Speedshop Posted September 18, 2013 Posted September 18, 2013 The thing that stalled my project SR was the rear wheel. It needed so much work, I changed the rear disc brake from a drum and fitted an ally swingarm. The rear hub from an XT500 was laced in to a 3.5 x 18" inch rim then all the problems started. The sprocket carrier was worn and let the sprocket wobble badly - so badly i couldn't be sure I'd got the wheel spacer right to get the chain running true. Also the Motolana swing arm fouled the drum brake rod not to mention numerous other things that were needed just to get all the new parts to fit. Well after a long break the sprocket carrier was modified according to a German website: Bearing housing machined down New bearing and spacer fitted to sprocket carrier And I found an oil seal that fits with the standard circlip to finish it off: The fix for the brake rod was increase the length of the brake cam operating arm. I did this using the ally operating arm from an XT600. Adding length to the operating arm might change how the brake feels, but I then compared it to the length of the XT500 brake arm which is the same at the XT600 but in steel. So if they used a longer brake arm on the XT500 compared to the SR500 it shouldn't make much difference. We might do this fix as a kit and if we set up a proper machine shop offer this as a repair service (I had to unlaced the hub after having built the wheel up Grrrrr, and with some expert help machined it on a myford)
dt502001 Posted September 23, 2013 Posted September 23, 2013 Sorry to have to ask but,,,,,, if I have read this correct you have converted a disc to drum brake system and if so why? ,or you have made a new sprocket carrier to fit a alloy arm..... after reading it 3 x I'm still lost as to what you have done,I am guessing the latter as the picts show a drum could you please clear this up if for no one else but me.
Moderator drewpy Posted September 23, 2013 Moderator Posted September 23, 2013 cool mod, pain to work out though!
Speedshop Posted September 24, 2013 Author Posted September 24, 2013 Sorry to have to ask but,,,,,, if I have read this correct you have converted a disc to drum brake system and if so why? Because the rear brake does less then 20% of the braking. Its there to stop the back end wagging like a fish tail. Its been done but none of the big manufacturers put a twin leading shoe drum on the back when TLS was the best there was. You don't need massive braking in this position as the rear tyre is being lifted the more the front brake is applied. Your front is THE stopper, just need something to balance it at the other end. I recently bought sintered pads and upgraded the rear disc brake on my Daytona. I soon put bought basic pads in as the rear was too powerful and caused the back to lock up too easily
Speedshop Posted September 24, 2013 Author Posted September 24, 2013 cool mod, pain to work out though! We're doing a kit :-)
dt502001 Posted September 25, 2013 Posted September 25, 2013 All I can say is if your only using your rear brake for 20% your braking doing it all wrong,the front brake is for slowing down quickly the rear is for setting up the pre load on the suspension,so the bike set's it's self even in the conner and dosen't fish tail and if needed you can set a drift up to square a cornner. You sitill ride like the guys in the 80's if you brake with 80% front and HOPE to catch the rear as it set's down after massive braking with the front alone smooth braking say 70-30 set's the bike up better for a cornner just watch the fast guy's in GP and if you want to be fast in SM or ice or flat track. you better learn how to use the rear brake and pitch it in on a slide using a counter steer method,and most street rider's would be using a Sm riding style if they want to be fast on the street. I personaly think your conversion is wrong,i would never trade a disc for the extra weight of a drum,it goes against all principals of rotating weight and quick turning. Not to mention how a drum sucks in the rain/wet conditions. So while you have given people a choice,I would never suggest it to anyone
slice Posted September 25, 2013 Posted September 25, 2013 I like the conversion but am more interested in what DT says about his braking method, I am one of those OLD guys he's talking about and as far as I know if you pull on the front brake the rear lifts, if you brake hard it lifts a lot and if you brake soft it lifts a little, physics 101, so how can you say that using the back brake is better now than back in the day? Don't matter how big or small your back brake is if you only get 20% of your braking from it then it don't matter if it's drum or disc and the weight issue is negligible when you really think about it, a Disc and caliper versus a drum and shoes is (I would think) about the same in weight terms, maybe I'm wrong (ask my wife she thinks I talk out of my arse most of the time!) but I think Speedshops system is neat and tidy looking and some will no doubt find it useful. Just my thoughts on it you understand not saying I'm right just my opinion. P.S if you have ABS does that mean you get to use the rear brake more as it keeps the rear tyre on the road more? Remember I'm an old fart and have never used this stuff, barely understand it really!
Speedshop Posted September 25, 2013 Author Posted September 25, 2013 I ride old 500 singles on the road. And the odd 650 twin. When I feel confident I'm not going to lose my lisence I'll break out the 900 triple. I fully accept that discs are generally better then drums. However the 1970s disc and caliper that I removed weighed in at over 5 kilos and were on or off in the dry and off or maybe on (who knows if or when) in the wet - best replaced with the drum option which is far more controllable and predictable. The drum hub weighs less. Remember this is 1978 equipment. I'm no GP rider either! :-) I just do electronics to suit what the fast guys want from the engine. And I play in the workshop when I'm allowed near a lathe/welder/propane torch/drill press......... I did have a BMW with ABS - I could leave the braking so late I'd lead many rocket rider in to a round about too quick for their comfort. Trouble is it makes you lazy and the system failed one day, also if you are on mud or slippery rocks the ABS can leave you with no brakes at all.
Moderator Cynic Posted September 26, 2013 Moderator Posted September 26, 2013 All I can say is if your only using your rear brake for 20% your braking doing it all wrong,the front brake is for slowing down quickly the rear is for setting up the pre load on the suspension,so the bike set's it's self even in the conner and dosen't fish tail and if needed you can set a drift up to square a cornner. You sitill ride like the guys in the 80's if you brake with 80% front and HOPE to catch the rear as it set's down after massive braking with the front alone smooth braking say 70-30 set's the bike up better for a cornner just watch the fast guy's in GP and if you want to be fast in SM or ice or flat track. you better learn how to use the rear brake and pitch it in on a slide using a counter steer method,and most street rider's would be using a Sm riding style if they want to be fast on the street. I personaly think your conversion is wrong,i would never trade a disc for the extra weight of a drum,it goes against all principals of rotating weight and quick turning. Not to mention how a drum sucks in the rain/wet conditions. So while you have given people a choice,I would never suggest it to anyone Haha..... My TDR back brake gets used during the m.o.t and then.............? er..................? oh maybe if its raining, possibly. ooooh ice. Otherwise nope.
busyeddie Posted September 26, 2013 Posted September 26, 2013 I wondered how long it would be until Jason commented on rear braking....
Moderator Cynic Posted September 27, 2013 Moderator Posted September 27, 2013 What are you suggesting, would you be calling me a cynic, ah.......well. Drum looks pretty and does the job, in 78 it was likely far more reliable than a disk anyhow. My old mans Ho :-D da has a chuffing great twin leading shoe vented drum. It may not be as good as disks by some margin. You cant argue that polished up it looks the nuts. Its really good the first time you use it too. Problem being how close to the first the second time you use it is........
Recommended Posts