Phil
Expert Class
Posts: 420
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posted March 29, 2002 01:59 PM
redelk, your current thoughts on...
lowering the 12. Even at 5'11" it just feels to dam tall. I'm thinking about 1/2" in front and 1" in back. I'd go 1" in the front to but it looks like the tubes start to taper to much. How does lowering affect the handling characteristics, good or bad? Is this something that,properly done, should be done equaly front and back to maintain factory geometry?
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redelk
Moderator
Please... speak to the hand.
Posts: 3212
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posted March 29, 2002 05:03 PM
This isn't exactly my "field of expertise"...
... but that's never stopped me from sharing my opinion before. As if I actually had ANY "field of expertise".
I'm of those that believes there's a reason why the guys wearing the little white lab coats (engineers) at KHI get all the BIG BUCKS and we don't. They know what the fuck they're talkin' about and most of us don't! Frame and suspension geometry is nothing short of a "voodoo" science. There are so many factors and aspects to it, the slightest change can really throw the whole thing out of whack.
Suspension settings, in itself is complex enough. That's why when you read a bike test in Road Racing World that they will actually measure the OEM tires, before replacing them with race tires or with tires from a different manufacturer. This is so the can adjust the suspension to compensate for the minuscule difference in tire diameters and/or pressures. So if they feel it's necessary to make adjustments for something as minor as that, one can hardly imaging how drastic moving the fork tubes or lowering the rear (more then 5mm or so) would be.
Let's say you got a side view engineering drawing of the 12R. Then you drew lines along the many axis points of the swingarm, shock, forks and all the other related aspects of the suspension and frame. THEN start moving just a single component around (i.e. move the fork tubes up a 1/2"). You'll start to see that just that one change affected just about EVERY other aspect of the bike's geometry and balance.
Myself being 5'9" and with a 32" inseam, I find the 12R to be tall as well. The way the Corbin seat spreads my thighs doesn't help matters. Almost every article I've read about lowering a bike's seat height has always had the same response. DON'T lower the bike by it's suspension. At least not if you want to keep the original handling characteristics of the bike. It's far easier to alter the seat foam.
Now just because those lab coat guys know a lot of math, it doesn't mean that they know how I like to ride. Their goal is setting up the perfect AVERAGE bike for the AVERAGE rider. Just like suspension settings, the overall geometry is full of compromises. It's also like a tire. You can either have it one way or another (grip versus mileage). You can't get 6K miles out of a tire that sticks like a racing slick and the same applies to the bike's handling. You want straight line high speed stability or something that cuts like a GP racer?
If you move your forks up in the clamp a 1/4", you'll notice the difference. You move them a 1/2" and the bike will respond to input substantially quicker. When I put a 120/60 on front, the difference in tire size lowered the front end ANOTHER 1/2". It also has several other effects on the bike. The F/R weight balance shifted more to the front, the rake and trail was further reduced and the damping, compression and rebound also changed.
Sure the bike turned a hell of a lot quicker, but since the rear ride height settings were unchanged, it was TOO quick. A CMRA racing buddy of mine said that it handled like his racing GSXR 750. A compliment? No, not really. What he was saying was that it required a lot more effort to control the bike because it was so twitchy. Reducing the rear ride height might have taken some of the twitch out of it, but it would also change the angles of every part of the suspension. The bike would be no where near as crisp as it was with stock settings an positions.
Even with different springs, fork oil and suspension settings, unless you tune suspensions for Eric Bostrom, odds are greatly against you getting anywhere close to the bike's original handling characteristics, much less improve upon them. Even though the lab coat guys made compromises to attain their "Average", they also attained a balance between the interaction of all the bike's suspension, frame and tire components.
Tweaking here and there will guarantee some sort of change. It might be to your liking and then again, it might not. Though I have no doubt taking Mad Mike's bike down a long straight stretch would be a blast. Taking that same bike though Deal's Gap would be a NIGHTMARE! Lowering the front and back in order to change the bike's seat height is not much different then "strapping and slamming the bike for drag racing.
If that's what your in to, it might not be that bad. On the other hand, if your into riding through the twisties at a "spirited" pace (I NEVER encourage any one to violate local traffic laws), lower the bike on both end will have disappointing results.
The bottom line is... to be perfectly honest... I DON'T HAVE A FUCKIN' CLUE ON WHAT I'M TALKIN' ABOUT! Hopefully some of the other board members, (i.e. Doug, swft, Y2K, et. al.) who ACTUALLY know about such things, will share the more "educated" knowledge on this. It's just that I think that you CAN lower the seat height by adjusting and/or moving the suspension... you just won't like the results!
