C2 vs C3 rear strut rod bracket differences
10-18-2014, 06:25 PM
#21
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10-18-2014, 07:48 PM
#23
Team Owner
I grabbed that picture
Out of the Herb Adams book, and only posted it up for the rods and generally for the parallelness of the lower and upper, but yes that car Adams used, looks like the outer is higher! Thus even the known experts set them up glitched a hair! This is a photo, so the illusion could be caused by the lense curving the photo and then I reshot it thru another camera!
Also I will have to work through the camber curves (parallel to angled), but the way I have spring and shocked cars- I have race car minimum movement and these are pivoting on heims.
because you jerry have a race car, I assume we haven't steered to generally what is best for a general performance Corvette (split some street use and maybe some track time).
Also I will have to work through the camber curves (parallel to angled), but the way I have spring and shocked cars- I have race car minimum movement and these are pivoting on heims.
because you jerry have a race car, I assume we haven't steered to generally what is best for a general performance Corvette (split some street use and maybe some track time).
Last edited by TCracingCA; 10-18-2014 at 07:57 PM.
10-18-2014, 07:58 PM
#24
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10-18-2014, 08:14 PM
#25
Team Owner
Jim
Does the camber increase or decrease?
I am grabbing the Smith bible! I know I shoot for contact patch tracking and get that from the heims.
I know you work with this more often than most! i found my setup like 20 years agbo and just try to keep it set that way depending on what I am doing!
We have rod and halfshaft arcs of travel and what it does to camber!
We have set camber by setup of the strut rod length!
We have upright movement either by rubber deflection or heim rotation that can change camber!
At least we see that going more parallel on the upper and lower lowers roll center?
And i can guarantee my halfshaft are """not""" set up higher on the outboard!
I am grabbing the Smith bible! I know I shoot for contact patch tracking and get that from the heims.I know you work with this more often than most! i found my setup like 20 years agbo and just try to keep it set that way depending on what I am doing!
We have rod and halfshaft arcs of travel and what it does to camber!
We have set camber by setup of the strut rod length!
We have upright movement either by rubber deflection or heim rotation that can change camber!
At least we see that going more parallel on the upper and lower lowers roll center?
And i can guarantee my halfshaft are """not""" set up higher on the outboard!
Last edited by TCracingCA; 10-18-2014 at 08:28 PM. Reason: My ""not""
10-18-2014, 08:41 PM
#26
Team Owner
Ok we do have to analyze which direction the ground is going!
I will have to dig out the Smith book still, but I would say dropping 1" would increase camber movement in BUMP! to go more technical, because guys, we are talking two potential directions and not just the ideal model of high corning force and suspension arc on a flat track to get better handling, yes focus on that is the primary, but other things are happening in the real world like banking or off camber and then we have to consider the opposite tire especially and just not camber thoughts on each wheel but both left or right.
Therefore better phasing the question would be about the arc and my brain is starting to hurt! My NASCAR Crew Chief brother loves this stuff, and not my favorite topic. Going more parallel vice angle effect on arc?
Therefore better phasing the question would be about the arc and my brain is starting to hurt! My NASCAR Crew Chief brother loves this stuff, and not my favorite topic. Going more parallel vice angle effect on arc?
Last edited by TCracingCA; 10-18-2014 at 08:54 PM.
10-18-2014, 09:04 PM
#27
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If the distance between the inboard camber rod mount point and the center line of the half-shaft U-joint above it is less than the comparable distance at the outboard ends, there will be camber gain (more negative or less positive, depending on the initial setting) in bump.
10-18-2014, 09:04 PM
#28
The bracket for 63-68 is 1" higher mounting the inner camber rods higher, thus changing to the later bracket drops the geometry 1" lessening the angle, but many have found the geometry angle even better with one more inch of drop by different methods like a camber block or designing their own bracket unit like Herb adams did and the Toms Differential, and Global west, Greenwood, units etc who further changed the bracket and actually Guldstrand never developed a custom bracketl . Basically making them (camber rods) parallel to the attachment on the bearing hub bracket for the camber rod attachment. Therefore as the wheel moves up and down, you would have less camber change basically starting at 0 degrees to the attachment height level. The bracket itself doesn't change roll center essentially on it's own, but the better camber rod angle in conjunction with setting height with the spring bolts and changing the trailing arm geometry could lead to the ability through adjustment to change roll center, unless you have fixed length strut rods (camber rods). You are also trying to get the angle or better put "plane of the upper link of the suspension (the halfshafts parallel) to the camber rods. Therefore gaining better contol over the range of travel bettering the camber curve during suspension movement. I hope I got that said OK, because I was trying to write it as simplified as possible! Also you can help or hurt corner weighting with the spring bolt adjustments while aligning everything. I do think leveling the halfshafts is crucial, not only for coupling strength, but that essentially being an upper a-arm, it is not good for something coming in at an angle and moving differently from an angle with the wheel uprights. You want the arc of everything to move in unison as much as possible to limit camber changes through suspension changes caused by the tire tracking unless you are doing something where you are trying to set more camber based on a track situation induced by cornering forces! For tonight, I am not going to try to explain raising the diff by mod of the crossmember by compression of the donuts or shaving the donuts or elimination of thde donuts. Thus you raise that the halfshaft angle changes again and now you have to go outboard to the upright to adjust those, while reworrying about the camber rods. For the true benefit of the brackets we are discussing it is best to run adjustable heims for locking everything because the stock rubber has deflection and the cam setups don't help in high cornering loads! Alot to think about back there!
