Alright guys, Number 5 need input. What makes the A-arm suspension that will be on the Brute Force better that the strut suspensions currently on the Prairie? Don't be afraid to get technical!

 

This is a great question, but I'm not the best person to answer it. Maybe Nyroc or someone else can speak to this one. My impression is that dual a-arms are better b/c as the wheel travels up the suspension (e.g., when you hit a bump), the wheel tilts less from side to side as compared to a single a-arm or MacPh. strut assembly. I think they call this tilting action "camber" but I'm not sure.

For what its worth, below are the minimum turning radius specs for the BF750 and P700.
BF750 = 10.5 feet
P700 = 10.2 feet

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

I'll guess that arms you can custom set settings closer to your driving style.... for struts you have to replace springs with elkas or something. Also I would think double arm would be lighter. I would think the strut would turn sharper but the BF is not as wide either so both could cause a looser turning capabilities. I feel the strut also sinks faster in a downward hole where as the dual arm will eat more of the impact. All sport ATVs are dual arm so that says something too.

 

dual A has less unsprung weight, especially on an ATV. That makes it ride better, and when it is bumped upward, it comes back to ground faster for improved cornering and braking.

If the top arm is shorter than the bottom, The contact patch of the tire on the ground doesn't move as much side to side during a a bump. That also makes better handling and less bump steer. Even if the arms are same length, it is beter than a strut.

The contact patch doesn't move as much while turning, makes steering easier. The geometry doesn't cause as much lift or drop while steering, that makes it a whole lot easier to steer.

I am not so sure I care about whether my car has struts very much. I need dual a-arms off road more than I need it on road.

Custom, are you ready to make the mod? If I produce some mechanical drawings, can you make stuff to spec?

I am thining we will just mod the stock steering kuckles unless someone has a better idea (a little cutting and welding and machining). We will make the arms and brackets. We may use the same ball joint as stock or use a griz one (someone needs to do a little footwork here). The top arm has to suspend the weight, I think, since the lower ball joint is upside down we can't use that. We will leave the steering and brakes and axles like they are. We will mod the frame where the struts mount to fit the shock, and mod the frame for two more brackets to hold the upper arm.

Maybe KOD can get me some quality time with his griz or cat buddies so I can get some steering gemoetry hints from those quads.

 

This is as technical as it needs to get in my opinion: struts suck and A-Arms rule. I went and rode what I hope is soon to be my future 650 Prairie today and the first mod going on is Progressive Front Springs. Struts are just way too soft and spongy.

 

I don't know which is better, but I know I like how A-arms look more so than I do struts.

 

ARMS are better/stronger/adjustable/handle better - they aren't revolutionary by any means. Struts are the new thing in the industry becuase of POLARIS and they are CHEAP!!! Struts are junk when it comes to off road anything.

With strust on a typical ball joint construction you have 3 points of contact to the frame. 2 lower control arm one at upper strut mount. The lower keeps the structure from moving front to back with two points. The inword force durring turning is handled by these 2 points as well. The strut acts as a structural member of the suspension - so it does ALOT. The only way to adjust strut type suspension (camber/caster) is to adjust the angle of the strut itself. Now for the biggest disadvantage, angle of camber under load or zero load. When zero load (tires off ground) the wheels sag (bottom points in and the top pointed out.) under load is the oposite - ever see a front wheel drive car with a heavy load in the trunk - the wheels are all pointed up into the body and the bottoms are hanging out. The worst part about struts is they are easy to break/damage/don't last long. If POLARIS had never made a quad with struts, the other industries would have never done it either. They are junk compared to ARMS. GOOD things, lighter/cheaper/simple

Arms,
Well for starters they have 5 points of contact including the shock. The suspension forces are transfered over 4 points at the end of each arm. SO you allready have twice the structural integrity. I won't ramble that much on A Arms, becuase it is quite obvious how they are better if you put the two kinds side-by-side. Arms don't sag the wheel, and you can FINE TUNE the suspension for better handling.

 

Custom, I got your PM, but I have concerns that I wanted everyone to hear.

1. As far as I know, the center of pivot need to go through the middle of the tire contact patch. The reason our 650 strut steering sucks so much is that the pivot centerline is at a heavy anlge. This, we all know and can see. However, if we were to replace the strut with another arm and a shock, we would have to put the upper ball in the right location so that the pivot centerline went through the contact patch. Due to the current position of the bottom ball joint, that centerline angle would at the same crappy angle as it is now with struts. We would only gain minimal advantage with the change to a-arms.

2. We could wait till the BF is out and use all BF parts (including the front wheels). That might work well. But, we run the risk of not being able to get the front axles to work with the BF spindle.

3. We could lengthen the lower a-arm and move the ball joint closer to the centerline of the wheel. That would make this project a real toughy.

I would be tempted to just trade for a BF, or even buy the BF and keep my 650 and use it as a way to get other people to buy an ATV by inviting them.

 

Can anyone see a good way to mount the top arm to the frame in this P650/700 dual a-arm conversion project?

I can see a great spot on the fram for a rear mount but the front mount would be right about where the radiator is. Anyone got ideas?

C'mon, help me out with some ideas. All we need is trx450 to machine some knuckles and customfab to make the arms and we are all set. We will borros parts for other machines, weld brackets on our frames and then we will have superior handling.