high travel rf/lr

[riddle28]

Might be kind of a dumb question, but ive got an older car and was wondering how these newer cars get the high travel in roll. i have heard they leave the lr lower/ rf higher statically to get the travel. might be a dumb question but any insight?

[MasterSbilt_Racer]

Might be kind of a dumb question, but ive got an older car and was wondering how these newer cars get the high travel in roll. i have heard they leave the lr lower/ rf higher statically to get the travel. might be a dumb question but any insight?

RF strut locations are raised or rear strut design. Rack plates are higher. In some cases, ride height is manipulated too. Everyone pretty much sets the cars to where they think it travels, or a travel reference provided by their guru of choice and sets this pseudo dynamic load with the spring smasher.

[Punisher88]

Pretty much exactly what he said. I've lowered my static lr ride height that way I can raise the deck height and have it higher dynamically. Plus different spring setups so I can get it lower statically but still have my desired dynamic load number. And some are also raise the rf a half to 3/4 to help lower the lr some more statically. But still have the same load at 4.5 or 4.75 of travel. I feel like it has more to do with areo than anything. Just being able to raise up the rear deck higher and higher but still meet the rules for when you're going through tech.

[riddle28]

im in the process of dropping my deck now. pretty good chore on an old car lol. Im getting 4-4.5" of rf travel but im setting my ride heights off my setup book made years ago. ive recently bought a smasher so ill hopefully do some learning with it this year

[Kromulous]

I was looking at some CFD analysis a guy did on these cars, its interesting how much of a dead area behind the Drivers head on the Spoiler is created by the helmet and seat.

So unless you can get the spoiler so high on the left side that its in clean air. I think working on smoothing this turbulence would be cost effective.

Also the analysis showed a lot of "wash out" of aero behind the the driver as well, air exiting thru the sail panel area on the left side, caused by the yaw in the car somewhat, but the turbulated air mainly wanted to exit that way.

[Punisher88]

You're in an 09 bwrc correct? Before I got rid of mine 2 yrs ago I had really gotten fast with 375 lf, 325 rf 200 lr, 400 ( yes 400) rr, and had 3 inches between the lower and frame on both sides I think or 3.5. Can't remember. Whatever the right side calls for I matched on the left side. With 54.0 and 54.0 percentages and rode out. It would fly. Had .25 preload in the lr with exactly 100 lbs of bite at drop. Had the left front lower pulled ahead of the rf by .125 and it turned in and scotched like a dream and drove hard leaving. That year model bwrc is special. Don't get rid of it.

[riddle28]

im gonna pm you punisher

[riddle28]

clear your pm

[Punisher88]

It's cleared.

[billetbirdcage]

For those of you that don't know: Whatever you raise the pin to pin measurement on the RF, typically the LR deck hieght changes the same amount. So increasing the RF 1" lowers the deck 1", so you raise the LR deck back to legal and when on the track the car has 1" more aero.

This has been going on for a long time now, just look at pics of the world and see how high some of those nose's are. Some where 18" off the ground, yes we measured, lol.

[Punisher88]

Exactly^^ I haven't checked mine after just doing the rf on its own but it does lower it significantly when I make other changes as well.

[7uptruckracer]

How are you accomplishing it? I get we run the car st Max RF travel so all that truly matters is final load.

For those of you that don't know: Whatever you raise the pin to pin measurement on the RF, typically the LR deck hieght changes the same amount. So increasing the RF 1" lowers the deck 1", so you raise the LR deck back to legal and when on the track the car has 1" more aero.

This has been going on for a long time now, just look at pics of the world and see how high some of those nose's are. Some where 18" off the ground, yes we measured, lol.

[Basecircle]

I’m still more comfortable in the old-school scaling methods. Jacking the RF even a tiny amount makes HUGE differences. Is this all just a band aid way of meeting deck height rules, or are there big performance gains to be had? I’m assuming it works best on a 2-stage stack setup in the RF so you can adjust it to get the nose down easily from its high static height? Also really soft LR? Not something I’m in a hurry to tinker with, but I’m curious what all needs taken into consideration. I know you can’t just raise the rf 1” and go race. Haha

[Kromulous]

Yeah jacking up the RF will be moving CG around a little. Although getting that spoiler up in that clean air is the deal, on higher speed tracks i would think is even more important, Eldora etc.

Anyway, i am in the process of mapping my RF shock spring set up and i noticed to get ride height up 1" over std how are they doing this? Only thing i can think of is pre-loading the spring?

So say i have 425lbs on the RF corner static, and i have a 275 lb normal spring. At ride height you would need to compress said spring 1.54". 7" shock would show 5.46" remaining travel. That's if your shock mount can handle that much travel, basically zero droop, most cars have 1" or so? So that puts it down to 4.46" remaining travel. I think thats close to a standard set up.

Anyway is my thinking completely off here? but to run a soft initial spring rate, stack, they have to be preloading the spring to get the RF to stay up in the air, until its on the track, and then compresses down into its dynamic state.

I have seen pics of Davenports car on the grid, wow it looks like a dune buggy. Air shocks i guess...

[Mr.Kennedy777]

Yes that’s right. Also you need to account for how much more spring travel is there before it gets down onto the limiting device to see how much you need for rate down there without being too stiff. By absorbing more of the total weight transfer into the spring, you do reduce the amount you need to absorb into the bump, which is always a good thing because it means potentially softer bumps and better compliance. The car isn’t going to transfer more weight than normal from left to right except for that brief moment before it gets down and stays down. Once it’s down and tied down more is stored in the spring, and less in the bump. This can also help weight transfer because you have more stored inside the ride spring.

[Mr.Kennedy777]

If you can take 275 or 300 pounds off the bump and store it in the spring that’s more energy in a useable form over more travel than 1/4” or 1/2” inside a bump

[TheJet-09]

I saw Eckrich (Iowa) selling a Barry Wright on line, and in the pics there is a screw jack set-up for the RF upper shock mount. I assume that is how one could go about raising the RF without changing the pre-load on that spring. But you'd still need to be able to get it to compress down to the same end point in order for it to benefit the height of the LR, right?

[a25rjr]

Why are we not worried about getting the rr up in the air? I remember a modified and dlm had great success during Speedweeks, several years ago!

[Mr.Kennedy777]

I saw Eckrich (Iowa) selling a Barry Wright on line, and in the pics there is a screw jack set-up for the RF upper shock mount. I assume that is how one could go about raising the RF without changing the pre-load on that spring. But you'd still need to be able to get it to compress down to the same end point in order for it to benefit the height of the LR, right?

It would change pre load on the spring if the spring was on the shock. You’re not adjusting the pre load on the adjuster nut, but you’re pushing down on the shock which would raise the car you would still change your spring pre load. I think with the amount of pre load built into some of the springs this is a nicer option because they can get a little tight on the adjuster if you’re running a bump setup. Being able to make fine adjustments in shock height at static is nice and you can always re set pre load if desired or decrease it and adjust the shock height for different things going into the RF. I think personally it would just make quick adjustments and fine tuning easier, my personal opinion but I could be way wrong.

[Mr.Kennedy777]

Why are we not worried about getting the rr up in the air? I remember a modified and dlm had great success during Speedweeks, several years ago!

Are you talking about hiking the RR?