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MG MGB Technical - Top rear suspension aids?

I went through the archives concerning this and the newest was 10 years ago. Since then I'm hoping some interesting experience/knowledge/production has occurred.

I rebuilt the whole suspension using poly bushings, new lever shocks, springs. Ride is good just the typical hop and period related issues with the rear. Not flat through corners that's for sure.

Tried tube shocks (quite a while back) and liked the lever better for road which is where it lives. No tracking. Just wondering with all the kits out there including complete new rear suspension geometry if you all settled on several economical ways to help the stock,
Max71

Economical? Leave it alone. My V8 came with telescopics at the rear, I didn't like them, and when the second lot packed up I went back to levers. A pal has had two types on the back of his roadster and has had problems with both - bunny-hopping round on-road corners with the first and rattles from the second, including FOC replacement for one of them. His were fine on a smooth track. What happens with more radical mods I don't know, but then they are getting beyond economical, the telescopics were bad enough for the benefits they brought.
paulh4

Max, like Paul I have been through the whole selection of tube dampers, non of which worked well with the springs. However my V8 roadster has RV8 parabolic springs and their yellow Koni dampers and is excellent and economical. My GTV8 has the Bill Guzman rear end which is superb in terms of ride quality, axle location and anti tramp. My only reservation is that it transmits more road and axle noise probably due to having less rubber/poly insulation between axle and body. It uses all the original suspension mounts, only requiring brackets welding to the tube axle. Bill is based California.
Remember shock absorption is what the springs do! Multi leaf cart springs are not the best at this. Whatever you use as dampers, you are still left with the lack of compliance of leaf springs which were just a way of suspending a vehicle and locating the axle all with one , cheap, component. I would hazard a guess that the circular section on the rear chassis rail, where the bump stop is, was put there when originally MG intended to have a coil sprung axle, that is before the bean counters said NO!
Allan Reeling

Max, Here's the link to Bill's site;
http://www.classicconversionseng.com/
Allan Reeling

Said pal has parabolics, and wound them up. Had a second set and added a helper half-spring, but they've started going the same way. Mind you, he has a supercharger, and uses it.

According to various books the MGB was originally to have coil springs, IRS and various control linkages (as I recall). But it was unpredictable and Roy Brocklehurst turned one over in 'enthusisatic' testing, so they reverted to live axle and cart springs, and that is what gave rise to the 'hulls' under the rear lights.
paulh4

'MGB - the complete story' by Brian Laban, p47. IRS was a thought but due to the quantities of live axles being used they prevailed. A live axle with coil springs was fitted to a modified MGA chassis, with trailing radius arms and an expensove Watts linkage, but led to the overturning - 'out on test near the Abingdon factory' no less. Then a cheaper Panhard rod was tried in place of the Watts linkage, but caused rear-end steering and the mounting points kept breaking, and that was the end of that.
paulh4

MG history is just fascinating. I read the car's engine bay is its size because they always thought it would have a V8 in it. Originally, they wanted a Ford V8 and then a homeland one. Cost cutting gave way to the lump.

I'm up for things they wanted to do if it will make it better with years of afterthought and study.

What Paul shared is an eye opener. I was thinking anti-tramp or/and Panhard.

Allan - that link is interesting. They no longer sell the front end which looks like an RV8 and Hoyle. The rear they show is just the anti-tramp? It's shown on a complete coil over.

I knew you all would have common sense comments. I've been studying the rear end and various options for many years....
Max71

Paul, the RV8 single leaf parabolic is a much stronger unit than these flimsy looking things you see on offer. Interesting MG had problems with both the independent rear end and the live axle with coils, trailing arms etc., when Triumph succeeded with the TR4a IRS and the TR7 with live axle and coils.
Guzman and Frontline also succeeded. Sounds like there was a lack of will or some of that internal strife going on.
Allan Reeling

"Let's digress and review for a moment what a Panhard rod is and how it functions. A Panhard rod is a single link mounted parallel to the rear axle with one end mounted to the axle and the other end mounted to the frame or body of the car, usually for the sole purpose of keeping the axle centered. Panhard rods can be made to work great, and they're both simple and cost-effective - but they can also cause problems! Think for a moment of the axle end of the Panhard rod as being positively fixed in space, with the rest of the rod free to pivot around it. When the car goes over a bump, the body end of the Panhard rod must move up and down relative to the axle. Since the rod is rigid and has a fixed length, the body also gets shoved a little bit side-to-side as the rod-end swings through an arc. A longer Panhard rod induces less side-to-side motion for a given amount of up-and-down motion. (Take a ruler and compass to some paper if you need to prove this to yourself.) Thus, Panhard rods should always be as long as feasible!

