odd rim profiles

What's the rationale/aerodynamics behind some of the odd rim profiles available? Specifically, the
cutaway between the spoke holes on the Ksyriums and the inverted cross-sectional curve of Alex R390
rims (pic at http://www.nashbar.com/profile_moreimages.cfm?category=113&subcategory=1128&
sku=1128&brand= ).

--Art

 

"Art M" <[email protected]> wrote in message
news:[email protected]...
> What's the rationale/aerodynamics behind some of the odd rim profiles available? Specifically, the
> cutaway between the spoke holes on the Ksyriums and the inverted cross-sectional curve of Alex
> R390 rims (pic at
>
http://www.nashbar.com/profile_moreimages.cfm?category=113&subcategory=1128&
> sku=1128&brand= ).
>
> --Art

Dunno about the Alex rims, but the Ksyriums cutouts are for reducing weight.

Mike

 

"Mike S." <[email protected]> wrote in message news:<[email protected]>...
> "Art M" <[email protected]> wrote in message
> news:[email protected]...
> > What's the rationale/aerodynamics behind some of the odd rim profiles available? Specifically,
> > the cutaway between the spoke holes on the Ksyriums and the inverted cross-sectional curve of
> > Alex R390 rims (pic at
> >
> http://www.nashbar.com/profile_moreimages.cfm?category=113&subcategory=1128&
> > sku=1128&brand= ).
> >
> > --Art
>
> Dunno about the Alex rims, but the Ksyriums cutouts are for reducing weight.
>
> Mike

If you want to look at rim cross-sections, look through the QBP catalog, in particular:
http://harriscyclery.net/site/page.cfm?PageID=49&SKU=RM7530

The R390 is an odd cross-section, but I'm not sure I believe the miraculous properties listed on the
Alex site: "Lighter yet stronger than conventional road bike rims with its inside arch design, it
also helps to reduce wind resistance. The thicker inner wall prevents rim deformation caused by hard
braking and improves durability, the deep round inner wall prevents the rim strip from moving from
side to side, and the inner convex design fits the rim sleeve tightly."

(from http://www.alexrims.com/oe/index.htm - click on "Road Pro" then "R390" )

Jeff

 

Art-<< What's the rationale/aerodynamics behind some of the odd rim profiles available?
Specifically, the cutaway between the spoke holes on the Ksyriums and the inverted cross-sectional
curve of Alex R390 rims (pic at
http://www.nashbar.com/profile_moreimages.cfm?category=113&subcategory=1128& sku=1128&brand= ).
>><BR><BR>

Like a gent at Interbike said about a really wierd front der I was looking at-

" what's that thing for?", I ask.

"For selling", he says.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

"Qui si parla Campagnolo" <[email protected]> wrote in message
news:[email protected]...
> Art-<< What's the rationale/aerodynamics behind some of the odd rim
profiles
> available? Specifically, the cutaway between the spoke holes on the Ksyriums and the inverted cross-
> sectional curve of Alex R390 rims (pic at
>
http://www.nashbar.com/profile_moreimages.cfm?category=113&subcategory=1128&
> sku=1128&brand= ).
> >><BR><BR>
>
> Like a gent at Interbike said about a really wierd front der I was looking
at-
>
> " what's that thing for?", I ask.
>
> "For selling", he says.

LOL. You have a nice economy of dialog. The thing that threw me about the Alex rim was that you
usually don't see that much flair in a bike product that's so inexepensive.

--Art

> Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
> (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

Thanks for the links.

There seem to be a many medium aero rims that meet at an angle with the breaking surface. I would
hope that someone has tested and found that any small hit on drag there is less than the improvement
at the tire to rim junction. Or is it just another marketer's whim.

--Art

"Jeff Wills" <[email protected]> wrote in message
news:[email protected]...
> "Mike S." <[email protected]> wrote in message
news:<[email protected]>...
> > "Art M" <[email protected]> wrote in message
> > news:[email protected]...
> > > What's the rationale/aerodynamics behind some of the odd rim profiles available? Specifically,
> > > the cutaway between the spoke holes on the Ksyriums and
the
> > > inverted cross-sectional curve of Alex R390 rims (pic at
> > >
> >
http://www.nashbar.com/profile_moreimages.cfm?category=113&subcategory=1128&
> > > sku=1128&brand= ).
> > >
> > > --Art
> >
> > Dunno about the Alex rims, but the Ksyriums cutouts are for reducing
weight.
> >
> > Mike
>
> If you want to look at rim cross-sections, look through the QBP catalog, in particular:
> http://harriscyclery.net/site/page.cfm?PageID=49&SKU=RM7530
>
> The R390 is an odd cross-section, but I'm not sure I believe the miraculous properties listed on
> the Alex site: "Lighter yet stronger than conventional road bike rims with its inside arch design,
> it also helps to reduce wind resistance. The thicker inner wall prevents rim deformation caused by
> hard braking and improves durability, the deep round inner wall prevents the rim strip from moving
> from side to side, and the inner convex design fits the rim sleeve tightly."
>
> (from http://www.alexrims.com/oe/index.htm - click on "Road Pro" then "R390" )
>
> Jeff