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Wrench Science fit calculator - is my bike too big?

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Wrench Science fit calculator - is my bike too big?

Old 02-22-23, 11:32 AM
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spencertimm
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Wrench Science fit calculator - is my bike too big?

Hi everyone,

I have a bike that feels a little too long for me and I am trying to decide what my course of action will be. I saw a fitter and he said we can make the bike fit but this would require less seatpost offset and a shorter stem, thus potentially compromising my weight distribution and handling characteristics on the bike. Out of curiosity, I plugged my measurements into the Wrench Science fit calculator and it recommended an effective top tube length of about 540mm - for reference, my current bike is 578 mm. Could my bike really be that off? If so, it seems like I am better off buying a new frame rather than trying to make my existing one fit, but I'd be happy to hear others input.

For reference, I am on a size 56 Scott Addict Gravel. I am 74 inches tall with a 34 inch inseam, but my wingspan is only about 67 inches, hence the need for a short reach.

thanks!
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Old 02-22-23, 12:12 PM
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Since the seat tube is steeper than normal, your TT is more like a 563 on typical 56cm frame geometry. That is not long for a bike designed for people around 5'10".

Last edited by Kontact; 02-22-23 at 12:17 PM.
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Old 02-22-23, 12:16 PM
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Originally Posted by Kontact
Scott's website says the L56 Addict Gravel has a 518mm top tube.
I'm not sure where you're seeing that. I am seeing 578.5 mm for a 2022 Addict Gravel 20.
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Old 02-22-23, 12:22 PM
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Originally Posted by spencertimm
I'm not sure where you're seeing that. I am seeing 578.5 mm for a 2022 Addict Gravel 20.
Website loaded wrong. Check my edited post.
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Old 02-22-23, 12:32 PM
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Originally Posted by Kontact
Since the seat tube is steeper than normal, your TT is more like a 563 on typical 56cm frame geometry. That is not long for a bike designed for people around 5'10".

Thanks - that's helpful. Out of curiosity, how did you work the 563 figure out? I have been trying to work out the impact of seat tube angle on overall reach when looking at frames, but having a hard time doing so due to the varying seat tube angles and the impact on overall reach that my ultimate saddle height will have.
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Old 02-22-23, 08:38 PM
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Originally Posted by spencertimm
Thanks - that's helpful. Out of curiosity, how did you work the 563 figure out? I have been trying to work out the impact of seat tube angle on overall reach when looking at frames, but having a hard time doing so due to the varying seat tube angles and the impact on overall reach that my ultimate saddle height will have.
You know, I screwed it up. First I read the chart wrong for seat tube angle, then I applied the conversion backwards. I blame my phone.

Your "Universal Level Top Tube Measure" is 578. The conversion is to add or subtract 1cm for every degree difference between two bikes STA. I think the most useful STA for road bikes is 73, so if I want to compare a bunch of bikes I correct TT to 73. So if one bike had a 74 STA, you would add 1cm to the listed TT length to compare it to another that has a 73. If it is 72 you subtract 1cm, etc.

Your 56 fits a bit more like a classic 57 or 58, like someone 5'11 - 6' would ride. You are 6'2", with a 6'2" person's torso, but arms more like someone who would ride a 54cm frame. It seems like a wash to me - the reach on your bike shouldn't be too crazy for your dimensions - at least on paper. It comes with a 103mm stem, but 83mm stems are available. I don't think 83 will do anything bad for handling or look weird, and it will shrink your effective top tube to that of a 56. So it really seems like that should work for you. It is otherwise a smallish bike for your overall dimensions.

But everyone's fit is very specific, and it isn't just about dimensions. You may well be one of those people that benefit enormously from one good fit and some fit numbers you can apply to present and future bikes.

Good luck!
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Old 02-23-23, 10:31 AM
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Fit really is just your personal preference. Some people tolerate a wide range of bike dimensions and geometry and other's don't.

