I'm 160 lbs geared and run 21 f, 23 rear

 

Thanks...maybe I'm being too conservative, or more likely I'm just stuck in tubed mentality.

Still, I can't help but think 12ish and 15ish are too low, even for a starting point.

 

I am 160 geared and run 20 front 23-25 rear. Obviously, a lot of factors in play, e.g. how hard your wife rips, trail surface, and tires. My wife is 120 ish and I put in 20/20 for her. That's about as low as I can go without the tires rolling. I'm trying to maximize grip - a happy wife is one that isn't falling due to lack of grip.

 

Depends on the tires.....my wife was running Maxxis Exo sidewalled tires.....20 / 20 was the max I could run without them feeling like they were made of concrete.

On the other hand, she is now riding on non TCS WTB tires....and I have to put 24/26 to make them feel like they have any air in them.

That tubeless formula was originally set up for Stan's own tires...maybe?

 

I didn't even know Stan's had tires. You could be right.

That's what she's got is non TCS WTB tires. They feel downright flat below 20 psi.

 

I've never used the formula, although I was aware of it. It works out pretty close for my wife who's 110 lbs and runs 17 in the front and 19 in the rear.

 

Yes, 13 psi front and 16 psi rear is way too low for a standard 2.0 - 2.3" MTB tire of any wheel size. The formula obviously doesn't work for sufficiently light riders, and probably not exceptionally heavy ones, either.

Does anyone read the sidewalls on your tires? Does anyone think that smart guys like bholwell who design these tires think that 13 psi is a good idea, but they put 25 psi minimum on the sidewall anyway?

Yes, I know about lawyers. But it's more than just liability. The tire needs air pressure to stay on the rim when cornered and to keep the rim off the ground when you hit rocks and land jumps.

 

Does anyone read the sidewalls on your tires? Does anyone think that smart guys like bholwell who design these tires think that 13 psi is a good idea, but they put 25 psi minimum on the sidewall anyway?

Yes, I know about lawyers. But it's more than just liability. The tire needs air pressure to stay on the rim when cornered and to keep the rim off the ground when you hit rocks and land jumps.

I see what you're saying, but the tires in question read 35-65 psi min/max. I might as well chisel her wheels out of granite if I wanted her to ride on that. It would be worthless on anything but asphalt. 35-65psi are seriously inflated numbers, that ironically, would result in a seriously overinflated tire.

 

I'm about 135lbs and have been able to run around 14 psi front (Maxxis Ikon 2.35), 18 psi rear (Maxxis Ikon 2.2) on my hardtail on fairly rooty trails with little elevation gain. On rocky trails with steep downhills I have to run ~18 psi front and 25 psi rear.

 

Fair enough, but 13 still sounds extremely low. My wife doesn't corner aggressively enough to burp a tire, but she does go right over anything that the bike and her skill will handle. Seems like a recipe for a bent rim, so I'd personally favor more like 20 psi.

 

Yeah, I agree about 13psi. My wife isn't riding hard enough to do that either. This setup fits REAL tight. I can't imagine anyone burping them unless getting awful silly, honestly.

I'll drop her down a little more bit by bit and see how it goes. I really just wanted to see if I was way outside the usefulness of the Stan's formula, and I think that is the case.

 

I don't know what the fuss is about, my wife weighs about 110lbs and consistently runs 13-15 front and 17-20 in the rear. This is on multiple wheelsets with multiple tires. Currently stans crest wheels with geax goma front and nobby nic rear. She rides very technical/ rocky terrain/ enduro races at east coast bike parks etc. No issues with tire security.

I weigh 145 and run 15-17 front and 20-25 rear, very aggressive style on technical terrain with no issues. Current set up is stans flow ex/magic mary front and spank spike race 28/ HDR II rear.

 

If I can run 25psi (tubed) @ 180 lbs. then it seems reasonable that someone half my weight could easily go under 20.

