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fork brace thoughts

Old 08-15-2010, 04:25 PM
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fork brace thoughts

i had my buddy with the zx12 over today to sync my carbs, which by the way were a full turn on the sync screw out of wack and the bike runs alot better now. anyways he rode the bike and we started talking about a front brace. hes a machinist so we can whip something up no problem. he was saying that the ones hes used on his race bikes mostly bolted on from both sides and didnt need the forks removed. so were thinking of basically taking a rectangular piece of aluminum, drilling a couple of big holes, or milling them, then cutting the ends off drilling and tapping them to get screwed back on. itll be prettier than a basic piece of rectangular aluminum but thats the idea were shooting for. any thoughts on that? anything we should know about it?
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Old 08-15-2010, 04:37 PM
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I thought Dr. Honda had this in the works? I agree one that could be mounted without removing the forks is very attractive though.
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Old 08-15-2010, 05:16 PM
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im sure he is. but this would likely cost me the price of material so thats why im asking. and im sure hed be willing to produce some extras at some point.
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Old 08-15-2010, 05:24 PM
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In the early '80s I put a Telefix fork brace on my '78 CX500 (modded for canyon racing, not the stock ugly one) after a nasty speed wobble at 90mph in a left sweeper. I'd had wobbles prior to that, but at 90 that one scared me. It was the bolt on type as you describe, and it worked great.
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Old 08-15-2010, 05:53 PM
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The difference between a bolt-together type and one you slip over the forkleg is that the bolt-together one needs to be about twice as thick to make it possible to use large enough bolts...

I'd say M8 or equivalent is about minimum for the threads to withstand the loads... And no, I'm not talkinhg about the bolt in itself, I'm talking about the aluminium threads... And with an M8 bolt you will need at the very least twice that in material, so around 20 millimeters of thickness or more... That's starting to become chunky...

A pinch bolt on a brace made from one piece only doesn't need to handle anything near the loads of the bolt-together type... An M6 or M5 should handle that nicely, making the brace about 10 mm or more in minimum thickness... Lighter and less bulky...

And you really, really need to get the spacing exactly right... If the brace pinches the legs together or push them apart even the slightest fraction of a millimeter, the forklegs will stick, causing very funky suspension characteristics, and possibly make the bike dangerous to ride...
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Old 08-15-2010, 06:05 PM
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Some good points. So what if instead of screws we machine one end to slide into the other and secure it with a towel and then set screw that into place?
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Old 08-15-2010, 06:07 PM
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speaking of a fork brace.....Any word on Dr Honda's final plan ???
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Old 08-15-2010, 07:07 PM
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Sorry that was supposed to say dowel. Spell check on the phone got it. Lol.
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Old 08-16-2010, 07:27 AM
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Originally Posted by uchi View Post
Some good points. So what if instead of screws we machine one end to slide into the other and secure it with a towel and then set screw that into place?
Think of it this way... A solid one piece brace has two load points, the two pinch bolts...

A two piece or three piece brace have two bolts at each joint, making it four load points...

Now, simulations and math can tell you exactly the numbers, but general rule of thumb says when you double the amount of loadpoints, you double the size of the load bearers, ie the bolts and the material around the threads...

Now that's a bit of oversimplification, and with some safetymargin... But it doesn't matter if you do two bolts or one and a dowel... It's still two loadpoints, and that means you will need something like an M8 with atleast 4-5 mm of material around the threads to handle the load...
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Old 08-16-2010, 07:48 AM
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Given that this is something that's not going to be taken off and put back on (in other words, install it and leave it alone), I'd lean toward a solid piece. It's really not hard to drop the fork tubes to install it, so for a little bit of work, you have something you can really trust and feel good about.

Just a thought.
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Old 08-16-2010, 07:53 AM
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true enough. ive gotta drop a fork tube over the winter anyway so maybe ill see about making a solid 1 piece instead
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Old 08-16-2010, 10:53 AM
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My Coerce brace had 2 M5 (1 front, 1 rear) screws on each side and worked fine. The center piece fit between the tops of the fork sliders, where the rock deflectors were. You can probably see one on their web site.

The brace primarily prevents scissoring of the fork legs, so it is the clamping friction that provides the stiffness. Not a lot of added tensile force on the fasteners.

Well worthwhile, IMO.
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Old 08-16-2010, 11:21 AM
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do you have any pics of it installed?
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