A Max-Effort Build

[Sky Render]

When they discontinued 5.0 Magazine (which had decent tech articles), they switched my subscription to Muscle Mustangs and Fast Fords, a rag containing mostly car show builds and information on racing in a straight line. The "tech" articles are clearly sponsored by poseur brands such as Steeda. I generally thumb through the magazine once and drop it in the recycling bin, wondering when my subscription will finally expire.

So, I was pretty excited to see an article about a max-effort road race build! The owner races at Autobahn Country Club, which has less-stringent class rules than national series, so basically, he was able to throw EVERYTHING into this car: SLA front suspension, CV joints and camber on the rear axle...

http://www.mustangandfords.com/feat...homas-herbs-wild-2012-road-race-ford-mustang/

Discuss.

 

[MechE]

I know this is the least, "corner carving", thing about the car, but 9000 RPM?!!! I gotta hear that!

 

[Boone]

I saw that article. It was the first thing I dove into when I got my mag. Wasn't the SLA setup by Griggs, and once the SLA is in and front grip exceeds rear grip, the cambered rear axle actually makes sense.

Would this setup be streetable? I need something on my wish list.

 

[Sky Render]

Anything is streetable, if you try hard and believe in yourself.

 

[CobraRed]

Wanted to just scroll thru, read entire thing. We want.

 

[DevGittinJr]

Wasn't the SLA setup by Griggs, and once the SLA is in and front grip exceeds rear grip, the cambered rear axle actually makes sense.

IIRC, PWC GTS Mustangs are using the Cortex cambered axle (and watts) without the SLA. I've wondered how they get enough front grip to balance the car, with that much rear grip and the axles being available up to -2.5 degrees. My guess (not necessarily an educated one) is that SLA or not, all other things being equal, the rear roll-center adjustment in relation to the COG and inside rear tire loading/unloading, would mostly determine how much camber the axle needs. I'd also guess that because of the camber (the more you add the more this applies), the inside rear tire wouldn't need to unload as much to get the car to rotate. Supposedly, the watts/cambered axle combo reduced lap times by an average of a second for the one GTS team in particular, which is impressive given how consistent pro drivers and their setups typically are. Regardless, cambered rear axles for s197 is definitely an interesting topic.

 

[Boaisy]

Most of the ideas in that car is about the same path I was going to go. I wonder if they will sell the car anytime soon?

 

[SoundGuyDave]

I race in the series this car was built for (thank God not in his class, though!), and I haven't seen it out on track yet. June 11 is going to be interesting, for sure!

 

[Sky Render]

I race in the series this car was built for (thank God not in his class, though!), and I haven't seen it out on track yet. June 11 is going to be interesting, for sure!

We require a video of the unholy noise this thing makes at 9 grand.

 

[Norm Peterson]

IIRC, PWC GTS Mustangs are using the Cortex cambered axle (and watts) without the SLA. I've wondered how they get enough front grip to balance the car, with that much rear grip and the axles being available up to -2.5 degrees. My guess (not necessarily an educated one) is that SLA or not, all other things being equal, the rear roll-center adjustment in relation to the COG and inside rear tire loading/unloading, would mostly determine how much camber the axle needs. I'd also guess that because of the camber (the more you add the more this applies), the inside rear tire wouldn't need to unload as much to get the car to rotate. Supposedly, the watts/cambered axle combo reduced lap times by an average of a second for the one GTS team in particular, which is impressive given how consistent pro drivers and their setups typically are. Regardless, cambered rear axles for s197 is definitely an interesting topic.

Stick axles also "roll" in a corner, up to perhaps a degree or more per lateral g due to tire vertical stiffness and lateral load transfer. You'd want to cover for that much if possible. Plus a little because peak lateral tire grip probably doesn't occur precisely at zero camber like the easy assumption suggests. Choose geo roll center locations, springs, bars, and dampers around whatever you can get.

