Tires that mount easily on Sun CR-18 rims (ISO-559)

[Stephen Greenwood]

I just built a set of wheels using Sun CR-18 rims, ISO-559 size (a.k.a.
"26-inch"), and am dismayed by the difficulty I'm having in mounting
wire-beaded tires on them [1]. Some combinations of tires and rims are
simply more difficult to mount than others. Since I can't very well
swap rims, I'm looking for tires that are known to mount properly [2]
on these rims. Specifically, I'm looking for a commute-type or "urban"
tire: Slick tread, or nearly so, and somewhere around 35 to 45 mm in
width. I was able to mount a Kevlar-beaded MTB tire by hand, but I
don't want to limit myself to Kevlar-beaded tires because the vast
majority of commute-type tires have wire beads. Does anyone have
experience with tires that meet the above description? Thank you. I
would also appreciate similar information on a good studded tire.
Again, thank you.


[1] Judging from my search of the r.b.t. archives, I anticipate some
may suspect that the only real problems here are weak hands or poor
technique. The reason I present the problem as such is that I've used
many other sets of 559 wheels, each with rims of different manufacture
(Mavic, Bontrager, Araya, unknowns), and many types of tires for them
(Continental, WTB, Specialized, Maxxis, Geax). I've used dozens of
tire-rim combinations and never had this problem. Rim tape can also
play a role in mounting, so I cut down the width of the Velox rim tape
to just barely cover the spoke holes. This helped a little, but not
enough. I've also built wheels with rims from the same manufacturer
(Sun M13-II, 700c), again with Velox rim tape, and never had trouble
there, either.

[2] My constraint for "mount properly" is that it can be done with
hands only. If a tire-rim combination can only be mounted using levers,
its bead is so tight that you risk of pinching the tube. This happened
to me a few days ago with these rims... the only time in twenty-odd
years that I've ever damaged a tube mounting (or unmounting) a tire.

 

[sal bass]

at the shop i work at those rims are notorious for being tough to mount
tires to. which is why we don't offer them as an option. the last set
built with those...the customer was so ****** off at how difficult it
was to mount a tire, that the store manager just offered him to relace
any other rim of his choice and new spokes length for 50% off. it was
such a headache.

after he went off on his merry way with a new set of DT Swiss XT
4.1s...we tried mounting every tire we had in stock...about 14 tires
from about 8 different brands....not a single one went on without a
major struggle.....this was attemped by 6 different mechanics....no
levers....and several different techniques....






Stephen Greenwood wrote:
> I just built a set of wheels using Sun CR-18 rims, ISO-559 size (a.k.a.
> "26-inch"), and am dismayed by the difficulty I'm having in mounting
> wire-beaded tires on them [1]. Some combinations of tires and rims are
> simply more difficult to mount than others. Since I can't very well
> swap rims, I'm looking for tires that are known to mount properly [2]
> on these rims. Specifically, I'm looking for a commute-type or "urban"
> tire: Slick tread, or nearly so, and somewhere around 35 to 45 mm in
> width. I was able to mount a Kevlar-beaded MTB tire by hand, but I
> don't want to limit myself to Kevlar-beaded tires because the vast
> majority of commute-type tires have wire beads. Does anyone have
> experience with tires that meet the above description? Thank you. I
> would also appreciate similar information on a good studded tire.
> Again, thank you.
>
>
> [1] Judging from my search of the r.b.t. archives, I anticipate some
> may suspect that the only real problems here are weak hands or poor
> technique. The reason I present the problem as such is that I've used
> many other sets of 559 wheels, each with rims of different manufacture
> (Mavic, Bontrager, Araya, unknowns), and many types of tires for them
> (Continental, WTB, Specialized, Maxxis, Geax). I've used dozens of
> tire-rim combinations and never had this problem. Rim tape can also
> play a role in mounting, so I cut down the width of the Velox rim tape
> to just barely cover the spoke holes. This helped a little, but not
> enough. I've also built wheels with rims from the same manufacturer
> (Sun M13-II, 700c), again with Velox rim tape, and never had trouble
> there, either.
>
> [2] My constraint for "mount properly" is that it can be done with
> hands only. If a tire-rim combination can only be mounted using levers,
> its bead is so tight that you risk of pinching the tube. This happened
> to me a few days ago with these rims... the only time in twenty-odd
> years that I've ever damaged a tube mounting (or unmounting) a tire.

