Granny Gear Inches: Ride Now, Save Your Knees For Later

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It’s not uncommon to hear about a cyclist being sidelined by a knee injury. A crash is often the benefactor of such turmoil. However, riding long hours with a heavy load can also wear on your knees — if not immediately, over time.

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Cycling can dish out a lot of stress on knees. Even more so while bikepacking — which usually involves extended riding time on a bike loaded with gear. As one would expect, many knee problems arise from bike-specific issues like saddle height and setback, cleat position, and improper bike sizing. Others are based on intensity, such as increased distance and duration, and using high gearing and low cadence. Either way cyclists’ knees are among the most vulnerable joints for repeated stress injury, and it’s not uncommon to hear of a rider who’s had to resort to knee surgery in their 40s and even 30s. So what can we do to prevent such a horrible sofa sentence? For starters, a proper bike fit is paramount. Another preemptive strategy, especially for those of us who like to frequent steep and rocky trails, is to have a gear ration that features a more than adequate granny gear. Spinning can be the key to keeping stress off the knees during a nasty climb, particularly important in the latter half of a big day.

Advocate Cycles Lorax Review, Gravel Bikepacking

So what’s a good granny gear?

Naturally it’s different for everyone. The likes of Jay Petervary and Josh Kato might not require the same granny gear as a skinny guy with bird legs (such as myself). It also depends on how much you pack, and where you ride. An expedition bikepacker heading to the Himalayas will have very different needs than a racer over relatively flat terrain. Proper gearing is something you just have to feel out based on the situation, as well as your own skill, strength and biomechanics – though starting low is never a bad idea. Know what gearing works for you and make a note of it to have as reference when purchasing a drivetrain or fine tuning your existing setup.

How many gear inches is yours?

To start, let’s talk a little bit about the system of measurement. Gear inches is one of several relative measures of bicycle gearing. It’s basically derived from a formula and provides an indication of the mechanical advantage of different gears. Values for gear inches typically range from 18 (very low gearing) via 70 (medium gearing) to 125 (very high gearing); as in a car, low gearing is for going up hills and high gearing is for going fast. Essentially to calculate gear inches, use this simple formula:

Gear Inches Equation - Gear Inches = Wheel Diameter X (Chainring Teeth/Rear Sprocket Teeth)

An equivalent system customarily used by continental European cyclists is metres of development, which measures the distance travelled with each turn of the crank. That is, metres of development is calculated using the same equation replacing inches in diameter with meters of circumference. Thus gear inches and development differ by a factor of π times imperial-to-metric conversion. To convert from gear inches to metres of development, multiply by 0.08 (more precisely: 0.0254π).

How to find your wheel diameter.

Note that the wheel diameter in the above equation isn’t really the rim diameter; it’s the actual diameter of the mounted and inflated tire. Of course they are always different, and while this isn’t exactly accurate, here’s a simple chart with diameters in millimeters and inches. For the sake of brevity, this is limited to popular tire sizes that might fall into the bikepacking category. For additional sizes, check out this chart.

  • 700c x 35mm tire 27.2″/.692m
  • 700c x 38mm tire 27.5″/.698m
  • 700c x 40mm tire 27.6″/.702m
  • 700c x 42mm tire 27.8″/.707m
  • 700c x 45mm tire 28.0″/.712m
  • 29er x 2.0” tire 28.5″/.724m
  • 29er x 2.2” tire 28.9″/.734m
  • 29er x 2.4” tire 29.3″/.744m
  • 29er x 2.8” tire 30.0″.763m
  • 29er x 3.0” tire 30.5″/.774m
  • 27.5 x 2.2″ tire 27.4″/.696m
  • 27.5 x 2.4″ tire 27.8″/.706m
  • 27.5 x 2.8″ tire 28/5″/.724m
  • 27.5 x 3.0″ tire 29.0″/.736m
  • 27.5 x 3.8″ tire 30.6″/.777m
  • 26 x 2.0″ tire 26.0″/.661m
  • 26 x 2.2″ tire 26.4″/.671m
  • 26 x 2.4″ tire 26.8″/.681m
  • 26 x 2.8″ tire 27.5″/.699m
  • 26 x 3.0″ tire 28.0″/.711m
  • 26 x 3.8″ tire 29.6″/.752m
  • 26 x 4.8″ tire 31.6″/.803m
  • The best granny gear, bikepacking bike touring
  • Marin Pine Mountain 2 Review, 27.5+, 650+, B+
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OK, so really, what’s a good granny gear?

