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Old 08-19-2011, 05:32 PM   #1006
jdrocks OP
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Quote:
Originally Posted by sanjoh View Post
I think that depends on the show

pinstripes and ghost flames. whadya think?
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Old 08-19-2011, 05:43 PM   #1007
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Originally Posted by DesmoDog View Post
It's certainly not unheard of. Ducati did it back in the day. Here's my '74 750GT. They did the same thing on the 750SS.

In other news, all these threads on dual sport Ninjas is making me jones for a project bike... nice work.

i don't know if i've seen one of those, nice lookin' bike.


the ninja/versys bikes make a good platform to start with. plenty of recipes out there now, so a lot of the guesswork is gone. huge bang for the buck if you can find a cheap project bike. got a PM from a guy just recently who found a dinged up Versys for the whopping sum of $350.
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Old 08-19-2011, 05:49 PM   #1008
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Originally Posted by donny662 View Post
The 70's era Honda disc brakes also had the caliper in front of the fork.

forgot about those, and i might have owned one. oh well...


the problem here is that the caliper/brake line extends 150mm from the centerline of the tube when using a 300mm rotor. i can't see anything good happening with that arrangement in front of the forks.
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Old 08-19-2011, 06:13 PM   #1009
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Originally Posted by CooperSmithingCo View Post
I don't recall giving you a reason to be rude...

if you consider any comments to be rude, please accept an apology.


i never said i didn't check the geometry. i did say what i have works, and works well in every road condition the bike has seen...high speed I system to very rough two track.

i'm just a hobbyist, but my bikes are designed and built tough for the conditions i intend to ride. i can assure you that there is nothing inherently dangerous in this build. it rides and handles better than the first two ninja builds, and those were both superb runners.

too bad you can't see the bike, photos don't do it justice. when they designated the "beast" category, someone had this bike in mind.
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Old 08-20-2011, 07:21 AM   #1010
mtothef
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everybody hug!

coop, i didn't read where jd was insulting you. might want to get used to the voices people use on this here forum. likewise, your build chops are impressive judging from the other thread you have going, and coming from the "pro" world you are going to see a lot of hack shit in here. jdrocks builds tend to be way more finished and polished and thought out than some of the abortions that roll out some garages (mine included).

but, to the whole rake/trail deal, you have a point in noting that reducing trail by increasing offset can lead to a crappy handling, even dangerous bike. however, you should also note that there is a larger diameter front wheel on this particular bike now than what it was originally sourced with. for a given head angle and wheel size, increasing offset will indeed reduce trail, and your 3-4" call is the generally accepted sweet spot for most bikes. but when you increase wheel size for a given head angle and offset, you will INCREASE trail, in which case it is common to increase offset to bring trail back into a reasonable realm again.

case in point, supermoto bikes. take a regular dirt bike with a 21" front wheel on it and slap a 17" in there, and suddenly you have a bike that feels kind of like a shopping cart when you get on the brakes into a corner. because you've decreased usable trail by decreasing wheel size. lose the leading axle forks, or slap on much shallower offset crowns, and some of that trail is regained. going up in wheel size, which is what many people do when converting street bikes to dual sport, as well as slackening head angles (which sometimes happens accidentally with longer travel forks, and sometimes is intentional to get a more dirt-spec head angle compared to what sport bikes have), calls for more offset to bring the trail back into line.

just sayin'. jdrocks bike probably handles fine...
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Old 08-20-2011, 10:38 AM   #1011
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Quote:
Originally Posted by jdrocks View Post
if you consider any comments to be rude, please accept an apology.


i never said i didn't check the geometry. i did say what i have works, and works well in every road condition the bike has seen...high speed I system to very rough two track.

i'm just a hobbyist, but my bikes are designed and built tough for the conditions i intend to ride. i can assure you that there is nothing inherently dangerous in this build. it rides and handles better than the first two ninja builds, and those were both superb runners.

too bad you can't see the bike, photos don't do it justice. when they designated the "beast" category, someone had this bike in mind.
Maybe all the estrogen in the house right now rubbed off on me. Can't blame me too much, I've been conditioned to assume every message passed to me from my wife or daughter must me cryptic and I stay on my toes.

The trail issue isn't purely speculative due to components, I printed off your profile shot and ran some lines. Like I said, impossible to know for sure from a photo. This might help: http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

Your bike is absolutely a beast, and I'm more than aware of the injustices a photo presents so I imagine in person it's truly a sight. Like I said, I'm a fan.
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Old 08-20-2011, 03:30 PM   #1012
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Originally Posted by CooperSmithingCo View Post
Maybe all the estrogen in the house right now rubbed off on me. Can't blame me too much, I've been conditioned to assume every message passed to me from my wife or daughter must me cryptic and I stay on my toes.

