Shane661
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Posts: 11494
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posted January 15, 2009 11:20 AM
Lowering Forks Internally vs. Strapped??
What are the advantages to lowering the forks internally?
With forks lowered internally is it possible to do away with the strap? Is there adequate rebound damplng? I am picturing the forks operating like a slide hammer and creating wheelie problems when they top out (since they don't have to lift the weight of the wheel until they extend fully). Also it seems like you would really have to increase preload to keep from smashing an oil pan after a wheelie.
Since the bike is apart, I am considering lowering them internally, if it is a worthwhile modification.
Shane
  
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KZScott
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posted January 15, 2009 11:37 AM
Shane, I dont think they can extend fully with internally lowered forks, but i think they would extend as much as a normal forked unstrapped bike, but not more. but i could be wrong.... Ive been told internally lowered forks handle bumps much better than a strapped bike if your shut down area is rough for example. we are leaning pretty heavily towards getting a set of lowering blocks from Schnitz to internally lower dads forks and get rid of the straps. wheelie issues arent an issue with bars tho...
my guess is that you can lower the forks internally, then strap it without lowering it further (just enough to limit suspension travel) and have the best of both worlds.
my .02 
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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tcchin
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Posts: 867
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posted January 15, 2009 11:40 AM
How are you planning on lowering the forks? I don't think you want to just take out preload and let the fork sag down to mid-stroke, if that's what you meant by "slide hammer". If you put a spacer or a longer topout spring between the rebound piston holder and the cartridge cap inside the cartridge, you will shorten the stroke. This will require you to run a higher-rate spring and adjust the length of the preload spacer. It will also require more low-speed rebound damping and possibly more rebound shims.
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Shane661
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Posts: 11494
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posted January 15, 2009 11:42 AM
I was looking at purchasing some lowering blocks from Schnitz.
I'm trying see where the big benefit is.
Shane
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KZScott
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posted January 15, 2009 12:07 PM
http://www.schnitzracingstore.com/catalogs/catalog.asp?prodid=4867851&showprevnext=1
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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tcchin
Zone Head
Posts: 867
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posted January 15, 2009 12:47 PM
 Edited By: tcchin on 15 Jan 2009 20:52
The strap is just a means of applying preload to the forks. So, in order to get the fork to deflect, you'd need to load the springs past the point that they've been preloaded by the straps. Before that point is reached, the front end is rigid and will not follow the road.
An internally-lowered fork has very little preload at full extension and settles into a race sag when the main spring, topout spring and gravitational forces are at equilibrium. The wheel will track for some time when the front wheel sees less than 1g, whereas a strapped front end will not. Likewise, at slightly more than 1g, the front end will absorb bumps, whereas a strapped front end will be rigid. If you don't want to mess with heavier springs to prevent bottoming, you can raise the oil level to increase the air spring effect.
Not to discourage you from supporting Schnitz, but I see about $10 worth of hardware in that lowering kit. You might be better off doing a McMaster-Carr lowering kit...
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woppi
Pro
Posts: 1362
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posted January 15, 2009 12:54 PM
quote:
I was looking at purchasing some lowering blocks from Schnitz.
I'm trying see where the big benefit is.
Shane
i use them !!!
and i would say ---- they are OK !
woppi
____________
1st TFA Member / Austria !
" if it has wheels or titts - sometimes you will get troubles "
2000 Limited ZX12R NOS
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Shane661
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posted January 15, 2009 12:55 PM
Ok. But it still looks like the bike will be more wheelie-prone. When the bike is strapped the weight of the wheel must be lifted at all times in order to wheelie.
Otherwise, the fork can move quickly for the first inch or so, and then have momentum when it tops out. That would seem to make the front wheel more likely to lift. Hence, my slide-hammer analogy.
It would seem that in order to keep from bottoming, you would need, as you say, to put a heavier spring in. This would also require increased rebound and compression damping...which may more may not be achievable without re-valving the forks.
Correct?
Shane
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NOX
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posted January 15, 2009 12:56 PM
When you strap, you do not have a front suspension working the way it should.
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almost_les
Zone Head
Posts: 590
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posted January 15, 2009 01:26 PM
i called schnitz about this once, they said that the blocks do not allow the forks to over extend. they still bottom out at the same place, they just dont fully extend anymore. so according to them, no slide hammer effect, just shorter forks. FYI, i've heard of some people getting the slide hammer going on when they just try to cut the springs or have their "mechanic" buddy work on them, so make sure you get everything done right
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tcchin
Zone Head
Posts: 867
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posted January 15, 2009 01:32 PM
You only have spring-assisted lift on the front end over the length of your race sag. Once you run out of sag, the fork is topped out and the wheel will lose contact with the ground. You can mess around with the topout spring (shorter and stiffer) to reduce the amount of overlap with the main spring. You can also add low-speed rebound to control fork extension rates. Of course, running low sag numbers will reduce the range over which you have spring-assisted wheelies, but it will also reduce the suspension's ability to conform to pavement features.
A stiffer main spring would require more rebound damping, but not more compression damping. As long as your low speed bleed circuit has adequate range of adjustment, you should be able to make do. Also, you can mess with your fork oil level to make your air spring effect more progressive and prevent bottoming.
