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Gravel bike sizing dilemma

Old 11-14-23, 03:00 PM
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Gravel bike sizing dilemma

Hello,

I am new to gravel biking and I am in the market for a bike. I originate from a MTB background and I am quite familiar with geometry and my needs relative to the style and fit of a mountain bike but I am a little stuck when it comes to the gravel bike. Iím around 5,7/5,8 and I am sort of inbetween sizes on the particular bike I want (nukeproof digger rs) I am between a small and a medium. But I am leaning more towards a small to ensure a more upright riding position due to some recent lower back problems but the excessively small reach numbers on both sizes put me off abit. My main mtb has a reach of 460mm with a 50mm stem. And the small digger has a reach of 404mm which will then have a 60mm stem plus the drop bars. Does anyone have any experience with the sizing in regards to all of these elements or can tell me the reach/size they use relative to their height.

I would like to try the bike for size which would be the easiest option but unfortunately canít do so.

all help and feedback is greatly appreciated
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Old 11-14-23, 04:13 PM
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At your height - yeah - it's not surprising you're in between fame sizes. Changing the stem length and angle to get the right fit for your body is easy and pretty common practice. Keep in mind that a smaller frame will also likely have a shorter stack height, which may make it more difficult to get the bars into the higher position you need.

Since my preference is to be lower and probably more stretched out than you, my numbers probably aren't relatable. All my stems are slammed to the headset top cover without any spacers, and none of them have a positive rise. That's just what works for my body.
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Old 11-14-23, 04:58 PM
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Oddly enough, the reach of both my mt. bikes, from middle of the seat to middle of stem at the bar is the same, or within 10mm of all my road bikes, at 67-68 cm. I chose the medium C-Dale Topstone gravel bike as the same ETT as my road bikes, at 56cm. I vary the stems a bit as my carbon road has the h-bar an inch lower. From what you stated, I would think a 460 plus 50 stem, at 510, will make the small Digger at 404 plus 60, or 464, too small. The Digger medium has at least 20cm more ETT and might be a better choice.
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Old 11-14-23, 09:27 PM
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Originally Posted by brennan_mid
Iím around 5,7/5,8 and I am sort of inbetween sizes on the particular bike I want (nukeproof digger rs) I am between a small and a medium.
There isn't enough difference between adjacent sizes to matter. With the bike in-question, the medium is +14.7mm of reach, and +18.7mm of stack. The latter is one stem spacer, and the former is less than the adjustability offered by saddles, seat posts, stems, and bars.

Originally Posted by brennan_mid
Does anyone have any experience with the sizing in regards to all of these elements or can tell me the reach/size they use relative to their height.
Everyone's body and preferences differ, so this is a terrible way to select a bicycle -- luckily, as noted above, the size doesn't matter because there are so many methods of adjustment.
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Old 11-15-23, 03:47 AM
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Originally Posted by brennan_mid
Hello,

I am new to gravel biking and I am in the market for a bike. I originate from a MTB background and I am quite familiar with geometry and my needs relative to the style and fit of a mountain bike but I am a little stuck when it comes to the gravel bike. I’m around 5,7/5,8 and I am sort of inbetween sizes on the particular bike I want (nukeproof digger rs) I am between a small and a medium. But I am leaning more towards a small to ensure a more upright riding position due to some recent lower back problems but the excessively small reach numbers on both sizes put me off abit. My main mtb has a reach of 460mm with a 50mm stem. And the small digger has a reach of 404mm which will then have a 60mm stem plus the drop bars. Does anyone have any experience with the sizing in regards to all of these elements or can tell me the reach/size they use relative to their height.
I would like to try the bike for size which would be the easiest option but unfortunately can’t do so.

all help and feedback is greatly appreciated
What's you leg lengths?
I'm 174 (maybe 1" taller) and based on effective top tube and stack figure, would go small as the 560mm with the 60m match most small/52 gravel frame 2 UK fitters advised me to go for.

When I spoke with Ragley (founded by the guy would design Nukeproof bikes and previously PlanetX/ OnOne bikes), Ragley told me to go small and told me the following:
If your height and inside leg measurements put you in-between two sizes, then your upper body should be the deciding factor in selecting the best-sized bike for you. Your upper body dimensions determine your reach, and this affects how 'stretched-out' you'll be along the top tube of your bike. To work out if you have a long or short reach, you need to determine your 'Ape Index' (arm span minus height).
  • If you have a positive Ape Index (i.e. your arm span is greater than your height), then we suggest you go for the larger of the two bike sizes.
  • If you have a negative Ape Index (i.e. your height is greater than your arm span), then you will probably be more comfortable on the smaller of the two bike sizes.
Example: 152cm (arm span) - 163cm (height) = minus 11. In this example, you have a negative 'Ape Index', and should go for a smaller frame size.

Last edited by Fentuz; 11-15-23 at 03:51 AM.
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Old 11-15-23, 04:07 AM
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Originally Posted by Fentuz
What's you leg lengths?
I'm 174 (maybe 1" taller) and based on effective top tube and stack figure, would go small as the 560mm with the 60m match most small/52 gravel frame 2 UK fitters advised me to go for.

When I spoke with Ragley (founded by the guy would design Nukeproof bikes and previously PlanetX/ OnOne bikes), Ragley told me to go small and told me the following:
Just to clarify the small digger has a reach of 404 which is obviously a lot shorter than the 460. So just clarifying you understood that aspect or if maybe youíve misread the question?

the ape index looks like a good indicator and Iíll have a look now and see what I come up with so thanks a lot
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Old 11-15-23, 04:14 AM
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Originally Posted by TC1
There isn't enough difference between adjacent sizes to matter. With the bike in-question, the medium is +14.7mm of reach, and +18.7mm of stack. The latter is one stem spacer, and the former is less than the adjustability offered by saddles, seat posts, stems, and bars.



