before and after performance for new tires, results

konarider94 · 11-18-2009, 09:32 PM

I got some new tires and did a before and after with my dynolicious app. Just thought id share the results. First run was stock with 245/65-17 and the second run was with 245/75-17 goodyear silent armors

xa310165 · 11-19-2009, 05:45 PM

Hey can you get some pics of the tires on your jeep? I had the silent armors on my truck and they looked tight. They were 31s though...I miss the bigger tires.

konarider94 · 11-19-2009, 08:23 PM

yea i plan on it but the weather has been junky. ill try tomorrow

cant believe no one has commented on the differences in speed. i know thats not the purpose of larger tires but its interesting to know anyway. instead of subjective opinions.

stephendurda · 11-19-2009, 08:40 PM

Not too surprised that larger tires would slow you down, since they're heavier and your engine has to work harder to turn the larger diameter.
I think people may be a bit skeptical about the efficacy of the accelerometer/GPS combo in your iphone for determining HP and precise Gs.

konarider94 · 11-19-2009, 09:07 PM

Quote:

Originally Posted by stephendurda

Not too surprised that larger tires would slow you down, since they're heavier and your engine has to work harder to turn the larger diameter.
I think people may be a bit skeptical about the efficacy of the accelerometer/GPS combo in your iphone for determining HP and precise Gs.

i can agree with that, and i knew it would slow me down its just nice to see how much. the absolute numbers may be off a little but they seem to be in the ball park. as a relative tool for before and after it should be pretty reliable.

i think its a neat technology. integrate acceleration to get velocity and integrate again to get position. i wish i could verify it at a drag strip but there are none near me. it does not run off of gps. accelerometer and time only.

stephendurda · 11-19-2009, 09:14 PM

Since my posting, I've done a bit of reading of reviews on Dynolicious and it's quite impressive to a lot of people. I agree that since you're using it to compare the same vehicle under two circumstances your results should be meaningful. Did you change the weight of your Jeep in the app after you added the new tires? If not it seems like the results might be skewed a bit.

konarider94 · 11-19-2009, 09:24 PM

Quote:

Originally Posted by stephendurda

Since my posting, I've done a bit of reading of reviews on Dynolicious and it's quite impressive to a lot of people. I agree that since you're using it to compare the same vehicle under two circumstances your results should be meaningful. Did you change the weight of your Jeep in the app after you added the new tires? If not it seems like the results might be skewed a bit.

i didnt change the weight. the weight is only used to estimate hp in my understanding. if you know the vehicle weight and the acceleration you can get the force. then that is used to get work then power. its nice to see a fun application of my physics classes. the difference in weight is pretty small though.

the horsepower numbers seem to be the most innacurate to me anyway. they have to assume some kind of rolling resistance and air resistance which will be different for every vehicle. you have to know how much force it takes to move a vehicle. because in an ideal case it takes no force to move at constant velocity but that is certainly not true. i was mostly concerned with the times.

stephendurda · 11-20-2009, 01:22 PM

Fair enough, the HP is definitely what I'd put the least stock in with that app. I noticed on another thread you've got 245/75's on your WK with no rubbing. Seems like a good compromise for those of us not wheeling all the time to help fill out the wheel well. Don't like how undersized mine look right now. Unfortunately the Michelins on there are basically brand new, so I'll have them for a while.

konarider94 · 11-23-2009, 05:21 PM

Quote:

Originally Posted by stephendurda

Fair enough, the HP is definitely what I'd put the least stock in with that app. I noticed on another thread you've got 245/75's on your WK with no rubbing. Seems like a good compromise for those of us not wheeling all the time to help fill out the wheel well. Don't like how undersized mine look right now. Unfortunately the Michelins on there are basically brand new, so I'll have them for a while.

yea the 245/75's look great and i still think ill put a 2" lift on it. if turning and you hit a big bump it will rub just a lil bit, nothing major though. on flat ground there is no rubbing at all. i just want a 2" lift to get rid of that rake and then it wont rub at all

dsalinas · 11-23-2009, 11:33 PM

I run 255/70s, and I definately believe I lose around 3-4tenths of a second compared to stock. If this is in the ballpark of what is lost, I would be running 6.1-6.2secs 0-60 with stock tire size.

HurriJeff · 11-25-2009, 10:41 PM

Hey konarider94,
Is your WK 4wd? What value did you use as your driveline loss ? Thats a hard number to find!

konarider94 · 11-25-2009, 11:51 PM

I dont think they make a 2wd hemi. But yea it has the QD2. I put in 0% to get an estimate of wheel hp. Power at the crank is a pretty useless number.