Sometimes I think a person's will to tolerate something until their body gets use to it is part of the equation.

The long and stretched out position you are getting with a 56 cm frame is likely better for you on that bike than the large amount of saddle to bar drop you'll have with a 54 cm bike of that model.

I use to ride large oversize bikes and was quite comfortable being so stretched out. My saddle to bar drop was little to none back then. On my Tarmac, if I was to go to the next size smaller, then the bar drop would probably be so much that I'd be uncomfortable.

So if you are uncomfortable in that stretched out position, then the better option for you would be to look at a different model bike unless you wish to have a large saddle to bar drop that the smaller size will give.

Since you bought the bike already, you've hemmed the fitter into doing things that might be more of a compromise than what a different model may have been. So whether you do what the fitter recommends or not, you are just going to have to get use to it.

Last edited by Iride01; 02-23-23 at 10:35 AM.
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Old 02-25-23, 10:55 AM
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Originally Posted by spencertimm
Hi everyone,

I have a bike that feels a little too long for me and I am trying to decide what my course of action will be. I saw a fitter and he said we can make the bike fit but this would require less seatpost offset and a shorter stem, thus potentially compromising my weight distribution and handling characteristics on the bike. Out of curiosity, I plugged my measurements into the Wrench Science fit calculator and it recommended an effective top tube length of about 540mm - for reference, my current bike is 578 mm. Could my bike really be that off? If so, it seems like I am better off buying a new frame rather than trying to make my existing one fit, but I'd be happy to hear others input.

For reference, I am on a size 56 Scott Addict Gravel. I am 74 inches tall with a 34 inch inseam, but my wingspan is only about 67 inches, hence the need for a short reach.

thanks!
Stems and seat posts are cheap. Why donít you try what the fitter recommends for a while. If you donít like it, then buy a new frame.
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Old 02-25-23, 06:39 PM
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Originally Posted by spencertimm

For reference, I am on a size 56 Scott Addict Gravel. I am 74 inches tall with a 34 inch inseam, but my wingspan is only about 67 inches, hence the need for a short reach.

thanks!
So, 6'2", average leg length & short arms. Generally, gravel bikes are made with longer top tubes and set up with shorter stems for manueuverability. I think Scott didn't get the memo on the stem part. Top tube length (57.85 cm) plus stem (103 mm) makes for 68.15 cm, which is long for a 56, gravel or road. If you size down, you'll end up with a shorter head tube, so what you gain from shorter reach, you'll lose from greater drop.. I don't think you want to go there. Your leg length puts you right in the pocket for a 56. I'd ask the dealer to let me try it with a shorter stem, the 93 or even the 83. It's a gravel bike so it's supposed to be maneuverable, and all that talk about how stem length affects stability is exaggerated anyway. You end up getting accustomed to it. 103 isn't super long and 83 isn't super short. The important thing is to get a decent fit for your somewhat odd proportions.

Just for grins, I punched my numbers into the Wrench Science calculator. The results were weird. My guess says that calculator-based fit or sizing systems generally fall apart for anyone having non-average proportions. Such as been my experience anyway, since the first edition of the Fit Kit from around 1980.

Last edited by oldbobcat; 03-01-23 at 08:04 PM.
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Old 03-04-23, 06:22 AM
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Originally Posted by Iride01
The long and stretched out position you are getting with a 56 cm frame is likely better for you on that bike than the large amount of saddle to bar drop you'll have with a 54 cm bike of that model.

So if you are uncomfortable in that stretched out position, then the better option for you would be to look at a different model bike unless you wish to have a large saddle to bar drop that the smaller size will give.
^^^This.^^^

FWIW, I would try a shorter stem before I would mess with the seatpost. Moving the saddle forward could have other negative implications. Contrary to popular belief, a shorter stem won't noticeably change the handling characteristics unless you are used to bombing descents at 40mph or more or doing other stupid stuff.

Last edited by Lombard; 03-04-23 at 06:27 AM.
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