Again, different strokes for different folks — literally — but I’ll share what I’ve found. To me, when bikepacking, that magical number falls around 19 gear inches or under — specifically for a mountain bike destined for steep terrain and trails. This number differs on a gravel bike as there is usually less tire resistance and rotational weight. To illustrate, here are five bikes that I’ve ridden in the past 8 months and what their granny gear translates to in gear inches. Each shows the bike, wheel size, and drivetrain on the left, then the granny gear ration (front x rear) and gear inches.

  • Salsa Pony Rustler, 27.5+, 1×11 (30x42t) 20.7 gear inches
  • Niner RLT 9 Steel, 700c/35mm, 2×11 (36x32t) 30.6 gear inches
  • Surly ECR, 29+, Rohloff (34txRohloff 14s) 18.1 gear inches
  • Surly Krampus, 29+, 2×10 (22x36t) 18.6 gear inches
  • Marin Pine Mountain 2, 27.5+, 1×11 (32x42t) 22.1 gear inches

The ECR/Rohloff combo has the lowest gearing. And while 1st isn’t the most frequently used gear on this bike, there have been plenty of times where it came in handy, such as the High Atlas in Morocco and the Transnevada. Conversely, the Marin Pine Mountain at 22 gear inches was a little hard on the old knobbies. A 30t chainring would have brought it to the same level as the Pony Rustler, and made it more suited for the steep terrain that the Altravesur route dished out. The Niner RLT 9 Steel was absolutely brutal on the steeps; but pretty good for going fast on flat terrain.

For reference, let’s take a look at the high gear to add perspective to the overall range of each of these bikes and drivetrains.

  • Salsa Pony Rustler, 27.5+, 1×11 (30x11t) 79.1 gear inches
  • Niner RLT 9 Steel, 700c/35mm, 2×11 (46x11t) 113 gear inches
  • Surly ECR, 29+, Rohloff (34txRohloff 14s) 95.08 gear inches
  • Surly Krampus, 29+, 2×10 (36x11t) 99.8 gear inches
  • Marin Pine Mountain 2, 27.5+, 1×11 (32x11t) 84.4 gear inches

The 2×10 offers the widest range of gearing which is great for a grueling expedition. For the sake of comparison, how about a classic 26×2.2″ mountain bike with a 3×9 MTB drivetrain, let’s say a 42-32-22 crankset and 11-32 cassette? The granny gear would be 18.15 and the high gear would be 100.1.

  • Joachim Rosenlund

    Or you ride 2×11, with a White Industries crank and a 11-42 cassette.

    The White Industries crank can take on (at least) a 20-tooth gap so you could do a 46/26 (or even 24) – 11/42 giving you a greater range the all the other mentioned possibilities! :-)

  • Smithhammer

    Solid article, Logan. And timely for me, since I just put a 40t cog on my Fargo for long, loaded climbs (28x40t = 19.95 g.i.)

    Interestingly, I just applied the same formula to the GX 1×11 drivetrain on my Hayduke (30x42t = 20.7 g.i.) – less than one gear inch apart.

  • Mbanzi

    Great article! I did the same calculations a while back and came up with the same granny of 18.6gi on my Krampus with a 36/22+11-36 combo. Using a 11-40 Sunrace cassette or Wolftooth cog would bring it down to 16.8gi.

    1x just isn’t viable on 29+ for bikepacking (for a normal cyclist) unless you go to SRAM Eagle, or have a direct mount crankset (like the Race Face AEffect or SRAM X-SYNC) that can take a smaller than 30t chainring.

