Help me stop my Catrike Shimmy!

[John Rooker]

This is an area where I have some problems with the way the company handled this and I know there are others here who share those problems.  If I recall correctly, the original Expediton came with Big Apples on it.  When was that? 2006?  Sometime late in 2007, the gusset was added and a change in geometry took place.  If you read Larry Varney's reviews of the two Expeditions he had, he made reference to the heavier steering of the 08 vs his previous Expe.  David bought Larry's 08.  If it wasn't for daily reading of BROL (Thanks, Bryan), I would have never know of the change in the Expedition.  My dealer, who is a Gold Dealer, didn't even know. 

I don't want this thread to degrade into Big Cat bashing so let's be careful here, but I think we have a bad Expedition here.  Maybe we can help get rid of the shimmy..I hope.

[legrandfromage]

My frame doesn't have a gusset, but it does have a geometry change. The earliest Exps had black kingpins, and a geometry identical to the 16" trikes - which did not work. They changed the geometry quietly (the changed trikes have silver kingpins) and later added a gusset and said something about a geometry change.

[devious56]

I don't think I can contribute much more to this conversation, and I'm like John, I don't want to get into a Catrike bashing situation.  I have strong feelings about the shimmy problem and what should be done with it.

The early Expeditions were notorious for shimmy problems from what I've seen in my short term dealings with Catrike.  When a product is as dangerious as some of the Expedtions have proven to be, they should be replaced.

Talk to Catrike and see what they can do..................  and good luck.

David

[John Rooker]

From what I've been seeing and reading, the 09 Expedition is pretty well sorted out. 

I can pretty much echo what David just posted. 

Try everything listed here and if it doesn't remedy the situation, give Big Cat an honest chance to try to come with a solution. 

[throttle 8]

I have a relatively new X-Po (Orange Crate #922) and I have no shimmy problems what so ever!  I'm 245 lbs. and have the hybrid headsets (bearings on bottom-bushings on top). The thing handles like a dream.  I'm running Primo Comet's all the way around.  They are all 1.5's (on the recommendation of David) and give a decemt ride.  I think if you install the bushings and tighten them just enough to take the play out and then 1/4 turn more, your shimmy problem will disappear.....hopefully

[TrikerTom]

Centerpoint steering is not the be all and end all of shimmy.  I have an Actionbent that doesn't have centerpoint steering but exhibits no shimmy or bump steer.  I did, however, put in some significant effort in ackerman compensation.  These trikes came without any compensation... seriously!  I developed a kit to deal with this which entailed simply shortening the tie rod -significantly-.

Correcting Ackerman compensation did teach me a few things...
1.  Catrike optimizes -Manufacturing-... so every trike gets one of 2 spindles depending on wheel size.  This may have changed for 2010 but in 2009 and before, they were all one or the other.  Obviously, with different wheel bases, not all Catrikes are optimized geometries... they are optimized for economy of scale.
2.  Near perfect Ackerman is -very- touchy.  You -will- notice a change of 1/8" in cengter to center positions on the tie rod ends once you start messing with it.
3.  Raising and lowering the position of the rod end will change the -rate- of compensation.  If you want rapid compensation, move the rod end -below- the tab on the spindle instead of on top.  I know Catrike is limited in just how uch you can change this position.

Using the typical diagram... drawing a line through the rod end from the rear wheel center to the front wheel center is amazingly accurate on trike with caster and camber.

I too test rode an '07 Expedition.  And all was good for about 15 minutes when all hell broke loose on my first downhill.  In every respect, that Expedition felt very familiar to my Actionbent with the excption that the seat was very uncomfortable on my shoulderblades... and that bleedin' shimmy.

When I got back to the shop, one of our locals was there trying to decide between the GT3 and the Expedition.  He went over to the Expediion and asked what I thought of -this-... this being a quick little shake of the rear tire and watching the whole trike just twitch like a wet noodle.  We went to my Actionbent and did the same and it was much more solid... and it doesn't even have the triangle.  I suspect that this too has a lot to do with all that shimmy.  Mind you, we are talking an '07 here and I suspect that is the same frame you have. 

I also have an '06 Road in our family.  It too shows less than optimal Ackerkman.  Once you get near full steer, it wll take over for you.  Nothing serious but having worked on Ackerman, I know it is not optimized.  The trike is rock solid on the road though.

That's my story and I'm sticking too it.  I'd suggest you get with Catrke and see if they will work with you on an upgrade.  BTW: I too have a 48" x-seam...  my boom is maximized.

[jimali]

1.  Catrike optimizes -Manufacturing-... so every trike gets one of 2 spindles depending on wheel size.  This may have changed for 2010 but in 2009 and before, they were all one or the other.  Obviously, with different wheel bases, not all Catrikes are optimized geometries... they are optimized for economy of scale.

true, there are but two different spindle models, but, the head tubes on each model are adjustable in position during engineering to place it's spindle into the correct position unique to that model.  The geometry difference in the four models using the black spindle, Dash, Pocket, Speed, & 700, is primarily wheelbase, affecting caster.  That'd take just a slight adjustment in the angle of the head tube.