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?

[a25rjr]

Are you talking about hiking the RR?

Yes.......

[Kromulous]

I seen that Barry Wright car, that adjuster is cool. Nice to have if you wanted to really boost up the LR for a feature, or different track, crank it down say an inch, lower the LR and the raise the deck back up. You could work it out in the shop on your smasher numbers for the LR, probably the LF and RR too i guess to get back to your set up, and change the whole attitude of the car dynamically.

Overall thats what i am trying to do, make more room for the RF shock to expose more shaft for available travel. Plus not lose to much shaft trying to maintain a higher static ride height, aka the preloading question.

One thing i find intriguing, Bloomquist doesn't run all that crazy camber. His car lifts high, but the nose inst burred in the ground like the longhorns or the disco mobiles either. He seems to make it work without going to the extremes.

[billetbirdcage]

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?



Not 100% sure if this is what your asking:

Can you run the car with the RF shock basically extended all the way at ride hieght? meaning when the car is setting on the ground in the pits the 7" stroke shock has 7" of exposed shaft? Not saying it's ideal, but we'd won 5K+ races like that. The car is never in that position except in the pits.

[Mr.Kennedy777]

Yes.......I know quite a few mod guys that have been running 4 left and Z right for that reason. Even with relatively tame static bar angles that don’t move the tire rearwards much, the drive angle is always really good and coming off the corner you can see the RR coming up on the gas.

[Kromulous]

Yes Billet that's what i am after, maybe not the full 7, but 6 would be nice. Then i would probably have to work on rack or cross member clearance.

On the RR thing, on the slick tracks i go to, if i notice the RR doesn't compress coming off the corner or just stays the same ride HGT, the car is usually slow. Most of the fast guys from the middle off compress the RR a little. We race a lot at Florence that's where i notice it.

[Mr.Kennedy777]

Yes Billet that's what i am after, maybe not the full 7, but 6 would be nice. Then i would probably have to work on rack or cross member clearance. On the RR thing, on the slick tracks i go to, if i notice the RR doesn't compress coming off the corner or just stays the same ride HGT, the car is usually slow. Most of the fast guys from the middle off compress the RR a little. We race a lot at Florence that's where i notice it.I’ve never had any personal success with running the higher drive angles in the RR on slick. But perhaps the drivers doing this kind of thing and making it work for them don’t use up as much of the RR tire capacity on entry to mid, perhaps more roll steer on throttle, maybe running higher bite and softer springs like old school, and then are able to use more of the RR on exit?

[Mr.Kennedy777]

I dunno. I’ve seen some guys be really fast and sounds like they’re ripping pretty hard even on a slick. Maybe it’s a brake floater on the left rear deal while trail braking with more throttle or something. Really not sure about that one lol

[billetbirdcage]

Yes Billet that's what i am after, maybe not the full 7, but 6 would be nice. Then i would probably have to work on rack or cross member clearance.

Just to be clear, I'm saying we've ran with 6 to 7" of exposed shaft when at ride height but we aren't using all of that up in travel. Meaning I'm not traveling close to 6" to 7" from standard ride height. There was another reason I needed the shaft exposure and it wasn't travel related in my case which I don't want to get into. I Just didn't want people to misconstrue I was traveling that far.

[riddle28]

this may sound dumb but how are you raising the rf 1" above ride height and holding the car up in the pits? like say youre an 1" above and your static ride height wheel weight is usually 450 a 3.5", meaning it takes 450 lbs to hold that corner up. If it takes that much to hold it up, wouldnt you wind up being like 600 lbs at 3.5" wheel weight when the car gets to the normal static ride height? that may be my problem im trying to make the high travel stuff logical with my old way of weighing a car

[Kromulous]

Cant use the quotes thing, but yes i wanted to have more shaft available to make room for a bump stop or bump spring, and a stack.

Riddle28, not dumb at all i am tring to put all together myself, if you boost your ride height up to 4.5" (over the 3.5") your going to have to decrease your LR the same amount 1" at min. Still you might carry a little more weight on the RF, not sure. So in essence your rocking the car back on the LR, using the LF and RR as the pivot axis.

