Looking for knowledge of front forks rakes

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joedrum

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I’m sure in racing this has the be a big part n setting up a bike to run strait ..not really looking for that but to make it wobble less ......Been looking to do something better ..when it happens the forks seems to strait up and down ...just looking for opinions of rake versus wheelbase...thanks
 
This site has a good calculator and some good info on rake and trail. Trail is the thing GLs are marginal, but still OK on. It's also the reason the Kaw 3s killed so many. They ran marginal trail due to a steep rake angle. When you backed off and the forks sagged, rake angle decreased and the trail got way to little. Sportbikes get away with steep rake for quick steering by having stabilizers to tune the oscillations out. https://www.rbracing-rsr.com/rakeandtrail.html
 
Jones' point shouldn't be taken too lightly-

It's not so much the rake and trail figure that you measure when it's sitting still... it's the dynamics that CHANGE when you're riding.

IF you ever happen to have a front-end oscillation start, lean forward... get more weight on the front wheel... the oscillation will usually settle out... but downforce from wind on a fairing, or many other things... will have a substantial impact on handling.

Having spring problems on the front end... particularly... one fork tube that has a weak spring, or having just enough malignment in the tubes so that one slider binds at some point... or having improper damping oil or levels in one or both... will cause stability problems, as will a sloppy swingarm bushing...

And the most overlooked, is well-worn tires. If either of your tires have worn to exhibit a flat tread profile rather than rounded, it will get really touchy, particularly in curves.

When braking, having assymetrical load on the fork sliders will cause both steering stability and wear problems. Why? Because brake caliper force is twisting on ONE slider, but not the other. This is one of my greatest pet-peeves of 'integrated' braking... two front calipers that are NOT working together. My '79 CX500D had adequate fork tubes until I fitted the Pacifico fairing. it got a whole lot more stable at highway speeds, but more substantial springs and damping was clearly needed. I replaced the CX triple-trees and forks with GL-1000 units. I snipped off about 4" of the GL spring, and installed a sliding puck and 6" of CX500D spring, so that the spring rate at rebound would be a good match for the lighter bike. I ran 7wt fork oil, and of course, fitted it with a CB900 front master cyl and a second CX500 caliper, and the end result was a WHOLE lot better than the original setup in just about every way.

That being said, I'm not certain what front end parts combinations would improve a GL-series, but I'm certain there's room for it somewhere.
 
Ok there are options out there to put sportbike front end on a Goldwing seems the GSXR Suzuki front ends have the most aftermarket parts to do this switch but complete front ends are very expensive and the cost involved makes this a very expensive modification it would be nice to have the front brakes of a sportbike on an old wing so it looks like I'm going to have to keep looking at options for my bike I'm not saying that the old Wing front ends are bad but they are on my bike with the shaft drive like it has and also the power and torque it has it just moves the bike around starting all the time problems it seems it doesn't matter if the if you are traveling on the throttle or coming off the throttle the bike shifts quite a bit it is pretty neat all the stuff that is out there to accomplish a front end swap I'd like to do it but that's the moment I'm not going to be able to and I'll keep looking for options and keep looking for parts to get this done
 
I will look into that ..but I’m thinking that’s all good ...my custom fit 1200 swingarm adjusts front and back ...at pivots and axle ...I’d like to have spring caps that threaded on and also the same diameter tube for a inch or so to raise the forks ?
 
Raising front will increase rake angle and trail. Lowering the back will do similar. I've seen screw-in extenders. You could also try adding ~1" plugs on top of the springs to stiffen and raise it some.
 
Look ata great build thread at NGW ...one of the few threads there. That non members can see. Pics ...bike was heavily raked ...I also found that there is no screw in fork extensions for oldwing forks ...seems Harley’s are the only ones made today for sale...also found a place called franks fork tubes ..he actually has 37mm tubes for sale ..most places carry 41mm and 35mm tubes only ...so options are not many ...my likes are that I really like the simple gl1000 forks ..
 
Ok I had to try it ...I lowered the forks down a good 11/16th of an inch to see if it would make a difference ....it did for the better ...so I’m convinced this is the move to make ...either new longer tubes or custom screw in extensions ....plus a fork brace that actually works like the older ones that really had strength to them ....
 
My Oldwing when I rebuilt the forks I damn near cut a third off them and added spaces to raise it up to stock height. On the Blackbird I actually raise the rear up about an inch to decrease its rake. However the number one thing I know from my ex500's is using a string to align them. Running a string across the rear tire up to the front and measuring the distance from the string to each side of the front tire will tell you if #1 if the rear tire trails directly behind the front and you will defiantly see if your fork tubes are twisted in the triple tree. However like Jones says, to sum it up, all the geometry needs to be taken into account. Alignment is the largest issue AND these wings have floppy, soft steel frames that gives at speed. I would defiantly diagnose and confirm alignment before you go into modifying.
 
Hey Ἀφροδίτη !!! Good to see you back around!

I had excellent results on my last V Max dropping the tail about an inch and a half. It responded very well to increased rake. Pretty much eliminated a nasty head shake.
 
For the basics, have you tried searching for "bicycle geometry"? They are both two-wheeled vehicles, and while bicycles travel slower, they are arguably more sensitive, being powered by a Mark I human being, with limited power output. Rake, trail, and wheel base act similarly to a motorcycle.

Before making changes, I'd search for how it applies to motorcycles, but the basics are there.
 
I'm trying to follow this because I have dealt with head shake on several bikes, and I'd like to help.
1. Joe, what are the symptoms you are experiencing?
2. Are you looking for 37mm fork tubes of a minimum length? My 82 cb650sc has nice long 37mm forks that I'm tempted to shorten.
3. The different reasons or cures for headshake I have dealt with in the past included: loose head bearings, worn front tire, low air pressure in front tire, and the wildest one is... Honda mounted the front rim on cb750's 4mm off center to allow racers room to install a second front brake. The cure for this one was to adjust the spokes 4mm to bring the rim back on center. The full story of this can be found in Mark Paris's book "My CB750 Book" by Lulu Press.
My current headshake issue is with the Harley Wide Glide front on the trike with too much rake. During extreme braking it would give a little wiggle. Turning the damping back up on the already included steering damper seems to have taken care of it. I also try to avoid situations the require extreme braking! (Now that I can stop the darn thing with the new disc brakes) But now I'm rambling....I'll stop.
 
Symptoms are it seems my bike can deliver forces on the frame of bike and forks more than the capabilities they can handle ...yes it’s time for a new front tire ...yes air pressure has to be maintained...and if I ride normal bike seems really ok ...but any way you look at it in a oldwing the motor is part of the frame ....the removable frame piece is proof of that ...on my bike if you rev the motor out of gear it will rock the whole bike and that’s just the motor running ...this same thing transferred through the driveline to the wheel under full throttle seems to bring in more than the bike can handle safely ....to me longer tubes would help some to a point as it seems the bike when it wobbles is running over itself ..let me just say that powerful oldwing and it’s shaft drive can bring in forces that are not inline of the bikes down road direction to the point of wobble is introduced
 

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