I constantly see posts about what can one do to make their car handle better and every time the first thing that pops in my head is TIRES! Of course suspension components are important but tires are the most important part of the package. If for example I pick the wrong compound tires (all race tires to choose from) it can be the difference between an easy win and a “I almost crashed every corner” 3rd.
I just read an article in Grass Roots Motorsports (which you should be reading if you want to go around corners) and they had a great suspension/tire test on a Mazda MX-5. I know, it’s not a Mustang but the basics still apply.
In short here are the conclusions. And these times are with professional drivers:
OEM tires, 205/45R17 Bridgestone Potenza RE050A
Aftermarket tires, 225/45-17 Dunlop Direzza Sport Z1 Star Spec (and wider wheels).
1st Test:
Tires
OEM tires, 205/45R17 BridgestonePotenza RE050A)
Aftermarket tires, 225/45-17 Dunlop Direzza Sport Z1 Star Spec (and wider wheels).
OEM Suspension, tires, wheels.
Best lap: 58.07sec
Lateral G’s: 1.066g
OEM Suspension, Dunlop Direzza tires (not a race tire), 17x9 wheels
Best lap: 55.28sec
Lateral G’s: 1.191g
Pretty straight forward conclusion here. Better/more focused tires are a huge improvement, 5% to be exact. To put that in perspective if you had a bolt-on on a 300rwhp car that offered a 5% improvement it would be 15hp. Any bolt-on worth 15hp would be snapped up by everyone and their brother. Shorty headers, TB’s, X or H pipes and axle backs can only dream of making 15hp. And keep in mind, the tires limits were not reached during this test, the stock suspensions limits were.
Conclusion: 5% improvement
2nd Test:
Coilovers
K&W Variant 3 Coilovers
K&W Coilovers, OEM tires, wheels.
Best lap: 57.52sec
Lateral G’s: 1.086g
K&W Coilovers, Dunlop Direzza tires, 17x9 wheels.
Best lap: 54.10sec
Lateral G’s: 1.226g
Another straight forward conclusion here. With the stock tires the coilovers only improved the lap time .55sec. A WHOPPING 1% increase in performance. It is more than clear that high dollar suspension components are rendered about useless unless they have good tires to work with. Would you spend $2000 on coilovers and run them with OEM type tires for a 1% increase? Me thinks not. Another piece of data of note is that the car did a faster lap with a stock suspension and the good tires than the stock tires and coilovers. 2.24sec faster in fact!
3rd Test:
Swaybars
The swaybar test was done with the good tires and the coilovers on the entire time so you will not see any huge gains like were seen when the OEM and Dunlop tires were compared.
OEM Swaybars 21mm front, 12mm rear
Hotchkis Sport Swaybars 27mm-3 way adjustable, 21mm rear-3way adjustable.
K&W Coilovers, Dunlop Direzza tires, 17x9 wheels, OEM swaybars.
Best lap: 54.10sec
Lateral G’s: 1.226g
K&W Coilovers, Dunlop Direzza tires, 17x9 wheels, Hotchkis Sport swaybars set stiff front/soft rear.
Best lap: 53.48sec
Lateral G’s: 1.200g
As expected there was an improvement with the aftermarket swaybars. But it was only .62sec (1.2%) and this was with tires that could take advantage of them.
Conclusion(s):
There are lost of conclusions that can be drawn (and most likely debated) from this test.
-What sticks out to me more than anything is that tires are the most important part of a suspension combination. Bottom line, tires, tires, tires. The Dunlop’s out performed the OEM tire/Coilover combination by 2.24sec (4%!). That is a MASSIVE difference.
