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MG MGB GT V8 Factory Originals Technical - Traction/anti-tramp bar question
|My v8 needs a traction/anti-tramp bar. I assume this is a pretty simple piece of engineering, but if there are any pictures of what anyone has done online, please point out the URLs. |
I still run an MG rear end (3.07). Would the anti-tramp bar sold by Moss be strong enough for a hopped-up V8? That would be the easiest solution. I don't really want to take the diff off and weld a fitting on there if a bolt-on unit will work just as well.
|I fitted the Moss Anti-tramp bar kits to my 75 Roadster conversion last month. Simple to fit but I reckon the front mountings could do with beefing up a little - they bolt up through the floor and if the a-t bars stop rear axle steering like they're supposed to, they could rip holes in the floor just in front of the spring hangers! Plus the ride becomes extremely firm, even with adjustable rear shockers on the softest setting. Not sure of the benefits just yet! Are you sure you need them?|
|Interesting. I don't see why the ride would become any more or less firm. Gotta think about that. I got a copy of an old V-8 newsletter where they discuss this matter and I see that the way a bunch of people have done this is to weld a front fitting onto/around/near the front spring hanger, where the metal is _really_ beefy, and then bolt a rear fitting to the assembly that bolts the spring to the diff. Seems like a plan. |
You must be right, if the Moss kit simply bolts through the floor there is no freakin' way it will hold up to a V8's output. Just another crappy Moss product, I guess.
Also, it occurs to me: wouldn't a pair of traction bars be much more useful than just having one on one side?
|Ned, you are right. Traction bars come in pairs.|
Moss motors traction bars were design for 4 cylinder engines.
|Ned, I have these pictures of a friend's car on the net, I hope they're of some use to you.|
The ride becomes more firm because the traction bars bind the action of the rear springs. As the body moves down, notice that the rear shackles move rearward. So does the rear axle, because the front spring mount is fixed. When you attach the traction bar, you prevent the rearward movement of the axle.
|am currently fabricating "top hats" for my front spring hangers aka those put on the RV8 by factory..they should beef up the undercarriage..also provide a place to bolt the anti-tramp bars...check out my site (www.theAutoist.com) on the garage page|
Thanks; it looks like Mr. Bourke has fitted rubber bushes to allow some degree of fore-aft movement of the axle (thanks for clarifying that, Mark, it certainly becomes obvious when you say it). This all seems so doggone overengineered ... I wish it were a bit cheaper to fit one of the T. Taylor IRS units, and forget about traction bars, panhard rods, and all that sorta stuff!
|No matter which traction or 'anti-tramp' bar you use it should be the same length as the spring measured from the center bolt to the center of the front bushing. This measurment is taken along the arch of the spring and not 'straight line'. If the bar and the spring are of equal length then there should be no bind on the suspension and no degredation of the ride. Using rubber bushings will allow for some misalignment and rotational movement when the suspension compresses on one side more than the other.|
|Maybe I am missing something. However, it seems as though the factory anti-sway bar not only reduces sway, it also prevents rotation of the axle. If so, why are traction bars necessary. Bill, it seems to me that any bar that is rigidly fixed (even with rubber bushings) to the axle and to the body is going to prevent the fore-aft movement of the axle when the springs function and thereby bind the axle. Thoughts?|
Anti-roll bars seldom do anything to prevent axle rotation, they just try to force both ends of the axle to assume the same attitude. Some on this list have removed their rear anti-roll bars and have been pleased with the results, more even tire contact under cornering. Anti-tramp bars are more useful for linear acceleration and don't bind too much in this application, but can bind during cornering because the axle cannot rotate evenly when one side of the car is lower than the other. All the things we do to improve live axle contol are compromises.
|Great thread! I have Towery tork arms on my car and they seem to be working well. The rear springs seem like they are working properly and the car has a comfortable ride. I have Spax rear shocksand a Hopkinson rear sway bar. Overall, the car performs well for my needs.|
|Axle tramp or wheel hop is caused when the spring begins to bend in the reverse of it's normal position when the rear axle housing trys to rotate. Because the axle is usually mounted above or below the centerline of the spring there is additional leverage placed on the spring. An anti-tramp bar moves in parallel to the spring under normal conditions so does not cause any bind on movement, but since it is rigid and won't bend it prevents the axle rotation and spring bending.|
For a good street suspension the anti-tramp bars should be the same length as the front half of the spring and mounted parallel to the line between the front spring bushing center and the spring center bolt at the main leaf. Rubber bushings will help soften the ride yet not allow enough axle rotation to be a problem. There is fore and aft movement of the axle when the springs compress, but remember that this movement is through an arc, not strictly linear. A rigid bar mounted parallel will travel through the same arc and thus not affect the fore and aft movement.
Hope this clairifies things.
Anti-tramp bars are usually located below the spring and offer more leverage than the spring because of their increased distance from axle centerline. Picture a rectangle with one end the front spring eye and the front of the bar; the other end the spring center bolt and the aft pivot of the bar. When the wheel is forced up as the car squats, the upper link (the spring) becomes longer than the bar; therefor, you no longer have a rectangle, but a trapezoid which rotates the axle and forces the pinion shaft toward the prop shaft. Now let's go to the other side and lift the body as happens on the inner wheel in a turn. The upper link (the spring again) becomes shorter than the bar, creating a trapezoid of opposite dimensions to the first case. The axle will rotate and the pinion shaft will will be forced toward the ground. When these two forces combine when one corners, how could you not have tremendous tortional strain and the appearance of spring bind?
This thread was discussed between 22/06/2000 and 30/06/2000
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