Dan's message here is spot on for street driven cars. The perception of better "handling" will be there even if it really isn't the case from a track perspective.

 

Well, I may have confuse some people here because I am dealing with tw different cars here. One is my 1966 BB and the other is my 1965 SB.

I have a set of Avon’s on order but they are two months out. I will be ordering QA1 shocks shortly.

My SB car is in the body shop so I expect I will be making the changes to the BB first. Someone removed the rear sway bar from my BB car and I have a factory bar on order. The shocks will likely go on first or possibly the sway bar.

I have no plans to replace the front sway bar at this point on the SB car or to add a rear bar and will start with Avon’s and QA1 shocks after I his car is out of the body shop. I also plan to order a Blueprint 396 SB for this 1965 replacing the current original 300 h.p. engine so I have a lot on my plate in the near future.

 

Oh, I like that and I think you hit the nail on the head. "The perception of better handling". Folks in marketing are quick to tell ya that perception is reality. So if the user perceives the handling is better, then it must be. Even if the suspension change turned the car into an understeering pig.

 

My recollection of a quote from a NASCAR driver, long ago:

"Understeer is when the front end hits the wall. Oversteer is when the ***-end hits the wall."

Duke

 

My suggestion is to get the suspension components (bars) back to stock. The OE setup is the best baseline to start from. Get the Avons and shocks installed and get the alignment dialed in, Then do plenty of test driving over your normal roads to dial in the adjustable shocks.

The last thing to do is start swapping bars, and you need to understand what they do. Sure, they reduce roll, but they also have a big effect on the cars understeer/oversteer balance, which can vary widely among drivers. I recall long ago a Formula One driver had to use a spare car in practice that was set up for the other driver, and the first driver declared the car "undriveable".

I''ll add that on base suspension small blocks that can snap into oversteer at the limit, it's a good idea to install hard urethane bushings on the front bar links to the control arm. The rubber bushings can compress at high roll angles causing loss of bar effectiveness which effectively transfers roll stiffness to the rear, which is why they can suddenly snap into oversteer at the limit.

I don't have enough experience driving big blocks at eight or nine tenths, but it probably wouldn't be a bad idea to do the same. Public roads can be unpredictable, so its best to have a car with limit understeer and one that doesn't exhibit trailing throttle oversteer that can spin you into the weeds, a guard rail, or over over a cliff. Early 911s are famous for this trait due to both the rear weight bias and the toe and camber change of the semi-trailing arm rear suspension. The C2/3 three link rear suspension has similar unfavorable characteristics, which is one reason why they are very sensitive to rear toe and static rear toe must be in the proper range to avoid handling instability.

There's a reason why modern very high performance production and purpose built race cars have either a five link rear suspensions or upper and lower A-arms, which are the equivalent of four links plus a toe control link.

Duke

 

My take on this is that some folks perceive under steer as being better handling because it feels “safer” when they are at the limits of what they have experienced. At that point backing off the throttle is the instinctive reaction and understeer feels like the car is more predictable and therefore is thought to be better handling.

Comfort, predictability at the limits of one’s experience, and perceived safety are taken as better handling over actual cornering speeds and exit velocity. How many folks accelerate through a corner in street driving?

 

Alignment dial in? Can someone give me the specs for this regarding this thread.

 

Recommended alignment specs, both "touring" and '"sport" have been posted many times by me and JohnZ.

Duke

 

Um, I know a fellow who lives in the Sierra who does exactly that.

 

I always accelerate through corners. It's fun, especially 180 degree freeway onramps. I might enter a little conservative especially if I can't see the exit, but once I can see that the coast is clear I add throttle and take it up close to the limit.

Duke

 

 

Same here. You know those ramps are banked correctly. If I am on an unknown to me road I am careful not to accelerate in a hard turn for fear of the turn not being banked the correct way.

 

I have recommended your spreadsheets with links as they have evolved over in C3. It is a great tool to model and compare setups.

For the OP:

Know what you have in each car for springs, bars, and bushings, along with front/rear weight, and model them in the spreadsheet (Weight and Springs is the far left tab starting page).

On a C2 the inboard rear camber strut bracket produces a high rear roll center (promoting rear stiffness and snap oversteer). The C2 bracket also produces a less than ideal rear tire camber curve for anything other than the skinny 1963 tire profile (it moves a wide tire edge to edge as the suspension cycles). The lower C3 bracket produces a more stable camber curve to keep wider tires planted in fast cornering, and lowers the rear roll center for a more compliant ride. The C3 bracket also allows for slightly more rear roll and that shifts more load on the front bar & bushings to add more feedback with turn in understeer feel, in addition to reducing that snap oversteer concern (softer ride in a straight line and less surprise drama in corners). The C3 bracket, and lower aftermarket brackets, improve the handleing (model changes on the Spring Rate tab page).

Once the front and rear roll centers are set, get a performance alignment (-1* camber front, -0.5* rear camber, caster to your preference, and toe-in for your use, modeled on the Camber Change and Bump Steer tab pages). These settings will not change unless you change springs and ride height, so the tire angles and camber gain will remain consistent as you test bar and bar bushing changes (Sway Bar tab page).