The trail issue isn't purely speculative due to components, I printed off your profile shot and ran some lines. Like I said, impossible to know for sure from a photo. This might help: http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

Your bike is absolutely a beast, and I'm more than aware of the injustices a photo presents so I imagine in person it's truly a sight. Like I said, I'm a fan.
That's a cool article. It got me to go out and measure my project. I think measuring lines on a photo is dicey because the photo angle and wheel position have to be perfect.

I'm sure that the triple clamp offset and spindle offset is a published value for these forks. Combine that data with the radius of the tire in a fancy equation to yield a trail measurement, right?
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Old 08-20-2011, 04:17 PM   #1013
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[QUOTE=dentvet;16673168]I think measuring lines on a photo is dicey because the photo angle and wheel position have to be perfect.QUOTE]

Without a telephoto lens from a distance, toatlly dicey, which is why I never said it was definitely wrong. I'm a big analog fan and would measure it in real world. If it has a hollow steering stem, pop the front wheel off and the measuring will be as easy as finding a rod long enough.
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Old 08-20-2011, 08:42 PM   #1014
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Originally Posted by dentvet View Post
I'm sure that the triple clamp offset and spindle offset is a published value for these forks. Combine that data with the radius of the tire in a fancy equation to yield a trail measurement, right?
Close, but I think you still need the rake angle of the steering stem. The longer forks and taller wheel will change the rake angle from the published stock Versys value. Plus, the longer rear shock also effects the rake angle.
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Old 08-20-2011, 09:02 PM   #1015
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Just checking in -- JD, I know Joe from another forum, and he is a good guy, despite being a bit defensive about his former cycle building direction. He's also a sharp guy: he noticed this just by eyeballing your pictures. I completely failed to notice it, even after reading the build thread.

Because you utilized the Versys triple clamps (designed for a zero-axle-offset forks) and put in DRZ forks (offset-axle forks) you have, I expect, less trail than you think you have.

Regarding trail, here are two samples from the book I illustrated (the one in the signature) that will clarify how triple clamp offset, axle offset, and rake affect trail. Rake is really almost a red herring -- the key to chassis geometry is trail.

I will confirm that with a little work, you can pragmatically verify the ground trail -- some like to use straight rods with a point, some like to use laser pointers, some like string and plumb bobs. Compare your findings to other well-handling bikes in the same category -- KTM 950, BMW HP1, and arguably the ultimate stable high-speed dirt bike, the XR650R.

While I think that we could spiral into an argument about what "optimum" trail is, the truth is that you need *some*, and how much is enough varies with your tolerance for different handling characteristics.

Too little, it's twitchy & unstable (i.e. predisposed to tank-slap), won't hold a line exiting corners, and wants to low-side. Too much and it steers like a truck, and won't turn in. If you're built like a brick shithouse and can manhandle a bike all day long, too much is probably OK for you -- like '70s Ducatis. If you have cat-like reflexes and enjoy sliding the front, too little is probably OK, too -- like the Aprilia SXV 550.

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Old 08-21-2011, 05:59 AM   #1016
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Originally Posted by Roadracer_Al View Post
Just checking in -- JD...
thanks for stopping in, great illustrations which visually clarify the issues under discussion.

this same discussion occurred back in January when i first mounted the the DRZ forks in the Versys clamps. several builders posted their concerns, as they have now, both theoretical and technical, and these concerns were not ignored. my own findings at the time indicated that the geometry should be in an acceptable range, even though the custom shock was not mounted then.

however, now the rubber has met the road...1500 miles of road. this build has graduated beyond theoretical, and entered the empirical stage. how does it actually handle in varied conditions and speeds? in a word, beautifully. i'd ride it anywhere a bike of this size can go, and if you follow the ride report, i'm going to try.

the photo that apparently spawned this latest discussion was taken from an odd angle and elevation as i kept a cluster of gas cans and a stack of bike tires out of the frame. there are better photos of the forks in the clamps back in the thread.


packing the bike today, this beast is headin' west...then other places.
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Old 08-21-2011, 06:44 AM   #1017
ktmklx
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1500 miles of real world testing beats second guessing every time. Good information posted (road racer al) and good discussion. JD enjoy the bike, I'm sure you will cause you know how. Safe travels.
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Old 08-21-2011, 04:03 PM   #1018
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Amen to that -- glad it works for you.
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Old 08-22-2011, 02:35 PM   #1019
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What a great thread,read it all in one sitting.Stay safe on your ride out west.I look foreward to reading your RR.
John
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Old 08-22-2011, 06:42 PM   #1020
jdrocks OP
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Safe travels.

thanks, appreciate it. should pass fairly near where you and your brother were riding. if mine runs as well as yours, i'll be pleased. the 650 ptwin based builds do inspire confidence...very reliable for these big excursions.

you may have seen the Versys/KLR to Alaska thread currently up. having been out west with your build, can you ever imagine going back to a carbed 35HP 650 thumper for a trip like that? not me...if i crack those throttle bodies open i want something big to happen...like right now.
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