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MG MGB Technical - Anyone have GT Rear Springs on a Roadster?

I've read alot in the archives about GT springs on a CB roadster but still haven't seen much real experience except for Paul H's, he had them on and the ride was too firm. Since my left tire can sometimes hit the inside lip of the fender I'd like to raise the rear about an inch. Are GT springs really any different than rdstr springs except for the extra leaf? Especially since these are aftermarket springs we are all buying. Any experiences or trials-by-fire appreciated.
Sam Sullivan

I have GT spring on my 70B roadster. They were a used pair I had laying around. The original springs had sagged and I didn't want to get new ones. It raised the height from the sagging originals but not above what I would consider a normal height. The ride is firmer, but over firm. I have no plans on changing them anytime soon. I would guess new GT springs would be different than used ones.

HTH

Ron
Ron Smith

Sam,

I would suggest that you fix the problem at source by moving the spring hangers on the axle and fitting new ones. I had the same problem as you, the LH rear wheel would touch the rim of the wheel arch during 'bump' conditions. Removing and replacing the hangers, turned out to be quite easy, much less trouble than finding good springs!
MG Mike

I fitted GT springs to my 64 B maybe 10 years ago. The thinking was that the GT springs were less likely to sag over time. It has ridden a little high in the rear ever since. Last year I installed lowering blocks to get the ride height to a more acceptable level. I would recommend going with the roadster springs.
..Ron
Ron Bland

Mike-
Technically speaking, how did you move the hangers, did you reuse the same ones. Doesn't that throw the front-to-rear out of line?
Sam

Hi Sam,

Take a look at;-

http://digitalvault.bt.com/invite/login?c=313036363038&i=7530c-111535d63d0-gemini02&t=fb89d5154bb8bb5d&r=mg&lang=en

http://digitalvault.bt.com/invite/login?c=313036363038&i=7531c-111535d63d0-gemini02&t=ff612628c792f868&r=mg&lang=en

The pictures in the links are fairly self explanatory…you remove the old hangers with a grinder, make some new hangers (link to drawing attached above) from 2 short lengths of 2"x2" box section mild steel. If you are not up to making the brackets yourself, If you give the drawing to any small engineering firm, I'm sure that they could make you two brackets for a very small sum. The only 'tricky' bit is welding the brackets back on in the right place.

1) As all MGs are 'different' my advice would be measure the gaps between the lip on the wheel arch (fender?) and the side wall of the tyre using a plumb bob, for both LH & RH sides.
2) Once you have removed the axle, measure the distance from the back-plate to the spring hangers for each side.
3) Add the two measurement from (1) (LH+RH) divide by 2 and weld the new hangers to this offset. (so if you have 2mm on the LH side and 14mm on the RH side, move both of the axle hangers 8mm to the LH side)

I doubt that the " front-to-rear" will be "out of line", if it was ever in-line in the first place, the diff is off-set in order to have equal length drive shafts, if your body shell is straight (like mine is) the axle was out-of-line the day it left the factory, is it now much better than it ever was. You can check this by chalking out the datum's with a plumb bob on your garage floor, and measuring the position of the spring hangers on the axle. I've noted up to 7/8" difference between hanger positions on axles. This accounts for the many MGs you see with the same problem as your own and mine! I only moved mine 6mm but it makes all the difference to the looks and it stops that very annoying tyre rubbing!

Oh, add to the repair bracket for Axle rebound strap mounting (part number ARB101) and you have a perfectly located axle!
MG Mike

Thanks for all the detail Mike. This just may be next winter's project. Have to find a fabrication shop to do it.
Sam

Sam,

May be new springs is not the solution to your problem, but I have used GT rear springs on my ´63 roadster for four years now, and am quite happy with them. The ride may be a little firmer, but nothing dramatic. The rear felt a bit restless at first, but that turned out to be worn dampers. From memory, ride height is 14.5" from wheel centre to bottom of chrome strip.