If you swap springs, like the F41 springs that ride about 1" lower in front, the alignment should be adjusted for the new ride height (the ride height model adjustment is on the Roll Center tab page).

The Sway Bar tab page model assumes stock GM 6.25'/13.5" bar arm lengths. If you use an adjustable arm bar link mount (like old Rancho bars) or bars with a different pillow block to end link lever arm length, you need to change the sheet's "arm" values.

With modeling the difference in handling is quantified in the Roll Rate, from an ultra firm ride with understeer (C3 bracket F41 SB with 1 1/8" front & 7/8' rear Gymkhana bars @80% fr RR), to soft ride with potential snap oversteer (stock C2 bracket SB and no bars & base springs @45% fr RR).

Like any tool you need to test options on the pages and with your butt feel in the wild. Pick a desired roll rate & Fr/R balance, and then select the bracket and sway bars to fit and test.

 

It is very difficult to change just one item on your suspension without improving or ruining it's balance. My bb car should roll 3 degrees stock. I do not want that much roll. My old pro-solo car I had roll 1.5 degrees. This one I want somewhere in the middle. I am going with 480 front springs, a 330 rear composite, front 1-1/8 bar, and 9/16 bb rear bar. That should make it roll where I want, more like a new car, and give me a similar handling balance to stock. The ride quality is 80% based on shock valving, that's why I have QA1 adjustables. That's last. I tuned my solo car's rear bar 100's of times to adjust the handling balance. And I raced 28 times a year. I began with a lot of rear bar and a very neutral car. I finally settled on more understeer than the factory had, because I learned to used full power from that LT-1 thru most of the turn. That was several seconds faster than a neutral car. And yes powering thru turns is fun, if you have enough power, you can walk the tail out any amount you want. I actually had to add more rear bar / oversteer to the car for the road course. I just didn't have enough power in 3rd to walk the tail out. If you are more gentle with the car, or have less power, you would also want more rear oversteer than I did. On the C3 LS6 I will just juggle bar size up & down fr & rr until I get it where I like it. The numbers say it's got a decent balanced setup but I am still building the car. I just wish I had an adjustable rear bar. Might be worth making one even. I did before.
I am glad to hear some feedback from some that are using the spreadsheet to model setups. You can change a few things at a time, and not ruin the balance, if you keep the fr roll % the same. Somewhere around 72. Look what GM did to the gymkhana cars 78% front, and less power. Too much understeer.

 

If you've never been on the road (or track) before you need to take it easy and "read" the road. Decreasing radius corners and off camber turns, especially at the exit can be real pucker experiences. Get to know the road or track and then figure out where you need to be a bit conservative and where you can really let it hang out.

Every track has "pucker" turn. At Riverside it was Turn 2 and the big Willow Springs track is Turn 9. I always thought I could do Turn 2 flat in fifth at a bit over 100 MPH, in the Cosworth Vega, but was never able to bring myself to it. I didn't brake but I did lift briefly before turning in. It was flat and went around a berm. You couldn't see the exit. I always thought about the Gile Villeneuve - Clay Regazoni story that was written up in one of the car magazines way back when.

Giles was the new guy and there was a corner at Ferrari's Fiorano test track he was having trouble with. He always lifted. Clay said, nah, you can do it flat. So finally on a lap when Giles was approaching the corner he placed his left foot over his right foot to lock the throttle pedal full on and did the corner flat. I guess my ***** weren't big enough to pull that stunt. The link to the You-tube clip is from circa 1988. I was running the best road tires from the late seventies/early eighties, Phoenix Stahlflex 3011s, and unfortunately I didn't get around to installing a real set of DOT racing tires until after Riverside closed in the late eighties or early nineties, I think they would have allowed me to do it flat with confidence. Turn 2 was critical to a good lap tijme because it determined your speed through the esses, especially in a low to moderate powered car where you were scubbing off speed a good part of the way, especially Turn 2.

I'll let you guys figure out which is Turn 2 from the following clip. This was a track time event hosted by the local Ferrari and Pantera clubs. The rule were that if a car caught you in a corner he was faster, so let him pass on the next straight even if you can out accelerate him. The a-hole in the 911 didn't believe in following the rules, and I cou'dn't get the corner workers or start/finish stewards to pay attention to what was going on and black flag the SOB.


The two top related videos on the right are me and a buddy drag racing our CVs at the old Brotherhood raceway at the LA harbor back in the early nineties and the next on is video from my incar camera and the supercharged small block Mustang that overcooked it trying to pass me going into Turn 7A.

Duke

 

Cool video. Yeah, that joker should have let you pass on the straight since you were up his *** on all the turns.

 

are you saying that the C3 brackets are a bolt in change you can make to a C2 without other modifications?

 

Yes. Bolt in and reset rear camber.

 

Would you happen to have the part numbers and source of where to buy them?

 

Hemi - I’ve got one if you’re interested? I’ll post a picture of the difference …. the later model is flatter, in other words the differential end rod mounts are lower. I also have a thin 3/8” aluminum spacer, that goes under it to take it even a touch lower, I think I got it from Dick Gullstrand years ago (in the 70’s), it’s brand new.