Hey everyone, Its freakin HOT here on the east coast, at least it is in MD!!! About 100'..... I am getting to the Adjustable Perch's vs Caster just stay with me....during my rant... I've read all the Death Wobble posts, and most of the perch vs. Panhard bar discussions and this is a slightly different discussion. But Pro-Dampener advice is not what I'm after. I dont own a VW. And SO-Cal is a great company built by a legend but.....lets get to that part... I've been driving the hell out of my hot rod slowly working the bugs out venturing further and further from the shop. I havent posted as much as I've wanted, always lurking and checking out others work etc etc...as uploading pics and the whole internet posting thing is kinda new but mostly been cruising and workin on the car so posting updates have kinda lagged.....but with the heat, and kinda working out this suspension issue.... a full updated build of my 34 Plymouth Coupe will be soon to post. The car: 1934 Plymouth 5w Coupe, 4 inch Dropped I beam suspended by split 40 Bones, w/40 spindles, 454 BBC/TH400, 9" w/2.73s (yea non posi ...locker 4.10s soon...) and custom triangulated 4 link suspended by PRO Shocks 200lb Coil overs. I drove the car for the first time on November 15th 2007 and as mentioned have been taking longer trips every weekend. About two weeks ago the problem started. First a little history....When I first drove the car it drove fine but would bottom out on the rear suspenion when you launch the car. I setup the rear suspension as low as I could get it hoping I wouldnt bottom out...well ya build these things and learn...I had everything setup too low. The coil overs in the bottom hole and cranked all the way out. Allowing no "dampening". I then added 5 turns on both rear coil overs which left both shocks about equally distributed, the same amount of dampening. At the same time I moved both shocks up a hole on the coil over mounts, this gained me 2 1/2 inches of frame to axle clearance eliminating the bouncy/rough ride and frame wrap up on the right side during hard accellation and/or when launching the car off the converter. Ok. Well after dealing with fixing the rear and getting the correct shock mounting studs the car drove 100% better and launched hard digging in the right side...100% Contact patch and bites hard. Well as mentioned about two weeks later it brings me to this point. ( I know I ramble but want you to see the full picture) Well about two weeks ago the death wobble started ittermittently. Problem #1 At higher speeds about 65-70 (2300-2500rpm; highway speeds around this area) I hit several bumps and had no problem, minor bumpsteer expected by any straight axle car...till two weeks ago when this whole thing developed. Running 28 PSI in front 32 in rear...note this part.... I hit a bump/asphalt patch during hard accelleration on 97 North, and danced across 3 lanes into a death wobble but it stopped when I came down to about 25 miles an hour... Stopped and checked air. 28 psi. No problems for an hour. Got to my friends house checked everything out and the only thing amiss seemed the both shackles at the perch were starting to push the bushing out...no biggie. Re aligned and retightened everything, put 32 psi in all 4 and Well drove it the next day to a buddy of mine's house an hour in the opposite direction. No problems or nothin...sheer fun. I have noticed that the right front tire seems to level out around 28 psi for whatever reason. Thus I'd been equalizing it all at 28 in front.... We hung out worked on his project and noticed that the drivers side front shock mount had snapped the weld on the bottom of the frame. Instead of thru bolting it I welded Coupling nuts to the frame and then thru bolted them as the bottom mount, thru bolting the frame for the upper hole. So we re welded both coupling nuts on both sides LH & RH and literally stood on em. (used Grade 8 bolts btw) Well partied that night, cruised with him to pickup a project car and then drove home left the DF tire at 28 and for the first half an hour no problem. Then going home I hit a much milder bump and BOOM shackle rock or death wobble what ever you want to call it twice first time at about 55-60 and slowed down it stopped. Happend again slowing for a stop. Getting home I noticed well, the welds were fine but the drivers side shockmount had torn itself free rotating on the single thru the frame bolt mount and snapped the head of the grade 8 bolt off in the coupling nut..... SECONDLY I noticed more of the shackle bushing looked like it was being forced thru the shackle! The shackle looks a little bit like its binding or a twisting forcing the perch side of the shackle to take the load placed on it by the spring. After some research in the R&C archives i've collected I noted solution to my shock mount issues...