cagimaha Posted February 1, 2010 Report Share Posted February 1, 2010 Hi all, I've bought a 1978 Kawasaki Z1R (yeah I'll get round to starting a build thread when I find the lead for the camera) and the plan is to make something like this... now as you can see the forks have been swapped round so the brake calipers are on the front of the forks a la most early 80's AMA superbikes. Does anyone know the reason they did this? I'm not that concerned with any logistical problems like locating the speedo drive or brake lines. I just wanted to check what the opinion was about wether the brake mounts can take the braking force as a tensile force instead of compression? My thinking is that the bolts will still be under the same shear force but the brake mounts on the forks may not be up to the task. As its got a mildly tuned engine and otherwise standard chassis I'm going to need all the braking I can get... Also as it weighs the same as a small rhino I'd rather the calipers weren't going to make a bid for freedom when I'm trying to get it to slow down before going into a corner. It's gonna take a bit of getting used to the fact that you have to slow down before the corner and go round it on a +ve throttle or it just wallows and understeers... As ever any help/derisive comments much appreciated, Ben. Link to comment Share on other sites More sharing options...
spacemonkey Posted February 1, 2010 Report Share Posted February 1, 2010 Hi all, I've bought a 1978 Kawasaki Z1R (yeah I'll get round to starting a build thread when I find the lead for the camera) and the plan is to make something like this... now as you can see the forks have been swapped round so the brake calipers are on the front of the forks a la most early 80's AMA superbikes. Does anyone know the reason they did this? I'm not that concerned with any logistical problems like locating the speedo drive or brake lines. I just wanted to check what the opinion was about wether the brake mounts can take the braking force as a tensile force instead of compression? My thinking is that the bolts will still be under the same shear force but the brake mounts on the forks may not be up to the task. As its got a mildly tuned engine and otherwise standard chassis I'm going to need all the braking I can get... Also as it weighs the same as a small rhino I'd rather the calipers weren't going to make a bid for freedom when I'm trying to get it to slow down before going into a corner. It's gonna take a bit of getting used to the fact that you have to slow down before the corner and go round it on a +ve throttle or it just wallows and understeers... As ever any help/derisive comments much appreciated, Ben. I think if I remember correctly they did it that way until someone suddenly realised steering inertia would be lessened if they put 'em on behind the legs. Link to comment Share on other sites More sharing options...
fran9r Posted February 1, 2010 Report Share Posted February 1, 2010 Bloody nice garage! Link to comment Share on other sites More sharing options...
cagimaha Posted February 1, 2010 Author Report Share Posted February 1, 2010 I think if I remember correctly they did it that way until someone suddenly realised steering inertia would be lessened if they put 'em on behind the legs. That'd make sense... Still its not like it's ever gonna have a quick turn-in. Do you reckon the mounts are up to it? Link to comment Share on other sites More sharing options...
cagimaha Posted February 1, 2010 Author Report Share Posted February 1, 2010 Bloody nice garage! Yeah I wish my shed looked like that... It's owned (the bike and the shed) by a guy called Steve Elliott. He's had 3 bikes in the PB obsession thing in the last couple of years; that moriwaki zed, a honda cb900 with a bandit engine and spencer paintjob and a ducati with a tl1000 lump in it. Seems to be quite the talented fella. He only lives about 30 miles from me but I've never seen any of his creations out and about though, guess I need to get out more. Link to comment Share on other sites More sharing options...
spacemonkey Posted February 1, 2010 Report Share Posted February 1, 2010 That'd make sense... Still its not like it's ever gonna have a quick turn-in. Do you reckon the mounts are up to it? I don't think it makes any difference for strength. The mounts are just in compression instead of tension. Link to comment Share on other sites More sharing options...
alexp5 Posted February 1, 2010 Report Share Posted February 1, 2010 Something to do with flex in the fork legs whilst simultaneously braking and steering? The exact definition escapes me though, it's lodged in the deepest darkest recess of my tiny brain. It may fall out when I sneeze! My old Suzi kettle had the fork legs swapped, I thought it looked odd so swapped them back. The brakes were surreal anyways, and I couldn't tell any difference between the two. Link to comment Share on other sites More sharing options...
will#224 Posted February 1, 2010 Report Share Posted February 1, 2010 I'd love a bike like that. I think the calipers are still available from AP too. Link to comment Share on other sites More sharing options...
cagimaha Posted February 1, 2010 Author Report Share Posted February 1, 2010 I don't think it makes any difference for strength. The mounts are just in compression instead of tension. Righto, I'll set about swapping em round then! Thanks, Ben. Link to comment Share on other sites More sharing options...
cagimaha Posted February 1, 2010 Author Report Share Posted February 1, 2010 I'd love a bike like that. I think the calipers are still available from AP too. Yeah as a poor impoverished student they're a fair way out of my price range too unfortunately! I'm gonna be doing the project on a shoestring so most mods are gonna be cheap ones like putting the forks on backwards, loud exhaust, wider bars, ditch the switchgear, mirrors and indicators, knock up a bit of a dash out of some scrap stainless with a big analogue tacho and a small speedo and maybe an oil temp gauge and have a go at bracing the frame a bit. Then I'll start saving for the obligatory oil cooler and some better brakes, forks, swingarm and wheels and a paintjob. Or maybe a vinyl wrap... Thats the plan as it stands. Link to comment Share on other sites More sharing options...
