Could someone explain the high pressure tire?
10-09-09, 06:50 AM
#1
Air conditioned Hippie
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Could someone explain the high pressure tire?
Its almost time for some new rubbers on my bike. When I look down at the tires while I am riding They look a little flat. Last time I pumped up the front tire, I tried to put a little too much pressure in there because the tube blew while I was pumping it up. So I am wondering is it the tube that is "high pressure" or the tire or both. I have thought about getting some kevlar tires...is it worth the extra cheese. I dont ride off road but do ride a little ways away from home and would like to avoid a flat and to have less rolling resistance. pre thanks.
10-09-09, 07:06 AM
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How long of an answer do you want?
1. Bicycle inner tubes are like balloons. None of them will hold very much pressure unless they are contained in a tire. Tires are pressure rated by size and construction. They will have a maximum inflation pressure indicated on the sidewall.
2. Many bike tires have kevlar belts under the tread that reduce (but won't completely eliminate) punctures. Whether or not they are worth the extra money depends on where you live and ride.
1. Bicycle inner tubes are like balloons. None of them will hold very much pressure unless they are contained in a tire. Tires are pressure rated by size and construction. They will have a maximum inflation pressure indicated on the sidewall.
2. Many bike tires have kevlar belts under the tread that reduce (but won't completely eliminate) punctures. Whether or not they are worth the extra money depends on where you live and ride.
10-09-09, 07:52 AM
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Short version please. Not the dinotte tail light version... I have a 700c tire size. I believe i am running at around 40 psi, I know I read somewhere that people were running over 100psi and so what tube and tire would take that pressure?
10-09-09, 09:18 AM
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I put in my combined weight for me and my road bike: 180lbs.
Did the advised 60/40 split for the weight distribution: 108/72 lbs
Fot 23c tires the chart gave me recommended pressures of 112/75psi!
That's a big pressure difference.
A 55/45 split gives me 80/100psi which seems more normal.
Now I'm curious as to how differently I'm loading each tire.
I don't have a scale.
10-09-09, 09:24 AM
#7
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I put my road bike on my scales, and found I had 140 pounds on the rear tire, and 70 pounds on the front.
i.e. 67/33 distribution.
So I am skeptical of the weight distribution shown in that doc.
10-09-09, 09:37 AM
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I'm skeptical of the whole thing. First of all, my bike apparently weighs nothing. Front wheel with me on is 65 lbs, rear 115 = 180. That's what I weigh without the bike. So I tried it with just the bike. Sure enough, 0.00. I'd blame my scales, but I'm guessing it's the idiot trying to use them.The other reason I'm skeptical, is that the weight distribution is going to vary depending on whether I'm upright or over the bars. Right?
10-09-09, 09:52 AM
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I just inflate to about the max rating on my road bike.
Many things can cause a blowout. Tube pinched between tire and rim is common.
Many things can cause a blowout. Tube pinched between tire and rim is common.
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10-09-09, 11:30 AM
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Interesting chart, I've never read it before, but it's nearly the same way I inflate my tires. More by look and feel than pressure readings. (I really have no idea what the pressure is in any of my bikes)
Basically I inflate the tire untill I can feel the surface texture of the road through the bars while riding, then back off pressure till I don't. I then look to see what the bulge looks like, and before every ride look at the tires with weight on it.
Short answer is that it's the tires that are high pressure, tubes are only to hold the air, and will expand to fill the tire.(within limits)
Ken.
Basically I inflate the tire untill I can feel the surface texture of the road through the bars while riding, then back off pressure till I don't. I then look to see what the bulge looks like, and before every ride look at the tires with weight on it.
Short answer is that it's the tires that are high pressure, tubes are only to hold the air, and will expand to fill the tire.(within limits)
Ken.
10-09-09, 12:16 PM
#12
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When you check weight distribution the bike must be level and feet on the pedals.You'll need help.Floor needs to be level also.Move around an inch or two while on the scale and you'll see how much things change for a small movement.
10-09-09, 01:19 PM
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I'll have somebody weigh me after I die. I can wait.
10-09-09, 01:22 PM
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The bicycle weights, maybe, 30 pounds or approxmately 15 lbs per wheel. A few pounds one way or another isn't important.
