General Angle for rear wheels
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General Angle for rear wheels
I would say massively at an angle. 
it straightens a little under load but is meant to have the camber for roadholding, as far as I know.
it straightens a little under load but is meant to have the camber for roadholding, as far as I know.
a couple of suggestions i found
My [very limited] understanding was back then, car dynamics hadn't really evolved into the kind of (fairly) well-understood science it is now. With no real knowledge of weight transfer, etc. etc. it was considered positive camber was better as it got the inside tyre at the 'right' angle when cornering. Later the whole weight transfer thing was worked out, camber thrust, etc. and so negative camber became the norm.
As I understand it roads were more steeply curved in cross section back then, so positive camber would have put the wheels more upright relative to the road surface. In the days before independent front suspension a beam axle could be relied on to keep the wheels at a constant camber angle relative to the road. So having positive camber wasn't necessarily such a disadvantage. For a long-distance road race in the 1900s Mercedes went as far as measuring the crown of the road along the route and set the (positive) camber angles of its cars based on the average curve of the road surface. The idea was that the tyres would be nearly perpendicular to the road surface for as much of the race distance as possible. The Mercedes cars won the race, not necessarily because of the camber settings but probably because of how thoroughly the team prepared.
My [very limited] understanding was back then, car dynamics hadn't really evolved into the kind of (fairly) well-understood science it is now. With no real knowledge of weight transfer, etc. etc. it was considered positive camber was better as it got the inside tyre at the 'right' angle when cornering. Later the whole weight transfer thing was worked out, camber thrust, etc. and so negative camber became the norm.
As I understand it roads were more steeply curved in cross section back then, so positive camber would have put the wheels more upright relative to the road surface. In the days before independent front suspension a beam axle could be relied on to keep the wheels at a constant camber angle relative to the road. So having positive camber wasn't necessarily such a disadvantage. For a long-distance road race in the 1900s Mercedes went as far as measuring the crown of the road along the route and set the (positive) camber angles of its cars based on the average curve of the road surface. The idea was that the tyres would be nearly perpendicular to the road surface for as much of the race distance as possible. The Mercedes cars won the race, not necessarily because of the camber settings but probably because of how thoroughly the team prepared.
I also found a piece that said by using 126 springs which are slightly lower, this can reduce the camber if you tend to drive the vehicle with 1 -2 people only.
You must remember some of the old Triumph's Sean, like the Herald, GT6 and Vitesse. They had pretty positive camber to say the least. As they had a leaf spring at the back, they did have a tendency when cornering at speed to almost collapse in on themselves.
It could be quite hairy to say the least, it happened to me once. The back end hit a bump and as the car was lowered with some pretty hard Koni shocks on it, all the weight went from the back end drive wheels, they tucked themselves in and it came down hard and hit the end stops, the back end just started squirming all over the place. It's one of those situations where if you hit the brakes it will just make it worse, you just have drive through it. But it did scare the life out of me.
It could be quite hairy to say the least, it happened to me once. The back end hit a bump and as the car was lowered with some pretty hard Koni shocks on it, all the weight went from the back end drive wheels, they tucked themselves in and it came down hard and hit the end stops, the back end just started squirming all over the place. It's one of those situations where if you hit the brakes it will just make it worse, you just have drive through it. But it did scare the life out of me.
I sure do Tony, my first car was mk3 spitfire. Great fun but like you said very scary when throwing it into a corner. The front suffered from under steer and the back end would jump all over the place. Seeing as the 500 had independent rear suspension I think they got it horribly wrong.
Things changed with the McPherson strut and they then started to improve handling with caster, camber, kpi etc.
That's why modern cars are so much easier to drive. Not so much fun though?
Things changed with the McPherson strut and they then started to improve handling with caster, camber, kpi etc.
That's why modern cars are so much easier to drive. Not so much fun though?
It's a very interesting question partly because it's such an distinctive feature of the 500. I think I used to know the answer but forgot???!!!
It seems most plausible to me that the answer in a Wikipedia reference to Dante Giacosa when discussing how he designed out the stability problems of a rear mounted engine.
"His answer was to use a semi-trailing arm type of rear suspension that eliminated the large change in the camber of the rear wheels that was inherent with the simple swing axle" suspension system.
Hold on though, maybe that doesn't really answer it?"
My theory:
FIAT seem to have made much about the fact that the car was designed as a four seater and intended it to be used as that.
It would need reasonably strong springing to deal with that but equally it would be expected to handle well with fewer occupants. The spring rating needs to be a compromise for this in all vehicles but the proportion of the weight of the vehicle represented by the passengers in such a light car is sufficiently high that a spring that deals with the loaded weight is going to be excessive in an empty car. By designing in such a wide range of angles for the arms it might have permitted a "softer" spring to be used which still functioned at both extremes.
It seems most plausible to me that the answer in a Wikipedia reference to Dante Giacosa when discussing how he designed out the stability problems of a rear mounted engine.
"His answer was to use a semi-trailing arm type of rear suspension that eliminated the large change in the camber of the rear wheels that was inherent with the simple swing axle" suspension system.
