Tire Pressure - how much for optimum performance?
 

I've been reading the website and doing research about tire pressures and about tire drops, etc. Then I just finally gave up (brain just can't absorb it), which brings me to ask for help in here. :twitchy: :crash: :twitchy:

I have 700 x 35c tires on my hybrid, and I weigh 150 lbs + my load of 10-20 lbs usually placed in the rear rack. The labels tell that the pressure range is 50-75 psi, but I pump up to 70 psi on both.

So now I just wanted to know if I'm doing it right, or am I overinflating with respect to the bike load? TIA. :commute:

Here's what I use to set my tire pressure: http://www.bikequarterly.com/images/TireDrop.pdf

I'm a heavy guy (220 pounds) so I always put the maximum recommended pressure. At 150 I guess it's wathever you prefer, less pressure you put the smoother ride you get.

I would run the max in back at 75 psi and 70 in frunt. That way it would give you the best load carrying cupasaty and give you a little better grip up frunt with just a bit more comfort on the handle bars.

My .02 cents

There is a lot of rubbish printed about tire pressure. Usually people try to make up "universal tire pressure rules" with associated mathematical formulas. IMO such rules doesn't exist. I think you are doing the right thing, by using the manufacturers specification, and put the pressure in the higher range of that. The higher the pressure the lower the rolling resistance. Of course at some point a tire becomes too hard for comfort, but if you think 70 psi is OK for you, then there is no problem.

On my weekend rides with the smooth road of my choosing more is better. (85psi max in my 700x32s)
For my rough road commute I am actually faster with 65-70 in the front and 70-75 in the back.

It's an iterative process for me. I fiddle with it until I find the correct pressure which optimizes my speed with comfort.

I put 5 psi over the rated pressure in all my tires because I figure that is what you will loose unhooking the pump with a Presta valve (not a problem with Schraders.). If I wanted a smoother ride, I would drive my car.

The 15% drop method works well for me. It's not that hard to use. (I'd argue that pumping up to the max with no other thought is a worse universal rule than that. ;))

Depends on what you mean by "performance". If you're talking about minimizing rolling resistance and maximizing theoretical speed given a rider of a given strength, then higher is always better. You're limited by the rating of the tire. However, you're also limited by how much punishment the rider can stand, and therefore to some extent the types of roads you're riding on.

Here's how I do it...

I'm ~165lbs.

Commuter #1 with 32mm wide tires: Front: 60 Rear: 70

Commuter #2 with 40mm wide tires: Front: 40 Rear: 50

Road bike with 25mm wide tires: Front: 90 Rear: 100

Mountain bike: 40 or 50 depending on the terrain.

I don't think it's very scientific but it works for me.

OT.

Hey! I know where your avatar pic was taken!http://bikeforums.net/attachment.php...hmentid=311142

Ha! Yeah that was a fun ride. I've seen a few other avatar pics around here with Bike the Coast or the San Diego Century.

I'm lighter than the OP and also run 700x35. I put 60psi in the front and 70psi in the back, which I find fast yet comfortable. Max pressure for the tire is 85psi.

I put the max in mine becasue by tomorrow it will be less. I don't know about you guys but my tires never hold air for long on ANY of my bikes.

That's normal, all tires do that, even your car tires do that but as they hold a lot more air at much lower pressure it take a while to notice on a car tire. The oxygene molecules go thru the rubber slowly, that's why some will put nitrogen instead of regular air because the nitrogen molecule is bigger so the process is slower making the pressure more stable. There's a name for that but I don't remember what it is.

Here's a better explanation:http://www.popularmechanics.com/cars...stions/4302788

This. If the ride isn't too rough,the bike handles fine,and it doesn't feel like you're riding through mud,then you're doing it right.

Thanks for the input guys.. :thumb:


How does the tire drop actually work? Is it recommended to have the side threads touching the ground when loaded? I tried using different pressures in the rear tire from 60-75 psi but when I load up something in the rear rack, the back portion ride feels stiff when passing through bumps. Or probably its because I haven't ridden a bike in 8 years and that I'm not used to its feel yet.

Oh, and how often do you guys check and pump your tires?

About once every 3 to 4 weeks works for me.

I can kinda tell my tires are low by the buzzing noise from my tires and sometimes by the way it rides. Buzzing noise is dependent on the tire.

Before every ride I give them a pinch for a psi check. I would say with my 700c 32 to 34 tires I add air with the pump every four to five days.

I run 700x23 on my commuter and I check and ajust the pressure every 2 days. I didn't got anyflat since I check more often. I doesn't take long to do anyway

Depends on the tire and the pressure, really. The higher the pressure, the faster the air will leak out, and this is compounded by the fact that higher pressure tires typically are smaller so have less volume, so the same amount of air leaking out will affect them more.

On my hybrid with 32s and 40 or so PSI, I check them every couple of weeks if I remember. On the road bike with 23s and 110 PSI, it wouldn't hurt me to check every couple of days but in reality I pump them up about once a week. In that time they've usually lost about 15 PSI.

If it works for you and you're happy with it, you're doing it right.

You've read the usual material, and gotten lots of advice. There aren't any more secrets.

On the rough pavement and the cobblestones (Yes, cobblestones in Upstate, NY!) of my commute, I use less. But that's what works for me. I got there by the same route you're taking: Read the material, solicit opinion, then experiment for yourself.

I lose about 10psi a week on 700x32s inflated to 70-80psi (printed recommendation on tire is 60-80).

I keep the rear at 80 and the front at 70. Probably more than I need, but my roads aren't too bumpy. I weigh 145 and carry about 10-15lbs worth of stuff on the rear rack.