Tire size/weight a factor?

[minisub]

I wonder if the same factors that go into proper track setup also are factors when dyno-ing.
The axle will probably still wrap under load from the dyno. Incidentally, this should give me a great shot at video-ing the snubber working.
Inertia is in play when the power is applied to get the tires moving, but would the larger tires then be easier to roll once they get moving?

Just random thoughts....

I don't think you'll get a good test of the snubber. The front will be locked down, preventing weight transfer and the rear should be strapped so that the rear axle has both down and rearward force applied. I would expect that you would see much less axle wrap than you would at the track or on the street.

No real idea on the original question; my gut says the tallest/lightest combo would be best. Have no idea why, probably just some mis-remembered tidbits from HS physics some 30 or so years ago....

 

[TheBac]

Thanks Tom. Still gonna give it a try. Toyos are on...may as well dyno how I drag.

 

[othrgrl]

I have tried to dyno on my slicks and it actually didn't do well at all. Especially on a Dyno Jet our trucks have a hard time loading the motor enough to fully spool up the turbo. Short tires effectively lower your gear ratio and cause you to be able to load the truck even less. Last year back to back pulls on the same day I dynoed 10 more hp on my 20s with 305s than I did on my slicks. On the track you are also starting from a dead stop while on the dyno you typically have the tires rolling 50mph or more. FWIW I had the 20s with a new set of 305s on the truck when I dynoed what's in my sig and Dave said he saw upper 50s for boost while I've seen 62 PSI on the street.

 

[MMLMM]

Think of this...

The wider tire will lay a wider patch, creating more contact area creating more friction. We want as much traction as we can get and less friction. there has to be a ratio there somewhere that will tell us how much will hurt. Obviously loosing traction will hurt us, but can we get by with less friction, and make the wheel/tire easier to spin without sacrificing traction....? If so that will improve numbers.


also as the physics law was posted, that an object in motion will continue to stay in motion, thats true, how ever friction will be the stopping force. Weight and how tight the straps are will also play in this. More pressure between the drum and the tire contact will cause greater friction and not only that, it will cause load at the axle of the dyno drum . All the extra friction/load/force will for sure alter the numbers....but then again with too little friction, we loose traction....

 

[TheBac]

Cool! More ideas! Thanks guys!

Thing is, the shorter, thinner Toyos turned 579/1116 for an average today. Scares me to think the larger Hankooks would have done better.

 

[othrgrl]

Cool! More ideas! Thanks guys!

Thing is, the shorter, thinner Toyos turned 579/1116 for an average today. Scares me to think the larger Hankooks would have done better.

I'm not saying that taller tires will always dyno higher. How close were you to your normal boost? If you were way low I would consider taller tires to load the motor and get more boost, but other-wise stick with the lighter tire rim combo.

 

[TheBac]

Boost was a max of 31.4, and it would drop back to 27. Sothe high number is a lb low, but the drop back is exactly the same.

 

[othrgrl]

Then I wouldn't be too worried about it. When Chris was on the dyno he ony got 26 PSI instead of his normal 34. Last year when I was on it I only got 35 with the slicks and 40 with the 20s compared to the 47 I was at on the street and strip.