I'm close to wrapping up the install of my new Moser 12 bolt, and I noticed during this process that the ears are higher than on a stock 12 bolt.

I know this does something positive, but I'm not sure what and why - figured this would be the right forum for the answer.

In the meantime, maybe I should do a search.... ;)

The lower mounts are slightly lower too,or they were on the Moser I installed last summer. I removed the lower SSM mounts from my old 12 bolt housing and never re-installed them on the Moser housing for that very reason. It moves the instant center back allowing the suspension to hit and hopefully plant the tires harder. After going back to the radial slicks, and getting 1.415-1.431 60ft times last weekend, the design must work. Only varied .016 over 11 passes and 2 days of racing.

Interesting, that's a better description but similar to what my search yielded. I won't pretend to know HOW it works, only THAT it works. Thanks for the quick post.

What were your 60ft times before?

Does this have any negative impact on "normal" driving, or alter the stance of the car?

It doesnt alter the stance of the car at all or normal driving. Last year my 60fts were 1.50-1.60, I had all kinds of transmission troubles, replaced old 12 bolt that had a posi in it, ended up the year with 1.50-1.53 on MT drag radials. I then swapped to the ATI 8" converter and HR antiroll bar this winter, which made a big difference after I got it hooking again.

The revised geometry will plant the rear wheels better on acceleration. It does this by using the control arms (trailing arms?) to lever the back of the vehicle body UP when torque is applied. Every action having an equal but opposite reaction, the axle is pushed down for better traction during the application of torque.

You can see similar action on most shaft-drive motorcycles, especially the older Yamaha XS1100s. Whack the throttle open, and you will about put the passenger in orbit.

The down side--for both the bike and the Chevelle--is that it does the exact opposite when you pull out of the throttle and hit the brakes. The axle tries to lift (body sinks in the rear.) By lifting the axle, ultimate braking power back there is reduced.

If you draw a line at the same angle as both the upper and lower trailing arms the point where they intersect is the instant center point. As the upper attaching point is raised or the lower is dropped, as stated earlier, that point moves farther back on the car which adds downward force to the axle and tires. As the instant center is moved to the rear at some point the car's body and the upper part of the tire will seperate when the power is applied instead of the body squating on the tires and this improves traction. Several people make add on bars that do the same thing in principal. The old Mopar Super Stock springs always did this which is why they left so hard. Adjustable upper control arms are usually required in order to adjust the pinion angle when these points are changed in relation to each other.

As was already said, the raised and the lowered connections change the Instant Center or "IC". The results in a separation of the chassis at launch.

Since for every action there is an opposite and equal reaction, as the chassis is raised, the tires are pushed to the ground.

Watch this video I made a number of years ago showing first a stock suspension launch and then a suspension with a relocated IC similar to what you will see using a Moser 12-Bolt like the one you have or No-Hop Bars or SSM's.

http://www.boomspeed.com/mc71454/no_hop.wmv

My car was running mid to high 11's at the time this was made..

There is a theoretical difference in handling due to more of the vehicles mass going forward when braking. One of the reasons the IC's were located where they are in a stock location was to have more control when braking and to minimize the front end from dipping down when making a panic stop.

Notice the "Force Lines" under the front bumper stock and then on the hood with the relocated IC>

http://www.boomspeed.com/mc71454/InstantCenter_crop.jpg

Excellent information!

Tom, that video was a good idea - really shows the principle in action.

Thanks all for the input-