Guest Posted October 12, 2009 Posted October 12, 2009 I had loads of work done to my front brake:Master cylinder replaced under warrantyNew padsCalipers cleaned, seals replacedBrakes bledIn fact the brake has been bled several times before now and I think the fluid was also changed. After all this I still get a spongey front brake. One mechanic said one of the disks was warped, but I checked this myself and could not visually detect any warp. The mechanic said he found the warp by spinning the front wheel so I thought I would check for myself but. Also when I "pump" the lever, the feel returns for about a few seconds before going spongey again. I am thinking of getting braided hose but how can I find out that this will work without forking out loads of cash? (again). 1250 bandit s btw. Quote
Guest Posted October 12, 2009 Posted October 12, 2009 say hello in newbies.. if the disc is warped it will push the piston back as the wheel spins, requiring more pressure to return it to the disc.put the bike on the centre stand, and either prop up the front, or get someone to sit on the passenger seat, again lifting the front wheel. spin the wheel and mark it with chalk, where it stops, if it stops in the same place each time, then you have a slight warp.. Quote
Guest philgale Posted October 12, 2009 Posted October 12, 2009 where are you based? someone local may have a disk check thingy....i do anyway also would cuts/holes in the brake lines cause this? meaning new lines might solve the problem Quote
Guest Posted October 12, 2009 Posted October 12, 2009 old lines would as the rubber becomes soft, but an a 1250 bandit, doubt its old enough... and cuts /splits would weep fluid...could just be they've been badly bled by the garage, mine had, they couldn't build up pressure, i have,.. another mod is a larger master cylinder, but as its the 1250, can't think of a bigger one, (usually put a bandit 12 on a bandit6 for stoppy power...) Quote
rollazuki Posted October 12, 2009 Posted October 12, 2009 the disk should be flat(perfectly) sometimes when the disk overheats, it kinda turns into a shallow cone(imagine the rim round the edge of a plate.) when the put the brake on this flexes flat under pad pressure and gives a spongy feel.Get down with a torch, get a mate to apply and front brake on/off, and check for the disk itself flexing in any way. Quote
Colin the Bear Posted October 12, 2009 Posted October 12, 2009 Might just need bleeding. Put a cable tie round the lever and bar. Pull it tight and leave it overnight. The air will perculate up into the master cylinder and out of the lines. Quote
Pete Posted October 12, 2009 Posted October 12, 2009 Might just need bleeding. Put a cable tie round the lever and bar. Pull it tight and leave it overnight. The air will perculate up into the master cylinder and out of the lines. Top tip from Colin - same one he gave me when I had the same problem a long while back! If it works - crisis over. If not...Incidentally is the brake actually spongy (i.e you squeeze and not much happens) or is it more soft? My last bike was the GSX600F and I thought it was spongyness and tried Colin's trick which worked for about 3 squeezes. I checked online to see if anyone else had the same trouble but it turned out the brakes were naturally a bit soft anyway. I left it and it was perfectly fine.Also, if you have adjustable levers make sure you set it to 1 (I think) so it's actuated quickest. And echoing what Frankie said about feedback in the lever if it is a warped disk - the lever will pulse/vibrate. If you get up to about 30 or 40mph and hit the brakes (not quite an emergency stop, nothing quite that violent needed) you'll get the feedback. If there's no feedback in the lever then it's not a warped disk (however if there is a front end wobble then check your tyre pressures ) Quote
Guest Posted October 13, 2009 Posted October 13, 2009 Might just need bleeding. Put a cable tie round the lever and bar. Pull it tight and leave it overnight. The air will perculate up into the master cylinder and out of the lines. Top tip from Colin - same one he gave me when I had the same problem a long while back! If it works - crisis over. If not...Incidentally is the brake actually spongy (i.e you squeeze and not much happens) or is it more soft? My last bike was the GSX600F and I thought it was spongyness and tried Colin's trick which worked for about 3 squeezes. I checked online to see if anyone else had the same trouble but it turned out the brakes were naturally a bit soft anyway. I left it and it was perfectly fine.Also, if you have adjustable levers make sure you set it to 1 (I think) so it's actuated quickest. And echoing what Frankie said about feedback in the lever if it is a warped disk - the lever will pulse/vibrate. If you get up to about 30 or 40mph and hit the brakes (not quite an emergency stop, nothing quite that violent needed) you'll get the feedback. If there's no feedback in the lever then it's not a warped disk (however if there is a front end wobble then check your tyre pressures ) Indeed that is a good tip. I actually did this last night after looking round various forums for spongy bike brakes. Fortunately it actually worked and its much better now. However, will the sponginess return after a while even if there is nothing wrong with the brake system?As for the warped disk, I havent sensed any vibrations from the front lever what so ever. Quote
Pete Posted October 13, 2009 Posted October 13, 2009 No it shouldn't return. If it's nice and firm now and is for a good few squeezes it should stay exactly the same. Over time the position will change slightly due to pad wear, but you won't notice that.If it does change then it's likely that air is getting in somewhere, so you'd need to check that all connections/nuts/bolts are tight (don't snap them off though!) and look for wet patches. Quote
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