Hold on though, maybe that doesn't really answer it?"
My theory:
FIAT seem to have made much about the fact that the car was designed as a four seater and intended it to be used as that.
It would need reasonably strong springing to deal with that but equally it would be expected to handle well with fewer occupants. The spring rating needs to be a compromise for this in all vehicles but the proportion of the weight of the vehicle represented by the passengers in such a light car is sufficiently high that a spring that deals with the loaded weight is going to be excessive in an empty car. By designing in such a wide range of angles for the arms it might have permitted a "softer" spring to be used which still functioned at both extremes.
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I'm always being asked about the "funny" angle of the rear wheels and I always tell people how it's meant to be like that and will straighten out when a family of six Italians get inside.
But to tell the truth, the nearside rear wheel has always had a bit too much camber and recently seemed mysteriously to be getting worse. It all looked right, with everything sitting correctly and I couldn't see anything out of place. So I dismantled the suspension, removed the spring and measured it; I thought maybe I'd always had mismatched springs. Removing the spring is a doddle of a job and apart from a trolley-jack, no special tools are needed. At 220mm the spring was obviously correct, but I noticed that the chunky, rubber, top seating-ring was a struggle to locate fully both within the spring and inside the welded top-ring under the floor. I decided to fit it without the pressed-steel supporting ring which buffers it against the top of the spring and this allowed the rubber to fit properly.
It appears that this has sorted the problem but I'll keep an eye on it to see if the omission of this small component leads to other issues.
But to tell the truth, the nearside rear wheel has always had a bit too much camber and recently seemed mysteriously to be getting worse. It all looked right, with everything sitting correctly and I couldn't see anything out of place. So I dismantled the suspension, removed the spring and measured it; I thought maybe I'd always had mismatched springs. Removing the spring is a doddle of a job and apart from a trolley-jack, no special tools are needed. At 220mm the spring was obviously correct, but I noticed that the chunky, rubber, top seating-ring was a struggle to locate fully both within the spring and inside the welded top-ring under the floor. I decided to fit it without the pressed-steel supporting ring which buffers it against the top of the spring and this allowed the rubber to fit properly.
It appears that this has sorted the problem but I'll keep an eye on it to see if the omission of this small component leads to other issues.
Attachments
Fiat used to refer to this rubber seating ring as either a Ring or Cushion and called the pressed-steel supporting ring as a Thrust ring
I used to fit these Cushion rings into the Thrust rings first, then fit both together onto the welded top ring under the floor. As these might need to be turned to allow the spring ends to abut the step in the Thrust rings, I sometimes found it helpful to spray the inner portion of the cushion rings with some silicone lube. I think the purpose of the Thrust rings are to protect the cushion rings from damage from the spring, possibly to also locate the spring end securely. Omitting the thrust rings might possibly allow the spring end to shift slightly and cause metal to metal contact resulting in noisy suspension. Some Fiat models also used a shaped/ moulded hard plastic ring under the lower end of the coil spring to presumably prevent wear on the suspension arm/wishbone, possibly also to prevent noise/squeaking.
Al.
If anyone is interested in suspension systems, there's lot's of info available in the sort of textbooks that Apprentice Mechanics/Technicians use in the course of their studies.
(does anyone buy/borrow/read books anymore - not everything can be found on google/youtube ). It's a very interesting subject.
I agree with Peter's theory - long travel suspension with a soft spring rate was the only reasonably viable, cost-effective solution to coping with the widely variable weight loading that a Fiat 500 might have to carry, while remaining reasonably comfortable at all times. The crazy amount of positive camber probably didn't bother customers who were probably just happy to have 4 wheels under them, besides is could be great fun on wet cobblestones
Dante Giacosa could alternatively have fitted additional assister springs that would only come in play when the car was heavily loaded, but there would have been a weight/cost penalty and probably not as comfortable either.
Nowadays, he might have opted for variable-rate springs...
I think he worked wonders with what he had available to him just post WW2.
Al.
(does anyone buy/borrow/read books anymore - not everything can be found on google/youtube
). It's a very interesting subject.I agree with Peter's theory - long travel suspension with a soft spring rate was the only reasonably viable, cost-effective solution to coping with the widely variable weight loading that a Fiat 500 might have to carry, while remaining reasonably comfortable at all times. The crazy amount of positive camber probably didn't bother customers who were probably just happy to have 4 wheels under them, besides is could be great fun on wet cobblestones
Dante Giacosa could alternatively have fitted additional assister springs that would only come in play when the car was heavily loaded, but there would have been a weight/cost penalty and probably not as comfortable either.
Nowadays, he might have opted for variable-rate springs...
I think he worked wonders with what he had available to him just post WW2.
Al.
I'll keep an eye on the rubber ring. It seems to have weathered well over six years; just that it possibly hadn't properly located in the first place. Fitted inside the thrust-ring it squeezed the rubber so that it didn't slip over the centring pressing under the car. I expected the weight of the car to force it home. But thousands of miles' driving didn't do that! The springs have a pretty sedate life so I'm betting it will behave itself