A decambered rear axle has crossed my mind more than once, for more cars than just this one. At some point, maybe about 1° per side, you should start considering axles with barrel-profile splines.


Norm

 

[Vorshlag-Fair]

All that work, sequential trans, and they slap a torque arm on there...

 

[SoundGuyDave]

I'm with you on that one... Drank the Griggs "fit an SN95 kit under there" kool-aide for sure. With the rest of the kit, though... Damn. Just damn... Fall-line builds some beautiful race cars, including the season champs from the last two years, but I don't think they know the ins and outs of the S197 platform. Hanging $20K worth of Griggs suspension under it was most likely the "easy button."

Sky: My car is down at the moment doing a re-build post slicks/rain/wall/lack-o-talent, so I don't have a ride at the moment. I'm talking with a former student about mounting an effort, but if I do, it'll be in a CMC Firebird. The 0.063 seconds of video as it goes by should be entertaining. Otherwise, I'll be crewing for a 944 team.

This series is about as far from crap-can as you can get. The car in question is in GT4, and there's a whole 'nother power-weight class ABOVE it. I run in GT2, for what it's worth. Dry-break fueling, slicks (Pirelli, not R7!!), and lots of aero are the norm.

 

[Boaisy]

I've been trying to get into 944 racing since I lost my GT. Just waiting on $$$ to get in order. Lots of the local guys hopped on that once it started.

 

[Mark Aubele]

All that work, sequential trans, and they slap a torque arm on there...

Plenty of people on this site still think they are magical because Cortex and Griggs sell them. Don't get why you would remove a perfectly good three link for a wheelhopping torque arm (outside of a rules issue).

 

[CobraRed]

I'm with you on that one... Drank the Griggs "fit an SN95 kit under there" kool-aide for sure.

Plenty of people on this site still think they are magical because Cortex and Griggs sell them. Don't get why you would remove a perfectly good three link for a wheelhopping torque arm (outside of a rules issue).

My exact thoughts when reading, didn't say anything because I thought it would start some big debate. Glad I'm not alone.

 

[Roadracer350]

I want that cambered rear end!

 

[El_Tortuga]

Stick axles also "roll" in a corner, up to perhaps a degree or more per lateral g due to tire vertical stiffness and lateral load transfer. You'd want to cover for that much if possible. Plus a little because peak lateral tire grip probably doesn't occur precisely at zero camber like the easy assumption suggests. Choose geo roll center locations, springs, bars, and dampers around whatever you can get.

A decambered rear axle has crossed my mind more than once, for more cars than just this one. At some point, maybe about 1° per side, you should start considering axles with barrel-profile splines.


Norm

So I would want about 3 degrees. Even with a couple degrees of body roll the outside front looks great. Negative net camber means the tire patch is pretty flat after sidewall deflection. In the back, it's a couple of degrees positive. I'm headed for a softer rear bar like the 6 cyl sway

 

[El_Tortuga]

So I would want about 3 degrees. Even with a couple degrees of body roll the outside front looks great. Negative net camber means the tire patch is pretty flat after sidewall deflection. In the back, it's a couple of degrees positive. �� I'm headed for a softer rear bar like the 6 cyl sway

Admittedly, this is the most dramatic pic I could find of my whip. Slow right hander, power on so torque is twisting the axle, and downhill.

 

[SoundGuyDave]

I want that cambered rear end!

Cortex sells one purpose-built for the S197 chassis. After you fit it with a diff and brakes, you're out $10-$12 kilobux.

 

[Pentalab]

I want that cambered rear end!

Forget the $10-$12K mod. Just buy a 2015-2016-2017 car.... which has oem adjustable rear camber.... from zero to as much as -2.7 degs. Plus IRS. The 05-10 cars are long gone obsolete in every aspect from engine to tranny to suspension, lack of irs, no rear camber adj etc. The 11-14 cars are not far behind.

Sure you can add neg camber to the rear....for $10-$12K, but now you require deep pockets to 'fix' issues that should have been addressed earlier.