There was an old post about swapping out the stock brake levers and calipers with mountain bike aftermarkets, but that is gone with the hack. Unless someone can remember the name. MB or something, I forget.
have you tried adjusting the cable slack between calipers and levers? usually there's a lot of slack.
here's what you do: first put your bike on a stand. spin the wheel and then pull the caliper up and notice it takes a while for it to close all the way. so now, loosen the nut holding the cable, and pull more of the cable in and then tighten the nut. now see if the wheel spins freely (sometimes if you pull too much cable, it'll keep the caliper closed). if it spins freely, check to see how well your wheels stop. you'll notice because you changed the slack, it doesn't take too much work to get the caliper closed all the way.
oh well that's normal if you're going pretty quick then braking. the pads won't be able to hold the rotors still since there's so much speed and weight on the bike. unless your rotors have oil on it that'll sometimes cause them to slide.
other than that, basically there's nothing else you can do except replace your rotors or pads then.
I'm not sure how long thes crappy forks would last trying to do stoppies. Have you adjusted the brakes so the levers are stiff?if the levers are stiff and it still won't lock up the rear,I'd try spraying the pads and rotors down with denatured alcohol(break cleaner).I don't think the fronts would be able to lock up period,unless you were real light weight.
i accidentally did a stoppie after adjusting the slack for the front brake. after adjusting the slack, these brakes don't trail.
at first they would squeak, then it went away. now when brakes are applied halfway, the bike stops almost immediately. maybe going downhill at around 20mph (estimate), it'll take about 1.5 car lengths to fully stop. then i tried cruising and then holding the brakes all the way down. i almost flipped over. the stopping power was unbelieveable and it gave me goose bumps.
taht being said, i have a feeling your brake pads are just worn out, or there is still a lot of slack in your lines.
well what i did was spin the wheel and then pull the caliper closed, then once the wheel started slowing down from the caliper closing, let off a little bit, then tighten the cable at that point... that way right when you pull the lever it starts braking immediately and brakes harder.
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