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#1 BBSS Setup Bump Stops vs. No Bump Stops
SLMChamp

Posts: 37
rating

09/09/2009 8:09 PM

I have a straight rail outlaw late model that I run at a 3/8 mile 12 degree banked asphalt track.
I've been running conventional set-ups but I would like to try the bbss set-up but I have a few questions about it.

Bumpstops vs no bumpstops? What benefit do they have?

How low do I need to have my crossmember to the ground with or without bumpstops?

Is running with or without bumpstops the same except that the bumpstops are just controlling the height of the car?

Without bumpstops I'm worring about bottoming out my car if I have to blow it deep into the corner racing with someone.

This is what I have in my car to go test with, am I in the ballpark?
No Bumpstops
LF: 225 RF: 250
LR: 300 RR: 650

2700 lb car
60% left side
58% wedge

10 inch slicks

1 1/8 inch swaybar one piece.

I have a four double adjustable shocks, fronts are built for bbss with a lot of rebound. I'm also worried my sway bar needs to be bigger. If so how big and what will it do.
 
#2  
Rock

Posts: 2588
rating

09/09/2009 10:39 PM

I don't know what you had before for springs, but to me you have way to much rear spring for the sway bar, to me the car should be really loose.
The whole concept for a BBSS setup is to not have to run very much cross, some where around 48% to around 53% cross and the only way you can do that is with a very big sway (the term "Big Bar" Soft Spring)and with the rear roll center very low.
If I were you I would stay with your conventional setup until you get some better knowledge about the BBSS setup, the BBSS setup is very hard to work with, when you have it right it is very good, but if your off just a tick you are out to lunch in a big way.
That's just what I would recommend.
I talk to people all across the country and I have talked to people that have tried what you want to do and ended up having to buy a new chassis because they hit the wall really really hard. Now don't get me wrong I run a BBSS setup and love it, but its not for everybody as a matter of fact it is for very few people maybe only 30 to 40%. I have talked to people that have tried to run it for a whole season or more and finally gave up and when back to their proven conventional setup.
Your sway bar is rated around 300lbs, or less. When I run a 650lb RR spring I use a 1195lb rated sway bar, with the rear roll center around 9".
The rule of thumb is twice the rate of your RR spring is a starting point for the sway bar, example 650lb RR spring would calculate to a 1300lb rate sway bar, so you can see where I'm coming from.
Or turn that around if you use a 300lb rated sway bar you would run somewhere around a 150lb RR spring, now remember this would be a starting point.
 
#3  
Rock

Posts: 2588
rating

09/09/2009 10:54 PM

I forgot to say, but I didn't want to get into bump stops, thats a whole different can of worms, but here's a little info.
Now bump stops are much easier to work with.
If I were you I would try bump stops but with a conventional setup, to convert to a BBSS and bump stops all at once you would probably want to hang yourself.
The concept for bump stops in the front is so you can run very very soft front springs, the softer the front springs the better the car will turn in the middle, and the RF bump stop loads the tire and makes it stick better, don't confuse loading the RF with a bump stop to loading the RF with cross weight, they are two totally different things.
 
#4  
SLMChamp

Posts: 37
rating

09/10/2009 4:21 AM

Thanks a ton Rock. This is why I'm asking the questions.
My Panhard bar was going to be set at right side frame at 9 inches and the left side rear end side 10 inches. They told me to run a reverse split to hook it up.

Is the only problem I have is to small of swaybar? does everything else seem ok.

I thought the swaybar seemed small.
conventional set up I ran around 325's up front and 200lr and 175rr.

The other reason why I asked about the bump stops is because another guy I know told me if I run the front springs and swaybar I would be better off running bumpstops. If I run bumpstops should I still run a larger swaybar?

So what your saying is over the winter I should look at installing a 3 piece swaybar because I can't find that big of a one piece swaybar.

I just wanted to try something before winter so I have something to work on all winter.

Again thanks for advice. If you have any idea what I could try I would like the advice.
 
#5  
Rock

Posts: 2588
rating

09/10/2009 5:02 PM

The sway bar is based off of the RR spring, use the formula I gave you for a base.
If this is a coil over car around 2700lbs to 2900lbs Your front springs are to stiff, without bump stops you should be able to run around 225's, with bump stops you should be able to run around 150's, I have a 150 & 175 in my car @ 2750lbs 18 degrees of banking on a 5/8 mile track. Keep the rears the way they are.
 
#6  
SLMChamp

Posts: 37
rating

09/10/2009 6:55 PM

Thanks again. So If I understand you correct.

I should try:
Conventional set-up with:
LF:225
RF:225
LR:200
RR:175
Swaybar 1.125
58ish cross
Shocks?????? 6's in front and 4's in the rear
Or

Use bumpstops:
LF:150
RF:150
LR:200
RR:175
Swaybar 1.125
58ish cross
Shocks?????Use my tie down shocks up front?



