Warnings from Andy Blance about the dangers overinflation pose to your rims may give a few of you the impetus to lower pressures, fit fatter tyres, or even graduate all the way up to balloons. See for instance p8 of the Mercury brochure: http://www.sjscycles.com/thornpdf/ThornMercuryHiRes.pdf
In return for years of good information and a great deal of entertainment on this board, mainly on the Rohloff forum, I thought I'd put something back by sharing some observations on riding fat low pressure tyres, which I've done for years. My everyday bike, a Utopia Kranich, is in fact designed from the ground up to have 60x622 Schwalbe Big Apples as its only suspension. I live among the hills of West Cork, and ride on very
poorly surfaced lanes, either badly potholed or, if newly fixed, rough with big tar-set chips. This is an edited version of my reply on rec.bicycles.tech to a question by Pete Cresswell about whether the weight of fat tyres would slow him down:
> I'm tempted to put out the big bucks for a set of Big Apples just
> to see how good/bad they are compared to more normal tires. From
> what I've read, speed for a given effort isn't too bad, but
> acceleration/liveliness suffers noticeably. "You pays your money
> and you takes your choice...."
There are explanations on the net by Jobst Brandt and Sheldon Brown about why slick or nearly-slick tyres of any width offer less rolling resistance than patterned tyres. And wider slicks have less rolling resistance than narrow slicks. Deeper technical explanations in my Designing and Building Special Cars
, if you can find a copy.
Admittedly, Big Apples are *heavy*. There is a certain amount of effort
required to get them moving. Still, once they're moving, the same
effect works in reverse, and they just keep on rolling; the Big Apples
contribute much to making your bike and you feel like a powerful
rolling force, just about unstoppable. I was used to paying for
Marathon Plus, so the Big Apples didn't strike me as expensive. I will
say though that, if you're worried about the weight, you should spend
the few bucks more and get the Big Apple Liteskins which are pounds
lighter per pair, and the superlight racing tube as well for another
substantial weight saving. My tubes are three years and 5000km of
potholed roads old and I've never had a flat. My Liteskins show no
great signs of wear either, and they haven't been mollycoddled.
As for the handling, I am very impressed with the Big Apples. I can't
make a direct comparison, because the two shorter-wheelbase, naturally
more nippy bikes that I have don't offer wide enough forks for Big
Apples, whereas the bike I have the Big Apples on has a very long
wheelbase and a very laid-back geometry, good for stable fast touring
on sweeping bends rather than darting in and out of traffic.
(Actually, since I fitted a electric motor, I've surprised myself by
doing a bit of nipping in and out of traffic, so the tyres are more
capable than the extent to which I've been using them, limited more by
my accelerative legpower from low speed than by their size and
On tarmac, which is all I know, the roadholding and handling of the
Big Apples are beyond anything on a bicycle you're likely to know. On
fast sweeping downhills, and on tight corners too, on bad road nobody can stay with me. Everyone who tries to keep up arrives at the bottom of the
big hills around here white and stressed, and with their coccyx
hurting. I've never, including some scary moments with a tractor in
the dusk of a winter's eve, even approached the real limits of the Big
Apple roadholding. And, I must tell you, I keep mine pretty soft
(usually under 2 bar for an all-up weight in the order of 130kg), so I
sacrifice no comfort for speed. Those big round tyres appear to cling
like shit to a baby's blanket with any part of them that you care to
roll the bike over onto. I've never been down on the Big Apples. (The
one time I should have gone down, after a spectacular downhill slide of sixty
metres on icy slurry, I crashed into the wheel of a tractor parked
across the road, and landed on my feet, with my bike upright too.)
The speed, the security, the recoveries possible from situations that
would put you down on another tyre (riding off a broken verge of road
with the front wheel), any one of these capabilities would make the
Big Apple worth the price. But we haven't even talked of the main
reason to fit it.
> The two chief offenders that I see around here are tree roots
> under blacktop - pushing it up into ridges; and concrete slabs
> with many cracks that mis-align over time.
My bike is designed from the ground up to take the biggest Big Apples,
60x622mm. They are its main suspension. My Brooks saddle is the three
helical spring model B73 but the seatpost is solid. There isn't even any gel
in my handblebar grips: they're Brooks' solid, edge-on leather rings,
hard as rock but surprisingly comfortable in combination with the Big Apples. I cycle with unpadded thin leather dress gloves. The frame itself is of lightweight steel and crossframe design, triangulated in three dimensions and capable of resisting more than 5000lbs per inch of twist (same as a big Rolls-Royce car), in short ultra-stiff. The entire suspension is thus in the Big Apples.
I am ultra-sensitive to vibrations in my hands. The roads here are
pretty rough. Even when they're newly made, they're uneven and the top
surface hardly ever smooth; the lanes and minor roads I ride would,
in the States, get the official in charge of them summarily dismissed
five days a week. But in the nearly three years I've had the Utopia
Kranich with the Big Apple Liteskins, this is the first time I've
given a thought to residual stress injury in my wrists from vibrations
on my bike, and then only to say I gave it no thought for 34 months.
Microvibrations are an important problem on a bicycle, and it is one the Big
Apple designer understands or has lucked into an answer to. You
can't storm a Big Apple equipped bike across the sharper speed bumps
without feeling the effect, but I do ride mine faster across the
speedbumps at the supermarket than any other cyclist in town. But
that's the sort of bump you are aware of, and take measures to
ameliorate. What you can't see, and what mechanical or hydraulic
suspension on bikes is too stiff and slow to handle well, is
microvibrations from the road. This the Big Apples handles
brilliantly: one day you just remember that your hands and wrists
haven't hurt for quite a while. It's the least visible of all the Big
Apple advantages but to my way of thinking the most dramatic.
Out on the open road, I ride the Big Apples straight through potholes
that would stop a Marathon Plus equipped bike by throwing off the
rider, and that my roadie friends have to slow to ride around. I feel
no pain. The ability of the Big Apples to take anything in their
stride without disturbance to the rider or his line is a big part of
their ability to set impressive point to point times, a consistent and
significant fraction better than the widely respected and very capable
Marathon Plus which was my previous favourite.
As you can see, I'm very impressed. I've already bought replacements
for my Big Apple Liteskins and the Superleicht racing tubes (type 19A)
-- same again. They come in boxes the size of shoeboxes for
substantial pairs of boots. They sit reassuringly on top of my biggest
I know, everyone fits 29er tyres to rims for skinny tyres, and ERTRO made a special exception to the rules about matching tyre width to rim width for it. I don't care what ERTRO does for commercial reasons. For engineering reasons, more than adequately explained in Andy Blance's note reproduced above, it is not clever
. A rim narrower than 40% of the tyre width defeats the purpose of the Big Apple -- which we have seen is a cushy, fast, secure ride -- by forcing you to inflate the tyre to a much higher pressure, which not only cuts severely into your comfort, but into your speed as well, because the jarring from the hard tyres throws you off line.
Big Apples cry out for rims at least 25mm wide, preferably wider. For the record, my 60mm/2.35in Big Apples ride on Exal XL rims, 25mm wide on the inside, and I'm just about to build an electric front wheel on a Rigida Big Bull rim, also 25mm wide on the inside, because I can't source an Exal XL in 622 size. On wider rims you can reduce the pressure still more. Well made very wide rims are available: try the unicycle suppliers.
There are photographs of my roads on my personal netsite: http://coolmainpress.com/BICYCLING.html