Join Date: May 2009
Location: Prevezanian Riviera
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Quoted: 1 Post(s)
I would go with a smaller caliper and pads that are made to fit the disk diameter you are using.
The maximum braking force you can use is one that would lock up the wheel even in good dry pavement with the best tires. In your case this may already be too much as the frame may bend.
With the smaller diameter wheel you need pads that have more width/radius than length (side along the circumference). A single piston caliper may work best, maybe one from a dirt bike. If they have enough force to stop a 21" wheel from turning, they have plenty for a 12" wheel.