FXDX Suspension Tuning.

[speedzter]

Own 1.. Got 47K on it.. Best handing bike I've got.. Still has the stock forks (though they've been modified) and the original rears. High speed sweepers are not problem. It's got some chassis googaas but they didn't do much and are still on there for looks.. 
Max

Max I know you have experience with the FXDX, I was aiming at the other guy with his magic 49mm forks.
I've had a large diet of Jap' sports bikes in between HD's, and my 2000 FXDX still gives me a huge grin !!

I'm running a Deuce rear wheel, True Tracks and a front fork brace but otherwise stock.
I can't understand why you guys don't agree that the suspension links (True Track etc') aren't a positive thing.
They actually connect the drive train (motor/swingarm) positively to the frame.
How can you expect only a top link and two bottom rubbers to be stable ?
The input from the rear wheel HAS to cause it to deviate from the front wheel ??
The extra links allow the motor to move in the vertical plane but stay central otherwise.

My bike was stable up until around 85mph, but with the True Tracks, it is good to over 120.

[HogMike]

It's fun to see what you are trying to achieve with your bike, and probably MORE fun to actually do the engineering and installation of said parts to get what you want.
I have done many projects in the past trying to make my bikes "keep up" with other brands either in cosmetics or function.
Although I had fun with my projects the reality was I was never going to get there, not even counting the $$ involved.
That being said, they were always "fun" projects and much the topic of bench racing.
I changed my direction to "restoration" later on, and had a good time doing that for many years.
Different strokes.....etc......
Have fun doing what you're doing......interesting stuff.

[Hybredhog]

  I'll take a shot at trying answer your questions, but as you said, your never going to hit the target with a stock frame. Correct me if I'm off a degree or so, but Dyna frames come in 28 deg. (DX & SG models) & 32 deg. (WG & LR), With the 28 deg. being our focus. Now most all of your target bikes (Ducati Monster being my favorite), have appox. a 24 deg.? The quick & dirty way there is adjustable trees, AKA flat track adjustable neck cups. Now off the top of my head I don't know who makes them, but they have articulated various cups for set up, this may get you to where you want to be? That being said, raises the front, & will allow for a smaller front 17" wheel to equal out the height. As for a "stock" FXDX cartridge fork, Bang for the buck it ain't bad with a little tuning help, But if money is no object , cough for an Ohlin inverted fork. The stock rear DX shocks are junk in my opinion, and mine leaked inside of 10k, not to mention were way to soft spring wise out of the gate, so theres your other call to Ohlin.
     I know there are some Aluminum swing arms out there, big buxs, & possibly worth it, But I'd almost be willing to try some underside gusset work to see if that's where you'd want to go? As for wheels, You couldn't give me a set of spoke wheels, just to many pitfalls to make up for the unsprung weight, there are light billet wheels that can answer that better. What I did find out when I put a Duece rear wheel on my racer ('99FXDL), was that it was 2+ lbs. lighter than the stock cast. Gas tanks are going to drive you crazy, if quasi stock capacity is the target, An equivalent Alum. one is not going save much wieght (other than lighten your wallet), if any, and probably eventually fracture anyways.

[HogMike]

BTW: just did the math on my 2010-103 bagger on $$ spent to get to 129MPH.
$1500.


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[build it]

Wow, what a fing warm reception, I think I might even shed a tear . Thank you. You guys have given me more to think about than I anticipated, I have nothing to contribute at this point, but when I figure out what route I'm going with the suspension I'll post up in this thread, hopefully with some pictures. My aim is to go as far as I can, one step further than a perceived "discernable/measurable difference" would be just about right.

[CowboyTutt]

Build It, I just got back from having a long conversation with my friend "Dan Dan the Harley Man" at Harley Davidson of Ukiah.  He really is an entertaining fellow, I have to say!  I think the information I have will address previous questions directed at me and help you with your project as well. 

The story is when Harley first told their dealers about the new 2006 Dyna being "new and improved" nobody believed them.  The response was more of a "Yeah, sure".  So Harley put together a very expensive track school/event and rented out the Las Vegas Motor Speedway for 3 days and invited dealers to come.  They also hired Freddie Spencer to teach those who were capable how to get around the track as fast as possible.  Harley engineers were present as well as specimens of all the earlier generation FXRs.  There were displays and demonstrations by the engineering team using cut up Dyna frames from all generations including the new 2006 version frames and swing arms so Harley could show their dealers conclusively how "new and improved" the 2006 Dyna chassis was.  My friend Dan was personally there at this event.   

