F5 Dave
20th July 2010, 16:40
<link rel="File-List" href="file:///C:%5CDOCUME%7E1%5Cdavid%5CLOCALS%7E1%5CTemp%5Cmsoh tml1%5C01%5Cclip_filelist.xml"><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><style> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-NZ;} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> </style><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> Here are some random thoughts and hints about building a bucket with adequate & safe brakes<o></o>
Maybe a Sticky Mods?
<o></o>
Over the years I have witnessed many novel & imaginative setups. On the other hand I have seen some howlers bordering on the downright dangerous. Last weekend I witnessed the probably the worst Muppet engineering I have ever seen<o></o>.
This is by no means a complete guide and I am by no means beyond making dumb mistakes or logic farts<o></o>
I will largely omit drum brakes except to say that they are largely crap with too small hubs or leverage from both ends to be effective without thoroughly expensive classic parts, but most people will find a disc end.<o></o><o></o><o></o><o></o>
Brake mounting bolts<o></o>
Don’t use ally bolts anywhere near brakes. Levers, disc, and calliper mounts should have good quality steel bolts (or titanium if yer a wanker).<o></o>
<o></o>
Brake levers
C’mon pattern levers are cheap. Ball ends taped on are not kosher or justifiable. Beware the wrong lever. Also must have some free-play to the piston or the return hole will get blocked when hot. Attn with a file on the brake light switch tab or stopper will increase this. Don’t use an ordinary bolt, the threaded part will dig into the pivot. Grease this pivot.
Make sure the lever cannot be obstructed by anything; say if your throttle housing slips<o></o>.
Brake lines:
Divided opinion, but generally a braided line will be a stella improvement over a 20yr old rubber line. Make sure they are made long enough for when at full extension (wheelie) but not so long they will drag or be at a crazy angle. Consider routing & guides to avoid damage in suspension use<o></o>.
Brake plates<o></o>
This is where I lose sleep. They have a large force exerted on them. Some thin ally plate with the calliper stuck on it will twist & bend in several directions every time you clamp the brakes on a decent size disc from 80kph. This won’t do pretty things to your disc & ally fatigues in this application if it's flexing. Stiffness & strength are key. Start off with 10mm min plate & thicker if you need to significantly step the plate. Make a template from plywood & get someone to cut the plate & machine steps/ thread for mounting bolts. You may need to take a couple of hits at it to get the step the right thickness so the calliper is centralised & not rubbing. Obviously pads should cover the disc swept area nicely<o></o>.
Sticking brakes<o></o>
Bent or coned disc, muppet mounting, sticking pistons or sliding pins, dodgy wheel spacers. Or blocked master cylinder vents or return hole (see levers)<o></o>.
Brake discs
The most expensive component & easiest to damage. You shall need to check it is straight & flat (not cone shaped). The former by spinning the wheel with a pointer taped on the forkleg almost scraping the disc. Attempts to straighten discs are usually temporary. Maybe 25% successful. Glaze can be removed with sandpaper<o></o>
Mounting a disc on another wheel is possible but use your noggin. They have a large force exerted on them. One can get away with a thinner disc than stamped on for WOF, but don't push it, esp if disc gets hot. You can clean up grooves by giving it to someone with a lathe & careffuly holding some sand paper on a block against it. I said carefully<o></o>. A flapper wheel on a disc grinder can be mounted on lathe for a 'bush' but surprisingly effective result. No legal responsibility on above or any statements. Ah heck just send it to precision grinders or whatever.
<o></o><o></o>
Bleeding brakes:<o></o>
Read up on internet. With non std fittings you may need to lift front of the bike up to get the bleed nipple to the top of any air pockets. Look carefully if this takes a long time to bleed.<o></o>
<o></o>
Brake pads<o></o>
Will need replacing if worn with angle or any oil contamination. Glazing (but not contamination) can be removed by wiping on medium sand paper on a flat surface. Quality varies, you may have to try a few brands till you get one that suits your disc material<o></o>.
