frame rake

[ben james]

hi guys whats the best way to measure the rake of a frame.
ben

[hawkwind racing]

Ben 'please explain' do you mean how to measure what the rake angle is now ,or how to measure a change in rake angle
one method is to check the technical specifications of the model frame you have now , most manufacturers supply the rake angle ,
or use a plumbob from the top of the head stock and mark where it touches the ground ,also measure the length of the plumbob line from the top of the head stock to the ground, write that measurement down , now using a straight edge (any thing long and straight wil do )now use the straight line ,place it at the top of the headstock ,and follow the angle of the existing rake ,mark where it touches the ground ,then measure the distance from the top of the headstock to the spot on the ground , write down that measurement , now measure the distance between the two marks on the ground ,now using all those measurements you can produce a right angle triangle ,either use some trig to calculate the angle ,or scale down the triangle and measure the angle with a protractor , hope that helps
Gary

[gennyshovel]

It seems an awfully complex way of achieving a simple operation Gary,,when a spirit level(to find horizontal), protractor,,or even better, a combination protractor/level , slapped across the top steering head bearing race ,inline with the centreline of the frame will give the same result ???
Tiny.
Remember,,altering the fork length,wheel diameter,and/or rear shock length will not only affect the rake angle, but also the trail, and thats the important bit, if you want to go straight safely.

[hawkwind racing]

actually it sounds quite complicated but in practice it only takes a few minutes , and all you need is a string and bolt to place on the end of the string, a straight stick and a tape measure ,and very cheap you can use the same items to measure your trail and adding another straight stick align front and back wheels
Gary

[hawkwind racing]

or use one of these

[gazza414]

Plumbob way to go Gary....tried and tested

how did you ensure you never introduced any camber into the headstock when it was all done..ie is the back wheel following the front wheel?

Bitch that welding ...

[DirtyDave]

Genny's on the money Ben,
Rake and trail play a big part in steering speed, you need the centre line of your head stock to the ground not the fork legs, the triple clamp offset axle mounting position and wheel diameter affect trail,
your trail is measured from the point at which the head stock centre line meets the ground and the vertical line thru the axle centre meet the ground,
raising or lower the rear changes the trail and rack if not match by lowering the front,,
You can give yourself more trail buy swapping to a leading axle fork slider or getting a greater offset set of triple clamps, ( which i just happen to have in stock Benny. .)
In my opinion your better of bracing and lengthening your swing arm as most wondering is caused by swing arm and frame flex, especially from those high powered Kawasaki's LOL

[ben james]

thanks for all the responses guys, this gpz 1100 project is being sussed as we speak. lot of stuff going on in shed at moment, ducati undergoing repair, kermie being prepped for 07, new pit tent and camping facilities[girlfriend coming again in 07], new kwacka motor being built. tow vehicle needs new head. list is endless.
regards
ben

[SPOOK]

Hi Ben, I can lend you a book Motorcycle Chassis Design: the theory and practise. It may help you before you commence with the gas axe. I could drop it into your work next week. Cheers Russell.