Battered636 Posted April 4, 2012 Report Share Posted April 4, 2012 I'm getting an AP mini caliper and have also been looking at titanium rear disc's on some american site. They are pretty expensive though so I was wondering, since I never ride in the wet anymore and never touch the rear brake on the road or the track, would it be a really bad idea to get a dummy disc made up out of aluminium? It's very tempting to save all that unsprung rotational mass but I've never seen it done before and I know nowt about the various properties of metal so any advice on something potentially dangerous will be gratefully accepted and heeded! Link to comment Share on other sites More sharing options...
RonniB Posted April 4, 2012 Report Share Posted April 4, 2012 I have used a durbahn alloy rear disc on my NC racebike, it's really a "use once and discard" but I never ever uses the rear.. Link to comment Share on other sites More sharing options...
blur1 Posted April 4, 2012 Report Share Posted April 4, 2012 it always amazes me how people don't use their rear brakes..... why? it's a tool that when used correctly enhances riding skill. infact a multiple australian superbike winner here (shawn giles) goes through a set of rear brake pads per race meeting. Link to comment Share on other sites More sharing options...
RonniB Posted April 4, 2012 Report Share Posted April 4, 2012 Its a tool that requires riding skill to be used correctly, there you have my reason for not using it... Link to comment Share on other sites More sharing options...
heds954 Posted April 4, 2012 Report Share Posted April 4, 2012 it always amazes me how people don't use their rear brakes..... why? Not just me then. I couldn't ride without one. In fact I know I can't ride without one. Probably a habit I picked up from riding strokers with shagged suspension. Link to comment Share on other sites More sharing options...
Hendo Posted April 4, 2012 Report Share Posted April 4, 2012 Me too. Going into a bend too hot? Drag the rear brake a bit... Need to tighten your cornering line? Drag the rear brake a bit etc etc Link to comment Share on other sites More sharing options...
Adam Posted April 4, 2012 Report Share Posted April 4, 2012 About to flip it while attempting a minging wheelie.... Link to comment Share on other sites More sharing options...
Battered636 Posted April 4, 2012 Author Report Share Posted April 4, 2012 I can't even imagine using the rear to tighten my line! Applying useful lever pressure at big lean angles must take years of practice and it's probably too late for me to learn new tricks. But didn't Foggy once say something like, 'If they're using both brakes and I'm only using one, does that make me twice as good as them?' lol. Link to comment Share on other sites More sharing options...
wavydavy Posted April 4, 2012 Report Share Posted April 4, 2012 I'm getting an AP mini caliper and have also been looking at titanium rear disc's on some american site. They are pretty expensive though so I was wondering, since I never ride in the wet anymore and never touch the rear brake on the road or the track, would it be a really bad idea to get a dummy disc made up out of aluminium? It's very tempting to save all that unsprung rotational mass but I've never seen it done before and I know nowt about the various properties of metal so any advice on something potentially dangerous will be gratefully accepted and heeded! Simplifying the maths a bit - if your rear disc has a diameter of 220mm, with a hole on 120mm (thus giving a spinning disc of 100mm depth with an outside diamater of 220mm) and a thickness of 6mm it have a volume of 0.000162m3. Stainless steel is roughly 7930kg m-3 , titanium is 4500kg m-3 and aluminium is 2700kg m-3 . So the mass of the stainless disc is 1.28kg, titanium is 0.73kg, aluminium is 0.44kg. If you're never going to use it (which you won't be able to) then using aluminium to make a 'fake' disc will save you about 800g. I'm guessing that the rear disc doesn't have a depth of 100mm, though, so the difference will actually be less, maybe as little as 400g. Going for a massive dump before you go on track and/or using lighter knee sliders will save double that. Or just leave the last 2 litres of fuel out of the tank unless you really really are going to run dry if you don't brim the bike...... Its got to be safer than not having a brake or, worse, having something on there that could cause problems if it touches a pad or the redundant piston and becomes overheated (aluminium melting point is about 660oC - stainless steel is about 1500oC and titanium is nearly 1700oC... ) Link to comment Share on other sites More sharing options...
