Rear shock movement

[Ron Gusack]

I took video of the rear shock movement when leaving the line, but I don't know what it should look like. My logger says it didn't spin and I guess I could have tightened the compression. Can you tell me how this looks? There's both slo-mo and regular speed and also from the outside of the car. Thanks for any help.

[Bob Mulry]

OK Ron,

I guess that I have to give up one of my old guy tricks...........

Measure the roll out on your rear tires, with the car staged take a look at the name on the side of the tire or a paint stripe on the side wall......

If it's a 94" roll out, that tire should turn exactly 94" and move the car forward 94"........

With your eyes you should be able to read the name on the sidewall for 1 complete tire revolution..

If you use a camera during testing put a chalk mark on the tire and ground at the spot they touch the track, measure 94" forward and put a chalk mark on the track. This way you see if it is hooked up 100%

I know about loaded radius, but the tire tread still has to rotate 1 revolution....

Hope this helps sort it out,
Bob

[ironside68]

I'd start with tightening the extension on the shock. It's extending way too fast and bouncing right back up "into the car". What type of rear and front shocks do you have, both DA?

[Ron Gusack]

Both are DA. Rears are Strange, fronts are Menscer/Afco. Rear extension was set 3 from full loose and compression 3 from full tight. That was from a previous day on a track I couldn't get consistent 60's.

[ironside68]

I would tighten them to full stiff on ext, and 3-4 from full soft on compression and start there. Fwiw I've had Strange DA's on my car and had stiffer valving put in about the 3 or 4th time I ran them because I was always at full stiff on ext and still extended too fast.

The front looks to move decent and transfer, if it's a good hooking track I'd start with the rear changes first and compare videos.

[Ron Gusack]

Thanks, I'll give it a try. Should the rear plant, stay down and then gradually come up as it gets close to the gear change? I've been told to make the adjustment as tight as possible until it spins and then soften a little. The guys at Merscer told me that they don't like Strange shocks but didn't want to bad mouth them, so no real detail. My logger showed no spin on the run in the video, but my RT's were late on every run. Mostly .040's with one 020, and that was deep staging. I kept tightening the front.

[Tony Curcio]

I watched your video a few times, and thought it might be squatting, but wasn't sure until you entered this last question.
The car will respond to shock adjustments better if you eliminate the squat. The instant center is too low when the body pulls down over the wheels at the hit. It looks like you have ladder bars, though I couldn't actually see them. If so, all you have to do is raise the front mounting point.
When the body starts to separate from the wheels/axle, use the shock settings from Mr. Ironside. Full stiff on extension will usually get you down the track in all kinds of weather, as long as the rear is separating.

[Ron Gusack]

It is a ladder bar car with the front mounted in the lower hole. I think I have to beat the floor board up a little to gain enough room to move to the top hole.

[ironside68]

If you move to the upper hole you're going to hit the tire harder as well, but the only way to know how it's going to respond is to test it.

I ran Strange for many years and upgraded to Penske 2years ago. I didn't pick up et but the car was more consistent, and I felt the front was really the most valuable.

Strange may not be the greatest but they're better than Comp Eng shocks, better than a SA, but yes they are about 1/2 price of Penske, Santhuff and JRI. Speak with that Menscer guy or many of the other shock guys and getting yours "made/tuned" to your car I bet you see a good response without spending twice the money.

[Ron Gusack]

I'm a bracket/index racer, so ET isn't my main concern. As bad as that rear movement looks, the DS rpm looks like the tire is dead hooking. I looked at the Santhuff stuff, but 2 G's was a little extreme for me. The other thing that's bad is that I tow the car with the straps hooked to the ladder bar brackets on the rear, so I may have worn the shocks out just towing back and forth to the track.

Going to the upper hole would be a chore for me. I'd have to figure out how to move the Heims to keep the DS angle right and keep the same pre-load. These bars have no external adjustments cause they're way old.