How bad bigger tires effect E.T's
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From: W.V.C. Utah
How bad bigger tires effect E.T's
Last Friday I ran my Iroc and it pulled a 14.7 @90 with a 1.646 60'
Right now I have 255 50 16 Kumho ecsta supras on it if I put a set of 28" drag radials on it how bad will it effect my times? I have 3.42's in the rear. I'm thinking it will hurt my times pretty bad.
Right now I have 255 50 16 Kumho ecsta supras on it if I put a set of 28" drag radials on it how bad will it effect my times? I have 3.42's in the rear. I'm thinking it will hurt my times pretty bad.
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From: SE NY
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Lets say your stock tires are the same dia as those on my '88 Vette, ie 25.5". If you go to 28" DRs (2.5" increase in dia) you will lose 10% of torque to the pavement. And a DR is usually run with much lower inflation than a street tire, which will increase rolling resistance.
Unless you can launch harder with the DRs I suspect you will lose some performance going to the taller tire.
Unless you can launch harder with the DRs I suspect you will lose some performance going to the taller tire.
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From: W.V.C. Utah
Originally Posted by 65Z01
Lets say your stock tires are the same dia as those on my '88 Vette, ie 25.5". If you go to 28" DRs (2.5" increase in dia) you will lose 10% of torque to the pavement. And a DR is usually run with much lower inflation than a street tire, which will increase rolling resistance.
Unless you can launch harder with the DRs I suspect you will lose some performance going to the taller tire.
Unless you can launch harder with the DRs I suspect you will lose some performance going to the taller tire.
going for fastest stock block iroc 60' times 
from what I can tell 1.646 is the quickest for 255 50 16 street tires
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From: W.V.C. Utah
Originally Posted by 93 ragtop
did you run more then 1 run in the 1.64 range? The reason I ask is 14.7 sec. at 90 mph seems way low for a 1.64 60 ft time. Expecially on street tires.
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From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
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I went with 17 x 11's with 315's on the back and switched to 17 x 9.5's up front with 275's. The wheel/tire combo weighed 5 lbs more each, so that's an additional 20 pounds of unsprung weight.
My car slowed from 13.20's to 13.60's and worse.
My car slowed from 13.20's to 13.60's and worse.
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From: Everyday you must choose between the pain of discipline and the pain of regret. Fredericktown, OH
Originally Posted by 93 ragtop
did you run more then 1 run in the 1.64 range? The reason I ask is 14.7 sec. at 90 mph seems way low for a 1.64 60 ft time. Expecially on street tires.
I agree. The car is 2-3 SECONDS slow ET-wise for that 60'. If it makes enough power and torque to 60' like that, I don't know how it runs high 14s at only 90.
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From: W.V.C. Utah
Originally Posted by LT-4 CE
I agree. The car is 2-3 SECONDS slow ET-wise for that 60'. If it makes enough power and torque to 60' like that, I don't know how it runs high 14s at only 90.
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From: Hinckley Ohio
Originally Posted by 88421VETTE
Last Friday I ran my Iroc and it pulled a 14.7 @90 with a 1.646 60'
Right now I have 255 50 16 Kumho ecsta supras on it
Right now I have 255 50 16 Kumho ecsta supras on it
I am no expert but that ought to make Kumho ecsta supras the hottest tire around........
Do you have some mods to transfer weight to the rear or ??? Or just terrific track prep??? Or am I just not up on what kind of 60' times you can pull with an auto???
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From: W.V.C. Utah
Originally Posted by LT4BUD
Holy cows.......a 1.646 on 255 50 16 street tires......
I am no expert but that ought to make Kumho ecsta supras the hottest tire around........
Do you have some mods to transfer weight to the rear or ??? Or just terrific track prep??? Or am I just not up on what kind of 60' times you can pull with an auto???
I am no expert but that ought to make Kumho ecsta supras the hottest tire around........
