|The MGA With An Attitude
STEERING COLUMN BUSHINGS Revisited - SR-102A
At 05:29 PM 6/10/04 -0700, Grant, Michael wrote:
>" We are going to need some assistance developing standards for these bushings.
"260-160, 260-170, 260-190, Bush, felt_steering_MGA_too thick"
[Large part of response clipped, but pertinent info follows.]
I have in hand one of each 260-160 and 260-170. I do not have 160-190 (non-adjustable column top bushing). Measurement gives this:
260-160 --- 1-5/16" x 3-3/16" x 0.156" thick - Lower
260-170 --- 1-13/16" x 3-3/4" x 0.170" thick - Upper - [This one is too thick]
It has been nearly a year since I wrote about this issue on my web site, and mentioned that I need to install these parts. I suppose 17-1/2 years and 189,000 miles is enough for one set of felt bushings, as they are not too difficukt to replace. With this little reminder, maybe today would be a good time to do it. If I manage to dress the felt parts to suitable thickness to make a snug fitting assembly (that works), then I might disassemble it and "try" to measure the finished thickness of the parts.
At 05:02 AM 6/12/04 -0700, Barney Gaylord continues:
I just R&R'd the adjustable steering column on my MGA to install the felt bushings. Only 3 bolts, and easy to handle on the bench. If I had known in advance that the bottom bushing was a good fit without any tinkering, I might have been tempted to do it without removing the tube. In fact it should be easy enough to do in situ, but may need to remove the steering wheel to clear the seat back when pulling the shaft.
I bought 260-160 and 260-170 directly from Moss Motors in early July 2003. See prior memo for the measured dimensions of the bushings. Measuring the tube and shaft I get these numbers:
Tube bottom end ID = 1.156" and has the end curled inward slightly to prevent the bushing from falling out. Shaft bottom end OD = 0.810". That makes the radial space 0.173". That bushing is only 0.156" thick, so it leaves about 1/32" diametrical clearance. The shaft can and does wobble around that much at the bottom end, but likely no one should care, as you would never notice that small lateral motion at the steering wheel. The 260-160 bushing is otherwise a perfect fit for width and length, so all is well as is. That's a nice improvement over the too-thick part I had to deal with 18 years ago. If you had a chance to specify a slightly thicker (maybe a non-standard material thickness) felt part, I would think that 11/64" (0.172") would be a better fit.
Tube top end ID = 1.316" (maybe 1.312" the short way if it's not perfectly round). Shaft top end OD = 1.090". That makes the radial space 0.111" to .0113". My 260-170 bushing was too thick at 0.170" thick, and no way to assemble it even with great force on the shaft. It might be good at about 0.120" thickness, assuming we like a slight interference fit for snug operation at initial assembly. I will guess that 0.125" thick might allow it to be assembled but would likely leave it too tight for acceptable ease of turning with fingers on the steering wheel. But it wouldn't hurt to try 1/8" thick material if it's a standard thickness of felt stock. Maybe that was the factory's original intention.
So I pulled the same fix I used 18 years ago. I stapled the felt piece down on the workbench and touched off the thickness very gently with a wire wheel in electric drill. It only took a few minutes and one interim stop for a thickness measurement. I think I ended up with one edge a little thin at about 0.110", but at least half of the part was closer to 0.125" thick (or maybe not quite 0.125").
In assembly the shaft went in with a moderate push and some wrist action on the steering wheel hub. The wheel turns easily with one finger on the spoke near the rim, and there is no detectable radial clearance (like a nice small preload). The 260-170 bushing is otherwise a perfect fit for width and length. If you have a chance to specify a thickness tolerance, 0.125"/0.115" should be appropriate. As tradition stands this day and age, material thicknesses are often on the small side of tolerance to reduce cost at the mill, so you might expect nominal 1/8" felt material to actually be 0.120" +/- a bit anyway.
I know Rick deOlazarra mentioned in a prior memo that his 260-170 part seemed to fit okay (except for a smidge on the length). Perhaps the thickness has been changed (corrected) from 0.170 to 0.120 sometime in the past year since I bought my parts. If so, that part may also be okay as is.
For the non-adjustable shaft, I will "guess" that the shaft will be smaller diameter at the top end and the 260-190 bushing will be thicker, but I don't have a clue on the actual shaft diameter. I would be interested if anyone has a report on that part.
Addendum, April 25, 2013:
Just a quick note. Nine years and 60,000 miles down, and the felt bushings with graphite oil are doing just fine, still generally snug, no reason to tamper with them yet.