Can someone critique my set-up

[19,69camaro]

I am trying to design a front suspension for my Camaro using c5 front suspension. It will be a full frame car so I won't be relying on any stock suspension points. Tires are 315mm with 2.5" offset on all 4 corners. I am open to rolling the fenders but will not be adding flares. That pretty much dictates track width so I added to the KPI to try and reduce the scrub radius as much as possible. The engine is also set back so rack position is not a problem.

My goal for this car at this time is to make it completely adjustable and set it up so that it is very neutral and forgiving so that as I progress as a driver I can adjust the car to be more responsive.



Let me know what you guys think. Also if you could give me any pointers on what I should be looking for dynamically. Right now I am basing this off a high travel/low roll 2.8" dive 1.4 deg. roll and 15 deg. steering angle

[Motorcitydak]

Are you going to keep that 9 degrees of caster angle? With tires that wide I really hope you will have power steering. I am using 6.5 and manual steering, with the car not moving you seriously cannot move the wheel. Also with the c5/c6 knuckle I was able to get a scrub radius of 0 but I forget the measurements of my front wheel

[19,69camaro]

Most definitely going with power steering since it’s going to be a street car running 315’s in the front. Plus I want the high speed stability and dynamic camber gain you benefit from with a higher caster to KPI ratio.

Side not for anyone looking for a bolt in steering rack for c5 based suspension you can use a 4th gen Camaro unit. Inner pivots are about 28” and vette outer tie rods screw right on you don’t need some custom steering arms. Of course for this to all work the engine needs to be set back around 6”.

[Ron Sutton]

How are you increasing the KPI to 10.07° ?

[19,69camaro]

Ron, by moving the upper ball joint and UCA mounts inboard. Is that wrong? I was under the impression that it is a calculated value by drawing a line through the UBJ and LBJ.

[Rod]

lets get our suspension on

[Motorcitydak]

It is (as viewed from the front end of the car) but you cannot move the ball joints like that and not also tilt the knuckle and therefore static camber. You are stuck with what you get from the factory as far as KPI (king pin inclination, same thing as king pin angle)

Also the c5 stuff is good but no where near ideal really for anything. Yes it is a SLA but the upper arm is still too long. I ended up just building my own arms and am going to be getting 1.0 degree of camber per inch of travel. If you are running minimal travel, you would like to see quick changes

[Ron Sutton]

It is (as viewed from the front end of the car) but you cannot move the ball joints like that and not also tilt the knuckle and therefore static camber. You are stuck with what you get from the factory as far as KPI (king pin inclination, same thing as king pin angle)

Also the c5 stuff is good but no where near ideal really for anything. Yes it is a SLA but the upper arm is still too long. I ended up just building my own arms and am going to be getting 1.0 degree of camber per inch of travel. If you are running minimal travel, you would like to see quick changes

Hi Steve,

You are on track with the camber gain goals if you're running a low travel set-up. If we gain 1.0° camber per inch of suspension compression .... and travel the front end 1" during dive (under braking) then you'll gain 1° of camber. Frankly, for a low travel set-up around 1" ... you could benefit from even more camber gain.

One thing to take into account, is camber gain is NOT linear in most set-ups. When the software is telling you the camber gain is xxx per inch ... what it is really saying is it is xxx for the first inch. What happens is ... the shorter UCA angle changes more rapidly in dive than the longer LCA angles does ... creating progressive camber change. So a front end with 1.0° camber gain for the first inch of suspension compression ... may see 1.25° camber gain the 2nd inch ... and 1.40° camber gain the 3rd inch ... for a total of 3.65° total camber gain for 3" of travel.


For guys running a high travel set-up, that much camber gain won't be optimum. This is one of those situations where you want to make sure the whole set-up package is harmonious & works together. For Aldin's setup ... targeting 2.8" of travel in dive ... he would end up with too much camber. I can't tell Aldin ... or anyone ... how much camber they need exactly, because it is only one of several factors needed to achieve optimum contact patch on the front tires.

