IFS Technology - No Limit Sniper IFS

[Rod]

I had a chance to take these today, so I thought I would share this with you. This is a 69 Camaro with a stock sub (modified) and the usual aftermarket upgrades. With the current geometry and wheel and tire combo there is appx 3 1/4" of scrub radius. So how does that affect the suspension? Well, take a look. As the wheel turns in or out, the contact patch of the tire is being pushed forward, or pulled back. First, this action is at a different rate than the tire is rolling and forces the tire to 'drag' against the pavement, and makes the contact patch "un-happy" - loss of traction. Second, from the pictures it is easy to see that the wheelbase is changing. The outside tire is moving forward, making the wheelbase longer. On the inside of the car, the wheelbase is getting shorter. This changing of the wheelbase takes mechanical load off of the outside front tire and allows the tire to 'skip' on the pavement. or, "Push".

Looking at these pictures helps to understand why Scrub Radius is so important to a true performance suspension design.

ARRGGGG!!! its all over the place!

[RobNoLimit]

We do a flex test on all chassis and subframe designs. This allows us to compare our chassis and subs with the OE units and with others in the marketplace. Our test is pretty simple, and we use this as a standard, so it's always done the same way.

When you think about the subframe it really does three jobs. 1.- It locates all of the front suspension and steering components as well as transfers all suspension travel and brake forces to the rest of the car. 2.- It holds the motor and trans in place, and transfers the torque forces from the drive train to the rest of the car. and 3.- The subframe holds the front of the car in place with the rest of the car. If the subframe is flexing, it can change many factors in the car. Some of these are, effective spring rate, total roll stiffness, sway bar rate, steering position, Engine torque response..... These are all performance related. Sub flex can also change the alignment of the front sheet metal, hood, and front sheet metal. This flexing of the sheet metal can also relate to the driver experience as it can produce noise and rattles. The OE (Chevrolet) new that the sub would flex, so they mounted it with rubber bushings. Now, we like to use harder urethane or solid mounts to eliminate the flex, but over a long period (not too long really) these harder mounts will put more force into the uni-body mount pads, and start to destroy them. - I have repaired many. As part of the subframe design plan, we wanted to reduce the flex. More performance, better driver feel and road manners, and a car that won't self destruct. We cant stop the flex, but we can reduce it.

As I said our test is simple. We hold the sub at three points, and then apply a load. The load is in two steps. First is a 10 ft section of 2" x 3" .120 wall tubing (the arm). This alone weighs 40 lbs and will put appx 200 lbs of force on the sub to twist. Then we hang 100lbs. (bucket full of steel scrap) on the end of the arm. This is appx 1000 lbs of load force. (I know, this is not the true number through the centerline. No reason to write in. This is for comparison only. We're not NASA)

[RobNoLimit]

When we do this, we measure in three sets, both in degrees and in 'fall' in inches. The first is to check the sub itself, in degrees, swapping the support post from side to side. (this shows sub flex alone) Then when the arm is on, we check in degrees and inches. Lastly, with the 100 lb weight, we check in degrees and inches on 'fall'.

Results
O.E. Sub
Sub flex empty L/R = 0.90 degrees (neutral @ .50 degrees)
With arm only = 1.10 degrees Bar end = 48.5"
With 100lbs. = 4.50 degrees Bar end = 38.25" (10.25" of fall)

Sniper Sub
Sub Flex empty L/R = .060 degrees (neutral @ .30 degrees)
With arm only = .70 degrees Bar end = 49.25"
With 100lbs. = 2.80 degrees Bar end = 43.5" (5.75" of fall)

While we have tested others, it's not for us say the results. You can try these out on any sub and duplicate the test procedure for yourself. This flex may not bother a drag racer, where the weight is a bigger factor, but for a Pro-Touring track ready driver, it may make all the difference.

[RobNoLimit]

We have been asked about the weight. While there are some factors in comparing, like brake steering and shock choice, here is a basic rundown. The O.E. components we weighed were from a stock 68 with disc brakes. I have also make some notes as to sprung-or-unsprung weight, and rotating weight.