By not using a Panhard rod, the Classic Conversions 4-link has avoided the induced steering effect on bumps that MG engineers reportedly had with their coil-sprung rear suspension prototypes."

Allan - that kit is sounding really good. Paul, are you aware of this one? Normally, I'd be worried about the coil over in an MGB but this one is sounding well thought out and working quite well.
Max71

Max,
Yes the Panhard has it's limitations as you pointed out. Longer is better, but it also works better on suspension with less travel. Maybe why MG first experimented with a Watt's linkage, an altogether more complex (and weighty) device.
Another advantage of the Guzman set up is that all the links are adjustable for length. This allows really accurate, 4 wheel alignment to be carried out. A capability which is really useful when you consider the in-built inaccuracies the cars came out of the factory with, plus accident induced ones, plus the vagaries of the leaf springs.
Allan Reeling

Allan - I'm breathing hard on that setup. I think I saw it years ago. Just no feedback on it. Sent them an email this morning. Waiting on a reply. Sure went up since the review - like everything else.

"My only reservation is that it transmits more road and axle noise probably due to having less rubber/poly insulation between axle and body."

Think there's way to fit some poly in there to tame that? I'll ask Bill.
Max71

Max, The supplied bushes are hard plastic. I substituted fast road poly bushes for all but the front trailing arm bush. This did reduce the noise intrusion. If you C W & P has some wear, the clunk on over-run and take up is the most intrusive sound. I'll drop the axle this winter for an overhaul which should reduce this......hopefully!!
One of the really interesting improvements you notice, is after the alignment session. The steering feels altogether more positive and precise. Because axle lines are parallel and the off-sets even. This is a vehicle I have known all it's life and has never been in an RTA!! Measured at the steering wheel rim the difference amounted to 2 inches or so!
Allan Reeling

Also in the book is that originally a V4 was intended, which is why the V8 could be fitted to the near standard bay. Another development canned on cost grounds given the volume of B-series usage elsewhere.
paulh4

Allan - everything I've been reading is a rave by owners. Do you have the PN for the bushings? Several people have commented on the clunk. I rebuilt the drive train, all poly in the rear but seems like most will go away. I'm also quite excited about the prospect of being aboit to align the rear. Just have to pull the money and find someone here who can weld and not charge me a load to install. If not welding I could do the install.

Paul - I don't know if I've ever heard of a V-4 but the ultimate is a V8 you lucky buggers. :)
Max71

Allan - talked to Bill. He was kind of adamant to use his bushings rather than poly. What's you experience? Did you put in poly or just stayed with supplied?
Max71

Allan
I've been following this thread with interest being a leaf spring fan
Could you explain to me please your comment
" Measured at the steering wheel rim the difference amounted to 2 inches or so!"
Were you driving around with your wheel off centre before or was it off after, I just can't understand---and want to-----

On my hillclimber , the best setup I had (after years of testing) was 110lb leaf springs with an extra half leaf in the front half gas shocks and no linkages at all except for a large double acting gas shock mounted from the floor up at about 30deg to a mount on the top of the axle housing to stop axle tramp under acceleration--gripped everything in site
willy
William Revit

"One of the really interesting improvements you notice, is after the alignment session."

What was changed on the alignment session? As William asks, were you driving round with the wheel off-centre before, or afterwards?

Tracking alignment *should* be done with the steering wheel held in the straight-ahead position, then each TRE adjusted as required to get the correct tracking and alignment with the rear wheels (had my ZS done this morning). Cheapo places may well only do one TRE, and leave you to sort out the steering wheel. But really what should be done even earlier is to check the lock both sides, and position the wheel mid-way regardless of whether it is 'off-centre' or not, then clamp it there and adjust the TREs, then adjust the wheel/column UJ.
paulh4

Yeah
Having a wheel alignment on a real machine is the single best thing you can do to your car specially on moderns with stability control, traction control, etc and the steering wheel has to end up dead straight afterwards or you have wasted your time-and best done by the dealer of the particular make --------because
the local tyre service/wheel aligning experts very rarely reset the steering angle sensors on these cars and it creates all sorts of problems with ABS units operating at weird times and even auto trans problems---example

