Ok I have now had several pretty long "work the bugs out" runs with my 29 Roadster. The flatty is running cool, smooth and strong. What I have found that I would REALLY like to improve is the ride at the rear.........very bouncy! I have maintained the rumble seat so no fuel tank or battery back there. I could (all were suggested in the "How to Build" book: swap some short length leaves for some softer riding leaves. install softer shocks. or which seemed to solve Bishop/Tardel's case......add weight, 200lbs worth. My questions here: What kind of weight and put it where? What have the rest of you AV8 Roadster folks discovered?
Well, you have a rumbleseat. If you know some fat people and some thin people, there's your set of development tools...try different loads of flesh and see what happens. If this is a good path for you, you will get a weight target and then you can start thinking about finding weights that don't need to be fed.
Beaner......yup, that was mentioned in my post (swapping leaves). Thanks. I'd like to know what material and where to place it once I have an idea of the weight I need to add? I don't think keeping the folks in the rumble seat all the time will work out very well!
You can do some spring and shock tuning, but I think on this car shocks just fundamentally can't control the axle because axle is too heavy for the sprung weight above it...it will bounce the whole car. Big general problem for small rods, there isn't much in the way of axles or brakes light enough. Best cure would be independent rear, moving the weight to the sprung side, but Jag rear on and A-V8 would be more disturbing than bad ride... Weight that could go aft without actually adding to total car weight might include battery, spare, tools, gas tank, etc. Moving weight ALL the way back, like with stock spare tire mount, would produce maximum leverage for the weight but would make handling less responsive than having weight at rear inside of wheelbase.
In some drag classes they allow stacked weights on a bar, like the old time weight lifters used to us before all the machines became popular. You can still find that stuff at yard sales cheap (usually a fat guy seated at the pay me now table). You may have to experiment a little bit weight behind the axle seems to make the biggest difference but for handling's sake you may prefer it before the axle. The free weights on a bar make it easier to adjust your weight and I would put a little bit on each side.
I'd personally do a whole lot to soften it up before putting in weights. Why have to haul around extra that you dont need. Not that hot rods are for fuel economy... but youd be wasting fuel. And.... its going to slow you down
Thanks Beaner. Gearhead Graphics......I'm not so sure I can get the ride soft enough doing that but worth a try. I know when I ran the A in stock form it jumped around some but the way it is now is just silly! My 32 pickup was to soft and the frame was hitting the axle until I replaced a long spring leaf with a shorter one....that did the trick. Here we have some pretty nasty roads.
I had a thread up a while back on BOOTLEGGER CAR SUSPENSION. You might consider the doubling up of lever shocks or pairing them with tube shocks out back. That and maybe collecting some discarded weights or putting a tank back there that you can fill with water maybe.
I would quantify the 'bouncy' part, your shocks might be too stiff or not stiff enough. If you have a tube shock the put a tie wrap around the shaft and go for a ride over railroad tracks to get the bounce, then look at the shock to see if the tiewrap has moved. Adding weight/springs etc will change the ride height. Can you 'jounce' it on each corner? When the weight is off the rear when you lower it back onto the suspension the amount of travel should be 1/2 of the available shock travel. You have a floor jack under the frame and the rear is hanging 'loose' (actually the shocks are at full extension) and measure the shock travel - call it 6", when you lower the car back onto the suspension is there 3" of travel available to the shock? That is presuming you have tube not lever shocks, if you have lever then you need to get more creative with measuring. All I have suggested is an attempt to define what the shock is doing or not doing.
Thanks oj When we installed the tube shocks we took into account the correct movement. I'm pretty sure they are not the issue. It's a good stiff jolt in the rear over bumpy roads (which we have plenty of). My rear spring pack consists of: 5 leaves (progressively shorter up into the cross member) w/main leaf reverse eye and 4 under it to fill the pack. If you attempt to push down on the body rear quarter from the top......there is no movement.....to me that's stiff.
