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MG MGA - MG v-8 bushings - too tight!

Good Saturday morning all:
I found lots of threads on this general topic, but my specific question is: the new bushings will no go onto the pivot shaft. It isn't a matter of needing lubrication, they are too small. My car is an early one but I understand that these bushings are supposed to fit TDs and TFs. Anybody else had this problem? Maybe I should just return them and get one of the other bushing types? I don't think modifying the shaft is the answer.

Thanks again,
Jack Bissett, Lexington, VA
John Bissett

Jack I had the same problem with the one side of my 1600 A Coupe. The one side slid on easily and the other side was very tight on the pivot. I expect that it might have been replaced in the past; although they should all be the same size. It could have also been my fault when I instaleld the V8 bushing I might have burred the ends on the bushings a little. Either way, I used a hone to enlarge the size of the V8 bushing to fit over the pivot. It took a long time but eventually it slipped on and 5,000 miles later is still working fine. The origial bushing especially the ones from a common retailer don't last anytime at all. I fitted them on my 67 B and after 2000 miles they were worn out. I replaced them with V8 bushing and no problems. I now have V8 bushings on all my cars.

Andy
55 TF
60 A Coupe
67 74 B GT
Andrew Preston

I've noticed that recent bushes appear to be made from bar stock, with the hole drilled, rather than pre made steel tubes you would expect and as they used to be. Third world holes have wild variations, likely because they are made with surplus drill bits c WWI, or drill bits hand hammered by blind men. When I've encountered this I've just drilled the holes out, but it isn't easy unless you have a lathe. I also radius/chamfer the back end of the hole, since it runs into the rather large radius at the pivot pin shoulder.

FRM
FR Millmore

Thanks Guys. I just re-read Barney Gaylord's notes on the front suspension and he clearly suggests that the bushings need to be pressed onto the shaft. As I remember, they are supposed to be tight on the shaft and flex in the rubber, not twist metal on metal. So I will remove the pivot shaft from the chassis and try pressing the bushings onto it. One more step before i can put all this back together!

Thanks, happy Spring to all,
Jack
John Bissett

I can't believe that Barney says that, since it is not true.
from: http://www.mgaguru.com/mgtech/suspensn/fs202.htm
There is a link there that doesn't work, and I can't find any such statement. This is the only reference I found:
"A possible alternative to replacing a pitted Pivot could be to install MGB GT V8 type A-arm bushings. These bushings have a steel tube inner liner similar to silentblok bushings in a leaf spring. When installed the steel tube is pinched at the ends and does not rotate on the shaft."


The V8 bush slides on the shaft, and is clamped longitudinally by the nut and washer against the shaft flange. As such, the length of the bush and correct assembly is critical. They are commonly not assembled correctly, a result of incorrect washers frequently supplied today. You will note that the shaft has a small step at the end, and the OE washers fit ON that step. Today's washers are too small ID and will not fit there, so the bush (v8 or OE type) is not clamped correctly, resulting in rapid wear or failure. I either use the OE washers or machine the ID of the new washers to fit on that step, as designed. If the washers are right, and are located correctly on assembly, then either OE type or v8 bushes are finally tightened with full weight on the suspension, as both types use the rubber in torsion - neither has motion of bush on the shaft. Barney leaves some ambiguity or error there. The truth if the matter is that it is difficult to do correctly with the OE bushes, so when we could still get them in a useable state, I would assemble the arms in the normal running position without the spring, fully tighten, and then fit the spring. But, it has been about twenty years since I fitted anything but v8 bushes, since the OE type you get today are rubbish.

FRM
FR Millmore

FRM, -- Sorry about the broken link (missing picture). Thanks for the comment. I uploaded the missing picture, even found a few more to go with it.

You're right, I didn't say the steel sleeve was press fit, only that the rubber bushing is press fit in the a-arm, and the steel sleeve is "pinched on the ends" so it does not rotate. The steel sleeve is supposed to be slip fit on the pivot shaft, then captured against the ends to prevent rotation.

