The Magic 2 inches of suspension travel on an FD
04-28-15, 09:45 AM
#1
The Magic 2 inches of suspension travel on an FD
I know its been mentioned before that 2 inches of travel is the ideal for the FD .
Where I believe its the most gains .
Now my car is going a bit over that , it will on occasion or a hard bump gently tap the bumpstops .
I did the tie wrap trick but since on the ocassional HARD bump on the tracks i;ve been running its kind of skewed results
I can stiffen up my rear shocks quite a bit in order to achieve the magic 2 inches of travel .
But before I go into that . I'd like to understand why its the ideal number .
car is currently understeering a bit so I'm forced to stiffen the rear to fix it , if I soften the front i eat through wiring on the harness .
My aprehension is that despite the slight understeer , the car is currently setup the best its ever been and I have good traction for powering out of corners .
Where I believe its the most gains .
Now my car is going a bit over that , it will on occasion or a hard bump gently tap the bumpstops .
I did the tie wrap trick but since on the ocassional HARD bump on the tracks i;ve been running its kind of skewed results
I can stiffen up my rear shocks quite a bit in order to achieve the magic 2 inches of travel .
But before I go into that . I'd like to understand why its the ideal number .
car is currently understeering a bit so I'm forced to stiffen the rear to fix it , if I soften the front i eat through wiring on the harness .
My aprehension is that despite the slight understeer , the car is currently setup the best its ever been and I have good traction for powering out of corners .
04-28-15, 04:24 PM
#3
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i don't know anything about the FD specifically, but i'm skeptical of magic. every car we've ever run has been faster lower. when they hit the bump stops, it gets inconsistent and twitchy, so its best to keep it off the bump stops.
that being said the difference, between as low as it can go and like 2" higher, is really small, so don't be afraid to raise it up if you need it.
that being said the difference, between as low as it can go and like 2" higher, is really small, so don't be afraid to raise it up if you need it.
04-29-15, 01:03 PM
#4
i don't know anything about the FD specifically, but i'm skeptical of magic. every car we've ever run has been faster lower. when they hit the bump stops, it gets inconsistent and twitchy, so its best to keep it off the bump stops.
that being said the difference, between as low as it can go and like 2" higher, is really small, so don't be afraid to raise it up if you need it.
that being said the difference, between as low as it can go and like 2" higher, is really small, so don't be afraid to raise it up if you need it.
04-29-15, 03:36 PM
#6
650f / 500 r , GAB R shocks 8 way rebound / compression adjustable ,
fronts I'm running on 6/8 , and rears are being run on 3/8
I have a racing beat front sway and stock rear sway
alignment is -2.5 f , -2.3 rear 0 toe , up front , and a tiny bit of toe in in the rear , with 4.5 degrees of caster
fronts I'm running on 6/8 , and rears are being run on 3/8
I have a racing beat front sway and stock rear sway
alignment is -2.5 f , -2.3 rear 0 toe , up front , and a tiny bit of toe in in the rear , with 4.5 degrees of caster
04-29-15, 04:25 PM
#7
the spring rate is why you have so much travel, I have pettit tuned k sport coilovers, custom valving, spring rate of 12k front 10k rear, 3 clicks from full soft rear, and 6 clicks from full soft front and I am right in the sweet spot of wheel travel and my ride quality is awesome. I am at 25.75 ride height. you want the rear lower control arms to be parallel to the ground. that is where optimal suspension setup is at
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04-30-15, 01:17 PM
#8
First things first- move the wiring harness up above the sheet metal on the front fender.
--------------
I agree there is no magic ride height/travel.
You don't want to be on bumpstops in your normal maneuvering if your class allows you to change spring rate independent of bumpstop.
You can go low and stiff or higher with more compliance- it is a driver preference.
---------------
What tires/size and pressures do you run?
Doe others run that much rear camber on an FD?
Now the bumpstops are an ocasional tap in the rear .
IMO the understeer could be a corner entry front bumpstop issue
or
a balance issue you created in the rear settings trying to work around corner exit oversteer.
It seems with your current set-up-
you are trying to choose between too much rear camber (when you limit rear travel by raising compression damping) or getting on the rear bumpstop (but your high rear camber to allows you too run this much rear travel with good traction... right up to the moment you get on bumpstop and get unpredictable oversteer *worst kind*).
Since you don't mention hitting front bumpstop but do mention hitting rear bumpstop-
My gut is stiffen the rear and run equal tire pressures front/rear, but also take out 0.75 to 1 degree rear camber.
In my mind this would decrease understeer at turn in through chassis balance (the rear will start gaining slip angle the moment you turn in), but still provide good traction at corner exit.
