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MG MGB Technical - Lever arm shock uprating.

I've just spent the last half hour reading the archives about uprating shocks by adding shims and tightening the screw on the valve. I've spare sets of front & rear shocks that I want to play with, but I'd like some help from those that have actually done this before.

Here are the questions. Roughly what thickness of shims did you add? 0.010"? 0.050"? 0.100"? And how much did you turn the screw? 1 flat? 1 turn? 10 turns? I'd like to minimize the number of times I take the valve out to make adjustments, so I'm hoping someone can remember what they did, at least as a starting point. Other useful information would be the type of oil used to refill. Hydraulic jack oil, 20w of 40w motorcycle shock oil? I'd like to get something near the 30% upgrade offered by the overpriced valves sold by Moss, et al. The car is used for "spirited" driving on public roads.

Thanks in advance.

TTFN
Derek Nicholson

Steve S from Virgina has some information on shock valve uprating, it's in the archives, I don't remember the specifics. Wide World Auto Parts of Madison uses 20 weight hydraulic oil in their shocks. They do not recommend using a heavier fluid because it may damage internal parts. FWIW, Clifton
Clifton Gordon

Hi, I just found this site a couple of days ago and am glad I did. I like the archives too.

I've just started driving my MGB and one of the things I did was replace the shock oil with 40wt motorcycle fork oil in hopes of getting stiffer shocks for little expense. I've seen that recommended on the www several times, but I have no idea if the thicker oil will damage the shock after a while.

I read somewhere in the archives here that it does something to the pistons. I don't know.

Someone says he uses 50wt as standard procedure.

I don't know what screw you're talking about. I didn't do any more than remove the fill plug and valve. I just flushed/bled the rear shocks and noticed one washer (shim?) between the spring and valve on one, and two washers on the other. I put them back like they were.

I'll look for Steve's thread on shocks too. I've never even seen an exploded view of one.
GK Kendall

I've already searched the archive for "shock valve shim", "shock valve shims" and "shock valve shimming" in the MGB General and MGB Tecnical sections. There were quite a few threads in the Technical section, I read them all but no-one gives any indication of how much/many shims need to be added or how much to turn the screw. The most anyone seems to say is to note the original settings so that you can go back to the original setup if needed.
Derek Nicholson

I have taken a couple of front shocks apart and have some photos in my Yahoo photos. I sawed the cylinder of one in half to photograph the wear in the cylinder caused by the piston pin. World Wide Auto Parts can bore and sleeve the cylinders so you get a like new or better shock from them and a very reasonable price. You may need to sign up with Yahoo [no charge] to view my photos. My photos are open to the public.
http://f1.pg.photos.yahoo.com/ph/flash1929/lst?&.dir=/MGB+Shock+Absorber&.src=ph&.view=t

I have a copy of Steeve's post and as you say he doesn't give specific shim sizes. The rebound can be adjusted with the nut, I don't know how you could determine how much additional damping you have without using a shock dyno. Since most shock dynos are set up to check tube shocks I'm not sure if there are any capable of measuring the damping rate of lever shocks.

If I wanted valves for increased damping I would call Peter Caldwell [hope I have the selling right] at Wide World Auto Parts of Madison and tell him what I wanted.
That would be a much easier solution to your problem. You may need to send him your valves. You may also want to ask him about using heavier oil, as I recall he told me it can destroy the internal parts of the shock. Not because of compatibility problems but because it's too thick.

Clifton

Clifton Gordon

Contact Peter Caldwell at World Wide Auto in Madison WI. He rebuilds them for moss etc. He'll give you the time and really knows his stuff. He's also got some sehr interesting information re: uprated valves.

World Wide Auto Parts of Madison, Inc.
2517 Seiferth Rd. ­ Madison, WI 53716
Local (608) 223-9400 ­ Fax (608) 223-9403 ­ WATS (800) 362-1025


office@nosimport.com
Fred H

Glenn, welcome to the board.

