Spring rates tell you only half the story
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- Опубликовано: 14 сен 2021
- Forget spring rates and motion ratios - it's the natural frequency of suspension that actually matters.
Buy the book here - www.amazon.com/Car-Suspension... (or from Amazon in your country) 
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i get so excited for each new video! always learn something new. incredibly rare for a youtube channel today. normally have to wait months for an informative car video.
Glad you like them!
Really enjoying your recent uploads Julian, even as someone who already understands these topics it's always good to hear other peoples' thoughts on the subject.
When I saw this notification pop up, I had to spring to action and view it. Did it so quickly, thought I had compressed a vertebrae , but it rebounded. It no longer hurts.
Man, you put a smile on our faces!
@@JulianEdgar love the vids Julian, been following you for years mate. Even use the wool tufts for testing. Now, I’m a dyed in the wool tester. By the way, do you have the spring rates for wallas or kangas? Saw a boomer yesterday with some great rebound.
Your last thing said in this video (about Chevy Corvette) answered a lot of questions I've been putting in the last year. I have changed the front dumpers and coil springs on my car and something was wrong: the front end of the car raised about 5 cm than normal. And I did a lot of research to see if the spare parts were for my car or not. But, guess what? They were. And still... The springs, although they were shorter than the originals, they were much stiffer and that thing led to a raised front end. The proper springs are longer but softer than "wrong" ones, but the whole suspension setup is firmer. That is because of the dampers. That thing I couldn't understand. Thank you a lot!
Well am I lucky to have stumbled on an interesting channel. I really like what you have posted !
Glad you enjoy it!
Julian love the presentation, Ive learned so much. I reccomended your channel to a lot of people. I love the people who know some stuff, but when you talk about aerodinamics, they think they know also a lot. But wont look at the science. One of my friends told me, car has better cooling with no undertray, because air can enter under the car. He just got emotional when I started talking about pressure and other stuff. Great video and have a nice day.
Thanks Milosev. Most people simply don't (and won't) believe you can do proper car aero development at low cost on the road. Drives me nuts a lot!
@@JulianEdgar My cars missing the stock engine cover, and I ordered, the friend told me that's a waste of money. Also the little air deflectors in front of the wheels, he also said they do nothing. I said maybe when you drive 30kmh in the city sure, but as soon as you hit 100-200 kmh, those little wind deflectors make hell of a difference. Do you have any other social media where I can follow you Julian?
I am on Linked In both as Julian Edgar and Julian Edgar Books
@@JulianEdgar Ok thank you
What’s the relevance of the vertical stiffness of the tire in these measurements (which depends on the inflation pressure among other things)? Would you say its effect is negligible?
Natural frequency of tyres is about 10 times that of suspension ie tyres are comparatively very stiff and so can be largely ignored (except in damping, where dampers need to stop tyre hop ie work also at tyre natural frequency)
All very interesting. Do you know what wheel spring frequency World Rally Cars use on tarmac and gravel?
The thing I find amazing about this topic is how much influence the bump stop has. Cars seem to use suspension that starts getting onto the bump stops very early in bump travel, so calculating the true spring frequency is very difficult because you're ignoring a significant element if you just use the spring rate.
Bump stops are therefore very significant in determining the handling balance because they are definitely in play during roll.
I don't know the natural frequency of WRC cars. Because they ride well, I'd expect maybe 1.2 - 1.5Hz? Yes, it's a characteristic of modern cars that many use the bump stop as a rising rate spring because they don't have enough suspension travel. When I measure nat frequency, I don't calculate it from the spring rate - I measure it on the car.
@@JulianEdgar thanks for the reply, I will definitely be buying the book!
Is there a mathematical relationship between front/rear natural frequency, wheelbase, track width, and center of gravity? I'm wondering if it would be possible to take measurements of suspension, and then calculate what the effect on handling would be to e.g. increase front natural frequency by changing damper settings.
They are not derivatives of each other, and should be referred to in groups needed for a specific analysis. To get further to what your looking for, look into roll stiffness ratio. ChassisSim has a video on it.
(1) No. (2) Changing damping does not change natural frequency (not unless the damping is so strong the springs can't even move, anyway).
Isn't it often mostly because of higher weight on the front axle?
The mclaren f1 I considered soft and slow to set compared to modern and even some contemporary very sporty cars. Not saying it's a problem, the car was developed to be comfortable, not just as sporty as possible, but important to keep in mind
Yes, the McLaren was designed for real roads, not racetracks. Not sure the same can be said today - even most road cars are these days much too stiffly sprung and damped!
How does damping effect the natural frequency, if at all?
It doesn't change it, unless the damping is so stiff that the spring cannot really move.
I have a 2011 Lincoln Navigator with air ride suspension in the rear. How do I determine the proper ride height for the smoothest ride? Any help would be appreciated
Measure the rear natural frequency at different ride heights with the car loaded. Easy to do with a phone and app - covered in my books.
What is the rear natural frequency
I guess what I'm trying to say is how much lower should the rear of the vehicle be than the front. Right now it's about 2inches lower. I leveled it out and it didn't seem to feel as smooth.
@@wadeb8441 Did you watch the video?!
@@wadeb8441 As I said, measure the rear natural frequency at different ride heights. All else is just guesswork.