The Chopper Compendium

So the story goes that i got this springer for a song and a dance. I found a counte's customs take-off sugar bear springer. i bought it for the fact of wanting to blueprint a sugar bear springer (the last springer i needed to blueprint for my important springer blueprint collection). I bought it blueprinted it and sold it. a few weeks later the guy asked if i could buy it back as he lost his job. no problem to me. I then decided i would put it on a bike. it went on a 95 883 sporty that needs to be chopped. So here is the beginning stages of a sporty frame built to an existing frontend. I was not sure of what rake or up and out this frontend was built for so i had to mount a wheel and set the rocker bolts to 10-15 degrees off horizontal to get the stretches and rake set. i used a stock sporty wheel/tire(19 rim with a 100/90/19) rather than a 21 like sugar bear calls for. all that did was bring the overall up stretch down by 3/4". So right now the bike sets at 43-44 degrees rake and the top of the bottom tree is 36 3/8" off the ground. that is a 4 up off of softail standards. its about an 8 to 8.25 up on the sporty. I still need to figure out the out and the rear stretches. i think i am doing a 4" rear stretch and a 2 out front stretch. once all of that is figured out i will cut the frame for the hardtail and then do the backbone and upper wishbones to make a nice straight line to the axle blocks.

thats a real nice lookin front end there its gonna look sweet on that sporty all raked out long and low

Very cool looking springer, i personally like to keep my bikes rake around 36degree or less. I like my bikes to handle tight and easier to turn. Still very nice man.

Ahhh yeah....long & low....thInk it would look nicer with a thinner tire up front though....jmo...oh & spokes...again jmo

jonester123 wrote:Very cool looking springer, i personally like to keep my bikes rake around 36degree or less. I like my bikes to handle tight and easier to turn. Still very nice man.

very big misconception on long bikes not handling or having huge turnabouts. I have worked hand and hand with gary(the chopper handbook writer) bought every big name production springer and built literally hundreds of homebuild ones. If the springer is built to spec or if the frame is built to spec of springer (not what is told but solid measurements) my bike will actually out perform my hydro forks. That is girder, leafer, harmon, and springer. don't beleive me as irish rich, bill holland, sugar bear, arlen ness, gary , and countless others. some just need to understand that different rakes, different forks, and different frames take some getting used to. So that is just my take on stuff.

I agree with Krymis on this one. Rake angle has nothing to do with now agile or nimble a bike handles, just increases the overall turning radius since the wheelbase is longer. If the trail and flop factor are set identical a 45-degree bike handles exactly the same as a 30-degree bike on the curves. The long bike handling myth came about becasue of poorly designed bikesand forks but nowadays most chopper forks are built to more realistic specifications.

I agree to a point, it really just depends on what you are comfortable riding and what you like best i guess. I have ridden a couple long raked out bikes, they are real cool but i am not really used to them. I have mostly ridden bikes with stock rakes 36 degrees and under, i guess i need to ride some more long raked out bikes to develope a good feel for them.

jonester,

i was in the same boat. then something gary said resonated with me...most people don't know what a good handling bike is. What is good to me is poor to you and vice versa. I have since been willing to do all the math and experiment on every bike i have owned. if the #'s are in and i can be on then I am good and the bike feels like power steering when you can play with the weight of the bike in reference to the axle location.

One of the best books ever published on motorcycle geometry was done by a fellow name Phil Irving. It was called 'motorcycle engineering' and was first published way back in 1959 and later revised and published by Clymer in 1961. Irving designed some of the most radical and winning high performance motorcycles ever to see pavement and even today his engineering is considered to be state of the art and his work is the basic text book for cycle designers today. As far as I am aware he was the first person to challenge the old myths about rake angles and to design some high performance Springers and Girders. Harley used him to design their so-called 'modernized' Springers and later glide front-ends. Irving is best known for designing the Vincents but he considered those bikes to be rather 'conservative', aimed at what he called 'gentryfied' folks. His more radical designs dominated gran prix racing for decades and many of his designs were eventually outlawed since the rule makers felt that other competitors were at an unfiar disadvantage. His racing girders are still used today.

krymis wrote: ...the bike feels like power steering when you can play with the weight of the bike in reference to the axle location.

Is that using the same trail value or are you altering trail as you play with axle location?

Not speaking for Krymis here but you can maintain the same trail values and still use what I call 'dropped' rockers like the Sugar Bear versions and reduce flop significantly which gives the rider the 'impression' of having power steering since a small movement of the handlebars produces a realtively large displacement of the front wheel. This is one reason people have a hard time adjusting to riding with a Sugar Bear Springer.

gww25 wrote:Not speaking for Krymis here but you can maintain the same trail values and still use what I call 'dropped' rockers like the Sugar Bear versions and reduce flop significantly which gives the rider the 'impression' of having power steering since a small movement of the handlebars produces a realtively large displacement of the front wheel. This is one reason people have a hard time adjusting to riding with a Sugar Bear Springer.

gary is right on on the reasoning. the higher the axle is above that rear rocker bolt the lighter the overall bike feels. also the wheel can only turn so far before it reaches it's "terminal angle of rotation"(that's my new copyright sentence so no taking it gary). so there is no need for the fork stops due to the dropped rocker not allowing for flop. I have honestly expanded on gary's rude crude springer build article to about take up a full 1" thick 3 ring binder. just that one article. sugar bear does nothing special as far as rake and trail. it just looks that way with the scimitar rockers and the offset trees. The one big secret i found has been brought to gary's attention and so on. frames and frontends are seriously my life's work. for the past 10 years it is all i have worked on and gary has been at the forefront of helping me understand why and what for the physics of building. anything you want to know ask. rudog can verify i will not hold out or hold back. this should be common knowledge to elevate the home building to a professional level and beyond.

Sorry to all...I'm not buyin' it!!!

If the x/y/z relationship of the axle to the steering neck is fixed, the shape of the forks can have no effect on how the front tire moves when the steering axis is rotated. There's an unknown quantity that I need to know.

If the rocker pivot is dropped below the axle, that would mean that the rocker is angled upward. This would limit minimum trail to normal ride height, any motion would increase trail. Maybe something???

rudog wrote:Sorry to all...I'm not buyin' it!!!

If the x/y/z relationship of the axle to the steering neck is fixed, the shape of the forks can have no effect on how the front tire moves when the steering axis is rotated. There's an unknown quantity that I need to know.

If the rocker pivot is dropped below the axle, that would mean that the rocker is angled upward. This would limit minimum trail to normal ride height, any motion would increase trail. Maybe something???

thew axle is not the gyroscopic rotational axis. the contact patch of the front tire is. the axle comes into the picture as that is the connection between the wheel/tire combo and the steering axis. Not only do you need to look at that aspect you also need to take into account the perceived weight of bike being on the axle in one aspect and the lighter feel of the weight being moved under the axle and forward (moved rather from the horizontal 0 centerline to below that and towards the vertical 0 centerline.

I do believe that i may need to do a video on how I build and how two different frontends react even though they have similar numbers.

krymis wrote: thew axle is not the gyroscopic rotational axis. the contact patch of the front tire is. ...

Explain this...please!