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Old 10-04-12, 11:21 PM   #1
granto
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Did a 25mm tire ruin my 23mm rim?

Hello all,

So last year at the LBS they guy recommended I replace the stock knobby 32mm tires on my new bike with specialized all condition armadillos on my WTB dx23 rims. Thing is, there weren't any 28mms laying around, and he threw some 25mms on after asking another guy's opinion, who said I'd be fine. Not really knowing anything at the time about tire sizing, I didn't think much of it, and was generally pleased with the tires.

So one day my rear rim gets a nasty inward bend in it with a sidewall protrusion that truing just isn't going to fix. Maybe from a pothole or something, I'm not sure- I definitely liked to ride at around 115 psi but I didn't do anything extreme, just some basic city commuting. So I brought it in and they said they probably wouldn't be able to fix it if I couldn't. I then went to a local bike co-op and the guy had the correct tool to pull the rim out, but the rim has since bent on me again in new and exciting ways and things are generally going downhill. I've since learned form Sheldon that you risk rim damage from using a narrow tire on a wide rim, and this combination is definitely in the red zone.

What are your thoughts on this? Was it bad advice? I've since bought a new (24mm) rim, and want to put a 28 on it (which Peter White says is acceptable). Do you think it would be unreasonable to ask for a free replacement with a more reasonable size (28)? Since they didn't seem to be capable of fixing the old rim, there's not much I could ask them to do short of helping me pay for my new rim, and I thought asking for the tire they should have sold to me in the first place was a better approach. Or do you think I'm splitting hairs between the 25 and 28 and they are both running too narrow for the rim?
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Old 10-05-12, 05:57 AM   #2
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Originally Posted by granto View Post
I definitely liked to ride at around 115 psi but I didn't do anything extreme,
115# in that rim might have been extreme. IIRC, that rim is not rated for such high pressure, and at the very least, the wheel should have been gone over to bring the tension up to an adequate level.
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Old 10-05-12, 07:33 AM   #3
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I think that both sizes were fine for the rim and you want to blame someone else for damage caused by crappy roads. The Sheldon chart is notoriously conservative.

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So one day my rear rim gets a nasty inward bend in it with a sidewall protrusion that truing just isn't going to fix. Maybe from a pothole or something
Ah, a classic "I was just riding along!" story. Rims just don't get damage like that, you hit something, something hit you or it was damaged during service. Sounds like you hit something to me.

I've got several thousand miles running 23/25/26 size tires on a 22.5 width rim (CR18) with no damage or other issues to the rim. I have hit a pothole hard enough to get a pinch flat and blow out several sidewall threads in the tire, rim was fine. Ride wider tires, swerve those potholes and be personally responsible.
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Old 10-05-12, 08:17 AM   #4
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Originally Posted by granto View Post
Hello all,

So last year at the LBS they guy recommended I replace the stock knobby 32mm tires on my new bike with specialized all condition armadillos on my WTB dx23 rims.
You had a 32mm on a 23mm rim? Is this correct? If that is the case, why whould you believe that a 25mm will ruin the 23mm?

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Thing is, there weren't any 28mms laying around, and he threw some 25mms on after asking another guy's opinion, who said I'd be fine. Not really knowing anything at the time about tire sizing, I didn't think much of it, and was generally pleased with the tires.

So one day my rear rim gets a nasty inward bend in it with a sidewall protrusion that truing just isn't going to fix. Maybe from a pothole or something, I'm not sure- I definitely liked to ride at around 115 psi but I didn't do anything extreme, just some basic city commuting. So I brought it in and they said they probably wouldn't be able to fix it if I couldn't. I then went to a local bike co-op and the guy had the correct tool to pull the rim out, but the rim has since bent on me again in new and exciting ways and things are generally going downhill. I've since learned form Sheldon that you risk rim damage from using a narrow tire on a wide rim, and this combination is definitely in the red zone.
This is not the case on your story. 25mm is wider than 23mm, at least in the old math.

