Frame geometry / layout / design

[brian 1100]

Al,

I suspect most modern have geometry to radical.
What about comparing/copying a ZRX1100?
It's a more modern take on the J with pretty much the same layout and weight.
I've just come back from the US after riding one 2000 miles round the twisty roads of North Carolina and Virginia.
It's still a heavy old beast and no modern sports bike but handles and steers much quicker than my old Lawson.



Brian

[coldsummer]

Thanks Al. I suspect the old adage is true, if it looks wrong it probably is.

[Jay1969]

I think it depends on the rider too, their body weight / mass, riding
tecnique etc. (I suspect I've spelled technique wrong ha ha ha!)

[Al]

Had a look see at bike specs and the ZRX's are 50 lbs heavier than mine as it sits.
They have a shorter wheelbase and much more power.

Had another thought and looked up the basics of the 'new' z1000 's.
They are much much closer to mine than the rex's
They have a little more power and a little more weight and again a shorter wheelbase and lower angle (smaller number) rake than mine if i read mine correctly.
25 degrees of rake and 102 / 103 ish trail, seems to be a common set of numbers combined with a wheelbase in the higher 1400's rather than low 1500's of mm as targets might be the way to go.

Been reading about tuning; pro and antisquat from articles in Sport Rider magazine.
Bloody confusing, but i think i need a little more pro and less anti so will try to accommodate these as i go along.
The few years i spent at Santa Pod etc with Andy's drag Z1r haven't all been wasted after all. That was pro squat all the way, this is a newer concept to me.



AL

[sanderz]

Would adjustable yokes be worth considering Al?

Not cheap at around the £500+ mark (+vat) - Harris listed here

http://www.harris-performance.com/acata ... Yokes.html

recon Spondon, Gilles or other yoke/billet machine shops would be around this figure.

Spondon yolks used to have shims to alter offsets so conventional bar risers could /would be out. These 'new' era yolks have adjustment on the stem.

[Al]

Thanks for that thought and the link.
It has been suggested as have Z650 yolks.
I think the 650's had a steeper steering angle or when fitted give a steeper angle.
However they are too narrow between the stauntions.
The adjustable types are outside my budget unfortunately.

Was looking at this photo from; 'Sharing' in the discussion forum and noticed what looks like an inch or more of fork leg sticking up through the top yolk!

If i can find a good clean side on photo i will scale off some dimensions including rake angle.





AL

[ADRIAN H]

some pictures here, may help ?

http://www.clems-garage.com/LMS%20web%2 ... 20like.htm

[markz9]

hi zorded be careful with studying photos if you look at the suzuki yoshi gs1000 that wes cooley raced, yoshi used to cut and weld (approx) extra 30mm on to the top of each fork leg then clamp the weld so it was hidden by the top yolk so it looked like they were dropped through the yolks
in fact the were longer !!
ive got harris adjustable yolks on my zed they only alter trial not steeper steering angle
Mark

[Al]

Thanks Adrian couple of good clear ones in there.

Mark if you are at Odiham this Sunday let me know which bike is yours and i'll try hard not to black flag it

Will be marshaling,...... but Brian 1100 will be on track.

AL

[brian 1100]

The US superbike racing was always limited on what they could do under the rules. The frame geometry couldn't be changed. They all cheated a bit, Suzuki the most apparently.
I'm sure I read somewhere that the GPZ750 was Rainey's favourite bike ever as it handled so well (but probably only compared to the Z1000 he had before).

But this talk of modifying gets me excited.
You go the frame/handling route Al and I'll go the other way - more power.
May not be practical to do anything more with the engine though.
Don't really want to go above the current 1170cc as it gets hot enough as it is on track. Will speak to Debben in the next few weeks.
I will be at Odiham this weekend unless the weather is awful.

Brian

[Robw]

I am going for the more power route with my new bike, 1260cc and gasflowed head, hopefully more horsepower than the Rep. Al I will try and measure the rake and length of mine if you want.
Rob