Christofison Posted October 20, 2016 Share Ok so on a recent semi-down hill section on a road I reached a speed of around 65km/h and pulled the breaks....Took me around 30-40m to slow down to around 20km/h which I thought was a bit dangerous, especially if I would need to stop to avoid a collision or avoid something in an emergency (swerving aside)!While pulling the breaks I had that horrible feeling you usually get when dreaming and trying to stop and nothing happens :/. It felt as though I was gong to snap the brake lever off I was pulling so hard!Dude, you need to take them pads out and give them a good scrub with dish washing liquid & clean your discs properly with brake cleaner. Then reevaluate before spending any money. If it's still bad then perhaps the pads have soaked in the contaminant, spray lube or brake fluid. Get new resin pads. Like a few have said before, even weighing 125 with a rubbish brake set on a sticky surface, your rear wheel should lock up even with a moderate amount of finger force. With a bit more force applied to the front, you should get thrown over the bars if your front wheel doesn't wash out. Link to comment Share on other sites More sharing options...
Spoke101 Posted October 20, 2016 Share Some good advice above. But at your weight I wouldn't tempt fate at those speeds. Bite the bullet and invest in a set of these with 203 front and 180 rear rotors, It's a lot cheaper than hospital bills. Link to comment Share on other sites More sharing options...
Mr lee Posted October 20, 2016 Share Thanks for all the replies and advice.The bike is only a few months old and has been taken back for it's first free service to re-adjust derailed cables etc.I did mention to the workshop that the brakes did not feel as great as my old Titan Trail but was told it was the best they could get them after bleeding. I have only done about 160km's in 2 months and find them to be ok at the trails I go on...big red barn, BCC, ebotsie etc.It's just that I was on a road section earlier this week and got going very very fast and when applying both breaks at speed and expected at least the rear to lock up but both just felt very spongy, similar to brake fade in a car when doing laps on a track, which I have also experienced. I suppose I should have brought up that it felt similar to fade.The bike was washed a few days prior to the ride and brakes were applied a few times before the noted fade effect. Anyway I had a look on Shimano's site and they only show the high end stuff...my rotors and all the others inbetween are no where to be found! If a larger rotor would help would it not be cheap enough to change the rear to the same 180mm as I have on the front?Also where can I get brake parts in JHB, that I can physically touch, feel and see befor I buy them?Can I just pop the 160mm rotor off and attach the 180mm? How would I space the rear caliper out to accommodate for the larger disk?Anyone know what I would be in for if I were to upgrade to a set of entry level metal pad compatible disks and what would the part number be? Link to comment Share on other sites More sharing options...
JXV Posted October 20, 2016 Share Thanks for all the replies and advice.The bike is only a few months old and has been taken back for it's first free service to re-adjust derailed cables etc.I did mention to the workshop that the brakes did not feel as great as my old Titan Trail but was told it was the best they could get them after bleeding. I have only done about 160km's in 2 months and find them to be ok at the trails I go on...big red barn, BCC, ebotsie etc.It's just that I was on a road section earlier this week and got going very very fast and when applying both breaks at speed and expected at least the rear to lock up but both just felt very spongy, similar to brake fade in a car when doing laps on a track, which I have also experienced. I suppose I should have brought up that it felt similar to fade.The bike was washed a few days prior to the ride and brakes were applied a few times before the noted fade effect. Anyway I had a look on Shimano's site and they only show the high end stuff...my rotors and all the others inbetween are no where to be found! If a larger rotor would help would it not be cheap enough to change the rear to the same 180mm as I have on the front?Also where can I get brake parts in JHB, that I can physically touch, feel and see befor I buy them?Can I just pop the 160mm rotor off and attach the 180mm? How would I space the rear caliper out to accommodate for the larger disk?Anyone know what I would be in for if I were to upgrade to a set of entry level metal pad compatible disks and what would the part number be?Go to si.shimano.com It is their technical service centre. You can find specs of all currently available parts (specifications link on lower left of page) and you can also find and download service manuals for all parts past and present if you know the series number. Your M506 brakes are current production. You are not limited to Shimano. There are other brands that make good brakes but you get what you pay for. Shimano hydraulic brakes are typically very good across the range. If you levers were spongy and collapsing onto your fingers that indicates air in the system and needs competent bleeding . If the levers were stiff when pulled but just not slowing you down much that indicates contamination on pads. If the calipers are not properly aligned to the discs it can also weaken the performance. Difficult to advise further without riding the bike for myself. Yes you can/should fit a 180 disc at rear if you weigh over 100kg and going such speeds....even better move your front 180 to rear and fit a 203 front. you'll need adapters for both to get the correct caliper spacing. An investment in bigger discs is not wasted even if you later upgrade your calipers and levers. What bike is it? Sent from my SM-G935F using Tapatalk Link to comment Share on other sites More sharing options...
Mr lee Posted October 20, 2016 Share Thank you JXV.Merida ninety six 600 2016 Link to comment Share on other sites More sharing options...
Tony datoy Posted October 20, 2016 Share Fully kitted I'm around 112kgs, my Pyga has RT86 180/203 with M8000 XT brakes, resin pads. I've never had a problem stopping and I've ridden some hectic downhills.T Link to comment Share on other sites More sharing options...
JXV Posted October 20, 2016 Share Thank you JXV.Merida ninety six 600 2016Your 96 is a good quality frame with a decent component spec. Good foundation for an upgrade or two when the original bits wear out. The brakes are the lowest spec item in the groupset considering the rest is good quality Deore/SLX stuff. However I still think a disc upgrade, decent bleed and cleaning out any contamination should improve performance at quite low cost. None of this would be wasted money if you later to decide to upgrade the levers and calipers. Link to comment Share on other sites More sharing options...
