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650 or 700's On A Gravel Bike

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Cyclocross and Gravelbiking (Recreational) This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like : "Unbound Gravel". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

650 or 700's On A Gravel Bike

Old 05-14-18, 04:21 PM
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650 or 700's On A Gravel Bike

What's your preference for wheel size on your gravel bike ... my reason for buying one is I've been riding a 29er and as I've got fitter my overall distance of rides has been steadily increasing with the percentage of road vs gravel increasing so I'm looking for more road friendly and all my gravel tracks whilst there are a few lumpy ish bits are mostly fairly compact and non technical so am guessing I'd probably be better off with 700's.

That said I've seen a few comments saying shorter riders are generally more "comfortable" on the smaller wheels (I'm 5"7) although I would of thought if you buy the right frame size and I'm used to riding a 29er this probably won't be so relevant.

I'm looking at possibly getting a Salsa Journeyman which one company in the UK has in stock in the 650 but they can get a 700 shipped within about a week, I've had a look on their website and it seems the geometry for both is exactly the same so guess worst case scenario I could change the wheels if I wanted.

Interested in hearing others preference is and also the reason behind it with any plus / minus points of one vs the other.
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Old 05-14-18, 05:16 PM
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I have both 650 (47mm tires) and 700 (40mm tires) wheels for my gravel bike (Niner RLT9). At this point, the 650s are my preferred setup because the lower pressures required--more comfortable ride and better on some of the fire roads/trails local to me that are borderline mountain bike territory. The lower standover is a nice perk, but wouldn't make me choose one size over the other.
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Old 05-14-18, 09:10 PM
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I much prefer the way 700c wheels ride for all sizes 23mm through 55mm. There's a physiological component that is hard to quantify but the bigger wheel feels like it is more in sync with my pedaling style.

With 650b and 26" wheels they always feel like there's a dead spot, lack of rotational inertia that doesn't feel as good. This is especially obvious going from 700cx23 to 650bx23. But I think it may go away as the tires get bigger but I'm pretty sure I still felt it on 650bx48 and 26"x2.3" or it could all be psychosomatic nonsense.

Some would argue that there is no right frame size for 29" wheels and a 5'7" rider. I'm not necessarily in agreement. If you have no problems with your current wheelsize I'd just stay with it. But it would definitely be worth your while to at least test a 650b or even 26" bike.
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Old 05-14-18, 10:17 PM
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Originally Posted by Spoonrobot
I much prefer the way 700c wheels ride for all sizes 23mm through 55mm. There's a physiological component that is hard to quantify but the bigger wheel feels like it is more in sync with my pedaling style.

With 650b and 26" wheels they always feel like there's a dead spot, lack of rotational inertia that doesn't feel as good. This is especially obvious going from 700cx23 to 650bx23. But I think it may go away as the tires get bigger but I'm pretty sure I still felt it on 650bx48 and 26"x2.3" or it could all be psychosomatic nonsense.

Some would argue that there is no right frame size for 29" wheels and a 5'7" rider. I'm not necessarily in agreement. If you have no problems with your current wheelsize I'd just stay with it. But it would definitely be worth your while to at least test a 650b or even 26" bike.
I'm 5'7" (actually more like 5'6.5") and my MTB is a 29r. Went from a 650b to that with no issues. I think I prefer it to the 650b, at least for where I ride. My gravel bike is 700c and I love how it feels on the road and on the dirt. Honestly, even though it's very road-worthy, I still ride that bike pretty much everywhere I ride my MTB. I'm pretty sold on 700c for my gravel, do-it-all rig...
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Old 05-14-18, 11:17 PM
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If you have the same rolling diameter, like 700c x 25, or 650b x 42, or 26” x 2.3, they should feel pretty similar in acceleration and it’s willingness to turn. This assumes the same rim profile and tire construction. The polar moment of inertia is about the same (the effect of mass rotating at a radius). Where the larger rim diameter weighs more, but uses a smaller tire, so it is a wash. The larger tire will be cushier, and have more pneumatic trail.

If you do lots of twists and turns, you may like the more nimble feel of smaller rims with smaller tires. If you fly straight and level, you may appreciate smooth ride and stability of large rims and tires. If you get a bike with disks, you can just swap wheels.

Personally I run 700c x 44c on a monstercross frame as an “allroad” bike, but I am 2m tall. Though I mostly ride pavement, I haven’t owned a “Road” bike since I first tried wide tires. On my last century, I passed half the field on a long stretch of rough road.
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Old 05-15-18, 03:11 AM
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Cheers for everyone's input, I think it's probably helped to confuse me even more

Joking aside ... it probably has helped me decide as it seems to re-iterate what I initially thought and what I want to use it for taking the tracks around here into consideration.

