914Racer

I will claim, that unlike the fellow in the rear stiffness thread, I don't think you have to have a FWD car at a true 50/50 weight distribution.

In fact in most cases you will do more harm than good. If you are making reasonable HP for a race motor (not talking IT/H4 power), you will actually hurt your lap times by getting it to 50/50. I'll explain more after I have a few people tell me that I am crazy.

ddd4114

Should we assume all four tires are the same (size and type)?

descartesfool

See here:

https://honda-tech.com/forums/road-racing-autocross-time-attack-19/fwd-laptime-vs%25-front-weight-lapsim-values-842233/

and here are the charts missing from the original post back from 2006

rice_classic

But that thread was 8 years ago! Way to go ahead and rain the parade Descartes.



914Racer: I'll bite. You're crazy! Now, tell me why you refute this.

descartesfool

What's old is new!

But just try to move weight rearward. Still a major challenge on a FWD. Anyone know what current front % weights are on pro race cars. For a long while it was 58% minimum for WC FWD cars.

914Racer

Meh, experience says you have to keep weight over the front wheels to keep the traction. However there are a few different ways to set the car up and it is driver and track dependent. On an autox course the car may be faster with a 60/40 split. Having more weight over the drive wheels will help the car turn in faster and you will have traction out of the tight turns. However on a track car, you may have more success with running down towards the 55/45 region. That would have to be tested to see if you are losing traction out of the corners vs. handling and tire durability.

It will also depend on your rule set. Some classes like GT3/GTL allow all kinds of things, so I would be moving the driver almost to the middle of the car, maybe flipping the engine around backwards, etc, where IT won't allow you to move the battery. I know of one CRX racer who has run as low as 50/50 and he said it hurt his corner exit speed. He went back up to 55/45. He had no complaints over handling. Just traction on corner exit. It will also depend on power. If you run an ITC car you won't have the power to spin the tires anyways, so you may actually be able to gain an advantage if you run less weight on the front, but in the case of my GT3 car, it will have a lot of power and very little weight. So it will benefit from a little higher front weight.

I would agree that having your cross weights equal is a good goal to shoot for, but the reality is, most production cars will never make it. The production layout of our tin tops makes it hard to get the weight balanced side to side. However if you can move the driver over, convert to a K motor, etc, you could really change it up. But this would also be track dependent. If you have a track with predominantly left turns or right turns you might actually use a little offset on your weights. Like at TGPR, I will run with the left side front a little heavier than the right front to help the car work better on that track. However at a place like RD Atlanta, it would be better to go the other way.

Descarte, that is a good thread.

914Racer

Ask Billy. Lol

I would expect it to be pretty close to 58% front. WC isn't allowed the latitude to move the driver around much, nor are they allow a lot of the things the more open classes allow. However look at the old BTCC cars, they were moving the driver almost to the middle of the car and the engines were flipped around the gearbox and set behind the axle centerline.

ZUL8R

hmmm....

known

iTrader: (1)

I have been thinking about this a lot recently since I have to add weight for some changes in my class.

A little more weight in the rear at certain tracks or in general I think it might be a benefit to me, I'm locking the rears a tad and the rear end is very loose under braking. I know this is a common problem but one I would like to combat a little bit.

Im allowed some aero in the rear but Im not excited about the extra drag a full size wing would add. Im adding a decent but small within the rule set front splitter so with an addition of weight to the rear, I might not lose to much grip in the front.

What do you guys think? I think I'm still on topic here, not trying to deviate from the discussion.

914Racer

I have been thinking about it for my GT car. Having the ability to quickly adjust the weight distribution would be useful depending on the track. Maybe some active ballast could be even more useful. I think ballast mounted on a sliding track could be helpful.

JW racing

With the powa I have at the moment I need 80%f/20%r lol! Because I can not get on-power exit grip even if I paid my tires under the table to do so. I think though even the best setup cars still must roll on the gas when you get to a certain power point. So when you are at that point I think it's more about setting up overall neutral balance through the corner and use the ability to play with the throttle for balance, since it is the most powerful tool as far as balance goes.


Proper aero does wonders if you have front and rear balanced correctly, I have a wing many say has "too much drag" and is "too big" (GT200) however I found I have very little drag at top speed and a whole lot of down force. It just compliments my splitter and airdam perfectly. Just experiment what works for you best because every person will have a different suggestion.

914Racer

Try dropping the angle of your wing and see if you pick up some front bite.

When you get on the power does the car try to wash out?

JW racing

The wing helped overall with freeing the car up but I don't think it's that, the front does wash out only on the gas. I went back to the Helical LSD from the Plate LSD which helped a lot to mitigate the push, but still fighting a bit to get grip forcing me to roll on the throttle untill the car is pointed straight. The springs, toe and sway bars are so close to dialed I don't want to mess with any of them(softer front will hurt and stiffer rear will be too stiff since it's at 1100 and 32mm bar already). I was thinking of moving some of my ballast forward and playing with front track width.

