Tires and Dyno Runs

[Archive]

I was just thinking about the performance difference when I change from 245/75R16 to 285/75R16. There was a noticeable drop in performance when I went to the 285's. It seems to me that this would transfer into your Dyno runs also.

Does anyone know for sure if this is correct? And how much will it change your Dyno numbers?

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[This message has been edited by BIG BOB (edited 12-18-2000). ]

 

[Archive]

Big Bob,
I was just talking about that on friday to Brad and RPM in Ca.
Thats where HAVC and My6eatsV8's do alot of dyno testing and Brad could help you answer your ?.
I run 35' tires and was wikking to go back the stock size for a dyno but it was mention that it might not make that much of a differance.
I'm willing to try this next Fri when we dyno some chips on the 00 F350 PSD of mine,(dont worry we have and 01 SLT 4x4 2500 Cummins quad cab that the wife drives)

 

[Archive]

Sorry Big Bob,
didn't give a link to get in contact with Brad it's www.dynotuning.com leave him a message he'll get back to you, he is good about that.

 

[Archive]

If I recall correctly we have seen where dyno testing in 5th works better then 4th gear. This is because in 5th the boost gets a tad higher from the greater load. More boost usually means more horsepower.

I would think that large tires would be similiar in effect. A taller tire/gear ratio should cause the engine to develop more boost/horsepower. If a lower ratio were beneficial then dyno testing in 3rd would produce the best numbers.

Once again I have to wonder if this lower gear ratio being beneficial isn't misplaced naturally aspirated gasser science. Remember, the peak torque on the Cummins engine is achieved at below 2000 rpms.

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Nowel/Performance Diesel