As most of you know my “Tips of the Week” often come from my track experiences helping out other racers. In my experience many of the simple adjustments we can make to our cars are often over looked by the less experienced racer(s). I ran into 2 guys this weekend both having different problems both caused by ride height issues.
Driver #1: This driver was entered into the 4wd SC Truck class. He was having an issue where his car had no forward grip and it would donkey kick over the triple jump on the track, bad. His shock oil/spring package was the same as the guy sitting in P2 after 2 rounds of qualifying. Driver #1 was nearly out of patience at this point, and asked for my opinion. Right away I could see an issue with his truck. The front of the truck was nearly 4mm higher than the rear. On top of that the truck was a sitting very low for the 4wd SC class, 20mm. I grabbed the JConcepts ride height gauge and set him up at 25mm rear, 26mm front. I’ll talk about the “Rake” later. For Q3 I told the driver to take as many warm up laps as he could to get a feel for the truck. He managed 3 laps and I could tell he was going to have a much faster run this go around. He not only bested his qualifier overall by 15 seconds, he set the fastest lap of the round in this class!
Driver #2: A young driver asked me to look at his car and help sort out why he couldn’t carry as much speed as the rest of us were coming off the high speed sweeper. He was running a D413 and looked to have a somewhat regular setup on the car. Again however it was immediate to me his ride height was wrong. This time the ride height was too tall. He was sitting around 25mm which was 5mm taller than I was running on my Yokomo. Come to find out he had another manufactures springs on the car and both front and rears were too long to get down to 20mm ride height. So a quick spring change back to stock HB springs and were in business. This driver also ran his best round in round 3 and would do quite well in his A-main I found out later.
So what are we learning here? Ride height is simple to adjust on todays’ cars. 99% of them have adjustable screw style spring collars right out of the box. So you have no excuse to not make these changes in testing, it takes 20 seconds to give a few turns up or down. A few tricks and tips to ride height:
- Always always always check your ride height with the tires you plan to hit the track on. It may not seem like much of a difference between brand A tires and brand B tires but you’d be surprised when you measure them. Set ride height with a car that is “Race ready” and ready to hit the track. This means battery/fuel and the body. SC truck is the only exception here since it’s often difficult to reach the spring collars under the body.
- Mark your spring collars to help aid in quick adjustments. I personally do this by running the spring collar all the way up to the top of the shock body. Mounting the shock to the car and “scribing” the shock collar with a file to give me a nice mark I can see. This removes the anodizing and allows me to count my turns if I need to call out to a fellow racer for quick adjustment.
- Check your ride height often. Springs will soften/fatigue over time especially when new. New springs will take a “set” after a few days at the track. So check it often. I check ride height every time I get to the track and start running.
What does adjusting ride height do for the car? Here are a few examples:
Generally speaking a car that is sitting at lower ride height will “roll” less which will provide less traction because it’s not rolling. This can be helpful on a very high bite track where you want to prevent the car from traction rolling. This can be taken too far however to the point where the chassis is scrubbing all over the track. Not only front to back but side to side. So pay attention to the chassis after your run and see if you’re picking up dirt, etc.
A car sitting at higher ride height will have the converse affect. It will roll more providing more grip/traction. This is very helpful on a track with low grip where traction is sought after at a premium. Like all adjustments it can be taken too far. Ride height set too tall will cause traction rolling and a very “tippy” car off center. It will often be overly sensitive to steering inputs as well.
Some general tips:
Tracks that are bumpy often require a higher ride height whereas a smooth track can run a lower ride height setting.
If your car is jumping nose down severely this is often referred to as “donkey kicking” and is often caused by the rear part of the chassis slapping the jump face abruptly. This can be from your ride height being too low. It can also be caused by the wrong dampening and spring package.
If you find your car isn’t carrying as much distance off of a jump as the other racers your car maybe sitting too low also. This is caused by the chassis “scrubbing” the jump face and slowing down too much.
Running one end of the car lower than the other can provide more/less weight transfer rate to the “higher” end of the car. So if your car is over steering a bit under braking or while slowing down, you can raise that end of the car and help reduce the speed/rate of the weight transfer. It doesn’t take much, 1mm at a time. Note that if you find your 2 to 3mm higher to one end, you likely need to make other adjustments. **I have not personally found anything more than 2mm difference to be the “right” setup choice in most cases.
Anytime you change your ride height, be sure to check your camber and toe settings. These will move since they’re tied to the attachment points on the car, obviously affected by it moving up/down. It may be slight, but check it none the less.
As with any chassis adjustment, there’s give and take. Something gained often means something lost. Make sure you’re gaining the result you wanted from your car while losing the unwanted characteristic.