http://page2.auctions.yahoo.co.jp/jp/auction/b126201817

Any ideas?

Expensive?

Looks like modded rear axle or sprocket shaft?

It's a rear wheel balancing attachment :)

Yup here is what the listing says:

New attachment for wheel balancer
Product Details

Battle Factory products.

No. BA00 -100 -01
Machined aluminum products 17S. (Anodized titanium finish).
Taper angle of 45 degrees

The inner diameter 20Φ.

Ahhhhhhh so what's that do then?

No idea, but it must be magical as its bloody expensive!

it just bolts through the rear wheel, just like the axle, the 45 degree taper is so it centres the wheel for balancing, probably goes on a specialist wheel balancer :)

BillingCBR wrote:it just bolts through the rear wheel, just like the axle, the 45 degree taper is so it centres the wheel for balancing, probably goes on a specialist wheel balancer :)

http://www.battle.co.jp/syohin/ba00-100/baransu.htm

It's for this wheel balancer.