feetupfun Posted February 25, 2018 Report Share Posted February 25, 2018 Here is one type of M49 rear hub. I just measured the liner of this one as 144mm OD. Nominal ID is 140mm. I am planning plan to machine this one out to either no grooves or a maximum of 142mm ID with some grooves remaining. There is another type of M49 rear hub fitted to early build M49s that I will post up a photo of later if you think it is helpful. This earlier hub has a liner with the same nominal ID (140mm) but has a much bigger OD (147mm) 1 Quote Link to comment Share on other sites More sharing options...
blueflag Posted February 25, 2018 Author Report Share Posted February 25, 2018 Cheers! I'll be out all day cod fishing so I'll not get into the garage till tomorrow morning, I'm hoping I'll get away with just skimming the drum now....? Quote Link to comment Share on other sites More sharing options...
mrb505 Posted February 25, 2018 Report Share Posted February 25, 2018 7 hours ago, feetupfun said: Here is one type of M49 rear hub. I just measured the liner of this one as 144mm OD. Nominal ID is 140mm. I am planning plan to machine this one out to either no grooves or a maximum of 142mm ID with some grooves remaining. There is another type of M49 rear hub fitted to early build M49s that I will post up a photo of later if you think it is helpful. This earlier hub has a liner with the same nominal ID (140mm) but has a much bigger OD (147mm) That’s interesting David is there much visual difference between the hubs Quote Link to comment Share on other sites More sharing options...
blueflag Posted February 26, 2018 Author Report Share Posted February 26, 2018 Just spoke to in motion, apparently the brake surface was just chromed in the factory. Mine has obviously had a cast iron sleeve fitted in the past and that is almost worn through to the aluminium! Looks like I'm going to have to bore it out and re line the hub, I'll repair the bearing diameter at the same time. It'll keep me off the streets! I'll let you guys know how it goes.... Quote Link to comment Share on other sites More sharing options...
lorenzo Posted February 26, 2018 Report Share Posted February 26, 2018 (edited) As I understand it, if your hub is 2-piece with a removable spoke flange, as in the pics. from feetupfun , then it's the old style "heavyweight" item. This would have an iron brake drum which was actually cast-in as an integral part of the hub, and brake shoe linings 40mm. wide.. Hardchrome lining is a feature of the later one-piece "lightweight" hubs with brake linings 25mm. in width. Remember, blueflag - a picture speaks a thousand words.........? Edited February 26, 2018 by lorenzo Additional info. 1 Quote Link to comment Share on other sites More sharing options...
blueflag Posted February 26, 2018 Author Report Share Posted February 26, 2018 I'll try and post a photo tomorrow, even if it's a cast in liner I need to do something. ? Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 26, 2018 Report Share Posted February 26, 2018 On 25/02/2018 at 6:17 PM, mrb505 said: That’s interesting David is there much visual difference between the hubs Yes the earlier one has a narrower brake drum contact surface, the smaller spoke flange is part of the hub casting and the fins on the drum are machined not cast 1 Quote Link to comment Share on other sites More sharing options...
blueflag Posted February 28, 2018 Author Report Share Posted February 28, 2018 (edited) Been too busy the last couple of days to make any progress, I'm hoping to try and get the hub bored later on. Another question, I know I'll probably get flayed alive for suggesting it but I've found some cast pipe in a scrap bin, it would only need a lick on the o/d and bore to be spot on for size. It's not cast iron, it's a nickel chrome alloy steel, basically stainless. I'm happy to try it out, thoughts guys? (The only cast iron I have is a huge chunk and it seems a waste) Edited February 28, 2018 by blueflag Grammar Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 28, 2018 Report Share Posted February 28, 2018 40 minutes ago, blueflag said: Been too busy the last couple of days to make any progress, I'm hoping to try and get the hub bored later on. Another question, I know I'll probably get flayed alive for suggesting it but I've found some cast pipe in a scrap bin, it would only need a lick on the o/d and bore to be spot on for size. It's not cast iron, it's a nickel chrome alloy steel, basically stainless. I'm happy to try it out, thoughts guys? (The only cast iron I have is a huge chunk and it seems a waste) Some alloy steels have a low coefficient of friction so be careful. Mild steel or cast iron are the go for brake drums Quote Link to comment Share on other sites More sharing options...
blueflag Posted February 28, 2018 Author Report Share Posted February 28, 2018 That was my worry, I won't be doing anything too demanding on the bike but I'd like it to stop! Quote Link to comment Share on other sites More sharing options...
blueflag Posted February 28, 2018 Author Report Share Posted February 28, 2018 (edited) Well, just finished machining the drum, it is indeed a cast - in liner. I've taken it out to the nominal diameter of the aluminium, I'm guessing 144 ish mm. Just got to sleeve the bearing diameter while it's set up and sort out a mild steel sleeve for the drum. Slowly getting there! Edited February 28, 2018 by blueflag Missing photo. 3 Quote Link to comment Share on other sites More sharing options...
bleeper Posted March 6, 2018 Report Share Posted March 6, 2018 Nice! Quote Link to comment Share on other sites More sharing options...
blueflag Posted March 6, 2018 Author Report Share Posted March 6, 2018 Trying to find time to make and fit a new drum. Hopefully it'll be done this week. My mate has suggested going hydraulic on the rear, if I can find a suitable slave cylinder I'll have a bash. If I go ahead in the future I'll make a complete new brake plate to save ruining an original Bultaco part. ? Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted March 6, 2018 Report Share Posted March 6, 2018 6 hours ago, blueflag said: Trying to find time to make and fit a new drum. Hopefully it'll be done this week. My mate has suggested going hydraulic on the rear, if I can find a suitable slave cylinder I'll have a bash. If I go ahead in the future I'll make a complete new brake plate to save ruining an original Bultaco part. ? Best read the trials regs, rod or cable for brake operation in classic classes. Quote Link to comment Share on other sites More sharing options...
blueflag Posted March 6, 2018 Author Report Share Posted March 6, 2018 Oh well, means I've got more time for other stuff! Thanks for the heads up.? Quote Link to comment Share on other sites More sharing options...
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