tire pressure?
 

I wonder, how hard should your tires be when riding? I pump up my tires about twice a week and I can always "press in" the tubes with my thumb/hand, whereas I thought it ought to be rock hard (?)
When riding, I can see at least my front tire widen a bit, where it is touching the tarmac.
Ok, I will eventually buy a pressure measuring device and maybe another high end pump.
But I now dealing with the ordinary standing upright pump and just go for it.

My tires are: Bontrager Satellite Nebula's, puncture resistant, 700x32c; 27 tpi

The indication 27 tpi refers to the required pressure; what does it mean ...tire pressure...?

You need to pump them up to the recommended pressure. Get a pump with a built in gauge, or a separate gauge, or have a bike store pump them up and then get familiar with how they feel. I don't know tpi measures. Your tires are probably rated for 60 or 80 or 100 psi.

No, TPI is "threads per inch", which refers to the tyre's casing construction. Generally, the more threads per inch, the more supple and 'fast-feeling' the tyre will be, and they usually have a lower (faster) rolling resistance

Floor pumps with good gauges aren't very expensive :thumb:

Thanx for your info - and to finish off - I will buy another floor pump with a gauge - Is it normal that I have to pump twice a week? Are these tires loosing air more or less than normal? Or better, what's your experience with this?
I ride each day for about an hour.

I'd say twice a week is about normal, however, I check mine before every ride because I'm very fussy :p

I keep on thinking that my ride will get better when the bike is tip top in order. I am probably also very fussy biker. Should have been that in all other matters... ;-)

Definitely get a gauge. Having one built into your pump is nice, I love having the one on my compressor because it'd be a pain to latch it on, pump it up a bit, take it off, check the pressure and repeat as necessary.

Even my 700x25 tires which get up to 115-120psi still have a slight bit of give to them but compared to the 65psi MTB tires on my other bike (26x1.95) they are rock hard! But, like I said, if you press hard they do have a tiny bit of squish to 'em.

Get a gauge!

:thumb:

Obviously not fussy enough, or else you would already have taken care of getting a gauge and you would know what your tire pressures are.

My tires (700x25c) typically lose 5 to 10 psi per day. I check them before each ride.

I used to inflate my tires to the max suggested pressure. I now use this chart to inflate my tires and the pressure is down considerably from the max.

In case the link doesn't work, the original msg by Psimet2001 follows:
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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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You sure? 27TPI is like extremely low. I mean for comparison, the veloflex pave's I ride are 300...

yes: http://bontrager.com/model/06996/en

That's not uncommon for gumwall tyres. And manufacturers will cheat a little on the TPI rating. Veloflex for example will count all three layers in the tread area in their TPI rating. So their actual 100tpi fabric is 200tpi on the sidewalls and 300tpi under the tread. Others will count a single layer.

On those 700x32c tyres, depending upon your weight, that formulae speedlever posted works pretty well. You'll find they'll need 75-85psi. Of course it a lot of it depends upon the rider and how smooth you are with riding over bumps, potholes and other puncture-inducing obstacles.

Let's just say that according to the formulae, my PSI should be 100 rear, 90 front. Under what conditions would it be incorrect to get the pressure up to 120 PSI??

I ask because many road riders will go for a maximum regardless of what the formulae indicates. It seems to me that the ride will be a bit harsh and there will be less rubber that meets the road. Does more pressure mean less rolling resistance? isn't less rolling resistance better than more resistance?

I am a middle aged woman and just got first bike since teen years. Its a cruiser and tire size 26X2.125. Max PSI says 40. I see charts and suggestions on here and elsewhere but am still confused. I will just be riding casually on asphalt bike path. Should I have pressure up to the MAX or what? I weigh 160 lbs. I never have any trouble understanding my car tire pressure so feel really stupid.

Thanks
Terri

You won't find the chart above to help as your tires are wider than the chart covers.
You're quite light and you are not looking for high performance, I'd suggest around 30psi would work fine. Try it, if the ride is too harsh drop the pressure a little, if the bike feels too sluggish or feels like its hitting the rims on bumps increade the pressure a little.

You will be fine with 30-35 psi in the tires. 40 or 45 psi wouldnt do any harm but you would feel all the bumps on the path

Thanks Canadian biker friends! Will follow your guidelines.

Terri