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MG MGB Technical - Improvement of front shocks with or w/o OE springs

So I've gotten tired of the constant bouncing of the front end of my 80 LE B and have begun investigating adding a shock absorber to the setup in hopes of smoothening out the bouncing and vibration of the entire car as I hit bumpy city roads.

I see a couple kits offered by Moss for under $500 for the pair... Monroe (~$445) and KYB (~$480).

My B has 105k miles on it now and I'm fairly confident the springs are original.

Will adding the shocks resolve my bouncing/shaking front end?

I don't mind the ride height with my OE disc wheels, but I also see some front lowering springs offered ranging from $50/each @ 480# spring rate and to $68/each @550# spring rate.

So I wonder if I really need to "upgrade" my springs to not destroy the new shocks, or if they'll be fine. I also wonder if the new springs will make the shocks perform that much better.
Jeff Grant

Jeff. It sounds like your original shocks are worn and not performing properly. Their Brit name is dampeners which reflect their function which is to dampen the movement of the springs. From your description this does not seem to be happening.

Peter Caldwell, at World Wide does an excellent rebuild. I have been using his rebuilds on my GT for several years with no complaints.

But, as a first step, have you checked the fluid level in your current shocks?

Les
Les Bengtson

Les, thanks for your quick response.

I'm sorry to say, but I didn't know there were OE shocks at all! I'd taken a look at my factory service manual and did not see any listed. I just did my front brakes and just see a spring sitting there.

Any chance you have a picture of the strut so I know what I'm looking for?

This being said, obviously I have no idea of the fluid level!
Jeff Grant

It is the arms of the front lever-arm damper that support the top of the king-pin and stop the wheel from flopping over :o) Outlined in the attached.

Paul Hunt

Where and what type do you add fluid?

Do you think there's hope for it as is? I've owned the car for 11 years, sat for the last 7, and I can tell you I've never added any fluid.

What do you think about the strut conversion? I know it's not OE but try to not discourage it because of just that!
Jeff Grant

The tube shock conversions are ill designed and unecessary.

Just remove the plug in the top of the Armstrong shock and top up with fluid you can buy from any motorcycle shop.

If that doesn't cure your case of the wobblies, you will need new or rebuilt shocks.

I guess the front end would look strange to someone not used to anything but tube shocks!
Bill Spohn

Jeff. If you remove the front wheel, after installing jack stands under the spring pans or frame, you will see the two arms of the dampener which attach to the upper trunion of the king pin. They attach to outside of the dampener which is bolted to the cross member by four bolts. As you face the dampener, looking through the wheel well, you will see a bolt near the top of the dampener where the body is in a cylindrical shape. Remove that bolt to check for shock oil.

To top up the shock, remove the bolt and squirt oil into the shock until it is at the bottom of the threads. Allow any excess to drain out (paper towels should be at hand when doing this to mop up any excess) and reinstall the bolt.

I use the Moss, et al, supplied Armstrong oil, but others have used motor cycle fork oil. Instead of using the factory bottle, with its small flip up filler, I purchased a trigger type oil can, labeled it "Shock Oil" and find it much easier to use when topping up the dampeners.

If, after filling the dampeners, there is still a problem, or if you can see the oil leaking out the sides after a drive, the dampeners need to be replaced.

As to the desirability of replacing the factory style of dampener with a tube type shock, everyone has their own opinions. I will note that Motor Head, who sells parts and service and has their own "Bad Parts" page where they list parts which they have found to be of low quality, list the tube shock conversion on that page. I have given the link on the MGB General BBS under the "Moss Parts" thread and you can go there if you desire.

World Wide Auto Parts has been recommended here for the quality of their rebuilds of the original style dampeners. The few remaining professional MG mechanics I know all use their products. I am using them on one of my cars, the one which gets used most often and, as necessary, will replace the ones on my other cars with World Wide rebuilds. Peter Caldwell, who owns World Wide Auto Parts of Madison, Wisconsin will, from time to time, post here. But, he never mentions that he is in the business of selling high quality rebuilds, and other parts, so let me do it for him.