My issue fits well in this weight distribution topic.

914Racer

What is your current weight split? Post numbers from last corner weighting season.

I assume you are making somewhere in the neighborhood of 275 flywheel? Were you using a KAAZ? I would look at the OS Giken. It is probably the best (and most expensive) diff on the market. If you could get a hold of one of the Xtrac Viscous plates you would be money, but I doubt there is one available for less than a small fortune.

Another thing to look at. Change the cam on the throttle body. Slow the rate of opening at low throttle angles. This may help smooth the drivability coming out of the turns. Does this only seem to happen at very low speed turns, like first or second gear turns?

Might also look at shock valving. A change there could cure this problem since it only occurs in a transitional phase. This is an area where the shocks work. You are looking to control front end lift as you roll on the gas. Another thought might be to try out some anti-lift on the front suspension. This could also help keep the front grip higher. A wider track will really help with the lateral weight transfer, not so sure how much it could help with the situation you are dealing with.

JW racing

Corner weights are 727lf 723rf 460rr 460lr with me and half a tank in it. It seems to get more traction in front as the tank gets 1/4 and less but I risk dangerous sputter from the pump and sloshing at that point, so I run 3/4 tank or so most sessions.

Yes you are right about the power. It happens in 2nd and 3rd gear turns, with average radius and sometimes few are hairpins. I use the oem helical, I dont like plate units really because of several reasons. Maybe I haven't tried the agreed best (OS Giken) yet, but I am a cheap racer indeed...

914Racer

61/39. Sounds like its an issue other than weight distribution. The helical locks up to hard. Wonder if that might be causing some issues. How much toe out are you running in the front? Have you ever tied running without the front bar and a little more front spring. I also have to wonder if maybe your sway bar is causing a wheel to unload slightly thus causing the loss in traction. I also wonder if maybe a driving style issue might be causing the wheel spin, wish we were on the same coast so I could go to the track with you and study the problem. Do you use curbs heavily?

lwnslw

I have just a hair stiffer springs than Justin on the front and no swaybar and in low corners I'm picking up the inside front tire under gas, so I can't get enough traction out of the corner or get on the gas early.
Have the pics to prove.

JW racing

Marcel - try those 20k rears it will keep the inside front down and give more on throttle steering too.


I run 1/16th toe out in front, When I run no front bar, it picks up the rear wheel too much, it is unstable at high speed and falls over on it's face, and I dont want to run much stiffer than 900 fronts because my shocks are not the best. Curbs-Unless it's for shaving time in a certain corner, I just barely touch them and won't jump them. We jump one curb and that's bus stop at Buttonwillow and that's not where I loose traction. I try not to abuse curbs heavily as it upsets the car too much. *It isn't a peg leg effect from the helical and touching curbs or sand, I know what that feels and sounds like. That seems to be Marcels car's issue I feel. Mine is more like a dual wheel burnout and front push that is power induced.

I think it is in the rear because that is where the weight transfer is at the time of the issue and making a change to front suspension impacts entry or off power more than on power I feel. So maybe more rear toe out and trailbraking less and get used to the decrease in stability in the braking and entry zones. That should be close.

914Racer

Talk to Progress about changing the valving of the rear shocks. I bet you could gain some benefit there. Use the shock to control the transient body movements. That should help control the "lift" on the front wheels.

vtecjj

Justin-I'd try taking out rebound up front first....and go back to the kaaz (assuming it's not broken)

vbspec

hmmmm kinda funny i was corner weighing my car yesterday. we got it to a 51% cross but the f/r was like 67%f.... Im 75 lbs over weight and have nothing really to take out of the car. corners were 744rf/733rf/525rr/475lr
disconnected swaybars and played with preloading springs and could not make much of a difference. the car has been repaired from an accident when it was a street car and thats most likely where the weight on the right side is coming from
any thoughts???

edit springs are 800f/950r on double adg koni's

stuntman

You couldnt adjust your cross much when playing with spring perch heights?

As far as weight distribution goes, can you put a lighter hood on or move the battery?

JW racing

The hydraulic shocks were a limitation and I sold them, I have progress parts like sphericals still though. I actually use TEIN Flex gas shocks now, and they have some adjustability. I will try taking some rebound out of the front. One day I will be able to afford some Koni 2812s and a proper 1-way LSD but not soon.. they both are way out of my budget at the moment.

The kaaz wore out Meris, and it pushed like crazy. The Helical improved my entry and mid corner rotation immensely.

vbspec

I got it to the 51% and ran out of time.
The car has a CF hood and an Odessy Batt mounted behind he rr
Im guessing dropping the rear spring weight might make a difference as well.

Robin6

what a great read...thank you everyone!