(50s-current) "A solid bung mounted through the frame and welded to both the outer framerail and inner boxing plate will eliminate the common tendency for the shocks to tear upper shock brackets off the frame when they are bolted thorugh a single thickness of the outer framerail. "(ROD & CUSTOM, November'06; PG 80 , Pic 21) Problem #2 Ok I understand that without shock mounts the spring is free to rock under duress, which can explain as why up untill this point I havent really had an issue. BUT how do I fix whatever is making the bushing do what it is. Caster is the key, I can understand that in having too much caster through the wishbones forcing the spring to bind at the shackle and thus also putting an undue strain on the shock mount that hadn't really been noticed before (ie Possibly due they had been snapped free of the weld and the nuts that were welded to the frame actually were acting as a limiter for the range of motion of the shock mount until fully welded then the bolt could no longer take the strain and snapped thus causing even more wobble than before!! I checked caster angle upon setting up the cross member and it is at 6. Currently the Caster angle of the kingpin inclination is 6. SO there for what is my solution Bring caster back to 0 with the bones....or Do the adjustable dead pearch thing let it roll a bit take some caster out ....???? This is a all round drag and drive car. Drag weekends and still cruise. So it will see the driving and fun show n shines but most of all just having fun!!! Yea the Triangulated 4 link doesnt let me lift the wheels like I want but it does help me plant where I want it...Love to hear from Roothawg or any other racers with Big Blocks/SBs!!!!!!!!!!!!!! I've seen dead perches on several drag cars from the 60s...how does it allow the car to handle on the top end??? transions???? How will Adjustable Dead Perches work!!??? A how to tech perhaps??? I dont have a VW, and So cal makes an awesome product. It has its place. While Panhard bars just add another parrell link that busy's up the front end. 3. BUT How many cars havent had em, 4. How many have bought their "street" rods and didnt like the bump steer and added em. Have they ever checked their caster? in my opinion....Henry didnt put it on em. So on and so on....and in the 60s...if you DO LOOK at the mags...I havent seen many street cars with em and about 2 rail jobs that do. (not saying they werent but .....does the Milner Coupe have one????)..but thats just my .02 on that. Not trying to start the arguing again...just looking for serious caster and perch help not a band-aid discussion. I will fix it the way they did in the 50s and 60s. I'd absolutely love to discuss it with Mr. Chaporis or any of the rod builders hear their real opinion on why and why not and EVEN promote their perch product... Thank you all Look foreward to your help.
Wow, lots of info there. Like Dick S says, every car is different, and each solution, too. I run 6 degrees, too. but I got the swivel perch, but they are tightened solid. I still don't like the rubber shackle bushings. I read somewhere this last year about binding shackles being a factor in wobble. (One of the million factors) And yours have so much strain on them, they are getting pushed around. I've been lubing mine rubber bushings with ATF before every ride and this seems to help the ride. Smoother bumps, less harsh. And helped the wobbles a little. I want to make brass or steel bushings and have grease fittings. Hoping for lesss friction and bind. I'm guessing that youv'e been paying attention to all the other wobble threads with the links to info? Centering the steering box on mine was one of the last things I done, (cause I did not think it was wrong), and that made a big improvement. I needed to shorten the drag link about 1 1/2 inches to get it right. I haven't had a wobble for two weeks now. BUT, this isn't what's wrong with yours. Persistance will get you there. Frank
A "DEAD" perch does NOT use a shackle, used at one end of the spring only and mostly on circle track cars. What you do need is a set of "Adjustable" perches as I see in your pics your spring is in a bind. Thats why the shackle bushings are trying to leave. If you installed your front cross member ya didn't tilt it or not enough. Did the same dumb trick myself. Have you had the front tires spin ballanced ? Check your wheelbase ,both sides equal? One front tire leading the other can cause probs. Is your drag link close to parellel tothe ground? As Frank said having the steering box centered is critical. I've known that for so long I just forget to mention it. And Frank use silicone lube on those bushing,ATF will kill them sooner or later.
From what you said, you had problems in the rear, so this tells me ya' probably have something screwed up in the front too. From the pics, your shackles are in a bind. Get them straightened out so they're parallel. You must be bottoming the shocks out to rip the mounts loose. And, if that happened the shocks are more than likely "toast". The valving doesn't like to be compressed all the way. Actually, higher tire pressure could aggrivate the problem. Stay at 30 or below. I got lost in all your tech info, are ya' runnin' radials or bias? Lower pressure works better with radials. It looks like the spring can make contact with the bottom of your bolt on shock bracket. You never mention anything about your rims. What's the diameter and backspacing (BS)? I've found that anything less (yes, less) than stock rim backspacing can effect the scrub radius that will promote the "death wobble". We used to see that a lot on old oval track race cars. We'd hit a critical speed, usually on the pace laps, and the right front would go crazy. Pick up speed and it would go away. Ya' don't need a swivel or dead perch. Fix what ya' have first. Use a torch and get it parallel, but I doubt this is your problem. Another thought. After ya' raised the rear to eliminate the bind, did you readjust the caster in the front? Straight front axles are simple to set-up. Check all your parts for wear and make sure ya' have 1/16"-1/8" toe in. I've found that the basic stuff is what usually causes a screw-up.