I know several other Norwegian MGB owners use GT springs on their roadsters. We use our car for many long runs with a lot of luggage, and it is very comforting not to hit the bump stops all the time! But it may be a problem that so many aftermarket springs are now too stiff, too high and generally of lousy quality. I was lucky to find a pair of original new old stock Unipart springs

Tore.
Tore

If the rear wheels are tracking the fronts now then something else is wrong. And if they aren't either the chassis rails are twisted, or the springs are bowed to one side. So many MGBs have this offset (all of them?) that it has to be a design/jig/manufacture fault, and I really can't see it being the chassis rails. I've had a full tracking check done on both mine and neither are crabbing, but both have the axle offset to the left. Moving the spring hangers or axle pads is simply going to make the car crab, even if it *does* centralise the wheels in the arches.
Paul Hunt 2

Mike-

If you get a chance could you email me - I need to ask you about the brackets.

Thanks
Sam Sullivan

Hi Sam, no problem, email sent to "sullivas@optonline.net", hope it gets to you!
MG Mike

I am with Paul on this one - the axle and chassis rails are correctly aligned - the problem lies in the bodywork panels and is probably a jig issue - I wonder if the heritage shells have the same problem?

Cutting the axle mounting pads off and rewelding them is a bodge and not recommended.

Chris at Octarine Services

Hi Chris,

I agree that each individual car should be assessed before undertaking any changes to the geometry of the OEM set-up.

In my case I did just that. My body shell was absolutely spot-on. I levelled the car and dropped the plumb lines from the chassis datum points (as per the workshop manual)and marked these on a level surface. Using this method one can check if the chassis is parallel, the centre line and diagonals. I was actually surprised to find that my bodyshell was spot -on.

I also checked the panel fit as you allude to, by dropping a datum from the outside of the rear panel, not a datum point but a good indication. This too was spot-on, so in my case the problem definitely was the axle.

I was a bit sceptical but assured myself after measuring several axles at an MG autojumble and finding that the Spring Hangers were all at different positions on the axle. I boubt that MG or BL 'matched' axles to bodies in order to achieve the correct set-up.

Given all of the above, I had two options, find a replacement axle that 'matched' my car, or replace the Spring Hangers.

I don’t agree that fitting new Spring Hangers is a "bodge" only if it is done in a "Bodge" way.

The OEM Spring Hangers are welded the tube axle in the first place, removing them to relocate new ones is a perfectly good engineering practice. The strength of the axle and spring hangers is not being compromised and the design of the new hangers is dimensionally the same as the OEM ones. This task could be easily achieved by any good competent engineer.
MG Mike

Mike-
Just so we'll know how to check, what is the correct dimension on the axle for the spring seats? How do you measure it?
N. G. Phillips

Hello,

The tube axle is exactly 48" (4ft) from flange to flange in width. The Rear Spring -Front and Rear mounting datum width is 37" (centre to centre), so in order to centrally locate the axle the Spring Hanger 'centre line' needs to be exactly 5½" from the tube axle flange. Take care not to measure from the drum back-plate as this is approximately ⅜" wider at each side due to the Hub Bearing retainer. Oddly enough, the outside edge of the drum brake back-plate is also 48", so if your back-plate is not distorted, you could use this as a point to measure from when fitting new spring hangers.

An added benefit to my car was also that the Axle check straps lined up between the chassis and axle for the first time ever!

Regards,

Mike.
MG Mike

According to my information the tube axle for steel wheels is 48.5" flange to flange. The wire wheel axle is narrower at 47".

If the spring pads *are* significantly offset then of course centralising them would be a good way to go. But whilst my old axle has about 1/8" difference this is a lot less than the 1"+ measured at the arches, on both old and new axles.
Paul Hunt 2

I had a look under the car last night and the rebound straps *are* noticeably hanging to the left. The driveshaft is to the left as well. I'm moving forward with the relocation as soon as I can locate a metals fabricator. I am going to have the alignment guys check the front-to-rear line-up first.
Sam Sullivan

Mike,

Any further news re the Jones springs situation.

Kevin.
Kevin Jackson

Hi Paul,

Perhaps I've not made my descriptions of the measurements clear enough. The 'Salisbury' type axle and differential case assembly, when stripped completely, with no axle shafts or bearing retainers is 48", when you assemble both of the bearing retainers this will add approximately ¾" to this measurement if you measure internally from the drum back-plate. I say approximately as the outside edge of the bearing retainer is not a datum, just a cast surface, plus you have the variance of the flange gasket, with or without sealer etc. The inside face of the drum back-plate therefor is also not a datum, although there is probably not a lot in it for this purpose.

The 'Salisbury' or 'tube' axle casing width does not change if fitted with either the wire wheel or steel wheel, the Wheel Flange position IS different due to the different axle shaft and driving flange, but NOT the axle casing itself, this is the same for both wire and steel wheels.

