ls2 bait

iTrader: (11)

whats the friggin difference? just got my bmr cross member and have no idea what to look for as far as instant center. i know pinion angle should be in the -2 -3 range.

chrismorales75

Pinion angle is how far down the pinion (rear end) is pointing.

Instant center is where the lower control arm and torque arm would intersect if you were to plot out the path of each bar.

A good thing to do would be to have the car scaled, so you know where the car is 50/50 at and plot out the intersection points for the adjustable chassis part, i.e. torque arm and lower control arms.

wolfy

iTrader: (1)

is that optimum? i mean having the instant center at the 50/50 point? i understand the difference between pinion angle and instant center, but not sure how to tune both together for best results. and at what point do you set instant center more forward or aft of that 50/50 mark?

ps - sorry for the hijack...

NSTY WS6

iTrader: (5)

The instant center is not at the same point as the center of gravity. It could be in certain cars but not likely I dont think. Like has been already stated, the instant center is where your lines plotted along your torque arm(upper control arm) and lower control arms intersect. If your instant center in relation to your center of gravity is too high, there will be too much energy wasted pushing the car skyward, instead of forward. If the IC is too low in comparison to the CG the tires wont have enough force on them to keep them planted. Theres a fine line in there where it will work correctly and most importantly efficiently. Its easy to get a car to hook, be it pull the wheels, wheelstand, or squat. Its another to get it to launch efficiently, which doesnt include any of those, or atleast minimal amounts. You have to find your center of gravity to really be able to do any plotting, as it all circles around the CG. Instant center plays a big roll in the initial launch. When changing your instant center, front adjustment of your torque arm, bmr's stock replacement type has different holes to use, as does the Madman torque arm. Also, if your relocation brackets have another hole. You NEED to re-adjust your pinion angle to whatever you run be it 0 or -3 after you adjust the instant center.

ls2 bait

iTrader: (11)

holy mother of god this **** is a bit complicated. looking like i wont be adjusting this anytime soon.

Bitemark46

And to think that people call us drag racers a bunch of dumb rednecks. There is a science to this. I was just as confused as you when I started learing about suspension geometry (still learning). This link helped me out a lot in understanding. It may do the same for you. -Mark

http://www.baselinesuspensions.com/i...A_Drag_Car.htm

siverbullet

iTrader: (2)

wow that is some great info!

James Montigny

iTrader: (13)

chrismorales75

Knowing where the 50/50 point and intersection possibilities gives you information on which way to go based upon how the chassis is reacting.

Having the IC close to the 50/50 point would be better than and instant center that is only 24", but finding the optimum point when you have 2 lower holes on relocation brackets and a couple holes on a torque arm isn't hard.

Run the car, try another hole, set the pinion angle run it and see if it is slowing down or speeding up the car.

There is no guess one time where it should be and leave it alone, if you don't want to tune your chassis to work right, don't buy adjustable parts.

If you won't take time to try different settings adjustable parts are not going to help much.