Mr lee Posted October 20, 2016 Share Your 96 is a good quality frame with a decent component spec. Good foundation for an upgrade or two when the original bits wear out. The brakes are the lowest spec item in the groupset considering the rest is good quality Deore/SLX stuff. However I still think a disc upgrade, decent bleed and cleaning out any contamination should improve performance at quite low cost. None of this would be wasted money if you later to decide to upgrade the levers and calipers.Ok thanks very much. Any idea on what the part number would be on the lowest spec disk that would handle metal pads? Link to comment Share on other sites More sharing options...
JXV Posted October 20, 2016 Share Ok thanks very much. Any idea on what the part number would be on the lowest spec disk that would handle metal pads?Spec on your bike says it has centre-lock rotors - in which case SM-RT64.If you have 6-bolt hubs then the equivalent is SM-RT66 Both are available in 203mm, 180mm, and 160mm. If you change the front to 203mm you will need a brake adapter to space the caliper out further than your existing 180mm discIf you change the rear to 180mm you will need an adapter there to replace the existing 160mm adapter. The front 180mm adapter is likely not useable at the rear....depends on the frame. These are shimano part numbers. If you have 6-bolt hubs then there are many options for cheaper aftermarket discs but I do not recommend them - Often they they are thinner and consist of more airholes than metal friction surface - so they will heat up faster give less power, which will not help your cause..... Link to comment Share on other sites More sharing options...
gavascone Posted October 20, 2016 Share before going out and spending a fortune on upgrading take your bike in and get the brakes bled as a slight bit of air in the line could cause your brakes to not function correctly start with the basic stuff first and if they are squealing under braking then you would have to replace the pads Link to comment Share on other sites More sharing options...
Dicky DQ Posted October 21, 2016 Share Damn, I have Avids and even they stop me from way high speed on offroad downhills. Remember if you are using more than 2 fingers to brake (Typically just one) something is wrong no matter what the brand. As an aside, I have a no name cheapie set on another bike and I am almost sure that they are better than the high end stuff. So yes, there must be something else wrong. I am 100kg+ most of the time and have never had an issue. Link to comment Share on other sites More sharing options...
Mr lee Posted October 21, 2016 Share Spec on your bike says it has centre-lock rotors - in which case SM-RT64.If you have 6-bolt hubs then the equivalent is SM-RT66 Both are available in 203mm, 180mm, and 160mm. If you change the front to 203mm you will need a brake adapter to space the caliper out further than your existing 180mm discIf you change the rear to 180mm you will need an adapter there to replace the existing 160mm adapter. The front 180mm adapter is likely not useable at the rear....depends on the frame. These are shimano part numbers. If you have 6-bolt hubs then there are many options for cheaper aftermarket discs but I do not recommend them - Often they they are thinner and consist of more airholes than metal friction surface - so they will heat up faster give less power, which will not help your cause.....Thank you! Is center lock the type of hub and is it different to a 6 bolt?The disks on my bike have a hub but the disk is attached to it with rivets and there are 6 of them!I assume that as my disk is on the cheap side of things it is a one piece unit and cannot be changed unless swapped out with a higher spec one piece unit or a hub that will allow the disk to be bolted on! Link to comment Share on other sites More sharing options...
Eugene Brown Posted October 21, 2016 Share Thank you! Is center lock the type of hub and is it different to a 6 bolt?The disks on my bike have a hub but the disk is attached to it with rivets and there are 6 of them!I assume that as my disk is on the cheap side of things it is a one piece unit and cannot be changed unless swapped out with a higher spec one piece unit or a hub that will allow the disk to be bolted on!Sounds like centre lock, but to be safe, just post a photo quickly, preferably with the wheel out of the fork/frame (so that everything is exposed). Link to comment Share on other sites More sharing options...
Mr lee Posted October 21, 2016 Share Ok...how to post photo on here?Hopefully no image hosting site is needed... Link to comment Share on other sites More sharing options...
JXV Posted October 21, 2016 Share Thank you! Is center lock the type of hub and is it different to a 6 bolt?The disks on my bike have a hub but the disk is attached to it with rivets and there are 6 of them!I assume that as my disk is on the cheap side of things it is a one piece unit and cannot be changed unless swapped out with a higher spec one piece unit or a hub that will allow the disk to be bolted on!centre lock discs have a disc riveted to a splined carrier that fits onto splines on the hub. There is a lockring to secure them. 6 bolt hubs can be just a solid steel disc or a disc riveted to a carrier. Either has 6 bolts that attach it to threaded bolt holes in the hub. There are no splines or lockring. Do yourself a favour and look up your bike and the part numbers I gave you on the web. Sent from my SM-G935F using Tapatalk Link to comment Share on other sites More sharing options...
Mr lee Posted October 21, 2016 Share centre lock discs have a disc riveted to a splined carrier that fits onto splines on the hub. There is a lockring to secure them. 6 bolt hubs can be just a solid steel disc or a disc riveted to a carrier. Either has 6 bolts that attach it to threaded bolt holes in the hub. There are no splines or lockring. Do yourself a favour and look up your bike and the part numbers I gave you on the web. Sent from my SM-G935F using TapatalkThank you for clearing that up I did download most of the manuals for most components on my bike but have been away this week and it is all on my laptop...don't like looking at manuals on a small phone. Is there anyway I could get center lock disk that handles metal pads? Do they actually have one that would be a direct replacement without it being a total mission? ...and higher cost! Link to comment Share on other sites More sharing options...
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