# Inflating tires ( newbie question )



## JerB (Jul 10, 2012)

Hi Guys

I was wondering can I use my small shop compressor to inflate my tires If I set the outlet pressure low? I have a GT aggressor and Im pretty sure that they are scharder valves ( I think there called ) and can I just use the air chuck that came with it for inflating car tires?

Any help would be great

Jeremy


----------



## Sickmak90 (May 27, 2012)

Yes


----------



## JerB (Jul 10, 2012)

Cheers Sickmak :thumbsup:

I also just checked the pressure of the tires and it says on the tire that 65psi is the max, but noticed that my local bike shop filled them only to 50psi.

Is it advisable to stay 10-15 psi under the recommended pressure?


----------



## blockphi (Mar 26, 2012)

You want to run the PSI to fit the riding/terrain. Higher for lower rolling resistance, lower for more float. 50 is probably good for most pavement riding, but drop those down to 30 or even less on dirt. You'll need to experiment with how low you can go without pinch flatting. 

I ride a lot of road during the week and roll at 45 to 50 pounds, but have had tires that I've rolled at 60+. Remember, the max is the maximum you want to use, not what you should use.


----------



## JerB (Jul 10, 2012)

Thanks for the explanation blockphi I appreciate it.

I have learned so much from guys around here in just a couple weeks, its great having a place where you can find answers to any questions I might have.


----------



## Sickmak90 (May 27, 2012)

My tires say 40-65psi and I have been running 40 all summer. You will gain traction by running lower pressure BUT you run a higher risk of getting pinch flats.


----------



## Gasp4Air (Jun 5, 2009)

Another factor is the volume (how big the cross section). A wider, taller tire can typically be run at lower pressure without pinch flatting - but they can get squirmy, especially on narrower rims. Again, experiment to see what works for your terrain, style and preferences.


----------



## coopdad (Nov 6, 2010)

JerB, being new, you might not know the term pinch flat...
If you hit a rock, the low pressure of the tire will not keep the rim from bottoming out. When it does bottom out, the tube is squeezed (pinched) between the rock and rim and is often popped.


----------



## SimpleJon (Mar 28, 2011)

Tubeless is the way to go for trail riding in my opinion, on our local single track trails I run ralphs at 25Psi, no flats all year. when I am XC racing I run them higher at about 30Psi. I run my road bike at 110psi with 23mm tires


----------



## AndrwSwitch (Nov 8, 2007)

OP - mountain bike tires usually have a minimum pressure and a maximum pressure stamped on the sidewall.

They're really both just guidelines. Often not particularly good guidelines.

The minimum pressure isn't a bad starting point. If you don't bottom out your tires going over stuff on the trail, try a little less air next time.

For me, the lowest pressure that doesn't cause pinch flats or handling problems is the best. I have an embarrassing number of bikes, so I don't mess around with changing pressure to ride different terrain - all off-road gets the same pressure, and I have a road bike for riding road.


----------



## Pedal-E (Aug 30, 2010)

The air compressor with the correct adapter is a great way to quickly inflate tires. I still find that for getting them exactly where you want them, there is no substitute for a high quality floor pump with a built in pressure gauge and bleed valve or button.


----------



## ou2mame (Apr 23, 2010)

my rims are pretty thick and i run my dirt tires at 25 or so in the trails, depends on if i'm jumping or not. if i'm doing jumps/drops i raise it a bit so i don't smack the rim on the ground. for street tires i do 60, thats the max for mine and it rides awesome with no resistance.


----------



## AndrwSwitch (Nov 8, 2007)

In response to your PM - yeah, it's fine to use your compressor. Shops do it all the time, and I think most tubeless users prefer them very much for mounting. If your compressor's pressure setting is accurate, you should also hit the right pressure very consistently.


----------



## Slozomby (Mar 22, 2012)

just be careful. some compressors will inflate a tire really fast. and thats not good for the tube.

also


----------



## JerB (Jul 10, 2012)

Thanks guys, and thanks for the pic slozomby. My tires are Schrader. I dont have to worry about filling them to fast as I dial the outlet pressure so low. I will just use my tire gauge from the car to make sure that the pressures are within specs.


