thanks again, for good explanation. Would love to hear more about KPI, trail and jacking.

[@carpdime1592]

I can't express how much I appreciate this channel. It's pure gold, and I eat up every minute of these videos.

[@NorCalrestorations]

Great video Huibert. The knowledge and education is unprecedented in your videos. It was a pleasure working with you on the Tesla Model S Development days. It still is the bench mark of electric cars today.

[@suspensionsexplained]

Yes, those were good days!

[@AlecHulvey]

Came across your videos recently and have been really enjoying taking the rust off my knowledge! Recently I have been thinking about dampers and while I understand their basic function I don't know exactly what makes a "good" damper and what traits more expensive ones have that cheaper ones don't. I would love to see a video on this subject eventually, but I don't doubt whatever you make next will be extremely informative either way. Thank you for your hard work!

[@suspensionsexplained]

There really is no single definition of what makes a "good" damper vs a bad one. It really depends on the car and what it needs. Generally speaking, more expensive dampers are made of more durable materials and should last longer. That's not a hard and fast rule though. Check out SuperFastMatt for a good explanation of dampers and how they work.

[@ИванНовожилов-э9з]

Your videos are pure gold! Thank you very much for sharing your knowledge with us.

[@moneyshifters]

E46 or e39 touring diagram is a cool detail. Lovely car. Great video, as goes without saying.

[@suspensionsexplained]

Lol. It's the one I found that seemed royalty free.

[@moneyshifters]

haha. funny that

[@rikoskokos]

Thank a lot, Huibert! Brilliant channel with high-tech content explained with a simple words. As Einstein said if you can't explain it simply, you don't understand it well enough.

[@shoaibshaikh7196]

Dear I really liked your videos and its very informative and easy to understand the details. could you please make some similar videos for steering system both rack-pinion & recirculating ball joint.

[@robertfontaine3650]

Fantastic explanations.

[@WallyMay235]

Thanks for putting together such detailed explanations! I was wondering if the mass and CG height used to calculate dive, squat and roll moment should be the sprung mass and CG height. I could see on a larger vehicle the difference might be pretty small, but on a smaller/lighter vehicle it could be meaningfully different between total mass X CG height and sprung mass X CG height. Thanks!

[@人机结合]

thank you Mr Mees

[@abhishekhambar8202]

@ 3.33 second , after solving equations values coming 62.8 mm for front and 68 mm for rear , how you took 31 mm and 34 mm spring deflection?

[@longrifle.]

Great videos. After watching a few i subed. Perhaps you could cover some live axle suspension with regards to towing. Load distribution ect.

[@schaefsky]

How exactly is the center of gravity height defined, e.g. when the vehicle would stand on an axle articulation test with FL and RR wheels up and FR and RL wheels down? Does it have to be defined per wheel? Also, what would happen with a rear wheel driven independent suspension with regards to anti-squat / anti-lift? How does the suspension "know" where the weight transfer is coming from? (since this will change whether one draws the line from the contact patch or the wheel hub if I understand correctly)

[@suspensionsexplained]

The center of gravity is the point at which everything is balanced. Imagine the car suspended on a string attached at some point in the car. If the string is attached at the center of gravity, then the car will be balanced in all directions.

[@Victorini330]

In minute 3:45 (the calculations) Where does the 1750N come from in the bottom equations?

[@suspensionsexplained]

This is the weight transfer. See the equation at the 3:00 minute mark.

[@briank10101]

Can anti-squat help with traction on front wheel drive cars?

[@suspensionsexplained]

No, it can't. Anti-squat needs a drive force in order to counteract the effect of weight transfer. If there is no drive force, then there are no anit-squat forces. A FWD car has no drive force in the rear.

[@grippgoat]

When using the instantaneous radius method, you talk about locking the brake to lock the wheel to the upright. Does this mean that the contact patch location on the tire is the same point used at zero deflection, rotated with the knuckle (if the knuckle rotates) for the up/down deflected positions? Or do you still just drop a line straight down from the axle centerline for the deflected positions? I'm trying to analyze the multi-link rear suspension on my BRZ, which has a lot of angle in the trailing link, and may cause some rotation of the knuckle when deflected, making a significant difference in the front/back location of the contact patch between the two methods.