Mark/Foggy Posted April 4, 2012 Report Share Posted April 4, 2012 The jokers in the BSB 125 GP class have a habit of running mountain bike alloy dics and micro calpiers through scrutineering as a matter of habit. Don't know if they've been stopped from doing this yet, but look at the safety implications. Regulations state in all classes that a rear brake must be present for a reason. If the front fails, how are you supposed to stop. Think of the kittens. Link to comment Share on other sites More sharing options...
cuban pete Posted April 4, 2012 Report Share Posted April 4, 2012 it always amazes me how people don't use their rear brakes..... why? it's a tool that when used correctly enhances riding skill. infact a multiple australian superbike winner here (shawn giles) goes through a set of rear brake pads per race meeting. John Hopkins never uses his . as far as racers go it comes down to preference i recon . I use mine on the road , but when i was out on track i didn't touch the bugger . Link to comment Share on other sites More sharing options...
porter_jamie Posted April 4, 2012 Report Share Posted April 4, 2012 Never ever use the rear brake, im simply not good enough. Only reason it is there on my racebike is scrutineering. I reckon it helps in the wet, but i can't do it. Link to comment Share on other sites More sharing options...
Battered636 Posted April 4, 2012 Author Report Share Posted April 4, 2012 The jokers in the BSB 125 GP class have a habit of running mountain bike alloy dics and micro calpiers through scrutineering as a matter of habit. Don't know if they've been stopped from doing this yet, but look at the safety implications. Regulations state in all classes that a rear brake must be present for a reason. If the front fails, how are you supposed to stop. Think of the kittens. Front brake failure never even crossed my mind! Plenty of good reasons not to bother, then. Cheers, fellas. Link to comment Share on other sites More sharing options...
lorenzo Posted April 4, 2012 Report Share Posted April 4, 2012 I never thought I used mine either, until the seals started weeping on my old TRX. I pulled the guts out of the caliper and waited for new seals to arrive but carried on riding, then within about a mile of leaving the house I instinctively went for the back brake, there was (obviously) no pressure at the pedal, and I poo'd myself. I then took the pedal off all together, to save me going for it. My foot was fishing around in mid air and I poo'd myself further still. I now have a fully functioning back brake, even though i don't think I use it a great deal. Link to comment Share on other sites More sharing options...
abos Posted April 9, 2012 Report Share Posted April 9, 2012 I have never been able to use the back break in the way described here, trailing into a corner etc but I do when I'm sitting in traffic on a hill and want to stretch my arms. strangely the rear brake on my ZX636 always gets a warning and a blind eye turned by my local MOT inspector as it does not work in fact you can push the bike along with the brake on, its on original pads and disc. My ZZR1400 back break works really well and only got picked up on the MOT as the pads will need replacing soon. the difference is that i rag the 636 around at weekends and odd track-days, the ZZR commutes me into the Olympic park every day 100 miles a day across the home counties and central London. Would I run a Alloy rear disc? Never as the thought of breaking in a emergency where you would apply all your available braking and the rear disc collapsing effectively locking the rear wheel does not bear thinking about! I agree with Wavy Dave on this there are easier ways to loose a fee grammes! Link to comment Share on other sites More sharing options...
Battered636 Posted April 9, 2012 Author Report Share Posted April 9, 2012 I have never been able to use the back break in the way described here, trailing into a corner etc but I do when I'm sitting in traffic on a hill and want to stretch my arms. strangely the rear brake on my ZX636 always gets a warning and a blind eye turned by my local MOT inspector as it does not work in fact you can push the bike along with the brake on, its on original pads and disc. My ZZR1400 back break works really well and only got picked up on the MOT as the pads will need replacing soon. the difference is that i rag the 636 around at weekends and odd track-days, the ZZR commutes me into the Olympic park every day 100 miles a day across the home counties and central London. Would I run a Alloy rear disc? Never as the thought of breaking in a emergency where you would apply all your available braking and the rear disc collapsing effectively locking the rear wheel does not bear thinking about! I agree with Wavy Dave on this there are easier ways to loose a fee grammes! Yep, it was a bloody stupid idea and I'm just glad I didn't think of it first. The logic was it won't get used and I've nothing left to lighten without junking essential road gear, Good job I asked. Titanium it is, then! Link to comment Share on other sites More sharing options...
sonic Posted June 9, 2012 Report Share Posted June 9, 2012 A bit late but I ran an Ally rear disc for 2 years and never failed scrutineering, Link to comment Share on other sites More sharing options...
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