Positive camber on old cars.

[rhinochopig]

Why is this? When you see road and race cars up to about the late 40s, they all had quite extreme positive camber at the front. Why was this - limitation of steering geometry or something? It can't have been a good thing as surely it reduce tyre contact during roll.

eg.

[J4CKO]

Our Fiat 500 has it at the rear, always thought it was to compensate when people got in as it sort of levels out.

[VeeFour]

I think it's something to do with cross-ply tyres.

[Magic919]

Or ease of steering.

[Pints]

The VW Beetle was atrocious for this IIRC.

[RenesisEvo]

rhinochopig said:

Why is this? When you see road and race cars up to about the late 40s, they all had quite extreme positive camber at the front. Why was this - limitation of steering geometry or something? It can't have been a good thing as surely it reduce tyre contact during roll.

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.

Pints said:

The VW Beetle was atrocious for this IIRC.

Swing-axle suspension has horrific camber control, especially when load is reduced (e.g. when braking!).

[fourwheelsteer]

RenesisEvo said:

rhinochopig said:

Why is this? When you see road and race cars up to about the late 40s, they all had quite extreme positive camber at the front. Why was this - limitation of steering geometry or something? It can't have been a good thing as surely it reduce tyre contact during roll.

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.

[rhinochopig]

fourwheelsteer said:

RenesisEvo said:

rhinochopig said:

Why is this? When you see road and race cars up to about the late 40s, they all had quite extreme positive camber at the front. Why was this - limitation of steering geometry or something? It can't have been a good thing as surely it reduce tyre contact during roll.

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.

Thanks for the info. In a similar vein regarding Merc preparation, weren't the Merc race colours derived from them not painting their GP cars to save weight.

[JR]

rhinochopig said:

Thanks for the info. In a similar vein regarding Merc preparation, weren't the Merc race colours derived from them not painting their GP cars to save weight.

No, urban myth.

[RenesisEvo]

fourwheelsteer said:

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.

Interesting point, thanks for your post.