Author Topic: Gravel bike  (Read 1050 times)

Gravel bike
« on: May 10, 2019, 11:02:21 am »
A ponderation in progress, but I thought I’d access the hive mind to increase the thinks applied to the problem.
Gravel bikes seem to be a crossover between MTB and road bikes, and while serious off roading is a major challenge on a bent, I feel that the trails accessed by gravel bikes would be likewise accessible on a suitably prepared bent.

I’m aware that various trike and 4 wheel thinks exist for exploring further afield, but wide track vehicle isn’t always compatible with narrower trails and a bicycle is so much more elegant don’t you think.
I’m thinking that the 20 inch wheels on my grasshopper would be an embugerance to transit on rougher stuff and so I’m thinking that a high racer might be a better option. But I see that as being s little to tender in the wobble direction for such applications, and so I’m developing the notion that a new configuration is required rather than the reapplication of an existing design.

So into the design discussion.
Obvious we want bigger wheels or better rolling, though whether we go fat tyre or 29er is a refinement to consider later. To get a lower CoG with a reasonably short wheelbase you’d have to straddle the front wheel, so perhaps front wheel drive. Or perhaps just a full-size front wheel with a smaller rear might allow a lower CoG. Rear wheel steering seems an obvious solution to allowing a close straddle of the front wheel, but I think that would be a step to far into weirdness, even for committed 'benteers. Seeding would, in any case, need to be hamster/tiller to keep the width manageable.

That’s as far as I’ve got with this thought experiment. What are your thoughts? Is it just a plain stupid idea, or have my ideas sparked a glimmer of neurological activity? Please do add your thoughts and let see where this goes.   
Sorting my life out, one shed at a time.

Re: Gravel bike
« Reply #1 on: May 10, 2019, 11:26:59 am »
I tend to think of my recumbent as something like a gravel bike - full suspension, 35mm tubes, tough hybrid tyres. Since we don't have "fire roads" in the UK it's hard to know exactly how rough a "gravel bike" is supposed to handle, but certainly I comfortably bomb down gravel towpaths / into forests and the like. Edit: I'm talking about an Azub Six, in line with Kim's post below.

I would definitely go high racer rather than low, just in terms of having a bit of margin for recovery - the biggest downside I've found compared to an upright mountain bike is that if you start losing it you have to react quite quickly or you're already on the floor. My current machine is 20/26 but I'd probably go 26/26 for a dedicated off-roader - this is a reverse of how I thought before buying it (less far to fall is an advantage) but now that I'm comfortable on the recumbent I'd rather plan on not falling off than mitigate the damage.

I'm not actually convinced that you need big wheels for their own sake - "better rolling" is more of a concern for road/TT bikes where you're going as fast as possible - but the height is vital IMO. We see this with upright gravel/mountain bikes too - they generally have a more upright riding position than road bikes, and that's partly about aero being less important but also about balance and being more able to correct when something goes wrong. Those concerns are the same for a recumbent, so IMO if you're trying to design a gravel one you probably end up with a semi-recumbent where the riding position is not a million miles away from a sit-up-and-beg upright. Of course that undermines some of the benefits of a recumbent, but you'd still have the comfort advantage at least.

Kim

  • Timelord
Re: Gravel bike
« Reply #2 on: May 10, 2019, 12:46:22 pm »
That’s as far as I’ve got with this thought experiment. What are your thoughts? Is it just a plain stupid idea, or have my ideas sparked a glimmer of neurological activity? Please do add your thoughts and let see where this goes.

I think that's basically what a Streetmachine (and other bikes in the same mould from Azub and similar) is; being a highly stable expedition tourer designed to cope with unmade roads.  Upright riding position means you can see the ground.  USS means you can sit forward and shift your bodyweight a bit on the technical bits, which I think is more useful than keeping the width down, except when dealing with Silly Sustrans Gates™.

The 20" front wheel is a compromise, but you need to be able to get a foot down, so riders of less than Dutch proportions don't have a choice.  24" might be possible, though, as presumably they make half-decent off-road tyres in that size for children's bikes.

I believe Ben of Kinetics fame once built up a spare Streetmachine frame (without all the racks and things) as a single-speed off-roader, and it worked surprisingly well.  Can't find the page he wrote about it.


I'd put the ICE Adventure in the same category, though obviously trikes aren't so good on singletrack.  The ICE Full Fat is a serious off-roader for mad people.



In practical terms, I'll happily ride gravel tracks on my Streetmachine, often with the full set of luggage.  What makes me nervous is mud.  Marathons have their limits, and if I'm serious enough about off-roading to use knobbly tyres I'll use my mountain bike.  While being able to handle some mild off-road is important for a touring 'bent, I still think DF bikes are the best solution for off-road riding.
Careful, Kim. Your sarcasm's showing...

