I know this topic has been beat to death and if you want to learn about the Rear Biased Setup you just have to search, but I was involved in a thread over on the NASA forums and a guy posted this website which contains some great general and specific info regarding setting up a FWD car for racing and many other topics as well.

http://farnorthracing.com/autocross_secrets10.html

EDIT: Don't take this as the BIBLE people. Just learn what you can and apply where needed.

Mainly this guy has tested and proved the rear biased setup through not only mathematics but through trial and error as well.. .

Table of contents for this site
*Acknowledgements
*Caveat Lector!
*Driver Effectiveness
*Tires
*Suspension
*Shocks Updated 08 Jan 2007
*Balancing the Car
*Launch Control
*ABS
*On FWD - Talks about the Rear Biased Setup
*Corner Weight Calculator New 04 Jan 2007
*Tire Pressures New 04 Jan 2007
*Tire Temperatures New 04 Jan 2007
*Must-Read Books


Modified by 6spdKEG at 7:51 PM 3/7/2007


Modified by 6spdKEG at 4:22 PM 3/8/2007


Modified by 6spdKEG at 7:26 PM 3/8/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 6spdKEG &raquo;</TD></TR><TR><TD CLASS="quote">I know this topic has been beat to death and if you want to learn about the Rear Biased Setup you just have to search, but I was involved in a thread over on the NASA forums and a guy posted this website which contains some great general and specific info regarding setting up a FWD car for racing and many other topics as well.</TD></TR></TABLE>

I was that guy. And yeah, it's a great resource all around...guy knows his stuff. My original thread was over at SCCAForums.com... http://sccaforums.com/forums/1...25010

 

cool, I'm berny2435 on NASA forums. I'm not sure why I signed up for a different name than my H-T name.. .

Thanks again for that link

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Done correctly, you get a car that rotates on lift throttle, but plants the rear firmly once throttle is applied. </TD></TR></TABLE>
This is what I've been trying to tune into my car.

 

The 8 steps of reasoning to FWD rear stiff setup.

(1) The front tires do everything in a FWD car, power the car & turn the car.

(2) Because of (1) you want to maximize the front grip in a FWD car at all costs.

(3) two tires at equal weight will provide more grip than two tires at unequal weight even if the total weight remains the same.

(4) From (2) and (3) you can see that we want the front 2 tires to stay as close to equal weight as possible.

(5) from (4) we can see that we want the rear end of the car to take up as much of the total lateral load as possible, because this will leave the front two tires closer to equal weight = more front grip.

(6) Making the rear end of a car stiffer than the front will make the outside rear tire increase in load faster than the front outside during a turn. (until the max Lateral Load transfer for either end of the car is reached.)

(7) The max Lateral Load transfer of each end of a car (front, rear) is approx. equal to the weight of that end of the car divided by 2. (ie the rear of your car is 1000lbs total, (500lbs right rear, 500lbs left rear) then the max load that can be transferred left rear to right rear is 500lbs. At this point the inside rear will start to lift and any additional load transfer will come 100% from the front inside tire.

(8) From the above you can see that any set up that does not totally unload the inside rear is giving up front grip, and this is NOT good in a FWD car.


Picking the front spring rates:
It makes sense to find a good stiff spring that will be plenty stiff enough for quick responses to driver inputs and an overall stiff race like feel. The stiff suspension will also reduce body lean and resulting chamber changes from too much body roll. However too stiff and the car will start to skip and lose grip from small bumps and irregularities in the road. It turns out that most successful FWD road race cars tend to find this balance with a front spring that results in a natural frequency of abut <U>120 Cycles Per Minute</U>. This will give you a good starting point. If the front tires are skipping or chattering allot then you need softer front springs. If the car feels sluggish, and slow to respond to steering input then you should try stiffer springs.

