04-04-2018, 05:16 PM
Hi Dennis,
I went through exactly this on my Big 7 some years ago, I thought that I had a bent front axle but the problem turned out to be a bent radius arm. However, I carried out the checks that you have been doing while I had the axle apart.
Make sure you know the terminology, there is a good synopsis here: https://www.lespaulsmotors.co.uk/4-wheel...ment-faqs/
The correct figures for the Big 7 are:
Castor angle: 5 degrees
Camber angle: +1 degree
Swivel pin angle: 6.25 degrees
Toe in: parallel to 1/8"
These are from the "Austin Service Journal", page 202, October 1937.
The Swivel axles should have an appropriate "set" on them to give you the correct camber angle, this is not adjustable.
I found that, in common with many 1930's cars, the Big 7 did not have enough castor angle, producing an unsettling lack of directional stability. Apparently, this was done to make the steering lighter at the expense of driveability! With a pre 1936 Austin 7, the castor can be adjusted by making sure the radius arms are set correctly but on the Big 7, this is not possible as they are fixed. I made up a hardwood wedge, inserted between the spring and the chassis to try and force the axle forwards at the bottom and increase the castor angle, which was partially successful. I have heard that some owners have made up a special drop plate to put the radius arm ball joint down lower but I'm not sure that is necessary. In the end, I got the car to handle reasonably well, given the extra weight although by comparison with a Vintage Austin 7, Big 7's are never going to feel good!
Good luck!
I went through exactly this on my Big 7 some years ago, I thought that I had a bent front axle but the problem turned out to be a bent radius arm. However, I carried out the checks that you have been doing while I had the axle apart.
Make sure you know the terminology, there is a good synopsis here: https://www.lespaulsmotors.co.uk/4-wheel...ment-faqs/
The correct figures for the Big 7 are:
Castor angle: 5 degrees
Camber angle: +1 degree
Swivel pin angle: 6.25 degrees
Toe in: parallel to 1/8"
These are from the "Austin Service Journal", page 202, October 1937.
The Swivel axles should have an appropriate "set" on them to give you the correct camber angle, this is not adjustable.
I found that, in common with many 1930's cars, the Big 7 did not have enough castor angle, producing an unsettling lack of directional stability. Apparently, this was done to make the steering lighter at the expense of driveability! With a pre 1936 Austin 7, the castor can be adjusted by making sure the radius arms are set correctly but on the Big 7, this is not possible as they are fixed. I made up a hardwood wedge, inserted between the spring and the chassis to try and force the axle forwards at the bottom and increase the castor angle, which was partially successful. I have heard that some owners have made up a special drop plate to put the radius arm ball joint down lower but I'm not sure that is necessary. In the end, I got the car to handle reasonably well, given the extra weight although by comparison with a Vintage Austin 7, Big 7's are never going to feel good!
Good luck!