Technical 1929 ford roadster spring behind?

Hello , I'm building a fenderless model A roadster and was wondering if the ride quality would be worth changing the rear spring to leaf behind compared to leaf over. Im using a reverse eye main leaf with the original A pack with it, I have the spring behind bracket that Millworks Hot Rods sells, I've heard a few people say the roadster being light would ride better with the leaf moved behind the rear, are there any other concerns or advantages/disadvantages to doing this? It will be a high boy but frame stepped to get the tire (7.50-16) to be eye level with the radius of the tire wheel well. Thats the goal anyway. thanks for your help.

 

You probably won’t notice any ride characteristics changing but spring behind will require a lot less frame step to get the car that low. Really you could probably get it there with out any step if you just stretched the frame long enough to use the stock cross member with spring behind

 

The best way to improve ride quality is to lengthen the wheel base. Does the set up you plan do that?

 

It could , I’m starting from scratch so anything is possible I guess. Just want to think it all out before beginning.

 

All a spring behind does is lower the rear crossmember. In order to run a spring behind you will have to lengthen the frame
I just did it on a T frame.

 

thanks guys

 

If your car has an original roadster spring (7 leaf) it’ll ride just fine spring over.

 

Yes I have the original, thanks for the response.

 

You're limited with how low you can get the rear with the spring over the axle no matter what you do to the frame/rear crossmember due to the proximity of the axle and framerails. This is assuming we're talking about a traditional Model A rear spring. Since you mentioned starting from scratch, I would set it up to mount the spring behind the axle. This will allow you to get the car lower without a huge kickup and provide more freedom with final ride height in case you decide to add/remove leaves, use standard eye main leaf, etc. Moving the spring behind the axle also solves the issue that can arise with wheel cylinder and brake line clearance when using juice brakes.

As far as ride quality goes, they're both going to ride like an early Ford with buggy springs.

 

last century i ran a flatty powered '30 coupe with 5 rear springs, worked great...

 

I'm in the same boat as Dirtbag54 - just picked up a 28/29 RPU and trying to decide the chassis design. Was suggested to use a 40 front spring behind the rear and stretch the wheelbase to 108". It will be fenderless. Noticed the brackets they use offset the rear about 6 1/2". Considering 2 x 3 x 3/16 rails @ 26" front 36" rear with a 3" kick up in back. Probably gain the wheelbase with a spring over dropped axle up front ahead of the cross member.

 

Find a set of 35/6 rear bones and you will have the brackets built in, then make a bracket for the rear end.

 

looks like a perfect solution, probably set up for 2 or 2 1/4 spring - thanks...

 

Use a 40 rear flip the bells and shorten the frame and put the spring in front. This way you could really get it low without interference with the axle and frame. If you're using the model a frame it's a lot easier to shorten it then try to lengthen.

 

I’m curious how much horsepower the 35/6 rear bones could handle?

 

A guy will have to run a torque arm with any ford bones. I broke one of my 40 arms on my T modified years ago. When I built my single seater I built a top arm that keeps the rear end from rotating, it’s worked good so far.

 

I built the rear section and tacked it on to check the length. It will be trimmed and capped.

 

Good idea Rusty !

 

A spring behind done to improve things, generally will best be achieved with a rear chassis kickup to a minimum of the rail height.
That way you get lower stance and your axle tubes hopefully will not hit the underside of your frame on rough roads or bad undulations...
It is somewhat of an under valued method IMHO of lowering the rearend.

 

Does anyone know offhand how many inches that the crossmember has to be moved back to do the spring behind? I did the basic Tardel step on my frame but I always wished that the rear of the car sat just a little lower. I could have done a taller step but I didn't want to lose the trunk space. Might have to think about doing this as I have a 40 rear-end in my spare parts shed.

 

Here's a frame by Al Simon that's served me well for 30 years . . .

 

I looked at doing it on a future project and figured it would be around 7" as a rough guide comes to mind...

 

Blowed out T spring under mine. Rides great! T spring is flatter and a bit narrower. If you use the old spring original seat that will help a bunch.