Rake and Trail

[isiahstites]

I am getting ready to stretch, lower and rake the neck on my bike and was curious as to your thoughts on trail. I have not take all of the measurments yet, however from the info I do know I am thinking my trail number is going to be high. I know the number should be around 4-6 inches and was curious what kind of handling quality can I expect if it is above 6? I have done plenty of research over the years while building bikes on the subject, but do not have first hand experience in changing the steering neck.

Scott

[sheribuchta]

i run 52 degrees of rake about 14 inches of pos. trail  i dont think thats for everyone and i know this will start an arguement but rake and trail are your friend at high speed --all the rules that apply to cars have nothing to do with bikes because when you turn your wheels to the left on a car you will turn left --when you turn the front wheel left on a bike you will turn to the right yes thats right RIGHT --depending on the tube and stem offset  i would run 34 to 38 degrees of rake --i would run the smallest lightest front wheel and tire i could find and i would run no rear suspension  make sure that the front and rear wheel line up vertically  and you should be good to go and remember that steering must be limited to 15 degrees right and 15 degrees left 30 degrees total with very sturdy steering stops and a good steering damper (dampener)        willie buchta

[ol38y]

    but if you don't turn your bars back to the right pretty quick you're gonna be on your Acura...Eventually your bike is gonna go where your front wheel is pointing...  Ya mean counter steer.    From what I've seen in one year, which is not a lot I agree. But, what I have always considered optimum frame set up, ie dirt track or MX, is completely different here.

So Scott, get it where you like it, make it straight and blow the hood off...  Mines 39 deg. and if I remember right about 4" trail and runs straight as an arrow. But I only have half the motor you do. 

Larry.......  Yours to speed

[Sumner]

i.........................(dampener)        willie buchta

Willie a little off topic, but just curious as to why you don't log in under your user name, but under Sheri's??  Maybe a desire to be 50 again   

c ya,

Sum

[bak189]

Sum....don't ask Willie......ask "Landracing Jon"

[sheribuchta]

sum  sheri is on the computer most of the time but if it makes a differance i will log in --did you get your aluminum and how is the body coming  havnt heard     willie buchta

[willieworld]

hay i still remember my password     willie buchta

[Sumner]

hay i still remember my password     willie buchta

That's better, now I can sleep nights  . 

Yep got the aluminum with 3 of the 4 corners bent under.  I just today filed a damage claim against UPS Freight.  They called when it got to New Mexico and told me 2 corners were bent under and from there to here the driver managed to bend one more under.

I haven't started on the body yet, but maybe in a few weeks.  I want to finish up some other stuff first.  I'm welding up an aluminum fuel tank now.  Aren't TIG's the greatest??

c ya and you can still sneak in here under Sheri's name if you really want to  ,

Sum

[1212FBGS]

with that much rake and trail what will happen is the bike will go straight ....really straight.....so if you get blown slightly off course and are heading straight for a mile marker....your bike wont turn.... when you start counter steering the bike will start leaning in at the top but it wont turn.....so after you blow through the mile marker go back to the shop and pull it back....scott, there is no holy grail... you are racing a bike on slippery surface...dont kill your bike with silly numbers....do exactly as randy tells you to do....
kent

[wolbrink471]

Ummmm Scott or Kent......

For those of us keeping score at home, what did / does Randy tell you to do about the rake and trail?

Thanks

Mark

[willieworld]

that is pretty common --tell them a horror story to keep them from doing the right thing --heard them all my life dont pay any attention im speaking from 46 years of motorcycle riding experience --ive ridden and built just about everything on 2 wheels some 3 wheeled stuff also and at 63 i still ride last year riding 41620 miles  we have all had this discussion before  to no agreement --and will probibly have it again --my best advise is actually talk to 4 people who ride and pick something in the middle that way you will be in a safe zone  im probibly on the top of the scale at 50 something degrees if i were running a 2 wheel bike i would probibly keep the rake about 34 to 38 degrees   just some thoughts  and what works for some dont work for others  --if you want to see a horror story google RON COOK  look close and you will see a bike with to little rake although thats not the only problem   willie buchta

[racin jason]

250+mph Hayabusa's are running 28 degrees rake and 90mm of trail.

Willie,
At what rake does the front wheel want to flop?
Is there a point where too much rake causes the bike to be unstable?

[bak189]

Check out the rake and trail on Denis Mannings
Lucky-7 liner (with Telly-forks)................stable at
350+ mph

Those numbers, are the ones I would choose!!!!!!

[1212FBGS]

Wheeler runs 28 in his liner I ran 26..whan I ran 35 it wouldn’t steer…. Now on a sit up bike you can run lots of rake cuz you can compensate by leaning off the bike to make it turn….in a liner you don’t have the ability of body english to use… that’s why I know for a fact that anything more than 35 is useless…There have been tons of studies and papers done like the "Roland and Sharp" study on front fork oscillation done in the 60's... Willie I understand you have been riding for 46 years but you really need to get off your soap box on frame geometry before someone gets hurt from your unfounded advise… Harley Davidson has been building bikes for over 100 years and they don’t put 50 deg on anything... theirs absolutely no reason to use anymore than 38...over that a telescopic fork ceases to function properly due to weird angles…willie have someone use about 6 ratchet tie down straps and get yourself strapped down tight on your bike so you cant move anything but your arms and then try to ride your bike…you’ll be singing a different tune real fast
kent

[Dean Los Angeles]

But it's so easy:

Where Rw wheel radius, Ah is the head angle measured clock-wise from the horizontal and Of is the fork offset or rake.

Yeah, that's it!


Jason has the right numbers. Numbers in that region allow good stability at speed and still miss the mile markers.

I'm with Kent that 52/14 gives you the straight line stability but won't turn if you really need it.

Oh, and for the challenged: 90mm = 3.54 in. = 0.0000559234073013601 mi.