Is a single or double front gravel bike better?

Difference between front single and front double

Difference in gear ratio options

The difference between front single and front double is the number of gear ratios. A front single has only a rear gear shift, so the number of gear shifts is smaller. On the other hand, a front double has double the number of gear ratios because it has 2 rear gears.

However, it is not the physical number of gears that is important on a gravel road bike, but how many gear ratio options you have. A single front wheel does not simply mean that you have only half the gear ratio choices of a double front wheel.

Let’s compare gear ratios assuming 11-speed components.

First, the gear ratio of a front single with 11-speed rear and 11-32T sprocket.

Front	Rear	Gear Ratio
42	11	3.82
42	12	3.50
42	13	3.23
42	14	3.00
42	16	2.63
42	18	2.33
42	20	2.10
42	22	1.91
42	25	1.68
42	28	1.50
42	32	1.31

The gear ratio coverage range is from 1.31 to 3.82.

Next, the same rear sprocket is used with a double front gear ratio.

Front	Rear	Gear Ratio
50	11	4.55
50	12	4.17
50	13	3.85
50	14	3.57
50	16	3.13
34	11	3.09
34	12	2.83
50	18	2.78
34	13	2.62
50	20	2.50
34	14	2.43
50	22	2.27
34	16	2.13
50	25	2.00
34	18	1.89
50	28	1.79
34	20	1.70
50	32	1.56
34	22	1.55
34	25	1.36
34	28	1.21
34	32	1.06

The gear ratio coverage range is 1.06 to 4.55, which is wider on both the low and top sides, giving you a wider range of options.

However, a closer look reveals that the only difference with the front single is in the two top gears of 50-11 and 50-12, and the two low gears of 34-28 and 34-32, for a total of four gears. Other than that, the front single covers the same range of gear ratios, although there are large differences in gear ratios per stage.

Weight Differences

The front single has no front shifting, so the total weight of the component is lighter than the front double.

Let’s compare Shimano’s GRX-FC-RX810-1 crank for front single and 105-FC-R7000 and FD-R7000 for front double for road use.

Parts	Front Single	Front Double
Crank	644g	713.4g
Front derailleur	0g	95g
Total	644g	808.4g

Generally speaking, a single front is about 170g lighter than a single front. Considering that a 170g weight reduction in easily replaceable parts such as handlebars and saddles can cost several tens of thousands of yen, a 170g weight reduction just by reducing the front end can be called "cost-effective weight reduction.

In particular, since most gravel bikes are heavier than road bikes, a 170g weight reduction is significant.

Gravel road bike double front or single front?

Front double if you are mostly riding on paved roads.

A front double has a wider range of gear ratio coverage, which means that a front double is more runnable in the sense that it can cover both flat and hilly terrain. This is a major point for gravel bikes, where “drivability” is important.

In this sense, if you mainly ride on paved roads, it is better to use a front double for better drivability.

In addition, if you use the “synchronized shifting” of Shimano Di2 electric shifting, which is being used by an increasing number of users these days, the front shifting is done automatically according to the gear ratio, so the gear operation is almost the same as that of a single front shifting, and the disadvantages of a front double are covered.

If gravel and other unpaved roads are the main use, a single front wheel should be used.

On the other hand, on gravel and other rough terrain, there are times when you need to make instantaneous gear shifting decisions, so a double-front bicycle may not be able to shift into the appropriate gear instantaneously due to the complexity of shifting. If the rider is unable to shift into the appropriate gear, he may fall off the bike on a steep slope or fall off the bike on a steep slope.

This is one of the reasons why MTBs used for descending cliffs are increasingly adopting a single-front gearshift.

Double front shifting is also possible with Di2 “synchronized shifting,” but Di2 is an expensive component set, so it is not easy to install. If there are many situations where simple gear shifting is more advantageous, such as gravel, the advantages of front single can be used if Di2 is not used.

If the narrow gear ratio of front single is a problem, you can widen the coverage by switching to a component that covers front single and rear 11-50T, such as Sram.

The simpler front end also makes it easier to clean, which is a big advantage for gravel bikes, where the bodies tend to get dirty.

It is best to actually ride gravel to test which is best

The best gear for a gravel road bike varies depending on the road to be ridden and the rider’s leg strength. In this sense, it is best to try riding with standard equipment to get a feel for which is best.

If you are debating between a front double or a front single before purchasing a gravel road bike, we recommend that you go with a front double.

Converting a front double to a front single is a “removal job” and therefore less expensive to replace, but converting a front single to a front double requires the purchase of front double STI levers and front derailleurs, which are more expensive to replace.