 
#7  
Rock

Posts: 2588
rating

09/10/2009 8:51 PM

That would be a good "starting" point. Now if you need to change any springs, use the front springs for the entry & middle fix that if you need to "first" use the rear springs for the exit and only do that change after you get the entry & middle good first.
Now remember to adjust the middle of the corner use the track bar, if the car is tight in the middle raise the track bar 1/2" both ends at a time until you get close then go 1/4" up or down both ends at a time.
If the car is loose in the middle go down on the track 1/2" both ends at a time until you get close and then 1/4" up or down both ends at a time.
Now if the car is tight on exit take out some cross about 1% at a time depending on how tight the car is, maybe you need to take out more then 1% and do that using all four weight jacks maybe two turns each, you know how to do that correct, in this case put 2 turns in the LF, take out 2 turns RF, take 2 turns out LR, put in 2 turns RR. Doing it this way you will keep the ride height very very close.
Now if the car is loose on exit do just the opposite with the turns and start preloading the sway bar, don't go crazy on the bar, I would not go over 8 turns, and remember the more you load the bar the lower the left side of the chassis will go and the higher the right side of the chassis will go.
Now if you start using bigger sway bars the less max tunes you want to use on preloading.
Now if your going to start using bump stops, there's a lot of controversy in this area, some use them on both fronts, some use them on just the LF, some use them on just the RF, some use them only on the LR.
I'm not going to get into using bump stop on the LR unless you want some info on this.
I use bump stops on the RF & LR.
But if you ask 10 people you will get 10 different answers, so I don't know what to tell you in this area, except testing testing testing will tell you what works best for you.
Only use what people tell you as things to consider, including myself
nothing is black & white, some people will tell you only this will work or that will work, you have to figure out what works best for you, in all areas.

 
#8 Re:
mikeyb

Posts: 347
rating

09/20/2009 10:52 PM

Quote posted by SLMChamp:Thanks again. So If I understand you correct.

I should try:
Conventional set-up with:
LF:225
RF:225
LR:200
RR:175
Swaybar 1.125
58ish cross
Shocks?????? 6's in front and 4's in the rear
Or

Use bumpstops:
LF:150
RF:150
LR:200
RR:175
Swaybar 1.125
58ish cross
Shocks?????Use my tie down shocks up front?


For your "conventional" setup, I'd go up 100 pounds on the RR and go with at least a 1.375 sway bar. I've run a similar soft conventional setup. Start cross at 53-4% and add bar to get to 56%. And probably start with your tie-down shocks first. A 6 (if meaning a Pro 6) isn't enough. I would think you'd need a 4c/6r at least up front.

For bumpstops, a 1.4375 bar to start and a RR around 400# and have a lot of spring rubbers handy. Start cross at 50-2% cross and add 1-2 turns of bar preload. The nose drops and is supposed to stick there with a lot of shock rebound. The RR drives the car through the middle and off.

There are a lot more factors involved (as many have mentioned around this section) than just changing springs and bar for either setup, and it will take some diligent testing to figure it out. I do not recommend changing it just for one race weekend, unless you have nothing to lose.
 
#9  
SLMChamp

Posts: 37
rating

09/21/2009 9:28 AM

Well guys this is what happened last weekend. I ran my conventional setup and was not fast enough to make the show. So I changed my set up half way thru the day. I never ran this set up before.
This is what I put in my car with three sets of hot laps left
No Bump stops
LF: 200 RF: 225
LR: 300 RR: 650
2750 lb car
60% left side
58.5% wedge
3.750 stagger
Panhard bar was at 11 inches on the frame and 12 inches on the rearend.
1 1/8 inch swaybar one piece with two turns on it.
The shock rebound were set at 16 LF 8 RF

The car was tight in the middle. I qualified in the show. I was a ton faster with this set up. I understand I don’t have the correct bar and stuff but this is all I had in the trailer so I thought I would try it. When I got to the feature the car was tight and pushing up the track. The front had very little grip. Once I got the car turned it seemed loose. But the car wouldn’t turn. I’m done racing for the year but I was just wondering what should I of worked on. Is there to much wedge or raise the panhard bar? Was the 300LR driving the car to much? Should I of went down and what would that of done?
 
#10 Re:
bigman21

Posts: 157
rating

09/21/2009 9:46 AM

forget about the feeling of being loose sounds like the car was so tight once it gripped the front it snapped loose fix tight and loose will go away. definatly need a bigger bar between not having enough bar and that much wedge rf was screaming for mercy.did you try taking wedge out?

at least you made the show
 
#11 Re:
bigman21

Posts: 157
rating

09/21/2009 9:47 AM

also what to you have for front or rear percent?
 
#12  
SLMChamp

Posts: 37
rating

09/21/2009 12:35 PM

Thanks for the help.
I know some of the loose off was tight. No dought there. But I was leaving two black marks all of the way down the straightaways.
I didn't have time to do alot of adjusting. We didn't get a practice session before the feature.
So if I run a bigger bar I can take out wedge? Which on these set ups might be the answers.. I know in my conventional set up if I would run a big bar it would make me tight. I understand these set ups are different.
Because the big bar holds the LF down and it doesn't make you tight????
Don't these set ups run wedge around 53%
My rear percentage is 50.5 w/o driver.

