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Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

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Schwalbe Thunder Burt 2.1 v Continental X-King 2.4

From: andrew cooke <andrew@...>

Date: Tue, 14 Feb 2017 13:42:50 -0300

I've been riding some Thunder Burts (TBs) for the last 1,800km (since
I first built my Cotic Soul).  They are the Snakeskin Evo model, which
I think is the top version - - and
they cost $45 each from CRC (650b, folding bead).

They've been great - very fast rolling, light - and seem durable with
a lot of life still left.  But while they are well-suited to the
riding I do much of the time (gravel trails, cycle paths, roads), I
felt like I was missing some grip when riding in Durazno Bike Park, or
out to the East, near Panul (for some context, see - trails where the surface is
sandy and loose.

So I ordered some X-Kings (XKs) (2.4" ProTection, Black Chili - again,
the top model, at $44 each), which in the wider size (Continental
recommend 2.2" for XC and 2.4" for Trail) tend towards the opposite
end of the spectrum to the TBs - they're still intended to be
fast-rolling, but for an XC tyre they're fairly meaty.

The new tyres arrived yesterday.  I put them on the bike last night
and this morning went out to Durazno.  What follows, then, are my
first impressions of the XKs, largely in comparison to the TBs.

First impressions off the bike were of a bigger, fatter, blacker tyre.
I forgot to measure the TBs, but the XKs are 2 1/4" across when
mounted on my 27mm internal Arc rims.  Honestly, they look cooler than
the TBs, which always seemed a little small and, well, grey.  In
comparison, the XKs are not exactly plus-sized, but certainly big

I used the same pressure (25psi) that I use in the TBs, with latex
tubes (which "feel" a lot more supple than normal tubes - I suspect
they are close to the the feel of tubeless, although obviously I am
going with a higher pressure than people might run tubeless).  As I
write this, after the ride, I am thinking that a slightly lower
pressure might address some of the harshness I will discuss below.

On the bike, my first reaction was surprise at how heavy they felt.
CRC list the XKs at 690g, while the TBs are 480g.  That's over 40%
more and, at first, they felt like tanks.  However, that impression
did go away over the course of the ride - by the time I was back home
I guess I was used to them and they really didn't feel that unusual.

Despite the weight, I couldn't detect much difference in rolling
resistance.  It seemed like they took more effort to spin up, but once
I was rolling, they didn't need any more work than the TBs.  The XKs
were very slightly louder, but only at speed, when you could start to
hear the whine of the individual blocks on the road.

One difference that is difficult to describe is that the XKs felt
"harsher" on the easy, hardpack trail along by the river - a little
like my suspension wasn't dialled in correctly.  I tried changing the
rebound setting, but couldn't improve things completely (the XKs seem
to need slightly more rebound damping - perhaps because they are

Comparing my Strava sections for the ride I just completed (on XKs),
with a similar ride on TBs, the roads sections are slightly slower,
but not by a huge amount - it could just be that I was having a
slightly off day (my legs have been pretty tired recently and I'm
looking forwards to next week off, on vacation).

Arriving at the bike park I hoped that the XKs would improve my
climbing.  There are two places where, on my last ride there, I
stalled out on the TBs: once in sand and once in a more technical,
steeper section.  My hope was that in both places I could make it
through with the XKs.

At the start of the ride, I did feel that the XKs were more secure.
Riding on the side of a water-damage V shaped gully, I felt more
confident - less worried that the rear was going to slip down.

But at both critical points - the places I was hoping the tyres would
make a real difference - I repeated my old mistakes.  Bummer.  In both
cases, I am sure I can improve.  A better line could avoid the sand,
or with a bit more strength I could power through, and the technical
part needs just a little more commitment and energy.

So while the XKs seemed be an overall improvement on the dirt - I felt
more confident of the rear, in particular - they weren't the game
changers I had hoped for.

On the way back home, hopping over speed bumps, I noticed that for
some weird reason I was doing better on the XKs.  At first this seemed
dumb - how could it make a difference? - but after thinking some I
found a couple of possible explanations.  First, perhaps the fatter
tyres have more bounce, so give extra lift.  And second, I think they
cushion the landing better, making things feel smoother.

On Strava, after the ride, studying section times (it didn't help that
I stopped to eat a sandwich in the middle of the climb :) it seems
like the XKs on the road are slightly slower, but my off-road climbing
times are slightly faster.  Which makes sense.  Unfortunately I don't
have any off-road descents in common to the two rides (and I suck at
descending anyway), but I'd expect an advantage to the XKs again

Conclusions, then, are what you'd expect.  Heavier tyres take more
effort.  Better grip seems to help, but really isn't a replacement for
skill.  If I want to get faster I need to work on fitness and control,
with either tyre.


Update: Second Ride

From: andrew cooke <andrew@...>

Date: Thu, 16 Feb 2017 16:41:24 -0300

Some extra observations from a second ride:

* They feel totally normal (not heavy) now.

* I still fucked up both places on the climb (although the second one
  was very close - dabbed just on the exit).

* This ride had a long, fast descent that I had done a couple of times
  before on the TBs.  I was MUCH faster on the XKs (20m v 28m) but I
  think this is largely my learning to descend better (the XKs can't
  hurt, of course).

* I got my rear caught on the side of a long wooden sleeper at speed
  (part of a wooden bridge).  Given the problems I have had with
  RaceKing tirewalls I was worried there would be significant damage
  but could see only some minor scuffing.  So the XKs seem
  significantly tougher than the old RaceKings (don't know how TBs
  compare - they seem pretty good too).


Update: Lower Pressures

From: andrew cooke <andrew@...>

Date: Sat, 1 Apr 2017 20:19:10 -0300

After a month or so using the XKs I have a couple more observations:

* Using a lower pressure (22, doen from 25psi I used with the TBs)
  really helps reduce the harshness in the ride (although they still
  sound like a jet engine whining on fast road descents).

* The XKs have much better puncture resistance than the TBs, and
  appear to be wearing better, but the rubber seems to not be as


Continental Race King 2.2

From: andrew cooke <andrew@...>

Date: Sat, 25 Nov 2017 11:47:24 -0300

These are a favourite from my old bike, so when the TBs wore down
smooth (after ~10,000km - they lasted well) I tried these as a

Honestly, they're pretty much what you might expect from the numbers:
they feel heavier than the TBs (and they are - 600g v 480g) but roll
as well - better than the XKs.  They are big tyres - on my rims
they're 2 1/4" across (same as the XKs, wider than the TBs) and they
feel "bouncy" - it's a bit like I imagine riding a plus bike feels.

Riding them on the loose, dry, rocky conditions here they're not that
much worse than the XKs.  I think they would do well as a single,
do-it-all tyre for both road and off-road.  But as a pairing to the
XKs, the TBs probably make more sense - for mainly on-road these are
too large and heavy.


Update: Higher Pressures

From: andrew cooke <andrew@...>

Date: Mon, 11 Dec 2017 12:45:38 -0300

The Race Kings feel much better (less "bouncy", more "normal") at
25psi.  Although they may grip a little less (had them snow-plow
sideways where I think the XKs would have gone straight).

Edit a few days later: OK, so I just came off on a local, simple
descent (dry dirt + rocks) I've done many times before.  At 25psi
these are not great on the front.  Will have to go back to 21psi when
doing anything off-road.


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