will#224 Posted February 1, 2010 Report Share Posted February 1, 2010 Yeah as a poor impoverished student they're a fair way out of my price range too unfortunately! I'm gonna be doing the project on a shoestring so most mods are gonna be cheap ones like putting the forks on backwards, loud exhaust, wider bars, ditch the switchgear, mirrors and indicators, knock up a bit of a dash out of some scrap stainless with a big analogue tacho and a small speedo and maybe an oil temp gauge and have a go at bracing the frame a bit. Then I'll start saving for the obligatory oil cooler and some better brakes, forks, swingarm and wheels and a paintjob. Or maybe a vinyl wrap... Thats the plan as it stands. Still sounds good to me! Keep an eye on ebay, i think some of the sidecar racing bods still use those calipers. Link to comment Share on other sites More sharing options...
cagimaha Posted February 1, 2010 Author Report Share Posted February 1, 2010 Still sounds good to me! Keep an eye on ebay, i think some of the sidecar racing bods still use those calipers. Thanks for the heads up, I'll keep my eyes peeled Link to comment Share on other sites More sharing options...
banoffee Posted February 2, 2010 Report Share Posted February 2, 2010 I don't think it makes any difference for strength. The mounts are just in compression instead of tension. maybe. however one setup means they'll still stop you if they fail and the other doesn't... Link to comment Share on other sites More sharing options...
Marb Posted February 2, 2010 Report Share Posted February 2, 2010 I was told that it had to do with brake bite. Back in the dat when they still had forks made out of marshmellows and calipers that didn't have any feel. When the calipers are placed behind the forks they want to squeez themselves between the forks and the disks when you brake. Modern bikes, with the mahoosive forks can stand this force and keep the brake calipers from flexing. However, the wobbly forks together with calipers that didn't do anything but bite hard the forks would flex, alowing the caliper to jam between the disk and fork and locking up the brakes. They were also called, self-powering brakes. I remember the early Dholda Honda Endurance racers suffered from quite a few front end lock ups and them moved to the calipers in front of the forks. If you move the clalipers tot the front you don't have this problem. Hope that makes some sense, and i could be completely wrong. Link to comment Share on other sites More sharing options...
alexp5 Posted February 2, 2010 Report Share Posted February 2, 2010 I'd love a bike like that. I think the calipers are still available from AP too. Norman Hyde stocks them: http://www.normanhyde.co.uk/search.php?tag=53 The classic single pot Lockheed calipers are a lot better than they have any right to be! Link to comment Share on other sites More sharing options...
cagimaha Posted February 2, 2010 Author Report Share Posted February 2, 2010 I'd be more worried about the calipers than the fork legs if you are going to reverse the direction of the front end. Many calipers are direction sensitive because either the piston sizes are biased - if they are mutipot calipers - or because the pad mounting arrangement only works in one direction. Hmm I hadn't thought of that, these calipers are a lot less sophosticated than anything on a modern bike though. They're twin piston and the pads are perfectly circular so I don't think that direction will be too much of a problem. maybe. however one setup means they'll still stop you if they fail and the other doesn't... This is sort of what prompted the debate... Not really a nice thought. I was told that it had to do with brake bite. Back in the dat when they still had forks made out of marshmellows and calipers that didn't have any feel. When the calipers are placed behind the forks they want to squeez themselves between the forks and the disks when you brake. Modern bikes, with the mahoosive forks can stand this force and keep the brake calipers from flexing. However, the wobbly forks together with calipers that didn't do anything but bite hard the forks would flex, alowing the caliper to jam between the disk and fork and locking up the brakes. They were also called, self-powering brakes. I remember the early Dholda Honda Endurance racers suffered from quite a few front end lock ups and them moved to the calipers in front of the forks. If you move the clalipers tot the front you don't have this problem. Hope that makes some sense, and i could be completely wrong. Yeah that makes sense too, my dad reckons they put them in the front to keep them running a little cooler then moved them behind the fork legs again when they realised that performance in the wet was compromised. I think I'm gonna do a bit more research before I go either way with this one. My first concern was wether the aluminium had the same compressive strength as tensile strength but it seems theres a fair bit more to it than that! As ever many thanks to all for the input, Ben. Link to comment Share on other sites More sharing options...
fran9r Posted February 2, 2010 Report Share Posted February 2, 2010 maybe. however one setup means they'll still stop you if they fail and the other doesn't... Hows that then? Link to comment Share on other sites More sharing options...
cagimaha Posted February 2, 2010 Author Report Share Posted February 2, 2010 Hows that then? Well my thinking was that if the calipers are behind the fork legs and the mounts break then the calipers will just bash into the fork legs but I would still have some form of stopping power. If the calipers are on the front and they make a bid for freedom then theyre gonna wizz round, yank the braided hoses which will compress the forks then probably either lock the front and send me into orbit or smash the fork legs to bits if they manage a full revolution. Neither is exactly a nice idea but I know which I'd prefer. Link to comment Share on other sites More sharing options...
banoffee Posted February 2, 2010 Report Share Posted February 2, 2010 Well my thinking was that if the calipers are behind the fork legs and the mounts break then the calipers will just bash into the fork legs but I would still have some form of stopping power. If the calipers are on the front and they make a bid for freedom then theyre gonna wizz round, yank the braided hoses which will compress the forks then probably either lock the front and send me into orbit or smash the fork legs to bits if they manage a full revolution. Neither is exactly a nice idea but I know which I'd prefer. yep that's what I meant. saved me typing it all Link to comment Share on other sites More sharing options...
fran9r Posted February 2, 2010 Report Share Posted February 2, 2010 I doubt that would be the case...unless your calipers and forks were shaped to make a fit that could withstand the braking force-my stock 9R calipers/forks would not, then your pretty much fucked anyway. I'd make sure the brackets were over engineered so that this would not happen in either case. Link to comment Share on other sites More sharing options...
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