What about the LR spring seems heavy to me. This is what I was told to try by a local guy. Just wonder what the 300 does for me. Next year I would go try a 1.5 swaybar and around 53% wedge. I might even try to practice at a track yet this year. Maybe next year I'll get into bump stops
 
#13 Re:
bigman21

Posts: 157
rating

09/21/2009 3:22 PM

wedge is an area that greatly depends on the driver and driving style 10 different drivers may take 10 different wedge amounts by as much as 6-7 percent so that is something you will have to figure out but probably 53- 55 range is probably good. a bigger bar doesnt mean you are going to need less wedge but with a small bar you will have a lot of roll with lighter springs so it mean alot of weight is transfered to the rf and with 58 or so wedge you already have a lot on it. when you have heavy springs in there they are already helping to control the body roll and then you put a bigger bar in there you create a big bind but when you have soft springs you need the bar to keep the front end from rolling and keeping weight of that lf tire. the lr seems high but i have seen some cars running as much as 400 back there. but generaly 150 to 225 in the left rear. we run at a 3/8 11 degree track and i always ran like a 200 over there.
 
#14  
sledder

Posts: 135
rating

09/21/2009 6:39 PM

hey SLMchamp..my opinion would be to definitely get a bigger bar..rock has qouted it on here many times...half the rate of the sway bar should be the right rear spring....our season is over,our last night was an invitational,so i started playing with wegde and rear spring rates..i had a 500lb sway bar with a 250 R.R spring,and usually run a 200 L.R. with 52% wedge.so i started increasing the L.R spring and decreasing the wedge..i ended up with a 250 L.R and 50% wedge and the car turned awsome and had a tonne of bite off the corner...the track bar was at 10.5 left side and 11.5 right side(frame side)...use the track bar to get the car to turn in and in the middle,and wedge/sway bar preload for the exit.(is what rock has said many times on here)but i used the left rear spring and compensated with less wedge,thats what we kept doing and it worked great for us...
 
#15 Re:
mikeyb

Posts: 347
rating

09/21/2009 7:34 PM

Quote posted by SLMChamp:

The car was tight in the middle. I qualified in the show. I was a ton faster with this set up. I understand I don’t have the correct bar and stuff but this is all I had in the trailer so I thought I would try it. When I got to the feature the car was tight and pushing up the track. The front had very little grip. Once I got the car turned it seemed loose. But the car wouldn’t turn. I’m done racing for the year but I was just wondering what should I of worked on. Is there to much wedge or raise the panhard bar? Was the 300LR driving the car to much? Should I of went down and what would that of done?


A lot less wedge- about 8% less. 1.5" swaybar (recommend changing to a 3-piece in the offseason if a lot of your fellow racers run them. Easier to borrow.) and adjust from there.

Depending on severity of the center push, raise the J-bar up .5" or 1" at a time.

If still tight in and thru the middle, drop that LR down to a #200.

With these setups, all the expected numbers/percentages are just that- numbers. Also move some weight so you're .5-1% nose heavy.
 
#16  
mikeyb

Posts: 347
rating

09/21/2009 7:38 PM

one other thing... try cutting down your rear stagger to 2.75-3". I found that was the best range on a 3/8 mile with ~8-10 degrees of bank.

running a non-spooled rear end requires even less stagger.
 
#17 Re:
Rock

Posts: 2588
rating

09/21/2009 10:25 PM

Quote posted by sledder:hey SLMchamp..my opinion would be to definitely get a bigger bar..rock has quoted it on here many times...half the rate of the sway bar should be the right rear spring....our season is over,our last night was an invitational,so i started playing with wedge and rear spring rates..i had a 500lb sway bar with a 250 R.R spring,and usually run a 200 L.R. with 52% wedge.so i started increasing the L.R spring and decreasing the wedge..i ended up with a 250 L.R and 50% wedge and the car turned awesome and had a tonne of bite off the corner...the track bar was at 10.5 left side and 11.5 right side(frame side)...use the track bar to get the car to turn in and in the middle,and wedge/sway bar preload for the exit.(is what rock has said many times on here)but i used the left rear spring and compensated with less wedge,thats what we kept doing and it worked great for us...
Good job Sledder, you did your home work and it payed off for you, good going.
 
#18  
expired_account

Posts: 3
rating

09/21/2009 10:31 PM

how high, above travel indicators, do i start my bumpstops? soft? medium? hard? is it all trial and error?
 
#19  
SLMChamp

Posts: 37
rating

09/22/2009 5:05 AM

Thanks Sledder and Rock.
I didn't have any other parts with me. I really wasn't planning on trying this. The conventional setup just wasn't cutting it. Yes I remembered what ROCK wrote and that bothered me the whole race knowing my stuff was wrong. That is why I wondered about the LR spring. With that much LR spring I should of took out all the wedge. I did find a 1.5 inch bar but they wouldn't give us a practice session. My goal was 1.5 bar and take the wedge down to 53.5% and try it.
 

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