Scales might be inaccurate at low total weights. Try weighing yourself holding the bicycle and subtracting your weight.
Last edited by njkayaker; 10-09-09 at 01:31 PM.
10-09-09, 01:58 PM
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Well I have changed a few tires in my day. I am a Phd Harley Davidson, although I am not going to say thats not possible. She gave out at a pretty high pressure. I used some soapy water just like I would on a regular(motorcycle tire). What I am wondering is what is the description of the high pressure tire. I gather that I should go to the LBS and just look at the sidewall.
10-09-09, 02:08 PM
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Yes, all bike tires I've seen have the pressure rating on the sidewall. I usually go about 10-15 PSI lower than the rating. Mostly for comforts sake. Go too much lower and you run the risk of pinch flats.
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10-09-09, 02:45 PM
#17
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I'm doing some serious speculation here, but I speculate that pressure ratings on tires are more related to what the rim will stand up to, rather that the rubber and cord. A 700C x 40 at a given pressure is going to exert a lot more force on the rim than a 700C x 21 at the same pressure.
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10-09-09, 05:07 PM
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ebonyresearch, there are two parts of a tire that would be made of Kevlar -- the belt, as mentioned before, and the bead, the edge of the tire that hooks into the wheel rim. Tires with wire beads (literally, a hoop of metal wire) hold their shape when off the wheel and are quite stiff. A Kevlar bead allows the tire to be folded flat for storage purposes, saves weight, and is still sturdy enough to be useful (Kevlar has very little stretch, even comparable to steel of the same diameter). When you see a tire listed as two versions in a catalog, and one says "Kevlar", it's probably got a Kevlar bead instead of wire.
Also, having the tube blow while pumping it up was likely an installation error and not the fault of too much pressure (that is, if you're not significantly pumping beyond the pressure rating of the tire). Installing the tube with a fold in the rubber or letting it get caught between the tire bead and rim will create a weak spot. If it's pinched between the bead and rim, it will work its way back out and, without the tire to contain it, it expands and pops like a balloon.
10-10-09, 08:57 AM
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This makes more sense. When Harley switched to the belt drives they showed us a pic of the kevlar band in the belt. running lengthwise 7 times through the belt. They showed us a pic of a single strand holding an F-150 suspended in the air.
10-10-09, 10:38 AM
#21
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I'm doing some serious speculation here, but I speculate that pressure ratings on tires are more related to what the rim will stand up to, rather that the rubber and cord. A 700C x 40 at a given pressure is going to exert a lot more force on the rim than a 700C x 21 at the same pressure.
I had some semi-smooth 26" x 1.9" tires that were rated at 70psi, so that was what I ran in them.
After *twice* cracking the sidewall of a Mavic mtn rim, I finally realized that was more than the rims could handle.
10-10-09, 05:41 PM
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HELL NO! I worked for Harley Davidson and got my fill of the bull! Worked for an Import Yamaha and Suzuki dealership before I moved which frankly was so much nicer. The people that loved to ride rather than participate in a costume party. It was also nice to have such a diversity of riders from working on the side by sides to quads to dirt bikes and cruisers, and then the water craft, which I could do without... I used to own Chico's Custom in Greenville Texas back in 2002 and 2003. I still restore on my own 1 at a time. Which is much more enjoyable and not such a "bolt on the chrome fest". Graduated from MMI Orlando in 2007, I love to ride anything with wheels on it!
Now I fix computers - its a cake walk compared to motorcycles and much better paying without the constant payment to the snap on truck. Still doing my research in electroculture and working on Motorcycles at night though.
Now I fix computers - its a cake walk compared to motorcycles and much better paying without the constant payment to the snap on truck. Still doing my research in electroculture and working on Motorcycles at night though.
Last edited by ebonyresearch; 10-11-09 at 07:55 AM. Reason: forgot something.
10-11-09, 09:28 PM
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The pressure ratings on the tires are definitely not the maximum pressure rating that the tires can take (otherwise, how would it be able to take your weight?). Those ratings are likely determined by a bit of number crunching at the company at where they think the maximum "safe" pressure is. Safe meaning with a negligible amount of "incidents" of tires blowing up and such.