O.E.
Subframe with motor mounts and trans crossmember ....... 125 ....... sprung
Steering box, pitman arm and center link ....... 34 ....... sprung
Sway bar 3/4" ....... 13 ....... 3/4 sprung
Tie rods ....... 7 lbs each ....... 14 ....... 1/2 spung
UCA ....... 9.4 lbs each ....... 18.8 ....... 1/2 sprung
LCA ....... 13.5 each ....... 27 ....... 1/2 sprung
Spring ....... 14 each ....... 28 ....... 1/2 sprung
shock ....... 2.2 each ....... 4.4 ....... 1/2 sprung
Spindle with steering arm ....... 16.6 each ....... 33.2 ....... un-sprung
Brake assembly ....... 23 each ....... 46 ....... unsprung-rotating
Total wt = 343.4 lbs, with 128.55lbs of un-sprung wt, 46 lbs of rotating wt.

Sniper IFS
Subframe with motor mounts and trans crossmember ....... 152 ....... sprung
Rack and pinion ....... 14 ....... sprung
Sway bar ....... 1 1/4" splined w/steel arm ....... 18.5 ....... 3/4 sprung
Tie rods ....... 1.2 lbs each ....... 2.4 ....... 1/2 sprung
UCA ....... 7.1 lbs each ....... 14.2 ....... 1/2 sprung
LCA ....... 10.5 each ....... 21 ....... 1/2 sprung
Coil-over ....... 6.1 each ....... 12.2....... 1/2 sprung
Spindle with steering arm ....... 9.3 each ....... 18.6 ....... un-sprung
Hub and brake assembly - Baer 14" 6p ....... 18.1 each ....... 36.2 ....... un-sprung, rotating
Total wt = 288.9. Unsprung wt = 84.3 with 36.2 lbs rotating.

While the subframe itself is heavier, the total assembly is lighter. More importantly is the reduction of unsprung weight and rotating weight. Yes, the percentage of unsprung and rotating weight is not perfect. The UCA and LCA are heavier to the 'sprung' side due to the cross shaft and bushings. The coil-overs are mounted 'can-up' to reduce unsprung wt as well. Also the caliper should be sorted out of the 'rotating' wt number. But you get the idea. Dare to compare!

[eric1967]

Looks good Rob. I like those long lower arms. This should be a killer setup.

[another69]

I am very excited about another subframe in the market and especially the direction that this one is headed. I always assumed that the subframe was the strongest part of 1st gens but it sounds like it is actually weaker (or at least less stiff) than the unibody?

I like the idea of a wider track width. How much wider than stock is this one?

[RobNoLimit]

I am very excited about another subframe in the market and especially the direction that this one is headed. I always assumed that the subframe was the strongest part of 1st gens but it sounds like it is actually weaker (or at least less stiff) than the unibody?

I like the idea of a wider track width. How much wider than stock is this one?

I'm not sure it's weaker, but the flex can be damaging. OE track was 58.7" (this is the hub face to hub face, or WMS/WMS) Our IFS is 60". 1.3" wider, or .65" per side.

[RobNoLimit]

At last weekend's USCA event in Texas, Keith (Velocity's owner) was there to compete in the car for the first time. The weather was good and they all got plenty of runs and lap time. This car has been sitting for about six years, and we addressed mostly suspension upgrades so far. Here is a run down to give you an idea about the car.
This car was built to showcase ridetech Shockwaves and air suspension. We removed the Air components and replaced them with ridetech coil-overs. The rear suspension is a RideTech 4-bar. 9" Ford with Baer brakes. - Not sure of the gear ratio or posi unit type. Front suspension is our new Sniper IFS with RideTech coil-overs. We re-used the Baer rotors and calipers. The LS makes good power (est. 450hp) and it had a t-56 trans. - clutch unknown. Wheels are currently mis-matched (working on that) and we put on a set of used Falken 615 tires. 315/30/18 on all four corners. We had little time to test/tune and decided to leave a base alignment in the car so that it would be easier for Keith to get used to. Camber = -.5, Caster = +7.5, toe is 'in' 1/16". The IFS has 7 degree spindles. Street manners are great, one finger on the freeway, or no hands, rolls smooth and straight. For a track day, I would normally set the alignment as follows: Camber = -.8, Caster = +8.5, and toe 'out' 3/16". These subtle changes can make a big difference, but we didn't want to get ahead of ourselves.

