MikeM

I suggested the radius rods MAY HAVE been added to control axle hop under hard brakingfor two reasons. One was the Corvette was conceived as a sports car and was factory backed in competition as such. Sports cars primarily were designed for sporty driving and sporty racing which would include hard braking which will cause the rear axle to hop, just like acceleration when the spring winds up and unwinds.

The car wasn't designed as a drag car which would also experience the hopping problem under hard, jerky acceleration. Most "sporty" drivers are reported to be much smoother on the clutch and gearshift under road race type conditions than drag racers on the strip.

Also, for a reason I can't explain, it seems more logical to put a radius rod above the spring to control braking forces and under the spring to control acceleration forces.

All the above is just a guess.

Plasticman

Mike,

The reason that I agreed originally with you is that it makes sense from a torque reaction and transfer standpoint.

Under acceleration, the axle want to twist bottom forward, lifting the front of the spring upward, and causing the spring to separate at each leaf (top leaf is the only one connected to the vehicle at the front spring hanger, and as it bows upward, it separates from it's supporting shorter leaves). Once overload is reached, the spring unwinds rapidly and hop results. Adding a Traction Bar underneath prevents this and transfers the axle rotational force to the frame through the bar. It is actually now just trying to stretch the leaf spring, not causing it to deflect upwards.

Now reverse that affect by adding the Radius Rod on top (without the Traction Bar below). Under braking, the axle is trying to rotate top forward. Again, the top Radius Rod prevents the axle from applying force to the leaf spring, but transfers the force through the rod to the frame. If the Radius Rod is not there, then the front half of the spring will be forced downward (and in this case, against the supporting shorter leaves). Once the spring reaches an overload, it deflects back rapidly (causing the axle to hop - washboard road or not).

In other words, it is the sudden spring deflection due to high and sudden torque application (and the quick release of that spring energy) that causes the wheel hop. Not the roughness of the road surface. Adding the rods or bars to transfer this force to the frame is of great benefit. But having both Traction Bars and Radius Rods does cause binding, so you are left with a decision. Leave both on, and suffer a harsher ride with decreased bushing life, or control the hop that is more of a "danger". At this point, I am more concerned with traction induced wheel hop, and subsequent breakage of parts. If I see brake induced wheel hop of any significance, my decision can always be reversed. As I mentioned before, the brake induced wheel hop may be more of a factor on stock drum brake Vettes with more equalize front/rear brake bias. With a front disk brake conversion, the bias shifts more towards the front, and reduces the amount of rear brake induced torque. To be seen if this theory holds true.

Plasticman

MikeM

I believe you're saying what I've been saying.

Plasticman

But you made it sound like you were so unsure of the reasons.

Besides, I like to sprout off a little!

Plasticman

wmf62

Bill

AZDoug

Took off the radius rods, yes the harsh ride went away, downside is there is some body roll around corners, haven't done much driving yet, but it is no longer the slot car like it was with the lift bars and radius rods. This was with the SSM lift bars, BTW, not Trac Masters.

At least my luguts are all polished up in back now,and the brake drums and inner fender well look real good with a fresh spray of semi-flat black paint.

Since the SSM lift bars clamp to the front of the spring I am wondering if I can use the radius rods with snubber bars, as snubber bars aren't clamped to the spring, and do not seem like they would create 6 link type suspension with the rad Rods like the SSM bars did.

Doug

Plasticman

Doug,

Would think the SSM bars are essentially the same as the Traction Masters in function and connection (from what I can tell). Do you have an anti-sway bar installed? I do have the anti-sway bar, and did not notice any handling difference with the lower traction Bars on vs. the upper rods.

I agree that snubbers bars would allow your Radius Rods to function as a link, but my problem with snubbers is they are really more of a straight line traction control part. When a snubber is used in taking corners, I see it suddenly contacting and stiffening up that side, but it is a sudden change, and not smooth. I would be afraid of using snubbers in that method (unless assured they would never contact during cornering).

For a better method, how about Cal-Tracs (or similar Comp. Engineering Slide-A-Link Bars) that has a built in internal for/aft snubber. That would allow the upper Rods to stay in place without binding from the lower "links". And yet retain the added traction control of a traction bar type lower link.

Here is a link to the Comp. Slide-A-Link parts sold by Summit:

http://store.summitracing.com/egnsea...03812&D=303812

Here is the install instructions:

http://static.summitracing.com/globa...c2096c2100.pdf

They do say to replace the front spring bushing with the supplied solid alum. bushing, and that is going to add a tad amount of harshness back in.

Problem with the Cal-Trac or Comp. Engineering parts is they do not have anything for our early Vettes. Cal-Trac did offer to make something up, but it would be money and time (as usual). Or you can call them and see what they have that is "close".

Plasticman

AZDoug

The SSM bars are not similar to the TracMas, CalTracs, slide a links etc.

The TM and CT bars have pivot , front and back.

The SSM bar is a solid bar, closely resembling a snubber bar except the SSM is captured in front by a clamp to the spring with no rubber bumper, and a snubber bar is free float in front but with the rubber snub.

i have my sway bar installed. the handling isn't bad at all, but not like with the radius rods installed, honest to god, with the SSM bars and the rad rods, the car went around corners like a Testarossa, of course that was on a reasonably flat surface, anything requireing suspension travel on a corner would probably require finesse.

Doug

Plasticman

Doug,

I was referring to function of the SSM bar essentially being the same as a Traction Master in that it transfers the torque reaction of the twisting axle to the frame. In the case of a SSM bar, it transfers it to the front of the leaf spring (which does the double duty of pivoting as needed, instead of a separate mount and pivot, plus the torque transfer to the frame). The function is very similar, just different method and mounting.

I was just offering an alternative that would still offer the control, yet not have the harshness of the "6 link". But would not have the variable undesirable characteristics of a snubber bar when cornering.

Take it for what it is worth,

Plasticman

JohnZ

The SSM bars that clamp to the front of the spring significantly increase rear roll stiffness (and oversteer), beyond that provided by the rear stabilizer bar; be careful at the limit - it'll break loose QUICK.

AZDoug

I feels like it will, keeps you on your toes, it is glued to the road, then suddenly just wants to go its own way, thus one of my desires to go with a snubber bar which will let the rear suspension act normally, and I think I can reinstall the radius rods with the snubbers without causing any binding. I figure GM wouldn't have put them there if they weren't needed, so I will try to keep them if they don't cause problems

The only disadvantage to snubbers that i can tell is visual and maybe ground clearance at tall speed bumps, they hang down lower and are way obvious, getting rid of the yellow that lakewood ships them painted with,a nd making them flat black will help with that.

Doug