Tire pressure for an overweight rider.

Discussion in 'Cycling Equipment' started by Audiokat, Feb 16, 2016.

  1. Audiokat

    Audiokat New Member

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    I'm curios if there are any out there that have done some thinking about tire pressure as an overweight rider.

    I'm 6'1 and about 280lbs. It seems to me that 90psi to a 180lb rider is likely going to be different than it would to be for a 280lb rider. I can only assume that the lower the pressure the more road surface contact and the more work needed to turn the pedal.

    Conversely it also seeks an overweight rider is putting more stress on a highly inflated tire. I currently keep my back tire at 110psi and front at about 100psi


    Do any hefty fellers out there go with higher pressure or am I just overthinking it.
     
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  2. Audiokat

    Audiokat New Member

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    Realized there is an entire section for this stuff but have no idea how to delete my post.
     
  3. dabac

    dabac Well-Known Member

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    The first rule of tire pressure is:
    - Don't Blow The Tire
    It's loud and forceful enough to be dangerous. And a pointless waste of money.
    Now, unless degraded by damage or age, you can be quite certain that the tire will withstand the max rating embossed on the sidewall.
    And have sufficient margin that you don't really need to worry about pressure gauge calibration.
    But tire manufacturers won't tell you the self-destruct limit, so deliberate overinflation isn't such a hot idea.

    The 2nd rule of tire pressure;
    - Avoid Snakebite Flats
    Meaning tire pressure should be kept high enough so that the tube and tire can't get pinched between road and rim during regular riding conditions.

    Everything else is optional, subject to personal preferences and open to debate.
    But don't worry about rider weight stressing the tire unless you've ALSO over-inflated it.

    Tires pumped too hard for the road conditions becomes bouncy. You lose traction momentarily, comfort, and even speed, as even the smallest of bumps has to be turned into a bit of vertical motion.

    Rolling resistance isn't primarily dependent on pressure, but rather tire deformation.
    As the tire flattens at the contact patch, wave and wrinkles are formed in the material and pushed around as the wheel rolls. IT is this kneading of the actual structure that causes the rolling resistance of the tire.
    Tires with thin and supple tread patterns and sidewalls roll easier at the same pressure as a sturdy, puncture protected tire.

    If you're heavy, start with the highest recommended pressure.
    Ride and ponder. Does it feel bouncy? Is the comfort OK? Are you at risk of bottoming out?
    If you bottom out at the highest allowed pressure, you need another tire. Either a wider one, as a bigger air chamber can carry a greater weight, or one of the same width but with a higher rating.
    If you don't bottom out you're free to experiment. If it feels bouncy, drop the pressure 10% and ride some more.
    When you either begin to bottom out,or when the bike begins to feel sluggish and wobbly in turns, it's time to increase pressure again.
     
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  4. Audiokat

    Audiokat New Member

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    Thanks dabac!
     
  5. pwarbi

    pwarbi Well-Known Member

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    I'd imagine that most larger people would over inflate their tyres at least a bit, just to try and improve the comfort of the ride at least.

    Cycling isn't any different from other forms of transport in that respect. The bigger the load, the higher the tyre pressures should be.
     
  6. mpre53

    mpre53 Well-Known Member

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    We need to know what size tires you're running. For example, if you're using road tires of, say, 23 or 25 mm, at 280 lbs. 110 psi rear is too low. Rolling resistance really isn't the main issue. It's more an issue of avoiding pinch flats. Of course, every tire/tube combo has max inflation limits, and going above that isn't a great idea either.

    As an aside, I have always run my 23 mm tires at 110 psi. Last winter, aka the Winter From Hell, I gained a few extra pounds, that I never managed to lose. Probably not coincidentally, this past season, I set a new PR for flats. You still outweigh me by a good 100 lbs. You might want to take the bike to a shop, and find out what tire size is the widest one that you can run in your frame.
     
  7. dabac

    dabac Well-Known Member

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    Unless you're bottoming out, higher pressure WON'T improve comfort. Rather the opposite. The bike rides harder, bouncier.
    Most would say that LOWER pressure gives a comfier ride. Less bounce, softer. Small pebbles will simply sink into the tires as you roll over instead of kicking the bike upwards.
    Not quite. There's air chamber size/tire width to consider too. A wider tire can carry a heavier load at the same pressure.
    But with modern road bikes, there usually isn't much room to go for a wider tire.
     
  8. dhk2

    dhk2 Active Member

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    dabac has summed up the issues well. After seeing a piece online (maybe this Forum?) I've found the "15% deflection" method works well. It's the basis of this tire pressure calculator: http://www.dorkypantsr.us/bike-tire-pressure-calculator.html

    You can approximate the load on front/rear using the 40/60 estimate (for road bike), or just measure your actual loads using a bathroom scale while sitting on the bike. I did that, and came up 42% front/58% rear. I'm 200lb, on a 20lb bike (with bottle and seatpack). Now as a result, running 95 front, 115 rear on my 25mm tires. The difference in ride comfort and handling feel with the reduced front pressure is significant.

    One thing the calculator quickly reveals is that many of us big guys shouldn't be on 23mm tires, since even at max pressures they will allow too much deflection (at least on the rear tire). I'd like to try a 28mm tire on the rear of my bike, but the frame just doesn't have the clearance.....the 25 barely fits.
     
  9. pwarbi

    pwarbi Well-Known Member

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    Well if the modern day bikes can't carry wider tyres, then it's not exactly something to consider like you say it is in the first place then is it?

