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100 psi?(14 posts)

100 psi?I Love Shimano
Aug 21, 2001 7:33 PM
Hung around the LBS the other day to fix my rear flat tire (ok, I'm new at this, I don't want to break anything removing the rear). Anyway, the mechanic fills it up to 100 psi. I tell him that I usually put in 120 psi. He tells me that it's too much and would be to hard to offer any shock absorption, and that 110 is also too much. Another guy there, who used to race in the Marlboro Tour (The Philippine's version of the Tour) agreed with the mechanic. Now, I think 100 psi. is too soft...especially for our roads here with all our cracks and patches that risk a pinch flat. Am I right when I say that 100 psi. is too little? BTW, I run 700C 20mm tires.
re: 100 psi?nuke
Aug 21, 2001 7:49 PM
Well, it's all a matter of long as you DON'T pinch flat.
Lesser pressure will afford you a softer ride, albeit requiring more energy. Higher pressure will make for a more solid ride and lower rolling resistance. Whether 100 psi will pinch flat for a 20mm tire depends on your weight, speed of travel and height of bump. So you see, there are a lot of variables to it. Hopefully, it'll only cost you a tube to try it and see what works for ya!
re: 100 psi?I Love Shimano
Aug 21, 2001 9:16 PM
Guess I'll stick with 110-120 psi in the meantime. Any others have different opinions?
re: 100 psi?Bruno S
Aug 21, 2001 9:26 PM
Usually tires have limits for inflation. Check the side walls for this information.

One thing you may want to do is to get a good quality pump that has a gage. Inflating the tires properly will prevent punctures. You should also learn how to take off the rear wheel. Just shift to the highest gear (smallest cog) and to the small chainring (middle if triple). Then remove the wheel. Is very easy and some day you may have to do it on the road so its a good idea to have prior experience.

If the road are bad you may want to use 700x23 tires that are bigger and give you a more confortable ride. If you do not care about speed you can also use 700x25. 23 is the most popular size.
re: 100 psi? Tire size?mr tornado head
Aug 22, 2001 6:25 AM
Well, I went to 700 x 25's here because a lot of roads are tar and gravel chip. I run them about 90-100 psi. Have not noticed them being any slower than 700 x 23's and the lower pressure keeps me from geting the "buzz" in my hands & my butt. FWIW, I weigh about 160 lbs.

The only time I got a pinch flat is when I ran over a pothole, and 20 more lbs of air woudn't have saved me.
another vote for bigger tirescory
Aug 22, 2001 7:39 AM
You gain a lot in comfort and stability with 25s, and (at least as far as I can feel) lose nothing in speed. I've put 28s and 32s on my road bikes, 35s on the Atlantis (it goes offroad fairly often), and it works really well.
What does it say on the tire?UncleMoe
Aug 21, 2001 9:21 PM
My tires say 100-120 psi. I hit right in the middle at 110 and have had no problems.
120 psi Max.I Love Shimano
Aug 21, 2001 10:21 PM
Is says I can put in a maximum of 120 psi.

Bruno S, thanks for the suggestions. I plan to put in 23mm tires once I use up my 20mm ones. If I remove the rear tire, does it matter that I put it back with the chain falling on the smallest cog? This is what I am afraid of, I might wreck the Rear D or something!
Pinch PuncturesDougal
Aug 22, 2001 1:01 AM
There is no real chance of getting pinch punctures at 100psi. You'd have to drop to 80 or 75 to risk this, assuming your under 200lbs.

If you're a bit heavier then its worth keeping your tires as pumped as they will go.
120 psi Max.Lone Gunman
Aug 22, 2001 6:11 AM
Shift your derail to the smallest cassette gear to remove the rear wheel. Return it to the small on the re-install. Little to no chance of damaging anything, just do not force anything. Pulling the derail to fit everything into place is okay, up or down, not right to left.
I would bet that....alex the engineer
Aug 22, 2001 5:40 AM
...the seals in their air compessor are worn, and they just don't want to pump tires up the rest of the way by hand. Sometimes, even a mechanic will tell give you a line of bull (surprised), such as "Shimano doesn't make individual cogs", or "Tubasti is the best tubular cement around" (as well as other pearls of wisdom recently told to me by bike shop "mechanics"). Unless you KNOW that the mechanic is trustworthy, take EVERYTHING they tell you with a grain of salt-especially if they aren't road cyclists.
FWIW, I ride on 21mm tubulars, weigh 175, and will pump the rear to 125-135 psig. Front tire usually is 105-110 psig. On a clincher, 100 psig is probably OK if you weigh less than say, 140 lbs, but you are increasing your risk for pinch flats.
Stay with the 120# (nm)Chen2
Aug 22, 2001 6:01 AM
re: 100 psi?PEDDLFOOT
Aug 22, 2001 11:33 AM
I run 700X25 around 110 and have found no loss of speed.I used to inflate to 120 all the time but lately went down to 110 hoping to get a little better traction.The ride does seem smoother and less road buzz too.I agree that you would probably have to go less than 100 or hit a huge pothole to pinch flat.I don't see any advantage in 700x20 tires unless your racing.Go to 23's or 25's.You'll get a much better ride.
and if you're riding Axial ProsLuis
Aug 22, 2001 2:16 PM
There was the letter from Michelin in Velonews a few months ago suggesting that the APs got better wet weather traction at 100 psi. I've been riding 23 APs for years at 110 but have gone down to 100 with a perceived decrease in road vibration and no noticable effect on speed. I'm about to mount a pair of 25 APs for Cycle Oregon--it'll be interesting to see if they feel different.