120 Jota rake and trail

martymoose

martymoose

Hero member
Location
Sydney, Australia
Hi Guys,

Only info I can find is in the reprint book of articles, ranges from 26 to 28 degrees rake, trail usually around 110mm, not all the tests have this info printed, mostly just wheelbase and seat height.  Hope they actually measured it and didn't just copy each other! 

Anyone tried to accurately measure rake and trail?  I have never tried!  Want to compare my 120 to Jugs'120.  Rake should be faily easy to measure with a plum bob and and protractor.  What about trail?  Length of wood taped to the steering head and touching the floor?  What is the established practice for actually measuring.

Rake on the RGS is bigger from memory, slower steering, and the Motodd frame that Rob Berryman has is really long in the front end.  I remember riding that and finding it "interesting". 

Anyone got rake and trail figures for other laverdas?

Cheers

Marty
 
from early green Book

SFC 28Deg/85mm
1000 EARLY Cerianis 28/123 fork leg1.5 steeper than steering head
1000/1200 late cerianis 28/100mm most 1200 had parallel fork to steering head
100/1200 Marzocchi 28/110mm

From late green book
same except last line
1000/1200 with Marzocchi 28/100


Jugs S


 
To actually measure it is not so easy Marty and to compare the factory starting point  to your 2 bikes is also not so easy.Real accuracy would mean looking at getting them Computacked.There head office is at Regents Park,96441946.
Your next option would be setting up rods through the steering head and swingarm pivot and setting up either string lines or piano wire,to see if the steering head  is square to the swingarm pivot.The man in Sydney for this is Laurie Alditon at Smithfield,don't know how he does it,last time I was there I asked if he had a Motolinner,he doesn't but said he wanted one.That surprised me as when they first arrived on the market every second bike shop had one.The alloy beam frames made any repairs redundant so not so many around these days.
 
Marty,
Measure rake by having bike on level surface and plumb-bobbing down from top and bottom of fork and doing trig.  Trail is thus worked out by scary number thingies using rake, tyre diameter and triple clamp offset - offset is 45mm and tyre diameter of 626mm rings a bell but best to cross check actual machine.
If none of this makes sense, call me and take some measurements and I'll plug it all in and let you know.
Cheers
Steve B
 
Take a look at http://www.rbracing-rsr.com/calculations.htm, has no less than 3 rake and trail calculators, complete with diagrams. Calculations don't look too complicated as long as you remember your high school trigonometry, only 40 years ago, right?
Hell, it's for Harley riders, gotta be simple :D :D

Ken
 
I thought this article interesting.

http://www.sportrider.com/tech/146_0310_art/index.html

They have worked the figures on weight bias verses change in rake TRAIL. the old I'll drop my forks through the tipple clamps and get some more weight over the front end or is it really a change in Trail that has the most effect.

though they are selling off set yokes

JugsS
 
Hey Marty, what do you mean by "interesting"??? The Motodd is running the early off set Ceriani clamps which should increase the trail if my thinking is right. Have no idea of the rake, a question for Phil Todd if you read this Phil.
As it is now the centre pipe is close to the mudguard under braking, enough to discolour the paint with the heat!!
I should try a set of "straight" yokes to see if there is a noticeable difference, the Cerianis have been on for 25 years so maybe a time for a change.
Phil, whats you opinion on different yokes then???
I can't fault the handling of the Motodd and it's way better than any standard framed triple I've ridden. Any improvement would be a bonus
Rob
 
Heya Rob,

I just remember it being very Looong in the steering, more like an RGS than a Jota. 

Hi Steve,

yeah, plumb bob sounds the way to go, I will give you a ring tomorrow.  Will be at the workshop.

Cheers

Marty
 
No worries Marty.  There is also various chassis calculation software on Tony Foale's website, the basic stuff is free to download and will do everything you are talking about.
Cheers
Steve B
 
Hi Rob - I think almost every type of yoke has been fitted to the Saxon/Motodd chassis over the years - nobody ever complained of poor handling - despite the fact that people generally like to waffle on about how they push their machines to/past the limit - usually pub talk -  I raced mine with the old "wobbling" Ceriani yokes and the later Marzo ones - couldn't really notice any difference - probably the sign of a fantastic frame design  :D :D - Regards - Phil
 
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