-The idea that swaybars help the car “handle” better has FAR more to do with what the driver is feeling through the car opposed to it actually going faster (handling better if you will). I constantly see posts about how someone’s new swaybars were a huge improvement because the car doesn’t roll as much anymore. But this test does a pretty good job of proving that they feel faster but when the stopwatch is put on them they are not much of an improvement at all. Body roll (as long as it’s not out of control) is clearly not a “bad” thing. That being said if you were to run swaybars and not upgrade the stock springs/dampers they would be a bit more effective (percentage wise) because they would add to the wheel rate which would not be getting done with higher rate springs. But swaybars are not supposed to be a Band-Aid for spring rates that are too low. I would love to have seen a test with the OEM tires, OEM springs/dampers and Hotchkis bars. I would bet money the improvement would be almost zero.
-Note that the fastest lap time did not show the highest G’s.
-The Dunlop’s out performed the OEM tires (which are not bad) by 2.79sec (5%).
-The coilovers out performed the stock springs/dampers with the stock tires by .55sec (1%)
-The coilovers out performed the stock springs/dampers with the Dunlop tires by 1.18sec (2.2%)
-The Hotchkis Sport swaybars out performed the OEM swaybars by .62sec (1.2%)
I found the article very interesting from a technical standpoint and I thought that for those of you that are not flush with suspension data (opposed to “mine feels better” crap) that it could shed some light on what works, what doesn’t, how much it works, what works best, etc.
That being said suspension can not be broken down into just one test like this. There are no “rules” in here (aside from good tires being unquestionably the most important component in the system) but there is a lot of good data to draw from when making buying decisions. Here is a short list of what I think the order of importance is when modding a suspension. This list applies to most situations, not all. Suspension is not that easy.
-Geometry:
This is the angles and pick up points of the suspension. Some can be improved fairly easily (caster/camber plates), some are a huge operation (double A arm front suspension). Under the classification are things like control arms and bushings. If they are flexing under load the geometry is changing. Geometry is unquestionably the foundation of a suspension.
-Springs:
Springs “are” your suspension. They determine where your geometry is based on load. If they are way too stiff the suspension will not move and go through the geometry changes that it needs to do things like transfer weight. If they are too soft they will move too far for a given load which will put the geometry where you don’t want it and also possibly bottom out. Spring selection is paramount. During race weekends I am constantly swapping out springs to “tune” the suspension. Because springs determine where the suspension geometry is for a given load they can be considered “soft geometry”. So their importance is obvious.
-Dampers (shocks/struts):
First and foremost the dampers job is to control the springs. After that their rates need to be set up to control the un-sprung weight (wheels/brakes/etc). And if it is a high downforce car there are all sorts of tricky valving things that can be done that will allow for them to operate normally but “blow off” when encountering large bumps which create high shaft speeds.
-Swaybars:
The job of swaybars is greatly misunderstood. But that is because they can be used in a lot of different ways. I could write pages on all the different ways to balance springs and swaybars together but because most of you reading this are not going to be at the track trying to shave tenths I’ll keep it basic. Swaybars are there to do two main things. One is to reduce body roll. A swaybar allows you to reduce body roll without having to run heavy springs. But swaybars are not a replacement for good spring rates. The second job of swaybars (adjustable ones) is to allow for adjustment of the chassis balance. With swaybars the car can be tuned to understeer (plow the front), run neutral (all four tires pushing the same) or oversteer (tail out). In my opinion spring rates should be picked first and then swaybars. If I had a choice I would run higher rate springs and lower rate swaybars and use the swaybars mostly to tune the cars balance.
And last but not least, the driver. Off the showroom floor these cars are better than 99% of the drivers out there. That is a fact. The best investment that 99% can make in their suspension is to attend a driving school or two. Obviously I spend most of my time at the track on bikes but on occasion when there are two tracks on the property there will be cars on one and bikes on the other (Autobahn, VIR, NJMP, Vegas, etc). I can’t tell you how many times I have seen cars like Neon’s, GTI’s Civic’s, old school BMW 3 series, etc running circles around full blown race cars, Vipers, Porsches, Ferrari’s, etc. It’s obvious what the difference is…..the driver.
