5th coil spring choices

[DK1]

Seeing what people have had success with. I'm fighting a drive off issue in the slick where i blow the rear tires off coming off the corner and then the they finally hook about the flag stand. Car is a 2016 Blue/Gray Rocket. 300 lbs 5th Coil spring at 38.5".

Thinking of trying a 225 with a bump at 3" of travel as I already have all the pieces. Not sure I should look into a stack set up or not. Other than the standard rocket 300 lbs at 38" set up what has everyone had success with?

[CCHIEF]

Tell us more about your engine, fuel, tires and track dirt and size, shocks. Alcohol,peaky power band cam, tires, shocks and throttle control all come into play. The biggest advances in traction come from increased corner speed.

[Matt49]

The biggest advances in traction come from increased corner speed.

Ain't that the truth? The car with the most "forward bite" is the car that doesn't need it :-)

I'm personally a fan of softer 5th coil. That being said, you have to keep in mind what the lift bar travel is doing to your relative j-bar pinion mount height. You may have to compensate accordingly for this.

[MasterSbilt_Racer]

It got better because you stiffened it by moving it out. Move it back and stiffen the spring.

[25jrjr]

We had the same issue on our blue/gray Rocket. Josh advised us to soften our 5th coil to a 250, and lo and behold, it worked. fwiw....we watched him do it to his car and he won the woo feature at brp.

[MasterSbilt_Racer]

We had the same issue on our blue/gray Rocket. Josh advised us to soften our 5th coil to a 250, and lo and behold, it worked. fwiw....we watched him do it to his car and he won the woo feature at brp.

Slowest I have ever been is with a 250. Lol. Never worked for me

[Matt49]

I personally think 5th coil rate and location is a driver feel thing...at least a big part of it. Meaning that there is more of a comfort with a certain combination that may not necessarily show up on the stopwatch.

[hipower17]

at what lenght was your 5th set at 25?

[25jrjr]

at what lenght was your 5th set at 25?

I never measured the length, but one hole in front of their standard setup hole.

[DK1]

well I tried a 225 with a bump that hit at 2.6" of travel and had it at 36.5". Needless to say car was slow and still wheel spinning.


Tell us more about your engine, fuel, tires and track dirt and size, shocks. Alcohol,peaky power band cam, tires, shocks and throttle control all come into play. The biggest advances in traction come from increased corner speed.

Engine is a 415 @ 800hp. Fuel is 114 HCR+. Tires are LM 20's. Tracks are mostly 3/8's. Shocks are fresh JRi's.

When it's slick the car is flat. The rear end is not driving the tires under the car and not lifting up. When it's tacky the car is a rocket ship, very fast. When it's slick might as well throw the boat anchor out and go fishing.

Long story short. Car turns good, can roll through the corner and carry the speed just no forward drive when the car is pointed straight.

So 350 5th coil spring or higher?

[CCHIEF]

There is no major gains to be made with the lift bar unless something is really out to lunch there. What car? Springs? When does it go flat, or is it flat all the time when slick? OK/up when grip? Possibly too much rebound in RF shock? You need the car to bar up, and that is body roll induced, fwd bite is the product. What year and make/model is the chassis? If your way off from the manufacturers baseline I don't know where to go, too many variables. Video of car in action is very telling sometimes.

[DK1]

2016 Blue Gray Rocket. Standard set up.

It's flat all the time in the slick. Gets up when theres ANY kinda moisture in the track.

I get the body roll, major gains ect but if the 5th coil doesn't get any lift and body separation traction is going to be affected. If the tires aren't in the race track or are over powered they're just going to spin. If they spin the axle won't wrap up because there's not enough resistance (traction) to wrap up and lift the body up.

[CCHIEF]

Start pulling spring rubbers to get roll back in the slick. Gotta get up on the bars to add weight to lr for drive. the hook is body roll initiated traction get the roll back in the car and it will come to life

[billetbirdcage]

When it's slick the car is flat. The rear end is not driving the tires under the car and not lifting up. When it's tacky the car is a rocket ship, very fast. When it's slick might as well throw the boat anchor out and go fishing.

