Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

Tire Inflation?

Old 08-14-09, 10:29 AM
  #1  
Senior Member
Thread Starter
 
Riverside_Guy's Avatar
 
Join Date: Aug 2009
Location: NYC-UWS
Posts: 373

Bikes: Trek 750

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Tire Inflation?

I have 700 x 35cs that are marked to hold 50-75 psi. I'm about 235, so at first I inflated to 70... but found after 1-2 rides, they were down to 50-55. Last 2 times I inflated to 63, and the same happens, 50-55.

It seems it gets into that range and tends to stay there, so I'm pretty sure I'm not having the exact same slow leak in both tubes.

Am I right to inflate to 60-65? Is it not unusual for it to deflate to roughly the same pressure? Is it "normal" to lose 10 psi after 2 rides?

Thew bike seems every so slightly more comfortable at 50 and 65. However, I have not noticed any specific issue with the speed I can do, factoring out wind conditions.

My "rides" are 3 per week, about 10-14 miles each.

Should I be topping up before every ride?

Time to get in the saddle now, we got some SUN!!
Riverside_Guy is offline  
Old 08-14-09, 10:34 AM
  #2  
Senior Member
 
frymaster's Avatar
 
Join Date: Aug 2007
Location: where the mild things roam
Posts: 1,092
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
i top up every morning and usually cram an extra 10% in. suggested psi ratings owe more to lawyers than engineers after all.
frymaster is offline  
Old 08-14-09, 11:10 AM
  #3  
Bicycle n00B
 
Join Date: Oct 2006
Location: Denver, CO
Posts: 383

Bikes: None yet

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I use the settings for my tires, but I top up every day I can. I miss a day once in a while, but do not miss two.

Bike tires are notorious for not holding pressure. Check and fill every day if you can.
eshvanu is offline  
Old 08-14-09, 03:57 PM
  #4  
Time for a change.
 
stapfam's Avatar
 
Join Date: Jan 2004
Location: 6 miles inland from the coast of Sussex, in the South East of England
Posts: 19,913

Bikes: Dale MT2000. Bianchi FS920 Kona Explosif. Giant TCR C. Boreas Ignis. Pinarello Fp Uno.

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times in 4 Posts
Loss of air in a tyre is quite normal. Time to get worried is when you lose all the air overnight and you can't find the puncture.

The tyre pressure on the wall of a tyre is only so you can keep within safe guidelines. The heavier a rider and the higher the pressure required to stop Snakebite punctures. This is where you hit a rock/kerb/pothole and the tyre is deformed so much that it compresses againt the rim- trapping the tube between the two. This gives two neat holes in the tube- just like a snakebite. That does not necessarily mean that you have to go to the Max as your potholes may not be that severe- but it is a good guide to what you should use. Going low on pressure is not always a good idea. Snakebites are one thing but "Extra Drag" caused by a low pressure can be tiring. And going too high will give you a rough ride.

And it is always a good idea to check pressures before a ride. You have found the main reason. You always seem to lose the same amount between rides but if one of the tyres loses an extra 20psi- you will know you have a "Slow" puncture that could turn into a flat tyre at any time. Better to repair it at home than on the road.

Just thought of one reason you could lose pressure after a ride. I use 700x23's at 120psi and I only lose a few lbs pressure weekly. It could be the quality of your tubes. There is a reason why not all tubes are only a few $'s each. The better quality tubes- and more expensive- are better quality.
__________________
How long was I in the army? Five foot seven.


Spike Milligan
stapfam is offline  
Old 08-14-09, 07:25 PM
  #5  
Senior Member
 
Join Date: May 2004
Location: Central Ca (taxifornia)
Posts: 196
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I weigh 240 and run Specialized tires and tubes... They are rated at 75-100 pounds.. I blow them up to 95 and then a couple weeks and a couple hundred miles later I check them .. They are usually around 80-85 pounds so I blow them back up to 95 again and go another couple weeks.. If my tires (tubes) were looseing air as fast as the OP's seem to be I would be getting a better quality tube.. He is looseing more in a few miles then I loose in a couple weeks..
Tourister is offline  
Old 08-15-09, 11:41 AM
  #6  
Senior Member
Thread Starter
 
Riverside_Guy's Avatar
 
Join Date: Aug 2009
Location: NYC-UWS
Posts: 373

Bikes: Trek 750

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Thanks for the input guys. The pattern seems to be lose 10 pounds in the first 1-2 rides, but not so much after that. Which leads me to ask what ya'll might think I SHOULD be riding at. I get this sneaky feeling they WANT me to ride around 50-55, even though I'm heavy and 50 is the supposed minimum.

Seat of the pants does tell me that having more rubber on the road is not impacting speed much at all.

Way back in my motorcycle days, I recall it was all about real rubber vs. synthetic. Rubber was what to get, part of which was durability, and part was it's ability to hold pressure longer. Is there such a thing as real rubber vs. synthetic for bike tubes?

