Twenty9er

Greetings! I am new to the forum and gravel biking, but, just picked up a used BMC URS One (3) and the bike is amazing. I am a mountain biker that needed/wanted a bike to ride on gravel for the days the trails are closed.

My concern with a 1X was that i would run out of low gear 40T front 11x42 cassette (Shimano GRX 600). Sometimes on flat ground and always on down hills, I spin out and need more low gear. Does anyone have any experience with ethirteen cassettes? thinking about changing cassette to 9x42 and putting a 42 oval up front. Is the 9 with a 42 oval overkill (instead of the 40T) and too much cowbell? I have a 34 oval on my mtb and sometimes miss the climbing gear, but, am in GA and have been able to manage.

any input is appreciated.

shoota 

You're running out of high gear, not low gear. Nice bike btw, I love BMCs.

What cassette you can put on depends on your freehub. If it's just a standard 11s Shimano/Sram freehub then the smallest cog you can go is 11t. (Unless e*thirteen uses some kind of trickery, but I think their 9t cassettes use an XD/XDR driver. Feel free to correct me if I'm wrong here.)

How do you feel about your 40-42 low gear? If it's too low then an easy fix is to just put a bigger chainring on.

The obvious answer to fix all of this is to go 2X.

Twenty9er

Thanks for the feedback. I will need to look into the driver and not sure if it is compatible, but, it claims to be compatible with any drivetrain.

I wish I could go to a 2X, but, the BMC is only able to run a 1X, which was my only hesitancy in buying the bike. I guess easy fix is start with the larger chain ring and see if I need more gear.

The warbird was my other choice, but, couldnt find one local and am not a very patient person.

zen_

The only cassette with a 9t cog is the new Campangolo Ekar, which is in no way compatible with 11 speed GRX (Ekar is 13 speed, and uses a totally different hub / body).

If the hub on your wheels can use a SRAM XDR body, you could use a SRAM 10-42 cassette to get ~10% more top end without sacrificing climbing gear. Changing the front ring to a 44t would accomplish the same top end, at the expense of some climbing gear.

Edit - If your URS has a DT Swiss wheelset, then getting an XDR driver body will be no issue if you wanted to use the 10-42 SRAM cassette.

mstateglfr 

This all day. A bike that has the gearing range you want/need just makes sense.

Twenty9er

According to EThriteen, they make a 9-34, a 9-39 and a 9-42 called the XCX Plus 11 and says it is compatible with Shimano and SRAM 11 speed drivetrains.
My wheelset is Mavic (Shimano GXR derailleur). It seems like this might be a good option and can add a 42 oval if i need even more high gear.

shoota 

None of that says anything about what your current freehub is. It's probably a standard Shimano/Sram freehub, e*thirteen cassettes utilize an XD driver. You need to be SURE of your current freehub.

zen_

I wasn't aware of that EThirteen 9-42 XD cassette, so I stand corrected.

Gearing is in the same boat as saddles though; at the end of the day, what you need is very personal. If you plug in that 9-42 cassette to a gear calc, there is a big hidden trade-off with what I would consider "cruising" gears (13-20 MPH), in that you end up with an 18% jump between the 17t and 20t cogs, which for most riders would be high use gears with a 40t ring. That would not bother some riders, while others would find it extremely frustrating on the road, or flatter sections of gravel.

Twenty9er

I appreciate everyone's input, as gravel is new to me. I know its all bikes, but, each has its nuance and its definitely a a learning curve. I am starting to understand the importance of cadence, that baggy pants get hung up on my seat and make me feel slow and i look ridiculous wearing a helmet with a giant visor when riding down the road.

I forgot that once I bought the bike I start replacing stuff on it, like i have on my mtb's. I guess the more you know the more you "need".

Thanks again for your comments and look forward to learning about and getting more into the gravel.

rosefarts

So I run 40x 11-42 on my bike. It certainly does run out of high gears but on dirt, it doesn't matter because I'm tucked and not pedaling.

My new bike will have 44x 11-46. Similar climbing but a wee bit more high gear. I anticipate switching it to 42, but the used group came with 44 and I'll run it awhile.

My wheels do not have an XD freehub available, so I'm stuck with shimano. I might mess around with 38x 10-42 if I ever need a second wheelset.

