Tire Pressure???
Thread started by
digablesoul at 07.17.09 - 12:33 pm
Tire pressure question...
So my tire sidewall has a hole through it. I ran Conti Gatorskins(GS) 700x28 and had the pressure at 100 psi. The GS that I have has it rated at 116psi max. Now my thought of running the pressure on tires is that if I keep my psi just below the max amount that it would help counter my heavy ass (260+) so the pressure, with me on it, would make it be at 116psi. Now… since it blew… should I have the psi a lot lower so that it can absorb… let’s say a small pothole? Or would running at max make it easier to pop? I’m confused here. I called an LBS and they said that running at a lower pressure, in addition to my weight (major factor), made the sidewalls easier to flex which ultimately made the hold on the sidewall. But I’m thinking if I hit the hole at max pressure… there’s no way for the tire to compensate the additional hit. Whaaaa?? Need help!
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That's what I heard too, lower tire pressure is bad, even for us heavier ridaz.
X-Large07.17.09 - 12:40 pm
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If the tire separated from the bead and blew up part of the bead and surrounding area, I'd look at your wheel, or the tire maybe wasn't seated right in the first place.
Running at a "lower pressure" would make you more susceptible to pinch flats but slightly lower should be ok, slightly more flex or not. Running at max pressure I don't think would hurt either, rubbers pretty tough.
I usually run just under the max pressure or close to it if I pay attention, usually kinda flat but not too flat...
Try a wire beaded tire and make sure its seated in the rim correctly? check your rims, dented?
dave07.17.09 - 1:05 pm
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More importantly what is your riding style? Commuter? Looking for faster road performance?
At your weight, I would go with something wider than 28c, it wont be as fast, but i dont know if your 260lb+ ass is fat or just heavy from all your muscles bulging out...
if just fat, get a wider tire and it will help make your city riding more enjoyable. Potholes wont be as much of a problem...
You can have some real fun testing your frame/fork clearance, and see if any 29er slick tires will fit or basically more of a hybrid-ish 700c... depends on your rim width and assuming as a rider pointed out, your rims are in good condition
md207.17.09 - 1:16 pm
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you dont want your tires/tubes to absorb shock, then they get blowouts... If you are on the heavier side you want to be right up to the max pressure.
larsenf07.17.09 - 1:27 pm
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depends on the type/size of hole and also whether the innertube is actually coming out of said hole. save yourself the worry and just get a new tire or put in a boot at least. and run it at the max recommended psi.
tfunk40807.17.09 - 1:30 pm
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I should have noted...
Tire pressure is inexpensive (free) suspension.
MTB riders like to ride a little over 20lbs of pressure.. especially if riding rigid.
You can use the same idea on the rough streets, but with more pressure than trail use of course...
what kind of bike do you have?
md207.17.09 - 1:35 pm
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@digablesoul
Pinch flats are the most common type of flat on the ride, especially with the heavier folks. 700c wheels and tires are designed for high pressure. I would run them at the max presure listed on the side of the tire.
Running low pressure will give you more flats not less.
If you are worried about the extra weight you can always run a wider tire. I like to run 700 32c, thats pretty wide, on the back of my tallbike cause the extra frames adds a bit of weight to the bike.
Wider tires will flex less on the sidewall even under heavyt load.
It seems wseird that you got a sidewall blowout though. Those usually come from some sort of sharp object hitting the sidewall and creating a small slit in the tire then the tube will bulge out of the hole and get popped by friction with some other object.
Try a new tire corectly inflated and check it every few days to make sure it is still up there.
stillline07.17.09 - 1:37 pm
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I blew out the sidewall on a Gatorskin a few months back and I suspected over pressurization because it was a hot day. I e-mailed the customer service at Continental. They got back to me pretty quickly; one thing they said was that the pressure ratings on the tires are actually quite conservative - in fact you can go way over that rating before the tire will blow from pressure. But they also warned against mounting the tire with metal tire irons (which in fact I had) so I'm now pretty much convinced that was the cause of my blow-out.
mr rollers07.17.09 - 1:37 pm
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sorry, dude, not true.. well partly true...
you have a range of pressure to work with along with your own weight... running on the lower end of pressure gives you more cushion... doesnt mean you can run as low as you want though... you have to take your weight and terrain into consideration...
md2 responding to a
comment by larsenf
07.17.09 - 1:38 pm
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the point is this:
if you want to run skinny tires: you need a lot of pressure, but why do you want skinny tires if youre 260+ lbs?
Get a fatter tire, and pump it max or a little below if you want...
True if you're heavy, you have to pump more lbs or air... but wider tires and lower ends or YOUR range, will absorb more of the terrain.