    It's like saying buying a car is something to consider unless you can't drive. If you can't drive in the first place then you wouldn't consider it would you?
     
  10. dabac

    dabac Well-Known Member

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    That's not a fair comparison, and I suspect that you're aware of it.
    Whether or not a wider can be fitted depends on several things that haven't been stated:
    -is "the bike" a modern, performance-oriented drop bar road bike?(the ones often limited in tire clearance)
    -what tire has it on now?
    Maybe it came with 23s and can take 25s. Maybe it's already on 25s and a 28 would rub. Or maybe it won't.
    And, often isn't always.
    Any rider wanting a wider tire while being entirely devoid of sense of judgement and observational skills is recommended to bring the bike to a shop for guidance and service.
     
  11. dhk2

    dhk2 Active Member

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    Another important consideration before buying wider tires would be rim inner width dimension. The tire makers specify a range of rim widths required for each tire to insure proper tire bead retention, ie, keeping the tire on the rim securely under both high and low pressure limits.

    Having the correct width is important enough that standard dimensions are listed for quality rims now. For example, an ETRTO 622-15mm rim (my current size) is limited to 25mm width tires by my tire manufacturer. My new wheels will be wider, ETRTO 622-17mm, which Mavic say is good for a tire size range of 25-32mm.

    The trend seems to be wider rims and tires for road bikes, and that to me is a good thing for the majority of riders and applications.
     
  12. Froze

    Froze Well-Known Member

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    This is exactly correct, if you use that calculator, use the second one by the way, and figure in your fully clothed ready to ride weight plus the bike with all the ready to ride accessories and you'll get darn close to where you need to be. If you see that the inflation required is more than the tire recommended max psi is suppose to be than you need the next size up tire...at least in the rear. I went to the calculator and you should be using a 25 on the front and a 28 on the rear, if a 28 doesn't fit than the bike shop that sold you that bike were idiots! They should have recommended a bike that can handle at least a 28 tire. The bad thing is that most road bikes sold are only designed to handle 240 pounds max which is why a 25 is the max they'll handle and which is why larger people will experience issues with wheels and even frames. That bike shop basically did this, sold you a Ford F150 pickup with a 6 cylinder engine knowing you were going to tow a 12,000 pound trailer when they should have sold you a F250 with a V8.
     
  13. dhk2

    dhk2 Active Member

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    Froze, yep, I like your auto analogy. But I didn't let the bike shop sell me a bike, it's a custom frame. When I bought it 12 years ago I was around 175 lbs. Really didn't even look at the clearance for 25mm tires....everyone was running 23's back then. I'm planning on going to 28mm rear on the new bike, as soon as the OEM rear tire wears out.

    But you know what sells bikes these days....lightweight and race-proven. A 200 lb guy (like me) comes into the shop and wants the latest 15lb CF wonderbike with 23mm tires so he can go real fast....and the LBS salesman sells it to him.

    My 125lb buddy rides steel bikes with rear racks and either 28 or 32mm tires at low pressures. Guess who beats me up hills every time? How could that be when "his bike is so much slower than mine"?
     
  14. Froze

    Froze Well-Known Member

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    Your 125 pound buddy is pushing 150 pounds less weight up that hill then you have too, even in racing the lighter racers will usually beat the heavier ones up hills, not to mention he may be in better shape than you. It's kind of like me getting on a 12 pound CF wonder bike (I don't own one by the way) and have Lance Armstrong ride my 32 pound mountain bike with fat knobby tires and he'll beat badly without breaking a sweat just on pure better conditioning than me, so bike weight and size of tires won't prevent him from beating me. The average weight of a pro racer is 151 pounds for men and about 30 pounds less for women.

    If you can't get a 28 to fit on the rear you may have to find a 25 tire meant for touring purposes like the Schwalbe Marathon Plus, or the Vittoria Randonneur, it will be a heavy tire but it will hold up better than normal light racing tires that people buy because they think they have to look like Lance Armstrong; I would buy two of those, one for front and rear. Price wise both of those tires I mentioned can be found in a 25 and come in at under $37 each and they are tough as nails and will wear a very long time.
     
  15. dhk2

    dhk2 Active Member

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    Froze, believe you have confused me with the OP. My 125 lb buddy is pushing 75 lbs less weight than me, as I currently weight 200. The point I was hitting at is that of course it's the total weight of the bike and rider that matters, not just the weight of the bike. It's dumb for most of us aging recreational riders to obsess about a few pounds on the bike......as if the bike is going to ride itself up hills!

    I think your tire suggestions are good for a 275 lb rider though. For years, weighing 180-200 lbs, I ran 23 mm GP4000s without any problems, inflated to 110 psi f/r. With normally 4K miles life on the rear tire, and almost no flats, I really don't need anything heavier or slower. My only reason for moving to 25s (and 28s in future) is more grip and comfort that comes with the lower pressures.

    Also agree tough tires are important. The new bike I got last week came with Mavic wheels and 25mm tires. First test ride, was caught out in a light rain (hey, I couldn't wait). Had a puncture on the rear which appears to have come from a tiny flint in the road (nothing was stuck in the tread though). Mavic says they have been engineered to provide optimum performance with the wheelset, but puncture-resistance seems to be lacking a bit.
     
  16. Froze

    Froze Well-Known Member

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    Yup sure did, sorry about that.

    But for the OP the tire suggestions I made stand for his weight if he can't get a 28 on that bike.
     
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