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MG MGB GT V8 Factory Originals Technical - Suspension
|I am just beginning to research converting my 66B to V8|
power. The biggest question in my mind is suspension upgrades to achieve fast road car standard. From what I have read there are upgrades to the stock front end design or there is the option of converting to RV8 front suspension.
My own set up lowered by 1" gives a neutral drive
Negative camber wishbones
3/4" anti roll bar
Anti tramp bar
Rally type rear spring
Front Spring 8"x600lb/in
Koni on rear (at softest setting)
Uprated lever arm on front
I understand that uprated lever arms all round work well.
The RV8 does appear to be a easy option and sorts out uprating front brakes, Wilwoods can be a bit of a pain. The Coil Over option also looks good but I don't know anyone using it.
|I was also wondering if anyone has tried to make a kind of trailing arm suspension to replace the leaf spring and lever shocks with a conventional shock (gasp!) and coil-overs. You would still need a panhard rod or watts linkage, and it wouldn't be as elegant as a jaguar irs conversion, but it would be better than leaf springs, no?|
I wonder about a four bar setup with coilovers?
|Well, i'm trying both. I'm in the last stages of mounting coilovers to the front end. I'm now trying to make an elegant top shock mount. I have upgraded the brakes to: Porsche 911 rotors ~$25ea, and Porsche 944 Turbo Brembo calipers ~$100-150 ea. Of course you need 15" rims to accept the brembo's, and even they barely fit. I believe someone else has made a 4 link coilover rear setup, but can't remember who. I'll start on that in a month or two. Don't bother asking how I did it. I'm not giving any plans until i've tested the setup myself. I'd hate for someone to wreck their car or worse because of my miscalculation.|
|Bill, I am working on coil over suspension for the B (front and rear) Trying to make it affordable and simple to install. Have drawings and ready to make proto type and test. Hope to have it ready by next year so that I can complete the V8 kit.|
One thing about bigger brakes. The advantage of bigger brakes is the braking area is bigger, some 4 pot calipers do not have any more clamping pressure than the stock B caliper when install on a B, in fact some have less.
When installing bigger brakes the master cylinder should be match, and also the pedal ratio plays a big part on the equation.
|Hmmm, ok, so it looks like this is something that actually has been done before. Does anyone know where I can find pictures of such a setup? Or designs? I'm trying to look now on my lunchbreak but I'm not having much luck.|
|Joe, look on htis web adds under Trevor Taylor.|
|Guys, there is a Haynes book out by a guy called Champion entitled something like "How to build a sportscar for under 250 UK Pounds". It basically is a manual to build a Lotus 7 replica but it has some real interesting and detailed drawings and instructions on converting a leaf rear end (Ford Escort) into a trailing arm suspension with panhard rods etc. By the way, I wonder how a Cortina or 2litre Escort rear would go in an MG??|
|Sounds like a lot of work for very little improvement over a well thought out leaf spring rear. Ride height adjustment would be easier with coil overs, but that's about all I can see that would be a large improvement unless you're planning to go racing. Most street tires don't have enough grip to load the suspension to the point of requiring a 'race type' setup. Leaf springs with a properly installed set of traction bars, panhard rod, and tube shock conversion should give you a good suspension without a lot of engineering. |
If you were considering an IRS then the improvement would probably be worth the work and expense.
|irs are almost always heavier than a solid axle suspension. The solid axle system gets even lighter when you go to plastic springs, a 40 lbs weight saving. (5 lbs per spring vs 25 lbs per spring) The irs has a weight penalty in trying to locate the wheel.|
I'v been playing with the idea of a early Nissan 300zx irs differential with axles supported by the plastic leaf spring and a pivot bar attached from the wheel backing to the differential. It would seem to me to be the best of both worlds. Rubber bushings at each end of the leaf spring should allow enough lateral movement to accomodate the change in track width as the axle swings up and down. It could even weigh less than a solid axle system, and have a modern gear ratio. The 84-86 years had the same bolt pattern as the mgb and rear disc brakes. It would still be subject to spring wind up under v8 power off the line, unless the pivot arm was diagonally attached to the body/frame forward of the differential.
|What I had in mind for a trailing arm suspension is actually very simple...It's probably something MG would have considered doing at some point. I am also interested in coil-overs because |
1. they weigh considerably less than the leaf springs
2. no leaf spring windup/reduced wheel hop
3. I can set corner weights as well as ride height
I know it is not as elegant a solution as an IRS, but I'm thinking of keeping things more period-based rather than going all-out. Plus it would be much cheaper. Going to a simple swing-arm IRS (think early spitfire) would be period too, but there's no way I would ever turn my car into an evil handling thing. Anyway, a couple of Turners I've seen use a trailing arm setup using the spridget axle with a panhard rod, and it works very well. That's actually how I got the idea.
