Trek sizing

I have always rode a 54cm or M road bike, was in local bike shop today looking at a Trek Domane Sl6 and the shop guy was trying to push a 56cm onto me, he kept saying a 54 was the wrong size for me I'm 5ft 10ins, can anyone advise please?
https://www.instagram.com/seanmcgrathphotography/
Trek Domane SL7 GEN4
Planet X RT58
Cannondale CAAD 10 2012.
Pain.. Is weakness leaving the body.

HATING LIFE-CYCLES FROM 2011

Comments

  • imposter2.0
    imposter2.0 Posts: 12,028
    Your height is only one component of your size in terms of which size might be the best for you. Arm length, leg length, torso length, etc - all of these matter in determining a decent fit.

    The guy might be right - or he might be wrong. It's impossible to say on the information you've provided here...
  • N0bodyOfTheGoat
    N0bodyOfTheGoat Posts: 5,906
    edited March 2022
    https://www.trekbikes.com/gb/en_GB/bikes/road-bikes/performance-road-bikes/domane/domane-sl/domane-sl-6/p/28313/ "3 question size finder" put me on the 56cm, like OP I'm 5'10" and have stumpy ~32" cycling inseam for my height.

    56cm has 377mm reach (11mm less than my "58cm" Cube Attain GTC) and 591mm stack (19mm less than my Cube). It comes with a 100mm stem, 10mm less than Cube, so bike is by default going to feel more upright.
    ================
    2020 Voodoo Marasa
    2017 Cube Attain GTC Pro Disc 2016
    2016 Voodoo Wazoo
  • bianchi_dave
    bianchi_dave Posts: 847
    edited March 2022
    Not the same bike (obvs), but I ride a 54 medium Trek Emonda SL6 (H2 fit, 2019) and its perfect size for me. A 56cm would be miles too big for me in most brands I think.

    For reference I'm about 5ft 10in so similar height. It'll depend on how you're made as well. I have proportionally shorter legs and longer torso. I also ride two Scotts, a 52S Foil and a 54M Addict RC. I only need a 10cm longer stem (120mm) on the Foil, as although the effective top tube is quite a bit shorter than the Addict, the reach is actually less of a difference due to the different frame tube angles.

    Another thing to consider is how much saddle to bar drop you have, as this may also dictate your frame size. A bigger frame would have a taller head tube, meaning you might not be able to get the bars as low as you'd like. Similarly one that has too low a head tube could mean a huge stack of spacers under the stem.

    I'd like to know what the shop guy is basing this on, as there are a few variables. The last thing you want to do is buy a bike that's too big, whereas its quite easy to make a smaller one fit you properly. Being cynical it sounds like he's maybe just trying to sell the bike he has in stock.

    A good idea is to take the stack and reach measurements from frames you know fit. This is a great tool for comparing, as it not only gives raw numbers, but also the differences between sizes (and brands) -
    https://geometrygeeks.bike/

    Hope this helps
    Scott Addict RC
    Scott Foil Premium
    Trek Emonda Disc
    Scott Solace 10
  • bikeit65
    bikeit65 Posts: 992

    https://www.trekbikes.com/gb/en_GB/bikes/road-bikes/performance-road-bikes/domane/domane-sl/domane-sl-6/p/28313/ "3 question size finder" put me on the 56cm, like OP I'm 5'10" and have stumpy ~32" cycling inseam for my height.

    56cm has 377mm reach (11mm less than my "58cm" Cube Attain GTC) and 591mm stack (19mm less than my Cube). It comes with a 100mm stem, 10mm less than Cube, so bike is by default going to feel more upright.

    Done the 3 question size finder, it put me on a 54cm
    https://www.instagram.com/seanmcgrathphotography/
    Trek Domane SL7 GEN4
    Planet X RT58
    Cannondale CAAD 10 2012.
    Pain.. Is weakness leaving the body.

    HATING LIFE-CYCLES FROM 2011
  • kennethclark7102
    kennethclark7102 Posts: 8
    edited June 2023
    First, need to measure the bike’s frame size to make sure it suits your body type. For instance, if you want a Trek 18.5 frame size, you should get one with an ML Alpha size, which is recommended for people with a height of 5’6.9” to 5’10.5"
  • crescent
    crescent Posts: 1,201
    edited June 2023
    I bought a second hand 56 Trek Domane and I am 5'10". The sizing chart puts me bang in the middle of the 56 height range. After a few rides I was concerned that it was too big, but I think this was down to the relaxed geometry and higher front end - all my other bikes are more race orientated geometry , so quite a different feel for me. The handlebars were definitely far too big for me, they were 42cm wide with 100mm reach. I swapped these for 40cm and 75mm reach and it now feels fine. Also, I have the stem "slammed" which improves the aesthetics in my opinion. I'm happy with the sizing now, but with hindsight I would have held out for a 54 which I think would have been a better fit 'off the peg'.

    Edit : Just noticed the date of the op 🙄
    Bianchi ImpulsoBMC Teammachine SLR02 01Trek Domane AL3“When I see an adult on a bicycle, I do not despair for the future of the human race. “ ~H.G. Wells Edit - "Unless it's a BMX"