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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 08-22-10, 09:23 PM   #1
erpdat
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MAX PSI and winter jacket

How many of you run maximum PSI? I've been running 20-30PSI under but was thinking about trying out max. Beneficial?

Also, I need to pick up a new jacket for the Fall/Winter. I was thinking about the Chrome Cobra hoodie. Anyone have any experience with this? I live in Portland and yeah, it rains a lot.

Thanks
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Old 08-22-10, 09:37 PM   #2
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two subjects, one post? huh. BF is never this concise...

tire psi: some say to run based on your weight. there's a chart/algorithm floating around here that takes into account tire size, and rider weight, and will spit out the psi to run at. I run at the "max" psi (whatever is listed on the tire) on the front, and I run overpressurized on the rear. For me, this equates to 110 front, 120 rear. I'm about 160 lbs, ride 23 tires, and this is great for me/city riding, and aside from mammoth potholes, I don't need to worry about pinch flats whenever I'm at these pressures. Anytime either tire dips to maybe 90 or below, I can definitely feel it when going over bumps/trolley tracks, and I get a bit nervous about flatting. IMO, if you generally have to worry about pinch flat avoidance, you're tires are too low.

running at higher PSIs WILL help pinch flat avoidance. Some say that higher pressure tires will also reduce rolling resistance, which kind of makes sense, but I've never seen any data to back this claim, just speculation and anecdotes.

jacket: actually, what with that other post about casual riding clothing, I was just thinking wondering about chrome clothing. It looks super nice, but it's also stupid expensive. if you do get it, please report back as to how it is. Otherwise, I'd imagine that you'd also need a wind/rainshell, and that might make a bigger difference. (for heavy rain/cold winter wind)
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Old 08-22-10, 10:14 PM   #3
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I have the Cobra. Considering how expensive all the other Chrome crap is, I can't believe how cheap this hoodie is! I mean, it's 100% Merino. Look around online for Merino hoodies, you won't find anything that even comes close to that price. If you're unfamiliar with Merino, let me just say that you will never want to take the thing off. It's super comfy, never stinky, keeps you warm when it's wet. It's cut great for skinny folks, though I thought the sleeves were just a hair too short. I can't comfortably ride while using the thumb loops. Otherwise, it's perfect. The huge pocket in the back is big enough for water bottles, books, food, small dogs, whatever you want. And then it's got that little bad-ass key-pocket by the right hand. Quality zippers…I could go on and on about how much I love it. Oh, one other thing I don't like about it: It's got metal caps at the end of the hood's drawstrings which are elasticized. I have hooked them on my bag while taking it off, the stretch and then POW I have these little metal rockets shooting back in my face. I am afraid that I'll lose a tooth with that someday. Gotta be careful about that! So, yeah, get it.
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Old 08-22-10, 10:16 PM   #4
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Another member provided this method for determining tire pressure, that I'm now using:

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
Front Pressure = .9*Rear Pressure
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Old 08-22-10, 10:25 PM   #5
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Hey hey P-lander! Ok I'm not in Portland but just right across the bridge. I'll be looking for Fall/Winter wear too (rain gear) soon here too.

I run max psi, didn't even know about a weight chart deal, and didn't care. But according to chart, my psi is 112 and max is 110, so I'm good either way
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Old 08-22-10, 10:43 PM   #6
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Damn, that's a good review! I am just wondering if it will be okay being constantly soaking wet. Last year I rode with a huge Northface jacket and even in December/January, it was too warm. Also, way too bulky and uncomfortable. I'm going to send Chrome an email and see what they say. They don't seem like the type of brand to scam a cyclist but I think I'm pulling the trigger later this week. Once I have it, I'll give my review as well. It's going to start getting chilly in PDX soon (Thank God)
I hate the sun/heat.

Turns out I need to be running about 100PS1 on both. (I'm 130 lbs.. err, last time I checked) But I cranked em up to 120PSI anyway, although max is 140 on each.