10-18-2014, 09:07 PM
#29
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Would lowering the bracket on a street driven car be beneficial? I have a 66 convertible that is lowered and has heim joint camber rods. If I lowered the bracket 2" my camber rods would be exactly parallel with my half shafts. I have under car exhaust and my pipes would then have to go between the camber rods and my fiberglass spring-doable with a custom exhaust system , but would that be worth the effort?
10-18-2014, 09:17 PM
#30
Doesn't the camber change when I go into a corner and hit a bump also change the toe? It seems that by making the half shafts and strut rods parallel would help with this toe change --or am I just of base ? Right now my lowered cars half shafts are parallel with the ground at ride height.
10-18-2014, 09:17 PM
#31
Team Owner
Thanks Jim
If the distance between the inboard camber rod mount point and the center line of the half-shaft U-joint above it is less than the comparable distance at the outboard ends, there will be camber gain (more negative or less positive, depending on the initial setting) in bump.
Smile!
Also my Father loves at 81 the exposure I have given his car, so here is proof at least his dinky (the 3" look small to me!) halfshafts are ""not"" higher on the outer axles. I have to talk to him about the vintage 1970 chrome tape also!
My compter keeps as I type jumping what I type to a different or prior location in what I have typed. It keeps messing with my train of thought. Anyone know how to fix that?.
I am taking a break! Be back!
Last edited by TCracingCA; 10-18-2014 at 09:20 PM.
10-18-2014, 09:26 PM
#32
Team Owner
Also
We are a family of mutant 8 leaf springs! Don't ask, but I have explained that in the past. It's an F-41 pack with a Guld strand short on the bottom of that and the bottom leaf of the F-41 modified home shortened! thus hopefully falls between an F-41 7 leaf and a Daytona, but I feel more daytona level.
10-19-2014, 08:05 AM
#33
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You want some camber change during body roll.
Think about it this way.... you want the tire to remain vertical as the body rolls. The only way to achieve this is to gain some negative camber when the suspension compresses.
If there is no camber change, then the inside edge of the tire will begin to lift as the tire leans over with body lean. Not good..... loss of grip will be the result.
You'd probably rather not have toe change during body roll.
But if you must have toe change, it's better to have an increase in toe-in than an increase in toe-out.
Increasing toe-out causes the sensation of roll oversteer and it's discomforting..... Turn the steering wheel, body rolls, rear end feels as if it's coming around, correct steering, vehicle doesn't turn as much as wanted, turn the steering wheel more, .....[repeat]
Toe-in during cornering causes roll understeer and is a stable, comfortable situation.
Unfortunately, the trailing arm design of the C2s and C3s can produce roll oversteer. It can also produce roll understeer. And, just to make things interesting, it can transition from roll understeer to roll oversteer. The point at which each of these situations occur is affected by the amount of toe-in dialed into the rear suspension.
When the static position of the outboard u-joint of the half shaft is below the inboard u-joint, any suspension compression up to the point that the two u-joints are at the same elevation will tend to cause roll understeer.
Conversely, if the static position of the two u-joints is at the same elevation above ground, any suspension compression will tend to cause roll oversteer.
Combining, it's easy to see that if the static position of the u-joints favors roll understeer but the suspension compresses sufficiently to place the inboard u-joint lower, there can be a transition from roll understeer to roll oversteer.
It seems that by making the half shafts and strut rods parallel would help with this toe change --or am I just of base ?
Right now my lowered cars half shafts are parallel with the ground at ride height.
Jim
Last edited by jim lockwood; 10-19-2014 at 08:47 AM.
10-19-2014, 01:49 PM
#34
Yes, both camber and toe change during body roll or if a wheel hits a bump. It's not all bad, though.