[@suspensionsexplained]

You need to imagine the brakes locked so the contact patch momentarily moves with the knuckle. If you juist drop a line straight down from the wheel center then the contact patch would just do whatever the wheel center does. That would be incorrect. Lock the brakes while making the tiny up and down motions to give you the instant center line.

[@suspensionsexplained]

You use the contact patch with a locked brake. You use the same point that you used at zero deflection. I know this seems odd but that is why you use very small suspension deflections to do this method. I used 10 mm but proper multi-body dynamics systems like ADAMS will use much smaller deflections to eliminate as much error in this math as possible.

[@donovanlucibello379]

Mr Mees, thank you for a great series of videos, this shade tree mechanic is learning a lot. Would you be able to answer for me a notional extrapolation of a concept (or if you did a video elsewhere just point me to that please), what would happen if the wheel base of a car was extensible? For example, take the wagon you had in your example, if it was extended into a limo configuration and became 50 mm longer at the wheelbase would all of those calculations be qualitatively affected positively or negatively in their effect for antidive anti-squat properties?

[@huibertmees4781]

Thank you for your comment. Extending the wheelbase has the effect on increasing the amount of anti-lift. The reason for this is that the angle of the ideal line is reduced with a longer wheelbase. This makes sense since the weight transfer is a function of wheelbase. As the wheelbase grows, the weight transfer gets smaller for a given deceleration, so it takes less braking force to counteract the weight transfer that is there. Since the suspension geometry doesn't change with wheelbase, and the braking force doesn't change, the amount of force the suspension generates to counteract the weight transfer will still be the same, but the amount of weight transfer has been reduced. Therefore, the suspension is counteracting a larger percentage of the weight transfer with the longer wheelbase. I hope that makes sense.

[@szjm19]

Dear Author, Is it necessary to replace both front shock absorbers if only one has failed (due to hitting pothole with one wheel)? Thank you

[@suspensionsexplained]

Yes it is. The good shock will still be partially worn and combining it with a new shock will be a problem. You want the same level of damping on both sides of the car at all times. And besides, that other shock might be 2 miles away from failing as well. You never know!

[@payron805]

more vidéos!!

[@Dr_Xyzt]

1: If you have high anti-dive values, will it negatively impact your ability to corner while partially decelerating? 2: Why do some suspensions have lower control arm on an axis that is not parallel to the longitudinal axis of the vehicle? 3: Is it safe to say that on rear suspension, anti squat on acceleration becomes anti-lift under braking? I ask this, because I did a torque arm suspension with control arms aimed slightly upwards and it had violent wheel-hop under braking. 4: How much roll understeer/oversteer is detectable to the driver?

[@suspensionsexplained]

1- High anti-dive values should not impact cornering ability while braking. Having said that, high anti-dive and anti-lift values mean there is not much suspension travel happening when you hit the brakes. This means you can't use the roll steer to help generate understeer in a corner while braking. You have to use bushing compliance instead

[@suspensionsexplained]

2 - The lower control arm axis is very often determined by package space, especially in the rear. It doesn't have to be parallel with the longitudinal axis of the car. 3 - Anti-squat and anti-lift are NOT the same thing. In an independent suspension, anti-squat is related to the motion of the wheel center while anti-lift is related to the motion of the tire contact patch. In a live axle, both are related to the motion of the tire contact patch. However, the ideal lines are different. For braking, it goes from the contact patch to a point located at the height of the CG and a distance behind the front wheel equal to the wheelbase multiplied by the percentage of braking done by the front wheels. For acceleration, the line goes from the contact patch to a point located at the height of the CG and a distance behind the front wheel equal to the wheelbase multiplied by the percentage of drive torque done by the front wheels. For a purely FWD car, this means the point is located right at the rear wheel, making anti-squat meaningless. For a RWD car, the point is located right at the front wheels. 4 - This really depends on the character that the OEM wants in the car. There is a balance between roll understeer and compliance understeer and this balance can greatly impact how the car feels. It's a question of timing. When you enter a corner, the cornering force is first to appear and build up. This force causes compliance changes in the suspension. Once the force builds, then the body will react by rolling. This is when roll understeer appears. If the car is setup for compliance oversteer and roll understeer then at first, the car will oversteer slightly until the body rolls and "catches" the car. This can make the car feel very responsive but could also get you into a lot of trouble if you have to do a quick lane change when you steer left/right/left or right/left/right quickly. The body doesn't have time to roll, and you are working mostly on the compliance oversteer. Almost all OEM's will setup their suspensions to have both compliance and roll understeer for these reasons. It's also the safest setup, especially since the vast majority of customers are inexperienced drivers when it comes to emergency maneuvers.