Mr Larrington

  • A bit ov a lyv wyr by slof standirds
  • Custard Wallah
    • Mr Larrington's Automatic Diary
Re: Gravel bike
« Reply #3 on: May 10, 2019, 02:55:11 pm »
I saw some full-on "gravel bike" dual-26 machines more than 20 years ago in Denmark, so nothing is new under the sun, but my limited experience of riding gravel roads on a Speedmachine is not something I'd wish to repeat in a hurry, especially as it was the closing few km of a 200.  Higher is almost certainly better.
External Transparent Wall Inspection Operative & Mayor of Mortagne-au-Perche
Satisfying the Bloodlust of the Masses in Peacetime

Cudzoziemiec

  • Dormant but requires tea
Re: Gravel bike
« Reply #4 on: May 10, 2019, 03:01:42 pm »
I clicked on this thread without noticing it was in the Dark Side. I don't have any recumbent knowledge or thoughts but I can waffle on gravel bikes. I'll try to make my waffles dark side-relevant: "Would you like maple syrup or recumbent sauce with your waffles?"

As sometimes happens with niches, "gravel bike" has become a wide-ranging term. We'll leave aside the thorny question of whether it was a users' niche widened by marketing people or a meaningless term invented by marketing departments and given broader application by users. It covers everything from cyclocross bikes with tyres too wide for the UCI (ie more than 34mm) through mountain bikes with drop bars to fat-wheeled tourers. Do you see your recumbent gravel rides as speedy blitzes, gnarly berm bashing for thrills or longer adventures on the road less paved? Maybe all of these and a bit more besides?
At some point in the ride, you might find yourself in Osaka with Spanish speakers where you had expected Edinburgh talking Greek. This does not mean you are lost, or even off route.

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Gravel bike
« Reply #5 on: May 13, 2019, 08:41:58 am »
something like this perhaps?

https://cruzbike.com/products/q45
“Procrastination is the thief of time, collar him.” –Charles Dickens

Kim

  • Timelord
Re: Gravel bike
« Reply #6 on: May 13, 2019, 12:16:56 pm »
something like this perhaps?

https://cruzbike.com/products/q45

Wow, that's fugly.  Looks like it might do the job well, though.  Impressive if it fits 5'1" riders!
Careful, Kim. Your sarcasm's showing...

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Gravel bike
« Reply #7 on: May 13, 2019, 01:12:05 pm »
It's a Cruzbike, 'tis a thing of beauty and engineering wonder.  :P
“Procrastination is the thief of time, collar him.” –Charles Dickens

Re: Gravel bike
« Reply #8 on: May 13, 2019, 01:22:55 pm »
You want recumbent and off-road?
https://www.icetrikes.co/products/full-fat


I had a brief go on one at York rally. Tremendous, enormous fun.
<i>Marmite slave</i>

Kim

  • Timelord
Re: Gravel bike
« Reply #9 on: May 13, 2019, 01:43:07 pm »
The ICE Full Fat is a serious off-roader for mad people.

https://youtu.be/APJ8gLJ3gHY?t=2326 refers.  Delightfully bonkers.
Careful, Kim. Your sarcasm's showing...

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Gravel bike
« Reply #10 on: May 13, 2019, 02:19:01 pm »
that would definitely be fun to have a bash round Thetford Forest
“Procrastination is the thief of time, collar him.” –Charles Dickens

Kim

  • Timelord
Re: Gravel bike
« Reply #11 on: May 13, 2019, 02:22:47 pm »
I'd love to take one over the Sands Of Doom™.  I've mucked about on one on grass a couple of times, but that doesn't do it justice.
Careful, Kim. Your sarcasm's showing...

Re: Gravel bike
« Reply #12 on: May 13, 2019, 09:54:07 pm »
I'm quite happy riding my Fuego on wide forest tracks. I know the rear can take a 42mm tyre as I had one fitted for a while. So it can certainly take tyres with a suitable width and tread for gravel.  The turning circle means you'd never take it on narrow and twisty but narrow and straight and smoothest is fine. I'd probably want light elbow pads for comedy falls as the wheels lost traction in the gravel. There are also a few Bridleways and Greenways round here I have taken it down.

Re: Gravel bike
« Reply #13 on: May 14, 2019, 04:09:06 pm »
I've taken my Optima Orca around some comparatively muddy parts* of the Forest of Dean, as well as some local unsurfaced tracks (towpath etc).

*I think it currently has 2 inch small block tyres on it, but at the time it had 1.5" slicks. Which was interesting!
Life is too important to be taken seriously.

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Gravel bike
« Reply #14 on: May 14, 2019, 07:32:26 pm »
Wicken Fen, mostly gravel and hard packed earth is no issue with the S40 on 32mm GP4 Seasons - it's a nice summer/dry route to Addenbroookes.  One of Tomsk's Essex audaxes through a farmyard, 3 inches deep in cow shit was not quite so easy though.
“Procrastination is the thief of time, collar him.” –Charles Dickens