understeer after coilover install?
- Thread starter jmd2914
- Start date
There could be a million reasons for this.
The alignment could be off
If the ride height changed this affects instant center and tire loading.
If you stiffened the rear more than the front this can cause this issue. Typically if you stiffen one end the other end gets more loose.
Or you could simply be overpowering the tires you have.
The alignment could be off
If the ride height changed this affects instant center and tire loading.
If you stiffened the rear more than the front this can cause this issue. Typically if you stiffen one end the other end gets more loose.
Or you could simply be overpowering the tires you have.
Well it depends. I assume that the CO's increased your front wheel rate. If that is the case your swaybar may be too much. Wheel rate is a function of spring rate and location. A 1000 pound spring (really stiff) in the stock location is equal to about a 250 lb spring on the CO (what I'm running on the street). I don't have the formulas right in front of me but I'll dig them out and post them up so you can figure out what change happened in the front and the back as you need less CO spring than you do stock location spring for the same wheel rate.
Now I changed to a new sway bar both front and back shortly after I went to CO's (front only) on an 83. The sway bars are different in different years and I can't remeber right now if they are stiffer or lighter. My problem was more of an oversteer condition but I changed several things when the sway bars went in so I can't say for sure what was the fix was.
I now have a power off understeering/power on oversteering condition on the street. This was a trade off for getting the car better balanced for the autocross. I set the shocks stiffer and change the camber and toe on the autocross.
Now I changed to a new sway bar both front and back shortly after I went to CO's (front only) on an 83. The sway bars are different in different years and I can't remeber right now if they are stiffer or lighter. My problem was more of an oversteer condition but I changed several things when the sway bars went in so I can't say for sure what was the fix was.
I now have a power off understeering/power on oversteering condition on the street. This was a trade off for getting the car better balanced for the autocross. I set the shocks stiffer and change the camber and toe on the autocross.
Ok this is for a 79-2004 Mustang.
Front:
Stock spring: spring rate X.25= Wheel Rate
CO: Spring rate X.90= Wheel Rate
Rear:
Stock: Spring rate X.49=Wheel Rate
CO: Spring rateX1.10=Wheel Rate (this is because the spring is behind the axle)
I also found the sway bar charts.
Mustang Anti-sway Bars
Take a look through all the pages on this site. This is great information on the Mustang.
Front:
Stock spring: spring rate X.25= Wheel Rate
CO: Spring rate X.90= Wheel Rate
Rear:
Stock: Spring rate X.49=Wheel Rate
CO: Spring rateX1.10=Wheel Rate (this is because the spring is behind the axle)
I also found the sway bar charts.
Mustang Anti-sway Bars
Take a look through all the pages on this site. This is great information on the Mustang.
67coupe
Founding Member
Brian's already posted the answer.
Typically, the end of the vehicle with the highest roll stiffness (wheel rate + sway bar rate) will loose traction first. In your case, the front roll stiffness increased due to the new wheel rates with the coil overs. This is, most likely, the reason for the increased understeer. As you mentioned, MM does recommend going with a softer front bar to increase front end grip and maintain front to rear balance with the coilovers.
You could also increase the rear bar stiffness but this would decrease rear grip to eliminate the understeer.
Nice link Brian. Is the 84 V8 front bar a "bolt-on" swap for my 89? I also want to eliminate my understeer. I know the SN95 bars require different mounts when fitted to a fox.
Typically, the end of the vehicle with the highest roll stiffness (wheel rate + sway bar rate) will loose traction first. In your case, the front roll stiffness increased due to the new wheel rates with the coil overs. This is, most likely, the reason for the increased understeer. As you mentioned, MM does recommend going with a softer front bar to increase front end grip and maintain front to rear balance with the coilovers.
You could also increase the rear bar stiffness but this would decrease rear grip to eliminate the understeer.
Nice link Brian. Is the 84 V8 front bar a "bolt-on" swap for my 89? I also want to eliminate my understeer. I know the SN95 bars require different mounts when fitted to a fox.
That I'm not sure of. I know there are differences in the K members and the front control arms. I have the 87-93 arms on the stock 83 K.
The sway bars I bought are Eibach, were listed for a 79-93 and bolted right into the front. The rear was a different story but that was due to the control arms I'm using.
