Big fat wheels for cyclocross

[Squat'n Dive]

After seeing the rim failure thread I'm a bit worried preparing to run
a Mavic CXP-33 rim
on a cyclocross bike I'm about to order.
Would a 622x38 or 45 cause the extra load on the rim and a premature
rim failure?
What are my options for a fat stiff cyclocross rim, pref 36 double
eyelet (rear) that can
take tires from 622-23 up to 622-45? Is there such a versatile rim?
Options for a rim like that with ceramic breaking surface and lower
eyelet count
(front)?

 

[landotter]

On Jan 28, 12:55 pm, "Squat'n Dive" <[email protected]> wrote:
> After seeing the rim failure thread I'm a bit worried preparing to run
> a Mavic CXP-33 rim
> on a cyclocross bike I'm about to order.
> Would a 622x38 or 45 cause the extra load on the rim and a premature
> rim failure?

At marshmallow pressures, surely not, but it's still not a great idea
to have too narrow of a rim for a tire, if ya want stability. Sun
Rhynolite and Alex DM18 are two that are simple, strong, and
inexpensive--however, neither will do well with a tire narrower than
28mm as far as I can remember. But, then again, who wants to put <28s
on a cross bike anyway?

 

[Chalo]

Squat'n Dive wrote:
>
> After seeing the rim failure thread I'm a bit worried preparing to run
> a Mavic CXP-33 rim on a cyclocross bike I'm about to order.
> Would a 622x38 or 45 cause the extra load on the rim and a premature
> rim failure?

Nope.

A larger tire protects the rim by attenuating peak loads from bumps
and landings. You have to use lower pressure than you would in a
narrow tire to realize the benefits of a fatter one.

> What are my options for a fat stiff cyclocross rim, pref 36 double
> eyelet (rear) that can take tires from 622-23 up to 622-45?

If you want to use 700x23 tires, you'll need a rim no wider than about
21mm. That pretty much eliminates touring rims as a category. If you
want a much stronger rim than the CXP-33 that will still work with
23mm tires, the Velocity Deep-V is a good choice.

The Alex Crostini R1.1 and R1.2 (with offset spoke holes) look good
and come from what I consider to be today's best rim maker. I have
not tried either of those rims in particular, though.

Chalo

 

[landotter]

On Jan 28, 1:41 pm, Chalo <[email protected]> wrote:

> The Alex Crostini R1.1 and R1.2 (with offset spoke holes) look good
> and come from what I consider to be today's best rim maker. I have
> not tried either of those rims in particular, though.

I've made a minor effort to try and locate some when I'd first seen
them on the alexrims.com site--as indeed, if they're Alex quality with
offset drilling, it's a win-win. No luck. I have seen them as OEM on a
few flat-bar bikes at the LBS. Good stuff, if you can source them.

 

[Kinky Cowboy]

On Mon, 28 Jan 2008 10:55:41 -0800 (PST), "Squat'n Dive"
<[email protected]> wrote:

>After seeing the rim failure thread I'm a bit worried preparing to run
>a Mavic CXP-33 rim
>on a cyclocross bike I'm about to order.
>Would a 622x38 or 45 cause the extra load on the rim and a premature
>rim failure?

Real cyclocross, or just a CX bike for other purposes? You can't race
on anything bigger than 35 anyway. For other uses, see the Mavic
pressure chart which shows safe working pressure against tyre width;
it can be found as a label on some Mavic rims, e.g. my Open Pros have
a label saying 10bar/19mm to 8bar/28mm. That suggests a maximum of
5bar on a 38, should you be minded to fit such fat treads to skinny
rims.

You need a wider rim for tyres over 28mm according to Mavic, although
plenty of people get away with 30-32mm CX tyres on rims optimised for
23mm road race rubber. If you're going up to 38-45mm tyres, you
definitely need a wide touring rim, as those kind of tyres will have
been designed to operate best off a wider base.

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

 

[Nick Payne]

A tyre is basically a cylindrical pressure vessel, which means that for a
given pressure, the stress on the rim is proportional to the diameter of the
tyre. So, for example, if you pump 19mm and 38mm tyres to the same pressure,
the stress on the rim is double with the 38mm tyre. Conversely, a 38mm tyre
at 60psi puts the same stress on the rim as a 19mm tyre at 120 psi...