I'll be taking the car racing, in case you were wondering.
didn't really intend to start a debate here, I was just wondering if it has been done before. :-)
I believe Maidstone Sports Cars in the UK have a kit: four links, brackets, coil spring, tube shocks and panhard rod. No coilovers but it wouldn't be hard to fabricate an adjustable mounting pad for the coil springs.
Apparently the MGB was designed with coil springs but they were scrapped at the last minute. I believe the space to fit them was kept, the axle already has a mounting pad, the chassis rails also to fit a 8" by 2.25" coil spring.
There are some pictures on MGOC's website under V8 conversions. I believe the car belongs to John Bourke?
Hey -that's me-I didn't know that I had coilover suspension at the rear-you must be getting confused with my front suspension setup where I'm showing pictures of my modified spring pans to take 2.5 dia springs on adjustable platforms.
As you can tell from the V8 conversions site I'm using modified RV8 springs with my own design of traction bar and panhard rod. I'm intrigued by Barry and Joe P. ideas for what sounds like some sort of swing axle partly located by the leaf spring. Maybe you might like to explain in more depth?!
My own idea is one which I believe the factory investigated-ie a De Dion axle. I dont know whether anybody has looked under a Volvo 343? These cars use a develpoment of the old Daf suspension with single taper leaf springs(I haven't checked these out yet). As I'm sure you all probably know a De Dion axle is basically a beam axle but where the differential is mounted on the body to vastly reduce the unsprung mass.
As the Volvo already has leaf springs the De Dion tube should be relatively easy to modify/shorten for our use. In my case it would mean that I wouldn't have to throw away all my current modifications and it is a period solution. One of the major advatages of a beam axle is that the wheels maintain a constant camber with none of the nasties associated with swing axles/jacking/high roll centres. Another De Dion setup to check out is the old Alfetta.
I would use a Jaguar differential as a first choice. As the diff doesn't have to locate the suspension it can be mounted in rubber with CV jointed half shafts.
I see no disadvantage with maintaining the leaf springs -plastic/steel single taper/etc-remember that once you locate the diff on the body the axle does not have to resist drive line torque so no wind up takes place. If the brakes are also moved to the side of the diff- this removes brake torque from the picture and the axle then just sees suspension loads.
The big hassle is of course locating the diff on the body-I'm sure that it would give a very high percentage of the benefits of some of the current IRS solutions at reduced cost. It's notable that when Caterham decided to uprate their suspension design they chose a De Dion design as it is an easy and logical upgrade for a live axle system.
Then again I'm not sure how much of an improvement any of this is over my setup on a smooth road...trouble is the nice roads are generally a bit bumpy....
great comments. I vaguely recall years ago seeing a dedion tube the was not fixed length and had a sliding section. My impression though is that the tube is ordinarily a fixed length. The swing axles would then need to vary in length as they moved up and down. Most of the modern cars with irs have fixed length axles. The gt6 with its rubber donuts was not the most reliable system. Where would the dedion tube go? The space is quite limited between the battery boxes forward and gas tank reward. The differential could be mounted fairly high and the dedion tube directly underneath. Ground clearance would be an issue. How large diameter is the volvo tube? Are there swing axles readily available and adaptable with the sliding splines?
If you could use the leaf/mono springs to do most of the motion control the big bugaboo of irs - weight penalty - could be reduced or eliminated.
|The De-dion was like a VW swing axle right?|
Not really a suspension update considering
The IRS leaf spring combo that you referred
to is similar to the Corvette before they
went to coil-over's in the rear. The leaf
spring was mounted on the differential and
the ends of the spring were mounted to the
lower control arms of each rear wheel.
The leaf spring was a composite mono-leaf
to keep un-sprung weight at a minimum.
I don't know if you had more un-sprung
weight using the composite leaf spring or
IF you don't plan on pushing more than
400hp, perhaps look into a 2nd or 3rd Gen
RX-7, if you have a boneyard around. The
Jag is heavier and I think it's a bit wider.