So that means you have either 8 or 9 (depending on how the main leaf fits in) leaves in a car that only had 7 to begin with? Also the leaves under the main, if original length with have some force on the main when you tighten up the u-bolts. Had the same initial problem with my '29 coupster and found there are 2 different rear spring retainers that the u-bolts go through. One deeper than the other (Go to Bratton's website). Also used the shortest leaves under the main, but may still have to cut the down. I can't remember how many they used in the spring pack in the Tardel book, but 7 or 5 comes to mind. Like you combo of years also.
Yes, B/T had 7 and they removed the 4 short and cut them for the bottom fill. I didn't take pics of my finished pack and I can't see the top leaves for a good count and I may be less than stated but I do have the cut (to 12") 4 on the bottom to fill. So, I could in fact have only 4 above those. The short ones of the 4 on top make for a stiffer ride while the longer ones soften it.......unless I'm mistaken?
That's the best test for getting into the ballpark. If it won't budge, take shocks off while de-leafing the spring. IMO. Get the spring softened up first, IMO Shocks can really mess things up on a light rear body. I always arm test them before I even try to see if they fit.
Well, that about sums it up. If you can't push the thing down, sounds like the spring is stiff to almost rigid for the weight of the car. More softening in order...you should be able to get some bounce out of it by hand. A basic test is to try to bounce it with the shocks disconnected. If you can't, the spring is definitely too stiff. And make sure the leaves can slide.
Thanks guys. With the B/T roadster.....they softened the spring and shocks but was still to stiff.....so, they added 200lbs of dead weight somewhere at the back. I have send a message to Mike about the weight and what and where it was used. So far, I have not heard back. Yes, I'm going to disconnect the shocks and then push down. Yes, I have considered a T spring which will give me a little lower stance and that I wouldn't mind because I did not z my frame due to me wanted to keep the rumble seat. If I do a T spring, I think I will have one made up from the same width material as the stock A spring which will fit as stock in the cross member and shackles. Interesting that I have not heard from many other AV8 owners about this? I guess it's not an issue for them?
When both spring and shock rate are correct you lower the weight onto the suspension the suspension spring will absorb 3" in my 6" example, when you jounced the car and it didn't respond then the spring rate is probably too great (the other possibility is that the shock is bottomed out) and you'll have maybe 5" reveal, then you can make an assumption. I'd ballpark the rear weight of a raodster at 1200lbs, with 2 attachment points, 1" (measured on the shock, 5" reveal) travel the rate is 600lbs per inch (if it traveled 3" then it'd be 200#), then divide the number of leaves to find individual leaf rate and work the math to tell you how many leaves you need to center the shock. It'll also tell you how much weight you'll need to add if you cannot safely remove springs, the solution is likely a combination of both. You'll still have to recover your ride height.
Spring and shock work will help to some extent but this is a deeper problem common to a great many hotrods...the body is too light in relation to rear axle and wheels, and so at some point cannot control axle movement...a hard thump upwards will lift the entire rig regardless of springs and shocks because the sprung mass is not enough to hold down the unsprung mass when it starts moving rapidly. Adding weight is about as unpleasant an idea as there is for a rodder. Removing weight below is a severe problem for both tradition and wallet reasons. Somebody needs to make a cheap magnesium Model A rear end...or an XKE rear that includes a hologram projection of a '40 quickchange... Lots of texts suggest that unsprung weight of more than 10% of car weigh is undesirable. Add up what's under a 2,000 pound rod and weep.
Thanks Bruce. So all the AV8ers just put up with the bad rear ride? Hmmmmmm Again, I come back to my 32 pickup....there is not much weight back there and I have a very decent ride?
Ever weigh a '32 bed? You have considerably more weight and further aft than with your roadster. Total weight is probably more than 500 pounds greater, with more and thicker metal behind the driver. And very little difference in axle and wheel weight downstairs.
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