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almost_les
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Posts: 590
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posted January 15, 2009 01:49 PM
shouldn't you be able to use enough rebound damping to cancel out most spring assisted wheelies? IMHO most the time its either on launch or a shift when there is a jolt to the chassis and it tries to jerk up the front tire. the only time the springs would really be helping out is on a power wheelie when the front is unloading too slow for the reboud damping to be effective.
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tcchin
Zone Head
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posted January 15, 2009 02:03 PM
I you run that much rebound damping, then the front end will pack down and fail to follow the road surface.
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almost_les
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posted January 15, 2009 02:08 PM
i see. so unless you have a perfect surface to run on, too much rebound becomes a bad thing. makes sense
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tcchin
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posted January 15, 2009 02:13 PM
Right. The spring doesn't have time to recover and release its stored energy, so you end up running too low in the stroke with too much preload, making the ride very harsh.
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KZScott
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posted January 15, 2009 03:16 PM
Tim, you dont have the part # of the $10 McMaster-Carr lowering kit do ya? (i need one for a 12)
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
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tcchin
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posted January 15, 2009 03:47 PM
Edited By: tcchin on 16 Jan 2009 00:18
Try:
Aircraft Spruce part #03-37610 1.5"x.049" 6061-T6 Al tube, $3.25/ft
Aircraft Spruce part #03-04800 .75"x.120" 4130 steel tube, $5.75/ft
http://www.aircraftspruce.com
Be sure to cut the new preload spacer (03-37610) shorter than the stock one by the length of the lowering spacer (03-04800) that you install in the cartridge. Also, be sure to include the thickness of any washers that you decide to add or remove in your measurements.
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whitehendrix
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posted January 15, 2009 05:03 PM
Tim.. man.. what the hell DON'T you know? seriously.. i think Scott's right. you've got a wifi connection in your head thats downloading and whatnot 24/7, dontcha...
i am anti strap all the way. the same way i'm anti bolt-on extention.
if you're going to compete on a professional level, i've always believed in prefessional components. straps are ghetto as hell, are horridly rough on the suspension and seals, don't give very good feedback, and God forbid the bolt comes loose or stitching shears. especially in the middle of a race.
internal lowering is touchy and must be done with caution and the correct components (or a correct reconstuction and modification technique)
choppin springs will yield horrid results.. tho "almost" not in the same ballpark, i'll go ahead and group that in with the ricer kids cutting the springs on their shitbox civics cuz it's cool.
same goes with bolt-on extensions. i HATE those things!! haha.. but, thats another rant.
my .001 cent there.. but ya.. internal lowering all the way.. and better yet, do what Tim said and make your own. no better way to know suspension inside and out than to build your own componentry!
and take pics. don't be greedy and hog all the fun and whatnot. share!!
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
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KZScott
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posted January 15, 2009 05:37 PM
thx Tim! ok Shane, go ahead and give it a go , I havent taken forks apart before 
if you do a write up, a monkey could follow the instructions 
my bolt on extensions and strap definately did their job 2 yrs in a row.... only sold the extensions to go even longer
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
Shane661
Needs a life
Posts: 11494
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posted January 15, 2009 05:39 PM
I've heard that the tools to do the 14's forks are very expensive, but I'll look into it...
Shane
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shiphteey
Needs a job
Posts: 2529
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posted January 15, 2009 05:52 PM
My lowered forks weigh more than stock. Strapping it makes it a FIXED BALLAST when you LAUNCH instead of unloading the suspension and wheelying either.
Lowered center of gravity and heavier up front.
For LSR make sure you get your ride heights right....you know what I went through.
A.
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Gemini Motorcycles
Topping out everything from Ninja 250s to nitrous ZX-14s.
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tcchin
Zone Head
Posts: 867
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posted January 15, 2009 05:59 PM
You can use two-piece split shaft collars to hold the damping rod and the cartridge to avoid damage to those parts. Sample McM part numbers are 6063K34 ($10.04) for a 24mm cartridge and 6063K16 ($6.62) for a 12mm damping rod. You will probably need a fork spring compressor to compress the spring while you remove/install the fork cap assembly. I made my own from a Quick-Grip bar clamp (McM 51755A26 $44.59) and some scrap metal.
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whitehendrix
Zone Head
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posted January 16, 2009 05:54 PM
you run bolt-ons, scott?
Hmm..
well, i guess maybe they're a little better built than i thought?
haha
(i still don't like em )
____________
Duct tape is the handyman's secret
weapon. The black is for formal
occasions. - ZRXDean
ill never own a busa unless
someone gives me one.... and then
ill sell it -KZScott
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KZScott
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posted January 16, 2009 06:21 PM
did 2 yrs in a row. there are good ones and cheap ones. 4-9 inches wasnt enough so im having my arm modified by spencer cycles to go up to 12 over
at 68in wb i dont see why my bike wont run 8s NA even with me driving
____________
01 ZX-12R 8.84 @ 156.3 no bars, DOT tires. Pump Gas, NA.... turbo 8.47 @ 164.
00 ZX-12R 8.62 @ 165.2 no bars, slicks, Pump Gas, 55 shot.... turbo 8.32 @173
00 ZX-12R Fastest NA Kawasaki in the world 1: 222.046 1.5: 226.390 Loring AFB
00 ZX-12R street turbo 1: 227.9 1.5: 234.1 Loring AFB
00 ZX-12R LSR turbo 1: 263.1 1.5: 266.5 Loring AFB Worlds fastest ZX-12R
CMG Racing RCC Turbos
|
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