Stiff/soft suspension influence on braking
06-26-2015, 12:50 PM
#1
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Stiff/soft suspension influence on braking
How stiff/soft suspension influence on braking? (given braking on the straight line)
My intuition says soft front allows front to dive harder -> more weight on front -> better braking.
On the other hand - too much dive and rears will lose too much weight and ABS will go crazy.
On the contrary it seems to me that i've experienced that too stiff suspension can cause brakes lock up - which is the opposite to above statements.
So, which is right?
My intuition says soft front allows front to dive harder -> more weight on front -> better braking.
On the other hand - too much dive and rears will lose too much weight and ABS will go crazy.
On the contrary it seems to me that i've experienced that too stiff suspension can cause brakes lock up - which is the opposite to above statements.
So, which is right?
06-26-2015, 02:28 PM
#2
Originally Posted by Croc
How stiff/soft suspension influence on braking? (given braking on the straight line) My intuition says soft front allows front to dive harder -> more weight on front -> better braking. On the other hand - too much dive and rears will lose too much weight and ABS will go crazy. On the contrary it seems to me that i've experienced that too stiff suspension can cause brakes lock up - which is the opposite to above statements. So, which is right?
06-26-2015, 05:32 PM
#3
First, neither front nor rear spring or shock stiffness has an affect on the weight transferred from the rear wheels to the front under braking. The factors are the CG height, the wheelbase, and the mass.
The spring stiffnesses, front shock compression, rear shock rebound, and suspension geometry affect how much the rear of the car will rise as weight is transferred to the front an how much the front will dive as weight is transferred on to it.
Two soft or too stiff, especially with the shocks that affect transients, can affect grip. Too stiff can reduce front grip. That is the same effect too stiff will have on cornering. Shocks and springs that are too soft will let the car seem uncontrolled, at least in sudden maneuvers.
Note that some forms of racing use this to their advantage. A common oval track setup is known as 'big bar/soft spring'. In this setup, very soft front springs let the car, usually at a nominal 4" ride height, dive to let the front spoiler (or splitter if allowed) get next to the track surface. This has gone to the point where a 2x3 tube that ran under the front engine pulleys has been replaced by a .75" thick bar. The big advantage is on exit where a high rebound left front shock (always the inside shock) has high rebound keeping weight on the inside rear wheel for traction.
BTW, better braking is when the weight is distributed evenly, or rather in proportion to available grip. Cars with low CGs and a rear weight bias are usually the best at braking, at least assuming they have sufficient traction in front. An example would be a Porsche...or a Formula 1 car...a mid-engine Ferrari or McLaren...etc., etc., etc. I've never seen a test, but I imagine an STR S2000 with its larger front tires could probably significantly out brake an S2000 on stock size wheels and tires.
The spring stiffnesses, front shock compression, rear shock rebound, and suspension geometry affect how much the rear of the car will rise as weight is transferred to the front an how much the front will dive as weight is transferred on to it.
Two soft or too stiff, especially with the shocks that affect transients, can affect grip. Too stiff can reduce front grip. That is the same effect too stiff will have on cornering. Shocks and springs that are too soft will let the car seem uncontrolled, at least in sudden maneuvers.
Note that some forms of racing use this to their advantage. A common oval track setup is known as 'big bar/soft spring'. In this setup, very soft front springs let the car, usually at a nominal 4" ride height, dive to let the front spoiler (or splitter if allowed) get next to the track surface. This has gone to the point where a 2x3 tube that ran under the front engine pulleys has been replaced by a .75" thick bar. The big advantage is on exit where a high rebound left front shock (always the inside shock) has high rebound keeping weight on the inside rear wheel for traction.
BTW, better braking is when the weight is distributed evenly, or rather in proportion to available grip. Cars with low CGs and a rear weight bias are usually the best at braking, at least assuming they have sufficient traction in front. An example would be a Porsche...or a Formula 1 car...a mid-engine Ferrari or McLaren...etc., etc., etc. I've never seen a test, but I imagine an STR S2000 with its larger front tires could probably significantly out brake an S2000 on stock size wheels and tires.
06-26-2015, 06:28 PM
#4
As said before, spring rate changes how quickly load is transferred not how much load is transferred (to any large degree). But if you have soft springs with lots of travel your toe and camber changes can negatively effect your contact patch under braking. More rate can help with this.
If your locking up brakes with stiff springs, remember the loads transfer faster. You need to load your tires more carefully when applying the brakes. Or its possible your "too stiff", have bad shock settings or just low quality shocks.
.02
If your locking up brakes with stiff springs, remember the loads transfer faster. You need to load your tires more carefully when applying the brakes. Or its possible your "too stiff", have bad shock settings or just low quality shocks.
.02
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