Picking Rear spring rates:
Now that you have a good starting point for the front springs, you can pick a slightly stiffer rear spring to make sure you get that total lateral load transfer in the rear. Remember we do not want maximum grip in the rear, we want maximum grip on the front 2 tires AT ALL COSTS. The rest is driver preference, do you want the rear to lift real early in the turn (most fwd racers do) or do you want to only have rear tire lift mid turn. Either way you still want the inside rear to be totally unloaded at, or even before you hit the max G in a turn. If your rear tire is not totally unloaded in a hard turn then you need stiffer springs, or sway bar in the rear, because you are giving up front grip. Front grip means everything in a FWD car.

NOTE:
Some FWD cars are so front heavy that even with the inside rear tire lifting and staying off the ground during the entire turn it still pushes like a pig. In this case you can run smaller tires in the rear, older bald tires, or play with alignment and tire pressures to get some off throttle rotation.

(snow days are fun ).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 577HondaPrelude &raquo;</TD></TR><TR><TD CLASS="quote">

Picking Rear spring rates:
N The rest is driver preference, do you want the rear to lift real early in the turn (most fwd racers do) or do you want to only have rear tire lift mid turn. Either way you still want the inside rear to be totally unloaded at, or even before you hit the max G in a turn. If your rear tire is not totally unloaded in a hard turn then you need stiffer springs, or sway bar in the rear, because you are giving up front grip. Front grip means everything in a FWD car.


</TD></TR></TABLE>

I will disagree with him on that point. You look at the RTR tsx's and the Tri-point mazda's and those cars are FLAT and not lifting the inside rear tire.

 

To put some Honda perspective in to the talk of wheel frequencies, to achieve a wheel frequency of 2.0Hz in the front you need about a 750lb/in spring. An increment of 50lb/in is about 0.1Hz.

In the rear, a 2.5Hz wheel frequency needs a 700lb/in spring. There's your starting point.

Those values are assuming a 2300lb Civic EG. Other Hondas of that generation may be similar.


Edit: forgot to square the MR


Modified by bsclywilly at 5:08 PM 3/7/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slammed_93_hatch &raquo;</TD></TR><TR><TD CLASS="quote">

I will disagree with him on that point. You look at the RTR tsx's and the Tri-point mazda's and those cars are FLAT and not lifting the inside rear tire.</TD></TR></TABLE>

I think that what is happening with those cars is that the overall roll stiffness is so high that they are lifting, but only a little bit. If you look very closely at still shots of those cars cornering, you'll see that the inside rear is actually lifting, but it's only around half an inch to an inch, not the 4+ inches that you'll see on a lot of club racing cars.

 

So talking roll stiffness, these RTR tsx's and Mazdas, what are they using too keep the rear more planted??

Stiffer front rates?
Huge front roll bar?
More evenly ballanced car front to rear weight ratio?
Better chasis/cage design?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 6spdKEG &raquo;</TD></TR><TR><TD CLASS="quote">So talking roll stiffness, these RTR tsx's and Mazdas, what are they using too keep the rear more planted??

Stiffer front rates?
Huge front roll bar?
More evenly ballanced car front to rear weight ratio?
Better chasis/cage design?

</TD></TR></TABLE>

E. All of the above!

And, here's a good picture... Even though the tire's not far off the ground, it's still transferring all the rr weight to the other tires. You don't want the tire so far off the ground that you overpower the outside front. I guarantee you that they do weight transfer studies to optimize roll stiffness and spring rates to match the tires' capabilities.

 

I never knew lifting the rear wheel was a good sign.
I wish I knew if mine lifts or not.

 

It looks like #144 up theres seems to decamber to 0 deg. Probably not an intensional setup there.. .

For a relative noob at HPDE, is Neg 2 deg camber in the rear enough to start with on entry level R comps like Toyo Ra 1s, Hankook Z211, Nitto Nt01R?

I have new Mugen RTAs, new Mfactory Toe links and camber kit, New LCA hard rubber bushings, 850 springs with GSR roll bar.. .