Nick

"Squat'n Dive" <[email protected]> wrote in message
news:f3d3823a-1e9f-44eb-8e33-ec316713d832@f47g2000hsd.googlegroups.com...
> After seeing the rim failure thread I'm a bit worried preparing to run
> a Mavic CXP-33 rim
> on a cyclocross bike I'm about to order.
> Would a 622x38 or 45 cause the extra load on the rim and a premature
> rim failure?
> What are my options for a fat stiff cyclocross rim, pref 36 double
> eyelet (rear) that can
> take tires from 622-23 up to 622-45? Is there such a versatile rim?
> Options for a rim like that with ceramic breaking surface and lower
> eyelet count
> (front)?

 

[Jay Beattie]

On Jan 28, 3:20 pm, Kinky Cowboy <[email protected]> wrote:
> On Mon, 28 Jan 2008 10:55:41 -0800 (PST), "Squat'n Dive"
>
> <[email protected]> wrote:
> >After seeing the rim failure thread I'm a bit worried preparing to run
> >a Mavic CXP-33 rim
> >on a cyclocross bike I'm about to order.
> >Would a 622x38 or 45 cause the extra load on the rim and a premature
> >rim failure?
>
> Real cyclocross, or just a CX bike for other purposes? You can't race
> on anything bigger than 35 anyway. For other uses, see the Mavic
> pressure chart which shows safe working pressure against tyre width;
> it can be found as a label on some Mavic rims, e.g. my Open Pros have
> a label saying 10bar/19mm to 8bar/28mm. That suggests a maximum of
> 5bar on a 38, should you be minded to fit such fat treads to skinny
> rims.
>
> You need a wider rim for tyres over 28mm according to Mavic, although
> plenty of people get away with 30-32mm CX tyres on rims optimised for
> 23mm road race rubber.

Most CX racers that I know use standard road rims like Open Pros and
CPX 33s -- at least the ones who use ordinary OTC rims and not the
spendy botique wheels. I have seen plenty of cross riders running
30+mm tires on some pretty expensive road race wheels. Personally, I
use Open Pros on my cross bike with 32mm tires. -- Jay Beattie.

 

[Squat'n Dive]

On Jan 28, 5:20 pm, Kinky Cowboy <[email protected]> wrote:
> On Mon, 28 Jan 2008 10:55:41 -0800 (PST), "Squat'n Dive"
>
> <[email protected]> wrote:
> >After seeing the rim failure thread I'm a bit worried preparing to run
> >a Mavic CXP-33 rim
> >on a cyclocross bike I'm about to order.
> >Would a 622x38 or 45 cause the extra load on the rim and a premature
> >rim failure?
>
> Real cyclocross, or just a CX bike for other purposes? You can't race

CX bike for road going with wide winter spiked tires. I don't race,
just pedal semi-hard.

> on anything bigger than 35 anyway. For other uses, see the Mavic
> pressure chart which shows safe working pressure against tyre width;
> it can be found as a label on some Mavic rims, e.g. my Open Pros have
> a label saying 10bar/19mm to 8bar/28mm. That suggests a maximum of
> 5bar on a 38, should you be minded to fit such fat treads to skinny
> rims.
>
> You need a wider rim for tyres over 28mm according to Mavic, although
> plenty of people get away with 30-32mm CX tyres on rims optimised for
> 23mm road race rubber. If you're going up to 38-45mm tyres, you
> definitely need a wide touring rim, as those kind of tyres will have
> been designed to operate best off a wider base.

Are there cyclocross events scheduled in winter? If not
i guess that'd explain the lack of cyclocross specific rims.
I assume there are some stiff touring rims available among the
Velocity Deep-V, Alex Crostini R1.1 and R1.2, Sun
Rhynolite, Alex DM18 and whatever else was recommended?
Something as stiff as CXP-33 or at least OpenPro perhaps?

