Last weekend i finally got my '31 A Roadster on the street for the first time for a test drive and in addition to the scary power of the thing i encountered even more scary front wheel shimmy at speeds around 30 mph. After reading through many threads here i am sure that one of the reasons is the considerable wear/clearance of the kingpins/spindle bushings. Therefore i have decided to overhaul them. As it is not that easy/fast to get parts for this car over here i would like to order the correct parts the first time round and not have to wait for weeks for new parts when i discover during installation that i bought the wrong parts... I am pretty sure that i have the stock 31 Model A axle on the car and i have 39 Lincoln juice brakes with (i ***ume) 39 Ford drums. However i am not 100% sure (except for the backing plates/brakes - those i installed myself), therefore i would highly appreciate it if someone more knowledgeable than me could tell me what kingpin overhaul set (for which years) i should order to get it right the first time... Furthermore a recommendation where best to order the required parts would also be helpful (maybe some Alliance Vendors carry the parts?). Thanks Helge
That looks like a round back spindle, '37 and up and the bushings etc may be the same as squareback spindle - that'll give you the new kingpins, bushings and bearing. I'd order from **** Spadaro, here on the hamb...he is topnotch and will make sure you get the right stuff the first time. You'll probably need a reamer as well, he has the highest quality reamers. The other thing you need to check is how tight the kingpin is in the axle itself, they get loose and then open up around the top - no bushing for them. To resize the axle i heat with oxyacetalyne. I take an old kingpin, turn it down a couple thou in a lathe. I heat the axle end and dip it into a bucket of hydraulic oil, repeat several times until the undersize kingpin starts to tighten up (you are shrinking the axle when douseing it in the oil), the top and bottoms can still be overly large, i heat to cherry red and take a ballpeen to the flange around the hole at top or bottom and beat it in against the undersized kingpin and it'll snug right up. Then you use that reamer you got from **** to bring it back out to the new kingpin size. The important thing about the reamer you get from him is that when doing the spindle the reamer is aligned by the other hole so he upper and lower holes are true to each other, i have lesser quality reamers that just do the individual holes independant of each other...bad ju-ju there. I hope i helped a little. Its a fun job and it'll actually work.
Plenty of threads on this topic. http://www.jalopyjournal.com/forum/showthread.php?t=247360 Oj's got it about the piloted version of the reamer, it works best. And Spadero's the guy!
It appears that you have a Model A axle with 37-41 spindles, the king pins are the later style since Model A kingping have a brake rod that runs through them. Usually if you have bad kingpins they will cause the steering wheel to shake and quit as you slow down.The king pins for 37-41 are different than 42-48, the diameter is the same from 28-48 but there are differences in the length. Your kingpins have a gap above the spindle and I can't tell if there are shims between the axle and spindle which could cause movement. The easiest way to check for wear is to jack the car up and try to move the top and bottom of the wheel towards the axle, it should not rock back and forth. The drag link and tierods can also cause problems.
Measure the front & back of the front tires. Make the front 1/4" to 1/8" narrower. Also check if the steering loop nuts/lock washers are sitting flush against the backing plate, inside the drum, & NOT caught on the lip of the 3" centering ring of the spindle.
That don't look like any of the model A axles I've had... looks more like a 33-6 axle. A axles don't have a curve from the wishbone mount to the kingpin boss like that, they are pretty straight.
Yes, that is a 33-36 axle with 37-41 spindles. Order up a 37-41 king pin kit. The bushings are a press in and then must be reamed to size. You'll need to either buy, or find someone with an adjustable reamer that has a centering extention on it to keep the bores in line. If you have a good local machine shop, they probably have a reamer and can do it for you. Do a quick search and you should be able to find an example of someone doing this as well as the correct size of reamer needed.
Thanks for all the great tips. First I will tackle the kingpin issue (already tried to contact **** Spadaro), then i will measure the toe-in, wheelbase etc... I Think i would not hurt either to replace the quite old and already partly cracked bias-ply front tires... Helge
quite old and already partly cracked bias-ply front tires, are the only kind of bias-plys I run. Sometimes new bias-plys can bounce. They do ride the road groves & perform horribly but wont really cause "shimmy"
X2 on the axle observation and man that front spring you are running sure looks sturdy to say the least...
Do you have 7 degrees or so of caster? The pics seem to show less. The rear end of the split 'bones appears to be too high up on the ch***is. Lumpy or "twisted" tires can cause your symptoms too. Sometimes a tire will cause it with no apparent reason. Slack anywhere in the steering also a prime cause. Your kingpins don't look loose in the pics, everything looks lined up between the spindle and axle bosses. That doesn't always mean much, but I'd be surprised if they are really loose. Even loose wheel bearings can do it. If nothing else works, try a different set of tires. Some brands just don't like being on an I beam axle.
@ Sawbuck: So far i do not run any shocks at all on the front...i would like to try getting the car driveable without them...if nothing else helps i have to think about how/where to install some front shocks... @ R Pope: So far i did not check the caster...it is on the to do list. There is definitely clearance at the spindles - i can move them at lest 1-2 mm on the kingpins when i move the upper/lower part of the wheels left/right. I measured the toe in and it is at almost zero...doesn't help either. So, quite a bit left to do... Helge
I don't see any wheel weights on either wheel. Have you had the tires balanced? Even with old tires you should have the tires balanced and that may help a lot. You also need some sort of working shock absorber. On the king pin bushings you can have a machine shop fit the bushings to the pins with a hone that is used to fit connecting rods. The cost should be a whole lot less than buying and shipping a reamer that you may use only once in a lifetime.
To much airpressure in that kind of tires can make them horrible. Try with 0.7-1 bar if you have more.
Another thing to check is the steering box. I run a F1 box that has been fully rebuilt by a guy that has built literally hundreds of boxes, drove fine but with 4 1/2 turns lock to lock. To correct it myself and a mate fitted a longer pitman arm,in doing so got the centre of the box slightly out when we refitted the drag link this in turn caused a couple of wobbles. Today got the tracking, toe in checked and corrected, then found the high spot in the steering box (informed it is always directly in the centre of the box), fitted the pitman arm at the 6 o'clock postion and finally adjusted the drag link length to connect the pitman arm to the steering arm on the back of the front hub. Just about everything can add to or directly cause wheel wobble, keep plugging away and you'll resolve it.
Check out all tie rod and draglink ends by shaking hard to see if anything can move without moving the other part it attaches to while you are doing this. I believe you almost certainly have '35-48 Ford type ends, though I can't see them.
Thanks to all the tips here I have the problem solved now... I renewed the kingpins (including bushings), slightly increased the toe-in, lowered the tire pressure to about 20 PSI and additionally installed a SoCal steering stabilizer... In one of the few rain brakes with dry roads we had two days ago I test drove the car and have to say it is a completely different thing: No more wobble or shimmy on the front wheels, smooth running even over bumps in the road and all in all much more pleasureable to drive (still a bit scary, but that is mostly due to the Pontiac TriPower characteristics...). I still have not balanced the front wheels (no weights on them at all?) but will do so tomorrow and see if the slight vibrations at speeds over about 45 mph will vanish then. I think the major problem were the badly worn kingpin bushings and i can only recommend to renew them if there is any wear on them - and easy job and great improvement! Helge
The Jalopy Journal
