Just a question on gasser suspension, I’ve noticed a lot of cars have the radius wheel wells very close to the tire, it looks great but are they generally running with no travel? I’d assume they would be up against a bumpstop or some other limiter? Is it typical for drag car to run no travel? I understand a typical parallel leaf setup with a straight axle would not ride very well, so maybe most don’t care about the rear ride anyway? Also, how does a typical parallel leaf straight axle car compare in terms of handling to a transverse leaf early ford hotrod setup? Assuming both are set up correctly. I’m getting into a 55 chev gasser project, and wonder what to expect compared to my model a straight axle (which I find handles great and a pleasure to drive).
bump.. Take Blasphemi for example, there has to be no down travel in that rear suspension, but it is street driven. Maybe the coilovers are cranked for street duty, or swapped out? Is it typical of drag cars to run with no suspension travel? I have ordered some books on chassis design, just wondering on stuff while waiting for them to come. When I built my model A, I went with a triangulated 4 link and coil overs. I get about 2" of suspension down travel and feels like they would be the min you'd want on the street. The picture below looks it would have 1/2" at the most.
it's almost like he puts on different tires for street driving but I think the spring rate is rather stiff.
Good point, didn't think of that. I suppose most I see would be drag car, and the remaining are probably projects still mostly mocked up.
I have a 63 Impala that was turned into a drag car in about 1966. Has a beam axle front end, Olds rear, leaf springs at all four corners. Very little rear suspension travel. The back of that car is STIFF.
Someone went to a lot of trouble to get the Impala to set on 4 leaf springs. Hope it was worth it. Looks good , but that's a x frame car with coil springs on all 4 corners. Maybe they sit it on a different chassis.
When you set a 55 Chevy level before cutting off the front of the frame and independent suspension to install rectangular tubing frame for a straight axle, what part of the original car is considered for 'level'? Bottom of the frame under the front seat?
The rear springs need to be stiff enough to support all of the cars mass when launching. Ladder bars need to be set up in 100% or greater "anti-squat" [this causes suspension "extension" which plants the tyres hard into the ground][sometimes called separation] Shocks need to be set reasonably stiff on compression to keep the tyres planted [so the suspension "returns" slowly] Setting it up this way and there should be minimal [if any] compression from static position
This is where I ran mine without issue, but it looks better a little lower This is where I think it looks the best, but it's really a trial and error process with springs settling over use.
The science of launch geometry was certainly known in the gasser era, but was it applied? It looks a lot like that famous Colin Chapman quote, "Any suspension, no matter how poorly designed, can be made to work reasonably well if you just stop it from moving," usually paraphrased as, "Any suspension can work if you don't let it." If the rear springs are stiff enough, the whole business of instant centres and such becomes moot. Very stiff rear springs plus even the most rudimentary roll cage will do a lot to mitigate the effects of engine torque reaction onto the rear axle. But the resulting rearward roll stiffness bias could make the car a handful on the street, especially if ordinarily masked by a lot of grip from the rear tyres. I'd expect dogged understeer until the car suddenly changes its mind. The advantage of later launch geometry is that if the instant centre is located well, the car should launch exactly as if it had solid rear suspension, without any squat at all. The rear suspension would, however, be able to move as needed under any other circumstances.
All mine have close tolerances, and I do it the same for all of them. A little stiffer spring rate, whether it's coilovers or leaf springs, and most important!...polyurethane bump stops above the axle on each side. If all else fails and I have the bump stops set to keep even a pothole surprise from allowing the tires to contact the fenders.
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