Tire Question... from a noob
 

Hi Everyone

I'm new to road biking and just recently got a 2nd hand TCR 2 Composite. My first question is about the tires. Apparently the ones on my bike are "clincher" tires. What in the world does that mean? Do those still used tubes? If anyone can provide a brief explanation it would help a lot. Also, when you guys inflate the tires, do you actully check the psi or just do it by feel? If you do check the psi, I'm guessing there must be a gauge that is sold for presta valves?

Thanks for your help.
Alex

i couldn't imagine trying to 'feel' a road bike tire for optimum pressure, since it gets up to like 110 psi. i'd suggesting buying a bike pump with a pressure guage, which you should be able to find in any bike shop worth a damn

There are 2 major categories of tire: Clincher and Tubular. The clincher has a thick edge that overlaps a lip on your wheel rim. The pressure from the expanding tube makes it "clinch" to make contact. Tubular tires are glued to their rims.

The only way Ive found to check your pressure is to use a pump with a pressure gauge on it. Ive looked all over for a pressure gauge (not attached to a pump) to test tires with, and havent found one. Many people use a variety of pressure based on their riding style. I use 120, which holds the shape of the tire well on fast, sharp turns. More easy-going, less agressive style riding may warrant lower pressure for a softer ride.

Pressure guages are available for presta valves, I have one. You can also get one of those little adapters that adapt the presta to a regular tire valve, and then use a regular pressure guage that can go to 150 pounds. Pictured is the little adapter, and the pressure guage

http://img2.freeimagehosting.net/upl...c948936b4b.jpg

here are 2 presta gauges available

http://www.rei.com/product/595814.htm
http://www.amazon.com/Slime-Digital-.../dp/B000ENOPPE

I just use a floor pump with a gauge on it.

Use the chart I have linked below to determine the correct tire inflation for your weight. The different curves are based on tire width. You can find your width on the side of the tire. It should say "700X23" odds are. If it does then the "23" is your width.

http://www.bikeforums.net/attachment...1&d=1154461177

Just get a pump with a gauge built in.

You do both. Most important is the gauge method usually done before a ride with a floor pump and gauge. Then I always pinch the tires to get a feel for the tire after inflation. Once you get a sense of how it should feel, it will be your own personal "gauge" as to when it needs air. Sometimes I will skip the floor pump and start a ride without inflating.

Inner tubes will hold air only for so long. The leak comes from the valve so if you haven't been riding for a few days, chances are you will need to inflate.

Nice chart, but do you have one that goes below 185 pounds?

/cp

Yes. I have posted the equations on here somewhere. Didn't realize that it only went down to 185. I actually could probably lower my tire pressure at my current weight.

I'll re-post them when I find them.

Feel will never give you an accurate enough gauging of the pressure in the tire to be close enough to prvent flats from under inflation on rides.

The best way to prevent flats is to inflate your tires tothe correct pressure before EVERY ride (or at least once a day if you are riding multiple times a day.

Tires can lose a lot of pressure within 24 hrs. I can't rememebr where I read it, but I believe the figure is something like 10%-20% within 1 day. For most of us that equates to 12-24 psi in one day. That's a lot.

I have found this to be true with my tires over the last 20 years.

Best ways to avoid flats: Inflate before every ride. Ride at the "correct" pressure for your weight, buy quality tires, and don't run over the stuff that pops your tires....;)

also...check the tire sidewall. it will give you the max psi the tire should hold.

...but do note that's a maximum. My Vredestien's state 145 psi but there's no way I'd inflate then to that pressure. Serves no purpose and exceeds the max recommended for my rims....

You need to look harder.

http://www.pricepoint.com/images/sty...3%20TOPTG8.jpg
http://ecom1.planetbike.com/planetbike/media/1029.jpg
http://www.zefal.com/AAA/BASES/PRODU...od655image.gif

+1 if you have one down to 120 lbs :)

incorrect

This can't be stated enough IMO. This is the best advice for avoiding flats...period. I haven't had a flat since January of this year and I know it is because I am religious about checking my tire pressure before each ride and avoiding hazards in the road.

I commute regularly on a road bike with 700x23c Continental GP4000s. I get thousands of miles out of them and rarely flat. Of course, I'm prepared for it if I do. I carry a spare tube and 2 CO2 cartridges in a seatpost bag and in my shoulder pack I carry another tube and a mini-pump. On weekend rides I only have the one tube in the seatpost bag though. I also carry a multi-tool in the seatpost bag.

Why doesn't the chart go below 185lbs? I like to know what it says for 150lbs.

As I mentioned I will find the equations and post them. I made the chart for myself and my father-in-law a couple of years ago. At the time I didn't see getting below 185. My father-in-law was why the upper end of that curve was created.

The equations work the best because you just pop in the size and your weight and get a recommendation. Keep in mind these pressures are considered an appropriate starting point and should be adjusted based on preferences, style, tire performance, etc. as needed.

They do work very well as a starting point though.

The equations were derived as functions of the recommendations that Sheldon Brown placed on his site. There are so many variables with tires that I am sure he didn't want to expand on the topic.

Found it - this is an excerpt from another threadhttp://www.bikeforums.net/showthread.php?t=238071:
Formulas:

Only the intercepts change for tires between 20-28 widths. Larger widths and the slopes change. Obviously these are generalized and assumed to be linear. While not 100% correct they will give you a great place to start.

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*Front Pressure = .9*82.83psi = 74.55psi front

You could start by running 85 rear 75 front and adjust from there. For your weight I would step down to 23's which you could run at 92F - 102R. That would be nice and comfortable and have less rolling resistance than the 28's.

Hey

Thanks for all the responses. Looks like I'll invest in a decent floor pump cause if I got to do it before every ride, that’s not fun with the little hand pump.

As for the equation, with my weight I'd be looking at 90 in front and 100 in back on 23s. Compared to some of the other numbers I've been hearing 120-140 psi, that’s a big drop. So now I'm kind of wondering what to go with (of course taking into account the limits written on the actual tire).

Btw, those CO2 cartridges, how much can you actually get out of one?

Alex

That's why I took the time to figure out the equations a long time ago. Most people just pump to the written maximum on the sidewalls and let it go, but that it not needed, and actually will give you a poorer ride or tire performance. Riding at the correct pressure allows the tire to absorb the shocks of the road, while providing low rolling resistance, etc.

90 in front and 100 in the rear sounds appropriate. I would definitely start there.

As for CO2 - with a 12g unthreaded cartridge that can be bought at Walmart for around $7-$15(?) for a box of 20 will bring your tires to around 90psi....your appropriate riding pressure. It will get you home, and is much cheaper than the threaded cartridges.

How do you go about finding that out?

I use Shimano 550's as training wheels and have no idea what the recommended max is as I like a high psi.

You'd have to check with the manufacturer. Most do not seem to readily list the max pressures. I have seen them a few times. With those 550s you'll have more to worry about than sidewall failures anyway. Keep an eye out for spokes breaking - have a backup plan.

Again this goes into what pressure to run them at. As pointed out in that example you should never be running the tires at 145 anyway. Run them at the appropriate pressure for your weight. If the appropriate pressure is around 145 then step up to wider tires and/or lose some weight.

Yeah I'm not that impressed by them. Seem a bit flexy and heavy. Hubs already sound like they need an overhaul.