Shock Tech Q&A

[LLOYD-XMAS]

I have a question what is to tall when talking about bump-stops on the rf of a dirt late model? What is considered to tall for the christmas tree style? Also what happens if the bump-stop is a touch to tall? Thanks

[PenskeShocks]

There isn't really a measurement that is too tall. All depends on the track and how much your RF is traveling and when you want to get into the bump stop and how much. In general, if you get into a bump stop too soon, especially in the RF, it will tend to tighten the car up. Bump stops are very tricky, if your running a bump stop set-up you have to be sure you run enough rebound to control the force produced by the bump stop.

[fastford]

I have a question what is to tall when talking about bump-stops on the rf of a dirt late model? What is considered to tall for the christmas tree style? Also what happens if the bump-stop is a touch to tall? Thanks

when i first started with the bump stops, mine were to tall, i cut them down a little at a time to get the amount of dive i wanted, then if during hot laps it was diving to much, i would shim it back up, i got all my stuff from re suspension, one thing to remember, if you cut it , it will get stiffer, but with the christmas tree type , it dont effect it much , also the more dive on rt ft, the more rear steer and the freer the car will be

[LLOYD-XMAS]

Thanks for the replies.

[xray]

The question everyone wants to know but afraid to ask, How much RF rebound @1ips for a stack combo? For a conventional 400?

How much rebound do you take out throughout the night as it slicks off?

[MasterSbilt_Racer]

The question everyone wants to know but afraid to ask, How much RF rebound @1ips for a stack combo? For a conventional 400?

How much rebound do you take out throughout the night as it slicks off?

That is where the crew chief earns his money. There is no one right answer. Your stopwatch, eyes, and the driver determine that for the given track.

[PenskeShocks]

I agree with MasterSbilt. There is no right answer, depending on chassis, driver, tire choice, and other factors, it can all vary. There is definitely gains to be had when it comes to zero point rebound, the type of rebound curve being run, whether its digressive or linear. Again may things, 1" velocity is important but its usually because the amount of bleed run in the shock. The proper bleed is more important.

[xray]

I agree with MasterSbilt. There is no right answer, depending on chassis, driver, tire choice, and other factors, it can all vary. There is definitely gains to be had when it comes to zero point rebound, the type of rebound curve being run, whether its digressive or linear. Again may things, 1" velocity is important but its usually because the amount of bleed run in the shock. The proper bleed is more important.

I agree, and apologize with the vaugness of the question, But there has to be a "starting point" for weekly guy on a non glass smooth surface? I guess i hoping for an answer that i knew didn't exist.

I have been all over the map on RF rebound and cant put consistent back to back results together to get that "AHA" moment. Am I at least on the right page by taking it out in the slick to add grip?

Has anyone found out what "too much" compression in the LR front is either?

[xray]

Also by bleed do you mean in the stack or with the needle, or a combination?

Thanks for the reply!

[MasterSbilt_Racer]

Am I at least on the right page by taking it out in the slick to add grip?

Do you have so much that the front is ratcheting down? Are you on a paperclip or a momentum deal? The right adjustment on one night at one track can be completely wrong the next night at another track.

It reminds me of the early 4 link days when people argued about cheat sheets that didn't agree. One said stiffer lr spring tightens exit. The other said softer tightens exit. Guess what?, both can be right!

[xray]

Yes, full tight the rebound overcomes the spring with the bumper dyno test.

Majority of places i run are paperclip style, 1/4 miles

[JR. MECHANIC]

Penske, what's your thoughts on "critically damped"?

[PenskeShocks]

honestly, we typically never have much luck with critical damping. in theory or some simulation it should work, but in actuality, when it comes to driver feel, track conditions, tire wear, you will typically end up with a different curve. I know some engineers that live by it, some work, but majority we have seen struggle to make it work. They get so focused on critical damping, they end up tuning everything else around it.

[zeroracing]

Penske has a wide range of shocks available, what in your opinion is the best choice for a budget racer that runs one track week to week, as far as out of your line up of shocks?

[PenskeShocks]

If your running the same track week to week our 7500 non adjust is perfect. All our shocks use the same piston diameter so. internally you getting the same as our other shock, just not the adjustability. We have a lot of local guys and thats all they run, because like you said, they run the same track each week.We are finding we run a similar curve a lot of places, you could probably get away with all non-adjustables for a lot of tracks, may just need a few RF, RR, and LR options.