Technical Front tire wear.

[AndersLS]

Hello forum. I am redoing all the bushings/shocks/spindles on my 69 500F. Prior to all this work, my tire wear was as is pictured. Outer tire wear. Both sides are pretty evenly worn. The wear feels smooth to the touch. I have a feeling the camber is off.
If it was toe-in, the wear would feel rougher to the touch.
What do you fellas say?
If the camber is the culprit, I will remove a couple of shims from the triangle mounting bolt, to get less camber. Ideas welcome. Thanks.

 

[bugsymike]

Hello forum. I am redoing all the bushings/shocks/spindles on my 69 500F. Prior to all this work, my tire wear was as is pictured. Outer tire wear. Both sides are pretty evenly worn. The wear feels smooth to the touch. I have a feeling the camber is off.
If it was toe-in, the wear would feel rougher to the touch.
What do you fellas say?
If the camber is the culprit, I will remove a couple of shims from the triangle mounting bolt, to get less camber. Ideas welcome. Thanks.
View attachment 410672

Looking at the photos I tend to agree re camber, as you say and if it doesn't feel rough as though feathering to one side or the other unlikely to be be tracking or racing through the bends .Just a thought the rear springs are not weak as if the rear is sagging it will through out the front, so would need correcting first.
I used to have a Dunlop castor, camber and KPI gauge but sold it on through lack of use.
You should be able to get an idea of the camber using a reading from a spirit level top to bottom ideally at the rim rather than the tyre and on flat level ground.
Another way is to hold a plumb line from the top edge of the rim and see how far it is off at the bottom.
I used to try for a small amount of Negative Camber which helps cornering. If you see pictures of older cars when hard cornering the outside wheel often looks like it is tucking in.

 

[AndersLS]

Both rear shocks were defective…….the springs seem fine. I have changed all the shocks.

 

[the hobbler]

Looking at the photos I tend to agree re camber, as you say and if it doesn't feel rough as though feathering to one side or the other unlikely to be be tracking or racing through the bends .Just a thought the rear springs are not weak as if the rear is sagging it will through out the front, so would need correcting first.
I used to have a Dunlop castor, camber and KPI gauge but sold it on through lack of use.
You should be able to get an idea of the camber using a reading from a spirit level top to bottom ideally at the rim rather than the tyre and on flat level ground.
Another way is to hold a plumb line from the top edge of the rim and see how far it is off at the bottom.
I used to try for a small amount of Negative Camber which helps cornering. If you see pictures of older cars when hard cornering the outside wheel often looks like it is tucking in.

If you have a standard 500 (as against a lowered one) the front wheels have quite a bit ot POSITIVE camber. I don't have a proper camber-tool, so I made one using a flat pieceof steel which just sits on the top and bottom of the wheel rim and a spirit-level with a moveable degree-gauge built into it/ I will be back home tomorrow, and if nobody else has come up with the camber angle, I will look it up and let you know what it should be. You are unlikely going to be able to achieve negative (or even '0') with the standard road spring---I don't think that you can remove enough spacer-distance from behind the wishbone mounting 'yoke'.

 

[bugsymike]

If you have a standard 500 (as against a lowered one) the front wheels have quite a bit ot POSITIVE camber. I don't have a proper camber-tool, so I made one using a flat pieceof steel which just sits on the top and bottom of the wheel rim and a spirit-level with a moveable degree-gauge built into it/ I will be back home tomorrow, and if nobody else has come up with the camber angle, I will look it up and let you know what it should be. You are unlikely going to be able to achieve negative (or even '0') with the standard road spring---I don't think that you can remove enough spacer-distance from behind the wishbone mounting 'yoke'.

The original Dunlop Caster, Camber and King pin inclination Gauge I had came in a box like this photo (s/h empty box now advertised on eBay for considerably more than I sold my complete kit for, doh! ). There are simple magnetic Camber gauges advertised on eBay for around £10, though I would question their accuracy as they show them with the car jacked up and stuck against a brake disc (not Fiat drum) and most important we always checked correct alignment with road wheels sat on level ground so suspension at a working position .
As the hobbler said regarding lowering springs, ride height will seriously effect steering geometry.


.

