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  1. #1
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    Tire pressure for a 400lb man on 750x35c tires

    Hello everyone, I'm a really big guy, almost 400lb, riding on 700x35c tires, matrix 750 rims. This is my bike, everything is stock.

    http://www.trekbikes.com/us/en/bikes/2008/archive/7200

    The tire says to inflate between 65-80 psi, but I found the rear wheel to be too "soft" for my weight at that psi, and have been riding at a little under 100psi.

    I'm wondering if that's dangerous, and if so what should I do?

    thanks!
    Last edited by llmercll; 06-27-11 at 10:16 PM.

  2. #2
    Certified Bike Brat Burton's Avatar
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    Hate to say it but - I think you`re outta luck!
    Skip the tire pressure - the highest load rating I`ve personally seen on any bicycle tire was 145lbs. You`re looking for something with a 200lbs load rating plus 25% as a safety margin.

    Suggest you bicycle with extreme caution. The load ratings on every component on the rest of the bicycle are probably being exceeded too.

  3. #3
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    Actually your tires are 700 X 35, not 750.

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    You'll certainly get less stupid "you're too fat to ride a bike!" answers in the clyde section, which has a number of 400 lb guys (and gals) and former 400 lbers who ride bikes, and who will probably give you an answer.

  5. #5
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    Quote Originally Posted by Al1943 View Post
    Actually your tires are 700 X 35, not 750.
    thanks, I fixed it =)

    I'm going to ask a mod to move this to the clydes forums, thanks!

  6. #6
    Senior Member Fletch521's Avatar
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    Tires are OK, wheels are going to be a problem. I bought a 2010 Trek 7200 Labor Day 2009 and started breaking spokes the first week! 32 spoke wheels are not for us bug guys. I was 365 pounds then and I have replaced the wheel with a brand new identical wheel from trek and that one started breaking spokes just as fast, had the second wheel completely rebuilt and it kept breaking spokes too. That wheel did last longer than any of the Trek supplied one though. I also had a 1982 Trek road bike that has 36 spoke wheels 27 x 1 1/8 tires that are 29 years old that I've put about 3000 miles on and have never broken a spoke.

    So, save a lot of down time and find a 36 spoke wheel that will fit your tires. There is just something about the 32 spoke pattern that allows them to flex to much.

    The response I got from the Trek dealer when dealing with the spoke issue, while they never actually said "your to fat" was "what did you really expect..."

    I expected that when I walked in of the street and said I was looking for a bike that would hold up to my weight and they selected one for me, that it would actually hold up to my weight. What they don't expect is someone our size to actually keep riding for more than a day or two. So breaking spokes every few days isn't an issue to them.

    But the tires are fine. I kept them at 85 to 90 psi, never had a problem, wore the back one out while loosing 100 pounds. Take care of the wheel issue soon, before you get discouraged, keep riding and your not going to be 400 pounds for long.

  7. #7
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    Thanks for the reply fletch =)

    Breaking spokes is a huge concern of mine, but after about a month of riding I haven't broken a single one. The front wheel came out of true (but that could be because my brother knocked it over) and I got that taken care of, and at the same time bought 5 backup spokes just in case. I can change them myself so hopfully they don't start breaking every other day =/

    Was any one wheel in particular giving you more trouble than another? was it the rear? Were they properly tensioned?

    The guy at my LBS actually told me that keeping the tires inflated high would be enough to keep my wheels from going to hell, which is partly why I'm curious about ideal psi in my case.

    I've been fine at a little under 100psi so far. I just want to be sure I'm not doing something very dangerous and will blow out one day or have some epic wreck because my tires will pop =p

    Now I'm going to knock on some wood =p

    thanks!

  8. #8
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    Quote Originally Posted by Fletch521 View Post
    Tires are OK, wheels are going to be a problem. I bought a 2010 Trek 7200 Labor Day 2009 and started breaking spokes the first week! 32 spoke wheels are not for us bug guys.
    It's more a quality issue. Skip stress relieving the spokes and they'll break. Don't put enough tension (either on all of them or just a few) in a rear wheel and non-drive side spokes will break and perhaps have the nipples unscrew. Put too much tension in some and the rim will crack.

    Stress relieving means paying laborers or buying another machine so it doesn't happen in cheap wheels. High tension slows down the machines so the production line runs slower and makes less money so it may not happen either.

    Depending on where you live, a complete wheel build is about $40 - $90.

    Spending some fraction of that before riding a machine built wheel for a tune up would be prudent.