Harley Davidson engineers realized as performance demands increased on the Dyna line that the FXR chassis limitations were becoming evident.  The thin wall, small diameter fork tubes (sometimes called "Sportster Tubes") were one area of weakness as well as the triple clamps as I referenced above.  Another major area of weakness was the steering neck.  Lastly was the rear swing arm.  So Harley engineers focused their efforts in 3 areas: 1) Forks  2) Steering neck and 3) Swing arm. 

Once the presentations were done at the event then all generations and versions of previous Dyna's were flogged around the race track under guidance from Freddie Spencer for those capable of it.  Freddie would direct people in speed, line of turn and brake points so people could first hand experience the instabilities when flex in both ends of earlier Dyna's would cause oscillations and "Golly Wobbles" as Dan called them that were pretty scary.  Then the new 06 Dyna's were brought out and they were clearly superior on the track under the same conditions.  Dan's personal experience was that the older Dyna's were 8-10 mph slower on the race track because of too much flex front and rear. 

So some of the improvements that were made to the 06 Dyna chassis was the change to 49mm forks and stiffer triple clamps that were 30% stronger.  The steering neck became a 3 piece assembly that was "capped" and 15-20% stronger.   The swing arm was also stiffened by increasing side wall thickness and triangulating it although you really need to cut it apart to appreciate it (I was able to compare both a pre-06 design and the current ones as we had a used Dyna present).  Even the rubber engine mounts  and axle sizes were changed in 06.  What the Harley engineers reportedly did was to measure flex between the steering neck and the rear axle.  They somehow put a rod horizontally through the rear axle and one vertical through the steering neck and twisted and measured force and flex.  The new frame flexed  a whopping 1/3 less than the older ones. 

Dan said the engineers were sometimes "geeky" and needed to simplify their language so those present at the event could understand them but they seemed quite proud of all the frames they destroyed in their research and new frame development. 

Dan said people won't be able to easily verify any of this because it was a "Harley School" and the general public was not invited.  But my friend Dan was there and many others as well.  There was once a whole "cottage industry" that existed to address the weak rear swing arm of Harley Dynas.  It was not a big secret, just common knowledge at the time. 

So Build It, Dan said one of the sharper fixes on the earlier frames was to weld the steering neck in some way.  Then of course address the swing arm and front forks.  I wish you could have been there this morning.  Dan would make a cool You Tube video!  Instead I just stood there, asked questions and took notes as best as I could! 

Hope this helps my friend. 

-Tutt     

[CowboyTutt]

By the way, the older Dyna's have 4.1 inches of trail according to the 2005 Harley Dealer book that lists all the specifications that I looked at today.  My personal ride has similar rake to the FXDXs at about 27.5 but we measured my trail at 3.25 inches  with the longer shocks if I remember right.  It ain't magic guys, just physics and engineering. 
-Tutt 

[Hilly13]

I currently and I hope till the end own and ride an 06 dyna, stock was it better in handling to my 01 FXDX? the truthful answer no it was not, yes its frame is superior in design for all the reasons Tutt has put forward, but the standard rear shocks and front fork valving were inferior to the FXDX, with both ends addressed and in my case that was gold valve emulators and better springs in the front and very expensive French made shocks on the rear the bike was able to show it had an improved frame, but, and it is a big but, the rubber mounted engine with its swingarm swinging off it causes issues in fast bumpy cornering just like the FXDX, truetrak front and rear helped tremendously in this area, Speedzter is exactly right in his assessment IMO, having said all that if I was to go again at suspension I would use Howard's front fork cartridges and his shocks set up for my weight and the trutrak to keep it real. Hope that is of some help to someone as it took forever to type.

[CowboyTutt]

Thanks Hilly.  I've not heard of the true track stuff before for Dyna's.  I'm going to look into that.  Keep on typin'!  -Tutt 

[CowboyTutt]

Looks like the front TT won't work with my Jagg 10 row down there.  Might be worth doing the rear one only though.  -Tutt 

[sharkoilfield]

Before I "waste" more money on upgraded suspension on my FXDXT, I'd like to pursue every weight loss possible. These bikes are "Hogs" in more ways than one...just put in a lithium battery (-10 pounds and more starting power) and weighed an aluminum tank and my stock tank; that could be another 10 pounds lost...a belt primary would also take off significant poundage but present other issues...but if I go much further then the bike is no longer as versatile in my mind ie: unsutable for long range touring...now as I'm stuck with it for ever; I need to get another bike for touring and carry on with making my ideal Harley...there's some good discussion on this thread...how about some more weight loss ideas? 

