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Old 06-15-08, 08:01 PM   #1
rusty-c
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Heavy Rider-What Tires or Pressure

Okay, I'm a big guy.... 6'2" tall and 255 Pounds. I Recently purchased a TREK 7200 that is in great shape fits well and all of those details. I did have it fully serviced at the local shop, and all is in excellent condition. The tires that are on it are the originals and in great shape and wheels are true. My question is this I have the pressure maxed out at 80psi, which is what is recommended, and it looks like I am really stressing them. Any suggestions as to whether I can safely over inflate, or can I change out tires and if so what? Thanks in advance.....
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Old 06-15-08, 09:54 PM   #2
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keeep them at max PSI..
and come join us in clydes and athenas
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Old 06-15-08, 10:03 PM   #3
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Use 25 or 28 mm tires, and use the max pressure on the sidewall, given your size....don't mess with 23mm tires
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Old 06-16-08, 09:18 AM   #4
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The Trek 7200 is fitted with 700 x 35c tires, double check the maximum pressure. I have 700 x 38c and they are rated for 100 PSI max, but I run with 90 PSI in hot weather with no issues and I am a lil' bigger than you at 6'4" 277# currently.
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Old 06-16-08, 07:50 PM   #5
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You should worry about overstressing your wheels more then your tires.
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Old 06-16-08, 08:37 PM   #6
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You should worry about overstressing your wheels more then your tires.
Yes, but rim damage is more likely to occur if tires roll off rims for under inflation.
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Old 06-16-08, 08:56 PM   #7
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At 255 even "regular" wheels should do alright so long as you don't do anything crazy. (I'm close to that and haven't taco'd a wheel yet *knocks on wood*) Although, if you're carrying panniers or something then you do have to worry about overloading the wheels.

What is it about the tires that makes you feel like you're overstressing them? So long as they're not running so low under load that you're afraid of getting a snakebite flat, you're probably alright.

Or you could go with a wider tire like Big Apples or something.
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Old 06-17-08, 05:08 PM   #8
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Rusty-c,

If the tires on that bike are 700c-35 that should work pretty well for you. However, you may wish to find another tire of higher quality in 700c-35 or 700c-38 that can run at 100psi. For your weight you should probably be running at between 90-100psi for a 38mm wide tire. 95-100 for a 35mm wide tire.

However, I don't see a problem with running the 35mm tires at 80psi. They will compress a little more under your weight than with a lighter rider and will be a little slower but it should not cause a problem for the wheel and tire. Make sure that it is actually at 80 psi with a good gauge.
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Old 06-17-08, 05:58 PM   #9
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The compression was my issue, and I think your right on the needing a tire that will let me push the pressure up to 100psi. Do you have any suggestions on good quality tires that I should look at that fit the bill. Thanks, Rusty
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Old 06-17-08, 07:02 PM   #10
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The compression was my issue, and I think your right on the needing a tire that will let me push the pressure up to 100psi. Do you have any suggestions on good quality tires that I should look at that fit the bill. Thanks, Rusty
You will compress EVERY tire you put under your rear end, no matter what brand, size, air pressure, or material the tire is made of. You, as a human being, cannot change the laws of physics and chemistry.
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Old 06-17-08, 07:03 PM   #11
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Yes, but rim damage is more likely to occur if tires roll off rims for under inflation.
I don't think the OP is THAT ignorant.
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Old 06-17-08, 07:10 PM   #12
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I have a Trek 7300 and ride 700x28 on it and ride at 95-105 psi. Works great. Wheels are going to be a bigger issues. Take the wheels in and have them checked for tension and trueness when you hit about 400 miles and they should make them last a little longer. Insist on the having them check the tension. If you start breaking spokes, have them re-laced with some 14g spokes and your should be good.
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Old 06-17-08, 07:37 PM   #13
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Never had a doubt that physics would win, and at my size sure I wouldn't think about getting on the bike with the tires under-inflated (sucks to walk a bike back to the car).......just thought I might have maxed those tires out due to the compression of the side-walls. Bike has been serviced wheels are true and spokes are in good shape.

