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Tire Pressures

Old 11-13-19, 11:30 PM
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Bigbus
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Tire Pressures

I'm curious what other road riders with 1 1/4" tires are running for pressures on 27" rims. Tube type, Mine are rated at 90PSI and I've been experimenting all over the place. Thanks in advance for any replies.
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Old 11-13-19, 11:48 PM
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1 1/4" is ~32mm and 27" is almost exactly the same diameter as 700c. So I'd run them about the same as I'd run a 700x32.
For my ~190lb road bike+rider weight, if I was on decent roads, I'd probably do something in the vicinity of 70 PSI in the rear tire, maybe 5-10 PSI less in front.

What's your bike+rider weight, what are your roads like?
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Old 11-14-19, 05:35 AM
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I weigh 230 lbs and run 80 on my 32mm 700cc tires. I've played around between 90 - 70, after many years at 90. I honestly couldn't tell much difference but flats did go down at 80 compared to 90. The science says lower is just as efficient if not more and pinch flats did not start to happen at 70. If I lose weight, I will lower it.

Earlier this year I did the Seattle to Portland ride on a rental Fuji road bike with 32mm tires. I forgot to check the air pressure on the first day, felt fine. On the second morning I checked - the tires were at 65 psi! I pumped them up to my usual 80 - psychologically, I felt faster. Looking at numbers - no difference.
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Old 11-14-19, 09:13 AM
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I have 27" x 1 1/4" tires on my Mondia and I checked them with a pair of calipers and they measured 1.390" or 35mm. This is with 80lbs. They are Michelin Pro Tech that I got at REI and they were under $30 each. They are mounted on 1 1/4" wide rims. I am glad the bike has extra clearance to clear the wide tires , even though I have to mount the rear wheel with the tire deflated. The ride is great , but they are heavy. I am running them at 75 lbs and I weigh 155.
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Old 11-14-19, 09:35 AM
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I would be careful trying to compare newer 700c wheels to old 27” wheels. They aren’t built the same externally or internally. Same goes for the associated tires. But then I’m not an advocate for under or over inflating tires. The old style 27” tires like mine are labeled “inflate to 90 PSI.” That’s how I ride them. The ride on my vintage Nishiki International is responsive, supple, and sure. No need to fix something that was never broken.
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Old 11-14-19, 11:51 AM
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Originally Posted by Sapperc View Post
I would be careful trying to compare newer 700c wheels to old 27” wheels. They aren’t built the same externally or internally. Same goes for the associated tires. But then I’m not an advocate for under or over inflating tires. The old style 27” tires like mine are labeled “inflate to 90 PSI.” That’s how I ride them. The ride on my vintage Nishiki International is responsive, supple, and sure. No need to fix something that was never broken.
Inflating tires based on volume and load is something that basically applies to all pnuematic tires. Plus there are plenty of 700c wheels and tires built to the same quality as 27"ers.


Personally, I use the Berto tire pressure app, plug in my riding weight, bike weight and tire installed width. I treat 27" tires as 700c and run that. Technically the 8mm larger diameter of a 27" rim means more volume so they could be run slightly lower, but it's good enough.
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Old 11-14-19, 01:49 PM
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27" wheels means not hooked rims. Too much pressure will blow the tire right off. 90 is plenty, 80 maybe better.
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Old 11-14-19, 02:25 PM
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I pump my road bike's rear tire to max pressure & don't sweat the schrader burp at the end. I run the front a little lower, maybe 5psi? (700c)
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Old 11-14-19, 02:53 PM
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Originally Posted by Carbonfiberboy View Post
27" wheels means not hooked rims.
Not necessarily. Hooked rims took off in the 70s, and 27" remained popular well into the 80s. Plenty of 27" wheels from that period have hooks. (And any bike that's had its rims replaced with new 27" rims since then will almost certainly have hooks.)
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Old 11-14-19, 08:01 PM
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I'm old school. I can't get used to running those low pressures. I still ride 23, and 25mm tires, in the 100 psi range, 700c. 27" slightly lower.
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Old 11-17-19, 10:39 AM
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Thank you for all the great replies. I'm old school MTBer and have been for many many years, but this road bike thing is all new to me since the donated bike (Giant Quasar from the late 80's) and I'm really beginning to enjoy the roads more. The last time I pressured up I set them at 70psi which for a MTBer is really a lot of pressure. With the higher pressures I have noticed how much I miss a front suspension fork. But you gotta love the speed. Compared to a MTB this thing flies haha!
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