Rear wheel steering thoughts???

[Kburman12]

Hey guys, was curious to know some of your thoughts on the issue.

I've been studying different engineering ideas used in modern supercars to see what I could possibly apply to my 1973 Camaro. I've decided to go with a modern corvette chassis to install. I mention that so maybe you can get an idea of what kind of build I'm trying to do.

I understand that the rear wheel steering is used mainly in the off-road world. I've learned this setup has some pretty good performance adavantages on high speed stability and in tight corners such as an auto cross.

Y'all tell me what you think about this idea and let me know where an aftermarket unit might be worth looking into.

[andrewb70]

Are you talking about active rear steering or passive systems?

Andrew

[Kburman12]

Active rear steering

[NOT A TA]

A buddy of mine bought a new Honda Prelude in the late 80's with the 4 wheel steering. IIRC it was one of the quickest cars through the slalom tested by the car magazines.

[Ron Sutton]

Are you talking about a programmable system that will have positive rear steer in low speed corners & counter steering in high speed corners?

[Kburman12]

Yes this is exactly what I'm talking about

[Ron Sutton]

Yes this is exactly what I'm talking about

As the guys are saying ... complex. But forgetting the work for a minute ...

If you make the car have positive rear steer for autocross & counter rear steer for road courses & open road runs, you can achieve a marginal performance gain. This same gain could be achieved by tuning the roll stiffness of the car with sway bars. Your way is "trick". The sway bar way is simple. Same end result.

Best wishes !

[raustinss]

I'm going to say way too complicated to get it right and safe

[cornfedbill]

In my opinion it really depends on what you want to do with the car - autocross, road course, open road racing, canyon carving, etc. For autocross there may be some real advantages. However, if weight is a factor, I would forego the complexity and mass. In reality, most of our cars are multi-purpose and do everything from driving to Dairy Queen for ice cream to the rare high speed blast down a curvy section of pavement. Maybe we go to a track day, or an autocross from time to time. The operating conditions and road surface, along with tire temperatures, are constantly changing.

For an open road race car where slow speed cornering is not a real factor and the road surface is well maintained, a passive steering would not be so bad. Even the old Trans Am racers had passive rear steer by changing the angles and mounting of the rear leaf springs.

Although I am an automotive engineer and have many of my parts out there on very complex high performance automobiles still in production, I prefer simplicity. I would not choose rear steer, even with a high tech Corvette-based suspension unless it was based solely on the body lean while cornering. I would not have any linkages from the steering system or computer controls. I don't think the theory translates into practice to a high degree because there are so many other variables in a car that is multi-functional - road going, autocross, asphalt, cement, and so forth. And yes, I have driven one of the old rear-steer Preludes. Cool car.

I ran the Sandhills Open Road Challenge this summer. The road surface was pea-gravel embedded in tar. It was like driving on the tops of little marbles glued to the road surface. The road was very rough in spots and was not optimal for cornering. A high tech system like rear steer would have been dead weight there. And yes, we ran hard through the corners only dipping below 90 mph for two corners in the 30 mile stretch.

That's my opinion. It's worth at least what you paid for it.

[Kburman12]

The intentions are to build this Camaro as an all around performance car. I have every intention on putting it in the ringer on the road course, auto cross, drag strip, and be a great street car.

I've chosen to go with a corvette chassis to help build a rear weight bias, or get as close to 50/50 weight distribution. I'm going to attempt to make the front clip as light as possible.

If adding a weight will help put power to the ground and help reduce lap times, seems like it would be well worth it in my opinion.

[andrewb70]

You'll have your hands full as it is. In my book, rear steering is one of those novelty items that add minimal return for the amount of work put in.

Andrew

[hquackenboss]

I think it is important to understand that the manufacturers that have developed active rear steering fully optimized their cars before adding rear steer, and therefore had a solid baseline to compare the active steering improvements (if any). I would suggest that whether or not you have an engineering background, unless you have the math skills and the attention span to digest three books on suspension, including Herb Adams Chassis Engineering, Carroll Smith's Tune to Win, and Bill/Doug Milliken's Race Car Vehicle Dynamics and the companion Problems, Answers and Experiments workbook, you are unlikely to be happy with the result, because you won't have either the baseline vehicle performance measurements (and driver feel), nor the engineering basis to be able to analyze what is going on and how to make it better.