Seen that exact thing before, hikes fine if there is some brown but if both tires in the black it's flat as a pancake no matter bar angles or etc. Is your battery mounted to the right over on the X, instead of over behind driver or over LR area? Is you left side % less then 54.0% (like 53.8% with driver)? I'm assuming this is a non xr1 car correct?




Long story short. Car turns good, can roll through the corner and carry the speed just no forward drive when the car is pointed straight.

So 350 5th coil spring or higher?

Your driveshaft isn't too long is it? and hitting trans just may not notice it in the traction cause there is traction there

[TheJet-09]

So I remember seeing a specific load number mentioned in this thread, and I wanted to go back and confirm the number. And I now see that "people" must have been displeased with the amount of information the OP provided (look at the time and reason for editing).

Hey @DK1, I applaud your openness with information in merely trying to help your situation! And I hope you got the information you need. But for those who apparently had issues, those who think everything in racing needs to be so "hush, hush!" Get over yourself!

I realize much or most is gained through trial and error, and once learned is not often shared, but in the end what are we really doing for our sport? I see a lot of chatter lately by front runners about "this lapped car held me up" or "a lapper cost me the race." Did any of those leaders ever think of maybe going over and helping one of those lappers? Even just a little? "Hey, I see you're struggling getting into the corner. Where are you at on your RF?" You're not going to take a back marker and turn him into a feature winner just by sharing some information. But if you make him a little better, isn't that gonna help you not get "held up" when you're leading? (And I'm not saying the OP is a back marker, as I don't even know who he is.)

I attended one of the first Mark Bush classes, and he made it clear that he wanted us to better understand this stuff to keep us in racing. Because even though his business at the time was selling parts, when we don't understand something and start guessing, we start buying a bunch of parts (like 20 different springs or something). Sounds good on paper, but after a while we're broke, and guess what? No more buying parts from Mark Bush because we quit racing.

Nobody gives a rat's tootie what I run on my car, but if you ask me a question I'll give you a straight up, honest answer. I don't even back my car into my pit because I have nothing to hide. I used to do the tarp thing back in the 90's, but not because I had something trick, it was really just to mess with people. I'm sure there are drivers out there that could win (locally at least) in my car. But that doesn't matter, because they don't drive my car...I do. So whatever works for them may not work for me, but to act like they've got the secret formula or something...come on.

There are some who don't hesitate to share very valuable information, like Matt49, Mastersbilt Racer, and Billet Birdcage just to name a few, and I have always appreciated their posts very much. But I feel sorry for @DK1 for whatever was said to him. The guy's just trying to get better...

[Matt49]

I kind of agree with CCHIEF here. A 5th coil change isn't going to take you from junk in the slick (what you're describing) to running up front. Go back to standard 5th coil rate and location and figure out why you're not getting any body roll. Something could be in a slight bind that tractioned up conditions is overcoming. Body roll starts with side bite and then you can really start to hike the LR and get forward bite.
Check both right side shock travel indicators after a run in the slick and this can tell you a lot about where you're lacking side bite.
Where are your j-bar heights at each end?

[MLR19]

If you are really 2000 lbs @ 3" travel in the slick, I would expect the car to act exactly as you describe. I would wory less about load numbers & more about RF travel when the track slicks off.

[slingindirt83]

Im with MLR19 . That seems high for a 3" number. Try to get that at 4" and see if it helps. The numbers and travel go hand and hand . So to me it just sounds too stiff at that amount of travel.

[MasterSbilt_Racer]

So I remember seeing a specific load number mentioned in this thread, and I wanted to go back and confirm the number. And I now see that "people" must have been displeased with the amount of information the OP provided (look at the time and reason for editing).

Hey @DK1, I applaud your openness with information in merely trying to help your situation! And I hope you got the information you need. But for those who apparently had issues, those who think everything in racing needs to be so "hush, hush!" Get over yourself!

