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Another raked yokes post - DIY

I am mulling over reducing trail via the yokes, and have no choice but to machine my own.  

If I understand the confusing terminology, "raked" yokes pull the wheel rearward.  Am I correct in that this is done by changing the angle of the fork tube bore in the yokes?  

One could also reduce trail by increasing the yoke offset.  Not my preferred solution as it would need to go from 1.26 to 3.25".  

 

Once on the mill anyway, it is easy and clean to bore a fork tube angle in the yokes at 4 degrees = 2.09" of trail, while leaving the yoke offset stock. 

Stock trail is 4.17" so quite a bit less trail then stock, and I am hoping a sufficient reduction for our winding mountain roads and no freeway use.

I may incorporate race bike style, +/- stem offset bushings so that I can fine tune trail without having to make new yokes.  Finite adjustment only, but not that much more work - the problem is installing them properly so not for the inexperienced

 

A handy calculator:

https://www.rbracing-rsr.com/rakeandtrail.html

 

"If I understand the confusing terminology, "raked" yokes pull the wheel rearward."  No, when you rake the yokes the wheel moves forward,  away from the bike, thereby reducing the trail.

 

The drawing you posted is misleading in that the downward slant angle line is normally parallel to the angle of the forks. The line shown in the drawing is if you changed the angle of the steering head. In that case the line is correct and you moved the wheel forward thus reducing the trail. 

I posted only the after drawing.  Here is the before drawing from Liberty Sidecars I did not post:

 

So the red line is running through the yoke stem axis and not the fork leg?  If I now have it correct, "Raking" the yokes moves the wheel forward while maintaining the same stem geometry.

The method therefore must be boring the fork holes in the yokes at an angle - 4 degrees in my case

 

My first sidecar, and it is no wonder I am confused.............Thanks for setting me straight

 You've got it now.  The stem geometry stays the same, the angle of the fork bore changes, moving the front wheel forward thus reducing trail.

 

 

robert straghan has reacted to this post.
robert straghan

I am only as smart as my internet connection.  Is there an ideal number for trail?  

Once I have this on the mill, the angle can be anything within reason, but I would like to do it right the first time.  I see 2" mentioned in several places but that seems to vary +/- 1/2" depending on application and experience.  My stock trail is 4.17" (106mm) so going to 2.09"with 4 degree yokes is a big trail reduction

My conditions are mountain roads in Thailand, so sometimes a bit bumpy.  No freeway use and probably no more than 110 kph on the straights.  A new sidecar rider, and still trying to learn, so no twitchy steering required.

Bike is a Royal Enfield 650 Interceptor with a Cozy sidecar

  I have experience with  adjustable yokes on road race bikes, whereby the stem angle is adjusted using offset bushings.  Easy at first glance, but a bit fiddly to install and align properly.    As you might imagine, the amount of change is small, but good for fine tuning.  Is this not used in the sidecar world?

 

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My 2 cents "do nothing"  It's a small bike with a small light sidecar.  keep it simple sidecatist.

Dave

smitty901 has reacted to this post.
smitty901

What Dave said ^.

The primary - maybe only - reason to reduce trail is to reduce steering effort. With a light bike and car you may be just fine as built. Ride it for a while and see if you really need to modify the rig.

Duncan

smitty901 has reacted to this post.
smitty901
2011 R1200GS + EML CT2001

 Have to agree on leave it as is try it mostly a lot of wasted effort

 

Quote from Dave Skudlarek on October 16, 2021, 7:50 am

My 2 cents "do nothing"  It's a small bike with a small light sidecar.  keep it simple sidecatist.

Dave

The adjustable was used by some Harley was one.  They gave up on it.

My 1996 FB 1380cc needed no front end work, Nor did my 2015 750 Harley. The 2020 RGL is ok with no rake but rake would light steering effort some as it did on the 2017.

One more "leave it alone" vote.  You can always change it later if you want.  remember that reducing the trail reduces the steering effort but it also make the steering more "twitchy" and if you're not used to sidecars that won't be an advantage at the start.  When solo riders try my K1100LT/EML rig they all complain that the steering doesn't feel stable.  Experienced sidecar drivers understand and don't worry about it.

 

A

Thanks for the input and will ride it a bit more.  Our roads are twisty at times with lots of switchbacks and I am not a big guy, so  a bit lighter steering would be nice.  A bit lighter is why I was asking about the ideal trail spec on a light bike, with no freeway use

There is a secondary reason for different yokes.  I am currently fitting a larger rotor and 4 pot Brembo calliper to the front and need clearance at the wheel spokes.  I have the calliper fitted now using a rotor spacer and a bit of machine work, but wider yokes would make it a lot simpler and essentially a bolt on mod.  

