C[omp]ute

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 -
https://www.schwalbe.com/en/offroad-reader/thunder-burt.html - 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
http://acooke.org/cute/MountainBi0.html) - 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
boned...

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
heavier?).

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
there.


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.

Andrew