Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Touring Have a dream to ride a bike across your state, across the country, or around the world? Self-contained or fully supported? Trade ideas, adventures, and more in our bicycle touring forum.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 03-19-06, 01:32 PM   #1
spokewrench55
accidental tourist
Thread Starter
 
Join Date: Oct 2004
Bikes:
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It's Gonna Blow!

I guess I fall into the school of thought that where a little's good, more's better.

I'm pumping my Continental Top Touring 700X35 tires to 100 lbs psi. It says the max is 70 lbs psi. I pump my Nokia studded tires to about 90 even though it says 65. I don't use the Nokias loaded, though.

If not, my tires look too flat when the bike is fully loaded. I've never had a problem doing this so far, and have been through several of these tires. should I be worried? I'm thinking of trying Schwalbes also.

Sheldon Brown seems to pooh pooh that max pressure rating.
spokewrench55 is offline   Reply With Quote
Old 03-19-06, 04:15 PM   #2
-=(8)=-
♋ ☮♂ ☭ ☯
 
-=(8)=-'s Avatar
 
Join Date: Feb 2005
Location: 40205 'ViLLeBiLLie
Bikes: Sngl Spd's, 70's- 80's vintage, D-tube Folder
Posts: 7,903
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
As a medium mileage commuter I lowered the airpressure on the bikes
I use to give by aching parts relief fromthe bombed out rural roads of
PA and VT where I ride and coincedentally stopped having as many flats
Go figure ?
__________________
-ADVOCACY-☜ Radical VC = Car people on bikes. Just say "NO"
-=(8)=- is offline   Reply With Quote
Old 03-19-06, 04:38 PM   #3
Machka 
In Real Life
 
Join Date: Jan 2003
Bikes:
Posts: 46,678
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 566 Post(s)
Personally, I run my tires with a lower pressure than the recommended max. My contis have a max of 120 psi, I believe, and I run them somewhere between 90 and 100 psi. It makes for a nicer ride.



Just a word of caution ... if you are going to fill you tires well over the recommended max ... wear safety goggles, and perhaps some other protective gear, while doing so. Tires can, and do, explode.
Machka is offline   Reply With Quote
Old 03-19-06, 05:02 PM   #4
ken cummings
Senior Member
 
ken cummings's Avatar
 
Join Date: Dec 2005
Location: northern California
Bikes: Bruce Gordon BLT, Cannondale parts bike, Ecodyne recumbent trike, Counterpoint Opus 2, miyata 1000
Posts: 5,601
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I read a report years ago of a man who was killed by a tire blowing out. Of course it was one of those (in biking terms) 4100x1200 mining truck tires
ken cummings is offline   Reply With Quote
Old 03-20-06, 12:07 AM   #5
spokewrench55
accidental tourist
Thread Starter
 
Join Date: Oct 2004
Bikes:
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by -=Łem in Pa=-
As a medium mileage commuter I lowered the airpressure on the bikes
I use to give by aching parts relief fromthe bombed out rural roads of
PA and VT where I ride and coincedentally stopped having as many flats
Go figure ?
Makes sense, of course. The higher pressure does stiffen the ride a bit and the higher pressure tends to puncture where lower pressure will give more to resist puncturing. My puncture rate may have gone up, I didn't track it, but my snake-bites are gone and I was having them.
Gotta love the roads these days, and the higher pressure does put me in touch with the road condition. But hit one of those ruts where it reaches the rim.....that'll rattle your fillings!
spokewrench55 is offline   Reply With Quote
Old 03-20-06, 12:38 AM   #6
spokewrench55
accidental tourist
Thread Starter
 
Join Date: Oct 2004
Bikes:
Posts: 36
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Machka
Personally, I run my tires with a lower pressure than the recommended max. My contis have a max of 120 psi, I believe, and I run them somewhere between 90 and 100 psi. It makes for a nicer ride.



Just a word of caution ... if you are going to fill you tires well over the recommended max ... wear safety goggles, and perhaps some other protective gear, while doing so. Tires can, and do, explode.
Oh no! You mean I have to start packing a face shield and kevlar apron now? 'Cause to be honest, I think the problem's origin already comes from excessive weight.
I'm a motorcycle mechanic and we sometimes have to pump up tire to double the max to seat them. It's scary sometimes but I've only had a few cheapo tires blow off small chromed rims. It's not a shrapnel issue as much as the shock of the sound.
I do appreciate your point though. In fact, I try to be cautious whenever I inflate any tire. Everyone should be.

The thing is, I've been doing this for some time now with no problems. No problems with decents either. I just thought I'd see if anyone had a problem. I would drop pressure if I could, but it appears to me the tires are under inflated then. The tires are struggling under a heavy load, but I don't believe I'm exceeding their carrying capacity. I think the bike loaded (including me) and wet comes to about 350-360 lbs.
Which tires are you running at the pressure you mentioned? I'm running Conti Grandsports on the Bianchi just at max with no problems. But I wouldn't think to use anything like that on the tourer. Maybe I need to move to different tires. I know it's heavy but the wheels seem to be holding up fine.

I liked your web page. Did you like cycling in the Cottswolds? I thought it was perfect cycling.
spokewrench55 is offline   Reply With Quote
Old 03-20-06, 01:10 AM   #7
Machka 
In Real Life
 
Join Date: Jan 2003
Bikes:
Posts: 46,678
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 566 Post(s)
Quote:
Originally Posted by spokewrench55
Which tires are you running at the pressure you mentioned? I'm running Conti Grandsports on the Bianchi just at max with no problems. But I wouldn't think to use anything like that on the tourer. Maybe I need to move to different tires. I know it's heavy but the wheels seem to be holding up fine.

I liked your web page. Did you like cycling in the Cottswolds? I thought it was perfect cycling.
I use these ones ... mainly because that's the biggest size that will fit on my bicycle!
http://www.mec.ca/Products/product_d...=1142836834690

And thanks. I believe I was only in a little part of the Cotswolds, but I enjoyed cycling everywhere in England and Wales!! I've been over there twice and both times I have had such good experiences. I want to go back!
Machka is offline   Reply With Quote
Old 03-20-06, 05:47 AM   #8
gregw
Senior Member
 
gregw's Avatar
 
Join Date: Sep 2003
Bikes:
Posts: 988
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well here is the more applicable quote from Sheldon Brown;
"Rolling Resistance
"Rolling resistance" is the mechanical friction generated as the tire rolls. As a segment of the tire tread rolls into contact with the road, it deforms from its normal curved shape into a flat shape against the road, then back to the curve as the tire rolls onward. The deformation of the rubber in this process is what causes the friction.
There are two ways to reduce this friction, each subject to trade-offs:

The thinner and softer the rubber/fabric of the tire are, the more flexible they become.
The trade-off with this is that the thinner the tire gets, the more fragile it is, and the sooner it will wear out.

The higher the air pressure, the less the tire will deflect.
The trade-off with this is that if you pump the tire up too hard, you lose the benefits of pneumatic tires: the ride becomes excessively harsh, and traction will be reduced. In addition, extremely high pressures require a stronger (heavier) fabric and stronger (heavier) rim flanges.

Rolling resistance does decrease theoretically with any increase in pressure, but with modern, high-quality tires the rolling resistance at correct inflation pressure is already so low that the infinitesimal reductions gained are more than outweighed by the trade-offs. "

I go for long term comfort on my touring bike, and not concerned with "infinitesimal reductions" in rolling resistance. My Conti's sit at 70 psi, or below if I'm too lazy to pump the tires that day.

Greg
gregw is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -6. The time now is 02:55 AM.