Les
Les Bengtson

Jeff-
Unlike more modern designs, the MGB does not make use of inexpensive disposable tubular shock absorbers in order to damp the movement of the suspension. Instead, the suspension is damped by Armstrong lever arm dampers. Unless the car is routinely operated on very bad roads, the Armstrong lever arm dampers are quite adequate for their purpose and need not be replaced. Most owners who make the conversion to tubular dampers usually convert back to the original system. Of course, adjustable tubular dampers would have a potential advantage for racing on a racetrack, as their sealed pressurized nitrogen atmosphere would offer reduced foaming. Should you decide that an increase in their damping effect is desirable, this can be accomplished by simply replacing their valve units with heavy duty ones which have had their rates uprated by 25%, as the factory race team did. These are available from Victoria British Ltd. at http://www.victoriabritish.com . If your present front lever arm dampers are worn out, uprated units are available from Brit Tek (Part # GSA367UR). However, excellent rebuilt units are available from World Wide Auto Parts of Madison. They have a website at www.nosimport.com/shoxcatalog.htm .

What fails in a lever arm damper? Almost all of the (non-traumatic) failures result from lack of oil in the shock. The manuals always recommend checking and topping-up your dampers every 3000 miles or so. The shaft that protrudes from the body of the shock is rotating in the body without a bearing. To ensure sufficient lubrication there is often a channel or groove in the shaft bore. At the outside there is a rubber packing retained by a thin metal washer. A packing needs some lubrication to work at all and the weeping of oil acts as a deterrent to dirt getting in. Dirt getting in will score the shaft at the seal area hastening the demise of the packing and wearing the bearing surface in the body.

World Wide rebuilds are the best available. They machine the body and install Delrin nylon bearings. Their competitors use bronze. Bronze requires oil, but Delrin does not. World Wide then installs a radial double lip oil seal with a dust excluder. Their competitors use some variety of plain rubber washer retained by steel washers against the lever arm. World Wide installs a 3 micron finish stainless steel sleeve on the shafts in order to repair the grooves and pitting usually present on the shaft. These sleeves are of their own design and guarantee a surface finish and concentricity required for the best performance from the oil seals. Apparently, their competitors either grind or sand, when necessary, the shaft to smooth it. World Wide uses all-new, fine threaded hardware. Their competitors units do not appear to. World Wide uses an anti seize compound on those fasteners that the installer may need to loosen for installation. They clean the units using a media tumbler, glass bead blasting, and tumble again, then ultrasonics. World Wide finishs by painting with two coats of primer, followed by two coats gloss black high-heat enamel.


To refill your dampers (if they haven't worn out from years of neglect), on the front look atop the suspension on the top of the front crossmember and you will see a part where the upper arms of the suspension attach. This is the lever arm damper. Because the internal parts of the damper dislike grit, clean around the large filler plug on the top of the damper, and then remove it. Pour in the damper fluid and then replace the nut. Bounce each side of the front end of the car to help get rid of any air pockets inside the damper, and then remove the filler plug and top up the damper with some more fluid. One of the most common causes of problems with lever arm dampers is overfilling them. The top dome on the units used on the MGB is present in order to act as an expansion chamber. If the damper is overfilled, i.e., all the way to the top, then no space will remain for expansion when the hydraulic fluid gets hot. This will result in excessive pressure and cause leakage. Be aware that petroleum-based hydraulic fluids are not compatible with the natural rubber seals. Armstrong still makes its specially formulated hydraulic fluid available. It can be obtained through Brit Tek at http://www.brittek.com/ . The factory manual stated that, if necessary, 20W mineral oil could be substituted during warm weather. However, not all mineral oils are the same. During WWII the Germans made a lot of advances in this area, so mineral oils are much more common in Europe than on our side of the pond. Mineral oil with an anti-foaming agent was (and may still be) used in the power steering system of Audis. I suspect that the factory intended for mineral oil with an anti-foaming agent to be what they suggested, and just presumed that the customer would be knowledgeable enough to use the right stuff in a pinch (b-i-g presumption!) To fill the dampers for the rear suspension, find the linkage rod that connects the leaf spring to the damper. Atop the body of the damper is a filler plug. clean around it, then remove it and follow the same refilling procedure as used for the front dampers.