I'll probably go with the 700's and a reasonable width initially and see how I get on, if I'm finding it too bumpy I could get a 2nd set of 650's nearer the winter with wider tyres which will also help when it's wetter and muddier.

Thanks again much appreciated
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Old 05-15-18, 05:38 AM
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I'm in the middle of experimenting w/the very question. I have two Priority bicycles -- identical frames -- one with WTB Horizon 650b x 47 tires, and the other with Soma Shikoro 700c x 38. The Horizons I'm running at 30 psi, and the Shikoros at 40. The Horizons measure at 45 mm, and the Shikoros measure at 35 mm -- both are a tad narrower than nominal size.

Sunday was my first ride on the Shikoro tires. Very nice. Good on pavement. Good on hardpack dirt roads. Way worse than the Horizons on deep sandy patches, and by "deep" I mean when there is a couple inches of loose, eroded sand and gravel to churn through. The wider Horizon tires are also better on a chunky rail grade that I ride that has lots of leftover ballast rock. The 650b Horizons roll surprisingly well on pavement, but I'd have to give the edge on pavement to the 38 mm Shikoro tires. (Not sure I trust my feelings though).

Two photos below. First shows the sort of hardpack road that the 38 mm tires did well on. The second shows some of that rail grade where I prefer the wider Horizon tires and their lower pressures. The Horizons lower pressure smooths out the rail grade, and their width brings stability in the loose rock.

Hope all this helps! Just am sharing my experience. Good luck with your decision. And disk brakes make it easy to buy two wheel sets and swap back and forth.



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Old 05-15-18, 09:31 AM
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Originally Posted by Witterings
I'm looking at possibly getting a Salsa Journeyman which one company in the UK has in stock in the 650 but they can get a 700 shipped within about a week, I've had a look on their website and it seems the geometry for both is exactly .
Canyon switches from 700c to 650b for riders under 5'5". If you are 5'7" and comfortable on a 29er, you should be good with 700c.

I"m assuming your are asking wheel size for a smaller rider?
Or is it 700c vs 650b for the same diameter wheel?
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Old 05-15-18, 09:53 AM
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JonathanGennick .... useful info as well, there was only the one photo ... was that the 700's ???

Do you have the other photo you can post would be interested to see the comparison??
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Old 05-15-18, 10:41 AM
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Originally Posted by Witterings
JonathanGennick .... useful info as well, there was only the one photo ... was that the 700's ???

Do you have the other photo you can post would be interested to see the comparison??
I'll try and find a photo of the other bike. The two shots earlier were meant to show the different road surfaces. The tires on the black bike are the Soma Shikoro 700c × 38 mm. They work good! I'm not sure I would have tried 650b if I had had the Shikoros first.

Found a photo. Same frame. Different paint. WTB Horizon 650b × 47 mm tires. These cross over pretty well to easy singletrack.



​​

Last edited by JonathanGennick; 05-15-18 at 10:48 AM. Reason: Typo and add photo
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Old 05-15-18, 12:38 PM
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Originally Posted by JonathanGennick
I'll try and find a photo of the other bike. The two shots earlier were meant to show the different road surfaces.
​​
No that's fine ... when I looked at it earlier there was only one photo in there ... I wonder if I looked at it literally as you posted and the other was still uploading so didn't display as the 2nd one's now there .... weird.

It's made me think AGAIN though as some of the track I ride is more like the "rougher" than the other one and you say you prefer the 650 on that ... so really useful thank you!!!!
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Old 05-15-18, 12:50 PM
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Originally Posted by Witterings
No that's fine ... when I looked at it earlier there was only one photo in there ... I wonder if I looked at it literally as you posted and the other was still uploading so didn't display as the 2nd one's now there .... weird.
Could have been! Wow. We probably couldn't do that again if we tried.

It's made me think AGAIN though as some of the track I ride is more like the "rougher" than the other one and you say you prefer the 650 on that ... so really useful thank you!!!!
I wish I could just let you try them both back-to-back. Did that on Monday with a local friend. We took both bikes out and swapped back and forth.

I like to ride gravel in "blast through it" mode. The softer and wider tires are nice then.
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Old 05-15-18, 03:27 PM
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Originally Posted by JonathanGennick
Could have been! Wow. We probably couldn't do that again if we tried.

I wish I could just let you try them both back-to-back. Did that on Monday with a local friend. We took both bikes out and swapped back and forth.

