I wonder...

Got a few minutes to kill before the missus and I take off for a weekend at a bed & breakfast over to Canyon Lake. Since the golf clubs are going, we will take her Crown Vic...

The interesting thing about the Chassis tech forum is that almost NO ONE asks how to improve the chassis on their bike to improve handling. While the longer swingarms and super-wide tires look sporty, do they actually make a bike handle better?

I think the secret of making a KZ handle is to upgrade the rear shocks and fork springs, do some strategic frame bracing, use some high quality bearings and most important, to use some good tires.

What does a longer swingarm and super wide rear tire actually do? From my experience, it makes the bike harder to lean and turn compared to the original. Do folks make these mods for looks or handling or do they think both will result. Lots of folks post pics of their super-wide rear tires; compare the before and after handling. Never hear many comments on how modern sport bike components work on a 30-35 year old frame. I know from experience that a Z1 or even a KZ900 frame flexes a LOT and lacks the rigidity to ever be a great handler without bracing... Not looking to set off a flame war; just curious about all the mods that have been done and how they actually affect performance.

HMMMM well George that is a very good question indeed.
for one myself the kz650c that i race has agpz750frt end and rear along with the 18" wheels front & back.i run avons am22 110/80 and am23 150/70.the frame has been raked and brace at the front sides and rear.more rigid frame.has tapered bearings in the crown.has roller bearings in the swingarm.has progressive shocks.fork brace and steering dampner.all this for racing.plus a few other little things. but all in all is a great handling bike on the track.the bike in question that i mentioned is modeled after both my 75 Z1's.but this topic is about street bikes not race bikes,seeing as i had some time to kill.also George hope you and the wife have a great time on weekend.am jealous because there is still a lot of snow up here and the course i usualy go to is still covered in a blanket of white 2-3 foot thick.
Regards Paul

the brit bike mag "bike" i got at barnes and noble last week had a really good bit about tires/grip and it covered many great points between the thin and thick and profiles...really good reading....
by the way that 650 is set up exactly the way i'm leaning on my 1000j project....really really nice finished project you have there...
guys that can go fast can go fast on a bike.... regarless of tire design...each bike calls for a different tire to do it's thing....yvon duhamell (sp) said they used to have to run a treaded tire in the z-1 race bike or it was toooo squirly...i get along plenty quick on whatever tire i wanna run...as long as i keep that tire in my minds eye while riding

Yes, those mods do not help handling at all. They just help with the launch. It's all about what people want out of there bikes. I was a launch guy 25 years ago. Now I prefer a well-rounded ride.

EricHa wrote:

Yes, those mods do not help handling at all.

The 17" tires and rims do help handling even if that's the only mod. You can get better tire selections and the tire/rim combo will be lighter than most if not all 19"/18" or 18"/18" combos. The lighter the tire/rim combo, the less unsprung weight and less rotational mass. Also the 17" tire/rims are smaller in diameter reducing the gyroscopic effect they have. The less gyroscopic effect, the easier it is to transition the bike from side to side.

Bracing the frame and upgrading the suspension and the handling improvement will further improve.

Here's a little example that might help explain things.

Each stock component has a value of 1.
Each upgraded component has a value of 2.


Stock tires/rims = 1
Stock Suspension = 1
Stock frame = 1
17" tires/rims = 2
Upgraded Suspensions = 2
Frame Bracing = 2

For example 3 is stock handling. Each upgrade gets you an extra point of handling. If you have all three upgrades then you max out on handling. But only upgrading one area, (ie a braced frame with uppgraded suspension but keep the stock sized 19"/18" combo= 2+2+1=5 points) will help but the entire upgraded package (6 points) would be best.


There is a point where wide tires on older bikes are just for looks, and that would be on stock or close to stock machines that have been lower and have an extended arm. I good tire in 18" or even the LTD 16" would be sufficient.

Later, Doug

Yes, as long as you are matching wider rear tires with fronts. A skinny front tire with a huge rear is not fun in the twisties. That is what I was referring to.

My bike seems to handle a bit better, it's got ZX7 forks and GPZ mono rear. My bike has a 150/70-18 rear and a 110/80-18 front, these tires aren't too sticky either, the back comes out on me sometimes. I can still carve up a canyon though. I was off the bike for a little over 4 years though.
Mark

I went from a 150 to a 180 on my Monster a few years back. Didn't like the feel, as the tires are not on the same axis the more you lean. Looked cool though.

.

The mods you suggest are pretty much the standard recipe to make the Z handle without huge expense. Lighter, smaller diameter wheels/valve emulators/modern suspension/lighter brakes & discs will all help handling. Shedding weight in general should not be under estimated, my bike weighs just over 400 lbs dry, not bad for a street bike. Then there's the weight of the rider of course :laugh:

Handling mods: Aluminum rims 2.15x18 front and 3.5x18 rear, 100/70 and 140/70 Bridgestone BT45 - which I like. Front fork with Racetech valve emulators and stiffer springs. Works rear shocks. Frame braced throughout + stock arm braced. The rear shocks are 15" so that kicked the back up quite a bit. Wheelbase 1" shorter than stock. Rake is now 24.5 (no load). It goes around corners quite well

Stretched arms, lowering and wider tires will definitely help getting the power to the ground and launch the bike. Good for going straight.

I don't think very wide tires (160 and up) are really good for anything except looks (on a Z) unless you are putting it on the strip and deflating to get a much bigger contact patch AND you have the horsepower to match it. For a street bike, anything over a 150 is pretty much a waste of money if you ask me, but if you like the look of a big tire then why the hell not...

wow i think a new war could be brewing...:laugh:

i think your guys bikes with the modern forks and rears and hoops and brakes and tires are superrrrrrrrrrrcool
and the folks on here who got a stock anything in the garrage are lucky and have an investment as well as a peice of beautiful history.....

but for MY money a mildly punched out and updated z with a lot of original look ..but..period correct updates...shocks,carbs,braces,bars,coolers...looks really CORRECT.....thats me though....
but if i was gonna spend 2500 to make my z bike updated and modern...lets see labor + money+loss of original parts allready purchased@ number of times a might change my mind=7500
would my money be better spent on a used allready correct mods,,,zx9,,,zx7r,,,zx11,,,83-84 gpz 1100,,,zx-1o,,,all can be found for under 3000-3500 once in a while...
then you got a z-1 good to go...modded and finished state....
and a modern 17" tired 120-140 hp canyon bike with a frame designed to have those wheels on it and a geometry designed in japan by some really smart little fellas and tested on top speed circuits to be a matched set......
hmmmmmmmmmmmmmmm.
flames they are rising.....

the best thing ..or at least one of the best things about this site,is that i can throw out an opinion like the ones i have on modding up a z.......and while i joke that a flame will rise.....
The other folks on here that have different views...styles of riding and mostly tons more experience ,are then gonna chime in ,sometimes with emotion,and by the end of that thread i have way more information.
a heated debate is often truer than a discussion.. for the most part,only then do folks share from their hearts instead of giving theory they heard somewhere or ideas that SOUND good....
i would be more comfortable sounding like an un-informed idiot...and learning from it....
than teaching all the time showing all that i allready know....
my nine year old neice is hard to be around...she allready knows everything...