----------



## brent878 (Apr 17, 2007)

JerB said:


> Thanks guys, and thanks for the pic slozomby. My tires are Schrader. I dont have to worry about filling them to fast as I dial the outlet pressure so low. I will just use my tire gauge from the car to make sure that the pressures are within specs.


check your rims also. My rims have a max psi of 37 so I don't go over that even if the tire's max is 50.


----------



## SuzukiGS750EZ (Aug 4, 2012)

You can safely run them 5 psi over or more it's just not recommended.


----------



## shane772 (Aug 21, 2010)

brent878 said:


> check your rims also. My rims have a max psi of 37 so I don't go over that even if the tire's max is 50.


Where do you check the rims max psi? I'll go look at mine but, I don't remember ever seeing it.


----------



## BigRuckus (Jun 5, 2010)

shane772 said:


> Where do you check the rims max psi? I'll go look at mine but, I don't remember ever seeing it.


Most rims do not have a psi rating, so dont worry if you cant find the markings. Ultralight alloy or carbon race rims may have a psi limitation. If your rims have a weight limit, they may also have pressure restrictions.


----------



## chaboi (Aug 1, 2012)

I had an issue with over inflation at 30lbs is that odd?


----------



## h00k247 (Feb 20, 2012)

I use my compressor to top off my tires before a ride, much easier than using a hand pump.


----------



## Sickmak90 (May 27, 2012)

I finally got a nice floor pump today with a gauge. Beats using a micro pump.


----------



## navymtbr (Feb 2, 2004)

*Example*

My .02 on inflation experimentation...

Ride: 
26" full squishy (Trek Fuel)

Tires: 
Maxxis Crossmark's 2.1 (sidewall pressure 40-65 psi)
Kenda Nevegal's UST 2.1 (sidewall pressure 30-50 psi)

Rider: 
5'7" 160lbs

I ride a 7.25 loop through my neighborhood, blacktop. I use the Crossmarks w/tubes for this. Usually run at 30 psi. All things being equal...the ride is plush and I usually complet the loop in the 29 minute range with an avg speed of 14.5mph. Last night I increased the pressure to 55 psi and completed the loop a full minute ahead in the low 28 minute range with an avg speed of 15.5mph. Less rolling resistance but a harsher ride as I felt every crack and pebble in the road.

On my trail rides I switch to tubeless Nevegals @ 20 psi. Nice complient ride. Always had trouble on one steep and loose hill. Always seemed to break traction on a root 3/4 of the way up. One ride I decided to air down prior to the climb. The Nevegals stuck like glue and I climbed that hill like a billy goat. The remaining 5 miles saw incredible traction with a somewhat "spongey" feel. When I got home, I checked the pressure and found out I was at 16 psi. I now split the difference and ride at 18ish and have no issues (no pinch flats and plenty of traction)

Moral of the story: experiment with pressures , you'll be surprised at what it will do

Steve


----------



## AndrwSwitch (Nov 8, 2007)

LOL. I use a Crossmark rear on my trail days. Which is all days that I ride the MTB.


----------



## mtngoat13 (Jul 9, 2012)

I use a small compressor right now without any problems, but I am in the market for a good floor pump


----------



## telemike (Jun 20, 2011)

*Be careful or lose tubes!*

An air compressor delivers air much much faster than any manual pump. You can rocket beyond maximum pressure in milliseconds. Even the 12 volt tire inflators that I take on back country roads for my truck tires can blast an MTB tire before you can remove the chuck. Most single stage compressors will hit 120 psi on an MTB tire before you can remove the chuck. The noise is quite impressive when the tire pops from the rim and the tube bursts.

If you have a regulator of the right type, you can inflate with a compressor. I use a portable tank around the ranch that can be filled to, say, 40 psi and won't deliver more under any circumstances - it is safe for bike tires if filled to a low enough pressure.

Buy a quality floor pump with a gauge - you can even use it for car tires. But, it takes a while to top off 4wd tires!


----------

