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Old 10-06-2005, 04:00 AM
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RRS Front Suspension Geometry: No Anti-dive?

http://www.rrs-online.com/html/suspension.htm

Is anyone familiar with their products? There doesn't seem to be any anti-dive characteristics built into the suspension geometry. All the strut suspensions I've seen in the past have the strut angled forward slightly.

I've read this was to create anti-dive and reduce ride harshness, allowing the tire to kick back slightly rather than moving straight up. Is this important or is it only needed for stock vehicles?

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Old 10-06-2005, 06:57 AM
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No, it's not necessary, but, yes, I certainly like it in a car. There have been different philosophies expressed by GM and Ford. Back in the late fifties and sixties, if you hit the brakes on a Ford product, the front bumper almost hit the ground. Not true with a GM product. Now, both outfits knew how to design in anti-dive, so why didn't Ford do it? Well, the management at Ford felt that too much ride quality was sacrificed with the amount of anti-dive their rival was using.

So, that's it. As often happens with mechanical design, a compromise is required. Where you decide to draw the line is up to you. If your car is down in the weeds, you probably wouldn't notice the complete absence of anti-dive. But, with those ungainly cars of the sixties...with their soft suspensions..., it was very noticeable.
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Old 10-06-2005, 07:59 AM
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Anti dive.

The rear suspension can play a big part too. I assume you're talking Falcon or Mustang, so, lower the front spring eye - try to keep it 2 -3 degrees lower than the upper shackle pin, then correct your pinion angle with 4wd caster wedges or relocated spring mounts.
I don't like RRS (and I like to buy Australian) because like all struts you lose your camber change. With a dual A - arm front you can move the ride height and pivots to induce big neg camber on compression thereby planting the outside tread. If you run 6 deg neg camber like strut racecars must, you get cornering but a VERRY nervous car on rough roads or in side winds.
Struts are like r & p steering, light, cheap and ugly on bad roads - we got plenty of them.
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Old 10-06-2005, 11:09 PM
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Thanks guys, that's the frst time I got any responses to that question. I tried the http://www.pro-touring.com forum but it fell on deaf ears.

Based on the RRS pictures I'm guessing the brake caliper location was one reason for not angling the strut slightly forward.
When you say not necessary, does that mean that you have to compensate for dive in some other way like an increased spring rate or shock dampening?

I've been working on/off on a design of my own that is somewhere in between the Fatman and the RRS set up but at a fraction of the price. It's going to be using a late model Mustang Cobra strut with a coil over conversion and I want to make a bracket that can be bolted to the early Ford A-arm type spindle. I'd like to retain the original lower control arm, brakes, anti-sway bar and steering...at least for now.

Yes, I'm talking about Falcon or Mustang, Cougar and Torino.
I hadn't considered the rear suspension. I figured with weight distribution and weight transfer from braking would leave it up to the front suspension.

"...try to keep it 2 -3 degrees lower than the upper shackle pin, then correct your pinion angle with 4wd caster wedges or relocated spring mounts."

I don't suppose there's a simple way to measure this?

"I don't like RRS (and I like to buy Australian) because like all struts you lose your camber change."

I like to buy Australian too. I'm the only one in the US who owns an XY, XB and XC Falcon. I don't have a problem with RRS except for all the bells and whistles that don't mean much.

"With a dual A - arm front you can move the ride height and pivots to induce big neg camber on compression thereby planting the outside tread."

Excerpt from

http://www.jwfisher.com/sec-ford/FMC...on/default.htm

"...the Super Stallion was nothing more than a show car (introduced at the 1997 SEMA show). However, it did reveal to the public for the first time the front SLA and rear IRS work that had been done. Several magazine articles of the time showed detailed photos of the front and rear suspension. Unfortunately, none of these unique suspension pieces would ever be seen again, much less in production."

I'm assuming this is like the TBird's SLA. I wonder why they haven't followed up on this design.

"With a dual A - arm front you can move the ride height and pivots to induce big neg camber on compression thereby planting the outside tread."

Does an LSA work the same?
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Old 10-07-2005, 06:09 AM
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Quote:
Originally Posted by Brian S
When you say not necessary, does that mean that you have to compensate for dive in some other way like an increased spring rate or shock dampening?
No, it means that you don't have to compensate at all if you don't wish to do so. It's like anti-squat at the rear suspension. It's not at all uncommon, here in the States, to see rods with horizontal and parallel trailing links at the rear, meaning absolutely no anti-squat. They squat horribly, but the owners are evidently content. Again, dive on braking is not so bad if the car has a low CG. And, since so much of the braking effort is at the front, it's the front suspension design that is critical.

Incidentally, I dislike the struts, also, and for the same reason.


Quote:
Originally Posted by Brian S
Does an LSA work the same?
No, it's the short upper arm which, during jounce, pulls in the top of the spindle and gives you the negative camber you desire.

I might be wrong, but I get the impression that Aussie rodders are much more suspension-savvy than those in the States. I would guess that it's due to the greater interest in Formula One.
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Old 10-07-2005, 05:43 PM
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Quote:
I might be wrong, but I get the impression that Aussie rodders are much more suspension-savvy than those in the States. I would guess that it's due to the greater interest in Formula One.
I have great interest in F1, I just can't get Kimi to return my calls when I want to know his suspension settings...
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Old 10-10-2005, 06:52 AM
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Formula one means little to most Australians. We're suspension savvy because our roads suck, and most travel is still by road.
I'm building a 72 Holden ute (like a STRONG El Camino) with 10 deg pos caster and 5 deg camber on compression with only 30 mins neg @ ride height. With a lowered front spring eye it should tear up tar under brakes.
Not all Aussies are suspension savvy, some people like struts and the really dumb ones buy fwd's.

