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MG MGB Technical - Panhard Rod vs. Watt's Link

Has anyone tried installing a Watt's Link on a B? It seems like a great solution to stiffen the rear end without the arcing travel of a panhard rod. But I don't know if it's even possible without a lot of custom work. Opinions?
Steve Simmons

Why?
John
John Simmers

Why what? Why consider a Watt's Link? Because it looks like a better solution to the same problem. The Panhard Rod would travel up and down with a slight lateral arc, which can potentially bind suspension parts and cause stress. Watt's Links do not. But I just learned of Watt's Links so I'm not entirely sure it's the proper thing for an MG.
Steve Simmons

Steve,

What are you trying to do?
A Watts linkage only locates an axle against sideways movement. It has no effect on stiffening the suspension.
This sideways locating is now carried out by the leaf springs.
If you were fitting coil springs to the rear a Watts linkage with trailing arms giving fore and aft location would be the way to go.
You could then stiffen your rear end by choosing the correct coil springs.
This has been carried out many times, but it is a lot of work and only for the really serious competitor.

Mick
M F Anderson

Hi Steve

I agree that a Watts linkage will do a 'better' job of locating the rear axle than a Panhard rod. The problem is that the centre link on a Watts needs to be located somewhere on the differential housing, and having done that, location points need to be found for the outboard ends.

The trouble with a B is that neither the diff housing or the general construction of the rear underside make it easy to fit a Watts link, although I have no doubt that it can be done.

In comparison, a Panhard rod is simpler, lighter, and easier to make and fit. There certainly is some side to side movement introduced, but this is less than the movement that takes place using a standard rear leaf spring setup anyway, and the movement is beter controlled, so there is an improvement in axle location control which leads to better handling.


Cheers

ian F
Ian Fraser

There is a certain amount of rear end deflection (in relation to the body) on most leaf spring setups
and a Watts Linkage or a panhard rod would limit this and would greatly improve rear end location
accuracy when encountering great sideloading in turns.

Although not impossible, fabricating a Watt's Linkage would seem to be a daunting task on a "B"
and would probably not show all that big of a lap-time advantage over a panhard bar design.

Besides being more complex to design, build, align, and maintain. The axle presents it's own set of
engineering problems. Traditionally, a Watt's linkage would have a pivot arm mounted to the middle
of the rear axle gear housing. If your have a tube-type axle, this means mounting it to the rear cover
- which I would not recommend. The cover is too thin for this, and some of the side loading would be
tranferred through the cover gasket and could cause all sorts of oil leaks. Also, the pivot bolt would
be less than inches away from the fuel tank. If anything should go wrong (collision, loose bolt, etc.)
- that pivot bolt could pose a puncture risk. Not good. Of course, you can work around some of
these problems by mounting the pivot arm off to either side of the gear housing by attaching it to
either side axle tube, but then you'd be left with an asymetrical setup.

K.I.S.S. - Keep It Simple S_____

If designed well and fabricated carefully, a panhard bar would provide a good amount of sideways
location accuracy, it's easier to fabricate, setup and maintain, is lighter, and there are fewer parts to
go wrong. Any deflection coming from it's travel arc could be minimized with proper and careful
design work.

My 2¢.
Daniel Wong

You might be the first one to have a Watt-linkage on your car Steve, and it is a better way to do it than a panhard-rod (more expensive though).
Maybe it won't be such big difference in reality but don't underestimate the placebo effect.
After some thinking I believe that everyone needs a watt linkage. I might try to fit one after I have gotten that Burgess head, tubeshocks in the back, coil over, gotten rid of all rust, won on the lottery ...
Jesper

Another problem with the Watts linkage is mounting it in such a way that the roll center will be low enough, yet allow you to maintain some road clearance. A wishbone is a better solution if the sideways arc of a Panhard rod bothers you.
George B.

Steve,
Give Joe Huffaker a call at 707-935-0533. He offers a rear suspension kit for midgets that has Watts linkage, he could surely build one for a B.
Leland Bradley

MF, the point behind this project is to reduce as much as possible lateral movement of the rear axle. I just installed wide tires and don't want any rubbing on the arches.

There are certainly good reasons listed here for not using a Watt's Link. I thought about the road clearance problem but my limited knowledge of these things couldn't rule out a work-around. It sounds like a Watt's Link may be a bit too involved.

Leland, I'll give your contact a call and see what he has to offer. Thanks!
Steve Simmons

I just had this conversation with Ted Lathrop of FastCars, Inc (Michigan) and Dan Masters of Tennessee.

Ted favours the Watts linkage over the Panhard set-up, but...also feels that with proper springs AND bushes, it is likely that neither would really be necessary.

I questioned these gentlemen because I am in the middle of a V8 conversion on a 1974.5 MGB/GT V8 and was concerned about lateral movement of the differential..

I trust their opinions....