 

[JeffWills]

Stephen Greenwood wrote:
>
>
<snip>
Rim tape can also
> play a role in mounting, so I cut down the width of the Velox rim tape
> to just barely cover the spoke holes. This helped a little, but not
> enough.


Use *thinner* rim tape, not *narrower*. You want to decrease the
diameter of the rim at the middle of the channel, allowing more slack
in the bead. This makes it easier to pry the bead over the rim.

Plastic rim tape works well, but you may need to resort to fiberglass
strapping tape. It sounds like the rim was made a little oversize.

Jeff

 

[RonSonic]

On 20 Oct 2006 20:07:12 -0700, "sal bass" <[email protected]> wrote:

>at the shop i work at those rims are notorious for being tough to mount
>tires to. which is why we don't offer them as an option. the last set
>built with those...the customer was so ****** off at how difficult it
>was to mount a tire, that the store manager just offered him to relace
>any other rim of his choice and new spokes length for 50% off. it was
>such a headache.
>
>after he went off on his merry way with a new set of DT Swiss XT
>4.1s...we tried mounting every tire we had in stock...about 14 tires
>from about 8 different brands....not a single one went on without a
>major struggle.....this was attemped by 6 different mechanics....no
>levers....and several different techniques....

I own exactly one slime tube. It's on the wheel with the Sun rim. I knew that if
it flatted out in the woods I'd be the subject of pity and contempt and
amusement.

Ron

 

[Nate Knutson]

Stephen Greenwood wrote:
> I just built a set of wheels using Sun CR-18 rims, ISO-559 size (a.k.a.
> "26-inch"), and am dismayed by the difficulty I'm having in mounting
> wire-beaded tires on them [1]. Some combinations of tires and rims are
> simply more difficult to mount than others. Since I can't very well
> swap rims, I'm looking for tires that are known to mount properly [2]
> on these rims. Specifically, I'm looking for a commute-type or "urban"
> tire: Slick tread, or nearly so, and somewhere around 35 to 45 mm in
> width. I was able to mount a Kevlar-beaded MTB tire by hand, but I
> don't want to limit myself to Kevlar-beaded tires because the vast
> majority of commute-type tires have wire beads. Does anyone have
> experience with tires that meet the above description? Thank you. I
> would also appreciate similar information on a good studded tire.
> Again, thank you.

If you could be happy only being able to use folding tires, there's
Panaracer Paselas and T-servs, both of which are good tires that fit
what you want. 26" Paselas tend to be about 1/8" narrower than they're
labelled.

 

[Vee]

Stephen Greenwood wrote:
> I just built a set of wheels using Sun CR-18 rims, ISO-559 size (a.k.a.
> "26-inch"), and am dismayed by the difficulty I'm having in mounting
> wire-beaded tires on them [1]. Some combinations of tires and rims are
> simply more difficult to mount than others. Since I can't very well
> swap rims, I'm looking for tires that are known to mount properly [2]
> on these rims. Specifically, I'm looking for a commute-type or "urban"
> tire: Slick tread, or nearly so, and somewhere around 35 to 45 mm in
> width. I was able to mount a Kevlar-beaded MTB tire by hand, but I
> don't want to limit myself to Kevlar-beaded tires because the vast
> majority of commute-type tires have wire beads. Does anyone have
> experience with tires that meet the above description? Thank you. I
> would also appreciate similar information on a good studded tire.
> Again, thank you.
>
>
> [1] Judging from my search of the r.b.t. archives, I anticipate some
> may suspect that the only real problems here are weak hands or poor
> technique. The reason I present the problem as such is that I've used
> many other sets of 559 wheels, each with rims of different manufacture
> (Mavic, Bontrager, Araya, unknowns), and many types of tires for them
> (Continental, WTB, Specialized, Maxxis, Geax). I've used dozens of
> tire-rim combinations and never had this problem. Rim tape can also
> play a role in mounting, so I cut down the width of the Velox rim tape
> to just barely cover the spoke holes. This helped a little, but not
> enough. I've also built wheels with rims from the same manufacturer
> (Sun M13-II, 700c), again with Velox rim tape, and never had trouble
> there, either.
>
> [2] My constraint for "mount properly" is that it can be done with
> hands only. If a tire-rim combination can only be mounted using levers,
> its bead is so tight that you risk of pinching the tube. This happened
> to me a few days ago with these rims... the only time in twenty-odd
> years that I've ever damaged a tube mounting (or unmounting) a tire.

