Size of bike for Trainer

I have decided that I want to get a dedicated “trainer bike”, so i can stop beating on my more expensive bike (plus its a pain taking the back wheel on and off etc)
I"m 5’10 and normally ride a 56 bike. There is a size 58 trek Madone that is being sold at a nice price.
i’m wondering if i can make that match the important geometry points of my road/ gravel bikes.
what does the forum think?

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Hard to say for certain without knowing the actual model, size and year of each bike (for full geo values), but road bike to road bike, and size being what is likely a single step apart… it can probably work.

Key is getting the saddle in the right relationship to the BB so both bikes match. Ideal considerations:

  • Same saddle
  • Same saddle height & fore-aft (relative to BB)
  • Same handlebar reach & drop (functional to the hoods, since these can impact final fit)

Also consider that a crank length change is sometimes common at that size step, so it should be checked.


  • Nailing this might include swaps of cranks and seat post on the rear, as well as stem (size and/or position) combined with handlebars… all with the aim to put you in the same physical position and orientation relative to the BB.

  • Adding to that, as a rider with more bikes than sense… I train on a single, dedicated 56cm endurance road bike… but apply my fitness on a 56cm road & gravel bikes, a tri bike, a couple Large MTBs and even BMX. Point being that it may not be “ideal”, but I find that it’s not critical to match any or all of those to the millimeter. Maybe I am missing out on gains, but I don’t think our bodies are that sensitive.


awesome info…thanks

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Get a bike that is the correct size, even for dedicated use on a trainer.

I have a 2010 bike (my only bike) and recently found out that it is effectively a 59 due to changes in geometries over the last 12 years and misrepresentation / misunderstanding when I bought it. The improper size has led to a lot of fit problems and some interesting adjustments to make it fit as best as it can.

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