ISO - a dedicated bike for my trainer

[Jeffrey Zelevansky]

I love my Hillborne (2023, 60cm) and would like to source an inexpensive frame with similar specs that I could leave on my Wahoo Core wheel-off trainer full-time. I know it sounds like no big deal, but it's a hassle to move my Riv on and off the trainer all the time...basically daily in-season. 

I'm appealing to the hive mind here for an idea of a similar size steel frame that I could possibly buy sight unseen and kit out to use on the trainer. It doesn't need to be pretty, but does need to be sturdy. I imagine some kind of 80s-90s touring bike might work. My Hillborne is the most comfortable bike I've ever had and I'd like to get as close to that as possible. 

Thanks in advance for any ideas!

Jeff

[Garth]

Depends on how one defines inexpensive. There's endless used steel excellent quality frames on ebay anbd other bike websites. 

[Jeffrey Zelevansky]

I was wondering mainly about geometry and fit....so something in the same ballpark as my Hillborne.

I was hoping to spend less than $200 all-in.

[Eric Douglas]

I'm not sure if you need a frame with similar specs as much as you need a frame that will allow you to create the same riding position.  After all you won't  really be riding the bike when it's on the trainer, you'll just be spinning it.  So qualities that affect the ride, like head tube angle, frame material, bb drop won't really matter.

For example, on my Wahoo Core  I currently have a Bike Friday Pocket LLama.  It is very different than, say, my Surly Krampus, but since my  "riding" position on both both are the same  it works  fine.

I'd say as long as you can get the riding position the same any ole frame would  probably work-- with one caveat:

If the seat tube angle is too steep  on the trainer  frame you might not be able to get you saddle in the same position as on you Hillborn.  So watch for that.

Eric in Brooklyn

On Tuesday, April 29, 2025 at 8:18:04 PM UTC-4 jeff.ze...@gmail.com wrote:

[Nat Lichten]

Seems like the most important thing for a dedicated trainer bike is getting a top tube length and seat tube angle that’s comparable to your Hillborne. As long as that’s reasonably close, you should be able to replicate fit with seatpost length, saddle setback, stem height and length, etc. Quill rather than threadless stem would give you more adjustability.

I’ve never used a direct drive trainer, but I imagine other elements of geometry and ride quality don’t really matter. Steering geometry obviously isn’t a factor. Would you notice frame flex/chainstay length?

Finding something you can hang your existing parts bin on would be an advantage, too.

As to specific recommendations—isn’t an 80s-90s touring bike always the right answer :)? If I really didn’t have any other use in mind, though, I’d probably just look for something cheap, accessible and in the ballpark fit wise.

-Nat

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[Nat Lichten]

To be even less helpful—looks like your hillborne has a 71.5d seat tube angle, so slacker than most frames you’ll find. Maybe look for an early mountain bike?

BUT on a trainer you can slacken seat and headtube angle by blocking up the front wheel/axle—about .5 degrees slacker for each 10mm in additional height. So a frame with a pretty standard 73d sta will have about an effective 71.5d sta if you raise the front axle 3cm above the rear axle. It will also impact stack, reach and bottom bracket height, but you should be able to adjust.

[Nat Lichten]

One final correction: I realized that .5d per one cm rule is for fork axel to crown; axle height should be slightly different (more I think?). You could do the trigonometry or mess around with a bike and an inclinometer.

[Jeffrey Zelevansky]

Good points and a better way to think about this…the top tube length seems to be the most meaningful dimension. So I’m guessing anything that will get me close should work.

Jeff

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[DavidP]

Jeff - it sounds like you are grasping the concept. Eric's point about contact positions is key. On a trainer you don't need to worry about anything affecting handling so you can use a very short or long stem to get the bar height and reach where you want it. This means even top tube length doesn't have to be right on, just in a range that you can match your bar height/reach with easily available stems (to keep costs down). 

In practice this can be a pretty big range of frames. Frames with threaded forks and quill stems may be the most adjustable but you can probably get to the same place with a threadless stem and stem riser if necessary.

-Dave