I've got a 3.0 that gave me pause over 30mph in spite of repeated toe-in adjustments. I simply drilled two new holes in the tab on the handlebar so I could move the sterring arms pivot forward about 3/4 inch. When I realigned the steering and set the toe-in back to zero, there was a TREMENDOUS improvement in the twitchiness--40mph now is solid! Only downside I've discovered in a couple of hundred miles is the turning radius has increased. Looks like the same handlebar input is down about 35% at the hubs. Simple and very effective.
John, You're on the same page with us! About two weeks ago we started adding the front hole option to the production models. Now every version 3.2 TerraTrike comes standard with "Touring" holes and "Commuter" holes so the rider has the option. The Touring holes, while increasing your turning radius, dramatically slow down the steering so it is much less twitchy at high speeds. These holes are drilled on the handlebar tongue slightly forward and toward the center of the original holes (essentially in line with the tie rod arc).
Here's the deal: This alteration can be made to any TerraTrike. What you need to do is draw lines on the tongue that bisect the steering pivot, and the tierod holes. This is your Ackerman line. Then measure the same distance along this line on each side (make sure it's the same on both sides!). The closer to the steering pivot you go the slower your steering will feel, and the greater your turning radius will become. It will vary in diferent models, but most folks will feel a significant difference with holes about 1/4 of the distance toward the steering pivot. Drill your new holes, and realign your front wheels. Most of them are 8mm, but some older models are 5/16" bolts. Be careful doing this, and make sure you retighten everything.
I think the steering squirreliness is due to a combination of 1) toe-in adjustment , 2) slop in the front end and 3) not enough castor. You can do something about 1 and 2. No. 3 requires some redesign and more work. I'm still thinking about that. 1) Toe-in. I've been playing with mine and I now have mine just barely toed in (1/8th in measured at the rims). Play with yours. 2) The biggest improvement that I felt in the steering was from eliminating all of the slop in the front end. I made sure that the kingpin nuts were tight - tight enough so that there was no movement of the hub mount when rocking the axel, but just lose enough to still allow the hub mounts to turn. I made sure that the axel nuts were tight enough so that there was no play when rocking the wheel - but lose enough for the wheel to turn. Check the handle bar nut to see if it is snug enough - so that there is no slop in the handle bar pivot. Check your tie rod ends. If you grab a tie rod and shake it left and right, you'll probably here some rattling. This is due to the tie rod ends having too much play around the sperical bearing. I replaced mine with higher quality rod ends. I got them from an old racing buddy so I can't tell you where to buy them. There are many good brands out there. Good ones have a nylon insert around the sperical bearing. A good rod end should have such a tight fitting sperical bearing that you can barely (if at all) rotate the bearing with your fingers. Here is the info on mine: Aurora Bearing Co. 970 S. Lake St. Aurora, IL 60506 630-859-2030 You need 2 of each: MM5ty 5/16-24 Male RH (right hand) MB5ty 5/16-24 Male LH (left hand) I was surprised that they are not metric. Most of the hardware on the TT is. WW has come up with an odd mix of metric and SAE hardware.
You might want to also consider installing some longer 10mm bolts (kingpins) with the unthreaded length of the bolt being long enough so that no threads are inside the bushing tubes. I'm thinking that this may reduce any wear that may occur from threads within the bushings. I had to stack a couple of washers since the unthreaded length was just a bit too long. I purchased them at a local shop called Specialty Tool & Bolt (1-800-SB-BOLTS) at:http://www.sbbolts.com/. The part number is: M10-1.5x90 SHCS.
(and here's the full text of Michael's message about prices and part numbers for various handy nuts and bolts)
[From Michael Billesbach] I found a place that has a good selection of metric bolts in stainless or hardened steel (black oxide coated). They'll ship small orders. It is Specialty Tool & Bolt (1-800-SB-BOLTS) at:http://www.sbbolts.com/. They say their minimum order is $5.00. I've recently replaced some of my already rusting metric bolts with stainless steel. Here are the part numbers. I've included the prices I paid. Your price may vary. I'm not sure if he gave me some kind of break. Idler Wheel bolts Part No. M8 - 1.25 x 100 SHCS S/S Qty 2 Price 2.55 ea Seat clamp bolt Part No. M8 - 1.25 x 70 SHCS S/S Qty 1 Price 2.11 ea Kingpin bolts Part No. M10 - 1.5 x 90 SHCS S/S Qty 2 Price 2.94 ea Note1: The unthreaded length extends beyond lower bushing a bit. You'll have to stack 2 or 3 washers ( Part No. M10 F/W S/S). You'll probably want to cut off some excess threads. Note2: These stainless bolts are softer than the stock bolts. I haven't had them installed long enough to detect how well they wear. Kingpin nylock nuts Part No. M10 - 1.5 Nylock S/S Qty 2 Price .21 ea Seat to upper seat stay Part No. M5 x 45 SHCS S/S Qty 2 Price .55 ea