BTW, I didn't remember correctly, they are 700 x 38cs, although I don't think it's much of a factor from the 35 I previously mentioned.
Riverside_Guy is offline  
Old 08-15-09, 03:53 PM
  #7  
Senior Member
 
Join Date: May 2004
Location: Central Ca (taxifornia)
Posts: 196
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
The way I see it the tire has very little to do with holding the air pressure... It is the tube that is blown up and holds the pressure.. I am not an expert on tubes but it has appeared to me over the years that some tubes are more porus then others.. I would simply try another vrand of tuve and check the differance... If I was loosing 10 pounds of air the first day I would be very upset
Tourister is offline  
Old 08-15-09, 06:21 PM
  #8  
Senior Member
 
Join Date: Jul 2009
Posts: 74
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm heavy too, and I find that I have to increase the pressure about every other ride. tubes are porous, not heavily, but they do leak naturally. also, remember to keep the caps on your stems (they actually create the seal). If your caps are old, the internal seal in them might not be solid.
pointatopointb is offline  
Old 08-15-09, 07:44 PM
  #9  
aka Tom Reingold
 
noglider's Avatar
 
Join Date: Jan 2009
Location: New York, NY, and High Falls, NY, USA
Posts: 40,691

Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem

Mentioned: 510 Post(s)
Tagged: 0 Thread(s)
Quoted: 7287 Post(s)
Liked 2,362 Times in 1,381 Posts
Wow, what a lot of misinformation. The cap does not form the seal. The tire does the job of holding the pressure, though the tube makes the seal, i.e. it holds the volume.

Riverside Guy, tires are tested in the factory at double the rating. I would use 100 psi on the rear tire. You don't need nearly as much on the front, since a typical bike bears 2/3 of the weight on the rear wheel. Experiment to see what pressure is the point of diminishing returns. In other words, if 100 doesn't feel quicker than 90, then stick to 90. Make sure you're not bottoming out on the rim when you hit bad potholes, though. If you are, increase your pressure.
__________________
Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog

“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author

Please email me rather than PM'ing me. Thanks.
noglider is offline  
Old 08-16-09, 06:18 AM
  #10  
aka Tom Reingold
 
noglider's Avatar
 
Join Date: Jan 2009
Location: New York, NY, and High Falls, NY, USA
Posts: 40,691

Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem

Mentioned: 510 Post(s)
Tagged: 0 Thread(s)
Quoted: 7287 Post(s)
Liked 2,362 Times in 1,381 Posts
I never use valve caps. I don't believe they serve a purpose. Perhaps cars need them because of higher speeds.
__________________
Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog

“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author

Please email me rather than PM'ing me. Thanks.
noglider is offline  
Old 08-16-09, 10:33 AM
  #11  
Senior Member
Thread Starter
 
Riverside_Guy's Avatar
 
Join Date: Aug 2009
Location: NYC-UWS
Posts: 373

Bikes: Trek 750

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Oh I know all about spoked wheels and potholes; after I bent the second front wheel rim on my motorcycle I got cast wheels! Yes I understand conservative ratings.... but 100? That would seem to give me a VERY hard ride. Not such an issue on the Central Park Loop (especially now that the whole of the East Drive is getting new paving) but I fear it would be a major teeth jarring on the Greenway, especially the northern route.

Think I'll do more experimenting once I get a good floor pump in my apartment, I've been using a pump someone left out in the basement bike room which means schlepping my bike up and down in a very small elevator with wood finish (I'm on my coop board so I can't be cavalier about scratching the nice wood finish!).

However, I'm also curious about why you suggest such an inflation... is it more to protect the rim from a heavy rider? For more performance (up to a point, putting less rubber on the road may slow one down)?

So I guess few talk about synth vs. real rubber in biking??? Or is it all moot because everything is synth these days?
Riverside_Guy is offline  
Old 08-16-09, 11:56 AM
  #12  
Conservative Hippie
 
Join Date: Mar 2005
Location: Wakulla Co. FL
Posts: 4,271
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Please forgive my asking if you are not doing this, but are you using the gauge on your pump to check the tire pressure? That works fine when airing tires up, but once the chuck is disconnected from the valve the air in the hose returns to ambient air pressure. If the chuck is then reinstalled on the valve the air from the tube flows back into the hose until the pressure is equalized, giving the vessel containing the air greater volume. Hence, the lower pressure.

However, that being said it is true that all tubes will slowly leak over time. I top my tires off about once a week. More often seems unnecessary.
CommuterRun is offline  
Old 08-16-09, 02:48 PM
  #13  
aka Tom Reingold
 
noglider's Avatar
 
Join Date: Jan 2009
Location: New York, NY, and High Falls, NY, USA
Posts: 40,691

Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem

Mentioned: 510 Post(s)
Tagged: 0 Thread(s)
Quoted: 7287 Post(s)
Liked 2,362 Times in 1,381 Posts
I ride very narrow tires at 120 psi, and I weigh only 185. Of course, wider tires need less pressure, but more pressure gives you less rolling resistance, aka better performance. The improvement that higher pressure provides is accentuated for heavier riders or cargo loads. A lightweight rider can't really feel the difference between 70 and 100 psi. Higher pressure also helps protect your wheels, both rims and spokes.

Try it. It's not as crazy as it sounds. As I said, see if you can find the point of diminishing returns. It might even be above 100 psi.

