I am thinking about doing my rear arms on my Alfa Romeo spider,with spherical bearings inserted into the trailing arm to get the rear axle more supple,I am running Polly bushes,and my rear tires will lift in corners too easy, has a freind video it for me, I believe that the spherical bearings inserted the rear arms well lessen this. Your thoughts?
After they are placed into the arms, and located firmly, I can seal each side with a soft rubber bushing to keep them clean.
Are you saying your inside rear tire lifts and you think that adding more movement than is available in a poly or rubber bushing is going to stop that? Where's the next link that will bind?
I don't think that's the solution you're looking for. Try some anti-roll bars instead.
In reply to Dr. Hess :
Alfa Romeo spider run better without sway bar on the rear
,many folks on the Alfa Romeo bb, run there cars without.and a larger one than oem 13mm, just cause oversteer, cars are kind of sensitive to tight rear ends,also we have axle straps from the body to limit axle drop. Can react like a hard swaybar when you get on them,most of not all Alfa Romeo spider the rear shocks are set full soft to keep the rear on the ground.
Going to spherical bearings in the trailing arms will reduce the rear roll stiffness, which will help. Also the rear of the top arm. A larger front anti-roll bar will also have a similar effect. Do one at a time. Personally I would prefer the stiffer front bar, but that is related to preference. Remove the rear anti roll bar first....
In reply to Alfaromeoguy :
Spherical bearings definitely won’t be more supple - they’ll be about as rigid as it gets - but they *may* allow more multi-axis movement, if that’s how the suspension is designed, and if bushings are causing bind. However, if that’s true you may need high-misalignment spherical bearings to both prevent binding and damage to the bearings.
Spherical bearings likely won’t last as long a bushings, but on a dedicated track car it probably won’t be a problem. It really isn’t a solution you want to use on the street though.
In reply to Pete Gossett :if they rotate in the same plan of twist,how can it be more ridged to movement.
In reply to TurnerX19 :
A stiffer front sway bar= more understeer?
In reply to TurnerX19 :
You have a x19? Very cool car, I have seen one here in Sacramento with a 2.2 ecotec engine in the car.very fast.
In reply to Alfaromeoguy :
Kind of but not always. If a stiffer front bar allows the front tires to stay in their happy place in regards to camber it can actually reduce understeer.
I think you're on the right track by softening the rear and making the front stiffer.
Alfaromeoguy said:In reply to Pete Gossett :if they rotate in the same plan of twist,how can it be more ridged to movement.
Both rubber and poly bushings provide some dampening through their elasticity, delrin much less so. Also, because of this suspension components may not always remain concentric in their motions.
Spherical bearings, being metal-on-metal, retains concentricity throughout the range of motion(well, at least until they wear out). However, because they lack elasticity they do not provide any dampening and are thus more rigid.
Don't do it. I have un-did this to two cars this year because the owners could not stand how bad the noise was.
All drivetrain noise will go right to the tub. All road harshness will be transmitted, too.
Nothing wrong with good rubber bushings in this application.
freetors said:In reply to Alfaromeoguy :
Kind of but not always. If a stiffer front bar allows the front tires to stay in their happy place in regards to camber it can actually reduce oversteer.
I'm agreeing with freetors but I think correcting a typo when I note that a bigger front bar can reduce understeer for the reason suggested (i.e. if it prevents the car rolling 'til the fronts are leaning out of the corner, it'll make the tires work enough better to more than offset the fact that it's transferring more load from the inside tire to the outside tire). Preventing excessive body roll will of course also reduce the problem of picking up the inside rear.
In reply to Alfaromeoguy :
Yes, I am daily driving an X1/9 with a slightly warmed over original engine. I have also spent many years working on formula and sports racing cars as well as Alfa Romeos. Ransom's latest post here is exactly why I would go to a stiffer front bar, and Knurled is 100% correct about the noise issue. What some others have overlooked is that the lower arms are twisted in roll, so the spherical does reduce roll stiffness. The front geometry of an Alfa Spider does go into + camber in roll after about .6G. Thus reducing rear roll stiffness will magnify the + camber, while increasing front roll stiffness will help, and also keep the rear wheel down on the pavement.
Ransom said:freetors said:In reply to Alfaromeoguy :
Kind of but not always. If a stiffer front bar allows the front tires to stay in their happy place in regards to camber it can actually reduce oversteer.
I'm agreeing with freetors but I think correcting a typo when I note that a bigger front bar can reduce understeer for the reason suggested (i.e. if it prevents the car rolling 'til the fronts are leaning out of the corner, it'll make the tires work enough better to more than offset the fact that it's transferring more load from the inside tire to the outside tire). Preventing excessive body roll will of course also reduce the problem of picking up the inside rear.
Yes! That's what I meant to say. I have edited my original post for future readers.
In reply to TurnerX19 :
I have dailed out bump steer.
Full rubber boots are not on yet, put order to seals it, last Friday
I think the sphericals will do what you want them to do in this case. I think if the other end of the bar still has some form of bushing, the vibration transmitted into the body should be acceptable, but you'll have to let us know on that one. I can see if both ends were solid that the amount of noise transmitted into the body would be unpleasant. My brain is saying put sphericals in the front and leave bushings in the back, but I can't really explain why.
In reply to Vigo :I also have been thinking about Polly on one side,and spherical on the other end.
If you use something more compliant on the chassis side the NVH will be greatly reduced. The downside is that wear will be accelerated on that more compliant part. A spherical bearing on the wheel side and poly bushing on the chassis side shouldn't be too awful for NVH and the poly bushing will still last a long time, while rubber would be quickly murdered by the rigidity of the spherical bearing.
Spherical bearings on the chassis side are totally terrible. I have just two on my mixed street/track car and they are single-handedly responsible for most of the road noise and suspension maintenance work.
In reply to Alfaromeoguy :
Dialing out the bump steer is a very good thing, but it does not rectify the camber curve. You would have to lower the upper inner pivot point and shorten the upper arms or something more to cure the lack of negative camber gain in roll. Much easier to add roll stiffness!
Because of poly’s lack of deflection, they’re not a great choice for joints that move in multiple axes.
jfryjfry said:Because of poly’s lack of deflection, they’re not a great choice for joints that move in multiple axes.
True, I don't know if that's the case for this particular joint. If you need multi-axis movement, the only good options are a spherical bearing or a Land Rover-style torus-and-hourglass bushing arrangement:
jfryjfry said:Because of poly’s lack of deflection, they’re not a great choice for joints that move in multiple axes.
On the flip side, when working properly, they work much like a bearing on that one axis. They don't have preload or a spring rate like rubber does. If they're moving smoothly, it shouldn't be much different than an actual bearing in terms of resistance to movement. More like a roller bearing than a spherical, but still.
Note all the caveats about moving smoothly and working properly, though! Poly bushings are really good at seizing up.
I have looked into this,and it can be done. To lessen noise I could bolt in a new pick up for the trailing arms to the body, but a .250 × 3 wide x 5 long rubber plate, sort of like a sandwich ,body shell, .250 rubber plate,mounting bracket, of course,grade 10.9 bolts
This would isolate the trailing arm to the body . Lots of cars have a similar set up.
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