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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 05-20-11, 10:04 PM   #1
mestizoracer310
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Tire width proportioned to rider weight

Couldn't even try searching this, it's kind of "hard" to look this up..but......


I weigh 180-190#, and have been running 700x23 since I started riding newer bikes... the amount of deflection when I ride kinda scares me, so would going to 25 or 28 make any difference? I know they'd be a bit slower due to increased contact w/ the road....unless I"m wrong there too
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Old 05-20-11, 10:06 PM   #2
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Pump 'em up another 10 lbs . . .
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Old 05-20-11, 10:13 PM   #3
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How much pressure are you running?

Either get higher pressure tires for less deflection or get larger tires.

I switched from a 23 to a 28 in the back (and inflate the 28 to about 120 psi vs 145 for the 23) I honestly can't tell a difference at all.

I'm sure someone will say "If you're not getting pinch flats, there's nothing to worry about." which is probs true.
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Old 05-20-11, 10:13 PM   #4
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I actually have been....more specifically 120 in the front and 130 in the rear. This is with wire-beaded Gatorskins...
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Old 05-20-11, 10:17 PM   #5
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At your weight, I believe you'll be better off with 28's
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Old 05-20-11, 11:06 PM   #6
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At 245 lbs., I've been running 700x23 tires for 8 months now. The ride is terribly harsh and I have to be very careful to make sure my tires are inflated before every ride, but my rims have stayed straight and true. I've only ever had to worry about deflection when hitting a crack or pothole, but I know how to "get light".

However, after finally finding a set of 28s locally, I can say the difference in ride quality is night and day.
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Old 05-21-11, 01:54 AM   #7
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The actual contact patch on a 25 is probably smaller for you than a 23 would be because of your size. I read a great article about it last year some time that gave great reasons for why this worked. Something to do with your weight on a smaller tire is pushing the tire flat long ways more than the added contact patch of a wider tire which will be conpressed less because of the greater air volume.
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Old 05-22-11, 06:53 PM   #8
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Ok, so 2 votes for 28s and one for staying w/ 23s....

stryper, is that article online somewhere?
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Old 05-22-11, 07:01 PM   #9
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Quote:
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I actually have been....more specifically 120 in the front and 130 in the rear. This is with wire-beaded Gatorskins...
That's over inflating; I'm 200 and I have never gone over 120 and hardly ever get pinch flats with 23s. You need to steer around holes/cracks, learn to bunny hop, or simply get your ass off the saddle and let the legs absorb the impact. I know an older more experienced cyclist, who is also heavy, and he rides 23s at even lower pressures because he can effectively avoid pinch flats.

That said, I have been using wide tires lately (28 and 35mm) and I don't see myself going back unless the frame limits me.

tandems with 23s come to mind

Last edited by hairnet; 05-22-11 at 07:10 PM.
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Old 05-22-11, 07:17 PM   #10
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Use the following formulas to determine proper tire pressure as a function of rider weight and tire section:

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
Front Pressure = .9*Rear Pressure

For example, the OP weighs 185 lbs and uses 23mm wide tires, so Rear Tire Pressure = 0.33 x 185 + 53.33 = 114 psi. Front Tire Pressure = 0.9 x 114 = 103 psi.
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Old 05-22-11, 07:19 PM   #11
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At your weight, I believe you'll be better off with 28's
why
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Old 05-22-11, 07:28 PM   #12
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Quote:
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I actually have been....more specifically 120 in the front and 130 in the rear. This is with wire-beaded Gatorskins...
That is unnecessarily high. See my post #10.
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Old 05-22-11, 07:36 PM   #13
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Just get 28s and don't think "oh my god, I'm running big fat tires..." They feel SO much better. Just do it.
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Old 05-22-11, 07:58 PM   #14
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I went from 32c vitt rando's on my steamroller to 35c schwalbe delta cruisers and the 35's actually feel faster becuase they absorb the road abuse so much better. I am 250lbs and 6'1" by the way. On my Big Block I run 28c randos and they have been fine so far.
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Old 05-22-11, 08:05 PM   #15
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I weigh about the same as OP. 28's all day.
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Old 05-22-11, 09:24 PM   #16
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Quote:
Originally Posted by mikeetow View Post
why
I think TT said something about depending on your weight, you may have less rolling resistance with a bigger tire.. I think he said people around 160 should be on 25's so I just assumed at 185 a 28 would work good.
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Old 05-22-11, 09:56 PM   #17
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Check out yer weight distribution and use the Berto chart.

http://www.livestrong.com/article/37...tion-pressure/
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Old 05-22-11, 11:11 PM   #18
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Tejano, do I need to recalculate for a given load every time I carry stuff (other than myself)...?? When I commute to work I sometimes bring a 4# netbook, sometimes my lunch and drinks for at work...
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Old 05-23-11, 04:09 AM   #19
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Quote:
Originally Posted by TejanoTrackie View Post
Use the following formulas to determine proper tire pressure as a function of rider weight and tire section:

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
Front Pressure = .9*Rear Pressure

For example, the OP weighs 185 lbs and uses 23mm wide tires, so Rear Tire Pressure = 0.33 x 185 + 53.33 = 114 psi. Front Tire Pressure = 0.9 x 114 = 103 psi.
dude gas it right I am a clydesdale and run 23s with no problems at all
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Old 05-23-11, 06:15 AM   #20
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I'm in the 180s myself and have ridden tires ranging from 23-32. I still rock race tires (23) on my go-fast road bikes (and pinch flats are never a problem as long as I inflate my tires to proper pressure) but for casual riding/commuting I prefer something wider. I find 25s and 28s to be good compromises between speed and comfort but lately I've been riding 32s on my Bianchi San Jose and I love the comfort and ability to ride over anything (well, almost).
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Old 05-23-11, 07:07 AM   #21
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Tejano, where is that formula from?

I've been a low-pressure kind of guy for a while (most are surprised just how low), and your math is pretty close to my practice. there are all kinds of arguments for it.

OP, you're absolutely fine on 25c (@ maybe 95/105?)...but that's no reason not to run 28c, if that's what you like.
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Old 05-23-11, 07:21 AM   #22
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Tejano, where is that formula from?
I don't remember, but another member here originally posted it. I've been using it for all my non-competitive road riding on clincher tires ranging from 23mm to 37mm, and it seems to work really well. Higher pressures just make the tires ride like rocks w/o any noticeable gains in performance or flat resistance. Also, cornering traction in the rain is reduced significantly at higher pressures.
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Old 05-23-11, 09:21 AM   #23
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where is that formula from?
Psimet's Tip of the Day
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Old 06-04-11, 09:35 PM   #24
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Tejano, what about mismatched tire widths, say a 23 in front and a 25 out back or even vice versa?
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Old 06-04-11, 09:39 PM   #25
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wider in front will be more cushiony
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