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What are your thoughts on this? Was it bad advice? I've since bought a new (24mm) rim, and want to put a 28 on it (which Peter White says is acceptable). Do you think it would be unreasonable to ask for a free replacement with a more reasonable size (28)? Since they didn't seem to be capable of fixing the old rim, there's not much I could ask them to do short of helping me pay for my new rim, and I thought asking for the tire they should have sold to me in the first place was a better approach. Or do you think I'm splitting hairs between the 25 and 28 and they are both running too narrow for the rim?
Thoughts? You may be trying to get a free rim for free and blaming someone else.
You "hit a pothole or something" is more probable than just your 25mm tire ruining a 23mm rim.


Replace the rim and pay for it. No free rim for you.
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Old 10-05-12, 08:55 AM   #5
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I think that both sizes were fine for the rim and you want to blame someone else for damage caused by crappy roads. The Sheldon chart is notoriously conservative.
I don't want to blame anyone, which is why I'm asking your advice.

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You had a 32mm on a 23mm rim? Is this correct? If that is the case, why whould you believe that a 25mm will ruin the 23mm?
The 32 is appropriately wide for a 23mm rim. From every indication I've seen (even beyond the Sheldon chart), the 25mm is pushing it as too narrow for this rim. You will see anecdotes like the one given by Spoonrobot, but the rim is more prone to damage with tire that's on the narrow side.

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Sounds like you hit something to me
Nah I never hit anything except the occasional pothole/bump. Though we do get some nasty ones here.

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115# in that rim might have been extreme. IIRC, that rim is not rated for such high pressure, and at the very least, the wheel should have been gone over to bring the tension up to an adequate level.
Yeah that's probably right. The tire was rated for 115 but I had no info on the rim's pressure rating (still can't find it). They're not the greatest of rims. Also, the tension wasn't adjusted which could have been the problem... come to think of it some of the spokes were loose so this is probably the main culprit.

So it was probably mostly high psi and improperly tensioned spokes, and the narrow tires may have exacerbated that but it's really a moot point. Thanks!
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Old 10-05-12, 09:07 AM   #6
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I don't want to blame anyone, which is why I'm asking your advice.



The 32 is appropriately wide for a 23mm rim. From every indication I've seen (even beyond the Sheldon chart), the 25mm is pushing it as too narrow for this rim. You will see anecdotes like the one given by Spoonrobot, but the rim is more prone to damage with tire that's on the narrow side.



Nah I never hit anything except the occasional pothole/bump. Though we do get some nasty ones here.



Yeah that's probably right. The tire was rated for 115 but I had no info on the rim's pressure rating (still can't find it). They're not the greatest of rims. Also, the tension wasn't adjusted which could have been the problem... come to think of it some of the spokes were loose so this is probably the main culprit.

So it was probably mostly high psi and improperly tensioned spokes, and the narrow tires may have exacerbated that but it's really a moot point. Thanks!
It is unfortunate, but, anecdotes will not get you a free replacement rim. Pay for the rim and ride.
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Old 10-05-12, 09:19 AM   #7
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Originally Posted by granto View Post
The 32 is appropriately wide for a 23mm rim. From every indication I've seen (even beyond the Sheldon chart), the 25mm is pushing it as too narrow for this rim. You will see anecdotes like the one given by Spoonrobot, but the rim is more prone to damage with tire that's on the narrow side.
While the rim is a little wide for the tire, it's not that wide. Sheldon Brown's chart is very conservative.

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Nah I never hit anything except the occasional pothole/bump. Though we do get some nasty ones here.
There's your problem. Don't hit stuff. Spoke tension has nothing to do with it. Tire width has little to do with it. Tire inflation has more to do with it, although 115 psi is high enough. But the biggest problem is slamming the wheels into holes.

Okay, sometimes you can't avoid them but you can mitigate the damage by the way in which you ride. Most people ride a bike like it's a lounge chair...they sit on it and just slam into stuff. Don't do that! Even a rigid bike has suspension and you need to learn to use it. The suspension is you, more specifically your arms and legs. Float the bike by using your legs and arms to absorb the shocks rather than making the wheels and tires do it.