(The RX-7 IRS is mounted to a lightweight
subframe that can be modified to fit,
though you do have coil-overs, the disc brakes are also a plus)
|.....the De Dion was like a VW swing axle right...... er no- I don't think so- otherwise it would not be found under cars like Aston Martins,Alfa Romeos,Lister Jaguar etc. A swing axle is one where the axle shaft has no articulation at the wheel hub and hinges(swings) about a joint at the body mounted differential. This causes all sorts of problems-excessive camber change and jacking caused by the roll centre being somewhere over the top of the differential.|
A De Dion axle is usually formed by a tubular member sitting behind the body mounted differential with wheel hubs mounted at either end-it is just like a live axle without the diff and can be mounted in all the same ways-the classic installation usually has four trailing links with either a Panhard rod or Watts linkage for side ways location. The drive shafts have to be jointed at both ends and provision normally has to be made for plunge. Where the confusion over fixed length drive shafts may come from is by looking at the De dion under the Rover P6-the early versions had the De Dion member with a telescopic joint to allow sideways location by fixed length drive shafts.
I would argue that most modern cars do not have fixed length drive shafts-these are normally only used on swing axles and older fashioned designs of IRS where they form one of the suspension links -eg Jaguar, Corvette,early Lotus designs-eg Elite and early race car suspesnion. The current popularity of front wheel drive now means that there a lot of excellent CV and tripodal joints which act as joints and also accept plunge eliminating the need for splined joints as per TR6/T2000.
I am not suggesting using a tranverse leaf spring as per the Corvette.I am suggesting that it should be possible to mount a De Dion tube behind the current axle line on the existing leaf springs. The body mounted differential would be the biggest hurdle to overcome-but as the diff would not have to take any suspension link loads it could be mounted in rubber and its position would not have to be very accurate.
The Volvo 340/360 is the only modern car that I know that uses a De Dion axle located by leaf springs sitting behind a transaxle.The use/adaption of this De Dion assembly would take out a lot of the engineering work normally need to make the assembly.
On my way down to the Spares Day at Sandown Park today I was following a new Japanese off roader (Honda CRV?) whiich appeared to have a coil sprung De Dion tube.
|If anyone is interested, the suspension setup that Andrew refers to can be found at:|
This is more what I had in mind...keeping the live axle setup but going to trailing arms for location. What I had envisioned was a slightly different 4-bar setup or a 2-bar setup with a parallel A-arm (which would serve dual purpose of lateral location and a third parallel link. I haven't worked out the details yet, so I'm not sure which would be better. I do like the design of the one in the link above, though. Keep in mind that it is an MGRV8 and not an MGB. I don't know if they use a different axle or not. Going this kind of route would be a lot less work and cheaper (I think at least) than going to a fully IRS (jaguar, sierra/xr4ti, etc), but more complicated than switching over to composite springs and a panhard rod or watts linkage. This is definitely a case where you get what you pay for (or work for) in that modifying the existing leaf spring setup is good, going to trailing arms is better, and going to a fully irs is best. :-)
|I'm with you John,|
I really like the idea of the De Dion setup, but I don't have the workshop at the moment to do the necessary. There are big advantages with the De Dion. All the torque reactions (acceleration/braking) are via the diff not through the springs hence no spring windup. With fixed length halfshafts you also get transverse location so no need for a panhard rod or A-bracket. The diff being mounted to the chassis reduces the sprung weight so you can get better wheel control. If you used the Rover P6 setup you'd get inboard mounted disc brakes for further reduced sprung weight and this is a setup that was designed to take the torque of a Rover V8 (I don't know the ratio though) My ideal would be a P6 rear axle using the std leaf springs and hence (almost) the standard suspension geometry. Problems would be...
Getting the axle narrowed (half shafts and tube shortened)
Getting a custom fuel tank made so that there is space behind the diff for the De dion tube.
Adapting the hubs to the MG stud pattern.
Possible brake balance issues because the P6 is an appreciably heavier car than the B
Overall I think the De dion is a better solution than independent under an MGB because with independent the hub carriers will need to be a minimum of 6-8" tall which will restrict maximum wheel travel. So you'd end up having to use V stiff spring rates and hard damper settings to stop the car bottoming out all the time.
Interested in your rumours about the factory trying a De Dion John, presumably they would have gone the parts bin route with the P6 setup too (or was this before Rover and MG were in the same company) any more detail on how they did it?
(I keep trying to talk myself into doing this hence the v long post)
Excuse my ignorance, but how can you have fixed length half-shafts on a de Dion set-up?