    If you are going to have wheels built, stacking the deck in your favor with extra spokes isn't going to hurt anything.

    You definitely want a deeper rim which will be stiffer.
    Last edited by Drew Eckhardt; 06-28-11 at 01:15 AM.

  9. #9
    Senior Member Fletch521's Avatar
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    Glad you're having better luck with spokes than I did. Two wheels, three complete rebuilds, 8 or 9 replacement spokes and weeks and weeks of down time.

  10. #10
    Watching and waiting. jethro56's Avatar
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    I have a 7300 with the same rims but slightly different tires. I ride really rough roads. 2500 miles no broken spokes. I bought a Park Tool tension guage and have retensioned twice.But check it every 500 miles or so.Seems to be holding tension pretty good now. I run 60 psi front and 75 psi rear. I don't think 100 psi would be a problem for the tires but I'd keep a close eye on the rims as they will have less shock absorbing ability.

  11. #11
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    This is the best article I could find on tire inflation.

    http://www.bccclub.org/documents/Tireinflation.pdf
    Old steel makes me squeal!

  12. #12
    I am the Snail~! Peter_C's Avatar
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    Quote Originally Posted by llmercll View Post
    Hello everyone, I'm a really big guy, almost 400lb, riding on 700x35c tires, matrix 750 rims. This is my bike, everything is stock.

    http://www.trekbikes.com/us/en/bikes/2008/archive/7200

    The tire says to inflate between 65-80 psi, but I found the rear wheel to be too "soft" for my weight at that psi, and have been riding at a little under 100psi.

    I'm wondering if that's dangerous, and if so what should I do?

    thanks!
    I too started riding at a really high weight (378lbs to start), and I went to bigger tires, both for comfort, and for less risk of a blow-out. I do not care greatly about speed. So, my thoughts are to find out how wide of a tire will comfortably fit on your bike, and then I'd suggest buying a good quality tire (Marathon, Big Apple, etc) in a larger size. I was on a comfort bike, so I went to 2" Marathons.

    Knowing what I know now, I should have went to 2" Big Apples for the best comfort (again, speed is not critical to me).

    If you want/need to stay in that size tire, you can buy a higher pressure version of that size tire which could also help. I would not over-inflate period.

    Hope this helps
    Peter_C
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  13. #13
    I am the Snail~! Peter_C's Avatar
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    Quote Originally Posted by Burton View Post
    Hate to say it but - I think you`re outta luck!
    Skip the tire pressure - the highest load rating I`ve personally seen on any bicycle tire was 145lbs. You`re looking for something with a 200lbs load rating plus 25% as a safety margin.

    Suggest you bicycle with extreme caution. The load ratings on every component on the rest of the bicycle are probably being exceeded too.
    No offense, but you gave horrid info, that isn't even correct!

    http://www.schwalbetires.com/bike_ti...s/marathon_420

    Look at the 700 X 38C for a sample, it's good for 100KG which is 220lbs per tire = 440lbs total for bike and rider - and that is without even trying~! Why would you say such a thing - please check your facts before you try to discourage someone~!

    A 700X45C (if it will fit) can carry 115kg or 253lbs per tire - and these are just plain Marathons.

    The Marathon plus in a 700X45C will carry a whooping 140kg or 308lbs per tire, or 616lbs for bike and rider.

    To the OP - please take what some folks say as opinion rather than fact. What I have posted is fact - see the link please.
    Peter_C
    http://s1103.photobucket.com/albums/g475/Peter_CC/ <-- My Photos

  14. #14
    Neil_B
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    Quote Originally Posted by Burton View Post
    Hate to say it but - I think you`re outta luck!
    Skip the tire pressure - the highest load rating I`ve personally seen on any bicycle tire was 145lbs. You`re looking for something with a 200lbs load rating plus 25% as a safety margin.

    Suggest you bicycle with extreme caution. The load ratings on every component on the rest of the bicycle are probably being exceeded too.
    Job 34:35 comes to mind here. "Job hath spoken without knowledge, and his words [were] without wisdom."

  15. #15
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    Yes, your weight should not be an issue with your tires. Tandem teams are frequently above your weight and usually run even skinnier tires. They also frequently inflate them somewhat above the nominal maximum pressure stated on the tire. Going 20% over the stated maximum will usually be ok since they're supposed to have a very substantial safety margin. But I'd only do this on the rear tire since a possible blowout there is not as likely to cause a crash. Or, as stated in the post above, you could go to a wider tire if it'll fit your bike

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