I like to ride gravel in "blast through it" mode. The softer and wider tires are nice then.
It's got weirder still ... I looked at the post initially on my main computer ... it was when I then opened it a 2nd time on a laptop in the kitchen and I saw the other picture .... I'm now back at my main computer and can only see one picture again ... that is weird

So sorry ... on the rougher surface you're saying both you / your friend preferred the wider tyre ... that's what the tracks I cycle over are like, you can often find a way between the lumpier bits but it's by no means as smooth as the other picture I can't see again

Have you tried them back to back on the road as well and is so where does your vote go then???
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Old 05-15-18, 03:34 PM
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Back at the laptop and shows both photos again ... I just re-read all you posted and looked at both pics .... makes me wonder if if you only wanted one or the other if a 700 x 45 may be the sweet point between the two, a bit more volume for the courser bits without too much penalty on the road depending what pressure you run them at???
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Old 05-15-18, 04:25 PM
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Originally Posted by Witterings
Back at the laptop and shows both photos again ... I just re-read all you posted and looked at both pics .... makes me wonder if if you only wanted one or the other if a 700 x 45 may be the sweet point between the two, a bit more volume for the courser bits without too much penalty on the road depending what pressure you run them at???
If I could take only one, I'd choose the 47 mm Horizons. No question. That's an easy call. The wide tires are more fun. I'm happy to have a second bike with 38 mm tires, but you won't pry the wider-tire bike from my cold, dead hands .
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Old 05-15-18, 04:46 PM
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700x43 tires....I've thought of doing a 650B set just to fit winter knobbie/stud tires. Haven't bothered spending the money yet. By the time I found myself wanting them this winter-didn't have the money lying around for the build and the sales were passed. The other side of it being that 650B won't get me a ton more clearance than I have, Can get a 700x50 in back if I wanted it, which usually I don't have any need of regularly here.
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Old 05-15-18, 04:51 PM
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Originally Posted by Marcus_Ti
700x43 tires....I've thought of doing a 650B set just to fit winter knobbie/stud tires.
I couldn't find good selection in 650b for winter tires, at least not for studded winter ones. I had to revert back to 700c -- 38 mm Gravdals -- for winter. Those were ok though, but I'd have paid a lot for 650b 47mm studded version of the Horizons.
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Old 05-15-18, 05:16 PM
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JonathanGennick ... brilliant and thank you for your help again ... along with everybody else that's posted!!!

Originally Posted by chas58
I"m assuming your are asking wheel size for a smaller rider?
Or is it 700c vs 650b for the same diameter wheel?
I didn't quite get this .... I was asking because I'd seen comments saying the 650 put the shorter rider closer to the ground so was more stable, I wonder if part of it was also to do with the "reach" on a bike who's geometry was set up for a 700 instead.

The part I didn't get (hence why I haven't responded before) was the
is it 700c vs 650b for the same diameter wheel
... surely they'll never be the same as the 650 or 700 refers to the diameter including the inflated tyre??

The size of the actual wheel for say a 700 is 622 and the depth of tyre makes it up to 700 ..... the 650 .. if it was the A or C then again the size of the actual wheel would vary so the overall diameter would remain as 650 ... or have I totally misunderstood ... either ... what you've said or the whole concept of tyre sizing .... with my grey matter both are highly likely :-)
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Old 05-15-18, 05:25 PM
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Originally Posted by Witterings
JonathanGennick ... brilliant and thank you for your help again ... along with everybody else that's posted!!!



I didn't quite get this .... I was asking because I'd seen comments saying the 650 put the shorter rider closer to the ground so was more stable, I wonder if part of it was also to do with the "reach" on a bike who's geometry was set up for a 700 instead.

The part I didn't get (hence why I haven't responded before) was the ... surely they'll never be the same as the 650 or 700 refers to the diameter including the inflated tyre??

The size of the actual wheel for say a 700 is 622 and the depth of tyre makes it up to 700 ..... the 650 .. if it was the A or C then again the size of the actual wheel would vary so the overall diameter would remain as 650 ... or have I totally misunderstood ... either ... what you've said or the whole concept of tyre sizing .... with my grey matter both are highly likely :-)
In theory it does...IRL no it doesn't. A 650Bx47mm (ish) tire for example is approximately equivalent IRL to a 700x30mm(ish) in inflated tire diameter/circumference. Ergo you don't screw with the BB height and stability between the two. The difference being, ofc, that the 650B wheel/tire has a ton more volume.

Wheel Comparison: 650B vs 700c -
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Old 05-15-18, 05:52 PM
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Originally Posted by Witterings
The part I didn't get (hence why I haven't responded before) was the ... surely they'll never be the same as the 650 or 700 refers to the diameter including the inflated tyre??
That's what the names "700" and "650" originally referred to, but the actual inflated wheel diameter depends on the tire you install. Wider tires also tend to be taller tires. In practice, "700c" means that the rim has a bead seat diameter of 622mm, and "650b" means it has a bead seat diameter of 584mm. A 650b wheel with a massive tire can have a larger inflated diameter than a 700c wheel with a tiny tire.

Originally Posted by Witterings
makes me wonder if if you only wanted one or the other if a 700 x 45 may be the sweet point between the two, a bit more volume for the courser bits without too much penalty on the road depending what pressure you run them at???
The lower pressure of wider tires isn't a very significant issue for road riding. Wider tires deform less at a given pressure, so a wider tire can be pumped squishier than a narrow tire and still have similar rolling performance.

