EpicSki › The Barking Bear Forums › Off-Season Sports & The Lighter Side › Cycling › Low tire pressures at the WC
New Posts  All Forums:Forum Nav:

Low tire pressures at the WC

post #1 of 18
Thread Starter 
2009 MSA WC, XC: Julien Absalon leads Geoff Kabush through the gnarly rocks.

my guess tubeless and 25 psi max. also love the large volume and wide tires.
post #2 of 18
Mr. Holmes,

That's absolutely amazing! How did you arrive at your deductions?

Dr. Watson

Tongue in cheek

But really, what are those conclusions based on?
post #3 of 18
Thread Starter 
Quote:
Originally Posted by MastersRacer View Post

Mr. Holmes,

That's absolutely amazing! How did you arrive at your deductions?

Dr. Watson

Tongue in cheek

But really, what are those conclusions based on?


well look at the tire.  and simple Email or PM to Adam Craig or heathers(the womens winner) husband on MTBR can be enlightening on what pros are running. It 2.35s and usually tubeless.
post #4 of 18
and 25 PSI, too? That is soft.
post #5 of 18
I'm extremely skeptical to such low numbers, even if they are suppose to come straight from riders. Why? Because I ride same tires as quite huge number of pro's are running (Schwalbe Racing Ralph/Rocket Ron) and there's no way, tires like this (or similar from other manufacturers) with paper thin sidewalls would stay on bike and not fold with so low pressure. Sure 10kg of body weight makes difference, but for me 2.5bar (around 30psi) for front tire, and around 3bar for back tire, is really lowest I can go without having feeling tire is going to get off the rim.
Next to that, both previously mentioned tires has minimum pressure set to 2.0bar (25psi is suppose to be only around 1.7bar), so I doubt they would be running them this low. But that's just my opinion, nothing more.
post #6 of 18
Quote:
Originally Posted by primoz View Post

 Because I ride same tires as quite huge number of pro's are running (Schwalbe Racing Ralph/Rocket Ron) and there's no way, tires like this (or similar from other manufacturers) with paper thin sidewalls would stay on bike and not fold with so low pressure. .
 


I'm with you on the Schwalbe's...great tread pattern and grip well, but I'm done with their paper thin sidewalls.  I was running about 30 psi in the front on my Racing Ralph's as well, and if I went to say 28psi, I'd burp air on some log hops and whatnot.(I weigh about 180lbs if that helps with perspective)

I'm now running a 2.55 Weirwolf LT tubeless in front ... really happy with it.

BWPA -- Sort of off topic, but have you ever checked out www.cyclingdirt.com?  there's a section of video interviews there with the pro's discussing their bike setups.  It's pretty cool.
Edited by Tyrone Shoelaces - 7/31/2009 at 03:39 pm GMT
post #7 of 18
Out of curiosity, do downhillers run their PSI higher?

To be frank, I ride from 40 - 50 PSI with tubes, as I hammer down the hills and I don't care to find out at what pressure I'll pinch flat or roll off the rim. One time in Crested Butte, on the 401 trail, I did just that (roll off the rim with tubeless). Since putting a tube in to finish the ride (painfully, but nothing broken) I haven't even tried tubeless again.

MR
post #8 of 18
Thread Starter 
Quote:
Originally Posted by MastersRacer View Post

Out of curiosity, do downhillers run their PSI higher?

To be frank, I ride from 40 - 50 PSI with tubes, as I hammer down the hills and I don't care to find out at what pressure I'll pinch flat or roll off the rim. One time in Crested Butte, on the 401 trail, I did just that (roll off the rim with tubeless). Since putting a tube in to finish the ride (painfully, but nothing broken) I haven't even tried tubeless again.

MR

downhillers run burlier tires with or with out tubes. I dont know what they run though for pressure

40 - 50 psi!? holy crap thats slow and bouncy, but you sound like you do what works with you. Not a clue how how a tire can roll off a a rim that easily with out some significant sideways drifting.
post #9 of 18
amongst my buddies, I'm running higer PSI than most. I am more aggressive on the DH than they are and heavier as well; I'm 200 lbs. Most buddies are 140 - 160 lbs.