Clifton, thanks for the photos on Yahoo. Nice to see what's in there before getting the tools out.

Clifton and Glenn. Yes, I've read good things about Worldwide. When it comes time to buy new shock, I'll probably use them. But for now, I'd just like to try it myself. There must be someone out there who has actually made these mods themselves. Or is it all just rumours?
Derek Nicholson

I meant call him. He'll give you advise on the viability of the procedure.
Fred H

Derek,
I dug into my lever shocks because their resistances seemed different when running them thru by hand. I talked to Peter regarding the procedure, and he stated that you can't get a good 'feel' for the shocks by checking by hand; you need what Clifton said, a special machine. Only one valve had a shim. I swapped shims and played with screw settings until I was sick of it, and saw no real change that I could measure by hand. A person has a limit on taking these things apart and, especially, taking them on and off the car. I figure if the handling seems off, or something isn't satisfactory, I'll get new rebuilds from Worldwide. In any case, call Peter and talk to him. Best, Joe
Joe Ullman

Henri Van Groningen sent me a set of seals for the shock arms. I had mine rebuilt at wwa so I offered to send them back to Henri. He told me to pass them on instead of returning them. Rather sporting I'd say. Anyone NEEDS them, let me know.
Fred H

Derek, thanks for the welcome.

Clifton, those pictures are great. I had no idea what was inside, and, with replacement costs, was too scared to look.

About this little adjustment nut...is it on part of the valve which has the little spring which the larger spring slides over? If it is, I didn't notice it because I didn't have my glasses on. Going by Clifton's picture of the damper valve, I'd guess it's under the left side of the top shim washer.

I didn't remove the covers because of no replacement gaskets being available. Were your gaskets reusable? I was afraid of ruining the gaskets and then having gasket-in-a-tube find its way into the wrong place.

GK Kendall

Years ago, on a '64, we put in a heavier oil to increase the dampening of the shocks. Bad decision, within three months, the front left shock had stripped out the splines on the lever. Lots of dips and such on city streets, combined with some less than optimal rural roads plus 50 wt oil did them in.
R. L Carleen

GK, The nut is covered by one of the damper shims. I did not try to reassemble the parts, in fact I sawed one body in half. You should be able to reuse the cover gasket if you are careful. Now that I know WAP of Madison can bore and sleeve cylinders I'll not disassemble any more shocks. FWIW, Clifton
Clifton Gordon

RL, not only that but Peter of wwa showed me a shock that had too heavy an oil in it. The piston clip comes off and hammers the cylinder. Looked like someone hammered a bb into it.
Fred H

Fred H: Yet these proposals keep popping up on these boards regularly...heavier oil = better damping. Sometimes an expensive lesson is the best learned. That's why "seat of your pants' mechanicking is sometimes the opposite of good headwork. Just changing out the old fluid on a regular basis (it really stinks because when the fluid is forced through the dampening orfice it gets hot, which causes it to break down.) When the fluid has broken down it loses it's viscosity and damping goes away. As a bonus, the lubricating qualities decrease, causing wear, which adds particles to the oil, making it more abrasive and increasing the rate of wear. On aircraft, there's a regular schedule for changing out the fluid in the landing gear shock struts, it's a really stinking, messy job, but it keeps them from having to be rebuilt or replaced, which is even a worse job. I'd say that on our cars 20K miles would probably be a decent interval. I've found that the fluid has some deterioration at that point, but not much. I have 80K on the shocks on my B and 70 on those of my A doing this.
R. L Carleen

First off, I'll take the advice of those here and go back to 20wt hydraulic jack oil or 20wt fork oil. I haven't driven the car enough to do any damage with the 40wt...just a few test drives.

I believe the rear shocks are ok, but the front left leaks. I'll contact WWA for front shocks when the time comes.

