Quickening the stearing on a 81 GPZ1100

For a while I've been looking at way of quickening the steering somehow without jacking the rear way up which just messes everything up.
I know that Dave/AKA Dr. Gamma has that sweet custom frame that had the head moved rearward and he installed a KZ650 triple clamp (less offset). 

By chance, I was looking at a set ZN1100 triple clamps I have, and noticed they have less offset than the GPZ1100, more like the 650 and 550
but are for 38mm forks.  So in theory, I can use these increase trail (stability) and quicken the steering at the same time. 

I'll get some photos up later. 

577nitro/JES

wrote:

I can use these increase trail (stability) and quicken the steering at the same time. 

I'm pretty sure "stability" and "quick" are opposite directions when changing trail.

"the more rake and trail we have, the more stable the bike will become, although both steering and maneuverability may suffer for it. Conversely, when rake and trail are reduced, the bike will steer quicker and become more maneuverable, though it's usually at the expense of stability."

From:. www.motorcyclecruiser.com/playing-angles/

 

wrote:

wrote:

I can use these increase trail (stability) and quicken the steering at the same time. 

I'm pretty sure "stability" and "quick" are opposite directions when changing trail.




 

Correct, more trail will aid stability but won't quicken up steering, it would make it slower.. The GPZ's already have 29 degrees of rake, which is also quite "lazy" by todays standards.

I helped a friend recently change the rake on the front of his GPZ1100 B2 frame back to 26 degrees, it wasn't easy , a lot of measuring, more measuring , cutting and welding, this should only be done by someone that really knows what they are doing.

wrote:

For a while I've been looking at way of quickening the steering somehow without jacking the rear way up which just messes everything up.
I know that Dave/AKA Dr. Gamma has that sweet custom frame that had the head moved rearward and he installed a KZ650 triple clamp (less offset). 

 

Less offset increases trail, which slows steering.

wrote:

wrote:

For a while I've been looking at way of quickening the steering somehow without jacking the rear way up which just messes everything up.
I know that Dave/AKA Dr. Gamma has that sweet custom frame that had the head moved rearward and he installed a KZ650 triple clamp (less offset). 


 

Less offset increases trail, which slows steering.

Correct, you'd be surprised just how many people get this wrong...

Well thought for sure reducing offset would help, now I’m wondering why the heck did they did it. Oh well live and learn I guess.  I did understand increasing rake and reducing trail quickens but it becomes squirrelly if not matched with the proper offset.  Worth experimenting I think.  

The Z1  had way too much offset resulting in too little trail which is why people used to 650 triple for less offset to get more stability.

When people talk about how quick a bike turns they are usually talking about how easy it is to initiate counter steer and this is almost entirely a product of trail and wheel assembly mass. Any change that produces less trail will make the bike turn quicker but this has diminishing returns because the bike becomes more and more unstable with less trail.  I would measure your bike and see how much trail you currently have.

The best way to affect how quickly a bike initiates counter steer is through lighter wheel assemblies. Forged wheels, smaller diameter wheels, lighter discs, lighter sprockets, etc. These will have a profound effect on how quickly a bike changes direction as the reduced gyro will allow the wheels to tip over faster Additionally, less un-sprung mass means better performing suspension, and if that wasn't enough, less rotational mass equals more horsepower! anybody seriously looking to improve the speed of steering should look at the wheels first.

 Something else to consider: Engine rotation - this isn't changeable unless you have a lot of money/time, but many MotoGP bikes' engines run backwards from standard as the gyro from the rotating engine assembly cancels out the gyro from the wheels and helps limit wheelies. Clearly this is what Kawasaki had in mind in designing  in the KZ750/400/440 twins 

DoctoRot post=861249The Z1  had way too much offset resulting in too little trail which is why people used to 650 triple for less offset to get more stability.

When people talk about how quick a bike turns they are usually talking about how easy it is to initiate counter steer and this is almost entirely a product of trail and wheel assembly mass. Any change that produces less trail will make the bike turn quicker but this has diminishing returns because the bike becomes more and more unstable with less trail.  I would measure your bike and see how much trail you currently have.

The best way to affect how quickly a bike initiates counter steer is through lighter wheel assemblies. Forged wheels, smaller diameter wheels, lighter discs, lighter sprockets, etc. These will have a profound effect on how quickly a bike changes direction as the reduced gyro will allow the wheels to tip over faster Additionally, less un-sprung mass means better performing suspension, and if that wasn't enough, less rotational mass equals more horsepower! anybody seriously looking to improve the speed of steering should look at the wheels first.

 Something else to consider: Engine rotation - this isn't changeable unless you have a lot of money/time, but many MotoGP bikes' engines run backwards from standard as the gyro from the rotating engine assembly cancels out the gyro from the wheels and helps limit wheelies. Clearly this is what Kawasaki had in mind in designing  in the KZ750/400/440 twins 

Yeah if I had the money, Magnesium wheels, ect....   I did swap out with early GSXR1100 wheels, which are pretty dang light, and it did help.  It is what it is I guess.

577nitro
 

Measure your trail and see where you are. you can probably tighten it up some.

www.rbracing-rsr.com/rakeandtrail.html

wrote:

 I did understand increasing rake and reducing trail quickens but it becomes squirrelly if not matched with the proper offset.  Worth experimenting I think.  

Increasing rake does not quicken steering period, Look at most modern bikes, they have around 24 to 25 degrees of rake and 30 to 35 mm offset, giving trail of around 100mm , these numbers are averages but you can clearly see they don't have more rake. I'm in the middle of building my bike, it came stock with 27 degrees of rake, by raising the rear , and using a smaller front wheel,  I've been able to get it to 25 degrees of rake, which works with the 40mm offset triple clamps I'm using, My trail is just a tad over 100mm, I'll measure it exactly once its all bolted back together, that's using 18 inch wheels front and back. I suggest using a rake and trail calculator to find out what your measurement will end up with, you seem to the all over the place trying to understand front end geometry, that's not a criticism, most people don't, its quite complex...

Here's an online calculator, all measurements need to be accurate, ask questions here if you are struggling to understand it....  This calculator is set up for Harley's, ignore the "triple tree rake" just put a zero there....

www.rbracing-rsr.com/advchoppercalc.html

PS I see Doc has posted the same calculator..

Also, I've found , what I think are the perfect wheels for a swap on these old bikes, that is if you are going to go to 17 inch wheels, take into account I've also used a different front end and swingarm, and some mods to the wheels are to be done, I'll be swapping to these wheels later on down the track. They are a set of 17 x 3.5 front and 17 x 4.5 for the rear, they are from the late model 2017-2019 Z650 Kawasaki, 5 spoke and way lighter than the original Kawasaki mags. I'm having to machine a small amount from the front disc mounts, and some from the rear sprocket carrier but the difference in unsprung weight will be noticeable, I think they look great as well...  Its still a bit of work to make any aftermarket, or different model wheels fit though, not a job for the inexperienced.....