bought a nrg for my brother But the brakes are terrible/Dangerous (levers hardly move) front brake actually comes on after riding it for a while (then front wheel wont move again until brake disc cooled down) basically back and front brake are useless is this a simple bleed or do the master cylinders need rebuilding? ps only ridden ped 's with rear drum brakes before and they work great skid etc should a rear dick brake work as good and even skid etc? (thats how i want it to be)
brakes binding is likely to be the pistons in the calipers not returning due to crud build up behind the seals. It'll need the pistons taking out, the seals carefully removing and their grooves cleaning out...clean the piston surfaces up too so theres no crud or marks (WD40 and some fine wire wool is spot on for this). Then the seals need to be replaced if they are damaged whilst taking out or in poor condition, lubed with some red rubber grease and the whole lot reassembled and bled. Pistons go in easy with finger pressure if they're inserted square into their housings and if alls good should be able to be pushed back by finger pressure alone when done. As for grip...SOME back brakes will lock OK with discs....some wont. This is one of the issues I too currently have with the EXUP. It USED to lock up easy but now wont since installing and bedding in new pads. I'll sort it when I get 5 mins and can be bothered.
so do i need to take the banjo off of the caliper cause in my head ill do it like this take out pads take caliper off of forks leave banjo on (otherwise will need to buy copper crush washers again) pump brakes slowly to get pistons nearly all the way out then split caliper clean up and reinstall then bleed? and is red rubber grease needed? (couldnt i just clean piston then spray silicone oil on and install) is this correct?
ideally you need to pump the pistons all the way out to be able to remove the seals, and clean behind them to remove the crud build up in the grooves they sit in. Once the grooves are spotless, it'll allow the seals to bit back as far as they're designed to do which releases the pressure on the sides of the cleaned refitted pistons as for the copper washer, warm it up til its a dull red and let it cool naturally...good as new to use again
dnt think i have a blow torch reuse banjo washers wow lol seriously that works? what you heat them up with might just bang them on the cooker lol
as long as the copper is not too squashed then even heat to dull red and let it cool. The copper softenes ready for reuse
4got to say i did this all no problem ages ago, BUT the pistons were still hard as hell to get back in the caliper could it be cause i soaked the seals in silicone spray? (thought would be good for the rubber) maybe i was wrong anyway all cleaned up n put back piston went back in 1 not to hard the other was hard as hell but i ended up ripping a bit the seal anyway i have common sense and knew how to do it in the first place (just didnt know i could reuse crush washers) thank for that tip ma8 ive just got a prob or soaking anything rubber in silicon oil (think its time to stop that lol)
If the piston is still tight its probably crap behind the seal. Make a tool from an old screwdriver or use one of them curved dentist prods that you get from ebay to clean the groove before refitting new seals with brake fluid. The grooves in the calipers have to be spotless. I stripped a caliper on the RG125 that i'm restoring at present. The caliper was seized solid...even 150psi from the compressor wouldnt move a single piston. I ended up clamping 3 of them and used a full system to push 1 piston to almost out at a time and then repeated on the other 3 in turn. Once the pistons were out, grooves spotlessly cleaned, new seals in, the pistons could be pushed back in freely with finger pressure. They now move as they should and back off the disc when the levers released Heres the crap from BEHIND the seals in the grooves the state of the rear of the seal itself the tool for cleaning out the groove the cleaned up groove how it should look (the dark areas are smooth but stained from corrosion)
yup i done all this dude i just use a lil percision flat head to clean the grooves and get out the seals my mistake was soaking the seals in silicone (trying to make them last longer) but not thinking that it makes them expand but other than that im pretty good at takoing things apart and seeing what to do i used a foot pump to get out my pistons worked great and mine also looked very clean like yours after finished just made the mistake of soaking in silicone i want use silicone spray on caliper seals again but will use it on things were swelling doesnt matter as the silicone makes the rubber last longer