I have added a few more lines to clarify the fit and assembly, and some of the problems that may occur with the sleeved bushings. They are not perfect, but are absolutely wonderful when properly installed. See here:
http://mgaguru.com/mgtech/suspensn/fs202.htm
Barney Gaylord

Barney
Your site says the following:"Rubber bushings for A-arm inner Pivot ride and rotate on the Pivot shaft with suspension motion."
I always thought that the idea of tightening the original rubber bushings with load on them was so that the compression from tightening them would press the bushing against the shaft, fixing it in place, and only allow suspension movement by distortion of the rubber, half way in each direction. What you say may often be true in practice, but I don't think it was intended that way.
John DeWolf

The original rubber bushings push on with your finger tips. The rubber is soft enough that compression effect from the end washers is essentially nil. Tight or not tight, the rubber parts will find their own position when set down on the suspension, and they will rotate some on the pivot in use. If the pivot shaft is rusty and pitted it will chew up the rubber bushings in short order.

Polyurethane bushings are entirely different. That material is essentially solid and will definitely rotate on the shaft with almost no flexing. I had them in my car for three years and 34,000 miles in the early 90's, and they came out looking exactly as new, no discernible wear. They are much stiffer than original rubber bushings, and probably stiffer than the GT type bushings. Since I installed a good front sway bar with polyurethane mounts, I don't think I can tell any difference in ride quality regardless of what bushings are in the A-arms.

The GT bushings should have the inner slip fit steel sleeve captured on the shaft so the rubber will flex during motion resulting in zero wear. For these it is very important to have weight of the car on the suspension for final tightening of the nuts and capture washers, so the flexing motion will be half in each direction up and down from center. If they are tightened with full suspension drop, then total suspension travel will flex the rubber too far in one direction likely resulting in early failure of the structural rubber.

I may have posted incorrect information in a prior post. I just checked my maintenance records, and the GT-type bushings have been in my car for over 15 years and 175,000 miles, still in good serviceable condition.
Barney Gaylord

OK, listen up! I said this before, but here are the quotes from the MGA WSM:

" Fit new rubber bushes into the levers. These will be found to be quite a loose fit in the lever, but when clamped up by the nut and washer will expand into their housing. These bushes do not rotate on their surfaces, the angular movement being taken by the rubber deflecting torsionally in itself. Special care should be taken when assembling these bushes to maintain a central location, so that the expansion of each half of the bush is equal."

AND:
"It is essential to clamp up the bushes when the suspension levers are set parallel to the ground to ensure even stresses on the bushes."

AND for the back:
"Before tightening the spring bolts it is absolutely essential that the normal working load be applied to the spring so that the flexing rubber bushes are deflected to an equal extent in both directions during service. Failure to take this precaution will inevitably lead to early deterioration of the bushes."

I will note that there is a very nice cross sectional drawing of the assembly before clamping in the WSM. It clearly shows the little shoulder that the washer is meant to fit on at final position. It can be tricky to locate the washer so that it goes onto the shoulder when tightened; a certain amount of fiddling is required, and it helps to assemble the nut and washer without bushes and take note of the nut final position with respect to the split pin hole and end of shaft.

Also, there is a dimensioned drawing of the bush, with tolerances of +/- .002. These are precision parts and must be fit as such. All such rubber bush designs have precise locating shoulders or distance tubes, in order to give correct compression of the bush. When correctly installed, there is NEVER rotational movement of the bush on either shaft or housing. I have dismantled cars that had been correctly assembled except for lever position, and after several years operation the levers were still strongly spring (rubber bush) loaded to the incorrect assembly position. If there is such movement, it will wear very quickly and the parts will be worn and polished. Movement results from wrong assembly or wrong parts. Reality is that even quite badly pitted shafts will NOT eat bushes that fit correctly and are assembled correctly, so long as there has not been massive loss of metal giving a truly loose fit.

