Cyclocross - Cross pressure

im a good old fat boy in the sport of cycling...i weigh 206...what kind of tire pressure should i be running? just a ballpark figure be awesome...im just not too sure where to start

60.3

depends on the course and depends on what type of tire and set up you have, tubular, tubeless, or clinchers

i have clinchers

i have clinchers

what tire is it and what width?

one good method is to start at the highest PSI for you tires, probably around 65psi, and then drop in 5psi increments until you pinch flat, then add 5 psi to your final number.

I normally run around 45-50 psi. Others claim to run lower, but I can't avoid pinch flats below 40 psi in 35mm tires.

run it low enough so that you bottom out like once per lap.

Remember to chalk/talc your tires and tubes to avoid pinch flats.

Anything less than 14.2 psi. That wa the tubes benefit from osmosis of atmospheric pressure, and gain pressure rather than lose it. It also gives you the added benefit of reducing the wear on rims and components...

run it low enough so that you bottom out like once per lap.

Isnt that the rule of thumb for tubulars?

hmmm i cant remember if that was tubular only. you might be right about that though.

hmmm i cant remember if that was tubular only. you might be right about that though.

I think it is, because if you bottom out a clincher you will almost surely get a pinch flat.

I run at around 35-40 PSI, which is 5-10 PSI below the recommended minimum on my Maxxis Locust CX tires (clinchers), and I haven't had a pinch yet, so I've been thinking about going lower. I weigh 185 now, but I weighed around 200 last season and I used the same pressure.

The courses I've ridden have been pretty soft. If I had any rocky sections or drops to deal with I'd probably go with a higher pressure.

I think this is something you need to test out. Expensive test though because you could go through many tubes. I am safe running 40psi with my Maxxis Raze's and I am about 150lbs.

What is this chalk/talc thing about? I have never heard of doing this.

What is this chalk/talc thing about? I have never heard of doing this.

talc your tubes so that the tube can slide more freely underneath the tire. I dont know if it cuts down on pinch flats, but it should lower your rolling resistance and makes changing tubes easier as they wont adhere to the casing.

During last weeks race I was bottoming out several times on the rear and it was quite squirley in the corners. I didn't pinch flat and that was on a clincher. I'm sure that the talc job saved me from a DNF.

talc your tubes so that the tube can slide more freely underneath the tire. I dont know if it cuts down on pinch flats, but it should lower your rolling resistance /QUOTE]

Myth.

[quote]
http://yarchive.net/bike/tire_talc.html

In the days before tubeless tires on cars, automotive tubes that were
not much thicker than the heavier bicycle tubes vulcanized into the
tire from the heat of the road and would rip when forcefully removed.
For this purpose, talcum was extensively used. Bicycles don't have
enough power not enough rolling resistance to generate vulcanizing
temperatures required to cause such adhesion so using talc has little
purpose. You'll notice that tubes contain talcum, and that is for the
purpose of preventing adhesion in the package of two absolutely clean
surfaces. You don't have that problem. In fact, adhesion of the tube
to the casing prevents rapid air escape in the event of a thorn
penetration.

Talcum, like tying and soldering, will last as much as 40 years after
the last need for it vanished. The last need for tying spokes
together at their crossings vanished with high wheeled bicycles that
threw the rider if a spoke broke and lashed about freely. Talcum in a
bicycle tire never had a reason, it has always been done in imitation
of automobiles, but even they don't use it anymore.

Jobst Brandt


Brandt designed tyres - the very successful Avocet Fasgrip was his work.

You may want to play with the psi on your tires a bit. I am 195lbs and I run my tubulars from 30-40 and my clinchers from 35-45.

[QUOTE=jonestr;9700363]talc your tubes so that the tube can slide more freely underneath the tire. I dont know if it cuts down on pinch flats, but it should lower your rolling resistance /QUOTE]

Myth.



Brandt designed tyres - the very successful Avocet Fasgrip was his work.

