Let's talk anti-roll bars

[Matt@BOS]

I've been testing and tuning my '69 Camaro with DSE underpinnings this year to get it to drive they way I want. I've played around with springs, sway bars and tires to try and get the car as neutral handling as possible. I try to only make one change at a time, but occasionally I will have to make two, i.e. if I'm replacing tires, sometimes I will change brands and throw on different springs as well.



Now, to what I wanted to discuss, is there a point where stiffening the rear of a car will decrease grip at the front, and/or increase grip at the rear?
Of the changes I've made, increasing rear sway bar stiffness seemed to increase the amount of understeer into transitional oversteer that I experienced. Additionally, I recently made a change to the front of the car. I increased spring rate and deccreased roll bar stiffness to try to get the car to have less brake dive with similar steady state cornering, but ended up with a car that seemed to put power down exceptionally well but exhibited more understeer, especially applying power with slight steering input. I'm curious, can limiting the amount of roll on the back of the car keep the outside front from loading up with weight, and "biting?"


Matt

[Ron Sutton]

Hey Matt,

so we all can have a better feel of what you're doing ... can you share all the details of your suspension ... tire brand & sizes, spring rates, anti-roll bar types & diameters, type of shocks, type of rear suspension (assuming it is a double A-arm front suspension) ... and front end geometry if you have it?

Plus ...
How heavy is the car?
Power output, trans & gear ratio?
What type of driving are you doing ... AutoX, road courses?

That will help get us all out of the dark to be able to engage in somewhat educated conversation.

[Rod]

yea!!! Matt tell me all about your spring rates, anti-roll bar types & diameters, type of shocks, type of rear suspension.......really I noticed the same thing I increased the rear bar on the car and stiffened the shocks and ended up with more traction

[Ron Sutton]

You're funny Rod.

I think I can tell you what's happening ... and why ... but I want to be sure of the set up ... so I don't stick my foot in my mouth. I wouldn't want to make assumptions & jump to the wrong conclusion.

You know what happens when you make assumptions ... right? You make an ass out the umptions. (Hmmm ... that didn't sound right).

[Matt@BOS]

Hey Ron, funny you should ask for details. I'd originally typed out a ton of details and then deleted them because I thought it might be better to talk from a broader conceptual level at first. I was hoping it might draw more people in, especially if they had personal experiences and questions of their own.

Here are the details:

1969 Camaro with 454 LS7 (gen IV), T56 Magnum, 3.73 gears, 18x9 and 18x11.5 wheels with 275/35 F, 315/30 R tires. DSE subframe and quadralink. 3500lbs with a full tank, sans driver. 51/49 F/R weight distribution. cross weights are pretty close. I think the biggest short coming of the car, which I am currently addressing is the narrower front than rear track width.

Anyway, I started the year with 450lb front springs and a .250" wall front bar with 250lb rear springs and DSE's 1-1/8" rear bar on the softest setting (of two settings). The car had pretty good bite and turn in, but it was wearing the outside tires badly and it was the tire was being overloaded because it would skip, or hop once before taking a set. The easiest adjustment I could make at the time was to adjust the rear bar and stiffen it up since pretty much any tuning guide says to soften the front or stiffen the rear to reduce understeer. Seeing as the front felt too soft I stiffened the rear, only to notice that I now had decent initial turn in with terrible mid corner push turning into transitional oversteer, making the car really loose putting power down.

Eventually I arrived at a set up I was reasonably happy with. 575lb springs/.250" bar front and 300lb/1-1/8" bar on the stiffest setting. I ended up changing though because the rear shocks I had were shot, so I put in working shocks (JRI) and replaced the springs with 275 to test. and I also wanted to give Falken tires a try. These changes gave me understeer that was most noticeable on turn in, but the functioning rear shocks greatly fixed traction issues as I used to start losing traction on auto crosses mid way through a straight since the rear springs wasn't being controlled.

In an effort to smooth turn in transitions I changed the front to a stiffer 700lb spring and softened the anti roll bar to .120" wall thickness with the hope being that it might solve the lack of turn in under braking. The car has always felt it never wanted to respond to trail braking, with the best turn in happening when the car was slowed and without your foot on the brake or gas.

I know there is probably no such thing as too much information, but there are a lot of different little things going on, and as I'm sure you know, fixing one thing always changes something else.

Matt

[Ron Sutton]

That is great information that helps me to have a little clearer picture. I still need a "few" more details.

