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46/30 vs 48/31 gravel chainrings: which Shimano GRX double to pick
GRX 46/30 or 48/31: the real gear gap, weight, price and parts.
At a glance
Short answer: Pick 46/30 if you climb a lot, carry luggage or ride slower gravel. Pick 48/31 if you spend time on fast roads, in groups or racing, and run out of gears on descents. The gap is small: about 4% at the top and 3% at the bottom, less than one click on Shimano's 11-36 cassette.
Who it's for: riders choosing between Shimano GRX double cranksets, or wondering whether swapping one for the other is worth the money.
Want to check your own setup? Our gear calculator has a compare view: put 46/30 in A and 48/31 in B with your cassette and tire.
The two cranksets at a glance
Shimano's 12-speed GRX double comes in two chainring pairs. The rings are "chainrings": the toothed rings on the crank. 46/30 means a 46-tooth big ring and a 30-tooth small ring.
| 46/30 (FC-RX610-2) | 48/31 (FC-RX820-2) | |
|---|---|---|
| Group | GRX RX610, 12-speed | GRX RX820, 12-speed |
| Shimano's pitch | "Ideal for steep climbs, and slower-paced endurance rides." | "Suited to flat or rolling courses, racing, and sustained high speeds." |
| Weight (170 mm arms, no bottom bracket) | 811 g | 718 g |
| Crank arm lengths | 165, 170, 172.5, 175 mm | 160, 165, 170, 172.5, 175 mm (spec chart) |
| Chain line / Q-factor | 47 mm / 151 mm | 47 mm / 151 mm |
| Bolt pattern | 110/80 mm | 110/80 mm |
| US MSRP (Shimano, 9 Nov 2026) | $180 | $280–$290 (Shimano US list price range, 9 Nov) |
Chain line is how far the chain sits from the bike's centre; Q-factor is the distance between the pedal mounts. Both are identical, so the two cranks sit the same on the bike.
In the box: Shimano's spec chart lists the crank fixing screw as included. The bottom bracket is a separate part. Shimano recommends BB-RS501 (threaded) or BB-RS500-PB (press-fit) for the 46/30, and SM-BBR60 or SM-BB72 for the 48/31.
What the gear difference actually feels like
Gear figures below use 700x40 mm tires at 90 rpm, a steady, normal pedalling speed. The ratio is chainring teeth divided by cog teeth: lower is easier.
| Setup | Easiest gear | Speed at 90 rpm | Hardest gear | Speed at 90 rpm |
|---|---|---|---|---|
| 46/30 + 11-34 | 30x34 (0.88) | 10.5 km/h (6.5 mph) | 46x11 (4.18) | 49.8 km/h (30.9 mph) |
| 46/30 + 11-36 | 30x36 (0.83) | 9.9 km/h (6.2 mph) | 46x11 (4.18) | 49.8 km/h (30.9 mph) |
| 48/31 + 11-34 | 31x34 (0.91) | 10.9 km/h (6.7 mph) | 48x11 (4.36) | 52.0 km/h (32.3 mph) |
| 48/31 + 11-36 | 31x36 (0.86) | 10.3 km/h (6.4 mph) | 48x11 (4.36) | 52.0 km/h (32.3 mph) |
What that means on the road:
- Top end. 48x11 is about 4% harder than 46x11. At 90 rpm that is roughly 2 km/h more before you spin out.
- Climbing. 31x36 is about 3% harder than 30x36. You will notice it most at the end of a long climb, not at the start.
- Next to a cassette shift. On Shimano's 12-speed 11-36, the smallest jump between neighbouring cogs (14 to 15 teeth) is about 7%. So swapping the whole crankset changes your gears by less than one rear click.
- Front shifts. Dropping from the big ring to the small ring makes pedalling about 53% easier on 46/30 and 55% on 48/31. They feel almost the same.
One thing worth knowing: a 48/31 with an 11-36 cassette (0.86) is easier at the bottom than a 46/30 with an 11-34 (0.88). If you want the bigger top gear without losing climbing gears, the cassette is the cheaper lever.
Which one to pick
| If you want... | Pick | Why (gearing) |
|---|---|---|
| The easiest low gear in Shimano's 12-speed GRX double lineup | 46/30 with 11-36 | 30x36 is the lowest ratio of the two |
| Similar low gears, with a harder top gear | 48/31 with 11-36 | Low end within about 3% of 46/30; about 4% more on the top |
| More speed at 90 rpm before the cadence ceiling | 48/31 | About 2 km/h more in the hardest gear than 46/30 (gear calculator, 700x40) |
| The lower Shimano US list price | 46/30 | $100 to $110 less at MSRP (9 Nov) |
| The lighter crank (170 mm, no BB) | 48/31 | 93 g lighter on Shimano's spec charts |
If you never use your hardest gear today, a bigger big ring mostly adds cost.
