Dual Sided Swingarms - Aluminum or Steel

[junior varsity]

Looks pretty cool.  The one in the first picture looks like a regular aluminum swingarm with the underneath bracing added.  The one in the second picture on the 851 looks kind of spindly in comparison. 

Any luck contacting the seller?

None. Sigh.

[COP TZR]

back from the dead.....  Does anyone have any idea of the weight on the AL arm and the steel arm?  Curious to know the weight difference.

[junior varsity]

i believe the steel is lighter, but its flexy.

[atomic410]

also fitment is questionable with some exhaust systems.  I wanted to put an al on my 620 but the aarow high pipes weren't having it

[COP TZR]

i believe the steel is lighter, but its flexy.

lighter...... are you kidding?

[junior varsity]

not at all.   I'm comparing the 17mm axle steel to the 17mm axle aluminum.

The box-shape itself on the aluminum is larger, and the thickness of aluminum is greater than the steel swingarm - hence its additional strength - there is also a lot more going on at the shock pivot on the aluminum swingarm than the steel swingarm.

The box-shape of the steel swingarm is narrower (and uses a slightly shorter axle because of it) and uses very thin walls, and the shock pivot location has lots of "open space" all around it.

[ducpainter]

I'm not taking my bike apart to weigh the aluminum swinger.

[junior varsity]

I remember noting that the aluminum swinger I had to remove from the fixxer-upper M900 (it was damaged) was heavier than the replacement I had, which was steel.  I didn't measure either though.   I suppose I could get a rough measurement on the Alu M900 swinger, since its over at RichD's

[Speeddog]

I've got an late model (ST style) swingarm that I can weigh.

[COP TZR]

is it worthwhile to swap out a steel arm for an alum. one?  Other than the alum. being stiffer & I guess heavier, what are the advantages?

[chris1044]

is it worthwhile to swap out a steel arm for an alum. one?  Other than the alum. being stiffer & I guess heavier, what are the advantages?

No, aluminum will always be LIGHTER than steel.  Always.  Rigidity depends on the types and the component design - I'm not sure, but in this case I would hope it's better than the steel component.

[Raux]

AL is what 1/3 the weight of steel with 1/2 the stength.

so figure to get the same stiffness you get about 2/3 the weight, but if you make it stiffer than... well you get close to the same weight or more.

so no, not always lighter.

[junior varsity]

No, aluminum will always be LIGHTER than steel.  Always.  Rigidity depends on the types and the component design - I'm not sure, but in this case I would hope it's better than the steel component.

Only lighter per unit - like Raux said, it's over sized for the benefits of similar stiffness. It's also the older 851/888 design, where the steel design is sized like the newer big axle swingarms in box shape & thickness.

The steel swingarm flexes easily whereas the Alu version was super stiff. The Alu swingarm also has the big M10 bolt to locate the brake caliper bracket pin (also heavy) compared to the small welded-on pin in te steel swingarm. Advantage there is the Alu swingarms pin is removable for floating caliper setups. Other advantage to the aluminum, besides superior looks, is the built in spools!

Would I "upgrade" to Alu from steel? Yes, but it's a low priority - would rather save up for awhile and have a JMC or Metmachex made to my specs than hope for a good condition used Alu to show up on eBay for a reasonable price

[Dellikose]

The steel swingarm flexes easily whereas the Alu version was super stiff. The Alu swingarm also has the big M10 bolt to locate the brake caliper bracket pin (also heavy) compared to the small welded-on pin in te steel swingarm. Advantage there is the Alu swingarms pin is removable for floating caliper setups.

Sorry to resurrect this, but could someone please post a pic of the bolt through the caliper bracket? I'm reinstalling my aluminum SA and can't remember what it looks like.

[Speeddog]

Do you have the floating rear brake carrier (with the tension rod attaching at the motor) or the fixed rear brake carrier that is restrained by the pin in the swingarm?