With a gripped-up setup, the histograms are really populated and the suspension is really moving around. Note how much weight is transferred to the rear and how the rear tires are really working on these cars. The histograms are much more centered now.
In addition, you can look at your shock pot raw data for problems. You can spot severe bottoming by looking for flat spots or even plateaus. This can be addressed with more high-speed compression or if it is severe and frequent, more spring rate. If you see an overshoot in the suspension movement after a bump event, that can be cleaned up with more rebound, usually more low speed. You can look at the time vs the displacement and see if the problem is more low than high speed. You can also look for ride height trends, if the chassis is ratcheting downward then too much rebound may be the issue. Look at your histograms before and after tuning out these issues and make adjustments to tune them up. In my experience, cars with nice symmetrical histograms don’t have many spot or segment problems
Not much information is out there on how to set up cars with a lot of aero load. Before this was not much of a factor but nowadays there are quite a few cars in the time attack world that can make over 2000 lbs of downforce. High-downforce cars have some interesting things that have to be considered. For a car with a lot of aero, it is inevitable that you are going to be running on your bump stops. You can control when it hits with these plastic packers that you can place under the bump stops. We use these to limit travel so the suspension won’t travel to the point where the front edge of the splitter will cut off the underbody airflow and stall out the diffuser. In fact, we usually use the packers to make sure the car settles on the bump stops slightly nose high to ensure you won’t have aerodynamic pitch problems with the splitter. This usually has less front downforce and perhaps slightly less overall downforce. It will probably make the car have a slight aero push at high speeds but it will be easier to drive and it won’t suddenly stall the diffuser and lose rear grip!
Having good bump stops is essential, especially with a high aero-load car. We prefer to use MCU or microcellular urethane as these are nicely progressive and still allow some suspension movement. This is important for a car with a lot of aero as it transitions from mechanical to aero grip as it settles on the bump stops. MCU makes the transition smoother. We prefer this bump stop from Professional Awesome. They are validated through fatigue testing and can take many load cycles before mushing out and disintegrating. They also have a tested spring curve and the data is available from Professional Awesome. Lately, even if the shocks we are using come with decent MCU bump stops we switch them out for these parts.
With packers and good bump stops, playing with the high-speed compression and the blowoff can yield some amazing results for smoothness and driveability in the zone between aero and mechanical grip making the transition more transparent for the driver. When working in this area try using more, then less damper control and see how the chassis is responding. Look at lap times and segment times and work on problem areas that your driver and data system might reveal.
I hope this series has been useful for you in demystifying the use of adjustable shock absorbers and can help you in troubleshooting and improving your own setups. I know that proper use of shocks is the source of some of the cheapest and more low-hanging fruit of all the speed secrets. This information is pretty golden and I guess we can see how gets out there in this age of people not reading anymore!
Once again don’t forget to read below!
How to Adjust Your Shocks, Part One- Single Adjustable Shocks
How to Adjust Your Shocks, Part Two- Double Adjustable Shocks
9 comments
“KW and ST Suspension also have really good baseline settings for all of their products in the enclosed instructions.”
I did email KW a couple months ago, to ask what were the default settings on my KW v3’s, and the response wasn’t that, but rather to just start at full soft and work your way up +2, until it’s too stiff, then back off -2 or -1. No defaults were listed in the manual that I could find. In fact, I found the manual of theirs rather lacking. I ended up crowd sourcing some settings, started there, and ended up with something that is 90% there to my liking… I just need more time behind the wheel now to fine tune.
That being said, thank you thus far for the excellent content on this topic and each part you’ve created. Super valuable.
Next article could be on re-valves or choosing spring rates, why you want them, and how it relates to road or track performance. e.g. I recall reading examples of “abnormally,” high spring rates that would hurt you back, but with proper valving, was perfect to match the driving profile of the car.
The reality is that on the street, you’re not tuning for a time, you’re tuning for a driver and a road.
If you have crappy roads, and an older driver, you are going to go softer.
If you have smooth roads and a younger driver you can crank up the stiffness.
One thing I will say, is chuck the sway bar on your driven wheels and do roll control through the damper/spring. Its going to really suck up the bumps that way. I think super stiff sway bars are the work of the devil.
You can also find that stuff online on their website. Usually asking people on forums, etc is less than satisfactory. What I think is odd is that OEMs think 10% more spring is a lot, I mean we can go 100% or more stiffer, and with the right stuff, it can sometimes ride pretty nicely, even on the street. I sometimes am reluctant to write about some stuff that I develop. It’s what makes me valuable and it’s stuff I have figured out. I don’t mind writing about standard best practices in racing though.
Hi Mike,
Thanks for the information as always. Just one question and this might be a little off topic but when you tune your suspension bump , ride height and droop do you disconnect the swaybar? I have seen somewhere where they disconnect the sway bar when tuning and getting the measurements on these things but I can’t make sense of the fact why you have to disconnect it when you ran it on track with it on. If you can enlighten me on this please that would be great. Thank you so much.
No., only for corner weighting.
I really do appreciate these guides; I understand there’s a lot of nuance and tricks but for talking about your bread and butter it’s great that you’re giving good useful information other than “well more than one clicker and you need a data system” or “I’d be happy to help for my hourly fee”
On the second to last and last pages, I notice you had some histograms built in Motec’s software and then others in Excel – do you have any other data analysis software packages you prefer, or do you just have some macros and workflows in Excel? I tend to live in Excel for data acquisition analysis on my day job, but I can easily see how there’s, at least in theory, faster and smoother ways to do things.
Actually it’s not excel, its AIM race studio 3. Motec seems to be less glitchy. AIM always had tons of updates and patches and stuff not working.
Oh, I see why I assumed Excel… OK thank you.
actually race studio 2