    For 27.5+ 1x is more feasible, especially if you go 11 speed with a Wolftooth 45t cog, a 30+11-45 will give you 19.3gi. The new XT 11-46 cassette will work even better at 18.9gi. Or, once again, get a smaller than 30t chainring.

  • Anyone else thought of putting on a 64bcd inner ring without the front shifter. All of my 1x crank a old triples. Because it doesn’t take physic to see them coming, I’ll manually move the chain to the inner ring at the bottom of the longer slogs.

  • Cephalopod

    Good info in this article. I find it odd that people don’t obsess about gear ratios more…
    Minor correction: metres of development uses the circumference of the wheel, not the diameter.

  • Daniel Pastrana

    just to clarify, what was the size of the rear sprocket on your Rohloff, 16 tooth? Thanks for the great article!

  • DamagedSurfer

    Great post! Pride comes before the surgeries!

    I find many of the gravel bike offerings to have incomprehensibly high gear ratios for their intended purposes. And truly, for mixed terrain gravel/road bikes, I find a 1x to be silly as you sacrifice way too much on either the high or low side. Seriously how difficult is it to adjust a screw on a FD? What do they weigh – all of 50 grams? It seems in the rush to go light we as riders have abandoned good sense at times. When I built up my custom cross bike I went with a 28/44 White Industries crank paired with a Praxis Works 11/40 cassette (10 spd). This gives me ample gearing for loaded touring both on and off road. Except for all the most impossibly steep stuff, I never need the granny unloaded, but again, it’s there when I need it.

    For reference I’m 6’1″ 190 pounds and ride 6 days a week via commuting, mountain biking, gravel sessions, and bikepacking. I would consider myself a fit, strong rider, probably like most riders :), but still having a good granny is essential to protecting your knees. I’m 33 now and want to keep riding until I pass from this mortal life to eternal bikepacking bliss. I’ve met too many riders with injuries due to repetitive stress rather than accidents.

  • Wm Coe

    Thanks for the great post. This type of info really helps a newb like me, keep em coming.

  • Chris Leydig

    Bike nerd article. Love it! My fleet is all 9 speed; for bikepacking abroad it seems best (in lieu of Rohloff). Using a 22/36 11-32 combo on my 26+ Troll and so far it’s been perfect

  • patrick martin

    Thank you

  • Lewy

    I saw this idea a few months back

    My Krampus and my Soon to be ECR will only have 1x cranks so I can’t do this.

  • Yeah, that certainly makes cassette replacement feasible… And you can probably rely on classic tools found in even the most primitive bike shops…

  • Thanks Wm!

  • Yeah, I agree. I truly think 2×10 is the way to go for bikepacking. However, 1x simplicity is kind of nice.

  • Hey sorry for the delay… Getting caught up after being out for a few days. Yes, it’s 16t.

  • Thanks Lewy, that’s exactly what I’m thinking. I’m gonna go out to the garage & do it now while it’s raining.

  • matt

    for bikepacking I reckon you need under 19 at one end and above 110 at the other but that type of range is becoming terribly unfashionable. Once rider and gear get above 95kg you might want to expand that range even further!

  • DamagedSurfer

    Hi Logan,

    My comment was more directed at using a 2x for mixed terrain type bikes in which you will frequently be on pavement. I for one would miss the higher gearing a 2x allows in that scenario. Regarding mtb’s and bikepacking in general, I’m starting to think I’ll try a 1x system, especially now that I’ve added a dropper to my hardtail 29er. The only problem is that Shimano Deore XT is so damn reliable I can’t justify removing it and switching it out until it breaks down.

