Steering, Suspension, & Brakes

I've removed the cross member in my 79 MGB so I can notch it for a small block ford. Before I removed it I noticed the steering rack looked like it was not parallel to the cross member. But then I thought maybe my 59 year old eyes peering through blended bifocals were messing with my alcohol consumption damaged brain. But now that it's out I know for a fact it was not parallel. The passenger side rack mount extends a quarter inch farther out from the cross member than the drivers side rack mount.
There is no indication that either of the mounts was replaced. Neither is bent or damaged. The cross member is not bent or damaged. There were no shims between the rack and the mounts.

Is this difference in the rack mount dimensions common?

Steve Melfi

Common? I hope not! My '71's rack is parallel.

Steve, I think I'd find another crossmember to notch. Even if it was done at the factory to compensate for some misalignment of the crossmember in relation to the chassis (that I would check very closely) the rack would still be out of alignment with the suspension bits so bumpsteer and ackerman would probably not be optimal.

Steve,
This is a phenomena that I've noticed on my conversion over the years and I have generally dismissed it as an optical illusion. I've done some measuring in the past and I agree with you that the rack is decidedly not parallel to the crossmember (the passenger side is further forward).
Just to test my sanity, I have just come from the garage where I have assembled an undamaged RB crossmember and rack as spares, and lo and behold, they are also not parallel. To any reference point the tie rod ball location is about 1/2" further forward on the passenger side.
Can't explain what I'm seeing but Steve and I can't be both hallucinating!

Graham,
Thanks for taking the time to check yours out.
After I get the cross member notched and the front end put back together the car will be off to the frame shop for a check up. I'm not going to proceed any fruther until I know the car is straight.
I'm thinking maybe when they built these cars they may have selected on a car by car basis the size of mounts to weld on so that there would be no binding (lateral force) at the steering universal joint at the firewall.

Steve

I've always suspected that the guys in the MG factory didn't know what an assembly jig was from the multitude of Bs and Midgets with the rear axles offset. This looks like another example. Somewhere along the line something slipped and I guess a bunch of RB MGBs were built with the steering rack uneven. I guess for a street car it wouldn't make a lot of difference, the mounts are strong enough and not damaged. For a race car I'd get it right of course.

Since my first post I have wire brushed the rack mount welds and the areas near them. There is no indication that the mounts were ever removed and reattached.
I have a 64 MGB (I think that's what year it is) sitting out by the garage (put a 302 in it 20 years ago but got rid of the engine and trans several years ago). It has shims between the rack and the mounts, and the mounts have slotted holes. The stock steering shaft universal joint on it was large and located about a third of the way down from the fire wall.
On my 79 the universal joint is at the firewall. So a very slight change to the mount positions will cause a large alignment change at the universal joint. That being said, I don't know how I can get the rack parallel to the cross member without adding a second universal joint somewhere along the steering shaft.
I did a brief rack mount search fly by in the forums at the other popular MGB web site and it came back with 3 or 4 pages on the subject. When I get the time, I'll go back there and read up on the matter.
My inclination is to add another universal joint. That would ensure no lateral stress at the firewall universal joint and would get the steering shaft away from the remote oil filter adapter.

Steve

Steve, that misalignment is probably the real answer to the issue, BMC wanted to use an existing rack and the only way they could fit it in the cheapest with one joint was to offset the mounts a bit. Now that sounds like MG engineering for sure. Just like the Spridget chassis, found that the steering would fit without a u joint if the wheel was angled in relation to the driver, so all of them have the wheel not square with the dash.

I've seen this before, though it was a long time ago, and did enough checking to determine that it was indeed a factory move. My memory is so foggy on it that I can't recall any of the details of why or how it came about but I do believe that all of the late model LHD cars are the same way. Yes it is irritating to think that it was not aligned the way it should be, but as a practical matter there is no way you'll ever be able to tell the difference in driving it.

Jim

The story I've heard, and it makes sense when you stop and think about it, is that when the steering column length was increased on later cars, that the rack had to be canted to bring it back into alignment with the upper steering column. I discovered that when I wanted to install an late model steering rack, that the shaft was several inches longer. As the shaft is pointing outward as it also points up, the shaft end is further outboard from the point that would properly intersect with the upper column. MG, rather that change the angle of the pinion shaft at the rack casting, simply moved the mount locations to re-align the intersection point of the lower shaft with the upper shaft. We all know of other engineering work arounds with the rubber bumper cars (ride height!)



Edited 1 time(s). Last edit at 05/05/2009 10:24PM by 67MGBV8.

There's an article titled "The Sump of All Fears" by William M. Lane and James Jewell in the May 2004 issue about how to notch the cross member. In the photos included it looks to me like that rack isn't parallel to the cross member.
I've read up on how to align the rack column with the column attached to the steering wheel and the problems that can occur if they aren't properly aligned. I'm definitely adding another joint between the rack and the existing joint.

Typically, aligning the column is no big deal and certainly much easier than the rigamarole setup you see using detachable points to line things up. Adding an extra universal joint will add play in the steering but if that's not a concern....

Anyway all it really takes is to lift the wheels off the ground, disconnect the column, make sure everything moves freely, loosen all the attaching bolts, reattach the column, jiggle things around and begin snugging bolts down starting near the u-joint and working back from there and shimming if needed. When everything is tight it should all move as freely as it did loose. That's about as complicated as it gets.

Jim

Jim,

I might fabricate new rack mounts. The other issue I've been thinking about, is that with one rack mount surface an inch farther out from the cross member than the other mount, the angles of the tie rods relative to the rack are probably not the same. So, one front wheel is not going to have the same degree of turn as the other for a given steering wheel rotation. In other words, with the front wheels straight ahead and the steering wheel then rotated a turn to the right, the right front wheel will move say 15 degrees ( I have no idea how many degrees since my front end is in pieces right now). Then when you rotate the steering wheel left from straight ahead the left front wheel may move say 17 or 13 degrees.
I'm not sure how critical this is and if I should even be concerned.
I'll check it out after I install the cross member.

Steve

On second thought maybe the rack to tie rod angles are oposite and equal.

Something to bear in mind is that there is a great number of these cars out there with the same configuration and only in very isolated instances has anyone ever said anything about it, and then it has come from visual observation of the rack, not from driving impressions. In my opinion if it makes you that uncomfortable perhaps an early crossmember would help with that. You should be able to score one pretty easily, heck I have 3 of them stuffed under the bench. It would mean modifying the length of the pinion but any decent machine shop can do that easily.

Jim