[@Dr_Xyzt]

@@suspensionsexplained 1: Thank you very much for the detailed response! I greatly appreciate it. That describes my front suspension very well. It has delrin bushings. The vehicle will not penalize poor technique, but will tolerate it. If you decelerate and turn at the same time, it will lock the inside front tire, but that won't upset the vehicle. If you reduce both inputs, it will revert to a neutral state awaiting proper cornering technique. 2: That describes the vehicle very well. The rear LCA mounts come very close to the headers. That's a frustrating aspect of this assembly. My new powertrain will be an inline-6 for this reason. Plus, the math for splayed control arms is harder than simply rotating them... 3: This is very helpful for my rear suspension. I will likely use a 3-link solid rear axle. A longer instant center with less anti-squat will be my goal for safety reasons. 4: I'm gonna have a cup of tea and pay for some seat time in better chassis before I set my design choices in stone... or... chromoly.

[@briank10101]

Does this apply if I accelerate and decelerate the car when driving in reverse? 😮

[@suspensionsexplained]

It does, but everything now happens in reverse. Lots of anti-lift in the rear turns into pro-lift in reverse.

[@clearestcosmos4348]

I am very confused with the spring deflection equation. The order of operations on it is very unclear and it seems like you're putting the entirety of your load onto a single spring which doesn't make sense because you calculated the equation as the entirety of the car, which will have two springs. The only way I can get the answer in the video is by doing the entire equation and then dividing by two and even when I apply this to my own car's parameters I get values that are not physically possible based on data from a previous car. Could you explain in more depth where the 1000 value comes from specifically that's the part I am most confused on.

[@suspensionsexplained]

This video wasn't the place to get into the details of the ride frequency equation, but the equation is 1 over 2pi times the square root of K over M. K is the spring stiffness (actually it is the suspension stiffness since the spring is most likely acting through some motion ratio) in newtons per meter while mass is in kilograms. Since I wanted to find the deflection in millimeters, I had to convert the spring stiffness from newtons per meter to newtons per millimeter, hence the 1000 term. Also, the mass term is shown as 2000 kg times the weight distribution divided by 2. This gives the mass of one corner, not the whole car. I then had to subtract the unsprung mass since that is corner mass that is not supported by the springs and doesn't contribute to the ride frequency. I hope this helps to overcome any confusion.

[@abhishekhambar8202]

@ 3.33 second , after solving equations values coming 62.8 mm for front and 68 mm for rear , how you took 31 mm and 34 mm spring deflection?

[@YangD-082]

Anti-dive only affects the driving feel but doesn't change the maximum braking performance? Does it affect the car's characteristic? Does it make the car more understeery or oversteery when the car is under braking?

[@suspensionsexplained]

That depends. If the suspension has a lot of roll understeer designed in, then the added deflection of having very little anti-dive or anti-lift would cause more toe change during braking which could make the car more skittish on uneven pavement. Most cars only have a little bit of roll understeer built in so I wouldn't expect it to have much of an impact. In any case, anti-dive and anti-lift have no impact on overall braking since they don't change the braking power nor the total weight transfer. They only affect how the suspension reacts to the weight transfer, they don't change it. Look at the math for calculating weight transfer. It ONLY uses the deceleration level, the mass of the car, the CG height above ground, and the wheelbase. Nothing in there is affected by anything related to the suspension design. I hope that helps, and keep asking questions!

[@YangD-082]

@@suspensionsexplained Thank you so much! There are many sources claiming different answers on this topic and that really confuses me. Your answer really helped me clear up my confusion. What is roll understeer? Does it relate to bump steer?

[@cam3002]

Where did you get the front ride frequency of 1.2 Hz and rear ride frequency of 1.3 Hz?

[@BLoudermilk]

Spring rates and frequencies are covered in a prior video

[@martinburnett3852]

He literally said it was an assumption dude. He made it up.

[@suspensionsexplained]

Those numbers are just examples but both are very typical of what you might find in a modern sedan.

[@improvedae86]

I just feel sorry for the poor French man driving the BMW , he isn't used to the motion because he normally drives a interlinked hydraulic suspension vehicle ...