Getting the best out of current setup:
Calliper Pistons must be un-seized, sliding pins free with high temp grease. Old setups should be pistons pumped out & seals carefully removed with a pick or small screwdriver down the edge but not skewering it. Clean out gunk behind pistons & white build-up in seal grooves (read up how to get them out). Clean totally. Inspect seals. Largely the main inner seals if undamaged will be fine if square in section. Outer Dust seals are less important, but if deformed can pull or jam the pistons causing excessive lever travel or dragging respectively. Replace as required.
Corrosion damage to the pistons or the ally bores can often be dressed gently with pot scourer, but at some point are irretrievable.
Master cylinders are a little more difficult to dismantle but the above applies. Seals more likely to need replacing. Clean cap vents. Replace rubber doffer in the cap if torn. Really<o></o>.
Wheel spacers<o></o>
These aren’t hard to knock up to suit a new wheel, but to get them parallel and the right thickness is the trick. You mustn’t need to dramatically lever them in when fitting a wheel, nor have the axle pull in when done up. This x10 importance on forks<o></o>.
Upgrading braking power, mix & match:<o></o>
OK assuming you’ve checked the above. Like everything else leverage is key. The bigger the disc the more the leverage. The bigger/longer the brake lever the more the leverage<o></o>.
A big disc is nice, but weight is a consideration. A more modern calliper with decent pads is worthwhile. I found a decentish calliper off an RG150, but turned out to be a rear & the pads available were all rubbish.<o></o>
Hydraulic advantage: Often misunderstood, but the basic simple rule is “smaller the master cylinder & more piston area in callipers the more leverage”<o></o>.
Just like moving the pivot point of a lever closer to the object you want to lift, - the more leverage you get. It gets easier to pull the long lever & lift the heavy object. But the downside is the object (pads) move less.
So If you put a master cylinder from a twin calliper setup on a single calliper you will get a wood like feeling from the lever & no power. Conversely a too small a cylinder will produce excessive lever travel (some of which may be gained back from braided lines). There will be a sweet spot where you will get a good feel of leverage & power. Most single setups will have a ½” (12.7mm) bore (cast on cylinder bottom). A reduction to 11mm for example can work well in some instances.
Let's be safe out there & if in doubt ask an expert.<o></o><o></o><o></o>
Maybe a Sticky Mods?
<o></o>
Over the years I have witnessed many novel & imaginative setups. On the other hand I have seen some howlers bordering on the downright dangerous. Last weekend I witnessed the probably the worst Muppet engineering I have ever seen<o></o>.
This is by no means a complete guide and I am by no means beyond making dumb mistakes or logic farts<o></o>
I will largely omit drum brakes except to say that they are largely crap with too small hubs or leverage from both ends to be effective without thoroughly expensive classic parts, but most people will find a disc end.<o></o><o></o><o></o><o></o>
Brake mounting bolts<o></o>
Don’t use ally bolts anywhere near brakes. Levers, disc, and calliper mounts should have good quality steel bolts (or titanium if yer a wanker).<o></o>
<o></o>
Brake levers
C’mon pattern levers are cheap. Ball ends taped on are not kosher or justifiable. Beware the wrong lever. Also must have some free-play to the piston or the return hole will get blocked when hot. Attn with a file on the brake light switch tab or stopper will increase this. Don’t use an ordinary bolt, the threaded part will dig into the pivot. Grease this pivot.
Make sure the lever cannot be obstructed by anything; say if your throttle housing slips<o></o>.
Brake lines:
Divided opinion, but generally a braided line will be a stella improvement over a 20yr old rubber line. Make sure they are made long enough for when at full extension (wheelie) but not so long they will drag or be at a crazy angle. Consider routing & guides to avoid damage in suspension use<o></o>.
Brake plates<o></o>
This is where I lose sleep. They have a large force exerted on them. Some thin ally plate with the calliper stuck on it will twist & bend in several directions every time you clamp the brakes on a decent size disc from 80kph. This won’t do pretty things to your disc & ally fatigues in this application if it's flexing. Stiffness & strength are key. Start off with 10mm min plate & thicker if you need to significantly step the plate. Make a template from plywood & get someone to cut the plate & machine steps/ thread for mounting bolts. You may need to take a couple of hits at it to get the step the right thickness so the calliper is centralised & not rubbing. Obviously pads should cover the disc swept area nicely<o></o>.