When you talk about your front sway bar, you mention wall thickness but not diameter. Please post the diameter ... and effective bar rate ... if you know it.

In the rear, you mention having the 1-1/8" sway bar on the stiffest setting. Please post the effective bar rate for it too ... if you know it.

Are you on a coil-over setup or separate shocks & springs ?

Did you put JRI shocks on all 4 corners ... or just the rear?

Lastly, are your results coming from driving in Autox or big road courses?


Thanks, Ron Sutton

[Rod]

Matty, I think were both using the hyperco springs I ended up with 200 lb rears and 700 fronts, but hell you know that works I could change next week, I think that some of the lack of trail braking is also tire offsets, I noticed that scenario at Del Mar with the 10" rim on all for corners I had 0(zero) trail brake I switched to the smaller 8" inch 255 front wheel set up front and the turn in was quicker mid way in the turn allowing the rear to come around, instead of pushing through the corners

[Matt@BOS]

Rod, we are both using Hyperco springs, although I have a stray set of AFCO ones that Cris let me borrow to test (300lb) and a few sets of DSE branded ones on the shelf.

Ron, here is a chart from Speedway showing the bar rates. You will want to look at the 1-1/4" OD listings. Forgive me though, because I don't know what the length of the arm is. I think it is either 10" or 12."

The rear rates are:
Front Hole: 344 lb/in. Rear Hole: 402 lb/in.

Matt

[Ron Sutton]

Matt,

Did you put JRI shocks on all 4 corners ... or just the rear?

[Ron Sutton]

Matt,

Did you put JRI shocks on all 4 corners ... or just the rear?

[Ron Sutton]

For clarity sake, Matt … please read this and make sure I am interpreting your writings correctly. If not, copy, paste & edit into the next post.

----------------------------------------------------------------------------------------------

Your car is a 1969 Camaro with 454 LS7 (gen IV), T56 Magnum, 3.73 gears, 18x9 and 18x11.5 wheels with 275/35 F, 315/30 R tires. DSE subframe and quadralink. 3500lbs with a full tank, sans driver. 51/49 F/R weight distribution, with “close” cross weights” & narrower front than rear track width.

You have had basic 5 suspension set-ups:

#1
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 344#
Notes: The car had pretty good bite and turn in, but it was wearing the outside tires badly and it was the tire was being overloaded because it would skip, or hop once before taking a set.

#2
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I stiffened the rear, only to notice that I now had decent initial turn in with terrible mid corner push turning into transitional oversteer, making the car really loose putting power down.

#3
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with.

#4
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes gave me understeer that was most noticeable on turn in, but the functioning rear shocks greatly fixed traction issues as I used to start losing traction on auto crosses mid way through a straight since the rear springs wasn't being controlled.

#5
Front Springs: 700#
Front Sway Bar: 295#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes seemed to increase the amount of understeer into transitional oversteer that I experienced & ended up with a car that seemed to put power down exceptionally well but exhibited more understeer, especially applying power with slight steering input.


Do I have this correct ?


Ron Sutton

[Rod]

thread HI-JACK! hey Ron that logo is familiar, I meet you at Pleasanton didn't I? you should have went for a ride along, OK back to your regularly scheduled program

[Ron Sutton]

Yes, Rod. I stopped by & looked at your baby while I was at the last Pleasanton GG event. Checking to see if you were running same size tires on all 4 corners.

Sorry I didn't introduce myself. I was visiting Brianne & Mike Maier most of the day.

[Rod]

I'm liking this!! now were talking real, fun, stuff,

For clarity sake, Matt … please read this and make sure I am interpreting your writings correctly. If not, copy, paste & edit into the next post.

----------------------------------------------------------------------------------------------

Your car is a 1969 Camaro with 454 LS7 (gen IV), T56 Magnum, 3.73 gears, 18x9 and 18x11.5 wheels with 275/35 F, 315/30 R tires. DSE subframe and quadralink. 3500lbs with a full tank, sans driver. 51/49 F/R weight distribution, with “close” cross weights” & narrower front than rear track width.

You have had basic 5 suspension set-ups:

#1
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 344#
Notes: The car had pretty good bite and turn in, but it was wearing the outside tires badly and it was the tire was being overloaded because it would skip, or hop once before taking a set.

#2
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I stiffened the rear, only to notice that I now had decent initial turn in with terrible mid corner push turning into transitional oversteer, making the car really loose putting power down.

#3
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with.