I realize much or most is gained through trial and error, and once learned is not often shared, but in the end what are we really doing for our sport? I see a lot of chatter lately by front runners about "this lapped car held me up" or "a lapper cost me the race." Did any of those leaders ever think of maybe going over and helping one of those lappers? Even just a little? "Hey, I see you're struggling getting into the corner. Where are you at on your RF?" You're not going to take a back marker and turn him into a feature winner just by sharing some information. But if you make him a little better, isn't that gonna help you not get "held up" when you're leading? (And I'm not saying the OP is a back marker, as I don't even know who he is.)

I attended one of the first Mark Bush classes, and he made it clear that he wanted us to better understand this stuff to keep us in racing. Because even though his business at the time was selling parts, when we don't understand something and start guessing, we start buying a bunch of parts (like 20 different springs or something). Sounds good on paper, but after a while we're broke, and guess what? No more buying parts from Mark Bush because we quit racing.

Nobody gives a rat's tootie what I run on my car, but if you ask me a question I'll give you a straight up, honest answer. I don't even back my car into my pit because I have nothing to hide. I used to do the tarp thing back in the 90's, but not because I had something trick, it was really just to mess with people. I'm sure there are drivers out there that could win (locally at least) in my car. But that doesn't matter, because they don't drive my car...I do. So whatever works for them may not work for me, but to act like they've got the secret formula or something...come on.

There are some who don't hesitate to share very valuable information, like Matt49, Mastersbilt Racer, and Billet Birdcage just to name a few, and I have always appreciated their posts very much. But I feel sorry for @DK1 for whatever was said to him. The guy's just trying to get better...

I can't believe anyone got upset over such dated info. Oh well...

[25jrjr]

Slowest I have ever been is with a 250. Lol. Never worked for me

I agree....that was my first adventure with a longer/softer. Our local track was Putnam County and you know how sandy slick that place was. We had to put a ton of side bite in the car as well.....equal trailing arm lengths, lowered j-bar, and stacked 350/150 left rear.

[DK1]

Thanks for the help everyone! It is much appreciated! Thank You!

That 3" number was actually the 4" number my mistake.

I made some changes and went through the car and found somethings. Will try it again on Friday.

[MasterSbilt_Racer]

Thanks for the help everyone! It is much appreciated! Thank You!

That 3" number was actually the 4" number my mistake.

I made some changes and went through the car and found somethings. Will try it again on Friday.

That makes more sense. Good luck!

[talclipse]

So are you guys always looking for X amount of load at 4" of travel? Or does that value change throughout the night? Which is more important, the wheel load or achieving the desired travel?

[MLR19]

As the track slicks off & lap times get slower, the car will generate less load. The RF front must either be softened or preload taken out of bump stop to allow the same travel with less load. How much depends on track condition & driving style.

[CCHIEF]

Preload taken out of bumpstop??Did You mean spring?

[zeroracing]

Probably meant shims out of the bump stop.

[MLR19]

Correct, remove packers to delay bump stop engagement, resulting in more travel with less force.

[CCHIEF]

Got it, now I'm with you.

[7uptruckracer]

Travel is way more important from a camber gain and geometry standpoint, but these days much more importantly from an aero standpoint. Granted on exit you do see some nose lift because the shocking they use in the slick to get some weight transfer

[huckleberry_hound]

Seen that exact thing before, hikes fine if there is some brown but if both tires in the black it's flat as a pancake no matter bar angles or etc. Is your battery mounted to the right over on the X, instead of over behind driver or over LR area? Is you left side % less then 54.0% (like 53.8% with driver)? I'm assuming this is a non xr1 car correct?

Do you recommend moving battery to center of car?



Your driveshaft isn't too long is it? and hitting trans just may not notice it in the traction cause there is traction there

We had this problem and overlooked it for some time until we found the driveshaft was too long and bottoming out against trans... didn’t seem to hurt when track was heavy but not enough drop when it slicked off

[DEKconsulting]

alot of guys have this problem with drivelines and is often overlooked i cant stress enough u have to make sure it aint bindin or bottoming out or every thing ur doin or have done is worth nothing.