 

[AndersLS]

Thanks for all the great info. My car is not lowered or modified in any way. The rear springs are the originals. Maybe its time to change them..?
I will remove a couple of spacers each side from the front wishbone mounting bolt.

 

[bugsymike]

You mentioned changing the rear shocks when I said about rear springs early, it is possible the poor shocks have weakened the rear springs making it a little lower at the back, so in the same way a vehicle weighed down at the back will throw the steering geometry out. This would increase wear on the outside of the front tyre tread due to increasing the positive camber effect.

 

[the hobbler]

You mentioned changing the rear shocks when I said about rear springs early, it is possible the poor shocks have weakened the rear springs making it a little lower at the back, so in the same way a vehicle weighed down at the back will throw the steering geometry out. This would increase wear on the outside of the front tyre tread due to increasing the positive camber effect.

As promised when I got back home (which I am now)---camber on the 500 is 1 degree +/- 20' of POSITIVE camber (wheels leaning OUT at the top). Caster angle (aka King pin inclination) is 9 degrees +/- 1 degree. Unusually, the 'book of words does not stipulate what weight should be inthe car for these measurements. However for 'toe-in' measurement (0 to 2mm---I always go for the '0' measurement), the workshop manual (factory) says that (a) tyre pressures should be set at 17psi (front) and 26.3psi (rear) and the car and the car should be in a "static load condition,or with an orderly load of four passengers" NOTE, an ORDERLY load, NOT DISORDERLY!!

 

[AndersLS]

Thanks. Great info. 17psi front pressure…..thats not much….I have 25psi now….ORDERLY..understood!

 

[bugsymike]

As promised when I got back home (which I am now)---camber on the 500 is 1 degree +/- 20' of POSITIVE camber (wheels leaning OUT at the top). Caster angle (aka King pin inclination) is 9 degrees +/- 1 degree. Unusually, the 'book of words does not stipulate what weight should be inthe car for these measurements. However for 'toe-in' measurement (0 to 2mm---I always go for the '0' measurement), the workshop manual (factory) says that (a) tyre pressures should be set at 17psi (front) and 26.3psi (rear) and the car and the car should be in a "static load condition,or with an orderly load of four passengers" NOTE, an ORDERLY load, NOT DISORDERLY!!

When we used to do steering geometry checks with the Dunlop kit I mentioned earlier , it was three separate operations, as in Caster, Camber and King Pin Inclination:-
Caster angle, similar to KPI, causes the wheel to rise and fall as well. However, dissimilar to KPI, the effect is opposite from side to side. Therefore, with symmetric geometry, the effect of right steer will roll the car to the left causing a diagonal weight shift.

Followed by wheel alignment (tracking) it was in the 1970s on Russian Lada cars(Fiat 124 under license) and we had to get quite proficient at the time as from brand new they could scrub out a set of front tyres in 600 miles, I kid you not! The steering could be so heavy we used to joke you could recognise a female Lada driver due to the similarity to a Russian Olympic shot putters arms! PC not being heard of in workshops in the 1970s
They could be made to handle reasonably well, even adding a little negative camber.
I recall on a Lada Course at the importers in Bridlington on an airfield five of us including a lecturer doing 80 mph down the unused runway after comments about the handling, he suddenly locked the steering right round so we were going in a circle and he calmly said we are on three wheels now, to which we all replied "bo**ocks, so he still at 80 with his foot hard on the accelerator he straightened the steering and we all felt it drop down on the ground!
In passing I would say not on Russian tyres and they did have a local Rally Team!
On Russian tyres road testing in the wet when cornering, a basic understanding of the principals of "cadence braking" before ABS became available was an advantage

 

[fiat500]

Thanks. Great info. 17psi front pressure…..thats not much….I have 25psi now….ORDERLY..understood!

It's so low that it's hard to trust most inflator gauges. I bought an analogue tyre gauge designed and sold for use with light aircraft......I figured that might be accurate. As Tom has said, there are specific instructions for setting the toe of the steering. Before messing with any other setting, I would get to grips with that. You'll be surprised at how much the measurement will change according to the weight in the vehicle. Also worth checking the play in the rear wheel-bearings as these can affect the precision of the steering and by inference, possibly the tyre wear.