I did an 4Xalignment on a 6 speed auto Falcon that had been having issues and was very happy with how it tracked down the road on my roadtest (round the block) and returned it to the customer who drove me back to the workshop, with a big grin on his face he said that's the first time it had felt right with the wheel straight and all--
Next day he was back, He'd been out on the highway and the auto wouldn't change into 6th gear--what had I done--well with the test gear hooked up -no dtc's ,so out the road to check wheel speed sensors etc and found that although the steering wheel was straight it was showing 5deg off--someone had previously calibrated it with an off centre wheel
recalibrated the steering angle sensor and bingo all of a sudden it changed into 6th gear ok --the stability control had picked up on the steering angle but the car was going straight ahead so it was trying to limit the speed by not allowing 6th gear

Bit off subject but I thought you might like a little read

willy
William Revit

As always quite interesting. Can't speak to something I don't own yet. Having push back on some shops here. I just need the welding done. There's a race shop down the street who does alignment on race cars as the track is only a few miles away. They're confident if I can it on the car they can adjust.
Max71

Sorry been otherwise occupied for the last couple of days.
Answers;
1) No i wasn't driving round with the wheel off centre. The front tracking had been accurately set when I re-built the car with a Hoyle front end. As you say wheel centred. The steering wheel is set while doing the front tracking, however any steering effect from the rear, or lack of it after the set up, only shows up on the road.
2. When I installed the 4 link set up, my alignment method, for the initial set up before the alignment session, was to laterally adjust the links to place the prop shaft dead centre in the tunnel, and make the long trailing links exactly the same length, as per the front half of the semi elliptics.

When measured on the laser set up with the prop in the middle of tunnel, (measured accurately I have to point out) the axle offset was 8mm. i.e., the back axle was shifted left 8mm! Crabbing!
And even with links set to identical lengths, the axle lines were not quite parallel, also 8mm out.
From these measurements one has to assume that the chassis alignment and the front spring eye positioning, were not stunningly accurate from new, as having known the car from it's first ownership, I know it was never involved in a shunt, during his ownership.
However as a BL press car who knows whether a "scribe" or a BL operative, had an off while testing, prior to the V8's release!!!



Allan Reeling

Thanks for the reply Allan, I just wasn't quite sure where you were coming from
Cheers
willy
William Revit

Another aspect of the perennial axle offset wrt the outer wings could well be that the prop-shaft isn't dead centre in the tunnel. However I would say that is irrelevant for two reasons, the main one being that the rear wheels should track the front wheels - that is they needn't necessarily be exactly behind them, but any offset should be the same both sides, and the wheelbase should be the same both sides. With my 1/2" or so offset I dropped verticals from all four hubs and measured track both ends, wheelbase both sides, and both diagonals, and the diagonals were within 2mm. It's the multiple panels between chassis rails that carry the mounting points and outer wings that are out, on my car at least. The side with the narrowest gap to the wing has that wing visibly bulging out over the wheel, whereas the other side is much flatter, look at the angles and spacing of the reflections in the attached, which has the spirit-level against the end of the hub. That, plus the tyre to wing gap, indicates that somewhere, or in a succession of places, things are probably getting on for an inch out! No sign of accident damage in the boot or underneath.

The second reason is that the UJs need to be at a slight angle or they will wear rapidly. Whether that angle is vertical, horizontal, or a mixture doesn't really matter.



paulh4

Axle in the middle of the tunnel was as it was with the original springs on. This was one of the datum measurements I took before I dismantled the old set up. The others were the front spring eye to axle centre and the gearbox flange angle from vertical so that the axle flange could be set to the same angle.
Allan Reeling

Allan - spoke to Bill who was defensive on the bushings. I trust what you're saying. Do you have specifics on the fast road poly bushes?

If I get the kit I want to have everything ready to go.

Still searching for welding shops who understand suspensions. Got the install instructions. Not sure the part about the welding is a definitive schematic, specs on placement. Seems like its pretty important to get them right and exact.
Max71

Max
Just out of interest--
What welding has to be done-on the body itself or completion of the kit
Your bodyworker mate- is he a painter or a restorer- he might be the man for the job or know someone-----
Cheers
willy
Ahhh--just had a look at the kit and yeah it's the brackets on the housing for the top arms---same still goes, any bodyworks with a mig welder should have someone that could do that for you--just a tip- if the brackets need a little finishing off to get a real neat fit, do it--preparation is the key, you need the brackets to fit up perfectly before you weld--the lesser amount of weld you put on the less shrinkage in the weld and the stronger it will be
William Revit

