jeffgair wrote:
The calipers I am going to use are from a Mazda mx5 (miata)which has 13" wheels so they are relatively compact.
First generation Miata brakes share several parts and overall design with the last generation Gemini brakes. The disks are not the same diameter, but the same vented front and solid rear. There may have been some shared origin of design or supplier. Vehicle weights and power were similar. In the Best Motoring test, they put the Miata against the FWD Gemini along with a pack of other similar 1.6 liter cars. The Miata was in the middle of the pack and the Gemini was pressed against its back bumper at the finish line.
That said, there are a lot of people upgrading the Miata brakes, and a lot of people who should know enough to be equally unhappy with the Isuzu brakes. They are not as bad as Elan brakes, but pretty rubbery and easy to push to fade on the track. The pins on the calipers do not move very smoothly over their life, and the inside pad and rotor are always wearing faster than the outside. And the rear calipers and emergency brake mechanism is a nightmare to get working right.
They aren't as bad as putting your foot out the door and dragging it on the ground, but more of a point to upgrade from, not upgrade to.