OldSchoolSwap
08-06-2002, 12:47 PM
Bottoming out of the front suspension
The single most common problem we encounter on race cars is bottoming out of the front suspension. It is suprisingly difficult to detect sometimes. This problem can really frustrate you, in fact, a frustrated team and driver can be one of the symptoms that the car is bottoming out! Most cars have more rear suspension travel, so bottoming out of the rear suspension is less common, and is actually easier to detect because of severe and sudden oversteer. Bottoming out of the front suspension can be much more subtle and gentle.
I have listed the most common symptoms and causes separately, with the most common listed first.
Symptoms of bottoming out the front suspension.
The car is unresponsive to changes made to the front suspension. A particularly good clue is that softening the front sway bar makes the car understeer the same or worse.
The car understeers more if you try to go faster, especially in mid-turn after the chassis takes a set. Don't confuse this with braking too late.
The car understeers more after only 2-3 laps. This is a sign that the front tires are overheating very quickly., indicating that the cars is way too stiff, perhaps because of bottoming out.
Just to be sure, wrap a nylon tie around the strut or shock, to indicate travel, then drive a few test laps. Absolutely avoid any bump or curb which would artificially push the nylon tie to the top of the shaft, and then pull in to see if the nylon tie has been pushed to the very top. This may mean driving off line and slowly everywhere but the places where you suspect bottoming.
Causes
The most common reason for bottoming out the front suspension is that the car is simply too low for the existing front strut or shock length. This is true even with very stiff springs. See our catalog for solutions.
Bump stops could be too long, especially stock hard rubber ones that can steal 2 or 3 inches of travel. Bump stops should benefit the car, not make it worse.
Front spring rate is too soft. Especially common with street springs that have been cut. This can be especially confusing because all the books say that stiffer front springs will make the car push, which is not always true.
Front springs coil binding. This is rather uncommon, but it does happen. You can see this by looking carefully at the individual coils where they could touch.
The single most common problem we encounter on race cars is bottoming out of the front suspension. It is suprisingly difficult to detect sometimes. This problem can really frustrate you, in fact, a frustrated team and driver can be one of the symptoms that the car is bottoming out! Most cars have more rear suspension travel, so bottoming out of the rear suspension is less common, and is actually easier to detect because of severe and sudden oversteer. Bottoming out of the front suspension can be much more subtle and gentle.
I have listed the most common symptoms and causes separately, with the most common listed first.
Symptoms of bottoming out the front suspension.
The car is unresponsive to changes made to the front suspension. A particularly good clue is that softening the front sway bar makes the car understeer the same or worse.
The car understeers more if you try to go faster, especially in mid-turn after the chassis takes a set. Don't confuse this with braking too late.
The car understeers more after only 2-3 laps. This is a sign that the front tires are overheating very quickly., indicating that the cars is way too stiff, perhaps because of bottoming out.
Just to be sure, wrap a nylon tie around the strut or shock, to indicate travel, then drive a few test laps. Absolutely avoid any bump or curb which would artificially push the nylon tie to the top of the shaft, and then pull in to see if the nylon tie has been pushed to the very top. This may mean driving off line and slowly everywhere but the places where you suspect bottoming.
Causes
The most common reason for bottoming out the front suspension is that the car is simply too low for the existing front strut or shock length. This is true even with very stiff springs. See our catalog for solutions.
Bump stops could be too long, especially stock hard rubber ones that can steal 2 or 3 inches of travel. Bump stops should benefit the car, not make it worse.
Front spring rate is too soft. Especially common with street springs that have been cut. This can be especially confusing because all the books say that stiffer front springs will make the car push, which is not always true.
Front springs coil binding. This is rather uncommon, but it does happen. You can see this by looking carefully at the individual coils where they could touch.