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so I weigh about 280 and i'm building a dawes sst and I plan to use 700x28s. I feel like these will be on the small side but I don't think the frame will take any bigger. will these tires hold my weight? what kind of PSI will I be looking at? until I drop some pounds i'll be mostly riding the boardwalk. thanks.
 

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This Bicycle tire pressure calculator would indicate something in the 90 psi F and 140 psi R.

So you need to make sure the tire can handle it.

Idealy you would be on larger but fit whatever is the largest the frame will take.

Obviously the wheels have to be suitable as well.
 

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If it's too late to buy a frame that will accommodate larger tires, then just use the largest tires that will fit. Bikerjulio's advice is sound. Regarding air pressure, what I would do is start at the max pressure on the sidewall and reduce pressure by 10 psi./week until you feel the tire riding soft, bottoming out, or you pinch flat. Then go back up 5-10psi. It would be fair to say you should experiment with each wheel individually; I never considered the front vs. rear pressure differences would be as extreme as bikerjulio lists but I suppose it's possible.

As you lose weight you'll have to reevaluate your tire pressure and drop it accordingly.
 

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Riding on tires at that much pressure is subjecting yourself to undue torture. Find a bike that will be comfortable and fun to ride so you can keep on riding it.
 

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Based on my personal experience you can run 90 psi in the front 100 to 110 psi in the back. When I got back into riding I was north of 3 bills and those were the pressures I rode at.

No issues with pinch flating or comfort. Get some good training tires with flat protection and you should be good.
 

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Based on my personal experience you can run 90 psi in the front 100 to 110 psi in the back. When I got back into riding I was north of 3 bills and those were the pressures I rode at.

No issues with pinch flating or comfort. Get some good training tires with flat protection and you should be good.
^^^This^^^

I've been there, too, OP. You can run 28s just fine. I ran 25s at that weight as well with no difficulties. I ran 90 or so in front and 100 in the back. The key isn't a formula so much as finding the lowest pressure that lets you roll well without pinch flatting.
 

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I'd question any rim's ability to withstand that pressure on its sidewalls. IMO, if he needs over 100psi then he needs a wider tire and one wide enough to do the job at sub-100 pressures. If his frame/fork won't take the width then it's the wrong frame-fork and no wishing & hoping will change that.
 

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I'd question any rim's ability to withstand that pressure on its sidewalls.
Back in the old days when we all ran narrow tires, and before I knew any better, I certainly ran pressures that high.

I tried to find hard info on this topic since you raised it, but didn't come up with too much, at least for alloy rims.

However, I'm sure you are right and that for OP to actually run 140 psi would be likely at or over the safe limit for any rim.
 

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I saw that in my search but wasn't sure what to make of it.

Tubular max's seemed low. I know I ran Conti sprinters a lot more than 130.

And why does rim width have anything to do with it? A wider rim is weaker? That's what it seems to be saying.
I'm not sure either. Not clear if it is rim only or rim/tire combination. The wider rims in the list are disc MTB rims with thinner extrusions and sidewalls..
I know back in the day, I run skinny tires at high pressures and never had any other issues but a sore bottom with them. Logically, a worn rim brake sidewall would be expected to be more succeptible to high tire pressures but I'm not sure where the threshold is.
 

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I'd question any rim's ability to withstand that pressure on its sidewalls. IMO, if he needs over 100psi then he needs a wider tire and one wide enough to do the job at sub-100 pressures. If his frame/fork won't take the width then it's the wrong frame-fork and no wishing & hoping will change that.
Just at the right moment, along comes @dracula with his story of the assploding rim http://forums.roadbikereview.com/wheels-tires/happens-when-you-pump-up-9-bar-mavic-aksium-wheel-353494.html
 

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Standard road tires are made for the average persons weight, you exceed that which is why the calculator is showing 140 psi for a 25 tire on the rear, not to mention very few tires will even accept that sort of pressure, however all is not lost, if you go with a touring tire like a Specialized Armadillo All Condition or the Schwalbe Marathon Plus both in a 25 they will more than handle your weight without pumping up to 140 psi. Sure the tires are a bit heavy but they will last a very long time and you won't get many if any flats. On the front you can go with a lighter tire if you want and be fine or go with the same tire on the front and eliminate again most if not all flats.
 
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