50 psi is pretty firm and I'm running 2.1" wide tires.

When I rolled the bead off the rim, I was in a rough section and I believe my tire rode along the side of a rock thus grabbing along the tires edge, but without support below. It happened so fast I'm not really certain. One moment I'm riding at speed through a grove of aspen, and in a microsecond I'm out of control and flying off the side of the trail, downhill. I slid along a felled tree that wasn't very well limbed and stopped 15 yards off the trail when I took a tree on the hip. I was lucky to escape with just scrapes and bruises. My head narrowly missed a tree at about 20 mph.

For me, 50 PSI is a good compromise for climbing, rolling resistance and puncture resistance.

Please define 'slow and bouncy'.

I would say that higher pressure provides less rolling resistance and is faster. Higher pressure would also be firmer so it would probably rebound more and be bouncier; lower pressure would be softer and have more 'give' thus being smoother.

MR
post #10 of 18
After googling around, I find that my PSIs are on the high end and I'm going to experiment with lower PSIs. I need new rubber, too, so I'm going to see what wider will do for me.

I ride a Sugar 2+ and monitor the shocks with o-rings to see that I'm not bottoming out. I am always just at the maximum range, which is good. I fear that if I reduce tire pressure below 40 I'm going to roll off the rim or pinch flat.

I'll never be able to ride in the 20's. I guarantee it. I don't like the squishy sloppy feeling. I'm always looking to see if I'm flatting out when I'm that soft.

When you started the thread, BWiPA, what sort of discussion were you looking for. It was kind of a nebulous beginning.

MR
post #11 of 18
Quote:
Originally Posted by BushwackerinPA View Post




downhillers run burlier tires with or with out tubes. I dont know what they run though for pressure

I run 25 psi front 27 rear tubeless for DH

I did a little survey of the WC XC mechanics at Bromont today just for y'all. Most of the tires were in the 2.0 - 2.2ish range. Outliers were as small as 1.8 and as big as 2.3. Of course the measuring isn't very exact, some 2.3s are the same size as some 2.0s. Of all the mechanics I queried none had pressures over 29 and none were under 20. It sounded like 25 was about average.

Remember, these are little guys for the most part for me at 200 lbs, I can't go under 29 psi without feeling rim from time to time and getting a little squirm in the corners.
post #12 of 18
I usually climb with <40 psi & deflate to <30 psi on tubeless tires for the DH, cause BWPA said I could .  I have never felt like I was gonna role it off or pinch the rim.
 
JF
post #13 of 18
I experimented this weekend and found that with 30 front, 35 rear, my bike was far to squirrely on fast descents. So I added 5 lbs to the rear and all was fine.

What I am understanding is, that like in all things, there are trade offs. Weight, ability and terrain have a lot to do with what will / will not work for you. Experiment and learn.

Thanks for making me think about my riding a bit more. I'm never complacent with my skiing, why should I be with my riding?

MR
post #14 of 18
 Do you have tubes?
post #15 of 18
Sounds like tubes. I'm running 35 front/40 rear on my big fat tubed tyres (Crossmark 2.25/Race King 2.2) - I weigh around 205.
Tubeless I'd expect to get away with at least 5 psi lower.
post #16 of 18
Quote:
Originally Posted by Squawker View Post
Tubeless I'd expect to get away with at least 5 psi lower.
I didn't do any real tests, but at least with my back Schwalbe Racing Ralph (I lost my nerves trying to convert front Rocket Ron, so I gave up on that) I don't feel I can ride tubeless with lower psi then with tubes. But I guess this depends a lot on tires you are using.
post #17 of 18
Quote:
Originally Posted by primoz View Post

Quote:

But I guess this depends a lot on tires you are using.

It does. Of course we also have to remember that most of the WC racers are dwarves (I wouldn't want to use any of Irina Kalentieva's settings) and even the biggest riders are pretty light, so they can run lower pressure than the rest of us.
post #18 of 18
Yup, I'm running tubes.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Cycling
EpicSki › The Barking Bear Forums › Off-Season Sports & The Lighter Side › Cycling › Low tire pressures at the WC