Check early Mustang lower arms as they should be longer than your XY's, this was a popular swap here, both to maintain 0 camber on extension for drag cars, and to induce neg camber for touring cars.
If you have trouble visualising a modified sla front end, cut three different lengths of balsa and make up a dummy, then change the pivot points and observe the changes in geometry.

To check the relationship between the spring eye and the lower shackle pin, set the car at ride height, and measure to the flat floor. using the horizontal plane you can make a triangle and measure the downward slant of the springs. Too much can make the car 'waltz' under brakes, even tho' it's not diving.
All those Fords are weak in the front, so you might want to use a triangular brace from the spring towers to the firewall - cornering forces can be high.
I won't run directional tyres here because they 'tramline' (follow rough surfaces) and can create more bump steer problems if things aren't perfect.
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Old 10-11-2005, 02:03 AM
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IMHO no true street car needs all that suspension. If you actually drive it that agressively you are a danger to society.

Of course, we don't need 450 hp either, do we.?????... LOL

Billy, I think most of the hot rodders in the US still believe that when the rear squats the car is hooking. Except the ladder bar guys, but they think that turning corners is irrelavent.

Anti-dive?? Has anyone looked at the strut Fox/sn95 cars slidiing to a stop??? yikes. And the aftermarket is installing these front ends into older cars as an ugrade.

The pro-touring thing that is sweeping the US the last few years and gaining momentum daily is beginning to get more rodders interested in suspension geometry and handling, and the aftermarket reflects this.

The air-bag guys want little geometry change with ride height, with their empahsis on height and smooth ride.

I still deal with a lot of rear leaf spring cars, Fords and Mopar mostly.
Billy, I'd like to hear your take on the old traction masters that Shelby used on the GT350 cars. I still hear "experts" say that if it was good enough for Carroll then it is good enough. I think that Shel used them because of the rule book limitations. The TM are ancient tech, they stop hop, but don't do any lift/plant or anti dive.

Me, I generally favor the ancient mopar-super-stock-spring thing.

rrrrrrrraaaaaaaaaahhhhhhhhrrrrrrrr Is that the sound dinosaurs make?
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Old 10-11-2005, 07:08 AM
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We're getting off subject, but, a few years ago, some were suggesting that curves be added to the dragstrip. I'm not certain if anyone got very far in developing and building such a site, but the idea was that the two cars would go straight for a furlong or so and then enter into some identical curves, finishing side by side. The concept is great, but I don't think you could ever come up with truly identical "lanes."

Some paved ovals have "one lap drag races," but they start the cars side by side, meaning one car will have the favored inside path through the turns. It would be far better to start the cars on opposite straights, so that they never come close to each other. But, owners of oval tracks seem to think that the paying customers won't appreciate it if there isn't the potential for "bumping and banging." This is really unfortunate, for the "opposite straight start" would, I'm sure, attract even the SCCA types who normally run autocrosses. I'd certainly pay admission to watch Porsches pair off against GTO's. Wouldn't take much to wire up some "win" lights so spectators wouldn't have to guess on close races.

Don't have much truck with leaf springs. They were a compromise on the production cars, so I wouldn't spend much time fooling with them on a competition car. The front brackets provide convenient attachment points for a couple of lower links (pivoting at the rear). Add a single upper link, offset to the right, and you have what I consider the very best dragstrip rear suspension. Unfortunately, for optimum results, the angles and offset are critical. So, I recommend a 4link with the links of each link pair parallel. With the right side link pair angled about 10 degrees greater than the angle having a tangent equal to the CG height divided by the wheelbase and with the left side link pair at 10 degrees less, rear tire loading will be very close to equal with any driveshaft torque and, since there will be no binding during cornering, you can even drive it on the street.

If you don't want to discard the leaf springs, the best fix is to use an adjustable coilover at the right front with a right front spring having a spring rate about 50% greater than that at the left front. (Torsion bar Mopar cars can pull off this trick very easily, of course.) Then, use wheel scales to adjust rear wheel loading to be equal statically. This, again, will tend to yield equal rear tire loading during launch.
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Old 10-12-2005, 03:45 AM
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Old Ramcharger.

Years ago I ran 2 50/50 shockers on the rhr because the cops would defect me for uneven ride height with an extra leaf. It would still break the lhf sway bar link about every 6 months.
I live on a dirt road and repair European cars, I've yet to drive an irs that didn't loosen your fillings, anti - squat Benz v8s(w116/126) seem as bad as any! No manufacturer seems to be able to match shocker valving or sway bar rates to their progressive rate springs - Ford and honda are the worst I've driven. I prefer linear rate coils purely because they're easier to tune.
That first Ramcharger looked ugly enough to be fun, were it a handfull?
Check out the Geelong speed trials, it's a curved quarter mile run (sadly) against the clock. Any vintage race car can and does run, pony cars, 409 Impalas, 427 Galaxies, local Monaro/Falcon GT/Chargers and Toranas,pre ww1 GP cars, Minis, Ferraris, Porsches, Lambos, 60's F1s etc. It's a great weekend with good food and grog.
Did I tell you I hate struts?
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