Thanks for the info, dudes.
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Old 08-22-10, 10:46 PM   #7
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Remember to lower ~5 PSI if you plan to ride in the rain.
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Old 08-22-10, 11:06 PM   #8
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i ride max. it feels faster.
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Old 08-22-10, 11:12 PM   #9
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i ride max. it feels faster.
Nothing wrong with that, especially if you ride on glass smooth roads. In the world I live in max tire pressure equates to a rough ride, so unless I'm racing I'll run a lower pressure for comfort at the expense of a little performance.
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Old 08-22-10, 11:41 PM   #10
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i ride max. it feels faster.
Seems to me that when my PSI is too high I feel less grip in corners, particularly bumpy/sandy/gravely ones.
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Old 08-23-10, 12:03 AM   #11
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Seems to me that when my PSI is too high I feel less grip in corners, particularly bumpy/sandy/gravely ones.
the only times I've had my bike slide out from under me was when I pumped too much air, but that's not really proof of anything, not to say I don't agree
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Old 08-23-10, 09:07 AM   #12
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+1 on merino wool hoodies.
I have one from Outlier and I love it. Would have gotten the Chrome Cobra had I known about it before i bought the Outlier. But i figure they should be the same thing and the Chrome has more pockets at the back. I'ld have gone with the Chrome.
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Old 08-23-10, 09:58 AM   #13
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I run max on my road bike (23s with 120psi) and on my Redline 925 (stock 28s with 100psi). If I were to use the formula TT shared, I would be running 25 psi under the max, which seems way underinflated. Obviously, it's not an exact thing and probably gets more wonky with really light or really heavy riders, so I just stick with the max.
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Old 08-23-10, 10:22 AM   #14
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Here is the bike tire calculator:
http://www.dorkypantsr.us/bike-tire-...alculator.html

That is going for the theoretical 15% drop (in sidewall height) for optimum ballance between ride and resistance.

I often ride at max 120 PSI, even though I should be at 80-90 according to the chart. But with rough roads it helps prevent pinch flats. Certainly if your ride is too bouncy, or you have issues with grip in corners or rough pavement, you can drop down to what is recommended for the 15% drop.
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Old 08-23-10, 10:26 AM   #15
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Where is a good place to by the Chrome Cobra?
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+1 on merino wool hoodies.
I have one from Outlier and I love it. Would have gotten the Chrome Cobra had I known about it before i bought the Outlier. But i figure they should be the same thing and the Chrome has more pockets at the back. I'ld have gone with the Chrome.
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Old 08-23-10, 10:56 AM   #16
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Run whatever tire pressure you feel comfortable with. I cranked my 23s up to 120 PSI, and while it did feel faster it also gave me a punishing ride. I had to look out for ever crack and bump which took some of the fun out of riding. For me, 90-100 PSI works well, but then again I weigh 130 lbs. (I also run the front at 5-10 PSI less than the rear.)

Question: does running too high a pressure put you at risk for bending a rim? The way I see it, if the air in the tire isn't taking the hit something else must be.

Last edited by FastJake; 08-23-10 at 10:59 AM.
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Old 08-23-10, 11:53 AM   #17
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Question: does running too high a pressure put you at risk for bending a rim? The way I see it, if the air in the tire isn't taking the hit something else must be.
The simply answer is no. The rim never sees the load from the road directly, unless you are running a very low pressure and / or hit a very sharp object hard enough to deflect the tire to the point that the rim contacts the road directly. Normally the rim only sees the air pressure in the tube, which is uniform and invariant as the tire contacts the road. Since the rim is compressed radially unformly by the air pressure, it does not bend or warp and all the load is carried in compressive hoop stress. The air pressure does reduce the spoke tension as the rim compresses circumferentially, but in a properly tensioned wheel not enough to impact the integrity of the wheel.
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Old 08-23-10, 12:49 PM   #18
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Where is a good place to by the Chrome Cobra?
um... online? iono.. Google says Tree Fort Bikes and Ben's Cycle carries some. LoRoK, input?
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Old 08-23-10, 02:02 PM   #19
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Where is a good place to by the Chrome Cobra?
Or the official Chrome website?
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Old 08-23-10, 04:25 PM   #20
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Some tires' maximum PSI is way higher than a rim could withstand, a BF member busted a rim because he pumped his tires to 150 PSI and it exploded when he was going ~25mph.
Partially full story here.



