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Clydesdales/Athenas (200+ lb / 91+ kg) Looking to lose that spare tire? Ideal weight 200+? Frustrated being a large cyclist in a sport geared for the ultra-light? Learn about the bikes and parts that can take the abuse of a heavier cyclist, how to keep your body going while losing the weight, and get support from others who've been successful.

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Old 02-27-07, 08:05 AM   #1
dydst
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Is my Big Fat Ass Causing all these Flats?

Last week, I switched the tires on my Giant Cypress DX hybrid from 700c x 38 to 700c x 25 slicks. And I LOVE them. The handling is great, I go so much faster, etc. They're awesome.

Here's the problem: In the five days or so since I've had them, I've had three flats. One, I think, was due at least in part to the fact that the rubber strip around the wheel that protects the tube from the spoke nipples fell of. I think a nipple may have pierced the tube. The other two flats were what somebody at my LBS once referred to as "snakebites".

Here's the thing: I'm 6'3" and weigh 240 pounds. I never, ever had a problem with flats when I was riding with my 700c x 38 tires. I suspect that this, in large part, is the reason. The roads I commute on are somewhat crappy, with a fair number of potholes. I usually avoid them, but I inevitably hit a few on my way to work.

I would really hate to lose these tires, and switch back to my large tires. But I'm getting sick of changing all these tires and being late to work.

So do I have to switch back to my old, fat tires? Do I have any alternatives, short of losing 50 pounds? Please, any thoughts or suggestions would be greatly appreciated. Thanks!
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Old 02-27-07, 08:12 AM   #2
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Make sure your tire are properly inflated every time ou go out. The "Snakebites" are pinch flats usually caused when the tire aren't inflated enough.
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Old 02-27-07, 08:21 AM   #3
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Use Velox rim strips, not rubber. Avoid sharp rocks, and, like efrobert said, make sure you have enough pressure in the tires. I like 100-110 psi.
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Old 02-27-07, 08:33 AM   #4
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max pressure varies with tire (well to some degree with rim too but...)

Whatever your max is on your tires, ride it. You can go a little lighter in the front because most of your mass is over the back seat. (Sheldon Brown has a great article on tire pressure.)

Also, ride lighter. I harp on this but for us big guys it is the best way to have our equipment last.

Examples:
You see a pot hole too late to avoid it... you take your weight off of the seat, you put it on the balls of your feet and your hands. As you get to the front of the hole (not the back, the front) you compress and unweight your bike.

Compressing basically means you relax your ankles and your wrists so your weight "drops" a tad, then you flex them back so your body lifts up. This takes a bunch of weight off the wheels and avoids the wheel/rim slamming into the back edge of the pothole and causing a flat and/or jarring everything/and or denting/bending your rim.

After you master this you can move onto bunny hopping.

(first, the key to riding light is not being surprised by a pothole but...)
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Old 02-27-07, 09:31 AM   #5
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Your rims might be too wide for 700x25 tires.

I have a touring bike, and I went from 700x35 to 700x28s, I was told that going much narrower would not be wise on the rims I was using. There's the possibility for rim damage if the tire is not wide enough... as to the flats, I would say start by checking that your pressure is high enough.

Might be a good idea to invest a few bucks in a floor pump with a gauge so you can easily and accurately get the tires up to the appropriate pressure. The skinnier the tire, the firmer it needs to be so you can carry the weight on the smaller contact patch on which you are riding.
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Old 02-27-07, 09:40 AM   #6
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If you're 240 on 25s, yeah...you're either hitting alot of sharp rocks/curbs/potholes, or your pressure is too low. Have a gauge? Use it. The rim width is also an interesting point maybe worth looking into.

I'm 270 riding 23s and haven't gotten a flat in months (outside of nailing a pothole dead-on 3 weeks ago--snakebite on the rear, nothing on the front). I ride michelin carbons.
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Old 02-27-07, 09:49 AM   #7
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IMHO, the smallest tire you should consider is the Rivendell Ruffy Tuffy 27c.
I put several thousand miles on them before I decided I wanted something
just a bit bigger. Oh, I weigh about 10 pounds more than you.

So I am about to try a new tire design that has a real size of 28c. If the ride isn't what I want, I am going to 30c sometime in the Spring.