The factors that matter are:
Spindle KPI
Static camber
Camber gain
Static caster
Caster gain (affected by steering angle)
Tire sidewall deflection under load
Side load G-forces (determined by tire & track grip, car weight & how hard the driver pushes the car)
Dynamic roll angle of the car (front end)

[19,69camaro]

I made a mistake and just moved the UBJ location around to see how it would change the scrub radius. I want to start with -.75deg of camber in the front but performance trends as far as I know doesn't change any geometry when you input your desired camber. After calculating it out it looks like if I move the UBJ 0.08" inboard that would equate to -.75 deg camber.

I would like to run higher travel and higher initial ride height so that much camber gain wouldn't be desirable.

[Ron Sutton]

I made a mistake and just moved the UBJ location around to see how it would change the scrub radius. I want to start with -.75deg of camber in the front but performance trends as far as I know doesn't change any geometry when you input your desired camber. After calculating it out it looks like if I move the UBJ 0.08" inboard that would equate to -.75 deg camber.

I would like to run higher travel and higher initial ride height so that much camber gain wouldn't be desirable.

You will want to set the LBJ distance out from the chassis centerline where it really is ... then:
* Adjust the UBJ distance out from the chassis centerline to achieve 8.66° (C5 KPI) with zero camber
* Adjust the inner pivot point of the UCAs distance out from the chassis centerline to match the actual length of the UCAs.
* Later ... after your set-up is all done ... then add your desired camber using the PT software shimming option.
* Recheck what it did to your geometry ... and see if you're ok or need to tweak on it.
* Work out your bumpsteer after shimming.

Best wishes.


P.S. IMHO, your roll center below ground by 3"+ will not be optimum. I'd shoot for ground level. While you're at it ... again IMHO ... you need to increase your anti-dive & caster gain.

[19,69camaro]

hopefully this is a little better

[Ron Sutton]

Roll center is better. Camber gain, caster gain & anti-dive all look low.

Go into preferences, to the Definitions tab & set your "Dive for gain" calcs to 2.8 ... same as your dive. You're probably going to want 2-2.5° camber gain, .75-1.25 caster gain & 35-40% anti-dive.

[19,69camaro]

Ron, Thank you so much for you input I have learned a great deal so far reading your posts.

I was trying to not go over 3.5 degrees of camber in dive, roll and with a 15 deg steering angle based off of what I read in other posts. The hard part for me knowing what to look for. For instance what is the ideal camber for a maximum loaded tire.

[Ron Sutton]

Ron, Thank you so much for you input I have learned a great deal so far reading your posts.

I was trying to not go over 3.5 degrees of camber in dive, roll and with a 15 deg steering angle based off of what I read in other posts. The hard part for me knowing what to look for. For instance what is the ideal camber for a maximum loaded tire.

I wish I could just give you an answer, but there are variables. Car roll angle plays a role. If the car roll angle is 2° ... it needs 1° more dynamic camber than a car with 1° roll angle.

Tire sidewall width, rim to tread width ratio & tire pressure all play a role too.
If we ran 9" tread width tires on 8" rims, we end up with lower tire pressure to achieve full contact patch ... and the sidewall will roll under more during hard cornering ... requiring more dynamic camber.
If we run the same 9" tread width tires on 10" rims, we end up with higher tire pressure to achieve full contact patch ... and the sidewall will roll under less during hard cornering ... requiring less dynamic camber.
Sidewall stiffness plays a role too. So generally speaking, 35 series tires will have more tire sidewall roll under than 30 series tires ... all else being equal. But sidewall stiffness varies from tire brand to tire brand (and even in the same tire brand of different tire model designs).

My suggestion is to shoot for around 3°-3.25° total camber (static & gain combined) start with 10.5° total caster (static & gain combined) and go run it. Use tire temps to guide you on if you need more or less of either caster or camber.

Best wishes.

[rustomatic]

This is first-rate nerdism! If only my walnut weren't blown out from taking a huge test last night . . . Ron Sutton: human geometry computer for the win!

[Aficionado]

This is first-rate nerdism! If only my walnut weren't blown out from taking a huge test last night . . . Ron Sutton: human geometry computer for the win!

It makes me feel better knowing I'm not the only person who felt that way....I need to be doing more homework!!