On pavement, the differences between 700c x 40, 700c x 45, and 650b x 47 are going to far too small to easily isolate and measure. And very small compared with differences from the other aspects of tire construction. The 2.1" tires that are currently on my gravel bike can run circles around slow 25mm tires, because the size matters less than how high-performance the tires otherwise are. If you want paved speed, choose supple tires without an aggressive tread pattern and without beefy stiff protection layers.
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Old 05-15-18, 06:00 PM
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Originally Posted by Marcus_Ti
In theory it does...IRL no it doesn't. A 650Bx47mm (ish) tire for example is approximately equivalent IRL to a 700x30mm(ish) in inflated tire diameter/circumference. Ergo you don't screw with the BB height and stability between the two. The difference being, ofc, that the 650B wheel/tire has a ton more volume.
OK .. so this may be the bit I'm not quite getting ..... lets take say a 650 x 25 (just picking something at random to give an exaggerated comparison) vs a 650 x 45 ... are we saying one (lets take the 25mm here) may have a perfect diameter of 650mm and the wider tyre may may have a greater height / depth (to keep it in proportion ???? ) and IRL may actually have a diameter of say 655 ... hence why it' coming close to a 700c????

Sorry I know this is me being thick ... give it to Xmas and I may just about be there
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Old 05-15-18, 07:42 PM
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Originally Posted by Witterings
are we saying one (lets take the 25mm here) may have a perfect diameter of 650mm and the wider tyre may may have a greater height / depth (to keep it in proportion ???? )
Tires inflate to a roughly circular cross-sectional profile. A circle that's wider is also taller.

Clinchers aren't perfectly circular in the real world, but this is basically what's going on:



are we saying one (lets take the 25mm here) may have a perfect diameter of 650mm
and the wider tyre ... may actually have a diameter of say 655
The inflated diameter difference between a 25mm tire and a 45mm is usually on the order of a few centimeters.
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Old 05-15-18, 07:43 PM
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Originally Posted by Witterings
OK .. so this may be the bit I'm not quite getting ..... lets take say a 650 x 25 (just picking something at random to give an exaggerated comparison) vs a 650 x 45 ... are we saying one (lets take the 25mm here) may have a perfect diameter of 650mm and the wider tyre may may have a greater height / depth (to keep it in proportion ???? ) and IRL may actually have a diameter of say 655 ... hence why it' coming close to a 700c????
Yes. You're getting the hang of it. 650 used to refer to an outer diameter of the tire. That outer diameter plus a tire width (the b part) forced a given rim size. We now refer to that rim size as 650b, and today we just let the outer diameter fall where it may.

When I switched from 32 mm 700c tires to 47 mm 650b tires, I did get a centimeter or two of drop. Maybe closer to a centimeter. Not enough to worry about, and I rather like the feeling of having the bottom-bracket closer to the ground.
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Old 05-15-18, 08:22 PM
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On pavement, the differences between 700c x 40, 700c x 45, and 650b x 47 are going to far too small to easily isolate and measure. And very small compared with differences from the other aspects of tire construction.
This doesn't make any sense. Larger tires, of the same construction, are known to be more comfortable. This is an attribute that can easily be measured by ones hands and butt or even an accelerometer if one was feeling high-tech.

I can easily feel the difference between 700cx40 and 650bx48. The difference is also easily measured in a series of short roll-down tests. Both tires were gravel king slicks, at the same level of sag the larger tires obviously roll slower. Results were not scrutinized through a regression analysis.
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Old 05-15-18, 10:24 PM
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Originally Posted by Spoonrobot
This doesn't make any sense. Larger tires, of the same construction, are known to be more comfortable. This is an attribute that can easily be measured by ones hands and butt or even an accelerometer if one was feeling high-tech.
I mean about overall performance, not feel.

Although at these widths, I'd argue that the difference in plushness on paved roads is usually irrelevant too. Even good 25mm tires seem to adequately deal with nearly all surface irregularities on most paved roads, when pumped appropriately. Very few paved roads have enough medium-frequency roughness that 48 provides a significant smoothness benefit over 40. Of course, such roads often exist in clusters.

I can easily feel the difference between 700cx40 and 650bx48. The difference is also easily measured in a series of short roll-down tests. Both tires were gravel king slicks, at the same level of sag the larger tires obviously roll slower.
Interesting. What is an "obvious" difference in this case? What particular pressures were being used?

This comparison confuses me quite a bit, because the overall size difference between those two tires isn't really thatbig, due to the BSD difference partially offsetting the width. The main penalty that a bigger tire would normally be expected to have on coast-down is from aero, but the 650b only increases the profile of the system by a few square inches.
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