 

[Ryan Cousineau]

In article
<[email protected]>,
"Squat'n Dive" <[email protected]> wrote:

> On Jan 28, 5:20 pm, Kinky Cowboy <[email protected]> wrote:
> > On Mon, 28 Jan 2008 10:55:41 -0800 (PST), "Squat'n Dive"
> >
> > <[email protected]> wrote:
> > >After seeing the rim failure thread I'm a bit worried preparing to run
> > >a Mavic CXP-33 rim
> > >on a cyclocross bike I'm about to order.
> > >Would a 622x38 or 45 cause the extra load on the rim and a premature
> > >rim failure?
> >
> > Real cyclocross, or just a CX bike for other purposes? You can't race
>
> CX bike for road going with wide winter spiked tires. I don't race,
> just pedal semi-hard.
>
> > on anything bigger than 35 anyway. For other uses, see the Mavic
> > pressure chart which shows safe working pressure against tyre width;
> > it can be found as a label on some Mavic rims, e.g. my Open Pros have
> > a label saying 10bar/19mm to 8bar/28mm. That suggests a maximum of
> > 5bar on a 38, should you be minded to fit such fat treads to skinny
> > rims.
> >
> > You need a wider rim for tyres over 28mm according to Mavic, although
> > plenty of people get away with 30-32mm CX tyres on rims optimised for
> > 23mm road race rubber. If you're going up to 38-45mm tyres, you
> > definitely need a wide touring rim, as those kind of tyres will have
> > been designed to operate best off a wider base.
>
> Are there cyclocross events scheduled in winter? If not
> i guess that'd explain the lack of cyclocross specific rims.
> I assume there are some stiff touring rims available among the
> Velocity Deep-V, Alex Crostini R1.1 and R1.2, Sun
> Rhynolite, Alex DM18 and whatever else was recommended?
> Something as stiff as CXP-33 or at least OpenPro perhaps?

"CX-specific rims" tend to be very light deep-section tubulars.
Essentially, CXers repurpose highly aero rims for their own need
(tubular, light, cut through mud). But that's racing gear.

For the Rest of Us, "cyclocross" rims are some variation on either "your
road rims with new tires" or "some reasonably tough 700c rim." For truly
gonzo "CX" projects, the 29er is here to help.

I get surprisingly usable traction with a set of 32 mm hybrid tires (WTB
Allterrainasaurus) on my CX bike. I just used them to ride to work and
back (a short 15-minute jaunt) today, after a half-metre of snow fell
yesterday.

Notably, the bike stops making forward progress once the wet snow comes
up above the BB spindle. Maybe it was a traction issue.

Bicycle tire rubber is very soft relative to car rubber, and I think the
narrow profile helps in certain snow and slush conditions. Note that the
prevailing circumstance locally is mucky slush, which is quite different
from the kind of snow conditions you get at, say -10 C.

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."

 

[A R:nen]

Ryan Cousineau <[email protected]> writes:

> Notably, the bike stops making forward progress once the wet snow comes
> up above the BB spindle. Maybe it was a traction issue.

Maybe you need to improve the nivadynamics (sp?) of your bike by, say,
adding a snow plough up front. (Of course the snow eats up momentum
real fast and if there is enough snow to impede the pedalling motion,
there's not much you can do. As far as I'm concerned, 10 cm or even the
occasional 20 cm of fresh snow is fun to ride in, but that's where I
draw the line.)

 

[Ryan Cousineau]

In article <[email protected]>,
[email protected] (A R:nen) wrote:

> Ryan Cousineau <[email protected]> writes:
>
> > Notably, the bike stops making forward progress once the wet snow comes
> > up above the BB spindle. Maybe it was a traction issue.
>
> Maybe you need to improve the nivadynamics (sp?) of your bike by, say,
> adding a snow plough up front. (Of course the snow eats up momentum
> real fast and if there is enough snow to impede the pedalling motion,
> there's not much you can do. As far as I'm concerned, 10 cm or even the
> occasional 20 cm of fresh snow is fun to ride in, but that's where I
> draw the line.)

An interesting suggestion, but I suspect the plow would increase the
resistance of the snow without increasing the traction of the bike .

I had a hilarious good time last year riding in nearly-as-deep powder,
albeit mainly downhill.

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."