SunRims CR-18: Couldn't get tire off...?

Are they USB (tubeless tire) rims? I have a pair of Mavic
Crossoads on my ATB with this same problem (no, I don't use
tubeless tires, waste of trouble and money IMO). Mounting
and dismounting tires, Esp. wire bead is exceptionally
difficult.

Prying off the USB strip and applying plain Velox tape
helped. But I still need three irons for anything other than
kevlar bead folding tires. Use the plastic ones, they'll
break before marring the rim.

"May you have the wind at your back. And a really low gear
for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner geocities.comczcornerOpen ↗

(Pete Cresswell) said:

On a new wheel they used a SunRim Cr-18.

This was a 'first' for me - always used Mavic 517's
or 618's.

Never had any problem getting tires on/off the Mavic rims.

On the SunRim, however, one tire went on really hard - took
a couple prys with the tire irons to get it over the lip,
didn't think much about it afterwards.

<snip>

Quoted message said:

Am I missing something technique-wise or are some
rims/tires just bad combinations?

It's the Sun rims. Rhyno Lites are as bad or worse. Coupled
with a more loose-fitting tire they are somewhat difficult.
When a tire known to fit tightly is used, they are absolute
hell (as you now know).

I still like my old Araya rims and even some generic no name
aluminum rims that I ended up with more than the current new
offerings on the market.

[email hidden] (Chris Zacho "The Wheelman"😉 wrote in message news:<[email hidden]>...

Quoted message said:

Are they USB (tubeless tire) rims? I have a pair of Mavic
Crossoads on my ATB with this same problem (no, I don't
use tubeless tires, waste of trouble and money IMO).
Mounting and dismounting tires, Esp. wire bead is
exceptionally difficult.

Chris, CR-18's are about as conventional a rim as you'll
find. The QBP catalog does a great job if you're comparing
rim profiles:
harriscyclery.netpage.cfmOpen ↗

I've used them in a couple different applications, including
recumbents (they come in 20" and 700C as well as 26"😉. I'd
*guess* that the rim Pete has is slightly oversize. Perhaps
it's within tolerance, just on the large side of normal.

On the other hand, it's possible that the tire was built
slightly undersize- still within manufacturing tolerance,
just on the *small* side.

I'd check to see other tires have the same problem on that
rim- that'll help narrow down what element has the problem.

Also, using a thinner rim strip is an easy fix for hard-to-
mount tires.

Jeff

Quoted post said:

Originally posted by x
On a new wheel they used a SunRim Cr-18.

This was a 'first' for me - always used Mavic 517's or
618's.

Never had any problem getting tires on/off the Mavic rims.

On the SunRim, however, one tire went on really hard - took
a couple prys with the tire irons to get it over the lip,
didn't think much about it afterwards.

But then I went to take it off..... Geeze!.... Made sure the
bead was free and pinched the casing so both beads were in
the center but still couldn't get that thing off.

After doing some cosmetic damage to the rim with the tire
irons and bending the lip on one of the irons I just cut it
off. Scratch one tire.....

The tire I have on there now comes off, but grudgingly -
takes a couple of stragegically-placed prys with the irons
to get it off.

OTOH, I got the second tire *on* the rim without resorting
to irons...

Am I missing something technique-wise or are some rims/tires
just bad combinations?
--
PeteCresswell

CR18 rims are OK, but there may be a few things to consider:
1. Spoke tension... if it's on the low side the rim shrinkage will be minimal. High even tension may gain you the desired 1 - 2 mm of rim shrinkage.
2. Tire talc will make the tire/tube interface and tire/rim interface easier to deal with.
3. Some rims are slightly larger diameter than the specified bead diameter
4. Some tires are slightly smaller than specified bead diameter
5. The inside rim wall on the CR18 isn't very concave
6. Some tires are just tougher to mount
7. Thin rim strips can aid the mounting process, but don't compromise the intergrity

check 'DIY tire removal' ijn bike tech achives. the cr-18 is
a bargain. lube the hooked spoke ends and hub holes with wax
or silicone. fillum. rim horizontal

Chris B. said:

... It's the Sun rims. Rhyno Lites are as bad or worse.
Coupled with a more loose-fitting tire they are somewhat
difficult. When a tire known to fit tightly is used, they
are absolute hell (as you now know)....

I have no problem getting tires on and off my Sun Rhyno Lite
and CR-18 rims. The tires in question are 28-406 Continental
Gran Prix, 47-406 Avocet Fasgrip Freestyle, and 47-406
Mitsuboshi Tioga Competition Pool (Japanese made "tanwall"😉.

Tom Sherman - Quad Cities (Illinois Side)

Tom Sherman said:

Chris B. said:

... It's the Sun rims. Rhyno Lites are as bad or worse.
Coupled with a more loose-fitting tire they are somewhat
difficult. When a tire known to fit tightly is used, they
are absolute hell (as you now know)....

I have no problem getting tires on and off my Sun Rhyno
Lite and CR-18 rims. The tires in question are 28-406
Continental Gran Prix, 47-406 Avocet Fasgrip Freestyle, and
47-406 Mitsuboshi Tioga Competition Pool (Japanese made
"tanwall"😉.

My experiences are based entirely on the 26" (559mm) size
which I think is what Pete C. was referring to; I
wouldn't know if Sun has mastered the basketball hoop
size. I have spoken to a few other users of Sun rims and
more than one bike shop mech along the way and I
convinced myself that it was not just poor technique or a
bum sample that was to blame.

Perhaps a shop owner/rat will relate their observations. I'd
like to know if I should tuck my extra Rhyno Lites in the
attic with the Inverted Jenny biplane stamp and the Faberge
Egg with Sapphire Pendant.

"(Pete Cresswell)" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

On a new wheel they used a SunRim Cr-18.

This was a 'first' for me - always used Mavic 517's
or 618's.

Never had any problem getting tires on/off the Mavic rims.

On the SunRim, however, one tire went on really hard -
took a couple prys with the tire irons to get it over the
lip, didn't think much about it afterwards.

But then I went to take it off..... Geeze!.... Made sure
the bead was free and pinched the casing so both beads
were in the center but still couldn't get that thing off.

After doing some cosmetic damage to the rim with the tire
irons and bending the lip on one of the irons I just cut
it off. Scratch one tire.....

The tire I have on there now comes off, but grudgingly -
takes a couple of stragegically-placed prys with the irons
to get it off.

OTOH, I got the second tire *on* the rim without resorting
to irons...

Am I missing something technique-wise or are some
rims/tires just bad combinations?

I've got CR18s and I've never had any problems. I'd suggest
you use another brand of tyre.

If your tube is too large either a 27 inch tube on a 700c
rim or a 26x2.0 tube in a 26x1.5 tire it will be hard to get
off. if you have presta valves leave the valve open if you
have shrader valves remove the core. Take a file and file
down the cosmetic damage and polish the edge of the rim with
some scotch bright of fine sandpaper every little bit helps.

prestone silicone lube and abrasive pad with same cleaning
the edges and seats helps.