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tyre pressure


tinkerbell
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how do i know how hard to pump my tyres?

i have maxxis crossmarks front and back.

my front wheel veels very loose and slippery and i am wondering if i am not pumping them too hard?

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Depends on the terrain and your weight. You have to experiment to some extend because I for instance, run my rear tyre quite soft in rougher and loose terrain, but then have to be careful not to take hits on the rim, in smoother terrain, I pump them harder, but rarely over 1.8 bar, unless it's a small volume 1.9"....

 

I'm 70kg with gear and I NEVER pump a 2.1 Crossmark harder than 1.8 bar - sometimes as low as 1.6 bar...

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I assume you're a lady - so...

 

If running them tubeless, and you're in the 50 to 60kg range.:

 

1.6 bar bar front and rear.

 

If running tubes, 1.8 rear and 1.6 front.

 

Basically, stand next to your bike on the side the front brake lever is. Now lean your bike sideways about 45 deg. Pull the front brake and hold while, with both hands on the bar in a 'push-up' position, compress your fork with all your power. While doing this... look at the sidewall of the front tyre, if it folds or crinkle, the tyre is too soft. Do same with rear end.

 

What I also do, is a find a vertical step of say 3-4cm high and ride over it, starting slowly, and look and feel how mych the tyre compresses on a sharp hit... from there I decide how much harder it needs to be. You don't want it SO soft that you pinch the rim, but you want it soft enough for good grip and ride comfort... if riding on nice gravel roads, just make them 1.8. But at 2, you'll start feeling the harshness....

 

 

 

 

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I weight 84 and I normally pump my tyres (tubeless) 1.6 - 2.1. Depending on the terrain. Harder rear tyre gives you better/less rolling resistance. So sometimes I go much harder rear than the front.

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Shjo, I see a big discussion coming...

 

Tinkerbell,

The Maxxis Crossmarks are known to be "skittish" as a front wheel. Replace the front tyre with a Maxxis Monorail and you won't believe it's the same bike.

 

Now to kick off the discussion...

Tyres have a min and max tyre pressure printed on them. Maxxis Crossmark and Monorails are 35 - 60 PSI. Even the tubeless ones. So it's printed on the tyre that it wants to be inflated between 2.4BAR and 4.1BAR...

35PSI(2.4BAR) will keep the tyre ON the rim and minimize chances of pinch flats/snake bites.

 

Now, sure there is a "safety factor" worked in here which needs to cater for weight and riding style. Call me old fashioned but I don't want to take the chance of my front wheel "burping" with me bombing down a rocky decent. So I ride 35PSI on my tubeless setup. Used to ride 43PSI with tubes.

 

You're about my GF's size and I inflate her tyres to 2BAR, because she's a light weight AND she rides like the girl she is. I have her safety in mind by running her no lower than 2BAR. So FPC outjie, expect an "oeroe-wapper" next time you deflate them to 1.4 before the race <_<

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Mmmmm I must do something right cause I go down sheeet and stuff running at 1.4/1.6 and have never ever had a "burp" on any wheel . Once did manage to destroy the tyre by hitting a rock but no real danger in that ? If you gonna run at 2 and above I suggest getting perma-tubes . Those things are apparently bullet proof .

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AGREE!

 

Definately don't want my front tyre to let me down on that very rocky down hill! So will take your advise, change the front tyre to a different one and keep it pumped to 1.9.

 

I might want to ride like a guy, but want my face to stay like a girl and keep all my teeth!

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I vote for a little mountain king 2.4 at the front with about 1.8 bar and the crossmark at the back 1.6 bar.

Thats what i race and I'm 63Kg.

 

Depending on the terrain i may run them even lower.

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Mmmmm I must do something right cause I go down sheeet and stuff running at 1.4/1.6 and have never ever had a "burp" on any wheel . Once did manage to destroy the tyre by hitting a rock but no real danger in that ? If you gonna run at 2 and above I suggest getting perma-tubes . Those things are apparently bullet proof .

D-R we all know you're special like that ;)

 

Tinkerbell,

Non tubeless Maxxiss Monorails aren't very expensive. Slap one on your front wheel, keep the Crossmark on the rear. It's the best +-R250 "upgrade"/"up-trade" you'll make on your bike. Keep the Crossmark you take off the front as a spare.

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How do you guys know these pressures are accurate? I have 2 different pumps and a pressure guage, and they all read different pressures. As much as 15% variance. I now just squeeze the tyre, and make sure its a bit squisshy!!!

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