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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 06-22-10, 08:19 AM   #1
hobkirk
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What TIRE PRESSURE do you use on your road bike?

Clyde novice here - 240# now (5# off so far). As I learn more and more I find I know less and less. I read an article about 15% tire drop (starting with Frank Burto?), found a calculator, and get frightening news: according to the calculations, I should run -
  • 113 PSI in my front 23 mm tire
  • 173 PSI in my rear 23 mm tire (150 if it were 25 mm)
I've been riding for less than a month, but I've been ramping up my mileage - 30, 100, and 125 miles/week. I've just been pumping the tire up until I can barely depress the tire with my thumb. I carry a Turbo Morph pump and a spare tube (30-40 mile rides take me a long way from home). I've had one flat (front, sharp pebble, saw it too late). I probably should have put a 25 mm (or 28 mm?) tire on the rear, but that's hindsight.

What pressure do you run?

----------------------------------------------- Added --------------------------------------------------------

I happened to find a digression on a positing in another forum at RoadBikeReview in post # 14 (http://forums.roadbikereview.com/sho...=tire+drop+psi). I mistakenly thought this was a well known idea. The poster stated a number of ideas that seemed controversial to me about optimal pressures, rolling resistance, etc. So I posted my question about tire pressures here in the Clydesdale forum because you (and me) are living with this issue every day you ride. The "15% Drop Test" was published in Bicycle Quarterly - here's the PDF. (now I note that the link is under Vintage Bicycle Press). It includes charts of optimal PSI for different sized tires and rider weights, aiming to allow limited tire deformation.

Sorry for the confusion. And sorry for "promoting" apparently ridiculous recommended pressures. Ironically, today I carefully pumped my tires to 110 front and 120 rear before a 57 mile ride and had a flat in the rear around 40 miles.

Last edited by hobkirk; 06-22-10 at 09:06 PM. Reason: A quest for clarity
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Old 06-22-10, 08:24 AM   #2
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Look at your tire's sidewall, you'll find the max PSI listed there. Fill your tires to the max.

Each tire is different, you can't use a calculator that like and apply it to every tire. For instance, some 700 x 32's top out at 80psi, other's top out at 100 psi and so on and so forth across the tire size spectrum.

Oh, your question: I run my 700 x 28 gatorskins at 110psi front and rear.
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Old 06-22-10, 08:25 AM   #3
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I have gone to 700 x 28's. Tire pressure seems to be a personal thing.
I prefer max psi most of the time.
Lower pressure will give you a softer ride.
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Old 06-22-10, 08:32 AM   #4
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I run about 105-115 psi in both front and rear. I have either 23 or 25mm width tires on all of my road bikes. I would suggest that you not rely on the thumb test, you could have tire pressures too low. I like to use an inexpensive Zefal tire guage to check pressure at least twice a week. Butyl inner tubes will not lose as much pressure as quickly as latex but they still lose pressure. Are you using a foot pump? You mention the turbo morph, which is a fine pump but I would be afraid of wearing it out in regular use. What I mean is that I only use my Topeak Road Morph for flats when I'm out riding, but that's just me.

As far as what you read by Frank Berto - I have no idea what 15% drop means, could you elaborate further? Also the front tire pressure recommendation looks fine, but 173 psi in the rear is way off the chart. If the tire doesn't blow out (quickly) at that pressure it will on the first ride. What's gonna happen to that cold pressure when the heavy braking down a mountain heats up the rim sidewalls? Kaboom! You might get away with extreme pressure like that on an ultra high quality handmade tubular tire but even if the tire did hold air the ride quality would be greatly deteriorated.

Way to go on your weight loss, I'm back up to my "fat"weight of 265 and haven't lost any weight yet although I have ridden several hundred miles this year.
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Old 06-22-10, 09:08 AM   #5
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I run 110-120 max air pressure as indicated on sidewalls, different brand tires.
700 X 25 tires. I'm 200 lbs. 100 miles per week commute.
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Old 06-22-10, 09:21 AM   #6
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I run the 700x23 Gatorskins on my road bike at max (120 psi) and the 700x28 Forte GT2/Ks on my commuter road bike at 5 psi over max (110 psi).