Whatever the method, every untalced tube I have had has formed a bond with the tire. Work in a bike shop for 10 years and you will find this phenomenon quite often.

[QUOTE=jonestr;9700363]Brandt designed tyres - the very successful Avocet Fasgrip was his work.

Bike Snob NYC (http://bikesnobnyc.blogspot.com/) readers are, of course, familiar with Brandt. :)

http://4.bp.blogspot.com/_wb8bAl1P-N0/Sq55S5gIo6I/AAAAAAAAJ3s/SEiDiLANDmg/s1600/French-Jobst-ghost.jpg

I normally ride in the 35psi range on grass/soft.. 40 or so on hard packed.. 40 will still bottom out on square faced bumps at speed.. so pick lines carefully and get weight off as needed. (i hit rim twice last week, luckily no pinch flats)

I'm 185#, 35c tires.

I weigh 130 lbs and with my new tubluars I am running 60 psi now. Rolls great but doesnt grip as well. I think i'll lower them to about 50 psi.

I think it is, because if you bottom out a clincher you will almost surely get a pinch flat.

I think it depends on the tire/tube/rim/rim tape combo.

I was running my tires (30's) at like 35 psi and I could push down on the tire and see it bottom out, but nothing happened.

It's insane how critical psi is in this game.

I think it depends on the tire/tube/rim/rim tape combo.

I was running my tires (30's) at like 35 psi and I could push down on the tire and see it bottom out, but nothing happened.

It's insane how critical psi is in this game.

Unless you are on an ultra soft course I would be extremely wary of running that low of a pressure on a clincher

Isnt that the rule of thumb for tubulars?

yeah it is. Also with tubulars you should be able to touch the rim with a lot of force pushing down on the tire with your thumbs.

[QUOTE=jonestr;9700363]talc your tubes so that the tube can slide more freely underneath the tire. I dont know if it cuts down on pinch flats, but it should lower your rolling resistance /QUOTE]

Myth.



Brandt designed tyres - the very successful Avocet Fasgrip was his work.

IMO Jobst Brandt is an arrogant prick, there I said it. He fails in his argument as to why you use talc. The talc makes the tube and tire have less friction so that as you start to deform the tire on a bump the tube can slide a bit helping to prevent a pinch flat. Tens of thousands of people use this method successfully, don't let one dude sway you.

I weigh 130 lbs and with my new tubluars I am running 60 psi now. Rolls great but doesnt grip as well. I think i'll lower them to about 50 psi.

holy crap you are running way too much pressure. at you weight you should be running 35 and under

^ yeah I run 30-35 and I weigh 205.

[QUOTE=meanwhile;9700404]

Bike Snob NYC (http://bikesnobnyc.blogspot.com/) readers are, of course, familiar with Brandt. :)

http://4.bp.blogspot.com/_wb8bAl1P-N0/Sq55S5gIo6I/AAAAAAAAJ3s/SEiDiLANDmg/s1600/French-Jobst-ghost.jpg


Do you have a conversion factor from PSI to DFU? :)

I weigh 130 lbs and with my new tubluars I am running 60 psi now. Rolls great but doesnt grip as well. I think i'll lower them to about 50 psi.

You are not really taking advantage of all that tubs offer. Get down to the 30-40's and take a practice lap, you will notice the difference.

Unless you are on an ultra soft course I would be extremely wary of running that low of a pressure on a clincher

+1 running clincher 32s at 40ish psi i pinch flatted front and rear in two days by finding the odd hard object buried in the soft stuff; tubes were talced; corners felt squirrely at that pressure; raised pressure to 60 psi with better results

I think it is, because if you bottom out a clincher you will almost surely get a pinch flat.

You don't always pinch flat if you bottom out a clincher. (At least, that has been my experience.)

You don't always pinch flat if you bottom out a clincher. (At least, that has been my experience.)

yet the only thing that will cause a pinch flat is bottoming out the tire against the rim