You have forgotten that Henry DID use panhard bars on his buggy spring cars with cross steering...you HAVE to have one on a cross steer car in order to make the car drivable... not my opinion just a fact. Otherwise everytime you turn the wheel the axle moves side to side. A dead perch will do the same thing BUT I don't think it allows for enough spring action to give it a good ride.
Thank each of you for you valuable input thus far... Frank... I will definately check my steering box out and ensure it is square and centered. I belive this is what you mean, also that the arm is centered and equal in its arc of travel. I did setup the car with 1/8th inch toe given for radials. I have not changed that. John.... I have had the front tires spin ballanced, I will double check the wheelbase to ensure both sides equal at this point. I am sure the drag link is parrel to the ground. Mod driver In my hurry to post i did forget some info. I am currently running P215/65R15 Radials on 15x6 Fenton Aluminum Slots with 3 in backspacing. In the rear P255/70R15 on 8 in wide chrome reverse with 4 in backspace (also have run 30x10 15 M/T Radir Cheater Slicks once around the block but will run them when its not raining when I get my posi...lol no need to burn up the slicks one side at a time at this point....) How would backspace affect the scrub line???? Dont get it. Yes I did install my crossmember with 6 degrees caster...built into the crossmember itself. However you do bring up a point I did not consider with the rear higher how so affects the front caster. DOH the Wishbones swing on an arc....with he arch now higher due to the frame...being at a greater angle I made a caster change. (YES the oil pan is low but its a stock '77 truck pan honestly...LOL. thats something else I'm working on lol. to be addressed with a comming 396 build up to be more technically "period" for 63/64/65 with a full pan thats actually the best competition combination.....that gives the most ground clearance oddly enough..) Held up so far and driven it just about 600-800 miles at this point, luckly but looking for a nice 5 quart early vette low profile pan or even a run of the mill 5 qt. car pan....but thats a totally different conversation. The coupling nut is kinda crude but at the time I kinda wanted to A) see if it would work, and wanted to use the factory Plymouth holes for the old shock mounts (as dumb as that may sound) and a buddy said it wouldnt work and tried to prove him wrong. Well seems I should weld the bung through the frame and possibly replace the shocks.......now... well this is how you build your first Hot Rod at 25 and hard headed huh... lol. 2.) the shock mount/nuts do not in any way hit the spring if the spring is compressed to the max. I used a ratchet strap to simulate the downward direction of the spring...While It in NO WAY has the same force as all 1100lb or so of the front end slamming a pot hole or bump....800 or so of that being the damn Big Chevy...trying free itself.... never the less it is clearing the spring. Here I am at MIR (Maryland International Dragway)aka Budds Creek March of this year.
are those soft rubber bushes in the perches? looks like they disintegrated pretty bad. Id rebush with something harder for a start.. I turned mine out of delrin and use poly bush lube on them regularly. check all pivot points including kingpins and make sure they are all really snug, and well greased. Dont kid yourself and say 'oh thats not too bad, that cant be causing it' because it probably is.
Read what I wrote more closely. I didn't say scrub line, I said "scrub radius". Do your homework and you'll find a diagram about it. It's effected by rim BS. See, ya' might learn something today (I try to learn something new everyday!!). By the looks of your car in the blurred pic, I'd be willing to bet this week's pay check that this is your problem. Rims offset to the outside will increase scrub radius. As I mentioned before, we used to see this on our race cars where we had a bunch of offset and wide rims. Take a pair of stock rims & tires that are your bolt pattern, bolt them on and take a test ride. Don't worry about the rears, you're problem ain't there. If you're running a pair of bolt pattern adapters, this will further aggravate your problem. Toss'em, they're junk anyway and scrap is high right now. The Fentons look nice, but if that's the problem, they gotta' go. Remember what I said, the basic stuff is what usually causes problem. Oh yeah, I'm retired, so I don't get a weekly pay check, but if what I tell ya' works, ya' can buy me a beer (maybe several beers)!!!!!!
Scrub radius is an imaginary line through the verticle center line of your tires If it's too far outside of your king pins it increases the effort required to steer the car... and it places a lot of load on your suspension. If you have "zero scrub radus" you should be able to turn your steering wheel with your little finger. It looks like you also have a cross steering set-up... you have to have a panhard bar...
Where did the shackles and bushings come from ? Definitely look different from my P&J shackles. Those bushings look too soft. Don't worry about swivel shackles,leaf springs can twist. Get the basics under control.
You made life too EZ on him. Let him look it up . Stock '35-'40 Fords have cross steering and no panhard rod. They work OK so long as your shackle angles are correct. I think Henry added that bar in '42. Yes, it was an improvement, but not totally necessary.
Spring on top of axle ,as long as the shackle angle is correct, does not need a panhard bar/rod. My does not have one and no issues to require one. Correct the twist in the spring/shackle and replace with a harder bushing. I too made up some delrin/nylon ones.