Just my humble input.

rick
1978 mgb
1969 mgc
1974.5 mgb/gt V8 conversion
rick ingram

You might wish to consider two other options, both of which are supposed to locate the rear axle, prevent wheel tramp, and give a low roll center:

Rear Traction Control Link available for the B from Frontline Spridget, although It isn't pictured on their web site.
http://www.mgcars.org.uk/frontline/index.htm


A V-link /Articulated A-arm /Wishbone Rear Axle Housing Locator, that you will have to build yourself, although a kit is available from Jegs.
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=4129&prmenbr=361

Regards,
Jerry

Jerry Causey

Anyone out there with experience of building a Watts linkage?

Do the outer locating points have to be in line with the central pivot at rest, or can they be mounted higher?

The problems of the central pivot can be overcome fairly easily, but the outer mountings would have to be located on the chassis rail over the axle and springs.

I can't see that this matters as long as the arcs described by the inner ends are identical - which rules out the assymetric design referred to above.
Chris Betson

I added Doug Jackson's panhard kit (the new generation is out now) and was astounded by the immediate improvement in handling. Jackson's set up has minimal arc and is located very solidly with substantial bracketing and parallels the axle optimally. The surprisingly large amount of flex in the springs and bushings was never noticed until it was gone. The panhard allows the fitment of 205/50/15's without rubbing. In my case, these tires are on bolted 15x7 inch Panasports on a wire wheel axel with bolt on hubs and 1/4 inch spacers to fine tune the spacing. This is with 22mm offset wheels, as stock. One consideration for a road car is the transmission of noise through the panhard rod. I have heard very good things about the V-link set ups but have never actually seen one. Dean
Dean Lake

I looked into Doug Jackson's kits, but unfortunately he doesn't offer one for banjo axles and has no intention to do so.

I hadn't thought of road noise. Anyone have experience with the increase in noise from a panhard rod?
Steve Simmons

Jerry is right; Frontline's Rear Traction Control Link is very interesting.

I saw it on Roger Cook's (he of TV fame) car on the Frontline stall at Silverstone.

They don't seem to have gone into full production yet, as I asked that they contact me when they had a full written specification and a car available for raod test. I must "chase" them again my 220 bhp V8 needs more control at the rear.

NJSS
Nigel Steward

I've got a datasheet for the RTL from Tim Fenna (Frontline) that I got a while back. Looks very good but at £365 is beyond me at moment. If anyone wants a copy give me your email and I'll send it.
Stuart Robson

Chris,

If you want details of the technical issues with watt linkage alignment, I recommend Alan Stainforth's book the Race and Rally Source Book. Its a few years old but its good for that type of thing. This book is available from the normal car book sources in th UK.

David
David Witham

Steve,
There will be an increase in road/mechanical noise as you have added another sound path; more if you use metal connectors vs rubber. On my car, I use a body mount like Doug's and welded an mounting ear to the spring plate, this gives you longer Panhard bar for less arc.
Leland Bradley

I have installed Doug Jackson's panhard bar kit and I was very pleased. At first I too wanted to build a watts linkage as it is the "perfect" way to keep the rear axle centered. However all the problems that have been mentioned above swayed me back to the panhard bar. As the bar is as long as it can be and there really isn't much suspension travel in the rear, the arc movement is negligible. There is probably more sideways defelction in the tire sidewalls than you will find in the panhard bar.

-Jared
Jared Snider

Good point.
Steve Simmons

A traction control bar has nothing to do with a Watts or Panhard rod linkage.

If you replace leaf spring with coil springs you still need some form of lateral control which is where the Watts Linkage or Panhard rod comes into things.
Daniel

A Watts link seems a bit of overkill to an already "located" rear end. This site has a good, inexpensive universal kit that can be adapted to most any application.

www.tperformance.com/street_rod_store/3100/watts_linkage_kit/
Chris Butler

Daniel

The traction control link name is a bit misleading. I've posted it to your email so yhou can have a look. Its not as suggested a type of antitramp setup.
Stuart Robson

I checked out this site...

www.tperformance.com/street_rod_store/3100/watts_linkage_kit/

It is interesting...and inexpensive. Additionally, they had infomation I needed for my Ford 8" differetial!

rick

rick ingram

Thanks to Stuart I now have the drawing and text. Despite what Frontline appear to claim they did not invent this out of thin air. As far as I can tell all they have done is produce a Michael Mumford type linkage for the Spridget which appears in Racecar Engineering, 1994, Vol 3 No 5. It is possible I even told Frontline about this some years ago. The system is one that appears on a lot of Mallock single seater racing cars. The frontline kit does appear to have additional triangulated linkages that I can't see a lot of benefit for because while they will improve axle location won't eliminate axle tramp. Anti tramp bars do eliminate axle tramp and provide improved axle location so my preference would be anti tramp bars and just the Mumford linkage on its own.
Daniel

i found this link,
http://www.griggsracing.com/ART/Guy_Watts_Link.jpg

looks like a lot of overkill, is there any room for all of that.. i know i'm in a tight situation just fitting a rear sway bar.
Dave

Why would you want to fit a rear sway bar on a live axle car?
Daniel

If one were to make a new diff cover, so that the centre pivot were part of it, do you think it would be possible to get enough load on the ring of bolts to stop it fretting and leaking oil?

Or, would something completely separate be needed, with its own attachment to the axle? The tube axle has those two sockets for the stretching tool used when setting backlash, perhaps they could be used along with some kind of clamp?