Anyone make an aluminum tank to fit a stock Dyna frame???

[Hybredhog]

  First off, an empty stock Dyna tank doesn't weigh 10 lbs to start with. I don't know of an Aluminum tank in production for them, but if it did exist, it'd cost $1000+ , and would be somewhat fragile when loaded with 4+ gallons of fuel. Belt primarys may save some weight, but a chain is peace of mind.  Wheels are probably the best bang for the buck in weight savings, but it does come down to $$ and how much you can play.

[Hybredhog]

   Here is a pix of my racer with the new 17" R6 wheel with HD brembo calipers, works great! It wasn't all that bad to make work, just figure out Bearing sizes & turn out a new axel & spacing. Fender fitment is a PIA , as HD mounting lugs are different & forks are rather norrow compared to the rest of the world, so no direct crossovers.

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[CowboyTutt]

Jeff, that is way cool.  Do you have a picture of the whole bike I can look at?  -Tutt 

[CowboyTutt]

I found these new wire wheels from Performance Machine that I'm drooling over.  Many sizes available.  They would be lighter than the stock wire wheels I have but still strong and retro looking.  I'm into the keeping the traditional Bobber look on my bike though.  I suspect that lighter aluminum hoop would reduce the gyroscopic effect of the stock 19" steel rim and ease turning at higher speeds.  BTW, one of the most cost effective improvements is putting good sport-touring rubber on a Dyna. 

http://www.performancemachine.com/motorcycle-wire-spoke-wheels.html

-Tutt

[sharkoilfield]

jeffscycle: I weighed my stock tank when it was off and it was 15lbs on my luggage scale; I found an aluminum tank (Arlen Ness NOS) and the vendor weighed it at 5lbs. I'm sure the Ness Tank would hold fuel for a while...

[Hybredhog]

 

jeffscycle: I weighed my stock tank when it was off and it was 15lbs on my luggage scale;


   Sorry Dude, youe scale is WAY off, I just grabbed a stripped dyna tank, 5 lbs.

[Hybredhog]

  The bike is stripped right now undergoing the endless work it takes to get ready for Bonni. The pic I put up is with stock size wheels & NO front brake. In my class I can do that for aerodynamic reasons, but I'm playing at 150+, and slowing down takes awhile without over heating the rear brake, Not to mention the PUCKER FACTOR! So thats why I'm installing a front now. odds are it won't interfear to much.

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[CowboyTutt]

NICE RIDE!!!!!  Me Likey!   

I have a friend here named Steve Burns who races a bright yellow Suzuki GS1100 at Bonnie every year.  Hard to miss his bike too with the two big yellow snorkels pointed out front.   

-Tutt 

[build it]

An observation re: the TT front and rear pieces. Not taking shots at anyone, nor do I have a structural load analysis done by an engineer, but, the stabilizers aren't exactly precision pieces. After watching one of the install videos I have a hard time believing that the load between mounting points is distributed evenly. In that video the "voice" says to pay attention to the pull of the bike, and tire wear. The mentality is if it pulls this way a "little" then a "little" "less" or "more" in the other direction will fix it. 

Real race bikes, rather, bikes that people generally accept as race bikes would never use the "little of this little of that" approach. Factory riders routinely will ask for 2-5mm more or less trail, or 5-10mm longer or shorter swingarms; go the wrong way and they notice it. I don't think anyone would notice 2mm more trail, not with the inherent limitations of a Harley. The bike, any bike, but particularly Harleys, can have misalignment from the factory. An off the showroom floor motorcycle can have "2/10ths" of misalignment.

If this FXDX doesn't work out and the down tubes can't handle it, or any part of the frame fails, that day I'll order a rolling thunder 2" tube FXR for an A motor if the motor mounts the same as my current bike, if not, I'll order a 2" dyna frame. The suspension pieces, well most of them, would be easily adaptable to another bike. 