"Hover" over the saddle...it is not a "seat"...even while pedaling. If you coast or are going to hit a pothole, let your legs and arms flex...the harder the hit, the more flex you need...to absorb the shock. Even mountain bikers with several inches of suspension travel ride this way.
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Old 10-05-12, 10:06 AM   #8
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You seem to have some doubt about the ability of the WTB DX-23 rims to handle 115PSI. Personally I'd think your V-brakes put out more force than that from the outside. Brake boosters were introduced to reduce frame spreading by V-brakes so there are high loads on the rim walls regardless of the tire pressure inside.

I'd suggest your real issue was insufficent spoke tensioning - part of normal wheel maintenance, compounded by poor road conditions and possibly your weight - which you haven't yet mentioned. This was described as a 'new bike'. Was that 'brand new with warranty' or just 'new to you'?
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Old 10-05-12, 10:22 AM   #9
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Narrow tires used on streets with bad potholes will always have the potential to cause damage to the rim no matter what the rim's width is. Keeping the tire pressure high makes this less likely to happen and I'd suspect that the pressure may have been well below 115 psi on the day you damaged the rim. Insufficient spoke tension will make it more likely that you'll have the rim go out of true and that spokes will break due to fatigue, but it won't increase the risk of bending a rim sidewall.

I presume you wanted some of the performance advantages of narrow tires (lower weight, more aerodynamic), so I wouldn't blame the bike shop for selling you those tires. They had no way of knowing whether you'd be careful about avoiding potholes.
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Old 10-05-12, 11:29 AM   #10
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DX23's are 18mm wide on the inside. That's the measurement that counts for Sheldon's chart, and it's close enough to the "green zone" for 25mm tires that it was not the cause of your problem.
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Old 10-05-12, 02:35 PM   #11
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I'd suggest your real issue was insufficent spoke tensioning - part of normal wheel maintenance, compounded by poor road conditions and possibly your weight - which you haven't yet mentioned. This was described as a 'new bike'. Was that 'brand new with warranty' or just 'new to you'?
Yeah I think it's a tensioning problem- I was riding the wheels right out of the factory. I'm about 190 lbs but I do "hover" over the seat as someone suggested. I also inflated the tire weekly. Bike was brand new- 2010 Bianchi Volpe. Not sure about the warranty.
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Old 10-05-12, 02:55 PM   #12
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Yeah I think it's a tensioning problem- I was riding the wheels right out of the factory. I'm about 190 lbs but I do "hover" over the seat as someone suggested. I also inflated the tire weekly. Bike was brand new- 2010 Bianchi Volpe. Not sure about the warranty.
Warranty is normally one year minimum on everything on the bike. But thats also dependent on proper maintenaince being done as required and in many cases, may exclude road damage.

So here's the suggestion: Have your next set of wheels checked for proper tensioning at the shop, check them ocassionally (once a month) for loose spokes, and have any loose spoke issues addressed IMMEDIATELY. A decent set of wheels, properly tensioned, will outlast an expensive wheel set with poor spoke tension.
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Old 10-05-12, 04:56 PM   #13
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Yeah I think it's a tensioning problem- I was riding the wheels right out of the factory. I'm about 190 lbs but I do "hover" over the seat as someone suggested. I also inflated the tire weekly. Bike was brand new- 2010 Bianchi Volpe. Not sure about the warranty.
Daily. Every two days at most. You may not notice a drop from 115 PSI to 70 PSI, but if you hit something your rim will.
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Old 10-05-12, 04:56 PM   #14
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Originally Posted by granto View Post
Hello all,

So last year at the LBS they guy recommended I replace the stock knobby 32mm tires on my new bike with specialized all condition armadillos on my WTB dx23 rims. Thing is, there weren't any 28mms laying around, and he threw some 25mms on after asking another guy's opinion, who said I'd be fine. Not really knowing anything at the time about tire sizing, I didn't think much of it, and was generally pleased with the tires.

