Sources for FWD race car setup - theory and practice
02-04-2008, 09:32 PM
#1
Burning Brakes
Thread Starter
Sources for FWD race car setup - theory and practice
Anyone know of a quality book or site that gets down in the weeds on FWD race car suspension setup?
I'm looking specifically for some help on the effects of swaybar settings and alignment (rear) for a class with spec, non-adjustable suspensions and more or less fixed spring rates and ride heights.
TIA
I'm looking specifically for some help on the effects of swaybar settings and alignment (rear) for a class with spec, non-adjustable suspensions and more or less fixed spring rates and ride heights.
TIA
02-04-2008, 09:56 PM
#2
hi!
try here: www.roadrace-autox.com
there are some very knowledgeable folks on that board; some real suspension gurus. most of them are SCCA IT racers, so most of them have adjustable everything....
i race two FWD cars; one, a Honda, has alot of potential adjustments; the other, my Probe GT, has practically no adjustments.
i can help you out a bit; my cars run pretty well and i do OK compared to the other fellas (i was NASA MA PTE champ for 2007 in the Probe)....
what kind of car are you campaigning? (is it the Spec Focus?)
todd
try here: www.roadrace-autox.com
there are some very knowledgeable folks on that board; some real suspension gurus. most of them are SCCA IT racers, so most of them have adjustable everything....
i race two FWD cars; one, a Honda, has alot of potential adjustments; the other, my Probe GT, has practically no adjustments.
i can help you out a bit; my cars run pretty well and i do OK compared to the other fellas (i was NASA MA PTE champ for 2007 in the Probe)....
what kind of car are you campaigning? (is it the Spec Focus?)
todd
02-04-2008, 11:11 PM
#3
Burning Brakes
Thread Starter
Thanks Todd - I have the silver Spec Focus that ran in the PT group at a couple of MA events last year - so I've seen you around. I'll do a little homework and shoot you a PM.
02-05-2008, 10:50 AM
#6
Burning Brakes
Since it's a "spec" class, you probably don't have a lot of tuning options. FWDers tend to be understeering little pigs, especially if they're on stock suspension.
Can you disconnnect swaybars ? Remember, if "adjustable swaybars" are allowed, "disconnected" is one setting in that range of adjustment. Get rid of that front swaybar and throw it as far away as possible...the next county, actually. If you have to have it actually connected, search for language in your rules-set that says something like "fasterners are free", which will allow you to use a rubber bungee as the fastener on one end of the bar.
Learn the "two-step turn-in". Ran a bajillion races in Showroom Stock classes and stuff like the old Rabbit Cup that required stock suspensions....the little mothers roll like a buoy in a hurricane, and you have to get the sucker leaning before you can effect any real load-transfer, so get used to adding a little steering input at initial turn-in, and once the suspension has taken a set, crank in more steering. This keeps your tires from getting surprised all at once.
Check the rear axle - are the spindles bolted to a cross-beam axle ? If so, you can fart around A LOT with alignment. Rear toe-out is actually a good thing on FWD race cars...play with bump-steer stuff to see what you get as the rear axle compresses...a little toe-out will get the mother turning....just DON'T LIFT once it's taken a set. You can shim the spindles where the bolt to the beam axle using thin shims or washers. Example: Sebring T1 is really kinda fun with 1/2" of toe-out in the RR wheel.
Learn to tune with tire pressures. Don't accept "common wisdom", because it's generally drivel cooked up by the mediocre. Blow the back tires up like bowling ***** to help relieve some of that understeer. We would normally run rear hot pressures in the 50-80lbs. range on race rubber...really. Get the back end sliding...and learn to like it that way...and you'll be F-A-S-T. Raises hell with rear tire wear...we would get about 1.5 tanks of gas out of a rear tire at Gingerman in a FWD Showroom Stock car before we were thru the rubber and "on the cloth".
Can you disconnnect swaybars ? Remember, if "adjustable swaybars" are allowed, "disconnected" is one setting in that range of adjustment. Get rid of that front swaybar and throw it as far away as possible...the next county, actually. If you have to have it actually connected, search for language in your rules-set that says something like "fasterners are free", which will allow you to use a rubber bungee as the fastener on one end of the bar.
Learn the "two-step turn-in". Ran a bajillion races in Showroom Stock classes and stuff like the old Rabbit Cup that required stock suspensions....the little mothers roll like a buoy in a hurricane, and you have to get the sucker leaning before you can effect any real load-transfer, so get used to adding a little steering input at initial turn-in, and once the suspension has taken a set, crank in more steering. This keeps your tires from getting surprised all at once.
Check the rear axle - are the spindles bolted to a cross-beam axle ? If so, you can fart around A LOT with alignment. Rear toe-out is actually a good thing on FWD race cars...play with bump-steer stuff to see what you get as the rear axle compresses...a little toe-out will get the mother turning....just DON'T LIFT once it's taken a set. You can shim the spindles where the bolt to the beam axle using thin shims or washers. Example: Sebring T1 is really kinda fun with 1/2" of toe-out in the RR wheel.
