0 deg. caster - what affect of front braking

[Tom Bellfoy]

The Les Andrews book states the Model A Ford should have a 5 degree caster.
A couple of us guys are trying to diagnose a model A problem with a friends car, we all have a fair knowledge of the Model A and its workings.

problem is when the stock brakes are applied the front end goes absolutely volatile by jumping all over the place.

We are likely looking at some loose parts and steering box in need of rebuild, however we also believe the front axle may be bent.

I've read a few posts on the bent axles so far but was wondering how to check the caster angle while the axle is attached to the car and if there was no caster at all what affect would this have on braking.
We'll als be checking the camber angle

thanks for your input

[heneste]

You can check the caster angle using a magnetic degree indicator (basically a protractor dial gauge that's magnetic at the rear). Or, you could do a crude approximation if you know the height of the axle (direct vertical measurement, call it "A") then take a straight edge and run it parallel,against the axle and measure that distance (call that "B"). The cosine of the caster angle should be measurement A divided by B.

Too little caster and you can get a wobbly wheel (like a shopping cart with a bad wheel)

[Tom Bellfoy]

Steve:
I just read another post which referred to Les Andrews book on how to measure the caster, found it in the book. When measuring the caster and camber angles tomorrow we should be able to determine if the axle or wishbone needs some attending to.

[Joe K]

If the front axle is bent 9 times out of 10 it is the axle segment "outboard" of the spring perch which is "pushed back." Mostly this happens on the passenger (right) side as drivers attempt to pull over into the rough road margin or hit a curb.

This "push back" can be compensated for in toe-in - provided that the wheel is only pushed to the stern and not "twisted" as part of the damage. Twisting can certainly happen, particularly if the wheel is locked up (braking) during the hit.

The only true check of a front axle is done with the axle "out" of the car and disassembled, and a check done with Bear alignment rods.

Here are the rods in use on a Model T axle. KRW had an equivalent system - and Bear might have been the name for KRW rods being used by the Bear Franchise.



The rods are not hard to make. The worst part is getting the axle "demounted" in order to do the test.

You might do better to get another axle and start fresh? My last axle bought in 2016 at Castaway Farm Antique Auto Swap I paid $20. Includes kingpins/spindles but no wishbone so half the disassembly was done.

Joe K

[Joe K]

Yunno, I'm going to correct my statement "the only true check."

You can do a check using only the outermost two rods - and a construction level.

And remove your kingpins and spindles to get to that elusive kingpin seat and place the rods and make a measure with your level and a ruler. All done underneath your fender with the car at level on a single jack.

Um. Maybe my first suggestion would still be best. Slugging out kingpins is not my idea of fun and most of us don't own the KRW kingpin "pusher tool" to do it best.



And then what do you do if you find the axle bent?

You're back to my suggestion.

Joe K

[Arlyn Bieber]

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After rebuilding close to 100 front ends, here is my opinion and experience. 90% of the axles are bent. 90% of the steering boxes are worn out, 90% of the steering balls are egg shaped. Half the radius rods are bent. Bit the bullet and remove the entire front end and totally disassemble and totally rebuild which is straighten axle, radius rod, and tie rod. Remove steering box and replace all parts including the worm which often times looks good but after 85 years of wear it isn't. Replace king pins and bushings. Replace the steering balls if they are out of round more than 0.020". If the front spring is sagged replace it along with the spring hangers. Replace the wheel bearings and RACES. Set the toe-in at 1/32". Assemble everything and you will be amazed how nice the Model A steers. You don't need later Ford steering boxes or shortened pitman arms etc. The original Ford design works extremely well. Also don't forget the tires. Keep in mind you get what you pay for in tires. Goodyears are the original size and the best out there and keep them aired to 35 psi. Just my thoughts.

[Patrick L.]

I guess my first question would be to ask how the car handles ? If the car handles well then maybe the problem is with the brakes. But, Model As handle pretty well with some front end troubles.

Most vehicles need positive caster angles. Smaller caster angles allow the steering wheel to return after turns while higher caster angles tend to improve higher speed handling. I don't think Model As need 5º of caster, but, they do need some. These cars were built in the early days of the builders figuring out this front end geometry stuff.
These cars certainly don't need as camber as Mr Ford wanted at the time, but, thats not the issue of this thread. It was during this period that Mr Ford figured that these didn't need as much toe-in as first thought, dirt doesn't care much but pavement does.

[Jerry in Shasta]

To answer your question, ever get a shopping cart with wobbly wheels? That's what the lack of caster will do.
JB

[Patrick L.]

I've not seen a shopping cart with brakes. Thats not to say some may have them though. [smiley face]

[SeaSlugs]

Originally Posted by Tom Bellfoy

The Les Andrews book states the Model A Ford should have a 5 degree caster.
A couple of us guys are trying to diagnose a model A problem with a friends car, we all have a fair knowledge of the Model A and its workings.

problem is when the stock brakes are applied the front end goes absolutely volatile by jumping all over the place.

We are likely looking at some loose parts and steering box in need of rebuild, however we also believe the front axle may be bent.

I've read a few posts on the bent axles so far but was wondering how to check the caster angle while the axle is attached to the car and if there was no caster at all what affect would this have on braking.
We'll als be checking the camber angle

thanks for your input

Do the brakes seem to grab? If its grabbing it could be locking up a wheel or attempting to with warped drums. Is the spring to crossmember u bolts tight as can be? Is the center bolt broken (common)? shackles worn out? When supported by the axle and tires off the ground how much wobble do the wheels have and where when shaken from 6 and 12 positions? What about 3 and 9? Do the wheels roll true?