I think the key would be with all that travel you added, is to keep the spring rate soft enough initially to travel thru it and get the nose down on the track before you add to much weight to the RF corner.

[mickley.28]

Raise you right front by using a softer right front spring... the key is too keep the same load numbers when the right front is at full compression dynamically which can be done if a softer spring is used with higher ride height (more preload). You shouldn't even need to do much with the left rear (don't worry about static wedge numbers - you can throw them out the window anyway when the left rear is at full drop dynamically). Scale numbers are a thing of the past now.... the only numbers that matter are left side and rear percentages then load numbers when the car is at its dynamic state. It sucks because i spent $1500 on scales a couple years ago and now everything is setup on the spring smasher and I don't even need the scales much.

[15D]

how do you scale the car for rear percentage with the RF and LR no longer at ride height? My thoughts would be to use another set of shocks and springs that have the same spring rate at correct ride height? Thanks

[DEKconsulting]

just scale it where it sits after you set ur loads dont worry to much about ride heights

[MasterSbilt_Racer]

how do you scale the car for rear percentage with the RF and LR no longer at ride height? My thoughts would be to use another set of shocks and springs that have the same spring rate at correct ride height? Thanks

Ride heights don't effect percentage beyond the tiny amount from wheelbase change.

[regis78]

so what are they running for left side and rear when they do this

[DEKconsulting]

I usually start at 54.5ls% and 53rear%

[DEKconsulting]

Looks like alot of guys r running this deal down in flirida5

[DEKconsulting]

Florida sorry

[billetbirdcage]

I'm going out on a limb here and post this: Actually surprised it hasn't been deleted yet.

https://www.facebook.com/delphcommunications/videos/1689127984480618/


Let the theories begin, LOL.

[Racer63]

What did that car do right before he moved forward? Was it still on the lift?

[billetbirdcage]

What did that car do right before he moved forward? Was it still on the lift?




https://media1.tenor.com/images/0e42110c65d57aa0029a291585e200f5/tenor.gif

[TheJet-09]

Tungsten hood pins on the right side? I watched it about five times and still can't fathom what I just saw.....

[Jking24]

The crew guy lifted the car at the left rear so it would clear the lift when he pulled off. Rumleys stuff is usually really soft on the rf softer than most

[CCHIEF]

So what would clear the lift? Chassis?

[DEKconsulting]

thst sum bitch is way up there

[Matt49]

My guess: Super super super soft LR spring rate and super super super high LR shock compression. The car had sat on all 4s so long that the LR frame rail was on the ground. Crew guy lifted the car (easily, by the way, because of the super soft LF spring rate) so that that the shock could hold the car up long enough to get him over the pit lift as he pulled out.
If he sits too long in the line up shoot and the car ends up down that low he'll just crank the wheel as he gases up to make sure he gets LR hike. Kind of knowing how Rumley thinks, he probably put little wheels on the underslung to make sure it doesn't drag bad but it would still potentially catch and damage a pit lift.

[riddle28]

imagine what theyre able fudge out of the body when its like that.

[mickley.28]

That shows you how much these guys care about scale numbers. With the left rear and right front that soft and the car sitting like that he probably had -200lbs of wedge in the car in the static state. I assume they’ve doing super soft left and right front for a couple reasons. 1 - to lower rear deck height so they can have high dynamic ride height which equals more downforce and 2 - to help soften the left rear over the ruff parts of the track to keep the tire from braking traction (basically what he was doing with the Rumley device).

[MasterSbilt_Racer]

We never really cared about scale numbers, it was just all we had to compare notes. We didn't realize it. Lol.

[Jking24]

We never really cared about scale numbers, it was just all we had to compare notes. We didn't realize it. Lol. Agreed 100% Long before smashers came into the dirt seen i realized that attitude was everything. I knew scales didn't mean a thing but scaling was all we knew