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MG MGB Technical - BGT ride height help

I'm trying to figure the best way of increasing ride height in 73 BGT rear end, and several people have given helpful advice via a recent thread. In my case, new springs have only helped minimally; a good option appears to be to put in longer shackles, provided it's legally sound. I think I'm looking at 15 inches from centre of wheel to bottom of chrome strip. My rims by the way are the Performance minilite style, 14x6 with 175/75 R14 tyres. The problem is tyre rub on LHS wing lip.
Does anyone know of any photos showing rear ride height from side on?? - I would love to look at some options before I settle on my own preferred height.Thanks for any help. John.
John Hall

John,

I don't know what is legal in Australia. Here in the states, no one would thing twice about adding longer shackles to change the ride height. I guess Mad Max is languishing in some Aussie jail now??

I think photos may not help too much because of all the variables with tires, wheels, etc. And, sorry, I don't have any that seem correct anyway. I suppose I could send a pic both sides of my car and you could choose. There is about an inch difference between left and right.

Could you pull your shackles out and shove some wood blocks between the eye of the spring and the frame channel? With blocks of varying thickness you should be able to find what looks right to you. Then put a tape measure to it and make up some shackles in that length.

Charley
C R Huff

John, my 73 G.T. sets 14.5 inchs with new O/E factory springs that I have saved for 20 years. Up ft. I have a set of used R.B. springs BUT I switched the L to the R & the R to the L for the used drivers side always sits lower, but my ft sits 14 5/8 with the used R.B. springs. I am running 185/65/15 tires on saab wheels that look like the mini lite with a 3/8 spacer to set the wheel out were it needs to be. I have made up air shocks on one of my cars, but it take some mony to make the top bracket, mod. the air shocks thatwere used on something else & sometimes the new shock that has the mod. leaks air. Why are you looking for 15 inchs?
Glenn Towery

Thanks Charley - the reference to "legally sound" comes from the fact that I was leaning towards simply cutting and joining together two sets of shackles (each side) to make longer ones, as discussed under the earlier thread (suspension and tire updates to improve handling); I still like the idea and method, but my local mechanic (B owner too) says it is illegal to have a weld in a shackle. Instead, he would simply make up new long shackles to whatever length. Incidentally, your suggestion using blocks of wood to determine preferred height, is exactly what I am doing. All help appreciated mate! John. PS - still hoping a reader somewhere might know of some side-on photos I can look at.
John Hall

John,

If you start jacking up the rear end you will definitely upset the handling, it appears that the wheels you have may heve the wrong offset for a B as 175 section for a tyre is not particularly oversize.

Your current ride height of 15" is about right, I would recommend bending up the lip on the inside of the wheel arches and this will cure the problem without messing around with the suspension and ruining the balance of the car.

I run 6 x 15 wheels with 195/65 15 tyres at a ride height of 14.75" and have no rubbing problems, having had the inner lips modified.

Kevin
Kevin Jackson

Glenn and Kevin - to clarify, the problem of tyre rub on LHS lip, was only noticed recently after we installed new rear springs to cure serious sag on LHS. The new ride height is 14 and a 1/4 inches all round - so we cured the sag, but appear to have introduced a tyre rub that wasn't there before! By re-installing the springs with a bit of sideways tension applied to the axle from a tie-down strap,(tricky!) we gained about 3mm towards centreing the axle, but it's still about 10mm over to the left. There is plenty of room on the rhs to move the axle over to centre - we just can't figure how to get that movement. The location of axle tube to spring assembly at the central point(with shocker mount) seems to prevent recovery of more than the few mm mentioned above.
So I'm left wondering whether the installation of a poorly made (twisted?) spring might have caused the axle to creep over to one side? Others have suggested stiffer polyurethane bushes might help.I plan to try that, plus longer shackles, because at 14 1/4 inches she doesn't sit right to my eyes - just needs to come up a bit, and that will help greatly with the rubbing problem.
No-one else has reported the same problem - only the inbuilt existence of offset axles at manufacture, about which I was ignorant. Thanks all. John.
John Hall

I extended the rear shackles on my roadster as I was fed-up grounding and bottoming when fully laden on tour. See http://www.mgb-stuff.org.uk/wn_suspensionframe.htm and click on 'Ride Height' for info on this and ride heights in general.
Paul Hunt 2

Paul H. - what a magic job you've done loading up all that info for blokes like me to benefit from. My reason for lifting the rear to about 15", is partly to get around the problem of the rubbing LHS tyre, and partly because I am old enough to remember getting a lift in a mate's new BGT in 1974 from Ashford (Kent) Hockey Club, and the car sat beautifully, rear tyres not obscured by the rear wing. I'll certainly be using the wooden block method to determine the height and therefore the length of the shackles. Was it you who suggested a combination of rubber and polyurethane bushes at the shackle to firm up sideways movement? John.
PS Call me old fashioned, but I'm not keen on bending up the inner lip.
John Hall

I didn't bend the inner lip, nor roll a baseball bat around the lip to flare it out a bit as is sometimes suggested, but I did grind it back a bit. It did little for the rubbing, though, and whilst *harder* springs raised the ride height a bit as well as being stiffer, which reduced the rubbing, it introduced a poor ride and didn't eliminate it altogether. Eventually I swapped the steel wheel axle with wire wheel conversion hubs for a proper wire wheel axle, as that was the cause of the rubbing. Just raising the height with the standard springs could well have been enough to reduce the rubbing to an acceptable level, but I didn't think about that option at the time. Longer shackles probably result in *more* sideways movement than normal due to the increased leverage. Harder bushes may get some or all of that back. I did go poly during my efforts to get rid of the rubbing, but went back to rubber when I fitted the correct axle for the wheels.
Paul Hunt 2

You could try centering the rear end. Most MG sit to eh left from the factory.
I put air shock on mine and can adjust the read height with a compressor.

Steve
Steve

Be careful if contemplating moving the axle to fit the body. It's my belief that the axle is accurately aligned with the front wheels, it is the several panels that come up and round from the chassis rails, over the arch and down the outer wing that are out. Move the axle to fit the body and you could be crabbing.
Paul Hunt 2

Paul,

I know what you mean about aligning the wheels to the body. Years ago with my 100-6 I was getting ready for a 1500 mile trip. I was having something done on a lift in preparation, and noticed that the front end toe was drastically off. I mean like an inch or more. When it got off the lift, I rolled it a bit and looked again. It still looked that much off.

I didn't have time to align it properly (always time to do it twice, never time to do it right) but I figured I could improve it just by eye.

So, I cranked the toe till it looked right. The tires weren't great to begin with, but in 60 miles I wore them down to the cord. Then I took out my tape measure, redid the toe, and it looked just as crooked as before I started.

Charley
C R Huff

Paul, Steve, et al - just got back from a lazy Easter away, and thanks for your input. It's because I'm reluctant to interfere with the front/rear alignment that I want to increase my ride height to about 15 inches. But this weekend I think I'll check the diagonals, front to rear, in case there's a clue to the LHS protruding tyre. I have the benefit of a hoist at home, which will help. After that, it will be time to set up the rear, choose a height, and go ahead with longer shackles. I'll report back via this BBS. Thanks all again. John.
John Hall

This thread was discussed between 15/03/2008 and 26/03/2008

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