 

My wife is 110lbs. She is very fast, very aggressively and unfortunately slams into stuff a lot more then she should. She runs 18-20 front and rear with 2.0 XC tires. Rarely flats and generally doesn't destroy wheels.

I am 135lbs, also quite quick and aggressive, however I do have a pretty light touch on a bike. I run 20 in the front and 19 in the rear. I have no problems.

Try dropping the pressure in your wife's tires to the teens at least. I think she will be blown away by the difference. If I put 25psi in my tires I am miserable.

 

I've not heard of anyone running less pressure in the rear tire before. What's your reasoning behind that?

 

She got a ride in at 18F and 20R today and was very happy with it. Better traction and less bounce over the rough stuff.

 

:thumbsup:

 

^^ Whatever floats yer boat. We all have a way of gravitating to whatever works for us.

 

I'm a bit over 70 kg (160 lbs or so) and my low limits are 20 rear and 17 front, but that's with 60 mm (2.35") tires.

I don't think the numbers sound really too low for such a light person. I'd give it a shot. It's a starting point anyways.

One important thing to note is that the gauges are normally used at higher pressures and at the low end of the scale they are even less accurate than normally, so any numbers you write down are only a reference point for that particular gauge.

Also the lower you go, the more difference slight changes make. Between 16-12 psi there's only 4 psi difference but it's a 25% drop in pressure. There's a bigger difference in handling per psi than for example dropping from 40 to 36 psi, which is only a 10% drop.

 

Gauge error is an important point. I have a couple of pumps with gauges and they provide very different readings. I have a digital gauge, which I assume is quite accurate and it indicates that my 12 year old bargain pump has a gauge which is much more accurate than my high quality newer pump.

 

I don't understand this need to run low pressures. What happens in you go around a high speed turn and the tire folds over and goes flat? Down you will go and risk breaking your collar bone, wrist, elbow, and or hip and whatever else including your bike. Not to mention there is no protection for your rim against rocks. I personally wouldn't go below the low 20 psi levels.

 

Well, how much do you weigh?

 

Lower pressure until you get a rim strike with "moderate" riding and poor technique, then add 2 lbs


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Number two spot on the podium on Sunday. She said the tires felt great. Average speed was quite a bit higher than normal, and she rides very consistently. We'll keep trying to find the sweet spot based on terrain and conditions...but this thread helped us get dang close. Thanks again!

 

Can this formula be applied to cyclocross bike tires (i.e. 700 x 33)? Or are they a different animal?

 

absolutely not. the air volume in a CX tire is far smaller than a MTB tire, even a 29x1.8.

this is the reason that one rider might run 7 psi with a 26x4.0, 22 psi with 29x2.0 and 100 psi with 700x23.

 

I weight 132+/- and my hard tail with Sun Ringle Charger Comp wheels I will flirt right around 10psi for slow speed techy stuff. I only have issues when the speed picks up and I start banging the rim on roots. Most of the time I am right around 20psi. My full suspension with SRAM Roam30 wheels gave me my first burp during a endurance race, pressure was around 20. At the DH park last weekend I bumped up to right around 30psi after I started getting a couple rim strikes in the really rough stuff. For what its worth, even down near 10psi I have never folded a tire over or fully unseated a bead.

With someone as light as the OPs wife, 10 doesn't seem hard for me to believe at all...

 

I'm 155 pounds with gear and run a mix of 2.3/2.4 front tires and 2.2/2.3 in the rear. On Mavic Crossmax wheels, which have 23mm internal width. Always tubeless.
I've been riding 18F and 20R psi for ages without a problem. Any higher and I notice a loss a grip. Not huge but it's reduced.

 

Depends on the width of the tire, but 24/26 is bananas. I run 15/19 with 56mm tires and I am 145 lbs.

But 13/16 sounds good to me for her - at least if she has wide tires and rims.

 

I'm guessing that you're replying to someone on here somewhere.

 

Yeah, the original poster who said his wife was running 24/26 psi for an 88lb rider.

 

'Reply with quote' will help us understand what you're referencing.