Note that Armstrong conveniently stamped their part number on every damper (except for the Spridget front units that were cast). All front dampers are the same Part Number (8177/1), even though there was a change in the very earliest models. On all rear dampers, the number is stamped on the underside of one of the mounting ears. MGB rear dampers will have 8178LH or 8178RH, or 12012 (LH) or 12075 (RH). According to Armstrong’s 1978 USA catalog, Part # 8178 fit all MGB Roadsters and GT 4 cylinder models through 1974. The 1973 and 1974 BGT V8 models used Part # 10801. All models 1975 through 5/1976 used Part # 12012. Afterwards, all models from 6/1976 to end used Part # 12075. While there appears to be no difference in the 8178, 12012, and 12075, if matching, check that the numbers are the same just to play it safe.
Steve S.

Steve, Les, and Bill, thank you all for your very informative posts. I was impressed that they didn't seem overly biased toward the "go OE or go home" mentality I've encountered in the past. :)

I think I will try to top off the fluid in my existing front parts first. The rear is quite stiff when I push down on a rear fender so I'm not going to check into that just yet.

The only part I want to confirm is the filling of the fluid...

Les said "squirt oil into the shock until it is at the bottom of the threads". I assume that's bottom of the plug bolt's thread, correct?

Steve said "One of the most common causes of problems with lever arm dampers is overfilling them"... this seems to contradict what Les is saying.

Keep in mind that I haven't seen what we're talking about yet, so maybe I'm mis-visuallizing what a bolt in a hole's going to look like once removed. Please clarify things a little for me.

Since it's July 4th, I can't get any shock fluid just yet, but I'll try to soon. The prices for rebuilt units at WWAP amaze me! I was expecting them to be much more. This being said, I can't see not going with fixing my OE setup as a "first try" to make my suspension less bouncy. Thanks so much everyone.
Jeff Grant

Jeff-
When faced with contradictory instructions, go with the ones that seem to make the most sense.
Steve S.

Considering I don't know what I'll be looking at, I can't say which makes the most sense. But since you're not directly defending your own statement, I'm guessing you're pretty confident that you're the one who's right. ;)

Anyway, I was at a car show today (Summer Nationals in Massachusetts) and saw a '78 MGB. I talked to the owner for a while and got a chance to bounce the front of his car. It bounced some, but surely much less than mine. He said he filled it just a few days ago with some other maintenance he was doing. I don't know how old his dampeners are though or what shape they're in, so I can't say how it would compare to freshly rebuilt ones.

Can someone say how much fluid they take? I don't know what size containers I can get fork fluid in. Will a quart be enough to fill both if my dampeners are completely try?
Jeff Grant

Jeff. In answer to your questions:

Yes, you fill the horizontal hole to the bottom of the threads and let any excess drain out before reinstalling the bolt. This is true for both front and rear dampeners when they are installed on the car and the car is relatively horizontal.

It is possible to overfill the dampeners when they are filled off the car, especially if the hole is placed upwards to make filling them easier.

The Armstrong fluid comes in a one pint (16 fluid oz.) container. A single container is adequate unless all of the dampeners are completely dry. Can't say how much would be needed if they are completely dry because I have never started from four completely dry dampeners.

Again, a trigger type oil can, with a long, flexible spout, makes it quite easy to get the spout end into the hole and fill the dampener with oil.

Les
Les Bengtson

Thanks Les for your quality response again.

Do you, or anyone, have a picture of the fill plug?.. or will it be obvious once I get in there to look at it.
Jeff Grant

Jeff. I do not think you could miss it. Take a look and, if you do, I have a pair of dampeners that are spares and I will take a photo of them for you.

Les
Les Bengtson

Sounds like a plan then Les. I need to pick up some fluid first, so don't be surprised if I don't respond until monday or tuesday on progress.
Jeff Grant

They *can* be overfilled, but not like most people think. The rear dampers have the filler hole on top which is accessed via a plastic plug on the outer sides of the rear shelf that contains the battery lid. They should be filled to the *bottom of the threads* as per the Workshop Manual. There is an air-space inside which absorbs pressure changes in use. However if you fill to the *top* of the threads then screwing down the bolt will pre-pressurise it, which is not ideal. Front dampers can have it either on top or the side/front it seems, and it is impossible to overfill the side/front fill as you will only get fluid in as far as the bottom of the hole unless you try *really* hard. Image of top fill front and rear types attached, the filler plug on front/side fill types is equally as obvious.

Paul Hunt

Thanks Paul for the picture! Now I just need to get some fork fluid when the local bike shop is open!
Jeff Grant

This thread was discussed between 04/07/2008 and 05/07/2008

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