So one day my rear rim gets a nasty inward bend in it with a sidewall protrusion that truing just isn't going to fix. Maybe from a pothole or something, I'm not sure- I definitely liked to ride at around 115 psi but I didn't do anything extreme, just some basic city commuting. So I brought it in and they said they probably wouldn't be able to fix it if I couldn't. I then went to a local bike co-op and the guy had the correct tool to pull the rim out, but the rim has since bent on me again in new and exciting ways and things are generally going downhill. I've since learned form Sheldon that you risk rim damage from using a narrow tire on a wide rim, and this combination is definitely in the red zone.

What are your thoughts on this? Was it bad advice? I've since bought a new (24mm) rim, and want to put a 28 on it (which Peter White says is acceptable). Do you think it would be unreasonable to ask for a free replacement with a more reasonable size (28)? Since they didn't seem to be capable of fixing the old rim, there's not much I could ask them to do short of helping me pay for my new rim, and I thought asking for the tire they should have sold to me in the first place was a better approach. Or do you think I'm splitting hairs between the 25 and 28 and they are both running too narrow for the rim?
One of the ways some companies keep prices down is by shorting people on their rims. Many times it helps to look up the reviews of a rim you have questions about. Unless you have a rim built by someone you trust you are at the mercy of what came stock on the bike. The rim not the tire is the questionable part of your problem. http://www.mtbr.com/cat/tires-and-wh...92_139crx.aspx
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Old 10-05-12, 06:59 PM   #15
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It's just a part of cycling, you bugger a wheel once in a while. Buy a new rim and lace it up. Get used to it, it will happen again and again and again.........

Bike wheels, frames, bars, pedals all will bend if subjected to the right force. Its a bike not a tank.
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Old 10-05-12, 08:13 PM   #16
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Okay, sometimes you can't avoid them but you can mitigate the damage by the way in which you ride. Most people ride a bike like it's a lounge chair...they sit on it and just slam into stuff. Don't do that! Even a rigid bike has suspension and you need to learn to use it. The suspension is you, more specifically your arms and legs. Float the bike by using your legs and arms to absorb the shocks rather than making the wheels and tires do it.
This seems to be the way a person needs to ride a bike with 25mm tires, which need to be inflated up in the 115 or even 120 or 125 psi zone. That's great on smooth roads or for racers who can ride under somewhat controlled conditions. With a loaded bike - groceries or school books or camping gear - on rough roads that maybe you're not familiar with, in traffic that requires attention and makes it difficult to see or avoid road hazards, then fatter tires at lower pressures have a lot of advantages!

Knobby tires are good for loose surfaces but when you're on pavement, smooth tires are best. My rims have 19 mm inner width and I ride with 50 mm wide tires - I push Sheldon in the other direction! But really, if your rims are 18 mm inside, you could try 37 mm tires, inflated to 60 or 65 psi. If you had 32 mm knobbies, probably 37 mm smooth tires would fit. Tires like those can handle rough roads with a lot less effort and attention! Panaracer Pasela TourGuard are popular and would be one good candidate.
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Old 10-06-12, 01:23 PM   #17
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This seems to be the way a person needs to ride a bike with 25mm tires, which need to be inflated up in the 115 or even 120 or 125 psi zone. That's great on smooth roads or for racers who can ride under somewhat controlled conditions. With a loaded bike - groceries or school books or camping gear - on rough roads that maybe you're not familiar with, in traffic that requires attention and makes it difficult to see or avoid road hazards, then fatter tires at lower pressures have a lot of advantages!

Knobby tires are good for loose surfaces but when you're on pavement, smooth tires are best. My rims have 19 mm inner width and I ride with 50 mm wide tires - I push Sheldon in the other direction! But really, if your rims are 18 mm inside, you could try 37 mm tires, inflated to 60 or 65 psi. If you had 32 mm knobbies, probably 37 mm smooth tires would fit. Tires like those can handle rough roads with a lot less effort and attention! Panaracer Pasela TourGuard are popular and would be one good candidate.
wut?