 

but this guys site is all about <U>AUTOCROSS</U>

an autocross setup may not be optimal for Road courses. especially a fwd car that is tail happy , setup for extremely tight autox courses.
alot of autox guys, especially front wheel drive cars, want a very twitchy setup. getting sideways in a turn at 45mph is alot different then at 110mph. also how many people drive on the roadcourse the way they do during a 50 second autox course. your tires would not be liking you very much after 20 minutes on the road course driving that way.

also the RTR tsx's and the Tri-point mazda's , how much suspension travel do they have? and what are their spring rates. on a car with more travel and softer spring rates you'll notice a more drastic amount of distance from the rear wheel to the ground when they lift up in turns. when you're running 1000lb springs it's alot harder to compress that then 400lb springs, say with a 22mm sway bar.

i'm not an expert in road racing. i have not driven my car on a road course. though i have ran on the track on a motorsickle.


and Not sure how you can say someone is a lowsy driver, seems like this guy has won a few things. even if it was in CANADA

2004 ASN/FIA Canadian D Modified Champions
2002 SCCA ProSolo Honda Street Challenge Series Champions
2002 SCCA ProSolo Street Modified Series Champions
2003, 2001, 2000 CENDIV Divisional Champions


Quite a few of my friends say who they believe are good autox drivers and who aren't. they love to talk all kinds of ****. Alot of the times the ones they say aren't good drivers are the ones that are beating them.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 6spdKEG &raquo;</TD></TR><TR><TD CLASS="quote">For a relative noob at HPDE, is Neg 2 deg camber in the rear enough to start with on entry level R comps like Toyo Ra 1s, Hankook Z211, Nitto Nt01R?

I have new Mugen RTAs, new Mfactory Toe links and camber kit, New LCA hard rubber bushings, 850 springs with GSR roll bar.. .</TD></TR></TABLE>

I run 2.5 degrees front and 2.0 degrees rear for autocross. Seems to work ok, but as you know from my other thread, my springs were all screwed up.

I just took a look at those Mfactory parts. I have a set of their drain plugs, but didn't know they made such nice other stuff. I'm going to have to pick up a set of those toe links and camber adjusters.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybridmoments &raquo;</TD></TR><TR><TD CLASS="quote">but this guys site is all about <U>AUTOCROSS</U></TD></TR></TABLE>
Handling-wise, the methods and ways of thinking apply to either type of racing; the point of both is to maximize the grip of the tires. Doing that takes a little bit different approach with a FWD car, but, autocross or road racing, you want the front tires to be working at 100%. Based solely on the frequency numbers he gives us, it seems like the setup recommended most by the Honda Challenge guys is close, but not exact. Like with anything, it's just a starting point. The HC guys have actually given me a setup that seems to be MORE tail happy that what his numbers suggest should be the case.

Edit: I didn't see the OP's edit.
While I can't say either way, since I've never seen him drive, it seems as though his credentials back him up. Whether or not he's a good driver doesn't really have a bearing on his setup knowledge. If the best setup guys were drivers, they'd never need crew chiefs and engineers, and likewise, if the engineers were the best drivers, they'd be driving. I know a bunch of people who are good at one or the other but not necessarily both...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spdracer22 &raquo;</TD></TR><TR><TD CLASS="quote">

Edit: I didn't see the OP's edit.
While I can't say either way, since I've never seen him drive, it seems as though his credentials back him up. Whether or not he's a good driver doesn't really have a bearing on his setup knowledge. If the best setup guys were drivers, they'd never need crew chiefs and engineers, and likewise, if the engineers were the best drivers, they'd be driving. I know a bunch of people who are good at one or the other but not necessarily both...</TD></TR></TABLE>

I changed what I said to be a lil less harsh. I guess I'm sorta a dick at times but what I said was way better than what my reliable resourse had to say about him.. .

Just an FYI I'm not trying to smash this guy's credentials for setup and tech expertise, I'm really commending him b/c I really like his site and that is why I posted it. I'm just letting people know that they shouldn't think that this guy is a "Bob Bondurant, Micheal Shumacher" racing figure we are talking about here. He's a guy that loves what he does, has done some real nice work and was kinda enough to share it with the public. Enjoy! I keep an open mind and learn from as many people and resources as I can, not just a select few.. .