I don’t know about the early 'banjo' axle as I don’t have any drawings for it or one to measure. But this axle too could have either wire or steel wheels.

In either case the axle dimensions don’t change between wire and steel wheels.
MG Mike

Hi Kevin,

Oh boy! Yes I got the springs just before Easter weekend, perfect timing to fit them over the holidays…….

When I unpacked them, one spring was 8mm lower than the other (for a spring with a rate of ≈100lbs/inch, this equates to a difference in static load of 31½lbs.) not acceptable in my book.

Also, there was a clear visible difference in the arch between the two springs. From my initial conversations with Jones Springs I was very clear that my requirements were for a 'matched pair' of springs, again not acceptable.

Anyway, I phoned then up explained my reasons for rejecting the springs and to their credit, they arranged to collect the springs, which they did on Tuesday.

I'm prepared to give them one last chance to provide a good pair of springs, after all, this will be my 6th set of springs, there must be someone out there who can make a decent pair of springs? Besides it must now be costing Jones Springs some money to keep making springs, shipping them to me, only to have to come and collect them again.

I should get the next ones, next week, so I'll post my results once they are on the car.

I wanted the car back on-the-road for April, but it looks like it will be June before I get everything finished, not good when the weather has been so good, especially when you see some other MGs driving about!
MG Mike

MG Mike - are you sure about that? The parts list shows two tube-type axle cases and two types of half-shaft - one for wire wheel and one for steel, but a common bearing cap.

The same goes for the banjo casing, although in that case the half-shafts are completely different at the hub end. Tube-type half-shafts are identical in appearance, but the steel wheel items are longer.

Yes, on the tube axle you can fit steel wheel hubs to a wire wheel axle and vice-versa, but you end up with the incorrect track in both case, with the tyres too close to the outer arches in the former case and too close to the inner arches in the latter.
Paul Hunt 2

Hi Paul,

No I'm not sure! The drawing that I have (obtained from BMH via Ron Hopkinson some years ago) details only one axle casing for the 'Salisbury' axle, there are different higher assemblies for the 'wire' or 'steel' wheels (bearing retainers are common to both as you say), but it looks like the only difference is the drive shaft in the top level assembly.

I'm not aware of two casings (or assemblies) for the 'Salisbury' axle, presumably the difference is in the length of the torque tube? As the diff case casting and flanges are the same?

Anyway, good spot Paul, and important information for anyone considering my previous advice on dimensions, which is all predicated on the 'Salisbury' tube axle for steel wheels.

The bit that doesn't change is the 37" centres between the springs hangers, so irrespective of which axle (wire or steel wheels) you have you can re-position the spring hangers if found to be too far off 'normal'

Mike.
MG Mike

Returning to Sam's original post I note Clausager speaks on page 149 (RH column) of "Roadster reverts to six-leaf rear springs instead of GT-type seven-leaf springs."

I have not searched earlier in the listings but wonder if this means that at some point the rear springs were common to both roadster and GT or (and perhaps more likely) that seven leaves were common with different spring rates for the two applications.

Regards
Roger

Roger T

Yes, the springs were common to both roadster and GT from the inception of rubber bumpers to September 75 according to my research, part number BHH1767.
Paul Hunt 2

Mike,

Dissapointing news about Jones springs I thought after what you originally posted and from my own conversation with that they were a company who were prepared to do the job properly.

I'm now thinking of using the Moss TGS40720 rated at 93lb roadster or 110lb. GT which have the reversed spring eyes, ie. the spring eyes are below the main leaf rather than above it as on standard springs and this will lower my Rubber Bumper car approx 2" which is what I need.

I now have my new front suspension and the Brown and Gammons de-castor kit on the car and have replaced the Argentinian rack with my original one, which I had rebuilt, what a difference, it was like driving a truck before and is now light and positive with good feedback.

http://i41.photobucket.com/albums/e258/castletine/P4060005.jpg

http://i41.photobucket.com/albums/e258/castletine/P4060006.jpg

And a shot of the car.

http://i41.photobucket.com/albums/e258/castletine/P4010004.jpg

Hope you have sucess with the next set of parabolics.

Kevin.
Kevin Jackson

This thread was discussed between 02/04/2007 and 17/04/2007

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