Max,
Will look up the invoice for the bushes tomorrow. Bill was a bit defensive when i told him too, probably because his hard bushes give the ultimate axle location. My argument was that a slight compliance was acceptable and haven't noticed a problem so far The main noise transference i experienced was the CWP "clunk" on over-run to take up and vice-versa. If your axle is in decent nick you might have less of a problem, anyway it's only half a day to change them!!
The welding is a simple job, and is almost the last thing to do, once the brackets, dampers and control arms are in place. The brackets are bolted to the top control arms and with the axle roughly in position, as determined by your initial measurements, they are placed on a cleaned part of the axle, an even distance either side of the dif housing, then tacked. The bolts are taken out of the control arms and the axle swung down. I made a couple of spacers and bolted these in place of the control arm, the welded the brackets in place. Just as a belt and braces I also made a couple of triangular "side" reinforcements and welded these in place.
I have finish servicing the GT this weekend and will take I photo, if you wish, while I'm under it!!
Allan Reeling

William - he's now 1500 miles away otherwise, great idea.

Allan - I had the diff rebuilt a couple years ago. Seeing how easy it is I could have accomplished it. Should be fine though. Drive train is in good shape too.

Pics would be great and any other info. After thinking on it I came to the realization that you just wrote. For alignment, its best to have welding done last. I was going to have it done first then do all the wrenching - not a smart move.

Still trying to figure out the total. I really want to do it. I've been wanting a better rear suspension for many years. But you have the smokin' front suspension as well, right. Even with the old front suspension I lose the rear too often even after being fully rebuilt with poly.
Max71

Max, Just one of the reasons for changing the front was to reduce the castor angle and thereby reduce steering effort, there are other reasons of course.
You could reduce the shipping costs and maybe the total cost by providing the coil over units yourself. They are pretty stock items and i'm sure Bill will give you the spring poundage and damper free lengths.
Any help I can give, you're welcome to it.
Allan Reeling

Allan - appreciate your help and advice. A couple photos and parts list for the poly would be great. He's actually just a state away and has a discount running until the end of the month. Hoping to take advantage.
Max71

Also in the book is that originally a V4 was intended, I can remember on one of my visits to the factory they had a BGT with a E series fitted in the rear, this was something else that never got into production.
Andy Tilney

"BGT with a E series fitted in the rear"

"The second concept for the MGB replacement was worked on in the early seventies and was very futuristic in appearance. ADO 21 as it was known only ever made the clay mock-up stage. It was proposed that this car should be powered by a mid engine and an experimental chassis was made up using a 1750 Maxi engine mated to a highly modified MGB GT shell that carried strut front suspension and a De Dion rear configuration. Unfortunately this design exercise was shelved in favour of those submitted by Triumph for the BL corporate plan for the seventies."

http://www.mgownersclub.co.uk/mg-guides/mgb/mgb-convertible-roadster
paulh4

Max, Have, at last, found the "Bush" invoice.
They are all (the 6, not including the front bearing on the trailing link) Powerflex PF99-111.
Body dia =28.94mm, under head length = 12.5mm, head is, dia = 34.5 x 4.1mm, sleeve is 34mm x 10mm bore.
I can't remember whether I had to enlarge the sleeve bore, i.e. whether Bill supplied metric or imperial bolts, or whether I added a shim washer between the two halves of the bush.
Hopefully have a pic tomorrow.
Allan Reeling

Max, As promised picture of the axle brackets. Also worth a mention is that you will almost certainly have to relocate the axle breather. Some have moved it to the cover, but I removed the oil and cover, plugged the hole with the end of a bolt and drilled and tapped a new location. Removing the cover allows washing out of swarf! The end of the bolt gets welded when the brackets are being done.


Allan Reeling

Max, As promised pictures of the axle brackets. Also worth a mention is that you will almost certainly have to relocate the axle breather. Some have moved it to the cover, but I removed the oil and cover, plugged the hole with the end of a bolt and drilled and tapped a new location. Removing the cover allows washing out of swarf! The end of the bolt gets welded when the brackets are being don.


Allan Reeling

Thanks for the tip on the oil breather. I didn't have any idea about that.

And thanks so much for the part numbers! Really appreciate the effort.

Paul - incredibly fascinating! We all lost out on Triumphs, triumph.
Max71

Allan - how did you drill and tap without getting the shavings into the axle?
Max71

Max, Read my post it explains. You can do it by using a very slow drill speed with a drill and tap liberally coated with grease. But removing the cover and oil is not a big effort and allows you to flush out any swarf ingress.
The bolts, by the way are imperial, i.e.., 1/2" dia.
Allan Reeling

thanks!
Max71

This thread was discussed between 21/07/2017 and 31/07/2017

MG MGB Technical index

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