Understanding suspension.

I am in need of some info about suspension.
I have a book by Kevin Cameron. in it he says that the old bikes where not able to go less than about 26* of rake without becoming unstable at speed on 100 hp bikes. I’m not exactly sure what he means by that. what does hp have to do with it , unless he means the added torque on corner exits? Then he says this was improved with the mono shock.
Does anyone have any good info on the transition from dual to mono shocks and why?
my bike now has a ZX9 front end and ZRX rear end. I have 26* of rake with the rear shocks laid down.
The bike rides ok but has too stiff a rear end. it will bump me off the seat on medium sized bumps.
When I take it to red line in 5th it is stable in a straight line. but if I hit a dip at say 80 miles/hr. it wobbles.
if I raise the shocks to a more vertical stock location the rear spring rate is better but the rake drops to 22.5*. I have not done much testing this way as yet.

I dont know about rake and all but I just bought some shocks similar to yours. Are your rear shocks so stiff they throw you off the seat? Are yours air shocks and what kind are yours? Just trying to get an idea of how they will handle and if the shocks contribute to your bike being wobbly at high speeds.

These are the ones I got just wondering if they are the same. Marzocci Strada is what I was told but am not 100% sure. Thats a good looking bike by the way

those are kyb shocks off of a zrx1200 i am pretty sure.

leon holmes

I have a Kawasaki OEM steering damper on my '73, put it on there within the first year of ownership and I've never had a wobble problem.

Did you have the wobble before you swapped swingarms? Swingarm bushings/bearings if not just right can contribute to this problem.

yes they are zrx12 shocks.
i only have a wobble isue at lean. its kinda fun though:woohoo:

but safe , :laugh: .
I have an old steering damper. that will have to go on for sure. i need to have a tab welded on somewre first though.
Kawickrice those are nice looking shocks, how long are they?

650ed wrote:

Did you have the wobble before you swapped swingarms? Swingarm bushings/bearings if not just right can contribute to this problem.

I don’t think so ED. but I never rode it hard with the stock arm. But it doesn’t show up unless I’m going pretty fast through a corner and hit a dip.
It has good bearings, unless the tolerance in the new sleeve I had made is too loose? I had to have a sleeve made to shim the kz swing arm bolt to fit the larger diam zrx bearings. Food for thought. I will have to jack it up and check for play.
Thanks.

mark1122 wrote:

Kawickrice those are nice looking shocks, how long are they?

They are 14 inches eye to eye

mine are 14 1/4". and are a little long for the new front end. yours should be good with a stock kz.

anyone give me some insight on the transition from old school to new school, in regards to improving handling?
i have some basics but would like more detail so i can improve my kz's handling.
I want to learn a little more about the old tube frames and suspension .
So far the theory is:
1. u need to stiffen the frame ,mostly in the neck and at the swing arm pivot.
2. more weight forward. Modern bikes are weighted 50/50 f/r to 54/46%.rakes are 22.5 to 24.5*. This puts more load on the front wheel and slows the steering, this then , allows u to quicken the steering with less rake.
3. longer travel twin suspension helps take load of the frame. I need to understand this 1 better. Some how the mono shock helped here.
why did they lay the top of the rear shock down a bit?? this would give them more clearance and a steeper rake.is there more to it han that? i found that this made my springs too stiff. if u lay them down and respring would u have to revalve?

i think in either the modern sportbike book or his top dead center book ..kevin tells why they started moving the top shock mounts forward ...if i remember right,it was to mimic a type of rebound effect that shocks back then did not have the ability to tune/adjust in...the later j models had the mounts forward stock....the rest are good questions and i am aware of the higher speed wobbles you mentioned..my bike has a stock 19 in front and koni shocks.....in looking at your front end (and others ...ie german modded bikes...) i have wondered how they "really " handle at full pace sweeping corners with bumps in mid corner...the first bikes to start smnaller wheels gpz-gs1150-interceptors were sat down in front like the many reto modded z's i see...,they would
really get your attention in fast sweepers and cause grave concerns and big fast get offs....my 19 with no dampner,no fork brace,and single disk,can track very well at 100....new springs new oil,air caps and correct profile tires also....the frame and bike were made for this type of front end....the early z racers had to run treaded fronts to track......just thoughts...mark1122 wrote:

anyone give me some insight on the transition from old school to new school, in regards to improving handling?
i have some basics but would like more detail so i can improve my kz's handling.
I want to learn a little more about the old tube frames and suspension .
So far the theory is:
1. u need to stiffen the frame ,mostly in the neck and at the swing arm pivot.
2. more weight forward. Modern bikes are weighted 50/50 f/r to 54/46%.rakes are 22.5 to 24.5*. This puts more load on the front wheel and slows the steering, this then , allows u to quicken the steering with less rake.
3. longer travel twin suspension helps take load of the frame. I need to understand this 1 better. Some how the mono shock helped here.
why did they lay the top of the rear shock down a bit?? this would give them more clearance and a steeper rake.is there more to it han that? i found that this made my springs too stiff. if u lay them down and respring would u have to revalve?

plus you got bookoo motor...so that changes most info folks will give on set ups...i wheigh 285-300 so that might be keeping my rear tire tracking and hooked up some too i bet....i read an article in a vintage cycle where the editor/guest rider ..took lawsons elr/1000j season winner out on a track and could not match his personal bikes )gpz550) club times.....eddie/muzzy and co and a crate or three of shocks..tires triple trees and spares made some tracks rideable i guess.....do you think your rear is so stiff that it is overwhelming the frames rear tracking...and flexing the center of the bike back and forth?