I've been using the "recommended" PSI for about a week now, I was over inflating my tires 10 PSI too high, which made my ride extremely erect and bumpy. Lowering to "recommended" PSI for my weigh made a ton of difference, no pinch flats, no more bumpy ride, and feel better when cornering.
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Old 08-23-10, 05:55 PM   #21
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Or the official Chrome website?
well yeah, but if you're dropping such cash on a hoodie, I think one would like to try it on. Especially if you're usually in-between sizing. (I'm a tall skinny dude. Medium stuff usually 'fits' correct, but is too short. large stuff is a bit baggy, but is long enough. And idk how much of a 'cycling' fit chrome uses for their clothes)

if your LBS carries chrome stuff, maybe you can sweet talk them into getting a few, and you can try them on. Otherwise, you'll have to order online.
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Old 08-23-10, 07:25 PM   #22
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What, the rim busted because of the tire inflation? That sounds pretty odd. more likely the rim had problems, and it took a hard hit because the tire wasn't absorbing anything at 150psi. The PSI is 1/2 of what the tire can withstand if mounted properly and on the proper rim.

Quote:
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Some tires' maximum PSI is way higher than a rim could withstand, a BF member busted a rim because he pumped his tires to 150 PSI and it exploded when he was going ~25mph.
Partially full story here.



I've been using the "recommended" PSI for about a week now, I was over inflating my tires 10 PSI too high, which made my ride extremely erect and bumpy. Lowering to "recommended" PSI for my weigh made a ton of difference, no pinch flats, no more bumpy ride, and feel better when cornering.
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Old 08-23-10, 07:37 PM   #23
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Exactly, when a tire pump to its maximum capacity, it will not absorb road bumps as well as it would when it's at a lower PSI.

Quote:
Originally Posted by The link
The crazy thing about all this is that, despite what most consumers think, there are plenty of scientific studies that show over-inflating tires actually increases rolling resistance of clincher tires (makes you slower). Over-inflation causes the tire shape to deform and to not contact the road surface smoothly. There are two other negative side effects of over inflation. The first is decreased traction and the second is less rider comfort. Zipp has done some great research in this area (see some of the links below) and they go as far as to list a narrow recommended tire pressure range for their tires (manufactured by Vittoria) based on the rider's weight and road / weather conditions.


The take away message here is to never inflate clincher tires more than 125 PSI. Remember that as heat increases so does air pressure. So cold tire pressure is different that a mid summer's day riding temperature. In addition the heat generated from braking will increase the air pressure of the tire. So it's best to use a tire designed to work optimally in the 110-125 PSI range and to take care that your tire is inflated to that range. Be safe, be fast and have some fun out there!
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Old 08-23-10, 08:22 PM   #24
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I don't know if you're adverse to the idea, but I have the Patagonia Slopestyle 2.0 Hoodie. It has a weather resistant coating that deals well with rain, is insulated to a decent degree and comes in a pretty nice range of colors. It's cheaper than the Chrome hoodie but might not fit a helmet and probably doesn't carry the street cred. Also if you get caught in a downpour wool will absorb a decent amount of moisture before it feels wet (way better than cotton) but can leave you totally soaked if the rain is bad enough. Wind might be an issue in merino as well.

The way I see it is that any of the hiking gear I have will meet the standards for my biking gear in terms of weight, weather protection, ventilation, etc. Might as well buy one piece to fit all needs.
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Old 08-24-10, 08:54 AM   #25
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and probably doesn't carry the street cred.
well that's a deal breaker...
ok i'm kidding. I was looking at some Patagonia hoodies before too. They seem pretty nice. Though I ended up going with a merino wool hoodie coz I have a water resistant shell on top of it sometimes when it gets too cold.

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The way I see it is that any of the hiking gear I have will meet the standards for my biking gear in terms of weight, weather protection, ventilation, etc. Might as well buy one piece to fit all needs.
+100
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