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What is the "expert" opinion on a Watts link for the rear instead of a panhard bar?

it seems to work well for the Bowler, although it does seem to have somewhat limited suspension travel compared to a usual baja vehicle or crawler

Obviously more parts to wear but it does keep the axle centered
 

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Only the B500. The B1000 is in Nov. which is cutting it close to race the same vehicle in Dakar in Jan.
I talked to Mark the other day and he said VW is building him a Rig for the 1000. He and the racing engineers from Germany came and watched me at rockraces in Cortez. They thought it was very cool. Mark is always thinking about advantage.


Great thread.









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so i've been reading this thread and any others i can find to try and learn as much as possible so that i can make my rig work better for Xrra racing. This last season was my first, and i built my truck with little to no knowledge of suspension geometry. Now that i have a little experience, and the truck is running, i feel my next step is to try and fine tune the suspension. So, i'm gonna try and explain anti-squat in my terminology to see if i am correct, so that i can better plan my upgrades.

A high AS% will lift your body in turn planting your tires under acceleration. This also means that the rear suspension will resist compression during rough sections, which in turn will translate to a rough ride. I have a single link rear, which i am told usually nets a high AS. One of my biggest complaints about my rig is how rough the ride is, even if the course seems somewhat smooth. I haven't ran the #'s yet, but i assume the single link is at fault.


On the flipside, a low AS will get your rig to squat, which in a sense "lifts" downward pressure off of your tire, causing you to lose traction easier. The plus side to this is that rough sections will feel a lot smoother.

So, of course the trick is to try and find a happy medium for your truck's particular characteristics for the given terrain you plan to travel. If this sounds off, please fill me in where i am wrong. I realize there is no exact right or wrong, but fully understanding it will help in my decision making.

Also, i was curious on the thought process for limiting straps. I set my rig up with short straps towards the center(when viewed from the rear). When articulating, the setup works well, but at ride height, the straps are only like 1-2" from full expansion. Now, i have noticed that a lot of race rigs run long straps alongside the shocks. My impressions are that when my rig leaves the ground on a table top jump or rough section, that the rear axle is left with some shock preload. Since the shock can't fully unload, it seems like that momentum would be carried to the front end and force the front to drop sooner than normal. Does this make sense, or am i reading too much into it?

I am gonna go back now and try to understand the other portions of this thread, and try to post up my impressions to make sure i am correct. I appreciate any help I can get.

I read back through again, and had a couple of questions if anyone is willing. How do you properly setup a 3 link to "equally load" the tires, i heard mention of a formula for this, but that was it?

Also, i am still unsure of the benefits or drawbacks of a high or low roll center height. Seems like a low one would net more body roll, and a high one less, correct? too high, and it seems like your truck would be rough riding, and too low would get you "squishy" cornering. I may be way off course with this, so please explain more if so. It also seemed like the best roll axis angle would be to anywhere from level to slightly higher in the rear, correct?

Again, i appreciate any info i can get!
 

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A high AS% will lift your body in turn planting your tires under acceleration.
No, not right. High AS% only resists the suspension motion that will occur from weight transfer during acceleration. It cannot net any increase in the 'plant' of your tires. I will now refer to 'plant' as normal force. So the total normal force on your tires is limited to the vehicle's weight plus or minus any vertical accelerations. Ok, great, what does this mean? The misconception stems from the "as the body is accelerating upwards there is a net increase in the normal force on the tire". This is true. Just do the standing on the scale with a weight you raise over your head trick. However, just as that acceleration increases normal force the deceleration as the body slows its upward movement decreases the normal force on the tire. So you do get a peak of higher normal force for a split second, but it's followed by a peak in the other direction. What this means is the 'planting' of the tires is fluctuating and not just simply 'more'. Tire load fluctuation is not a good thing. But yes, AS does create a force during acceleration that will hinder the ability of your suspension to isolate ground inputs and forces from the chassis.

Also, with a net lifting of the chassis there can be an increase in the cg height which will increase some load transfer to the rear wheels during acceleration thus increasing normal load on the rear tires at the expense of the front. This effect is often over rated even though it's possible that it is there. This is a different effect than the forces induced from the suspension linkages due to AS.

On the flipside, a low AS will get your rig to squat, which in a sense "lifts" downward pressure off of your tire, causing you to lose traction easier.
The "lift" off your tire is momentary and the idea will work almost opposite to that of above but for negative AS numbers. With AS between 0 and 100% your rig will squat, but there still be a vertical upwards force on the chassis from the suspension linkages.

I hope this makes a little bit of sense this go round.
 

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makes perfect sense, my wording is pretty sloppy, but the way you explain it is my general thought process.
 