As noted above, if you don't have a gauge, you have no idea what pressure you are running.
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Old 06-22-10, 09:32 AM   #7
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I have Vittoria Randonneurs - the cyclocross version. I got them in 28s, and run the back tire at about 120 to 130 and the front at 110 psi. I'm not sure what the tires themselves say for max load.
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Old 06-22-10, 09:40 AM   #8
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Quote:
Originally Posted by hobkirk View Post
Clyde novice here - 240# now (5# off so far). As I learn more and more I find I know less and less. I read an article about 15% tire drop (starting with Frank Burto?), found a calculator, and get frightening news: according to the calculations, I should run -
  • 113 PSI in my front 23 mm tire
  • 173 PSI in my rear 23 mm tire (150 if it were 25 mm)

I've been riding for less than a month, but I've been ramping up my mileage - 30, 100, and 125 miles/week. I've just been pumping the tire up until I can barely depress the tire with my thumb. I carry a Turbo Morph pump and a spare tube (30-40 mile rides take me a long way from home). I've had one flat (front, sharp pebble, saw it too late). I probably should have put a 25 mm (or 28 mm?) tire on the rear, but that's hindsight.

What pressure do you run?
Schwalbe Ultremos. 700X23. 115 front, 120 -125 rear. If you're using 23mm tyres and you can depress them significantly with your thumb, they're probably too soft unless your thumbs are much stronger than mine. To the best of my knowledge there is no tubed tyre that runs at 170 psi, so whatever your calculator is telling you, forget about trying that. Here's a link to Sheldon Brown on the subject of tyres.

Last edited by chasm54; 06-22-10 at 09:45 AM.
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Old 06-22-10, 09:44 AM   #9
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psimet's tip of the day



Tip 1 - Inflate your tires before every single ride. Know what the proper inflation pressure should be for your tires. Inflation requirements will vary by rider, bike, tires, conditions, etc.

Below you will find equations that you can use to help determine an appropriate starting point using your weight and the tire's size. Adjust from these baselines to suit needs and conditions.

Proper inflation is the easiet way to avoid flats.

Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33

Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67


Example: You are 150lbs running 28's

Pressure (psi) = (0.33*150) +33.33 = 82.83psi (rear)
Front Pressure = .9*Rear Pressure = .9*82.83psi = 74.55psi front
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Old 06-22-10, 09:48 AM   #10
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I use a floor standing pump with a built in pressure gauge - fill both 23mm tires to 110 psi and I do it each and every time I ride.

You're much more likely to flat if you run at a too-low tire pressure and the only thing I hate worse than hills & headwinds are flats out on the road.
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Old 06-22-10, 10:41 AM   #11
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Quote:
Originally Posted by hobkirk View Post
Clyde novice here - 240# now (5# off so far). As I learn more and more I find I know less and less. I read an article about 15% tire drop (starting with Frank Burto?), found a calculator, and get frightening news: according to the calculations, I should run -
  • 113 PSI in my front 23 mm tire
  • 173 PSI in my rear 23 mm tire (150 if it were 25 mm)

I've been riding for less than a month, but I've been ramping up my mileage - 30, 100, and 125 miles/week. I've just been pumping the tire up until I can barely depress the tire with my thumb. I carry a Turbo Morph pump and a spare tube (30-40 mile rides take me a long way from home). I've had one flat (front, sharp pebble, saw it too late). I probably should have put a 25 mm (or 28 mm?) tire on the rear, but that's hindsight.

What pressure do you run?
Let's see, road bike has 27x1 on it, that is equivalent to ~32mm, I run 80 in the rear and 70 on the front, with straight sided rims, I don't dare go beyond that, I'm about 220lbs. There is controversy around that 15% in the first place. The problem with using calculators is that no two tires are created equal, they can have different stiffness characteristics, different construction, and such calculators ignore these characteristics. For example tire X has a fairly stiff sidewall, tire Y has a fairly soft sidewall, even though the same width, with the same rider/bicycle, these tires will require different pressures for the same amount of drop. Another question is how much of a factor when riding is rolling resistance in the first place. I know some people will argue that they do so much better with a tire at 125PSI then they do with a tire at 124PSI, but how much is it worth?

