# Need more power? Tire pressure?



## skullman (Sep 26, 2009)

2008 750.

Just installed new (original type) Maxxis Bighorns (radial 27") on ITP 212's and changed the clutch springs to maroon primary and almond secondary. I previously had 28" Mudbugs on stock rims but wanted to try the Bighorns for more cross country riding rather than mud.

Tires are rated at max pressure of 36 psi so put 25 psi in to start. The performance was very disappointing - was really hoping to see more power output from the clutching.

Reduced the tire pressure to 15 psi after getting seriously stuck in a mud hole and it seemed to help...

So, questions: What tire pressure should I run? Why? What effect does pressure have on performance?

Do I need other power mods (stupid question)? What is the best bang for the buck?


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## phreebsd (Dec 16, 2004)

a fuller tire has less rolling resistance.


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## skullman (Sep 26, 2009)

Agreed. It appeared easier to wheelie once I removed some air...


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## phreebsd (Dec 16, 2004)

that was because of tire with low pressure will grip the ground more than a tire with high pressure... soft tires vs hard tire.. greater contact surface


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## TX4PLAY (Jan 18, 2009)

For what the Bighorns were made for I think they work better with lower pressure. I am running about 8psi in mine on the RZR and on asphalt you can feel the rolling resistance but climbing obstacles (stumps, logs, roots and ruts etc.) on the trail they cup in and grip real nice.

As far as power, they are a heavy tire but I would think that you have the right spring combo now. You may just order a couple different secondary's until you find what YOU like best.


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## Bootlegger (Dec 18, 2008)

yes...you only need about 6psi...the radials will look low but there not. 

The 27's are heavy...you would be better off with a Green seconadry.


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## FABMAN (Dec 18, 2008)

The more psi in a tire the taller the tire will be, effectively giving you a taller gear ratio affecting you take off. I have my tires at 6 to 7 psi.


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## phreebsd (Dec 16, 2004)

that's why I want the teryx bevel gears being on 31's.


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## skullman (Sep 26, 2009)

Checked my belt deflection and found it was out of spec. by 1 mm. Removed the 0.8 mm shim as it was the smallest (only two shims). According to the manual this is too much to remove to compensate for 1 mm deflection but it now gives me 21 mm deflection which is 1 mm below spec. The belt top edge is slightly above the edge of the secondary shieve and I have no clutch squeal - have not tried on decent ground to see how it is hooking up - just mud around the house but it seems more responsive and is tearing up the loose dirt pretty good.

Surprised no one has mentioned to purchase a Copperhead...


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