For actual riding, 90% dirt in foothills areas of southern Colorado, occasional wind, and mostly dry, I rarely find myself cruising in the 11. Maybe for a moment here or there. Focus on your middle cassette cruising gears and your climbing. The gears used at the highest speeds are actually the least important.

jp911

I've been through this with my wife's gravel bike. Started with a 38 tooth chainring, stepped to a 40, and then ended up with 42. Cassette stayed the same at 11-42. The 1:1 climbing gear is sometimes not enough on really steep dirt, but the 42 x 11 is perfect for cruising on the road (to get to the dirt).

rosefarts

So at 42x11, at 80 rpm, assuming 700x40 tires, it's 24mph.

Kinda right where you'd expect an organized and fit group of average (cat 3-4) racers on road bikes to be. Or a solo fit triathlete on their blade bike. Before the hills.

That's going back to my statement earlier about worrying more about the middle of the cassette. I think very very few of us can sustain that on a gravel bike. Certainly not as a pavement cruising pace on the way out of town.

Props to your wife if she really is doing that. I suspect if she is, that she's got some serious racing chops that kinda would disqualify her from this everyman discussion.

jp911

My wife is sitting here smiling from your compliment, but she is definitely not a racer. I should have clarified that the 42 x 11 is a good "max" gear for her on paved road or very well-groomed gravel.

msu2001la

A gravel bike isn't usually a good choice for fast group road rides, so I'm always a bit confused as to why this situation is often seen as a limiting factor when considering gearing for gravel bikes.

I have used my gravel bike for road group rides, running a 42x11. This gearing is fine on flat roads, but definitely not enough to sprint off the front, and also may not be enough to stay with the group on long descents or flat road speeds above 25-30mph.
I've never rode in a situation on gravel where I needed more than a 42x11, but I mostly ride in flat areas and my gravel riding is usually solo and/or more casual.

unterhausen

42-11 is higher than the classic 52-14, which was the most common high gear for most of cycling history until the late '70s. I have gone to 46-11 on the road, and I do occasionally use that gear.

I have never spun my 42-11, even on the local wednesday night gravel world championships, which finishes downhill.

I would like 2x, but the industry doesn't seem inclined to give me what I want without some compromises. Low end GRX is ideal, but I would rather have a nicer crank.

Russ Roth

Ran into this with setting up new gravel bikes for my wife and I, current ones are 46/32 with 11/34 cassette which has been fine for us but we're going for more aggressive offroad gravel rides and the new frames will be coming with 73mm BB spacing. I just ordered a couple of clearance truvative XO cranks which are more then we need but were less then the only x7 I could find. Had to go sram/truvative since shimano only offers a 38/28 which I couldn't find while the XO comes 39/26 and I'll be changing the 39 to a 42. Couldn't find even a 40t shimano chainring to swap onto a Deore through XT crank so no go there. My goal is to keep a tighter cassette and we'll be using our current 11-34 cassette with the later possibility of a 36. Although I know I'll run into times that the 42/11 won't be tall enough I'm accepting the tradeoff for the steeper and longer climbs we're looking to do and the need to not exceed a 16t jump for better shifting quality and balancing it against having crazy cassette jumps when spinning along.

rosefarts

This really comes down the actual terrain you are planning to ride.

In my locale, climbs can be steep and long. Usually ok on 40x36 but I do like the option of 40x42 if needed. The descents are long and steep, but due to sand, washboards, rocks, ruts, and switchbacks, the really tall gears just don't get used. When I'm going over 30mph, I usually tucked and engaged in heads up riding so I don't hit a deer, cattle guard, or redneck. Not much pedaling there
I never pack for overnight, just day trips.

That's where I base my opinion.

I could totally see making full use of a 48/32 x11-36 in better maintained roads.

Rather than continuing to zealously push my ideas, what are your plans for the bike. What will average days look like and what will your worst days look like?

mstateglfr 

Praxis Zayante 48/32
Praxis Zayante Carbon 48/32
Shimano RX810 48/31
Easton EA90 46/30

Any of these could be viewed as nicer than low end GRX...

xseal

or get a Rotor crank with Power2max spindle with GRX spacing. Another alternative.

zen_

FSA also has a wide selection of 48/32 and 46/30 cranks, although which ones are better than the 46/30 GRX crank is debatable. They also have powerbox crank options, which (correct me if I'm wrong), is the only spider based power meter for those chainring sizes.