The biggest factor isn't rolling resistance, but wind resistance, which increases exponentially as speed and wind speed increase, while rolling resistance is at best a constant, this means that as speed increases, it becomes less and less of a factor, until at some point it becomes statistically insignificant. Really, how much does it matter if that 100km ride takes you 5:46:25.8 versus you 5:46:25.7
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Old 06-22-10, 11:13 AM   #12
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I'm fortunate. The tires I use have a max inflation written on the sidewall. I inflate to that pressure (70 psi), then go riding.
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Old 06-22-10, 11:28 AM   #13
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i had a lot of issues and I'm your same weight. I stopped doing the old hand test, now i exclusively pump with a hand pump. Different brands of tires can take different pressures, i also had troubles with the bead coming off from over inflation when I was first starting out. now i use 700x28 armadillos which have a max psi rating of 100. I take them to 110 on the back and 100 even on the front, and again, I'm basically the same weight as you. Your tires are narrower so they will require more pressure. I would put them up to the max and just make sure whatever brand of tire you have that they are capable of handling the high pressure. The stock kenda kwests that came on my bike are rated 85psi max, they never should have sold the bike to a guy my size with those tires on there. had a ton of problems with them the first couple of weeks on the rough nyc roads.
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Old 06-22-10, 12:02 PM   #14
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thanks, this is really useful. I was running my 25s at 100psi - it felt weird to go higher than that - but now I see that the max psi is 125 and the calculator above says I should be well in excess of that. looks like we'll be inflating further!
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Old 06-22-10, 12:13 PM   #15
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I run my Specialized All Condition tires at 115/120psi front/rear. Those are 700x28c rated to 125psi max. I am around 235lbs...

For what its worth...Those are on a Hybrid, but I only ride it on the road
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Old 06-22-10, 12:47 PM   #16
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I have a 25mm in the rear and 23mm in the front. According to the calculations listed above, I would have ~100psi in the rear, and ~110 in the front, which makes no sense. Normally I run 110 on both, but having lost nearly 20 lbs of weight (down to 165-ish), I was wondering if I could get away with a little less pressure and not get that mushy feeling I get when I am under 110 psi.
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Old 06-22-10, 12:53 PM   #17
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110 - 120. I keep front and back equal cuz it's just easier that way
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Old 06-22-10, 01:20 PM   #18
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I run my 700x23 tires at about 120 front and 130 rear. The sidewall says 145 max. My brother's 700x23 tires are max 110, so we run his at about 100. It all depends on the tire.
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Old 06-22-10, 01:22 PM   #19
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My tires always have the recommended PSI on them, and that's the PSI I use. Keep it simple.
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Old 06-22-10, 01:39 PM   #20
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The lowest tire pressure that avoids pinch flats will provide the best ride quality, allowing the tire to absorb more bumps, rather than transferring them to the rider. They'll also be faster, have more traction in the wet, on real roads, and are less likely to damage the rim.
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Old 06-22-10, 02:14 PM   #21
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The maximum recommended pressure is just that... the highest you should go. I can't imagine anyone rides with 173 psi unless that person is racing, weighs 130 lbs and has a team car ready to fix flats.

I have moved away from 23 or 25 and now ride 28's at 100 rear and 90 front. When I rode 23's it ws at 120 - 130 psi but no higher. It gave me a smooth comfortable ride. Experiment as to what works best for you. Just remember too little air means pinch flats.
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Old 06-22-10, 05:08 PM   #22
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Originally Posted by dscheidt View Post
The lowest tire pressure that avoids pinch flats will provide the best ride quality, allowing the tire to absorb more bumps, rather than transferring them to the rider. They'll also be faster, have more traction in the wet, on real roads, and are less likely to damage the rim.
Not necessarily the case regarding faster. Generally higher pressure is going to be faster however you will be trading off speed for the other things you mentioned.
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Old 06-22-10, 06:53 PM   #23
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What it asks for on the sidewall of my Serfas Secas -- 130 psi.

But by the time I've wrangled the pump head off ...psssss ....probably about 125 psi.

The ride is still nice with the Koobi saddle and the carbon stays. This was a home-built bike from parts collected over a year+ beginning with the frame and fork. Took a while to save for the Campy Centaur/Chorus mix groupset.

The tyres were a good deal and ride and wear very well.

As for MTBs, depends 35 to 45 psi depending on the type and combo of terrain.


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Old 06-22-10, 09:28 PM   #24
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Not necessarily the case regarding faster. Generally higher pressure is going to be faster however you will be trading off speed for the other things you mentioned.
No. Faster. Less power lost in vertical motion, increased ability to put power into pavement.
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Old 06-22-10, 10:17 PM   #25
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I ride 25's and run them at 100-105 front and rear.
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