Stiffening compression with damping is a compromise, I agree it would be nice to get more spring on the car.
----------------------
Best thing is to get a friend to take pictures of your car, especially on the sections of track where you wish it were doing something else.
Pictures will show.
--------------
I agree there is no magic ride height/travel.
You don't want to be on bumpstops in your normal maneuvering if your class allows you to change spring rate independent of bumpstop.
You can go low and stiff or higher with more compliance- it is a driver preference.
---------------
What tires/size and pressures do you run?
Doe others run that much rear camber on an FD?
Now the bumpstops are an ocasional tap in the rear .
IMO the understeer could be a corner entry front bumpstop issue
or
a balance issue you created in the rear settings trying to work around corner exit oversteer.
It seems with your current set-up-
you are trying to choose between too much rear camber (when you limit rear travel by raising compression damping) or getting on the rear bumpstop (but your high rear camber to allows you too run this much rear travel with good traction... right up to the moment you get on bumpstop and get unpredictable oversteer *worst kind*).
Since you don't mention hitting front bumpstop but do mention hitting rear bumpstop-
My gut is stiffen the rear and run equal tire pressures front/rear, but also take out 0.75 to 1 degree rear camber.
In my mind this would decrease understeer at turn in through chassis balance (the rear will start gaining slip angle the moment you turn in), but still provide good traction at corner exit.
Stiffening compression with damping is a compromise, I agree it would be nice to get more spring on the car.
----------------------
Best thing is to get a friend to take pictures of your car, especially on the sections of track where you wish it were doing something else.
Pictures will show.
04-30-15, 01:36 PM
#9
I kind of have a shot a picture compilation , BUt it wasnt exactly taken at a track...
Powerhead Productions - killboy.com at PhotoReflect.com - Dragon Photos-Sunday-April 19, 2015-killboy.com follow the sequence up until picture 62 . Tell me if you can see anything , I saw the same pictures and it looked like the rear was maybe getting a bit more travel .
Also I did move the wire harness over the actual fender guard area and its wrapped securely , I'm rubbing the harness in the front of the fender right before it goes under the headlights ( only on driver side ) right after the harness meets up with the windshield wiper fluid harness. after raising the car , and stiffening the front shock a bit it stopped rubbing . and yes could do that remove a bit of rear camber
Powerhead Productions - killboy.com at PhotoReflect.com - Dragon Photos-Sunday-April 19, 2015-killboy.com follow the sequence up until picture 62 . Tell me if you can see anything , I saw the same pictures and it looked like the rear was maybe getting a bit more travel .
Also I did move the wire harness over the actual fender guard area and its wrapped securely , I'm rubbing the harness in the front of the fender right before it goes under the headlights ( only on driver side ) right after the harness meets up with the windshield wiper fluid harness. after raising the car , and stiffening the front shock a bit it stopped rubbing . and yes could do that remove a bit of rear camber
Last edited by Tem120; 04-30-15 at 01:40 PM.
04-30-15, 02:33 PM
#10
From looking at the pictures I would swap wheels/tires front to back and get a stock front swaybar.
Wider in front is what I did on my RX-8 and was running my 1" staggered FC wheels, its great.
Really, just try it.
The RX-8 was stock suspension, so it had a little of that stock understeer but then also really bad understeer from being on the front bumpstops on turn in.
I learned to brake and but then get on the gas before I turned in to get the front off the bumpstops.
Had our clubs best driver race the 8 and he wasn't turning faster times than me until I told him about the gas pedal trick and boom he got top time of day that run with a 1 sec improvement.
On my FD I hated the understeer from my Tripoint front bar so I put in the stock rate tube in and it was much better with just that change.
Wider in front is what I did on my RX-8 and was running my 1" staggered FC wheels, its great.
Really, just try it.
The RX-8 was stock suspension, so it had a little of that stock understeer but then also really bad understeer from being on the front bumpstops on turn in.
I learned to brake and but then get on the gas before I turned in to get the front off the bumpstops.
Had our clubs best driver race the 8 and he wasn't turning faster times than me until I told him about the gas pedal trick and boom he got top time of day that run with a 1 sec improvement.
On my FD I hated the understeer from my Tripoint front bar so I put in the stock rate tube in and it was much better with just that change.
05-03-15, 04:47 PM
#11
What are you seeing in the pics Blue?
I can't tell anything from the pics. Also, road is wet so you wouldn't be able to accelerate hard enough to get max compression on the rear.
Tem,
Your rear spring rates are fine. You are running good shocks. Your alignment is OK.
There is no magic amount of travel. There is no magic ride height. Don't believe the hype.
How long are the rear springs?
What bump stops are you using?
Which sway bars are adjustable and what are the settings?
