# Tire Pressure for grass



## spinningsf (May 20, 2008)

Simple questio but one i do not have the answer to. What is the proper tubular tire pressure to run in grass? Do u run harded for less surface area/ or softer for better grip in the turns? Help


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## wunlap togo (Oct 1, 2004)

The actual psi depends on how big you are and how fast you are, but the basic idea is- run those suckers low. Grass is usually pretty bumpy, so the low pressure allows you to roll much more efficiently and absorb the inconsistencies of the ground. You will also get better traction in the corners with a lower pressure. Experiment. Hope this helps.


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## colinr (Nov 20, 2006)

If you need a starting point, I'm 145 and I was riding 28 psi on a pretty rooty course this weekend, on a real grassy one I would have gone lower.


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## spinningsf (May 20, 2008)

Thanks, i have starcrossed this weekend so i'll let you know how it goes, i plan to run much lower then i was so we will see how it goes


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## unclemimo (Aug 24, 2005)

For Starcrossed last year I ran at 38psi cause it was dry and there was plenty of traction, any lower and the trade off between rolling resistance and grip is not worth it. Starcrossed is fast, fast, fast and I'll trade a bit of speed for comfort there any day.

Now if it rains (not in the forecast, but it _is_ Seattle) I'd drop it down to the high 20's to low 30's as the grass gets snot slick. In which case, staying up trumps speed. Three years ago it rained in the middle of the 4's race, and half the field was sliding around like they were on ice. Made for great entertainment.


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## arrynb (Sep 15, 2008)

Interesting.

I did my first race this past weekend and it was a healthy mix of wet / some muddy grass, and woods / rooted area, and ran them at ~55 PSI. Not for any reason other than that was the lower end of the pressure rating on the tire.

What would you say the max PSI would be for a race and what would those conditions be?

thanks


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## pretender (Sep 18, 2007)

unclemimo said:


> For Starcrossed last year I ran at 38psi cause it was dry and there was plenty of traction, any lower and the trade off between rolling resistance and grip is not worth it. Starcrossed is fast, fast, fast and I'll trade a bit of speed for comfort there any day.


You have it backwards (unless the course was actually a putting green). High pressure reduces rolling resistance only on smooth pavement or wood. See result 3 on page 7:
http://www.bicicletta.co.za/Downloadable docs/Rolling Resistance Eng illustrated.pdf


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## unclemimo (Aug 24, 2005)

About 25% of Starcrossed is on asphalt, otherwise I agree, lower is better. As always there is a tradeoff. . .

BTW here is the course map for this year. Looks like more grass.


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