Spoonrobot 

Anyone riding gravel/dirt events on a single speed cross bike?

I'm thinking about doing a 100 mile gravel ride running my bike as single speed because it would be a good way to knock out a singlespeed century and a gravel century all in one go.

Any suggestions for ratio? I'm planning to run Kenda Happy Medium 700x40c tires and thinking about running 46/18 which would put me right at 71 gear inches. Maybe a little low but I've done some hilly road alleycats on 50/18 (74 inches) and found it a good ratio for pavement and 700x23c tires. So a little lower should work for relatively flat, compact dirt/gravel.

mstateglfr 

Holy goodness I cant imagine doing a 100mi ride on gravel with a single speed.
If I did that, I would need time to map out a route that would be relatively flat...so like a river valley and ride the same loop a handful of times.

On a couple of gravel routes I ride, I try to stay in the same gearing for as long as possible when starting out. 46/17 is the gearing and I manage for about 5mi, give or take. The elevation is very gradual with roads that are 15-50' of climb over a mile. After about 5mi, its becomes time to start using what I spent money on.

Barrettscv 

+1


A 36 & 17 gearset with a 700x40 would provide 58 gear inches. That would provide 15mph at an 88 rpm cadence, and 17mph at 98 rpms.

Expect to walk the steeper hills with more than a 10% slope.

.

rm -rf

What kind of gravel road? I've ridden on well maintained roads with packed, pea sized gravel, and on state forest roads with some loose, inch sized gravel on the surface.

The pea gravel roads would be reasonably fast with your 40c tires. How steep and long will the hills be?

But I gave up on a long 10-12% grade with the large, loose gravel. I was riding my 30-29 low gear, too. That grade would be quite easy for me on a paved road. Even the 4% or 5% sections were very slow going, and hard work.

A shorter test ride on similar roads would be useful for checking the gearing.

rumrunn6

looks like a pretty standard cyclocross tire. I guess that form factor has some important features & benefits

Refreshing

In 2014 the first place finisher of the Dirty Kanza Half Pint was riding a single speed. Check out this article:

Dumping, Flatting, Sprinting, Roller Bombing and Horizon Hunting: A Dirty Kanza Half Pint Race Report?? - Cyclocross Magazine - Cyclocross News, Races, Bikes, Photos, Videos

However, no way in hell would I do it unless I was able to choose a gear based on first-hand-experience with the terrain and elevation gain.

ThermionicScott 

Sure, why not.



I've done a few gravel rides up to a metric on this bike (using 65"), but never what you'd call "competitively."

Spoonrobot 

Thanks for the reminder. I completely forgot I could convert inches into speed by rpms. Very helpful. No 10% hills, hell probably no 3% hills.

Here's the route. It's hardpack Alabama red dirt road, it's "gravel" but only in name. Usually just dirt with some rocks. Very flat, this type of terrain I can ride 18-19mph in a tight paceline, maybe 16-17 solo so I'll plan for that.

https://www.strava.com/routes/6046759

I've done a fixed gear paved century that averaged around 50 feet a mile and had a blast. I think I'll get a kick out of a gravel SS century too.

I'm more of a "parti-racer" nowadays anyway.

rm -rf

Wow, that seems perfect for a single speed bike. It would be very interesting to read your ride report!

palu

I typically run ~70-72 GI for paved centuries, but for gravel, I am down in the mid-low 60's (typically 61-63 GI). Dirt takes a toll on you, and it saps power. I'd gear down, personally.


EDIT: This dude did the DK with 39x17 (63-ish GI) and took 7th in SS and 69th overall in 2015 (in 2016, he moved up to 2nd in SS and 26th overall).


https://revoltingcogs.blogspot.com/20...ty-things.html

ksryder

Yeah lots of people do it, including on the DK200 (although none of them ever look like they're having much fun on the second half of the race). Seems like the guys I know always run a little bit easier gear combo than they would on pavement. Anywhere from 32-38 front and 16-19 rear.

50voltphantom

71 GI is huge, that's what I run for pavement. I did a 100k event with 3000' elevation at 64 GI and should've gone even lower to ~60. Spin to win. Right about 38x17 is what I'd target. Since 'cross season has started I've been riding 39x19, and while it's a little spinny, it's not as slow as you'd think, especially if you have any major hills to climb.

BIGDCYCLES

We have a group here in the Wichita area that ride coaster brake singlespeed. There is also a race series with a class for them.Lots of SS gravel riders around here as well. Most ride 50-60 miles but some ride century races and the Dirty Kenda 200.

CV-6 

If you have a rail to trail in your area, you have an excellent candidate for singlespeed gravel, providing they did not pave the trail. I ride the Katy Trail sometimes on a singlespeed. Considering the lack of elevation change, it's kind of a no brainer.

stdlrf11

I used to ride gravel on a single speed. I was running 48x17 on 700x32's. We'd only have about 2k worth of elevation over 60 miles or so. Nothing you couldn't sprint up. I would have died had we come across any big climbs.

sb88

Just done my first 2 CX races singlespeed - run 34:16 on typical October British courses - muddy, sharp bends, flat overall but steep bits are very steep. Gear has been perfect. I get passed cos I'm a semi-fit novice commuter on a steel bike in a series where wiry vets on £2k carbon bikes with tubs start at the same time as my race! The gear is the least significant variable, vs the fitness and experience of the other riders, the weight/stiffness of their frames and wheels and their ability to run lower pressures with better tyre setups. I'd finish in the same place if I had gears, or if they were all on SS. (About 2/3 down the overall leaderboard, but higher up the novices). I nearly ran 38:16 but tested it the night before and realised it made me stand to force my way up inclines too much. 36:16 or 39:17 might be suitable after a few races but consensus seems to be that a ratio just over 2:1 is good for SSCX. There's a skill to managing inclines without losing traction - obviously a low gear can make the wheel spin in gravel or mud but a slightly too high gear can mean standing on the pedals and causing wheelspin too...

phatfree

I rode a 12hr gravel race on a 42:18 with 40mm MSO's and I found the gearing to be perfect. In the end covered just under 180 miles.

mack_turtle

I am going SS on my next few gravel rides. I have a 29er hardtail with a 32x20 for trail riding. probably going for high 50s- low 60s for gear inches. with 29x2.1 tires, that should be something like 42x19, 40x18, 38x18... I would rather gear low enough that I can ride the hills rather than walk them and accept some spinning on the flats.