I can't tell anything from the pics. Also, road is wet so you wouldn't be able to accelerate hard enough to get max compression on the rear.
Tem,
Your rear spring rates are fine. You are running good shocks. Your alignment is OK.
There is no magic amount of travel. There is no magic ride height. Don't believe the hype.
How long are the rear springs?
What bump stops are you using?
Which sway bars are adjustable and what are the settings?
05-04-15, 08:26 AM
#12
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Look at the GAB R shock dyno's. The shock dyno doesn't look great. There is a ton of rebound and not much compression matching it. the shocks are "jacking you down" into the bumpstops. Plus they are progressive, basically the worst of the worst for handling high speed bumps. this thing must ride stiff as hell and bumpy as hell.
05-04-15, 12:04 PM
#14
lOOkatme
Look at the GAB R shock dyno's. The shock dyno doesn't look great. There is a ton of rebound and not much compression matching it. the shocks are "jacking you down" into the bumpstops. Plus they are progressive, basically the worst of the worst for handling high speed bumps. this thing must ride stiff as hell and bumpy as hell.
I had the GAB Super R on stock springs and they do behave exactly as you say.
But the Tem120 is running them on 3x stiffer springs than stock (11K F, 9K R), so a bunch of rebound damping is what he needs to control the springs.
Its probably better they have lower low speed rebound damping (progressive) to avoid jacking down with body roll/weight transfer.
Yes, I agree there is better suspension for high speed bumps- but as Tem120 knows, you pay for it.
Look at the GAB R shock dyno's. The shock dyno doesn't look great. There is a ton of rebound and not much compression matching it. the shocks are "jacking you down" into the bumpstops. Plus they are progressive, basically the worst of the worst for handling high speed bumps. this thing must ride stiff as hell and bumpy as hell.
I had the GAB Super R on stock springs and they do behave exactly as you say.
But the Tem120 is running them on 3x stiffer springs than stock (11K F, 9K R), so a bunch of rebound damping is what he needs to control the springs.
Its probably better they have lower low speed rebound damping (progressive) to avoid jacking down with body roll/weight transfer.
Yes, I agree there is better suspension for high speed bumps- but as Tem120 knows, you pay for it.
05-04-15, 01:29 PM
#15
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https://theprimitiveyou.com/everythi...-a-sweet-spot/
on a race car it really pays dividends to adjust everything on the suspension thats adjustable. you essentially need to learn where you are on the inverted U curve in the link for each thing. its tedious, but you learn two things.
the first is where the cars optimum setup is.
the second, is how changes effect the handling, each track is different, tires are different... keep notes, a whiteboard is great.
start with the easy stuff, try the shocks all the way soft and then all the way hard. if you have adjustable sway bars, try them all the way soft, and then all the way hard. try a high ride height, and then lower it until you hit bump stops, etc etc etc
on a race car it really pays dividends to adjust everything on the suspension thats adjustable. you essentially need to learn where you are on the inverted U curve in the link for each thing. its tedious, but you learn two things.
the first is where the cars optimum setup is.
the second, is how changes effect the handling, each track is different, tires are different... keep notes, a whiteboard is great.
start with the easy stuff, try the shocks all the way soft and then all the way hard. if you have adjustable sway bars, try them all the way soft, and then all the way hard. try a high ride height, and then lower it until you hit bump stops, etc etc etc
05-04-15, 03:29 PM
#16
hah , Yes like you stated the ride isnt that of a Cadillac . But its not that terrible either , depends on which setting the shocks are on . high it goes the much bumpier and stiffer the ride gets .
Also , Yes Better suspension would be great . and its actually very high on my list , But I want to fork out for a very good suspension setup when I do switch it .
Something along the lines of Zeal , ohlins , or similar setup . So I rather bide my time make due and adjust what I can with these . until I can afford something worth the money and effort .
Also , Yes Better suspension would be great . and its actually very high on my list , But I want to fork out for a very good suspension setup when I do switch it .
Something along the lines of Zeal , ohlins , or similar setup . So I rather bide my time make due and adjust what I can with these . until I can afford something worth the money and effort .
05-04-15, 06:46 PM
#17
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buy Ohlins. we've been road racing for 12 years and the Ohlins we were still like, "wow". if it helps we walked around the IMSA paddock this weekend, and Ohlins seemed to be the shock of choice there.
they have the low speed damping so that the car handles well, which is achievable, but the car also soaks up bumps without getting upset, AND it seems to ride well too. i guess ive never seen a shock that did all three of these.
they have the low speed damping so that the car handles well, which is achievable, but the car also soaks up bumps without getting upset, AND it seems to ride well too. i guess ive never seen a shock that did all three of these.
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