Everyone's body and preferences differ, so this is a terrible way to select a bicycle -- luckily, as noted above, the size doesn't matter because there are so many methods of adjustment.
I understand that height isnít the only deciding factor in what size I should select but Iím just trying to gauge from people experience.

however I donít want to buy a bike and have to adjust seat position and stem length to extremes in order to achieve a comfortable riding position as in years to come my position/feel will change and I do not wish to limit adjustability further down the line
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Old 11-15-23, 07:40 AM
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You canít compare frame reach numbers between drop bar road/gravel frames and MTB. MTB frames have for a long time been a bit longer, and in recent years gotten a LOT longer.

My MTB has a frame reach 73mm longer than my gravel bike.
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Old 11-15-23, 08:59 AM
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I used to think I was 5í9Ē, then at a physical about 10 years ago they told me Iím 5í8Ē. Jerks!!

So Iím possibly 1Ē taller than you, maybe not. I would not consider a small. My medium, has a lot of seatpost showing and i gradually increased my stem length to either 110 or 120 while experimenting with fit.

Is it safe to assume your body measures similarly to the average male of your height? 30ish inseam, arm span similar to your height, no major mobility problems (back or neck)?

Assuming your body is anywhere near mine, I think a medium is a better bet.

Look at the picture below, imagine the hoops Iíd need to jump through to get a smaller frame into the same riding position.

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Old 11-15-23, 10:01 AM
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Originally Posted by brennan_mid
however I don’t want to buy a bike and have to adjust seat position and stem length to extremes in order to achieve a comfortable riding position as in years to come my position/feel will change and I do not wish to limit adjustability further down the line
We're not talking about adjusting to extremes. Not even close. 15 and 18mm are nowhere near those extremes.

There is also no limit to future adjustability, since there is almost no position that is possible on one of these bikes and impossible on the other. The only such positions that might exist are on the opposite ends from where you are -- ie, the smallest setup for the small, and the largest setup for the medium -- and you don't care about those at all. If you did care about those positions you wouldn't be "between sizes" in the first place.

I have personally owned 51 and 58 cm Cannondales simultaneously and they had identical contact-point setups, and they both used common off-the-shelf parts, nothing exotic at all. That's an extreme example, but there just isn't very much difference between frame sizes, when compared with 200mm of seat post travel, 50mm of saddle travel, and an enormous array of stem and bar options.

If you want to spend days hemming and hawing over this decision, that's your prerogative, but it just doesn't matter (with respect to fit anyway, there might be other reasons to buy one size or the other -- such as buying bigger to maximize on-bike storage space ).

Last edited by TC1; 11-15-23 at 06:58 PM. Reason: correct typo
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Old 11-15-23, 10:43 AM
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Originally Posted by brennan_mid
Just to clarify the small digger has a reach of 404 which is obviously a lot shorter than the 460. So just clarifying you understood that aspect or if maybe youíve misread the question?
I did and looked at Nukeproof Scout (27.5 &29) before I replied. I have now looked at the reactor too. All these MTB have more reach (35 to 40mm) for equivalent rider height but I don't believe MTB reach only should be compared the gravel reach because Geometries are different.

On a mtb, upright position, the load is mostly on the hip. On a road bike/gravel, the position loads both hip and arm. If the reach is too long, you will stretch and strain you arms, neck, shoulders (20mm extra reach hurst/fatigue me).
Like I said, I am 174cm, length (heal to inseam) is 78cm, arm (shoulder to thumb crook) is 57cm and I would go for a small digger
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Old 11-15-23, 10:50 AM
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Originally Posted by Kapusta
You canít compare frame reach numbers between drop bar road/gravel frames and MTB. MTB frames have for a long time been a bit longer, and in recent years gotten a LOT longer.

My MTB has a frame reach 73mm longer than my gravel bike.
That may be. I was somewhat surprised to measure my '22 large Epic Evo, vs. my '19 medium Chisel as the same 67 cm from middle of seat to middle of stem, which is essentially the same as all my road bikes. My Epic has a 50mm stem, the Chisel a 90.
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Old 11-17-23, 02:05 AM
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I'm about your height (5-8), and always get a "medium-ish" frame rather than a "small-ish". The main reason is I prefer to err on the side of higher handlebars rather than lower. Others differ on that preference. The larger frame will have more head tube length, and therefore bar height. You can always get the bars up a little higher with the M, since there's only so many spacers that are allowed under the stem (usually 3.5 or 4 cm). The reach will be a bit longer, but usually not much more than a cm which is generally well within the normal adjustment of stem length to match up between the two. If you're looking for the most versatility shading towards an upright position, the M will always get you a couple-three cm higher. If you're more interested in a lower position, the S will always allow you to get a bit lower. If you don't have a strong preference, both will get you in the middle - the S with more spacers, the M with less.

Standover can be an issue, but not so much these days with slanted top tubes.

FWIW, I don't believe you can extrapolate much fit info going from MTB to "Gravel". Gravel bikes, at least for what I use them for, are definitely are more akin to road bikes. I've always had great success picking a gravel frame (before gravel became a thing i did the same thing with cross frames) based on comparing geometry to my most comfortable road bikes and simply deciding whether I could make if fit similarly with normal saddle and stem adjustments, remembering that saddle position is for position over the pedals, not reach to the handlebars..

Last edited by Camilo; 11-17-23 at 02:11 AM.
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