  • Derek Britton

    I was able to get 18.6 on the low end and 106.4 in high gear. 42t/28t SRAM X5 Crank paired with an 11-36t XT Cassette that I modified with the Wolftooth 42t + 16t cogs. Now it’s an 11-42t cassette with the SRAM X5 crankset. Great combo to use for my gravel/CX adventure bike build

  • nice. That’s a great range…

  • skunk ape

    Swapping the cassette on my RLT 9 for a 11-40 XT with the help of a Wolf Tooth Roadlink got me down to 24.5. Much better but still not low enough IMO.

  • Nice. Yeah, I just got done with a big trip on a 700c 11×42 with a 34t in the front and it was perfect with a light load…

  • Frank Z

    No problems with the front derailer with a 20t gap?

  • Dwight

    Awesome info!! I stumbled upon you site looking for info on running a 42 cog in rear, I have been trying to sort out whether the Sram X5 rear der. will handle 32 chain ring and 42 rear der, If anyone has experience with this set up would like to hear from you. There is a lot of supporting info that it will work – of course Sram denies this and claims 36 tooth cog is max. All the info on protecting you knees is spot on, The knee is like a large lever with the patella (knee cap) taking the impact of knee extension as the fulcrum. The Italian research indicates up 700 psi of force can be exerted (see Peter Sagan’s quads).

  • Fe

    I want to make by crossbike more mountain friendly and have a question. Maybe someone knows a solution?

    Current setup:
    – Aivee Edition One road rear hub
    – SRAM Rival 22 group (11-speed) with medium size derailleur
    – SRAM Rival PG-1130 cassette (11-fach) 11-32

    My plan:
    11-40 tooth or 11-42 cassette
    Wolf Tooth Roadlink

    My questions:
    Which of the following (MTB) cassettes can I install on the hub and which will work with the road SRAM Rival 22?
    – SRAM MTB cassettes with 11-40 teeth
    – Sunrace CSRX8 RX 11-Speed Wide Ratio Cassette 11-40
    – Shimano Deore XT 11-40t Kassette
    – Shimano XT CS-M8000 11-40t Kassette

    Someone told me that I can install any of these but that I need a 1.85mm spacer for the MTB cassette even if this is 11-speed. Does that mean the cassette is smaller? Will that cause performance issues?

    Looking forward to your recommendations.

    Best Regards

  • Don Thompson

    I have a 2017 Salsa Cutthroat that has a 38t chainring and an 11-42 cassette. I have Derby carbon rims with 29er x 2.2” tires. This gives me a low gear of 26.5” and a high gear of just under 100”. It’s fine for most of my riding—gravel in Iowa. We have some steep hills on our gravel roads, but they climbs are not too long and I can stand and get up all of the hills I ride. I’m planning on the Adventure Cycling Intro to Dirt Tour in Montana this summer to become acquainted with bikepacking. After that, I plan to do more bikepacking trips in the U.S., but most will be in Nebraska, South Dakota, Wisconsin, etc. I don’t think I’ll return to the mountains for bikepacking. My bike shop recommends a 36t chainring. That gives me a low gear of 24.77” and a high gear of 94.58”. I think that’s gearing I’d benefit from riding gravel in Iowa—I’m a fairly strong rider, but I’ll be 69 this summer, so I’m not one of the young guys hammering up the hills. My big concern is that my 25 lb. bike is a 48 lb. bike fully loaded with my gear in frame packs. Should I try an even smaller chainring to get my low gear down to 20 inches or less for bikepacking only?

    Any advice appreciated!

  • Chris Tsaki

    I assume you have a big cage real derailleur. If its a SRAM Apex rival force it should work with the XT46T cassete which has a big jump at the end (think 36-46). This might be the best option for you and the XT cassette is very cheap and durable. Have a Sequoia and i want to switch to 38T chainring and the 46-11 cassette and should be very compfy for loaded offroad climbs

  • Whoops, missed this, sorry. I used a 34T on a Cutthroat for our Cuba trip and it worked well (used a Wolf Tooth Camo system to go that low)––You could also check out the e*Thirteen TRS+ cassette (9-46) if you really want to up the range (511%).

  • Don Thompson

    Thank you—I do have a long cage rear derailleur. Will look at this option!

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