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Old 06-17-08, 07:48 PM   #14
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Why do you think they are stressed? A small bulge is nothing to worry
about in a 35c.
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Old 06-17-08, 09:19 PM   #15
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Why do you think they are stressed? A small bulge is nothing to worry
about in a 35c.
Looks more like about 40% of the tire has been compressed to the surface with 80psi. Wasn't thinking that was normal, and assumed it was due to myself being of the larger variety. It has been a number of years previous to now since I last rode, so I'm just getting into it, and wasn't exactly sure. Just thought that a tire that maintained more pressure might be needed. Thanks for your reply
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Old 06-17-08, 10:21 PM   #16
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The compression was my issue, and I think your right on the needing a tire that will let me push the pressure up to 100psi. Do you have any suggestions on good quality tires that I should look at that fit the bill. Thanks, Rusty
Most of the tires that will fit the bill are considered urban commuting or touring tires. One that comes to mind is the Specialized Infinity. Kind of a hybrid tire that comes in several 700c widths. I believe you can get 100psi with this tire. Touring tires are meant for carrying heavy loads so usually allow for higher pressures.
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Old 06-18-08, 06:29 AM   #17
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I don't think the OP is THAT ignorant.
No, I would never think that to be the case.

When post reply made, I was not aware the 35c types maxed at 80 PSI. Yet, I have 38c with max at 100 PSI, and 26" (MTB) max @ 60 PSI, and I do not have much tire compression and I am a lil bigger than OP.

Also, two others in family which are bigger than me with their Giant Yukons (MTB) and no issues there either.

After additional thought, I wonder how the OP is checking tire pressure? With inbuilt pump gauge or with hand gauge?

Last night had visit from Daughter and SnL, to use my pump. They learned that their pump, (foot type), gauge was not reporting correct PSI, off by 15 to 20 PSI, when compared with mine. We double checked to my pump gauge and found mine was right on.

I also noticed on their tires the tube was walking within the tire causing the valve stem to become angled, identically on his and her bikes. Another sign of under inflated tires. (expect them tonight so I can correct this issue)
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Old 06-18-08, 09:00 AM   #18
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Since it's mostly air pressure that holds you up, the tire has to flatten to the point where you have enough square inches in contact with the road. If you weigh 255 lbs, that means about 3.2 sq in with 80 psi, about 2.5 sq in with 100 psi, and about 2.1 sq in with 120 psi.
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Old 06-18-08, 10:08 AM   #19
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Since it's mostly air pressure that holds you up, the tire has to flatten to the point where you have enough square inches in contact with the road. If you weigh 255 lbs, that means about 3.2 sq in with 80 psi, about 2.5 sq in with 100 psi, and about 2.1 sq in with 120 psi.
And then after that the tire width will determine how much cushion there is between the road and the rim. A skinny tire at 80 psi will not have much clearance (will be squeezed more to make that bigger contact patch), at 100 psi will have a bit more cushion. But a fatter tire with a lower pressure can have more even clearance from road to rim. How much clearance you need depends on road conditions. More potholes/rootheaves, more bounces, might want more clearance on an absolute scale (regardless of relative pressure differences). On a nice smooth cement road, high pressure low clearance should suffice (as long as you stay on top of the pressure).

But hey I ride 26 x 2.0s and am <220# bike + me. If I let my tires down to 15 psi I still have more air cushion protecting the rims from surprise bumps than w/ 1.5s at a much higher pressure.
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Old 06-18-08, 09:16 PM   #20
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Rusty-c:

Let's put this in perspective: My tandem has 700cx25s. I'm "only" 195, but add in my son, 105, and the wheels on our bike are seeing over 50lbs more than you're are with just you and no one stresses with a tandem at "just "300 lbs. Put my little brother on, 160, and we still don't stress. Even with my neighbour, 275 lbs, we didn't stress on the tires We did stress a little on the drivetrain up one steep hill that put us in low gear...470lbs on 30-34 was putting some load into the rear chain/hub.

Yes, the tire flattens a little but I have never given it a second thought.

As DieselDan points out wheels are probably greater risk...eventually you will break spokes/crack the rim on the stock wheels. As jaxqtr points out by maintaining proper tension, you can delay this but the wheels are designed around 170 lb riders...the tandem has better rims, more spokes and a better hub.

Don
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