A bumpsteer kit is a lot like insurance: Once you realize you need it, it's probably too late.
When racers talk bump steer, most of the time we associate the term with autocross or other forms of road racing. This isn't unfounded: Bump steer is easy to observe in these applications: You're usually dealing with vehicles that are lowered, pushing the limits of adhesion and encountering uneven pavement surfaces. If the wheel jerks when you don't expect it, it can quickly spell disaster, and if you're involved in road racing on any serious level, you probably know at least one person who has either blown a race or wrecked their car due to bump steer. I won't embarrass Joe Charles in this blog post =o)
But what if you're drag racing? Does bump steer matter? You're damn right it does!
Before we go too far into discussing why, let's jump back and describe what bump steer is. Many of you probably already know, but for those who don't, this will be helpful. The simplest definition I've seen comes from the folks at Long Acre Racing--who I might add-- were kind enough to grant us access to use their content:
"Bump Steer is when your wheels steer themselves without any input from the steering wheel."
Simple enough, right? Scenario: You're coming into a corner, braking, turning in, you hit a light bump and the wheel jerks one way or the other. It might be barely noticeable, or it may try to pull the wheel out of your hands. Either way, it's not good. (Unless you're using some advanced techniques to deliberately create small amounts of bump steer to maintain a contact patch--something you still need a bumpsteer kit for--but we're not going that deep today.)
Some of you reading this are pretty damn talented racers. Those of you who are, especially with the faster cars--you know how scary it can be to have to make unexpected, last minute steering corrections. Some of the causes for those corrections are ridiculously obvious and you're going to have to deal with them no matter what: Wind, track conditions, tire inflation, traction, etc... You're going to deal with those things no matter what. Why complicate things with bump steer?
Before we go deeper into drag cars, we should probably talk about what causes bump steer. We defined bump steer as "when your wheels steer themselves without any input from the steering wheel", but we didn't discuss the cause.
Bump steer is not the road's fault. It is the fault of the person building and driving the car. I've heard many people say: "Well, the track is smooth, so I don't need a bumpsteer kit." That's bullshit.
Bump steer occurs during compression and rebound of the front suspension, when the angle of your tie rod ends are not on the correct the center line with the the lower ball joints. Below is a diagram from Long Acre Racing (Thank you for your permission to post this!) which shows the angles between the pivot points. Changing springs, tires, k-member, steering rack, lowering the vehicle, etc. all affect this geometry.
When this geometry isn't correct, a very common issue on drag cars, you'll often get bump steer, especially in the first 1000': Your wheels then toe in and out during compression and rebound, causing the car to work against your steering input.
Imagine this: Your car is in the air on on a 2-post lift. You've spent $50K on the car this season alone, trying different transmission, converter, gear and tire options, plus hours of tuning and dyno time. You're under the car admiring your hard work and making sure everything is dialed in before the race season starts.
As your suspension sits unloaded on the lift, the front wheels toe out. But you don't know this because you never checked your bump steer and likely never gave it a second thought, so you lower the car back to the floor.
At this point, now that the suspension is loaded, you don't have any toe out and perhaps have a slight toe-in. This is going to look normal on the alignment rack. You can make as many adjustments to toe in/out as you want on the stock tie rod ends, but it's not going to affect bump steer if the suspension geometry isn't correct. All that is going to do is give a reasonable expectation that you're going to roll straight with the suspension at rest.
Are you starting to see the picture?
If toe in/toe out changes significantly when the suspension loads or becomes unloaded, it's going to fight against the straight path you're trying to follow.
Think about what happens in a drag pass: I won't ask for a show of hands, but how many of you have watched a drag car lift the front end and unload the suspension, then "land" and load it, then compress it to the max, then partially unload it again before reaching the 1000' mark?
Check out this photo of Justin Jordan's car. The front suspension is completely unloaded. If those wheels are toe in or toe out, that's how they are going to be when they hit the ground again--that's steering corrections that will need to be made at extremely inopportune times.
Then, when the suspension settles, Justin may experience a different phenomena (toe in/out in the opposite direction) and he may have to make a different correction. If worries like this can be avoided by checking and adjusting your bump steer, why wouldn't you do it?
It all comes down to this: You've got a heap of money wrapped up in your car. You've got the best tires, wheels, you've built the motor, spent thousands on a roll cage, safety equipment and you burn $20 per gallon race fuel. Why risk everything on the stock tie rod ends with the lower pivot angle maxed out? Why the hell aren't you running a bumpsteer kit or at least making sure you've achieved zero bump steer with the stock tie rod ends?
Here is a better question: Why haven't you at least measured your bump steer?
Maybe you don't have any. If so, that's great, but I'd venture to guess it's more of a problem for you than you think.
You've got different wheels, tires, springs, ride height, an aftermarket k-member and a manual rack. This will collectively change the center line in some way--probably in a major way, guaranteed. This isn't to say you can't get lucky: Sometimes, a car will have some bump steer in stock form, and your front end components come together and somehow arrive at zero bump steer. It does happen, but it's pure, haphazard luck. Again: How do you know if you haven't measured it?
Measure your bump steer and dial it in properly. Companies such as Long Acre Racing have toe plates, precision bump steer gauges, which will help get you dialed in for a very reasonable price. These tools save lives in racing.
Of course, if you need a bumpsteer kit for an S197 mustang, you should buy ours!
The FerraroSpeed S197 bumpsteer kit is designed and built on US soil with the highest quality components and the best heim joint money can buy. The unique, shimless design allows you to fully adjust the kit on the car. It's a no-brainer for any drag, road course, or even street lowered S197 mustang
It's $289 shipped and worth every penny! Check it out HERE
If you have questions, email us: info@FerraroSpeed.com