You're on the upper west side? That's where I grew up, on 96th St near Amsterdam. My mother still lives there, and my sister is on W 83 St.
__________________
Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog

“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author

Please email me rather than PM'ing me. Thanks.
noglider is offline  
Old 08-16-09, 11:01 PM
  #14  
Senior Member
 
Join Date: Sep 2007
Location: Gaseous Cloud around Uranus
Posts: 3,741
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Likes: 0
Liked 11 Times in 7 Posts
I run 700 x 32 Panaracer TG tires.I'm not even sure what they are rated at but I've always run my tires around 120-130psi.They lose about 10 psi a week or so.I ride about 200-250 miles a week.Depending on what side of a bike tour you ask,I weigh between 185-200.

Last edited by Booger1; 08-16-09 at 11:07 PM.
Booger1 is offline  
Old 08-17-09, 08:58 AM
  #15  
aka Tom Reingold
 
noglider's Avatar
 
Join Date: Jan 2009
Location: New York, NY, and High Falls, NY, USA
Posts: 40,691

Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem

Mentioned: 510 Post(s)
Tagged: 0 Thread(s)
Quoted: 7287 Post(s)
Liked 2,362 Times in 1,381 Posts
Good story, Booger1.

I have some Panaracer Pasela tires, not the Tourguards. They have got to be the best value on the market today. I think I paid $20 each, and they'll spruce up any bike.

I clumsily put some rips in the sidewall, so I put a boot on the inside. To test it, I inflated it to 150 psi, and it held just fine.

Anyway, they ride great.
__________________
Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog

“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author

Please email me rather than PM'ing me. Thanks.
noglider is offline  
Old 08-17-09, 09:02 AM
  #16  
Senior Member
Thread Starter
 
Riverside_Guy's Avatar
 
Join Date: Aug 2009
Location: NYC-UWS
Posts: 373

Bikes: Trek 750

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by noglider
I ride very narrow tires at 120 psi, and I weigh only 185. Of course, wider tires need less pressure, but more pressure gives you less rolling resistance, aka better performance. The improvement that higher pressure provides is accentuated for heavier riders or cargo loads. A lightweight rider can't really feel the difference between 70 and 100 psi. Higher pressure also helps protect your wheels, both rims and spokes.

Try it. It's not as crazy as it sounds. As I said, see if you can find the point of diminishing returns. It might even be above 100 psi.

You're on the upper west side? That's where I grew up, on 96th St near Amsterdam. My mother still lives there, and my sister is on W 83 St.
104th betwixt RSD & WEA; I'll give your suggestion a shot!
Riverside_Guy is offline  
Old 08-17-09, 09:56 AM
  #17  
Senior Member
 
BlazingPedals's Avatar
 
Join Date: Dec 2004
Location: Middle of da Mitten
Posts: 12,474

Bikes: Trek 7500, RANS V-Rex, Optima Baron, Velokraft NoCom, M-5 Carbon Highracer, Catrike Speed

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 1511 Post(s)
Liked 733 Times in 454 Posts
It's not surprising. The lower the pressure in the tire/tube, the closer it is to atmospheric pressure and the more slowly it'll lose any additional pressure. If you're losing more pressure than you're comfortable with, get thicker tubes. They'll be slower and heavier, but they'll hold pressure better.
BlazingPedals is offline  
Old 08-17-09, 11:37 AM
  #18  
Great State of Varmint
 
Panthers007's Avatar
 
Join Date: Sep 2008
Location: Dante's Third Ring
Posts: 7,476
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 15 Times in 15 Posts
I have Rivendell Ruffy Tuffy tires that Rivendell states are 700 X 27C. I keep them at 90psi as I'm about to head out on them. Most 28C tires state 90psi, some say 100psi. I find 90psi optimal for the mix of pavement and dirt up here.
Panthers007 is offline  
Old 08-17-09, 04:20 PM
  #19  
Touring Cyclist
 
Mr Jepps Se's Avatar
 
Join Date: Aug 2009
Location: England
Posts: 4

Bikes: Currently just a hybrid 2 wheel, but looking for a KMX trike.

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I hate pumping up tires. These days there are so many garages around that I just fill up at the station.
Mr Jepps Se is offline  
Old 08-18-09, 12:03 PM
  #20  
Senior Member
 
Join Date: Sep 2001
Location: Montreal
Posts: 6,521

Bikes: Peugeot Hybrid, Minelli Hybrid

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
At 235 lb you should have about 90 psi in the back and 70 psi in the front. Use slightly higher pressure if you are interested in speed or slightly lower if you want more comfort.
AndrewP is offline  
Old 08-19-09, 10:41 AM
  #21  
Senior Member
Thread Starter
 
Riverside_Guy's Avatar
 
Join Date: Aug 2009
Location: NYC-UWS
Posts: 373

Bikes: Trek 750

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Will try that combo once the weather gets more reasonable... although it may make for a harsher ride than I'd like.

BTW, I'm down to 227, which I think is a combo of riding and eating... less.

My guess is "speed" may be limited by my gearing. Can't seem to make it over 25.5 mph even on a long downhill in Central Park.
Riverside_Guy is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.