Sticking brakes<o></o>
Bent or coned disc, muppet mounting, sticking pistons or sliding pins, dodgy wheel spacers. Or blocked master cylinder vents or return hole (see levers)<o></o>.
Brake discs
The most expensive component & easiest to damage. You shall need to check it is straight & flat (not cone shaped). The former by spinning the wheel with a pointer taped on the forkleg almost scraping the disc. Attempts to straighten discs are usually temporary. Maybe 25% successful. Glaze can be removed with sandpaper<o></o>
Mounting a disc on another wheel is possible but use your noggin. They have a large force exerted on them. One can get away with a thinner disc than stamped on for WOF, but don't push it, esp if disc gets hot. You can clean up grooves by giving it to someone with a lathe & careffuly holding some sand paper on a block against it. I said carefully<o></o>. A flapper wheel on a disc grinder can be mounted on lathe for a 'bush' but surprisingly effective result. No legal responsibility on above or any statements. Ah heck just send it to precision grinders or whatever.
<o></o><o></o>
Bleeding brakes:<o></o>
Read up on internet. With non std fittings you may need to lift front of the bike up to get the bleed nipple to the top of any air pockets. Look carefully if this takes a long time to bleed.<o></o>
<o></o>
Brake pads<o></o>
Will need replacing if worn with angle or any oil contamination. Glazing (but not contamination) can be removed by wiping on medium sand paper on a flat surface. Quality varies, you may have to try a few brands till you get one that suits your disc material<o></o>.
Getting the best out of current setup:
Calliper Pistons must be un-seized, sliding pins free with high temp grease. Old setups should be pistons pumped out & seals carefully removed with a pick or small screwdriver down the edge but not skewering it. Clean out gunk behind pistons & white build-up in seal grooves (read up how to get them out). Clean totally. Inspect seals. Largely the main inner seals if undamaged will be fine if square in section. Outer Dust seals are less important, but if deformed can pull or jam the pistons causing excessive lever travel or dragging respectively. Replace as required.
Corrosion damage to the pistons or the ally bores can often be dressed gently with pot scourer, but at some point are irretrievable.
Master cylinders are a little more difficult to dismantle but the above applies. Seals more likely to need replacing. Clean cap vents. Replace rubber doffer in the cap if torn. Really<o></o>.
Wheel spacers<o></o>
These aren’t hard to knock up to suit a new wheel, but to get them parallel and the right thickness is the trick. You mustn’t need to dramatically lever them in when fitting a wheel, nor have the axle pull in when done up. This x10 importance on forks<o></o>.
Upgrading braking power, mix & match:<o></o>
OK assuming you’ve checked the above. Like everything else leverage is key. The bigger the disc the more the leverage. The bigger/longer the brake lever the more the leverage<o></o>.
A big disc is nice, but weight is a consideration. A more modern calliper with decent pads is worthwhile. I found a decentish calliper off an RG150, but turned out to be a rear & the pads available were all rubbish.<o></o>
Hydraulic advantage: Often misunderstood, but the basic simple rule is “smaller the master cylinder & more piston area in callipers the more leverage”<o></o>.
Just like moving the pivot point of a lever closer to the object you want to lift, - the more leverage you get. It gets easier to pull the long lever & lift the heavy object. But the downside is the object (pads) move less.
So If you put a master cylinder from a twin calliper setup on a single calliper you will get a wood like feeling from the lever & no power. Conversely a too small a cylinder will produce excessive lever travel (some of which may be gained back from braided lines). There will be a sweet spot where you will get a good feel of leverage & power. Most single setups will have a ½” (12.7mm) bore (cast on cylinder bottom). A reduction to 11mm for example can work well in some instances.
Let's be safe out there & if in doubt ask an expert.<o></o><o></o><o></o>