#4
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes gave me understeer that was most noticeable on turn in, but the functioning rear shocks greatly fixed traction issues as I used to start losing traction on auto crosses mid way through a straight since the rear springs wasn't being controlled.

#5
Front Springs: 700#
Front Sway Bar: 295#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes seemed to increase the amount of understeer into transitional oversteer that I experienced & ended up with a car that seemed to put power down exceptionally well but exhibited more understeer, especially applying power with slight steering input.


Do I have this correct ?


Ron Sutton

[Tomswheels]

Matt, your suspension sounds like its working to eliminate too much roll, which is backwards. You want to ENCOURAGE roll, I included pics to show how it SHOULD look:



See how the front wheels appear to be pointed AWAY from the Apex, thats a great sign things are going well.



In this one we see the benefits of a 230(+) pound "driver"... Im getting the most grip possible from the outside edge of the left side tires.

[Tomswheels]

No comment needed, however, note the front left wheel / rear bumper angle. Almost perfect!

[Matt@BOS]

For clarity sake, Matt … please read this and make sure I am interpreting your writings correctly. If not, copy, paste & edit into the next post.

----------------------------------------------------------------------------------------------

Your car is a 1969 Camaro with 454 LS7 (gen IV), T56 Magnum, 3.73 gears, 18x9 and 18x11.5 wheels with 275/35 F, 315/30 R tires. DSE subframe and quadralink. 3500lbs with a full tank, sans driver. 51/49 F/R weight distribution, with “close” cross weights” & narrower front than rear track width.

You have had basic 5 suspension set-ups:

#1
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 344#
Notes: The car had pretty good bite and turn in, but it was wearing the outside tires badly and it was the tire was being overloaded because it would skip, or hop once before taking a set.

#2
Front Springs: 450#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I stiffened the rear, only to notice that I now had decent initial turn in with terrible mid corner push turning into transitional oversteer, making the car really loose putting power down.

#3
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 250#
Rear Sway Bar: 402#
Notes: I arrived at a set up I was reasonably happy with.

#4
Front Springs: 575#
Front Sway Bar: 447#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes gave me understeer that was most noticeable on turn in, but the functioning rear shocks greatly fixed traction issues as I used to start losing traction on auto crosses mid way through a straight since the rear springs wasn't being controlled.

#5
Front Springs: 700#
Front Sway Bar: 295#
Rear Springs: 275#
Rear Sway Bar: 402#
Additional Changes: Put JRI Shocks on the rear & Falken Tires all the way around
Notes: These changes seemed to increase the amount of understeer into transitional oversteer that I experienced & ended up with a car that seemed to put power down exceptionally well but exhibited more understeer, especially applying power with slight steering input.


Do I have this correct ?


Ron Sutton

Ron, that is 99 percent correct
On setup #4 I changed rear springs from 300lb to 275lb. JJ at JRI and I discussed between the 250-325lb rates I had on the shelf and put the 275lb springs on as a starting point since I was also swapping in rear shocks that had nitrogen, and well... functioned.

Oh, and before I forget, I do have JRI shocks on all four corners. They have low speed rebound adjustment, and a high speed damping adjuster. I can also add or drop pressure.

Thanks for your interest in sorting things out

Matt

[Matt@BOS]

Tom, I saw your Barracuda tearing up the Good Guys peanut course, and when I went for a ride I was afraid of capsizing. Perhaps that fear caused me to overcompensate by limiting weight transfer too much on my car.

Matt

[Tomswheels]

Understood Matt, im sure Ron will have a more intelligent observation, but have you ever tried a fairly stiff front setup with little (or even no) rear sway bar? This has worked with my (admttedly not as well balanced) cars in the past...

[Ron Sutton]

Ron, that is 99 percent correct
On setup #4 I changed rear springs from 300lb to 275lb. JJ at JRI and I discussed between the 250-325lb rates I had on the shelf and put the 275lb springs on as a starting point since I was also swapping in rear shocks that had nitrogen, and well... functioned.

Oh, and before I forget, I do have JRI shocks on all four corners. They have low speed rebound adjustment, and a high speed damping adjuster. I can also add or drop pressure.

Thanks for your interest in sorting things out

Matt

In which stages (1-5) did you have the 300# rear springs on ?

All JRI shocks come with a dyno sheet. Can you scan & post them please? We won't start with shock tuning, but we will finish there, as that is what shocks allow you to do ... fine tune & dial in a good spring & Anti-Roll Bar package.