Get FATTIES... you dont need skinny tires.
md207.17.09 - 1:42 pm
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Thanks for the replies everyone…
What I’m riding… converted 80’s nishiki fixie/ss on.. Velocity Deep V’s…
I’ve checked the rims and their good. I lined up the tire logo w/ the valve stem (thanks User1) So it can help me find issues and the area was good.
Yup… I’m commuting… and did hit a rough part but it was bumpy… but no pot holes. Kinda when asphalt spreads and resembles like a dry lake bed
@rollers…
Were they able to do anything for you on your tire? Like if it was defective? I guess it would be hard to put some sort of guarantee on tires cause of so many factors.
So I guess I’ll go wider. 700x32 in the rear? Or wider? Then. I’ll keep tires at recommended tire pressure. Make sure it’s seated correctly. And I should be good. I just don’t get it. Maybe I just have bad luck this bike. My other road bike w/ the tunes on my rack run the 700x28 conti gatorskins on velocity deep v’s and I’ve never really had a problem with it
Hey.. Any way one can see if you’re frame can take a wheel before purchasing? Like how would I measure? And… is 700x32 just right for me?
Man… I’ve got lose weight…. =(.. This is good though!!! Motivation baby!!
digablesoul responding to a
comment by md2
07.17.09 - 2:32 pm
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Nah, they didn't offer and I didn't think it was worth pressing the issue. I've chalked it up to "user error" and filed it under "lessons learned".
I still think they're great tires though and still use them. If this was a common problem I think we'd be hearing about a lot more of these failures.
mr rollers responding to a
comment by digablesoul
07.17.09 - 3:32 pm
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I found this
Tip 1 - Inflate your tires before every single ride. Know what the proper inflation pressure should be for your tires. Inflation requirements will vary by rider, bike, tires, conditions, etc.
Below you will find equations that you can use to help determine an appropriate starting point using your weight and the tire's size. Adjust from these baselines to suit needs and conditions.
Proper inflation is the easiet way to avoid flats.
Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33
Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67
Example: You are 150lbs running 28's
Pressure (psi) = (0.33*150) +33.33 = 82.83psi (rear)
Front Pressure = .9*Rear Pressure = .9*82.83psi = 74.55psi front
Gav07.17.09 - 3:38 pm
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Diagblesoul,
First let me encourage you to keep riding... lose the weight, and have fun. Stay focused and shed pounds in virtue of putting your ass on the perfect machine built with human being as a motor.
Second, go to a shop and recall what i said...
find out your rims width... and the max tire width your rim can/should hold. So with that tire.
Why?
1. youre looking to shed pounds and communte... both dont require skinny tires.
2. you'll make your ride more comfortable and have a nice selecting of commuter tires available.
you can probably just look up your rim specs online, but go to a shop, and dont let them sell what they have, only buy if they have the options...
go wide, you'll thank me for it
md2 responding to a
comment by digablesoul
07.17.09 - 3:46 pm
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I think you need bigger tires and less pressure.
700x32 or 35 at around 90-100psi.
If your Nishiki originally came with 27" wheels they will fit.
Deep Vs are great road rims for clydesdales (but way too harsh and stiff for pretty much anyone else)
richbell07.17.09 - 4:17 pm
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Digable,
Just get a new tire and try again, blowouts happen.
I outweigh you by a whole bunch, and have been fine rolling on generic 700x23s pumped to 100-110psi. If you're heavy, you do need to keep it close to the max pressure, but blowouts are unpredictable (and you may want to run it slightly softer (80-100) for a better ride quality (although slower). Just make sure the tires aren't noticeably flexing/ballooning out to the side as you ride.
Occasionally you're going to hit a pothole funny or run over something and blow out the tire, but that happens to everybody, regardless of weight.
It's just one blowout, and you've been riding for a while, so don't worry about it. If you start blowing them out consistently, then you might need to consider additional steps.
JB07.17.09 - 6:01 pm
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Google "Jan Heine - Optimized Tire Pressure" . He has a very comprehensive article on how to determine tire pressure. Basically it breaks down to tire deflection due to weight....the more you weight, the greater the tire pressure. The numbers printed on the side of the tires are just guilds, one size fits all philosophy. Remember that the weight distribution on a typical bike is 40% up front, 60% in the rear, therefore the rear tire should carry more air than the front.... I'm 200lbs... I run 700X25's on one bike & 700X28 on another... the 25's feel a little harsh, but fast.... if I'm running extra weight, panniers etc, the 28's feel great. You'll probably over the "listed pressure, I agree that most decent tires can handle the extra pressure. Spend the money & get good kevar tires.
Buddha-head Steve07.17.09 - 7:18 pm
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I thought this was gonna be another Pier Pressure ride!! :(
BICYKILLER07.17.09 - 8:32 pm
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