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This is also used to get the truck "unstuck" in case it rests on the top of a dune and allows it to crest it slower and therefore safer (to ultimately finish the race)
 

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No, not right. High AS% only resists the suspension motion that will occur from weight transfer during acceleration. It cannot net any increase in the 'plant' of your tires.
In road and drag racing there is a usage of pinion angle in the drive axle to increase tire "plant". Pointing it downward has a dramatic effect in increasing tire "plant". Offroad suspensions need for ground clearance and U-joint life results in the pinion angles pointing upward presumable decreasing tire "plant". Can suspension geometry be used to offset this effect or is it even desirable to do so in an offroad suspension?
 

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Triaged beat me to my response. Haha, if you can explain to me how to increase grip with pinion angle then I'll tell you how to offset it with suspension geometry.
 

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On certain tracks in the NASCAR circuit they use pinion angle as one of the means of adjusting tire bite off the corners for example. It is a bit controversial in other forms of racing I realize but there are people using it. Of course independant rear suspensions aren't affected by this, but obviously solid rear axles are affected by torque reactions.
I was just curious if anyone was paying any attention to this in the offroad world, I'm not here to prove or disprove anything.
 

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On certain tracks in the NASCAR ...snip
Dude, never quote the brain trust for reference. They are antiquated dipshits running moonshine cars with 50's tech.
 

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Which tracks? Does moving the pinion up increase or decrease tire bite? How do they adjust it? Why would you want less tire bite? What drawbacks are there to getting all this tire bite by adjusting the pinion angle?
 

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In road and drag racing there is a usage of pinion angle in the drive axle to increase tire "plant". Pointing it downward has a dramatic effect in increasing tire "plant". Offroad suspensions need for ground clearance and U-joint life results in the pinion angles pointing upward presumable decreasing tire "plant". Can suspension geometry be used to offset this effect or is it even desirable to do so in an offroad suspension?
Care to prove how pinion angle could have any effect on tire loads?
Triaged beat me to my response. Haha, if you can explain to me how to increase grip with pinion angle then I'll tell you how to offset it with suspension geometry.
On certain tracks in the NASCAR circuit they use pinion angle as one of the means of adjusting tire bite off the corners for example. It is a bit controversial in other forms of racing I realize but there are people using it. Of course independant rear suspensions aren't affected by this, but obviously solid rear axles are affected by torque reactions.
I was just curious if anyone was paying any attention to this in the offroad world, I'm not here to prove or disprove anything.
Which tracks? Does moving the pinion up increase or decrease tire bite? How do they adjust it? Why would you want less tire bite? What drawbacks are there to getting all this tire bite by adjusting the pinion angle?
I tried to warn you...Nascar = monkeys + Football
 

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Which tracks? Does moving the pinion up increase or decrease tire bite? How do they adjust it? Why would you want less tire bite? What drawbacks are there to getting all this tire bite by adjusting the pinion angle?
1. Short tracks-
http://sports.espn.go.com/rpm/news/story?series=2&id=2901145
-go down about halfway to the short track setups section.
2. Moving the pinion up decreases tire bite (according to the "brain trust" :flipoff2:).
3. Shims? It's the truck arm suspension, there are different methods to use. I really don't know what they are using.
4. If you are not familiar with the terms "tight" and "loose" then we need not continue discussing it. They set the cars up to be tight or loose based on differing circumstances and driver preference.
5. There is a loss of horsepower from larger u-joint angles that they would not like for example.

If you aren't taking any of this into account in offroad racing then you should at least be aware of it.
The Sprint Cup guys are one of the few remaining professional racing venues out there that run solid rear axles other than offroad racing so that's why I bring them up. And don't be so sure there isn't a hell of alot of money being spent in R+D there, the payoff for being the winner there is huge.
 

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front #'s

Okay....so ive read throught this thread about 10 times and countless other pages of suspension theory.......my question is do the same theorys apply to the front ???? Do the lower A/S numbers work for the front ?? Sorry if this has been coverd........
 

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Okay....so ive read throught this thread about 10 times and countless other pages of suspension theory.......my question is do the same theorys apply to the front ???? Do the lower A/S numbers work for the front ?? Sorry if this has been coverd........
the front is like the rear when you are driving backwards for the most part... a higher "anti squat" (in the front it's called anti dive) in the front will have the opposite effect and want to compress the suspension from the torque on the axle tube.

Bigger valves or Triaged will most likely straighten me out and go more in depth but that is it on the surface.
 

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the front is like the rear when you are driving backwards for the most part... a higher "anti squat" (in the front it's called anti dive) in the front will have the opposite effect and want to compress the suspension from the torque on the axle tube.

Bigger valves or Triaged will most likely straighten me out and go more in depth but that is it on the surface.
Yea....I get that part of it.........but I guess my main question is do the low A/S numbers that work for crawl'n and haul'n in the rear apply to the front?
If this is completly wrong.....I would love to hear the right answer:D
 
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