I've seen some spectacularly dodgy-looking panhard rods on Bs at various shows, which I'm sure I could break with a week's normal driving. At least with a watt's link everything would be working in shear like it's supposed to.

Is there any space to move the tank back a bit?

ttfn,
--
Olly
Oliver Stephenson

Hi Olly,

I reckon it is possible to mount the pivot on the axle using the securing bolts - the top ones are double ended to take the pipe clips - using this type of fixing would allow you to bolt on a carrier for the pivot, separate from the cover.

My understanding of the linkage ( an looking at a Watts link on a land rover) is that the pivot is in the centre of the AXLE - not the diff cover, since the diff is offset on the axle.

So, the pivot could fit in the recessed part of the cover and be well clear of the tank.

I am going to make up one to fit my V8 sometime - I'll post the results. May even sell them on as a kit!
Chris Betson

Ooo, that's cool... I didn't realise that the diff was offset enough to have the pivot point completely in the shallow part of the cover. I assumed it would overlap the bulge a little. I guess you'd have to use all of the securing bolts though, as otherwise you'd snap them all off when you hit a pot-hole when going round a corner :o)

If you come up with a good kit I'll be interested... I'm planning on fitting MGC 5.5" wire wheels with 205/65 tyres, which will need plenty of location on the axle.

I'll also be sorting out my anti-tramp bars, which I designed last year and never got around to making.

ttfn,
--
Olly
Oliver Stephenson

Olly
Can you share details of your anti-tramp bars?
Bob

Bob, I can indeed, but I've not tried them on a car yet so it might be a bit premature.

All the motion's worked out from first principles though, so I don't forsee any problems. Perhaps I'll put the info on my web site at some point...

ttfn,
--
Olly
Oliver Stephenson

Can we go back to Daniel's question ... sway bars on a live axle. I put a set of hefty bars on my CB car having had a chance to ride in and briefly drive Glen Towery's car ... handling was just what I wanted. He runs a really huge set of bars, if memory serves called an Evolution III set with a 1" front and a hefty rear. I couldn't find those so I just put on the Hopkinson set, which is 7/8" front, 5/16" rear. The handling is just great, and if memory serves fairly similar to Glen's car.

As I understand it, the main objection to a rear bar is, when you're in a hard turn, the bar is pulling the inside wheel up, thereby compromising its traction and forcing the outside tire to do all the roadholding. When the outside tire reaches its traction limit, the whole thing will go.

And this seems pretty much the case ... with the heavier sway bars, in a very hard turn, the car will corner beautifully but then if you keep at it without all that much warning the rear will step out. Without the rear bar you have a better warning that you are going to break loose ... the car feels leaned over, squealing and squawking and then gradually segues into a slide. Still, it's not night and day or anything.

But what I don't get is why it matters whether you have a live axle or IRS. Even with IRS, the bar would want to lift the inside wheel in the same fashion, no?
David D.

Personally, I cannot see the point of a Watts Link. I thought that the general consensus is that the rear of an MGB doesn't contribute much to the overall handling.

In fact, I struggle with the whole idea of non-period modifications - if you want a car that goes like a Golf GTI then buy a Golf GTI and save yourself some cash!

Anyway, it seems to me that it should be possible to fabricate a centre pivot which would mount on studs from the axle casing itself (ie replacing, say, 4 of the bolts). The load would then be transmitted through the casing rather than the cover. Someone needs to do a bit of thinking on the stresses first, because the pivot is going to take a lot of load.

Neil
Neil Lock

Neil, people have been putting panhard rods, watt's links and anti-tramp bars on their cars ever since someone first thought of souping up a production car. This goes way back to before our beloved Bs were ever made, so I don't think that these mods would be considered 'non period'.

Sometimes I agree that people go way too far with modifications to Bs - for example, the £2000 IRS setups that are available. Like you say, buy a car that already has that. However, the hobbyist can make any one of the aforementioned mods for a hundred quid or so, and that's not a big part of the cost of the car, so I say go for it.

To David, I can't think of a good reason why any suspension setup should favour an anti-roll bar, except perhaps if your axle moves sideways a lot it might bend it. With a watt's link I guess it's all equal :o)

ttfn,
--
Olly S
1934 Morris 8 / anti-tramp bars / 0-60 in 4 seconds!
Oliver Stephenson

Olly,

Although anarb will tend to reduce grip lifting inner wheel, it can increase grip by controlling camber change, which is fine at front or with IRS but doubtfull with a live axle, which I think was Daniels's point.
Also a very stiff car front and rear bars in UK winter's may be a bit of a handful.
There are other ways to control roll, lowering CG etc, what is interesting re Frontline kit, even if old idea, is that it is possible to change and adjust roll axis.As I've misplaced my Racecar Engineering, 1994, Vol 3 No 5. any thoughts Daniel?

Paul
Paul

Paul, very good point. I had forgotten that IRS would have your tyres tilting themselves off the road.

I like beam axles :o)
--
Olly
Oliver Stephenson

This thread was discussed between 11/02/2003 and 21/02/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.