 

 

 

The adjustable was used by some Harley was one.  They gave up on it.

The track bike method I am talking about is more like using offset bearing cups, than the HD adjustable trees.  Common in Moto GP and Superbike classes, and OEM on some Ducati models.  Rather than an offset bearing, the  yoke stem hole is over bored and an eccentric bushing is used.  

[​IMG]

Robert,

Take a look at this link...

https://www.lumleyengineering.co.uk/page_41.php?pgenme=bespoke-leading-link-forks

Scroll down to the unpainted picture.  It give a good idea about how this is done.  Note that it is possible to add some adjustment to this by making multiple mounting holes or adding clamps.  

Here's a cheaper solution

https://www.adventureridingnz.co.nz/forums/topic/reducing-trail-leading-legs/

Note that the reason for a leading link suspension is not just to reduce trail.  Telescoping suspensions are built to accept load from only one direction.  They are suboptimal when it comes to side loads.  That's not an issue for motorcycles but a real issue for sidecars.  Leading legs don't help here at all

I like the retro bike look of a stock front end with the Zeppelin chair, but have been thinking about both those alternatives.  If I go that route, it would be leading link, however I am going to have to learn about shock geometry and rates - the rest of the design seems easy enough.  Wasp has a nice adjustable design, but with Thai import costs I have to build it myself or cost doubles.  No issues with bigger brakes with a leading link, however my spoked wheels are not ideal for side load.  Interesting that Lumley LL examples show wire wheels?

New yokes simplifies machine work for  my 4 pot calliper clearance problem, and is a lot easier to design and build (for me at least) than a leading leg.  If one did not have a mill or get mates rates, then I can see how a leading leg would be cost advantagous, with a similar result as yokes.

Current thought is to ride it a bit more, and think a lot more.  

 

Robert,

I've been running spoked wheels on a BMW/2 rig for many years.  Two important things to note...

  1. This is NOT a high performance sidecar rig, I have a BMW K-bike based rig for long distance and higher speeds.  I use the /2 for putting around town and rarely go faster than 60mph.
  2. The wheels are laced with heavier than stock spokes.
  3. OK, three things... Most spoked wheel failures appear to occur with wheels using alloy rims.  If you are going with spokes, use steel rims.

A

Quote from Al Olme on October 18, 2021, 10:45 am

Robert,

I've been running spoked wheels on a BMW/2 rig for many years.  Two important things to note...

  1. This is NOT a high performance sidecar rig, I have a BMW K-bike based rig for long distance and higher speeds.  I use the /2 for putting around town and rarely go faster than 60mph.
  2. The wheels are laced with heavier than stock spokes.
  3. OK, three things... Most spoked wheel failures appear to occur with wheels using alloy rims.  If you are going with spokes, use steel rims.

A

I too am not a performance application, and even if so, do not have the experience.

Naturally I have 3 nice, lightweight, Excel aluminium rims.....................I will buy some heavy gauge, tapered,  SS spokes from Buchannans in the US .  Presumably bike only?

 

Thanks for all the help

Robert, I have no appreciable machining skills/knowledge, but we have installed modified trees on three motorcycles, including a 5° on a 2002 XL883R Sportster, with excellent results.  As I recall, the resulting trail on the Sportster was was ±1½-2 inches.

Lee / Summer Grove, Louisiana: Ural cT, CJ750, Burgman/Texas Ranger, Zuma 50F, MB5, TW200, CRF250L, GTV300

Maybe I am especially weak, but I found the steering effort on the Royal Enfield 350 in the sidecar class to be a lot more than comfortable. Same with my '79 Sportster. I have 5 deg offset trees ordered, hoping for the kind of results as SwampFox.

Just saw this post so apologize for being late.  I’m not comprehending how it’s possible to simply re-bore stock trees at a new angle. Maybe I’m not understanding what Robert is saying?  IDK.

The problem with humanity is: we have paleolithic emotions; medieval institutions; and God-like technology.

I have a 2011 Roadglide Ultra with a Motorvation Formula II sidecar that was mounted by the Motorvation Engineering Company before the business went under.  It steered heavier than I wanted, so I bought a set of raked triple trees from this company:

http://www.cutnshootcustoms.com/rake-kits-1.html

Great communication, free shipping, they cover sales tax!

It made so much difference on my bike that my neighbor who has a 2014 Ultra Classic Limited with a Motorvation Roadster sidecar asked me to install a set on his bike after driving my rig.  Both installs were not difficult if you are a mechanically minded person.

USCA Member and Minnesota State Representative