FYI, the OE bushes routinely lasted in excess of 10 years/100,000mi daily service on the very rough Pittsburgh streets where I used to be, so long as engine oil had not soaked them. We essentially never had to replace bushes other than as part of a general front end rebuild, usually due to lower links not being lubed properly.

FRM
FR Millmore

Sorry if I misunderstood or misquoted you Barney; the line about pressing them into place with the bench vise, I took to mean onto the shaft.
As it turns out, i cleaned up the shaft ends with a file and one of the bushes went on with no trouble. The other one, I should have dressed further, as it took a hydraulic press to install it on the shaft. Now, am I going to be able to get the arms onto the bushes?, as they are now on the shaft. Am I shafted? Tune in tomorrow, as I intended to install the arms and the shaft then. We'll see! The original bushings are so much less trouble!
Jack
John Bissett

I bought a set of each of the three styles of bushes; original, MGB V-8 and polyurethene. I have
MGA wire wheel disc hubs on the front of my TD. From reading the comments in this thread, it looks like I might be better off (in terms of ease-of-installation and durability) if I use the polyurethene bushes. Any additional comments on the matter would be appreciated.

Regards,

Bobby Loughridge
B. F. Loughridge

Bump for TD guys who have the same questions.
John - Curious as to how you did, certainly not correct. IF the bush is pressed on to where it is supposed to be, the inner end of the rubber would be expanded such that you can't get the arm on in the right position. Read Barney again - the bush gets pressed into the arm and centralised. There is rubber protruding on both sides which gets compressed when the complete assembly is properly located and clamped on the pivot; that compression is what makes it all work.

FRM
FR Millmore

True that the MGB GT V8 type bushings must be pressed in to a centralized position in the arms. Either one out of place in either direction would interfere with full assembly of the side arms onto the spring pan. In that case the rubber would be longitudinally deformed and stressed when the big retaining nuts are tightened, and it may result in fore/aft misalignment of the lower control arm.

I'm sure that the rubber exposed at the ends of the bushing is NOT compressed and does not expand when the nuts are tightened, as the center metal tube is as long as the rubber part. The rubber fits quite tight in the arm and is compressed radially in that area, resulting in a slight bulging appearance at the ends. I have never known them to slip notably out of position. Mine have been in service a long time with lots of harsh driving with no problem.
Barney Gaylord

"I'm sure that the rubber exposed at the ends of the bushing is NOT compressed and does not expand when the nuts are tightened, as the center metal tube is as long as the rubber part. The rubber fits quite tight in the arm and is compressed radially in that area, resulting in a slight bulging appearance at the ends. I have never known them to slip notably out of position. "

True that the initial condition is that the rubber is the same length as the steel, but when it is compressed radially by installation, it bulges out the ends. This bulge is then compressed by the nut/washer (shoulder), and that compression locks everything on place. If you measure the OD of the exposed rubber after everything is tight, you will find that it is significantly larger than either the hole or the starting bush OD. I am going from real OEM data, and poorly made bushes might differ. And I agree, they never move after correct installation, but they will if the bushes are not central and the clamping is not correct as I described way back there.

FRM
FR Millmore

Need to bump this up again so the TD guys can find it.

FRM
FR Millmore

Sorry....just saving this thread from the archives and back to the top for a friend


Prop
Prop


this was a great thread thanks.
Rebecca from the midget forum
PS: I will be back here in a year with MGA questions as I will be hopefully starting a new project.
R Harvey

I should have followed up. Back in early April, I misunderstood, and struggled to get the first bushing pressed onto the shaft. The second one went on fine by hand, after cleaning up the shaft. I was then able to get the bushings into the a-arms with a little careful work using my hands and a bench vice. Didn't take long. When I get to the other side of the car, I'll remember how I should have done it, and have less trouble.
Thanks for all the info and suggestions.
jack
John Bissett

This thread was discussed between 19/03/2011 and 02/05/2011

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