Minimum clearances.

I am building a '26 Ford Roadster and I am just wondering what minimum clearances are best to have. It will have a flathead up front with C4 automatic. I figure about 2000lbs total, 1200 front, 800 rear. Transverse leafs front and rear. Suicide front with rear mounted spring. The clearances I am thinking about are:
-Tie rod to the frame (the frame is directly over the tie rod).
-Tie rod to 4 bar linkage
-Oil Pan clearance to the ground
-Drag link to the tire.
Also, is it ever acceptable to bend the drag link to acheive sharper steering
Any help here would be appreciated. Thanks

-Dave Robinson

 

Most of this is tied to your front suspension travel. Typical minimum travel would be about 5-7 inches, so figure 3 or 4 for compression, or how far down you go before something bottoms out. With that in mind, go with about 5 inches to the oil pan. The tie rods can be dropped to provide about half an inch when fully bottomed. Same for the 4 bar clearance to the steering links. If necessary, a quarter inch will do.
You can shape the drag link for clearance to allow greater steering articulation, but too much will result in a bar that flops around on the rod ends and wears quickly.
This is what we build street cars at. Race cars that never see speed bumps and pot holes can get by with less, but require care when driven on the street.

Hope that helps. Scotty

 

Yes it will depend on suspension travel. You don't want your tie rod to be the first thing to hit something...that should be your axle. As for minimum suspension travel (compression from ride height) I'd say 2" is fine for a hot rod...its no luxury cruiser. My model a has less than 2" front and rear travel, it's not the greatest riding car but I've put well over 100,000 miles on it that way. And ground clearance depends on how much you mind s****ing...I'd say a 3" minimum, and I wouldn't have the oil pan be the low point.
And weight bias front to rear on most early Ford hot rods ends up being much closer to 50/50 than your estimate. My A roadster with a 460 Ford motor is almost exactly 50/50.
-Jeff

 

Most lowered cars, hot rods included, end up with two inches or less of suspension travel.

I'd shoot for at least three inches on the oil pan clearance, mine came out being two and a half, but it hasn't hit anything yet, so I guess it's OK

Rich