I'm not aware of any decent tire that mounts easily to a 26" CR-18. I
have a couple of the rims, and I always have to use a lever to install
tires. I have had good luck using the metal Park TL5 lever. It has a
broad but thin tip, and it's inflexible, so it works really well. A
lot of plastic levers (Park and Trek come to mind) are simultaneously
too thick and too flimsy to be useful when you actually need a lever.

-Vee

 

[Stephen Greenwood]

Thanks to all who replied.

Sal and Ron: I see I'm not alone.

Jeff: Yes, I understand about the thickness vs. width of the rim tape.
The intent with cutting down the width was that for this rim, it seems
to be best for the bead to sit on the shoulder, rather than in the
channel, during mounting. The channel is deeper than the shoulder, but
putting the bead there requires more lateral deformation, offsetting
the advantage of the increased depth. I cut down the rim tape width so
that the shoulders are bare, and I think that's as good as it's going
to get. It's difficult to see precisely what's going on, though, so I
haven't ruled out thinner rim tape. Several days ago I bought a Rox rim
tape in anticipation of this, and I may have to use it instead of the
faithful old Velox.

Nate: Much obliged. I have a set of 700c Paselas, but I was unaware of
the 26-inch versions of those. The T-serv also looks like a good
option. The original reasons I wanted to avoid relying on Kevlar-beaded
tires were high price and low availability, but it appears as though my
fears were unfounded (under $30 at various online retailers).

Vee: Thanks. I'm still loathe to use levers, because I'm afraid of
putting more holes in tubes and also of gouging up the rims with metal
levers. If they work well for you, that is good. That approach will be
my last resort, but I'll probably end up using the Kevlar-beaded tires.

 

[Johnny Sunset aka Tom Sherman]

Stephen Greenwood wrote:
> I just built a set of wheels using Sun CR-18 rims, ISO-559 size (a.k.a.
> "26-inch"), and am dismayed by the difficulty I'm having in mounting
> wire-beaded tires on them [1]. Some combinations of tires and rims are
> simply more difficult to mount than others....

Does anyone have data on the typical variation on bead seat diameter,
e.g. +/-0.1-mm, +/- 0.5-mm, +/- 1-mm, etc. on common production bicycle
rims?

I do not have a particularly strong grip (with some damage to my
dominant hand), but I can mount and dismount a 47-406 Tioga Comp Pool
[1] and a 28-406 Continental Grand Prix [2] on a Sun CR-18 rim without
tools. The leads me to speculate that the problem reported may be one
of bead seat diameter and not rim cross-section.

[1] NOS Japanese made tan wall, not Philippine made black wall.
[2] Idiotically marked as a 20x1-1/8 tire, which implies ISO 451-mm
bead seat diameter.

--
Tom Sherman - Here, not there.