You want some camber change during body roll.
Think about it this way.... you want the tire to remain vertical as the body rolls. The only way to achieve this is to gain some negative camber when the suspension compresses.
If there is no camber change, then the inside edge of the tire will begin to lift as the tire leans over with body lean. Not good..... loss of grip will be the result.
You'd probably rather not have toe change during body roll.
But if you must have toe change, it's better to have an increase in toe-in than an increase in toe-out.
Increasing toe-out causes the sensation of roll oversteer and it's discomforting..... Turn the steering wheel, body rolls, rear end feels as if it's coming around, correct steering, vehicle doesn't turn as much as wanted, turn the steering wheel more, .....[repeat]
Toe-in during cornering causes roll understeer and is a stable, comfortable situation.
Unfortunately, the trailing arm design of the C2s and C3s can produce roll oversteer. It can also produce roll understeer. And, just to make things interesting, it can transition from roll understeer to roll oversteer. The point at which each of these situations occur is affected by the amount of toe-in dialed into the rear suspension.
When the static position of the outboard u-joint of the half shaft is below the inboard u-joint, any suspension compression up to the point that the two u-joints are at the same elevation will tend to cause roll understeer.
Conversely, if the static position of the two u-joints is at the same elevation above ground, any suspension compression will tend to cause roll oversteer.
Combining, it's easy to see that if the static position of the u-joints favors roll understeer but the suspension compresses sufficiently to place the inboard u-joint lower, there can be a transition from roll understeer to roll oversteer.
No effect on toe. See above.
Your rear suspension is set up to favor roll oversteer. You can partially compensate for this with an alignment which has a toe-in condition at ride height.
Jim
You want some camber change during body roll.
Think about it this way.... you want the tire to remain vertical as the body rolls. The only way to achieve this is to gain some negative camber when the suspension compresses.
If there is no camber change, then the inside edge of the tire will begin to lift as the tire leans over with body lean. Not good..... loss of grip will be the result.
You'd probably rather not have toe change during body roll.
But if you must have toe change, it's better to have an increase in toe-in than an increase in toe-out.
Increasing toe-out causes the sensation of roll oversteer and it's discomforting..... Turn the steering wheel, body rolls, rear end feels as if it's coming around, correct steering, vehicle doesn't turn as much as wanted, turn the steering wheel more, .....[repeat]
Toe-in during cornering causes roll understeer and is a stable, comfortable situation.
Unfortunately, the trailing arm design of the C2s and C3s can produce roll oversteer. It can also produce roll understeer. And, just to make things interesting, it can transition from roll understeer to roll oversteer. The point at which each of these situations occur is affected by the amount of toe-in dialed into the rear suspension.
When the static position of the outboard u-joint of the half shaft is below the inboard u-joint, any suspension compression up to the point that the two u-joints are at the same elevation will tend to cause roll understeer.
Conversely, if the static position of the two u-joints is at the same elevation above ground, any suspension compression will tend to cause roll oversteer.
Combining, it's easy to see that if the static position of the u-joints favors roll understeer but the suspension compresses sufficiently to place the inboard u-joint lower, there can be a transition from roll understeer to roll oversteer.
No effect on toe. See above.
Your rear suspension is set up to favor roll oversteer. You can partially compensate for this with an alignment which has a toe-in condition at ride height.
Jim
10-19-2014, 04:09 PM
#35
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10-19-2014, 05:25 PM
#36
Burning Brakes
Thread Starter
Be very careful when setting toe at rear to set toe in from center of rear suspension. Do not just set toe boards on the wheels and measure total toe. i have made the error of having the correct toe but it was mostly on one side so when the suspension went into compression I had on wheel in toe in and one in toe out. Not a good feeling.
10-19-2014, 06:42 PM
#37
Burning Brakes
Gulstrand strut rod and camber backet on my 65 street car. Also has Van Steel offset trailing arms and QA 1 coil overs. Rides and handles great.
10-20-2014, 04:49 PM
#38
Team Owner
Back from Weekend break!
I am glad the toe question was covered, because I will not engage in one of those if any rubber is still employed in the suspensions, or for the rear you are using shims still!
I think most guys here that helped or chatted, will understand that!
I think most guys here that helped or chatted, will understand that!
10-20-2014, 04:54 PM
#39
Team Owner
Funny! But you are pretty knowledgeable!
And I just try to know just enough, so I don't kill myself in my beloved Corvettes!
10-20-2014, 04:54 PM
#40
Burning Brakes
Thread Starter
Just to keep the thought juices flowing. What do you folks feel the effect of half shaft angle and camber rod angle have on roll center for the rear. Static and dynamic. 