Why different spring lengths?
 

I keep seeing Model A front springs from 29" to 31.5", I thought the Model A axle where all the same width from perch to perch pin. Are there different shackle lenghts? Where would you use the 29"?

Re: Why different spring lengths?
 

Think the difference you are seeing is the amount of sag they have. Rod

Re: Why different spring lengths?
 

Some aftermarket dropped axles are narrower, made for those that build real low hot rods with fenders. Some narrower axles have perch holes with a closer spacing. Using a front spring with too long a main leaf, or even a worn out original spring, will cause the shackles to go toward the vertical and potentially the spring might strike the axle.