Is it posible to have someone drive it while another person in another car next to them watches to see what happens when the car in question brakes?

[larrys40]

Originally Posted by Arlyn Bieber

After rebuilding close to 100 front ends, here is my opinion and experience. 90% of the axles are bent. 90% of the steering boxes are worn out, 90% of the steering balls are egg shaped. Half the radius rods are bent. Bit the bullet and remove the entire front end and totally disassemble and totally rebuild which is straighten axle, radius rod, and tie rod. Remove steering box and replace all parts including the worm which often times looks good but after 85 years of wear it isn't. Replace king pins and bushings. Replace the steering balls if they are out of round more than 0.020". If the front spring is sagged replace it along with the spring hangers. Replace the wheel bearings and RACES. Set the toe-in at 1/32". Assemble everything and you will be amazed how nice the Model A steers. You don't need later Ford steering boxes or shortened pitman arms etc. The original Ford design works extremely well. Also don't forget the tires. Keep in mind you get what you pay for in tires. Goodyears are the original size and the best out there and keep them aired to 35 psi. Just my thoughts.

Arylen,
I agree with your assessment and experience.... I have rebuilt I'm sure at least the same in numbers and although i haven't seen as many axles as bad as wishbones bent or other damage. You stated it perfectly!
Agree that you don't need shortened pitman arms etc.. as with the front axle and steering gear properly rebuilt they do well and perform as was intended. I do prefer the firestones as I like the way they look and steer.. just my preference and they are both good brands .
I remember when Terry Oberer had his tudor done and he was perplexed at how hard it steered, even doing everything right.... I said get those crappy Garfields off there and put on new set of Firestones. He coudln't wait to call and tell me he now had "power steering".

Made a world of difference. The garfields wear like iron but steer harder than any other tire. Figured knowing Terry you would appreciate that.

All the best to you on the crazy left coast!
Larry

[Tom Bellfoy]

We just checked the caster according to the Les Andrews book. The drivers side has about a 2 degree positive caster and the passenger side is on the negative side (the mark goes back .375 inch) so that would be a negative caster but how do you math guys turn that figure into a degree of negative ?

The wishbone seems to be perfectly straignt and the camber on the drivers side looks to be about 5-10 degree out.

Me thinks we'll have to get straightened out.

Any input ?

[Ron in Quincy]

Camber is 7 degrees, built into the spindles. A easy way to check: park "A" on level cement, using a steel carpenter square, lay short side on edge and move toward backing plate on each side, square should touch top of backing plate but not the bottom, the difference at the bottom should be 7 degrees on each side, if one side has no camber it indicates a bent axel, this condition will give excessive shimmy.

Another condition that creates a problem is not having a 25 percent load on the tie rod and drag link springs at each end, if not it adds excessive play in the steering wheel and wobble in the front end: to check this, with wheels on the surface have one person move the free play back and forth on the steering wheel while another person watches the tie rod and drag link ends for any movement, if there is any movement tighten the plug end until there is no movement.

When you have check these two items and if any changes made, be sure to set the toe in on the front wheels.

Ron

Another item on the front axel that can cause hard steering are the king pin bearings, these are a load bearing, with the wheels setting on the ground you should not be able to turn the bearings, if you can turn the bearing you need to add shim or shims to the top of the axel so the load is on the bearing.

I have assumed that the balls on the steering arms and pitman arm are round and not egg shaped.

[Ron in Quincy]

BTT, see additional info on my post

[Jerry in Shasta]

Originally Posted by Patrick L.

I've not seen a shopping cart with brakes. Thats not to say some may have them though. [smiley face]

Bet you never saw a 440 magnum shopping cart either.
HEHEHEh

[Floats]

Hi Guys,
Down load a free app called angle pro. It will change your cell phone or Ipad into a digital inclinometer in minutes.
Regards
Chris

[Mike V. Florida]

Originally Posted by Arlyn Bieber

After rebuilding close to 100 front ends, here is my opinion and experience. 90% of the axles are bent. 90% of the steering boxes are worn out, 90% of the steering balls are egg shaped. Half the radius rods are bent. Bit the bullet and remove the entire front end and totally disassemble and totally rebuild which is straighten axle, radius rod, and tie rod. Remove steering box and replace all parts including the worm which often times looks good but after 85 years of wear, it isn't. Replace king pins and bushings. Replace the steering balls if they are out of round more than 0.020". If the front spring is sagging, replace it along with the spring hangers. Replace the wheel bearings and RACES. Set the toe-in at 1/32". Assemble everything and you will be amazed how nice the Model A steers. You don't need later Ford steering boxes or shortened pitman arms etc. The original Ford design works extremely well. Also, don't forget the tires. Keep in mind you get what you pay for in tires. Goodyears are the original size and the best out there and keep them aired to 35 psi. Just my thoughts.

You're my hero!

[Patrick L.]

Originally Posted by Jerry in Shasta

Bet you never saw a 440 magnum shopping cart either.
HEHEHEh

Can't say I have, but, would like to. I think I'd keep the engine and throw away the cart. I've got a thing for Chrysler RB engines.

[Mike V. Florida]

Originally Posted by Jerry in Shasta

Bet you never saw a 440 magnum shopping cart either.
HEHEHEh

Originally Posted by Patrick L.

Can't say I have, but, would like to. I think I'd keep the engine and throw away the cart. I've got a thing for Chrysler RB engines.

Might be a 440 ;