I'm 200+ lbs, and I race on 25s at 95-100 psi.
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Old 10-06-12, 02:05 PM   #18
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I'm 200+ lbs, and I race on 25s at 95-100 psi.
For 25 mm tires, Schwalbe recommends 100 psi or 7 bar (105 psi) when the rider is 165 pounds. Heavier riders should scale up. If you are 20 kg more, then you want to be in the 120 to 125 psi zone. Of course that depends on the specific tires and rims too. But skinnier tires can take higher pressures and put less stress on the rims.

http://www.schwalbetires.com/tech_in...ation_pressure
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Old 10-06-12, 06:11 PM   #19
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Edit: Nevermind, reread the original post. Still kinda sounds like you have worn through the rim, but it says the bend is inward? Pictures would help.

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Old 10-08-12, 07:43 AM   #20
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For 25 mm tires, Schwalbe recommends 100 psi or 7 bar (105 psi) when the rider is 165 pounds. Heavier riders should scale up. If you are 20 kg more, then you want to be in the 120 to 125 psi zone. Of course that depends on the specific tires and rims too. But skinnier tires can take higher pressures and put less stress on the rims.

http://www.schwalbetires.com/tech_in...ation_pressure

Still too high.

Every other recommendation is much lower:

http://sheldonbrown.com/tires.html#pressure

www.bikequarterly.com/images/TireDrop.pdf

http://www.michelinbicycletire.com/m...rpressure.view


And no, putting more air in the tire does not reduce rolling resistance.
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Old 10-08-12, 07:54 AM   #21
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I think that both sizes were fine for the rim and you want to blame someone else for damage caused by crappy roads... Sounds like you hit something to me... Ride wider tires, swerve those potholes and be personally responsible.
I'm with Spoon. Bikes (and parts) are pieces of outdoor equipment. If you use them, stuff is going to break occasionally. I weigh 240, and I've run tires from 19mm (back when I was stupid) to 41mm on all kinds of rims for 40 years. Every problem I've ever had could be traced back to me.
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Old 10-08-12, 12:15 PM   #22
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Reality check #1 - skinnier tires will always have less shock absorption capability than fatter tires.
Reality check #2 - rims should be considered maintenance parts. Sooner or later they WILL need replacing.
Reality check #3 - Going slightly outside Sheldon Brown's chart will not hurt anything.

The damage you describe probably came from hitting a pot hole. Pay to have the rim replaced and get on with your life.
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Old 10-08-12, 06:33 PM   #23
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Every other recommendation is much lower:

http://sheldonbrown.com/tires.html#pressure
For a 25 mm tire, Sheldon recommends 110 psi, given a 100 pound wheel load. A 210 pound rider on a 20 pound bike... 230 pounds total, could be 130 pound load on the rear. That would scale the pressure up towards 140 psi on the rear tire!

It's all theoretical for me: - I run my 50 mm tires at about 45 or 50 psi! But a big guy on 25 mm tires... the theory does suggest that pushing the pressure up into the 120 - 125 psi zone could well be worth the try!
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Old 10-08-12, 06:52 PM   #24
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Bikes: Thorn Nomad Mk2, 1996 Trek 520, Workcycles Transport, Brompton
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Quote:
Originally Posted by achoo View Post
And no, putting more air in the tire does not reduce rolling resistance.
Every place that I have read says that higher pressure reduces rolling resistance. It does get tricky though. Rolling resistance means the loss in energy due to deformation of the tire as it rolls. But the movement of the bike down the road can dissipate energy in other ways, which will slow the bike down just as much. Of course there is air friction. But also if the road is rough then the bike and rider etc. get jostled around which dissipates energy. It can also fatigue the rider, which impedes forward motions too. So higher tire pressure can make the bike slower, even though it might still reduce rolling resistance a bit.
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