The P6 setup had a telescopic joint in the De dion tube. This gets around the problem of the half shafts binding as they transmit torque loads and means that you can get lateral location via the half shafts
I'm using SD1 rear axle and have just found out the halfshafts have twisted. The following may be useful if you are thinking of using a Rover rear axle. Both A1 Fabrications and Norman Burton who used to carry out this sort of work are No longer trading. I have a contact if you wish to cut and respline and change to MGB Stud pattern. Quaife can also produce a custom made halfshaft for a shed load of money. The option I'm looking at is a custom made halfshaft fitting a SD1 axel but using a MGB drive flange.
Check out my setup on my midget. It uses the type of 4-link you are decsribing. I belive that it would fit easily under a B and work well. The suspension locates the rear under heavy cornering loads accutatly and does not wind up during drag race starts. My roll center ended up being about 4.5" above the ground on this set up. The coil overs come up through the rear deck and attach to the roll cage behind the seat (you should also have a cage if you are racing).
That's what I had in mind for my project, though I'm not sure if I want to do all parallel links or not. I have to take a good long look at the underside, and do lots of drawings and stuff. If I remember correctly, the Turners I've looked at had a similar setup to your midget, but with a panhard rod also.
As an aside, has anyone used (or has anyone ever seen/heard of) Ford Mustang II front suspension for a conversion?
Thanks for the info!
With this set up, the two lower links that angle in from the existing leaf spring mounts, to
the differential locate the axle and prevent it from moving side to side. The upper two
links run at a slight angle, wider at the axle and narrower at the chassis.
This suspension does not use or need a panhard rod. The reason I chose this design was
to eliminate panhard rods or watts links. Panhard rods make the suspension move
through an arc as the suspension responds to bump and rebound, where as the more
complicated and heavier watts link keep everything lined up. This 4-link is much lighter
than a 4-link plus watts link, and easier to make. Panhard rods can also add unnecessary
weight to the unsprung axle and also to the chassis due to the abundant bracing required
to withstand all cornering forces focused on one area of the chassis.
4-links plus panhard rod/watts link can be made to work in many cases, I just like to use
the Colin Chapman approach and use as few links and parts as necessary - but error on
the conservative side (larger rod ends, 2 lower rod ends instead of 1, etc...).
Hope this helps, and good luck.
PS: check out HP Books, "How to Make Your Car Handle" for good tips, and suspension
theory if you have not already done so.
|Joe P. Yes, I've driven an MGB with the Mustang II front suspension and Rover V-8. Barry Preston, up in Kitchener, Ontario, markets a kit to convert the "B" crossmember to attach the Mustang pieces. The car I drove was his fiberglass rebody of the "B" called the Brooklands. I was very impressed with the solid feel and lack of lean, though I should tell you that I only drove it in the rain and didn't really have a chance to put it through its paces. The Mustang pieces will increase the track width by at least 5 inches, making it not suitable for a stock bodied car. I thought about doing it, but, instead am waiting for a friend of mine to complete his MGB suspension redesign.|
|re: Mustang II suspension|
I assume that the subframe could be cut and narrowed to fit on the B, right? If so, the parts would be pretty cheap, and there's a good parts/support range for it (here at least)...
|Joe: What Barry's kit does is allow you to use the MGB crossmember with only the addition of welding on some metal brackets onto which you mount the Mustang upper and lower arms. It is the length of the Mustang arms that increases the track. Keep in mind that from what I've seen the Mustand II suspension comes in at least two flavors. The stock flavor has a narrow lower arm with a single inboard mounting point. The "A" is formed by a trailing arm, which must be mounted to a frame or body point. This is the system Barry adapted. You could use the true lower "A" arm that I've seen in the magazines, but I'm not sure if his kit will accomodate them. You are right about the Mustang pieces being plentiful. Unless you plan on Sebring flares, you'd have to consider narrowing the crossmember or the "A" arm pieces. FYI, Barry even had to use front wheel drive wheels to get the tires inside his flared fiberglass body. His body flares seemed about the same increase in width as the Sebring would give. You might find his sight by doing a search on "Brooklands".|
|Thanks, Bob. After I posted, I realized that they utilized a modified B subframe and not the one from the Mustang II. Unfortunately, you noticed my blunder! :-)|
Yeah, I've looked at the Brooklands website, which is what got me interested in the Mustang II suspension. It may still be viable for me to go with it though (with further research, of course) since I want to flare the fenders on my GT. I don't want the flares to be TOO big, however...they're supposed to be a functional accent, not a bulbous deformity. I wouldn't do anything larger than the sebring flares, and those are pretty big.
|Check out Chris Alston's Chassisworks. They have a crossmember that is available with a hub width as small as 52". Looks like it might could be made to work.|
This thread was discussed between 15/11/2000 and 06/12/2000
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.