Help me build a gravel bike!

Regarding groupset, have you heard that SRAM has just released its Force eTap WIDE variant? You can now get 43/30 chainrings up front and a 10-36 cassette in the rear. If things are pan flat, you could actually go 1x. The wide range cassette can be combined with the usual 2x chainrings, of course.

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Absolutely makes sense. If that’s the case there’s not a lot of gearing difference between a 2x11 set up and a 1x12. But I get sticking to what you’re comfortable with. I’m a creature of habit myself.

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Yeah it’s all about personal preference, and the glory of a gravel bike is you can change up styles pretty easily.

And yeahhh, once you go electronic shifting once it’s really hard to go back

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Yes, saw that. :+1:t2: Since I’m a beginner rider at just 2W/kg, the 43/30 sounds perfect for me. But since I also don’t face huge climbs, I’d think a cassette with less range (10-33?) might be a better choice to get smaller jumps between gears, especially at higher speeds where I’m more likely to spend a majority of my time.

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What wheels/tires would y’all suggest that I explore? I’d like to understand what a two-wheelset solution looks like for me. For gravel, either 700x40 or 650x47 (or thereabouts), and for road, 700x32 or 700x35.

But while I’ve learned a little about bikes so far, wheels are an entirely new subject. Not sure which brands to look at, much less which wheels might be recommended or have a great reputation for this particular job.

The 10-33 cassette is compatible with the long-cage WIDE mech, so you might still opt for the WIDE mech just to have the option later on.

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No reason to wait if that’s the type of gravel you’re riding. If I remember from looking around for bikes last time…the synapse has awfully good tire clearance (especially if if’s the disc model). Slap a set of 32mm GP5000 tires on there, drop pressure to like 40psi, and start riding.

Don’t think that’s going to work… the new Synapse does have clearance for 32mm tires, but the older ones are narrower. I’m running Vittoria Corsa Control 28’s on my stock wheels and that’s probably as wide as I can go.

Thanks to SRAM’s recent releases, my bike build is becoming a little more defined. My first thought was that, however rough the surfaces may be around Florida, it’s still flat and a 1.00 lowest gear should be low enough for me. But then I spent a little time this morning with Bike Calc’s “Cadence at Speed” page and realized that even the 43/30 has far more top end than I’m likely to need in the next 5 years (e.g. 43x11 @ 100rpm = 55kph).

The new 43/30 sub-compact crankset gives me all the speed I’m likely to want, greater flexibility on the low end, a lower bottom gear (0.91x), and makes the jumps between gears even smaller when I’m going at road speeds… clearly the best choice for me, though I didn’t think so at first.

What I think I “know” I want is:

  • Open U.P. frameset
  • SRAM Force AXS groupset (43/30 front, 10-33 rear, narrow crank to avoid increased Q-factor)

Wheels are where I’ve got the least knowledge and experience. I’d like to set up two wheelsets for this bike: 700x40 and 650x47. What brands/models would you suggest I check out?

One thing worth considering is that the new 43x30 chainrings are not compatible with the Quarq AXS power meter. If you do want to run a Quarq, the 46x33 chainrings paired with the new rear mech and 10-36 cassette would pretty much give you the same easy gear with some extra top end speed.

Regarding wheels, I am super happy with my Hunt wheels and will absolutely be running them for my Open UP build. They’re way more affordable than other big brands, but the quality is still top notch. I currently have the Hunt 30 carbon gravel wheels (700c) and love them, but just set up a pair of their 650b gravel wheels for my dads bike and will probably get my own pair of the 650b wheels to run for gravel stuff on the open. For road use, I’ll probably end up with the standard Hunt 30 carbon wheelset as it is super light and I don’t want anything much deeper for a climby specific build.

As far as gear calculators is concerned, this one is much, much better and easier to understand, and allows you to compare two setups. (I’ve entered the data of two relevant combinations for a 700cx40 mm tire.) Also, keep in mind that your tallest gear is not 43:11, it is actually 43:10, which is taller than 50:12 and a little bit shorter than 53:12. In case you don’t need that much gear anyway, why don’t you consider 1x? You could put a 38-tooth chain ring up front and couple it to a 10-36 cassette in the rear. You’d get almost the same gear at the low end and you’d still make 50.6 km/h at 100 rpm in your top gear. That sounds plenty fast to me. At the low end, you’d have a ratio of 1.06 (approximately 34:32) instead of 1.00.

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I second the Hunt wheelset recommendation, I’ve got two sets and they’re great, very lightweight and not crazy expensive. They’re a smaller company so I was hesitant initially but they’re legit.

When choosing gearing, remember that the effort required for different gear ratios is also a function of tire size (actually complete wheel radius). A 700x28 tire radius is 343 mm, while a 700x42 is 357 mm and a 650x47 is 343 mm. Notice that the 700x28 and 650x47 are the same.

The true way to compare gearing regardless of wheel size is gear inches or gear meters (also called development). Make sure you stick with either inches or meters. So pick a tire size that you are used to, figure out the gearing you want, then check what range of development that is. Now input the new tire size and see if a different set of gears would better match the development you had in mind.

If your gearing ratio needs are low enough to keep decent jumps between gears, I do recommend 1x. On the road, I am full in the 2x camp. For mountain biking, I think 1x is better because you don’t want spacing too tight or you have to do multiple shifts all the time and with short steep hills that kills your momentum. For gravel, I think it really depends where you ride and what you plan to do. I want my gravel bike to be a pretty decent road bike and an OK light XC bike. I also like to ride to the MTB trail. So 2X is needed to get the gear range to cover all that. And I will run multiple wheelsets to allow me to easily use the right tires for the ride I am doing.