 

[JeffWills]

Stephen Greenwood wrote:
> Thanks to all who replied.
>
> Sal and Ron: I see I'm not alone.
>
> Jeff: Yes, I understand about the thickness vs. width of the rim tape.
> The intent with cutting down the width was that for this rim, it seems
> to be best for the bead to sit on the shoulder, rather than in the
> channel, during mounting. The channel is deeper than the shoulder, but
> putting the bead there requires more lateral deformation, offsetting
> the advantage of the increased depth. I cut down the rim tape width so
> that the shoulders are bare, and I think that's as good as it's going
> to get. It's difficult to see precisely what's going on, though, so I
> haven't ruled out thinner rim tape. Several days ago I bought a Rox rim
> tape in anticipation of this, and I may have to use it instead of the
> faithful old Velox.
>

I think you misunderstand. The shoulders of the rim should be bare no
matter what. A thinner rim tape helps you *mount* the tire by allowing
the bead to sit on the reduced circumfrence at the middle of the rim's
channel. Once the tire is inflated, the beads of the tire should sit on
the shoulders of the rim's channel.

Try mounting the tire on a bare rim (no rim tape). You'll find that
it's very easy.

Many years ago I had a 17" Moulton tire that was mounted on a Sun M13
rim. It was nearly impossible to install or remove the tire without
three tire levers when it had Velox rim tape. When I switched it to
strapping tape, it only took one tire lever.

Jeff

 

[peter]

Johnny Sunset aka Tom Sherman wrote:
> Stephen Greenwood wrote:
> > I just built a set of wheels using Sun CR-18 rims, ISO-559 size (a.k.a.
> > "26-inch"), and am dismayed by the difficulty I'm having in mounting
> > wire-beaded tires on them [1]. Some combinations of tires and rims are
> > simply more difficult to mount than others....
>
> Does anyone have data on the typical variation on bead seat diameter,
> e.g. +/-0.1-mm, +/- 0.5-mm, +/- 1-mm, etc. on common production bicycle
> rims?
>
> I do not have a particularly strong grip (with some damage to my
> dominant hand), but I can mount and dismount a 47-406 Tioga Comp Pool
> [1] and a 28-406 Continental Grand Prix [2] on a Sun CR-18 rim without
> tools. The leads me to speculate that the problem reported may be one
> of bead seat diameter and not rim cross-section.

I would agree that the problem is with the bead seat diameter not being
consistent. I have two different Sun rims on my folding bike that uses
the ISO-451 (nom. 20") rim size. Unlike its ISO-559 counterpart, the
CR-18 rim on this bike is slightly undersized making it trivially easy
to dismount tires without tools but caution must be used when mounting
tires to avoid blow-offs. OTOH, the more aerodynamic Sun rim (not sure
of the model code) on the front wheel is a bit oversized and makes for
a real challenge to get tires off and on despite already having
substituted thin plastic tape for thicker rim tape.

 

[[email protected]]

Johnny Sunset aka Tom Sherman wrote:
> The leads me to speculate that the problem reported may be one
> of bead seat diameter and not rim cross-section.

I've sucessfully "tuned" rim circumference to achieve easier tire
mounting by disassembling the joint and filing off some metal. That
sure was a lot of work, and a little risky I guess, but with care I got
it to work for me.

 

[Stephen Greenwood]

I wrote:

> > Jeff: Yes, I understand about the thickness vs. width of the rim tape.
> > The intent with cutting down the width was that for this rim, it seems
> > to be best for the bead to sit on the shoulder, rather than in the
> > channel, during mounting. The channel is deeper than the shoulder, but
> > putting the bead there requires more lateral deformation, offsetting
> > the advantage of the increased depth. I cut down the rim tape width so
> > that the shoulders are bare, and I think that's as good as it's going
> > to get. It's difficult to see precisely what's going on, though, so I
> > haven't ruled out thinner rim tape. Several days ago I bought a Rox rim
> > tape in anticipation of this, and I may have to use it instead of the
> > faithful old Velox.
> >

JeffWills wrote:

> I think you misunderstand.

No, I understand. If the bead sits on the rim tape during mounting, a
thinner rim tape will help. The improvement is roughly equivalent to
increasing the bead circumference by a little less than pi times twice
the difference in rim tape thickness. For cloth tapes vs. some very
thin tapes, the difference is significant.

