I’m looking to set up my gravel bike for a flat race I have this summer but cannot seem to decide what would be better for my needs with my current options. Some background:
- Race is a mostly flat loop with a couple 3% avg climbs and some quick descents into a corner (not looking to pedal into a gravel corner at speed)
- Speed range from past top 10 finishers are 10-38 mph with about 20 mph average. The max being the quick downhill. Sustained speeds likely to fall between 12 and 30 mph.
- I want a tight spread most of the time and want to avoid large jumps in gearing.
- I want to be able to pedal at an optimum cadence on the false-flat downhills.
- Preferred cadence range is 90-100 rpm
My current gearing options are:
- 42T and 46T chainrings.
- 11-28T, 11-30T, 11-40T, 10-42T cassettes
- Shimano and XD drivers available
- 46/11 at 100 rpm gives 33 mph
- 46/30 at 90 rpm gives 11 mph
- 42/10 at 100 rpm gives 33 mph
- 42/42 will not be needed.
I stumbled across the 3T Bailout 9-32 cassette that’s heavily discounted now but I’m not entirely sure the 9t is even needed. I think my most used gear combo would be 42/15 or 46/17 and would like a tight group around those figures so that leaves the 10-42 out. I’m strongly considering the 46/11-30 but worry I’ll find myself running out of range in both directions.
Has anyone had much experience in this area that can offer some insight? I know for a fact I’m overthinking this, but having options makes me want to choose what’s best, so why not try to figure that out?
I can pedal comfortably to 50kph (31mph) on a 46x11. Not much else I can add sorry!
I’d personally go 42t x 11 - 36 or 11-32 but realise you don’t own these so would opt for the 11-30.
I’ve raced road and crits with a 46t on 1x, it seems a bit steep for gravel.
Have you looked at the downhill segment, how many of the race leaders are pedaling vs tucked in?
What rear derailleur do you have? I assume you’ve checked the range it can handle?
Yea it’s XT Di2. Handles the 10-42 no problem.
The downhill segments are mostly pedaled with the exception of one steep section into a corner.
I think I’d prefer to have more cadence selection at higher speeds. Seems like the steeper sections are 30s tops and I can grind it out.
Hi - midwestern gravel racer here. I run a 42 up front and 11-32 in back. I used to switch from the 11-32 for cross to the 11-28 for gravel, but these days I can’t be bothered. Even for some of the hilly races around here (ten thousand comes to mind) I’ve never wanted a lower gear, and I’ve certainly not run out of top-end speed even on long paved run-ins to the finish. So, if the race is really flat and you are less lazy than me, 42 and 11-28 sounds like a solid bet.
What race are you doing? Sounds fun!
Thanks! I’m going to be doing Rock Creek Roubaix and trying to get on the podium so my biggest concern is not being able to go fast enough. All the math points towards the 46t up front with my 11-30 cassette but I just wanted to be sure I wasn’t leaving range at home.
I will add that I do workouts on the flat bike path near my house and during hard vo2 intervals I’m typically in the 42/11 and occasionally shifting to the 10t and finding my cadence drops too much. So I feel the 42/11 for this race might be a tad too slow for attacking.
Oooh, that looks fun! Bummer it’s the same day as Crusher in the Tushar, or I’d be there. Also, hell yeah. Get that podium.
If it helps, I made a chart for you of speeds at varoius cadences on a 11-30 cassette with both 42 and 46t chainrings.
One thing I would consider here is that with the Shimano R8000 11-30 cassette, you get single-tooth gaps below the 15t which keeps things tight. If you want those tight jumps while cruising, running the 42t will bias you down towards the small end of the cassette a bit more. Of course, there’s no way around top speed. If you need that top-end, you need it.
Uh, yeah. Send it.
Woah thanks for all of this. So my comment on getting into the 10t is at the start my interval section of trail that’s a false downhill. Looking back through my history it appears I hit 30 mph top which is when I’m usually hunting for another gear past the 12t. Did this at 95 rpm.
The other intervals averaged around 25 mph at 95 rpm which would imply the 42/12 when I was using my 10-42t cassette the jumps were 10-12-14-… and I really disliked the jumps that low. So having single tooth jumps from 11-15 sound great.
The Shimano 11-28 and 11-30 all have the same 11-21t spread with the 11-25 having the Goldilocks 16t cog in there.
The reply feature doesn’t seem to be working…
I think it sounds like between now and July, you should throw on that 11-30 and try both chainrings to see how it feels. Hop on a fast road group ride to really put it to the test. If you pick the right (or maybe it’s the wrong) ride, people will get mad that you’re keeping up on a cross bike and pick up the pace on you.
You might check out the SRAM PG-1170 11-28 as well. It’s got single-tooth jumps 11-17, then a 19, then three-tooth jumps up to 28. Buttery smooth.
Yea definitely will be experimenting this summer. Really just seeing if I need to make a purchase prior to the race and seeing steep discounts (looking at the 3T 9-32) makes them appealing, but I think not needed. I’ll check out that SRAM cassette too, thanks.