Model a rear crossmember question

Ok, I have tried searching for this without much luck. I am building a model t modified on a model a frame, and am in the process of finishing up the rear kickup. The stock crossmember has a certain degree of caster (off the top of my head I think it was around four to five degrees). Now I understand why the front axle has that caster but why is it necessary for the rear? The reason I ask is that I haven't final welded the rear crossmember in. At this point it would be easy to angle the crossmember to take the caster out. Would this be a good idea or is it better to leave the caster in there? If it helps any I am using a model a spring and custom made spring perches on a 9".

 

An excellent question, I am using a Model A rear spring on a 40 rear. I am using a bulldog or suicide type perch welded to rear crossmember. Should I be angling my mount forward like a stock crossmember?

 

I believe you are talking about caster not camber. the front has a 4% lean to it to make it go straight down the road. camber would be how much the tires are leaned inword at the top. I don't recall the rear crossmember on my A being anything but straight so when a spring is bolted in, its perpendicular to the frame. See third pic down on my web page >>> http://www.brkdnc.net/****/****.html

 

There isn't any angle built into the rear crossmember unlike the front. The rear spring runs true straight up and down.

 

You are absolutely right, I meant caster not camber. I edited the original post. Maybe it changed depending on the year. My frame is a 1929 and it definitely has some build in caster. Maybe mine is just bent or something.

 

To my knowledge the Model A rear crossmember mounts flat to the rail, I dont think there is any "tilt" to it. You would weld your spring perches to the rear end housing with the pinion angle in mind to avoid any binding of the rear spring.

 

The place where it mounts to the frame rail is flat, but the place where the spring mounts to the crossmember has bit of tilt to it. The angle is the same in the middle and where both of the u bolts go. I'm starting to wonder if if this one has just been tweaked a little bit. It's not a significant amount and can easily be welded in so that it is flat. My main reason for asking the question was because I was worried about bind. I appreciate everyone's input so far.

 

I noticed the same thing with my rear crossmember. I think it's a little tweaked from the weight of the torque tube hangin from it after I detached it from the trans.

 

Now you got me thinking. Im off out to the garage to check mine.

 

Nope they are dead flat , the top surfaces are parallel all the way across, just checked three different ones i have here. yours could be twisted from a hard life maybe.

 

^ Yes, flat. No caster.