5

Can someone please explain the differences between a pullrod and pushrod suspension and provide the pro's and con's of each configuration? Typically these suspensions are used on open wheeled vehicles.

Any visual aids regarding components or function are desirable.

  • 1
    youtube.com/watch?v=pkcWMl9dpcg He explains both and it's very informative. – cloudnyn3 Dec 8 '15 at 9:42
  • Maybe I should just delete the question then. lol. thanks for the link. I've watched a bunch of that kid's video's. Love him. – DucatiKiller Dec 8 '15 at 9:48
  • It's a good question, his visual representation and explanation is better than any amount of typing haha – cloudnyn3 Dec 8 '15 at 9:53
  • 2
    Great question. I'd keep the question and not delete it. While the video link is useful, to my knowledge this question hasn't been asked before. Any answer posted here can reference the video if need be. We want to capture the information here as well and not have to rely on external sources if possible. – Zaid Dec 8 '15 at 10:30
  • 1
    @Paulster2 no problem. Your the answering machine, can't expect you to flow to every question :-) – DucatiKiller Dec 12 '15 at 21:47
4
+100

NOTE: Two sources of information on push/pull rod suspensions used for this answer -

From Formula1-Dictionary.net website with annotations

  • A - Lower Control Arm
  • B - Upper Control Arm
  • C - Pull Rod
  • D - Push Rod

I will first start out by saying the push-rod and pull-rod suspensions are basically the same suspension system, only one is flipped upside down from the other. In both suspensions, there is an upper and lower control arm. Each control arm will have a pivot point towards the inside of the vehicle. This allows for the arms to go up and down at the outside, which allows the wheels/tires/hubs to go up/down as needed. At the outside of the control arms will be ball joints which allows the wheels/tires/hubs to articulate to the left or right allowing the vehicle to turn.

There are also the push or pull rods on each. These are the reasons for the names. The push-rod will be under compression, while the pull-rod will be under tension. These bars are what supports the vehicle on the suspension by transferring the weight to the rocker arms, which are splinted to Torsion bars.

From Formula1-Dictionary.net website with annotations

In the above image, the push rod connects to the rockers. The rockers are splintered to the Torsion bars. This also utilizes the Torsion bar as pivot point for the rockers. The dampers act like shock absorbers, quieting the suspension when subjected to heavy jolts. The antiroll bar linkages provide a means by which to help the vehicle during hard cornering to stay level and stuck to the track. The pull system would be setup pretty much the same way, but upside down of this.

NOTE: In the above image, the antiroll bar linkages would not be attached as shown. If they were, it would never work because the center only acts as a pivot and would break (or be damaged) if both sides were hit at the same time (think of a speed bump). Something would have to give.

You'll notice the design of the pull-rod suspension, the pull rod goes from the bottom of the vehicle to the upper control arm. On the push-rod suspension, the rod is located high in the vehicle and attaches to the lower control arm.

Inherently, the working parts of the pull-rod suspension can be placed lower in the vehicle, which equates to a lower center of gravity. The problem with this is it makes it harder to get to for tuning or if in need of repair. It is also harder to implement in the rear of the car where you have to deal with the transaxle. Because the pull-rod is in tension under normal condition, it can be made thinner than can a push-rod. The trade-off is that the upper control arm needs to be beefed up to support the load, which is now seeing double duty, so it's about a wash between the two as far as weight savings goes.

As for which one works better, the effectiveness of each is about the same. Each has their own drawbacks when considering aerodynamics. Each rod type suffers from both compression and tension, though at different times. What it comes down to is the picking which one works best for the design of the vehicle.

  • 1
    I knew you wouldn't be able to resist. :) btw.....Your the Man! – DucatiKiller Dec 14 '15 at 1:29
  • 1
    @DucatiKiller - I'm sure you'll have some questions for me. I like to answer questions like these because they help me learn about mechanical things. Thanks for the compliment, at any rate. :-) – Pᴀᴜʟsᴛᴇʀ2 Dec 14 '15 at 1:31
  • I feel the same way, fun to learn and share. Yes, I'll probably throw a few of those questions out. – DucatiKiller Dec 14 '15 at 1:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.