J-arm vs. A-arm

[BigWhitey]

It seems like all the long travel trucks I see are running a J-arm top arm up front. Obviously, this gives more room for the motor and whatnot, but are there any trucks that run true A-arms up front? Would that put the motor too far back into the cab to fit the seats and everything else? I'm looking into a truck right now (on paper at this point) and it uses A-arms up front. The suspension design is bada$$, but I'm just trying to get some input as to whether or not there will be enough room...

Thanks for any help.

[SPONSOR]

Membership in the largest desert racing community has its advantages - Participate in Forum Discussions - Send and Receive Private Messages - Maintain Public Photo Albums - Access to Groups - User Profile in our Social Network - Increased Access to more Sub Forums - Reduced Online Advertisements Join our community today

[DUMP!]

It seems like all the long travel trucks I see are running a J-arm top arm up front. Obviously, this gives more room for the motor and whatnot, but are there any trucks that run true A-arms up front? Would that put the motor too far back into the cab to fit the seats and everything else? I'm looking into a truck right now (on paper at this point) and it uses A-arms up front. The suspension design is bada$$, but I'm just trying to get some input as to whether or not there will be enough room...

Thanks for any help.

If your talking about a Trophy Truck style of truck then the "J" arm is the only way to get the wishbone long enough for the desired amount of travel so that the wheel does not go through dramatic camber changes with out pushing the motor way back in the chassis. The only way to build a TT style truck with a traditional "A" arm is if you build it with the motor between the driver/passenger or to build it mid-engine.

By the way your suspension design can still be bada$$ no mater which way you go. "A" arm or "J" arm makes no difference to the suspension geometry of the design only the construction of the arm itself.

Dump

[partybarge_pilot]

Carl Renezeders truck is A-armed. It can be done without to many compromises. Also spreads the load out on the chassis more. J-arms tend to concentrate stress necessitating the need for large structures like bulkheads.

[025]

V-drive can typically run A-arm.

[philofab]

Although the upper a-arm/j-arm sees much less forces than a lower a-arm, it still needs to be quite stout to live. A j-arm puts a lot more push pull forces on the heim/bushing then a a-arm because of leverage. I've seen more than a few j-arms fold/rip out because of improper design. Your upper arm needs to be like 75% of your lower arms length to keep from having to much camber gain, so unless you want a truck that is way to wide you need a j-arm to clear your engine/exhaust. It normally requires you to move the radiator from the front of the engine for clearance so it may not be the best for some applications. You can create the same geometry with either setup.

[BigWhitey]

Thanks for the input. I know the geometry can still be the same with either setup...and both setups can be made to be quite stout...my main question is whether or not you can fit a motor in there running a front engine with A-arms...It sounds like it's doable, but tight.

The only way to build a TT style truck with a traditional "A" arm is if you build it with the motor between the driver/passenger.......

So is it safe to assume that moving the motor between the driver/passenger wouldn't make the truck's main cage too wide to perform well? How wide is the chassis of a typical trophy truck?

[scottm]

There are class 8 trucks with a-arms and stock frame rails, and 20+ inches of good travel - Nick Vaderweys for example. The short upper arm does cause more negative camber in bump, but that is what you want for cornering. I dont care how much travel a vehicle has, if the wheels lean out in corners (as most dez cars/trucks do) the suspension geometry is poor.

[philofab]

It's all give or take... how wide is the motor? How wide is the truck? Radiator front or rear? Does the truck have enough length to move the engine back? How much travel do you need? 18? 24? 28? Although some camber gain is good... to much can be bad. Proper sway bars will decrease the roll to a managable level. You must remember that a uniball/bushing will get less wear if you run longer arms because of less working angle. You also get the added benefit of being able to use a larger bolt through it since you don't need the extra angle misalignments get you.

Remember there is more than one way to do everything and one way is not necessarily better than another.

[DUMP!]

I dont care how much travel a vehicle has, if the wheels lean out in corners (as most dez cars/trucks do) the suspension geometry is poor.

Really Is that absolute, across the board, in any circumstance?? Because I'd be willing to bet at one point or another EVERY vehicle racing today in off road has at some time had the tire go negative in a corner. I'm not trying to start an argument I just think that statement borders on ridicules. Or maybe I'm missing something.

Dump

[PGMazzio]

It seems like all the long travel trucks I see are running a J-arm top arm up front. Obviously, this gives more room for the motor and whatnot, but are there any trucks that run true A-arms up front? Would that put the motor too far back into the cab to fit the seats and everything else? I'm looking into a truck right now (on paper at this point) and it uses A-arms up front. The suspension design is bada$$, but I'm just trying to get some input as to whether or not there will be enough room...

Thanks for any help.

It absolutely works, my brother's TT is A arms. The arms, and truck were made by MCM Motorsports.