What is corner balancing?
Corner balancing is the process of shifting weight around in the car and adjusting corner heights to obtain a desired 50/50 cross-weight percentage, ultimately making the car perform equally in left and right turns. The weight you shift in the car is usually the battery, but can also include ballast, the fuel cell, oil accumulators, and fire system tanks. You want to place these items in areas of the car that is lighter than the rest to off-set the weight from the driver and drive-train components. Ideally, these items should be kept within the wheelbase of the car, and not placed in the far corners of the trunk or engine bay to prevent a pendulum effect. After relocating everything possible the ride heights are adjusted to create a 50/50 cross-weight percentage.
When I installed the BC Racing coilovers I decided not to do the corner balancing right away. Instead, I started with the weight reduction and testing spring rates, this way I didn't need to get re-adjustments after every change. Once I had removed a lot of weight from the car and settled on the 5k springs, I set an appointment with Bret at Yawsport for corner balancing. I also asked him to do a thorough inspection of the car to verify everything was optimized. We made the 50min drive to his shop in Ramona CA to drop off the car, and anxiously awaited his updates...
The following day I get a message that the balance was pretty far off, (maybe 3% if I remember correctly) and he is unable to correct it any further due to lack of adjustment in the rear. I'm told I need to purchase ANOTHER set of Swift springs since I was sent the 7" instead of 6". When I installed the Swift springs last year I did notice that they took up almost all of my adjustment to set the ride height, but I'm a noob and didn't think anything more of it at the time.
I emailed BC and was told to call their tech support hotline, I tell them my situation and they begin to look up the part numbers to verify I was sent the correct springs. It turns out that they did send me the correct parts listed in their catalog, and because my springs were installed we couldn't do an exchange. I'm not sure if this is a isolated problem for me because my car is much lighter than stock, or if anyone else with a Yaris and these DR's have run into any issues like this.
I told Bret to do whatever was necessary to get the car balanced, he ordered and installed the new springs and had the car balanced by the following day.
I was a bit annoyed about having to buy a second set of the same springs, and Bret gave me the appropriate "I told you so" talk in regards to testing a new set of coilovers. He had warned me plenty of times, but I wanted to test something other Yaris owners could attain easily with good results. Well, that's how it goes I guess, all is well now and It didn't cost too much to do some valuable R&D. haha.
You can see in the photo above that we are now at a 50% cross weight with a driver ballast, and everyone mentioned it was going to be a huge improvement. Bret gave me a list of improvements I can do to the car, including getting that LSD as my main priority. We talked about the future of our local SCCA region and how we can make another round of spring rate changes next year when we know more about venues.
So what are the differences?
On the drive home the car felt amazing, it was like the front and rear suspension were working together now. Before, anytime I went over dips or large bumps it felt like the back of the car would rebound off the bump pretty hard. This is the reason I had to turn the dampers down to 5 clicks to drive it on the street, but now I was able to keep it at my race setting and not get beat to death. Interesting.
Our first race after the corner balancing was the 2018 Match Tour, and I noticed right away that the car felt loose. I was struggling to hold the car composed through the slaloms, but it was easily correctable so I kept rolling with it. It wasn't until my co-driver spun the car that we made some changes, we turned the rear damping down from 16 to 12 and that seemed to solve the problem. We will continue our tuning process at the next event and refer to the results to verify we going in the right direction. You can check out the Match Tour video below:
Coilovers are an amazing tool for tuning a car's suspension, but don't think for a second that you can just install them without ever messing with them again. If you're buying coilovers to slam a car and go hard-park at meets then that's fine, but to me, that seems like a waste of such a functional product. For those that want to race you need to properly install and set preload, test-n-tune the dampers, figure out spring rates, and corner balance the car. Everything you change will affect how the car behaves, so be prepared to repeat this process as your project advances. I highly recommend you get in touch with Bret and discuss your suspension goals, and listen to what he recommends the first time so you don't have to learn the hard way like me.