Switching from one to the other
Both 12-speed cranks work with the same rear derailleur and front derailleur in Shimano's own lineups:
- Front derailleur: FD-RX820 is listed for both. Its spec chart says top gear 46-48T and total capacity 17T. 48 minus 31 is 17, and 46 minus 30 is 16, so both fit.
- Rear derailleur: RD-RX820 lists a maximum front difference of 17T, total capacity of 42T and a largest cog of 34T to 36T. Total capacity is (big ring minus small ring) plus (largest cog minus smallest cog). 48/31 with 11-36 is 17 + 25 = 42, right at the limit. 46/30 with 11-36 is 41. Our derailleur capacity checker does this sum for you.
- Cassettes: Shimano's 12-speed GRX double lineups list an 11-34 and an 11-36 (CS-HG710-12) cassette.
- Chain: going up a ring size can mean a longer chain. Re-check with the chain length calculator.
For the full parts picture, see our Shimano GRX 12-speed compatibility guide.
On 11-speed or 10-speed GRX?
The same two ring pairs exist on older GRX:
| Group | 46/30 crank | 48/31 crank |
|---|---|---|
| GRX 11-speed | FC-RX600-11, 817 g | FC-RX810-2, 710 g |
| GRX 10-speed (RX400) | FC-RX600-10, 821 g | Not offered |
On 11-speed, FD-RX810-F is listed for top gear 46-48T, so it covers both. RD-RX810 lists total capacity 40T and a 34T largest cog: 48/31 with 11-34 is 17 + 23 = 40.
On 10-speed RX400, the FD-RX400-F spec chart lists top gear 46T and total capacity 16T. A 48/31 sits outside both figures, so it is not a drop-in swap there.
Related on Pedal Brief
- Gear ratio calculator
- Derailleur capacity checker
- Chain length calculator
- Shimano GRX 12-speed compatibility
- Road and gravel groupsets 2026
Sources and notes
Where the sources disagree
- 11-30 cassette with GRX 2x12. Shimano's story "A Guide to SHIMANO 1x and 2x Gearing Setups for Gravel" says: "GRX offers two chainring pairs (48/31T and 46/30T) that can be combined with SHIMANO 12-speed cassettes (11–30T, 11–34T, 11–36T)." The RD-RX820 spec chart lists a minimum low sprocket of 34T, and the RX610 and RX820 2x12 lineup pages list only 11-34 and 11-36 cassettes. We left 11-30 out of the main text.
- FC-RX820-2 crank arm lengths. The productinfo spec chart ticks 160, 165, 170, 172.5 and 175 mm. Shimano's en-NA product page says: "The 2x12-speed crank utilizes a 48-31T chainring and comes in 170, 172.5, and 175 mm crank arm lengths." The table shows the spec chart figure. For FC-RX610-2 both sources agree (165 to 175 mm).
What we could not confirm
- Swapping rings between cranks. Both cranks list a 110/80 mm bolt pattern and Shimano lists replacement rings for each (for example "Chainring 48T for FC-RX820-2" and "Chainring 46T for FC-RX610-2" on the en-NA product pages), but we found no Shimano statement that 48/31 rings are approved on the FC-RX610-2, or the reverse. Treat it as a crankset swap.
- A single US MSRP for FC-RX820-2. Shimano's dealer-locator page displays "$280 - $290" rather than one price. The dealer-locator pages are run on Shimano's subdomain by a local-shop stock service; we found no Shimano direct store price.
- FD-RX610 and RD-RX610. Their productinfo pages returned "No results" on 9 Nov. Shimano's RX610 2x12 lineup lists FD-RX820 and RD-RX820, which is what the main text uses.
- Shimano's own speed examples. Shimano's story gives 35.4 mph for 48x11 at 100 rpm but doesn't state the tire size, so we didn't compare it with our 700x40 figures.
- Older-crank weights come from the same spec charts (170 mm arms, no bottom bracket), so they compare like for like with the 12-speed figures.
Sources
- Shimano productinfo spec charts: FC-RX610-2, FC-RX820-2, FC-RX600-11, FC-RX810-2, FC-RX600-10, FD-RX820, FD-RX810-F, FD-RX400-F, RD-RX820, RD-RX810, CS-HG710-12
- Shimano lineups: GRX RX610 2x12, GRX RX820 2x12, GRX RX820 2x12 Di2
- Shimano product pages: FC-RX610-2, FC-RX820-2
- Shimano US MSRP (dealer locator): FC-RX610-2, FC-RX820-2
- Shimano: A Guide to SHIMANO 1x and 2x Gearing Setups for Gravel
Disclosure: Pedal Brief may earn a commission if you buy through links on this page, at no extra cost to you. This version has no affiliate links. We have not ridden these cranksets back to back. Specs and prices come from Shimano; gear figures are our own arithmetic from the tooth counts.