I'm not presenting an agrument, but am curious as to why someone highly respected (I won't mention any names) uses 50wt. It makes me wonder if the culprit isn't more of a mineral/petroleum base thing than an issue of oil viscosity.

I prefer to learn my lessons as inexpensively as possible. Thanks.

Glenn Kendall

Glenn. I, too, wondered about some of this. Back in the 60's I knew a fellow who used STP oil treatment in his shocks. Do not know how the shocks lasted over a period of time. The ride was exceptionally stiff with little movement of the shock arms. It would, quite literally, bounce you up and down in the seats when pulling on to the shoulder of the road. (No seat belt requirements in those days and many cars did not have them.) Since I have always used the factory recommended oil, except for the one time I did not (the first time), I cannot comment on how well a heavier oil will work. For my own cars, I find the arguments posted by Clifton, Fred H and RL to be sufficiently persuasive that I do not need to perform my own experiments.

I have deal with Peter Caldwell and communicated with him a number of times over the years. Overall, I have a very high respect for his experience and knowledge. In the area of lever hydraulic dampeners, I consider him to be the definitive expert. Some time ago, he pointed out one of the long standing myths of MG ownership. One that goes back as long as I have been associated with the cars. We have always noted that one had to use "mineral oil" in the shocks and should not use "petroleum based oils". After Peter claimed this was not a true statement, I looked up the definition of "mineral oil" in the dictionary. "Mineral oil" is a petroleum based product just like motor oil. Another "truth" falls by the wayside.

As to not being able to check condition of a shock by hand, this may be true. When you can, with a properly filled shock, move the arms up and down using the thumb and forefinger, you can definitely say it is bad. Whether such a test is capable of declaring a shock "good", as the common bounce test claims, I do not know.

I'll drop Peter a line and see if he would be willing to write a tech article for posting on my website or some other. If he is, I will make people aware of the fact when it is posted. Les
Les Bengtson

This may be of interest:

http://mywebpages.comcast.net/rhodes/shock.html

It covers in some detail the damper spring adjustment, and also endorses the use of heavier oil.

Les, that would be nice if Peter would help shed the light.
Glenn Kendall

Derek, The link in Glenn's post answers your questions about shim thickness under the springs. FWIW, Clifton
Clifton Gordon

Great thread! Sorry I wasn't able to chime in earlier, I was off for a racing weekend. Most of what you've learned is true.... just a couple of points of interest, I hope. RL... you have an A and a B. Look at both front shocks. They are the same basic casting with identical valves. Which way is rebound, and which compression? (bit like asking the sound of 1 hand clapping) The heavy oil method of stiffening can be valid, but also destructive. There are 3 piston end poppet valve designs. 2 of them seem to be able to withstand heavier oil, the third can't. Fred saw one of those. Really heavy oil may cause the shaft splines to strip away. I would not exceed 30W. There are several designs of valve. Having a supply at hand makes choosing easier. There are 3 large springs. .073, .087, .093" wire (if I recall correctly) Blue, silver, and gold, respectively. There are 3 small springs as well. There are several choices with number and size of valve orrifice, plus some mods that can be done. There are shims that can be added. There is no definitive test method that I know of. We are working on a shock dyno in concert with some racers. The "feel" is the best at the moment, with experience the guide. The "heavy duty" valves that are on the market are actually stock valves for TR6s it seems. I'm not sure, but all of the dimensions match. Remember that a shock doesn't support weight, not even the weight of its own arm, so it will "droop" if left alone. The oil passes very easily throught the orrifices when going slowly... push fast, and there is considerable resistance. When you are manipulating the arm by hand you are checking for consistancy, smoothness, and smooth transition from up to down. The last is checking for wear in the internal linkage and that the poppet valves are working properly. Les, if I could type faster, I'd finish that article. Sorry for the disjointedness, I had several distractions. Hope this sheds some light. Peter
Peter Caldwell

This thread was discussed between 16/08/2003 and 19/08/2003

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