Keith reports having a great time. The field was full with 76 entries. 18 in the GTV class. he placed well for the first time out.
Auto-X.................8th with a 46.702 lap....................27th over all
Speed Stop..........9th with a 11.167 run....................40th over all
Hot Lap ..............6th with a 44.934 lap ...................31rst over all
Design.................4th with 20.533 points
Overall GTV finish was 6th place.
Not bad out of 18 in the GTV class.
The biggest complaint was the brakes. Inconsistent feel and a low and soft pedal. We do not know what pads are on the car. The calipers use C5 front pads, my guess is these are the OE pads from the build. They will be going. Also, the master may be done. No big deal there either.
- If your headed to Raliegh N.C. for the GoodGuys event, come and check it out. Keith will be there, and hopefully we'll have V a bit more sorted.

[RobNoLimit]

Here is a finished subframe, powder-coated and ready to install. We will be starting the install in a few days. During the install we will show detailed picts and info on each component, and the install procedure. We are also starting a build thread on our house car, a fair-to-rough 68 that we acquired. The car has been nick-named "the Roach". Sad, but it is what it is, at least it will be a lot of fun.

Notice from the side view pict that the upper control arm mount has a pretty good rake. 10.6 degrees. One reason for the splayed lower arm is to get the motion of the lower ball joint to track the upper ball joint, so that we can minimize the caster gain, and still keep a big Anti-Dive angle. The Anti-Dive helps to keep the front suspension from compressing under hard braking. Keeping more brake load on the rear, and allowing the front shock compression to be tuned more for corner entry, and less for brake dive control.

[DJW32]

Rob,

Again, this looks great. Have you test fit a 4L80E in the new sub? If so, is there any cleared everything issues?

[cwylie]

I want one!

[RobNoLimit]

Rob,

Again, this looks great. Have you test fit a 4L80E in the new sub? If so, is there any cleared everything issues?

As far as clearing the sub, no problem. The trans mount will move enough to got from a 'Glide out to L480E, even 6L90E and T-56. The OE tunnel, well that's another story. Expect to do some sheet metal manipulation for the big gear boxes.

[RobNoLimit]

On the quest for a superior driving experience, and cutting edge performance, the Rack and Pinion choice was a big deal. Standard racks in use today (Mustang II, T-Bird, 'Vette) have an inner pivot width of 22" to 25", for our purposes, this is way too wide. We were looking for something in the 18" range. We worked with both Coleman Racing and Sweet Manufacturing to get exactly what we wanted. There was a lot to learn about these style of rack and pinions.

The ratios are set in "inches of travel" per one rotation of the steering wheel. These racks are available from 1 1/2" to 3" per rotation. The rack shaft on the Coleman racks are "Square" shafts, and the rack body's are machined with a square bed for the rack to travel in. This has a big advantage over a round shaft rack, round shaft racks can rotate slightly, and change the steering position, where as the square shaft racks do not.

Next is the power input servo. These control the amount of power assist, and how quickly in adds in the 'turn-in'. The servo's are controlled with an internal torsion bar. Torsion bar rates range from .185" dia. (lots of initial assist) to .280" (minimal initial assist).

Last is the slave cylinder. These are available from 1" dia. up to 1 1/2" dia. The larger the diameter, the more assist across the entire steering range.

It took a lot of math, and then a lot of trail and error to get the right combo. To easily steer a car with a 315 front tire in a parking lot, Navigate the tight U-Turns of a Goodguys coarse, and have a smooth controlled feel at high speed. All of this is achievable without using a specialized aftermarket pump. The normal GM Type-II pump is just fine. The larger piston volumes mean lower operating pressure, so cavitating, frothing, and over-heating is not a problem either. With the rack sitting in place in the subframe, the reason for the shape of the lower crossmember is clear.