If this post of mine doesn't encourage someone who REALLY knows about this knd of stuff to reply, it could only mean one of two things. Either I'm right or your just screwed because no one esle bothered to post. If I were you, I'd vote for the latter.
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There are only three sports: bullfighting, motor racing, and mountaineering; all the rest are merely games.
-Ernest Hemingway
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silver01bullit
Expert Class
on here too much
Posts: 333
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posted March 30, 2002 05:11 AM
I'm not Red Elk....but
I'll give you a shorter response 
I've played with all the settings you're wondering about, down in front, up in back. Up in front, down in back, etc. I can tell you from experience that lowering the front and keeping the rear stock will make the bike handle MUCH better and improve turn in greatly. Now, if you leave the back height stock then the amount you lower the forks in the triple clamps makes a BIG difference. I just moved mine up to 1/2" from 3/4" and it made a drastic difference. I'm not sure how I feel about it either. With the forks lowered at 3/4" I felt turn in was much quicker but not uncontrollable. It felt a little twitchy but nothing I couldn't handle. If you go more than 3/4" you'll need a steering damper cuase you'll be flirting with tankslappers. Unless you're drag racing, leave the rear ride height alone, it will slow turn in with the back dropped. I'm 5'8" with a Corbin and it's hard for me to reach but the handling improvements are worth it 
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Phil
Expert Class
Posts: 420
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posted March 30, 2002 06:56 PM
red and silver, thanks for the replys. Gives me something to think about. Starting to sound like I should leave well enough alone for now, at least till I have the ability to better utilize the bike as is and to tell what the changes are really doing.
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"Look at Dad, trying to look young again."
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MadMike
Moderator
FEAR THE BLACK FLAG!!!!!!!!
Posts: 6579
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posted March 31, 2002 07:18 AM
If I were you phil I would slam it and then start Dragracing every weekend! LOL... ive got my front down 1.25" and the rear is way down, not sure , my bike corners oh like one of those double decker buses in england! but is sure does go straigh very well!!!
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EastBayDave
Needs a job
Posts: 2245
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posted March 31, 2002 07:33 AM
Why not just cut the seat foam down...?
Cheap & easy...
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Enjoy the ride!
02' ZRX1200
00' ZX12R sold
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Phil
Expert Class
Posts: 420
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posted March 31, 2002 11:17 AM
Yea, I have thought about butchering up the Corbin. I'm not that happy with it any way. Mike, the only problem I'd have drag racing is it would become an addiction, same as everything else I do. But I have thought about a second bike just for that.
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MadMike
Moderator
FEAR THE BLACK FLAG!!!!!!!!
Posts: 6579
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posted March 31, 2002 08:22 PM
uhhh,uhh,ohhh, ummm,,, Im not addicted to dragracing! oh man ive got to go right now, leave me alone!!! Ive got to go watch my video's!!!! leave me the hell alone man!!
Mad Mike!!!
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Phil
Expert Class
Posts: 420
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posted April 01, 2002 04:43 PM
 Edited By: Phil on 1 Apr 2002 16:51
hmmm, lets see, extra 12r slamned and stretched with stroker motor, spare motor(wouldn't want to miss a weekend), new trailer, spare clutches, spare parts, awshit I don't need another money pit right now. I think for now I'll concentrate on just being able to launch it in street trim,without looping it, before some body on a Busa draws down on me. By the way Mike, that 12 with the sidewinder is looking good. Have you fired it up yet, it's got to be LOUD.
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"Look at Dad, trying to look young again."
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MadMike
Moderator
FEAR THE BLACK FLAG!!!!!!!!
Posts: 6579
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posted April 01, 2002 08:11 PM
oh yea sounds great!! Ive got around 85 miles on her now!! so my clutch is about broken in! hope by thursday night to have almost the 500 for the break in period! cool. I will have my friend do a videw so you guys can hear it! maybe bergie will post it for me!
Mad Mike..
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Koz
Expert Class
Posts: 304
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posted April 02, 2002 04:38 AM
If your not dragging all the time, leave the height alone. You want the height on the street for bad road surfaces and max. ground clearance, especially in turns. You can lower your riding position by modifying the seat. You can adjust the rebound & compression dampening, etc. to your liking, but do it a little at a time. (Make sure you have a reference point/base line before you start) The best overall handling for the street will be as close to stock height as possible. My 2 cents. If you want a much better overall ride get lighter wheels, you would not believe the difference.
Koz
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