Lets do one issue at a time. First the relationship to your perch pin shackle eye and the angle that the spring shackle eye is positioned in is incorrect. If you welded the front cross member in 6* rearward and did not have the frame level, then the difference from level is what the front cross member was installed at. This shows up when you install the front spring. If you sight the front spring eye to the front perch eye, you see that they are not parallel. This produces a twist in the spring that magnifies during flex. HAS TO BE ADDRESSED. Simplest way out is to install adjustable perches. They will self align the spring to the caster of the axle/radius rod and what ever the angle of the front cross member who cares. Fix this first and while your at it get a good shackle kit not one with the mickey mouse rubber bushing kits. Next issue is braking shock mounts , bolt or tearing out frame sections. This only happens when you are continually topping out or bottoming out a shock. The shock is a flexible link, if the brackets are breaking the are under a strain of some kind due to obstruction or misalignment, so you have to figure out what is happening and your shocks have to be positioned so that they have at least 3" of compression and extension. If you don't have that you have the wrong shocks or mounting them incorrectly. The last quick observation for now, is that you need a panard rod and with out going into a big engineering discussion, just install one.
I agree with everyone else... You've got a serious problem there with the angle of your spring/ front cross member versus the angle of your front axle/ wishbones. Everything should move in a straight line. I would also try to get the same amount of caster on those shocks as your front axle.
Stock '35-'40 Fords have cross steering and no panhard rod. They work OK so long as your shackle angles are correct. And you don't have a big block and big contact patch on your tires and don't ever drive it hard and you don't mind that weird feeling when you go around a sweeping curve and the axle shifts on the shackles over so slightly and your asshole puckers up and tries to eat the seat!
Well now, another case of someone thinking I don't know shit . But I've been there, I've done it and intend to keep on doin' it, even though some motor mouths think they know it all . If I didn't do it, or don't know what's technically correct, I'll keep my mouth shut and let those who really know provide the answers. So, Look"ie" here, what do we have that's pertinent to the discussion of this thread ???????? My '40 Ford Coupe oval track race car with a '37 hood. Uses a stock '40 Ford frame. A '40 Ford straight axle, transverse front spring with shackles at the correct angle. Cross steering using a GM Saginaw 525 box with Corvette quick ratio internals. BIG heavy big block Ford FE engine. BIG W i d e ASS tires. AND ....... operates at a high rate of speed while going around sweeping curves, large and small radius, flat and banked, on both dirt and asphalt race tracks. Oh yeah, I almost forgot. No panhard rod . When behind the wheel racing, I don't seem to remember my asshole puckering' up because of any erratic vehicle behavior caused by the dynamics of shackle shift. As a matter of fact, it's won many races against cars with independent front suspensions with rack and pinion steering. Our HAMB buddy, Dick Spadaro, has driven this car and remarked how well behaved it was. Even though Dick might say use a panhard rod, if I refresh his memory about this driving experience, he might rethink his statement . And the best part of all, we survived and had a blast doing it .
Limeworks has an oillite bushing for hotrod style shackles. I think they are designed to replace the common urethane bushings in most hotrod shackles. See if they come in your size.
What Dick said about the adjustable perches is right on. Don't try and make the spring flex, it just eats the bushings as you have found out. DO NOT use a dead perch. I found out the hard way that they cause the axle to move laterally back and forth during bump and rebound. They also cause the spring to effectively stiffen considerably. I do think you will appreciate the Panhard bar on a street car that encounters bumps, pot holes, road grooves etc.
I have been building and driving hotrods for many years, all with 4" dropped axles, transverse front spring, and aircraft type tubular shocks. I always install a Panhard rod immediately behind the front axle so that it doesn't show, and I use conventional, non swivelling spring perches. I set the front crossmember at 6 degrees like you have yours, and I (mostly) always use a 4 link style of axle mount (as opposed to a split wishbone). All of these cars have been great drivers, with no bump steer (use a Vega cross steer box), and no deathwobble. I have never used a steering dampener, and I have never seen rubber bushings squeeze out like that. You have a bad bind in your system somewhere, to make your car act like that. You may have to heat and bend or cut and weld the end of your wishbones so that the kingpin inclination of the axle sets at a true 90 degrees to the underside of the front crossmember. I hope that you have some length adjustability where the trailing end of your wishbone is anchored to the frame.---.---Brian
The bulk of the posts here, including my original one, have centered on the shackles, spring not in alignment with the perch and no panhard rod. None of the above will not cause the symptoms of his problem. I still contend the problem is with his rims and scrub radius. There's a lot of old Ford and hot rods runnin' around out there that have shackles in a bind and no panhard rod that don't suffer from the dreaded "Death Wobble".
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