Riding in flat parts of Florida means you probably only need the range of 1x, but might not like the gear spacing

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Nailed it on all fronts. Plus, I’ll add that as an overweight new cyclist, I still can’t get down in the drops for more than one minute at a time, and even my Synapse’s riding position is a challenge for my current level of core strength. So even as I continue to improve and get fitter, I’m hoping that a great gravel bike experience may also help me spend more hours on the bike enjoyably and get me in better shape that much more quickly. 2x and two wheelsets for me, too.

Favorite wheels/tires?

I am still getting the extra wheelsets setup. I have the stock 700c 25 internal width wheels that came with 700x38 Donnelly MSO tires. The tread on those was fine but they were way too stiff. I swapped on some Rene Herse (previously Compass) Hurricane Ridge (knobby 700x42) Endurance tires. Those are much more supple, roll amazingly well and corner as if they were slicks. :+1:

I got my 650b wheels but I am waiting on my tires to come in (Rene Herse Juniper Ridge 650x48 Endurance knobby).

I am waiting to hear back on lead times to see which aero road wheels I order. I hope to order something today or tomorrow, but they will probably take 4-6 weeks to get. I am going to run Conti GP5000 TL (25c or 28c) on them.

Please share more feedback on what you do with wheels/tires overall. This is my primary area of reading/learning right now and I’d like to get it right without too much experimenting. Re the Contis comment I quoted, may I strongly recommend 28? On my Synapse, I had the chance to try 25 and 28 and really, really like the 28’s much more. I’m running 20 psi lower (80 vs 100 before), it’s much more comfortable, overall speed seems to be as good or better. I did end up accepting the higher rolling resistance of the Vittoria Corsa Controls to get better puncture resistance, but I’m solidly sold on 28 over 25 for non-racing road riding.

I agree that bigger tires ride nicer.

The thing is though, you have to consider the real actual width of the tire, not just the stated width. Some tires marked as 25c will measure 27 or more on 17 mm internal rims (the standard that they are supposed to use). Also, using a rim wider than 17 mm internal will make the tires wider. I am looking at 21-25 mm internal width rims, which will grow the 25c GP5000 TL to around 27.5 to 29 mm.

For my aero wheels, I am trying to balance aero performance with safety and comfort. For best aerodynamics I am going with U shaped (toroidal) rims and keeping the external rim width 105% or more larger than the actual tire width. But you also have to keep the tire wider than the rim internal width by enough to not cause a safety issue. So I will pick my tires based on which width rim I settle on.

This Mavic blog link explains the tradeoffs and gives a compatibility chart. However, many people say this chart is too conservative. I have been reading various sources to decide my way forward.

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Thanks. While tires have both objective and subjective criteria, they seem to be easier to research and understand. Where I’m having some difficulty is in learning about wheels… average/typical cost (and range), pros/cons of various traits, brand profiles, discussions, recommendations and so on.

I can find reviews and “guides” like this one from Cycling News, but there’s not a lot of depth in that discussion and, since they seem to be choosing which ones to recommend, also not a whole lot of breadth into which I can sink my teeth and learn more.

I see this all the time on this forum and I guess I will add that it doesn’t necessarily work that way.

Meaning, I don’t think that wider internal width wheels automatically balloon out your tire to a width wider than the marked width. When you say “a rim wider than 17mm will make the tires wider.”…I don’t necessarily agree.

In fact, mine worked exactly the opposite way.

Here are some pictures of my wheels/tires.

Tires are 28’s Schwalbe Pro One

Wheels are 28 external and 21 internal Enve’s.

The wheel is wider than the tire when mounted and fully inflated to the recommended pressure.

The first picture shows the fully aired up tire which comes in slightly under 28.

The second shows the wheel and my photo skills are crap because it’s pretty much spot on 28 but looks a little over on the photo.

The 3rd pic shows the caliper on the tire using the width of the wheel as the measurement. You can see about a 1mm gap in that pic.

So if anything, my tires are under the stated marked width of the tire and definitely did not balloon out.

Honestly you can deep dive the subject of wheels, but I wouldn’t over think it if you aren’t going to target aero performance.

You need wheels that have the right axle standard and free hub for your bike. It helps if the wheels you pick use hubs that are easily converted to work with future or different standards for use on other bikes. I am going with DT Swiss hubs because of that. They are pricey and weight savings at the hub has little benefit, so I am going with the 350 hubs instead of the lighter and more expensive 240s or 180.

Higher points of engagement (POE) is nice, but IMO over hyped unless you will be riding technical trails where you need to be able to lay down power at low speed while positioning your cranks just right to not hit something. Higher POE generally makes for louder hubs while coasting. I choose to use 36T ratchets in the DT hubs even though there’s a 54T version available because the 54T is too loud. I don’t want to be distracted by my hubs on a beautiful ride. Most normal hubs come with 27T, which is plenty for gravel IMO.

Lighter is better and you pay for it. Aero wheels trade weight for better aero. Stiffness is complicated in that you want the right kind of stiffness and the right flex, just like a bike frame.

In general, spending more money gets you better wheels.

Since my bike is disc brake, I am rolling the dice a bit and getting some custom built Light Bicycle (Chinese carbon) aero wheels. The other 700c wheels will be the Easton EA70ax that cane stock on my bike and the 650b wheels are Fulcrum Rapid Red 5 db because those were the only suitable ones my LBS found any inventory of.

If you are buying an OPEN, I would get my initial spec together and ask OPEN for their opinions on it. They seem to be eager to help. They also have galleries of customers’ bikes to help you see how people built theirs.

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