I didn't get a chance to call Kent at GMD back this week; it's been pretty chaotic around here especially with the holiday. I'll give him a call this week and work out the details and report back.

Jeff, a 150+mph is a hellish mistress, I'm green with envy. Can you share any details regarding the engine? If not that is totally understandable. Sustained RPM in a Harley is no small feat. Also, thanks for the weight measurement of the tank; I can check that off the list for sure.

One thing I find amazing is how much Italian or Japanese bikes veil rider flaws; Harleys are just about the most unforgiving bikes I've ridden.

Anyone read that early 90s article by Hunter S. Thompson? He didn't want to test ride a Harley he wanted a 916 because no Harley could ever hold up to a proper pedigreed sport bike. They sent him a sport touring bike instead and he wrote glowingly about how "horror show" the bike was to ride. At 12 or 13, that article captured what I wanted to experience through riding, but on a Harley. A well off Uncle spent 15 or so years after that, ragging me because I wanted a Harley; he did this by giving me nearly free reign over a stable most guys could only dream of. I've ridden/driven everything I could ever care to ride/drive except a Britten and that stupid jet engine bike.

Good luck guys, when I have something worth sharing I'll post up, thanks for keeping my wheels turning.

[CowboyTutt]

Hi Build It.  I've been confused myself from the conflicting information.  It sounds like some have really benefited from the TT system on earlier Dyna's including an 06 version.  I've been looking into the the TT systems and the Sputhe Positrac but to be honest I've just not experienced the symptoms people are talking about with my 09 Dyna.  I've had it up to 110 more than once even with a huge transversely mounted duffle bag on my quick detach rear platform and still no "wolly gobbles".  The bike tracks as true through the turns as well as any twin rear shock bike I have ever had.  I thought I would break out my 09 service manual and examine the engine mounting system.  Check it out: 



The rear isolator (Part #8) appears to be mounted into a steel bracket between the rear downtubes with 2 bolts going through it longitudinally.  Same with the front mount (Part number 4).  There is a stabilizer link (part #18) on the top. 

The frame tubes are tied together from gusseting at the rear isolator, underneath, across the front islolator, behind the voltage regulator, and behind the capped steering head with a triangular gusset.  In fact the whole steering head area and the fully boxed back bone looks massive. 

The whole set-up looks pretty robust to me?  Could this be different some how from an 06?

I think I will pass on the TT's for now.  But an Ohlins steering damper might be nice....

-Tutt 

[FLTRI]

This will help will the unsprung weight diet:
http://www.blackstonetek.com/wheel_gallery.html
Bob

[Hilly13]

Each to his own as they say, the trutrak let's the engine rock foward and backward, it limits sideways movement, I can tell the difference, in fact I have one particular corner that gives the suspension a work out, before and after fitment attacks on this corner tell me for sure that it works at least to some degree as both entry and carry speeds are higher now and it dosnt get the wobbles, just scrapes the lower muffler. Roads around here are crap though so it might just be horses for courses.

[CowboyTutt]

Bob, thanks so much for the link!  I'm very interested and I book marked that for later. 

Hilly, maybe you are right.  We have rough roads around here too but I have found having a supple suspension tuned in conjunction with your tires makes up for a lot of that.  I'm lucky to have some race guys around here to help me with the tuning part.  I put zip ties around the fork tubes and go out riding hard over the same stretch of road to measure how much of my available travel I'm using.  The back I just keep adjusting on the same day, over the same stretch of road (since my Ohlins are fully adjustable and I admit that few have that ability) until they are becoming too soft, then stiffen them back up. 

I can usually run in the top third of my riding group even when riding with Buells on my porky Dyna.  Sometimes even better depending on the roads.  I'm just not sure the TT's would offer much improvement. 

Not trying to slam them, just sayin' that for me personally I'm not sure they would help that much. I will try to go by my dealership this week and look at the 06 service manual to see if there is any difference between an 06 and a 09 frame just in case.  If I do, I'll take a picture and report back.   

Thanks for posting and I appreciate what you have to say since you have owned both a pre-06 and an 06 Dyna.  I truly do.  Feel free to keep typing my friend.  I will pay attention.   

Regards,

-Tutt 

[build it]

I would've already comitted to c/f wheels if I hadn't listened to several horror stories on the West coast about them coming undone. This was about 7 or 8 years ago.