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This under-seat steering tadpole has a pretty large turning radius. The limitation seems to be that the handlebars will bump into the seat. When this happens the actual steering linkage seems like it would have more travel that could be used.

I'm looking for advice on how potentially to improve this. I'm not adverse to some new parts or modifications if that seems necessary / beneficial, but obviously if there is some kind of adjustment that would be worth trying first.

I can start taking things apart but thought it was worth looking for insight here before just monkeying around. In particular I don't want to mess up the wheel alignment or something like that.

Here are photos of the steering linkage etc.:

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Its a Sun EZ-Tad CX. Not the lightest thing out there but fun to ride :)

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  • The steering might become too twitchy!
    – Carel
    Mar 21, 2020 at 13:09
  • @Carel actually it already is a little bit...
    – StayOnTarget
    Mar 21, 2020 at 13:16
  • Those photos are not sufficient. In general it should be possible, but not necessarily desirable. The wheels might start hitting your hands.
    – Nobody
    Mar 21, 2020 at 22:59
  • Can you lay the trike on its side and take a photo directly from below? This should show the steering linkages more clearly. I suspect your ultimate limiting factor will be how far the wheels can turn before hitting something.
    – Criggie ♦
    Mar 21, 2020 at 23:59
  • There's a SX variant, specs at sunseeker.bike/index.php/products/ez-tad-sx specifically say Updates to the EZ-Tadpole SX include Direct Steering so there are no pushrods to adjust - that will limit your options a lot sadly. If yours is more like sunseeker.bike/index.php/products/t3-cx is the the T3-CX then its also a Direct Steering model. The underside photo will help a lot.
    – Criggie ♦
    Mar 22, 2020 at 0:02

1 Answer 1

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For a start, I would suggest you loosen the indicated pinch bolts, and push the bars forward a little, and rotate them outboard a little.

Mod of OP's photo

This is an adjustment, not altering the curve in the metal... the sketch is misleading.

  • By moving the bars forward in the indicated pinch bolts, you'll get more wheel-turn for the same movement of the handlebars.

  • Rotating the bars so they're further apart will give you more space before the bars stop on your seat.

And the best part - all that is completely reversible if you don't like it.

Modifying the push rods is going to be a lot more brutal and permanent. I'd start with a mock up using something cheap and disposable, perhaps plastic pipe or cardboard roll-centers temporarily.

Another annotated version of OP's photo.

I'm hedging a bit here but I THINK moving the pushrod at one or both ends will alter your steering like you want.

Downside is the width of the straight-ahead window will be much smaller, so you're going to have to actively steer a lot more when not turning.

Since its going to be very hard to change the steering arm on the wheel's hub, you might be better off checking with the supplier in case they offer any options to achieve your goal. A steering arm replacement with a hole that is closer to the kingpin would be much safer than you attempting to drill a new hole for the swivel. Note that the swivel will be a tapered hole too.

The safest solution would be to make an adapter plate that attaches to the main bar, and make two new shorter pushrods. That way you can revert to stock with no changes.

Also, consider making a scale model of the steering, using cardboard and pins to get an understanding of the relationships between your ideas and their effects.

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  • I appreciate the thought that went into this. I will definitely start with some adjustments before modifications. Moving the pushrod attachment points seems like it would require shorter pushrods?
    – StayOnTarget
    Mar 29, 2020 at 11:44
  • @UuDdLrLrSs yes you would need to shorten the pushrods, which makes it harder to revert. So if you can't get the amount of adjust you need by screwing in the ball joints further, then I'd recommend getting some shorter pushrods made in preference to cutting the ends off your existing pushrods. Also, I think smaller changes would be good here - the pictures are exaggerated to show the differences. Doing a mock up on the kitchen table would help you explore changes, without messing up the bike.
    – Criggie ♦
    Mar 29, 2020 at 21:10

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