Learn to tune with tire pressures. Don't accept "common wisdom", because it's generally drivel cooked up by the mediocre. Blow the back tires up like bowling ***** to help relieve some of that understeer. We would normally run rear hot pressures in the 50-80lbs. range on race rubber...really. Get the back end sliding...and learn to like it that way...and you'll be F-A-S-T. Raises hell with rear tire wear...we would get about 1.5 tanks of gas out of a rear tire at Gingerman in a FWD Showroom Stock car before we were thru the rubber and "on the cloth".
Last edited by Professor Helmüt Tester; 02-05-2008 at 11:13 AM.
02-05-2008, 12:29 PM
#7
hi again.
i pretty much agree with Helmut; remove the front swaybar. run as large a rear bar as the rules allow. put in quite a bit of neg camber up front (i run -3.5 degrees on the probe). i run -.5 in the rear. i run 1/16 to 1/8 toe out up front, and zero toe in rear (this is mostly due to the fact that i run lots of 'high speed' tracks; and less toe means more top end. also, i am an el-cheapo, and excessive toe out really wears out the tires fast).
as for tires, i tend to just replace the fronts frequently (keeping them fresh and 'good'). i keep the older, 'bad' tires on the rear, to help the car steer itself around corners.
as for driving style, i agree with helmut, too. you want the car to WANT to rotate; once you have initiated the turn, you will need to be feeding in throttle; even a slight lift will make the car really react and rotate swiftly -- as long as you are prepared and ready for this behavior, you are good to go!
todd
PS the outside edges of my rear tires tend to wear pretty quickly, in a 'feathery' pattern; thats from the rear sweeping across the pavement. my fronts wear pretty evenly, unless i get anxious with the throttle; then the inside 3" wears down first (due to tire spin; i don't have an LSD).
i pretty much agree with Helmut; remove the front swaybar. run as large a rear bar as the rules allow. put in quite a bit of neg camber up front (i run -3.5 degrees on the probe). i run -.5 in the rear. i run 1/16 to 1/8 toe out up front, and zero toe in rear (this is mostly due to the fact that i run lots of 'high speed' tracks; and less toe means more top end. also, i am an el-cheapo, and excessive toe out really wears out the tires fast).
as for tires, i tend to just replace the fronts frequently (keeping them fresh and 'good'). i keep the older, 'bad' tires on the rear, to help the car steer itself around corners.
as for driving style, i agree with helmut, too. you want the car to WANT to rotate; once you have initiated the turn, you will need to be feeding in throttle; even a slight lift will make the car really react and rotate swiftly -- as long as you are prepared and ready for this behavior, you are good to go!
todd
PS the outside edges of my rear tires tend to wear pretty quickly, in a 'feathery' pattern; thats from the rear sweeping across the pavement. my fronts wear pretty evenly, unless i get anxious with the throttle; then the inside 3" wears down first (due to tire spin; i don't have an LSD).
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02-06-2008, 02:43 AM
#8
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I ran a FWD track car (turbocharged '97 Integra) for several years... not only did I keep the front sway bar, but I upgraded it. Some people remove it to help the car rotate, but I found that the extra stiffness is more valuable than the extra ease of rotation. You just have to know how to drive effectively with understeer, and modulate the throttle on corner exit. It was really just power understeer anyway, because the car was well balanced, and nothing about FWD dictates that you have to have general understeer everywhere. There are better ways to get the car to rotate than to throw away the performance of your front suspension, IMO... the feel of the car does not necessarily indicate overall performance.
I also upgraded the rear sway bar, ran stiffer springs in rear than in front, extra negative camber in the front, an LSD, and used an Ingall's engine torque damper to help keep drivetrain movement from messing the suspension up. It worked out really well... even though the car was turbocharged, it could hook up decently on corner exit. The big bore RWD cars still beat me there, since FWD is still FWD, but I was able to catch them in other places. This was back in my Time Trials days, and to even my own surprise, it was always one of the faster cars at each event, beating most of the Corvettes, and only about a second off of the fastest Z06 (stock). FWD can definitely do a lot more than it gets credit for, but obviously I had enough reasons to give it up and choose to race a 944-Spec instead.
I also upgraded the rear sway bar, ran stiffer springs in rear than in front, extra negative camber in the front, an LSD, and used an Ingall's engine torque damper to help keep drivetrain movement from messing the suspension up. It worked out really well... even though the car was turbocharged, it could hook up decently on corner exit. The big bore RWD cars still beat me there, since FWD is still FWD, but I was able to catch them in other places. This was back in my Time Trials days, and to even my own surprise, it was always one of the faster cars at each event, beating most of the Corvettes, and only about a second off of the fastest Z06 (stock). FWD can definitely do a lot more than it gets credit for, but obviously I had enough reasons to give it up and choose to race a 944-Spec instead.