[RobNoLimit]

test

[RobNoLimit]

We have had a lot of questions about brake choice and sizes. One of our goals is to provide the answers needed to help the builder finish the project. There are a ton of un-answered questions when doing a swap like this, and any one of them can stall the project. Being able to supply the needed information will help get the car done and on the road.

The Sniper spindle and hub are vastly different from anything else, and so it is up to us to provide some assistance in mounting brakes. We currently have matched up parts from Wilwood and TBM (we have done a Baer swap but don't have all of the part # information ready yet) The IFS comes with the Hub and we provide the rotor adapter, but we need to know which rotor mount pattern to provide. There are three common patterns. 8 x 7", 12 x 8.5", and 12 x 8.75". Here is the information we have currently to help with brake choice.

[RobNoLimit]

From a design/tuning standpoint the method of aligning the suspension will determined the type of upper control arm. So, there are a few choices.

1. Fixed Arm. This is the most common, and cost effective. These align with shims, cams or sliders. With this type of an arm, the length does not change. But, when the alignment is changed, the location of the pivot points of the upper arm also change. So, the rate of camber gain stays constant, but the steering relationships (bumpsteer) changes. Remember that in changing the alignment, the goal is to change the angle of the spindle.

2. Adjustable arm. Not as common. While this type may be more expensive, it can be repaired and maintained very easily. When aligning this type, the length of the arm changes, but the location of the inner pivot points does not. This has less effect on the steering relationships.

We made the choice to go with an adjustable arm to lessen any changes to steering geometry during alignments. Also, track side adjustments are very easy, loosen the jam nuts, rotate the adjuster sleeve, tighten the jam nuts. Make notes of how many "flats" you turn, and you can easily turn it back. Working with SPC on these was very enjoyable, as they were willing (without too much extra cost) to build us exactly what we wanted. The inner pivots are Delron lined and have grease zerks for smooth and quiet operation. The ball joint cups are set at 11 degrees 'in' and 3 degrees 'back' This keeps the ball joint pivot dead center in it's travel range at ride height, allowing maximum tuning and motion range. These use the K772 Chrysler screw in ball joints. These are a favorite of oval track and road racers. While we use the Moog ball joint in production, there are many versions available, such as the Howe precision Low Friction ball joints. They are also much stronger than the A and F body 4-bolt style ball joint.

**** Before you ask, we are not fond of using the lower A-arm as an alignment point, as doing so has drastic effects on the 'low' mounted steering on these types of suspension designs. ****

[carbuff]

Quick question Rob... On the ball joint plate, why is one end bolted while the other is welded? Are both arms adjustable? I'm wondering if it's due to arc-angles as you adjust, but I would think you'd want both to have some swivel in that case.

Really just curious. I like the approach and really appreciate the information you are sharing in explaining your design choices!

[RobNoLimit]

Think about the arm as a triangle, where the three points (corners) are where the three bolts are located. Geometrically, on these arms, the ball joint plate becomes a part of one of the 'legs' of the triangle. The welded stem on the ball joint plate also helps keep the plate and ball joint solidly located. As to the info sharing, your welcome, and thanks. We may not have first in the subframe market, but remember, it's the second mouse that gets the cheese. We're just trying to fill in a small segment of builders and enthusiasts looking for that next level of driving experience.

[cornfedbill]

Rob,

This is definitely out of the normal box. I like it. It shows that you put a lot of thought into the design.

I am looking forward to see how it performs.

Are you planning to bring something with this set-up to the Loveland Good Guys in the fall?

[RobNoLimit]

I'm not sure I'll make Loveland, but Keith might. He is the new owner of the Velocity Camaro, which now has a Sniper IFS. I know that his goal is to qualify the car for the GoodGuys Scottsdale Shootout, and the OUSCI. So if he needs the points, he'll be there. We are going to Raleigh this weekend for the GoodGuys show and the car will be there. Our current set back may be tires. We got a used set of Falkens in the winter when we put the new suspension in and have been testing and racing on them, and they're pretty worn out. - No new tires available at the moment, so Raleigh and Kissimmee we be on used hides. I bet she still makes the board.