You didn't say which Corvette chassis you wanted to slide under your Camaro (unless you plan to use a C5, C6, or C7, I wouldn't do that), but if you build a car as you describe, with careful workmanship, and spend time tuning it, including getting the front/rear handling balance correct, optimizing alignment, particularly the front and rear camber and toe settings, you should be able to achieve handling as good as a C6 or C7 Z06, that is easy to drive fast. Once you have done that, you should be the envy of everybody who sees your car run, let alone drives it. And then, if you want to add active rear steer, you will have a baseline to compare. Then, experiment with various rear toe settings from toe in to toe out, and recognize the different feel, and measure its performance through a slalom, and how quickly you can get back to the throttle coming our of a corner. Once you do all that you will have a rational basis for deciding if you want active rear steer, and if so, what parameters. And then, retrofitting active steering to the Corvette will involve some ingenuity in picking what components to use, but you shouldn't have to redesign the whole rear suspension.

[Kburman12]

I'm hoping to stick either C6 Z06 or a new C7 or C7 Z06 chassis. I'm hoping to build a custom full frame to either utilize the corvette cradle and suspension or develop a cantilever suspension or pushrod suspension. Leaning more toward the cantilever though. If I'm able to use a C7 suspension, I'm hoping to be able to install the ECM to utilize the traction control or magnetic ride control. However, knowing that dealing with computers can be tricky, with what research I've done, a cantilever suspension seems to be the route I'm willing to go down for more adjustability.

For the weight distribution, I've decided to go ahead and bite the bullet and use as much carbon fiber in the front end as possible. The engine is going to be set back in the engine bay approximately 3-5 due to the length or the torque tube and driveshaft, but this is a great benefit. I'll be trying to develop cooling unit that provides auxiliary radiators in the front and better aerodynamics.

I'm obviously gonna put some meat for tires for a more square setup at all four corners. This will require fender flares. I've picked up some ideas to help develop some better aero for functional cooling and to help provide more downforce. Things such as brake ducts, fender vents, air intakes for radiators, hood heat extracting vents, air intake vents in the rear fenders for transmission and differential cooling, (I've been looking into F1 aero development to try and understand how I could use air underneath the car for this instead). I've been thinking of trying to use an idea from the Ford GT and hollow the tail lamps and connect the rear wheel wells so air can escape and relieve built up pressure.

Still trying to do a lot of homework. When I am either doing a crappy job of looking for my answer I reach out to you guys. Y'all are the experts and I'm a novice looking to get my project car as fast as possible.

This rear steering idea is definitely something I wanted to reach out for. It seems like it would be too much of a hassle to deal with. I've already got a lot I'm trying to do. I appreciate all of the feedback. I'll be looking forward to asking all of your opinions in the future again.

[cornfedbill]

Good luck. I am eager to see how your project turns out. It definitely sounds quite out of the box. I like different. I see far too many LS/T56 bolt-on subframe Camaros that are bolted together, not fabricated.

I can tell you from participating in the Sandhills Open Road Challenge that the open road race events are dominated by C6 and C7 Corvettes. They are very capable cars. If you use the components properly and maintain the factory balance and dynamics, you will have a very solid package.

[Ron Sutton]

My client, Tom Whalen, won both the Silver State & Big Bend Open Road events last year in his C5 Corvette. (By won, I mean the highest speed in the Open Class) He had totaled a C5 a year earlier when it got loose on him in a high speed corner. Crashed at 170 mph. Went end over end.

The cause of the crash is when you lower these C5/C6/C7 Corvettes, the rear suspension creates positive rear steer ... which reduces rear grip. The faster you go through a corner, the less rear grip you have. Tom came to me & we re-engineered the suspension in another C5 he bought. We raised the rear roll center, corrected the front, got the right springs & bars on it. But the big deal is we ... Scot McMillan from Scot Rods in Texas and I ... changed the rear setup to have COUNTER rear steer during body roll. So the faster you corner ... the more rear grip you have. After that, Tom had the grip & confidence to win both the Silver State & Big Bend Open Road events.

You can see his car in our catalog HERE