The Panaracer 32c tires are really more like 30c. They are surprisingly quick.
I have been meaning to start a thread to find out which ones are the longest lasting.
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Old 02-27-07, 09:50 AM   #8
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since I commute on bike everyday, I don't like getting flats. I put in some Mr Tuffy tire liners and haven't had a flat since. They will make a difference in the way that the tire feels when you ride (a bit harsher) and they add weight to the wheel/tire. But, they seem to work pretty well. It's a trade-off... I just hate flats. I'm thinking of getting a second set of wheels that I can switch out when I take the bike on longer training rides. I ride a 28mm tire... but I think I might go down to 23mm (without the liners) when I ride anything over a century.
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Old 02-27-07, 09:52 AM   #9
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Thanks guys -- sees like lack of air pressure might be my main problem. I really appreciate the responses.
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Old 02-27-07, 04:05 PM   #10
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Just out of curiosity, are you REALLY going faster, or do you just FEEL faster? Reason I ask is that I'm your size, and I've run tires from 700x20 to x41 on my Atlantis. On the very largest, at 70psi, I'm a little slower, but between 23mm and the 35s I run every day, I can't measure a difference on my 24-mile RT commute. The time depends much more on traffic, lights and what I've had for breakfast than on the tires, and the 35s are a lot more comfortable. On those at 75-80 psi, I finish a 50-mile ride feeling pretty good and go out and cut the lawn or something. When I do the same ride on skinny tires at 115, I'm whipped at the end.
As for your flat question, though, I haven't kept accurate track, but my impression is that I have at least half again as many flats on the skinny tires. Could be increased pressure on the road from the smaller contact patch, or maybe the fatties have more rubber, but there's definitely a difference.
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Old 02-27-07, 04:14 PM   #11
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they do say real high pressure will also increase flats.

By "they" here I mean Sheldon Brown but since he speaks for all of us at some level...
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Old 02-27-07, 04:20 PM   #12
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It is not your size, I'm bigger and don't have a problem running either 700X25 or 700X28.
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Old 02-27-07, 06:09 PM   #13
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Quote:
Originally Posted by Velo Dog
Just out of curiosity, are you REALLY going faster, or do you just FEEL faster?
I found that, in actuality, I am running a bit faster. I was able to increase my avg. speed by a little more than .5 mph on a 9 mile commute (it wasn't just a one day fluctuation, either). I also hit 30 m.p.h. on a hill that I'd never been able to surpass 24.5 m.p.h. on with my old, fat tires.

That, and the better handling, better ride, etc., is why I love these skinny tires so much, and don't want to switch back!

Incidentally, I think that lack of pressure may be my problem. I didn't realize how much pressue my tires are losing over the course of a day/night!

Thanks again, guys!
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Old 02-27-07, 06:26 PM   #14
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Wow, I thought I was the only person having this issue. I just switched to 700x28, but outside the 3 inch finishing nail I ran over, I have had 3 flats. One was definitely a pinch flat as it looked like the tube got caught between the rim and the tire. The other two were a mystery. I never gotten a flat riding before when I was riding my 700x38, so the first time was a painful lesson as I ended up walking home. Riding shoes are not comfy to walk a long distance in. I could not call anyone as it was about 12:45 am.

Needless to say, I now carry a CO2 airpump, patch kit and tire levers and the came in handy the very next day, but I keep on riding. I check my pressure every ride and use 120 psi and I would not go back to the 38's.
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Old 02-28-07, 12:05 AM   #15
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I've got over 600 miles on some worn 23mm tyres on front and 25mm on rear. I do pump them up to 100 psi plus before ride. I weigh 250 lbs. However I ride nicely paved country roads. I spend a lot of time looking at the road, so fail to see how I could ride into a pot hole if there was one on my route. Although there is a little 3 inch hole on one road I constantly ride over. I seem to always ride the same track on the road. I just might take some blacktop patch with me next time and patch the hole. I do have recorded in my files the following data regards tyre size for rim.

17m rim for tyre size range: 25 - 37
19m rim for size range: 28 - 44

So you may have too small a tyre for your rim; although I don't know if flatting is an outcome of that.
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Old 02-28-07, 01:43 AM   #16
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new rim tape and proper inflation helps alot I run hp 700 by 23s and I weight 215# to give you an idea one bike has 110psi on it and my winter ride has 130psi for a little better flat protection
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Old 02-28-07, 11:59 AM   #17
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Quote:
Originally Posted by Hambone
. . .

(first, the key to riding light is not being surprised by a pothole but...)
Au contraire, the first key to riding light is is being strong enough to sit light on your saddle;the second key to riding light is the learning of automatically seeing the pothole; the THIRD key is not being suprised by any pothole. . .
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Old 02-28-07, 12:13 PM   #18
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I commute three to four days a week and have all winter. At 240lbs my tires take a beating. I would personally recomend 28's and a liner. Check air pressure every time you ride and buy a pump. Another recomendation is to wipe down the tires after a ride; check for nicks or cuts before they become a problem. Ride hard and be safe.
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Old 03-08-07, 02:50 AM   #19
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Correct-size cloth rim tape, truing the wheels, and correct tire inflation is the only solution that keeps my big butt from popping tubes. However, it still happens...look at it this way, after a while you get fast at repairing tubes.
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Old 03-08-07, 08:15 AM   #20
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I started riding at 280lbs and have been fine with flats. I run 700x25 bontrager selects at 100psi.
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Old 03-08-07, 09:05 AM   #21
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Another factor to consider is that you may be on too wide a rim for 25mm tires...

Look at the chart on Sheldon's page below, you have to page down a bit to find the chart... Unless your rims are 17mm internal rim width or less, 25mm may be too narrow for the rim. And since the bike came with 38mm tires, I'll bet they are more than 17mm internal width, since 38's are at the upper edge of the proper range for a 17mm rim width.

http://www.sheldonbrown.com/tire_sizing.html

Good luck on finding a solution, whatever it is.
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