Tire Anatomy Question + Weird Fit
12-21-09, 08:59 PM
#1
Junior Member
Thread Starter
Join Date: Sep 2009
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Tire Anatomy Question + Weird Fit
I tried searching this forum, but since I don't know the proper terminology I may have missed the mark. Yep, I'm a noob. Please bear with me.
First, the anatomical question: Ok, you where the tire bead is, right? Well, what do you call the lines that sit just outside of each bead on the wall of the tire and sit flush with rim's outer edge when the tire is mounted? On some tires these lines are solid. On other tires these line may be harsh marks, dots, etc. I would assume that the lines' purpose is show the relative location of the bead and that if the line sits flush to the rim's outer edge and is visible along the entire circumference of the rim, one could assume that the bead is seated correctly. Yeah, so what's that line called?
Next, here's my problem. I have a wheel set that seems to have a problem with whatever-that-line-is-called. I've mounted three different makes of tires on these wheels and produced the same weirdness with all three tire types: With the tires fully inflated (and even inflated at max psi + 10% for sake of experiment, not for riding) this line dips below the edge of the rim in one five to six inch length on each side of the wheel. This would lead me to believe that the tire beads are not seating correctly in the rim.
The tires I've used are:
- brand new, never used 28mm Kendas (don't now the model)
- brand new, never used 32mm Hutchinson Urban Tour
- used, high mileage 32mm Bontrager Race Lite Hard Case
About the wheels: no-name OEM 700c rims that were rebuilt by my LBC using some older and gently used Specialized hubs for the purpose of providing my old ten speed frame with some spiffy 700c wheels.
So, am I making a mountain out of a molehill or do I have a problem with my rims?
First, the anatomical question: Ok, you where the tire bead is, right? Well, what do you call the lines that sit just outside of each bead on the wall of the tire and sit flush with rim's outer edge when the tire is mounted? On some tires these lines are solid. On other tires these line may be harsh marks, dots, etc. I would assume that the lines' purpose is show the relative location of the bead and that if the line sits flush to the rim's outer edge and is visible along the entire circumference of the rim, one could assume that the bead is seated correctly. Yeah, so what's that line called?
Next, here's my problem. I have a wheel set that seems to have a problem with whatever-that-line-is-called. I've mounted three different makes of tires on these wheels and produced the same weirdness with all three tire types: With the tires fully inflated (and even inflated at max psi + 10% for sake of experiment, not for riding) this line dips below the edge of the rim in one five to six inch length on each side of the wheel. This would lead me to believe that the tire beads are not seating correctly in the rim.
The tires I've used are:
- brand new, never used 28mm Kendas (don't now the model)
- brand new, never used 32mm Hutchinson Urban Tour
- used, high mileage 32mm Bontrager Race Lite Hard Case
About the wheels: no-name OEM 700c rims that were rebuilt by my LBC using some older and gently used Specialized hubs for the purpose of providing my old ten speed frame with some spiffy 700c wheels.
So, am I making a mountain out of a molehill or do I have a problem with my rims?
Last edited by domzilla9; 12-21-09 at 09:04 PM.
12-21-09, 10:12 PM
#3
Senior Member
Join Date: Nov 2009
Posts: 555
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 31 Post(s)
Likes: 0
Liked 10 Times
in
8 Posts
Both the Hutchinson and the Bontrager have wire beads. So it's likely that they are not looking for a hook on the rim.
The usual suspect is that that the tire is resting on the tube where it sticks out. I'll usually put one bead on the rim; then the tube and inflate it slightly and then the other bead by hand. I'll press against the slightly inflated tube while pushing the bead in to make sure the bead does not rest on top of the tube. I'll let out pressure to make it easier to move those final few inches of bead onto the rim. I'll then start inflating the tire. I'll look to make sure that it's evenly spaced around the rim.
Assuming that you have not made a mistake in mounting the tire, here are some more tricks. I'd use a smaller width tube - say 25 mm. It will inflate fully, but when partially inflated there's more room for the tire and tube to exist side by side. I'd use talcum powder to make the tube and tire slippery. That way if either finds a place to catch on one another or the tire on the rim, they may slide off. I'd inspect the rim to see that there are not any burrs that might catch the tire and keep it from assuming its normal position.
The usual suspect is that that the tire is resting on the tube where it sticks out. I'll usually put one bead on the rim; then the tube and inflate it slightly and then the other bead by hand. I'll press against the slightly inflated tube while pushing the bead in to make sure the bead does not rest on top of the tube. I'll let out pressure to make it easier to move those final few inches of bead onto the rim. I'll then start inflating the tire. I'll look to make sure that it's evenly spaced around the rim.
Assuming that you have not made a mistake in mounting the tire, here are some more tricks. I'd use a smaller width tube - say 25 mm. It will inflate fully, but when partially inflated there's more room for the tire and tube to exist side by side. I'd use talcum powder to make the tube and tire slippery. That way if either finds a place to catch on one another or the tire on the rim, they may slide off. I'd inspect the rim to see that there are not any burrs that might catch the tire and keep it from assuming its normal position.
12-22-09, 01:01 AM
#4
cab horn
Join Date: Jun 2004
Location: Toronto
Posts: 28,353
Bikes: 1987 Bianchi Campione
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 26 Times
in
19 Posts
Lol.
If the bead doesn't' seat it's a friction problem. Soapy water, Tri-flow, slightly higher pressure will all overcome this to help seat the tyre. When you spin the wheel if the tire does not noticeably dip at that one spot then it is perfectly fine.
If the bead doesn't' seat it's a friction problem. Soapy water, Tri-flow, slightly higher pressure will all overcome this to help seat the tyre. When you spin the wheel if the tire does not noticeably dip at that one spot then it is perfectly fine.
12-22-09, 07:09 AM
#5
Junior Member
Thread Starter
Join Date: Sep 2009
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Thanks for the input guys! Sounds like (my) operator error to me. I didn't have time to mess with the project bike this morning, but I'll pick up some talc for the tubes on the way home. I'll check the rims for burrs and then reseat the tires with a talc'd tube and post results. I love this forum.
But still, does that line have a name?
But still, does that line have a name?
12-22-09, 03:07 PM
#6
Senior Member
Join Date: Nov 2009
Posts: 78
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I think they're called "that little line right above the edge of the rim"......
+1 - Spray a little soapy water or windex where the tire meets the rim after you've mounted it and pump up over the max pressure. They'll usually pop into place and then give you less trouble. I wouldn't recommend tri-flow since that could leave residue that could get onto the braking surface.
There's some slight variation in the actual dimensions that wheels and tires get manufactured to. Since it's happening with multiple tires, I would guess your rims are ever so slightly larger than normal. Not a big deal, but it makes getting the tire seated right a hassle. Once a tire's been mounted, they're usually easier to get on right the next time you remove/install it.
+1 - Spray a little soapy water or windex where the tire meets the rim after you've mounted it and pump up over the max pressure. They'll usually pop into place and then give you less trouble. I wouldn't recommend tri-flow since that could leave residue that could get onto the braking surface.
There's some slight variation in the actual dimensions that wheels and tires get manufactured to. Since it's happening with multiple tires, I would guess your rims are ever so slightly larger than normal. Not a big deal, but it makes getting the tire seated right a hassle. Once a tire's been mounted, they're usually easier to get on right the next time you remove/install it.