However, if the bead does not sit on rim tape during mounting, thinner
tape offers no improvement. I was saying that in my case, the bead
appears to sit on the shoulders during mounting. Thanks to the cut-down
rim tape, the shoulders are bare. I did try to force the bead to sit in
the smaller-diameter channel, where it normally goes. It's hard to see
precisely what happens, but applying force to the final portion of the
bead (not yet mounted) seems to cause the already-mounted portion of
the bead to creep out of the channel and onto the shoulder. Putting the
mounted part of the bead in the channel, rather than the shoulder,
requires a larger lateral displacement of the unmounted portion of the
bead. For this rim, that detrimental contribution appears to be larger
than the helpful contribution of increased depth in the channel. This
is what I tried to convey this in my previous post.

> The shoulders of the rim should be bare no
> matter what. A thinner rim tape helps you *mount* the tire by allowing
> the bead to sit on the reduced circumfrence at the middle of the rim's
> channel. Once the tire is inflated, the beads of the tire should sit on
> the shoulders of the rim's channel.

The shoulders needn't be bare on most rims, and indeed are not on
several other wheels I have. Maybe you're referring to the sidewalls?
You certainly do want to avoid having rim tape there. If you really did
mean "shoulders", it's not quite accurate to say that the bead "sit
on the shoulders" when the tire is inflated. The rim tape may lie
beneath the bead, but inflation doesn't force the bead against the
tape, toward the hub. Inflation forces the bead out and away from the
hub. (If this were not so, we wouldn't use hooked rims.) I use a
full-width rim tape whenever possible. No cutting needed, and the
larger contact area helps prevent the tape from moving.

> Try mounting the tire on a bare rim (no rim tape). You'll find that
> it's very easy.

I did that a couple weeks ago, with no tube in the tire. I could
*barely* get it on.

I believe these rims are simply oversized. I have three of them, and
they're equally troublesome. Judging from the stickers, two are from
one batch, and the third is from a different batch (and for a different
number of spokes). I don't think manufacturing variation is the
problem. The variance is low, but the mean is off.

Regards,
Stephen

 

[JeffWills]

Stephen Greenwood wrote:
<snip>
>
> I did that a couple weeks ago, with no tube in the tire. I could
> *barely* get it on.
>

Hmmm... I could make a dirty joke, but you've expended a heck of a lot
of effort on explaining things so I'll avoid the temptation.

> I believe these rims are simply oversized. I have three of them, and
> they're equally troublesome. Judging from the stickers, two are from
> one batch, and the third is from a different batch (and for a different
> number of spokes). I don't think manufacturing variation is the
> problem. The variance is low, but the mean is off.
>
> Regards,
> Stephen

I'm beginning to think you are correct. It'd be nice if we could test
samples from many batches of rims. Knowing what I know about rim
manufacturing, I'd guess that one of Sun's machines was miscalibrated,
and the mistake wasn't caught or their standards were too loose until
they'd produced many, many rims.

Want a couple old Mavic M231 rims? Barely used... they've been on my
mountain bike while I've been doing mostly road riding.

Jeff

 

[Stephen Greenwood]

JeffWills wrote:

<snip>

> Hmmm... I could make a dirty joke, but you've expended a heck of a lot
> of effort on explaining things so I'll avoid the temptation.

I expended the effort for the benefit of anyone searching the archives
on this topic. I don't post very often, but I've learned much from the
archives, and I figure I should contribute when possible.

> I'm beginning to think you are correct. It'd be nice if we could test
> samples from many batches of rims. Knowing what I know about rim
> manufacturing, I'd guess that one of Sun's machines was miscalibrated,
> and the mistake wasn't caught or their standards were too loose until
> they'd produced many, many rims.

I spoke to the technical support department at Sun. They said they
haven't changed the extrusion or hoop length for many years, and that
they're not aware of any bad batches for that rim.

> Want a couple old Mavic M231 rims? Barely used... they've been on my
> mountain bike while I've been doing mostly road riding.

Naw, that's alright. It would force me to rebuild my wheels, and I
don't want to trouble with it. I'll probably use Kevlar-beaded tires. I
do appreciate the offer.

All the best,
Stephen