Do you have some mods to transfer weight to the rear or ??? Or just terrific track prep??? Or am I just not up on what kind of 60' times you can pull with an auto???
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From: The Top of Utah
Originally Posted by LT-4 CE
I agree. The car is 2-3 SECONDS slow ET-wise for that 60'. If it makes enough power and torque to 60' like that, I don't know how it runs high 14s at only 90.
Installing a larger diameter tire is the same as changing to higher rear end gears. Your 3.42's will act more like 3.07's. Is all comes down to engine revolutions per mile.
That is an AMAZING 60' time for that ET at ANY altitude.
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From: Redding Ca
With a larger tire, your overrall ET might actually improve. 1.6 - 60'time is incredible for your 1/4 performance. I suspect you are completely through the engine's power curv and in 3rd gear before half track. 
A taller tire might keep you in the fat part of the power curve longer. Although the 3.42 rear gear is not too low. My 87 Pontiac GTA with 3.27 gears, 700r, was almost perfect combination for DD-street and strip. I got 1.85's 60 footers with DR's at 13.30's, 104. Your times are really outside the norm. I think your short tires are screwing you up. 
A taller tire might keep you in the fat part of the power curve longer. Although the 3.42 rear gear is not too low. My 87 Pontiac GTA with 3.27 gears, 700r, was almost perfect combination for DD-street and strip. I got 1.85's 60 footers with DR's at 13.30's, 104. Your times are really outside the norm. I think your short tires are screwing you up.
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From: SE NY
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What are your shift points?
With those gears it really benefits you to stay in each lower gear as long as possible due to the 700R/4 gearing. This means that you should be shifting above the HP peak of the engine.
My modified TPI intake (siamese base) lets my L98 build peak HP at 4,800rpm but I get best 1/4 mile times with a shift point of 5,800rpm.
If you can get consistent runs, try shifting maybe 300-500rpm higher to see if ET drops any.
With those gears it really benefits you to stay in each lower gear as long as possible due to the 700R/4 gearing. This means that you should be shifting above the HP peak of the engine.
My modified TPI intake (siamese base) lets my L98 build peak HP at 4,800rpm but I get best 1/4 mile times with a shift point of 5,800rpm.
If you can get consistent runs, try shifting maybe 300-500rpm higher to see if ET drops any.
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From: Everyday you must choose between the pain of discipline and the pain of regret. Fredericktown, OH
I didn't see that 60' time was on Kuhmo Excta.
If you haven't been under 1.80 on the same day or even since, I'd begin to wonder if that wasn't an error on the time sheet. It takes a really decent suspension to get a mid-low 1.60 60' time, particularly in a car not making any power.
With good suspension and tires, it would take 400 lb ft. of torque (or close) to get a car that heavy to 60' that low. Now, on legit street tires, and average ones at that, it would be another game all together.
With my former Nova, I made the progression from running high 14s at 90-ish to low 11s at 117+ and played around with street tires, ET streets, but mostly slicks as I was a dedicated bracket racer. And I have seen tons of cars, and even with a factor for elevation, I have a difficult time with a 1.64 60' on street tires and a 14.70 at 90 MPH.
While it may not sound like it, I want to believe you and see how this shakes out as you play with tire size. I am curious what the interval times were on that pass (330 and 660).
If you haven't been under 1.80 on the same day or even since, I'd begin to wonder if that wasn't an error on the time sheet. It takes a really decent suspension to get a mid-low 1.60 60' time, particularly in a car not making any power.
With good suspension and tires, it would take 400 lb ft. of torque (or close) to get a car that heavy to 60' that low. Now, on legit street tires, and average ones at that, it would be another game all together.
With my former Nova, I made the progression from running high 14s at 90-ish to low 11s at 117+ and played around with street tires, ET streets, but mostly slicks as I was a dedicated bracket racer. And I have seen tons of cars, and even with a factor for elevation, I have a difficult time with a 1.64 60' on street tires and a 14.70 at 90 MPH.
While it may not sound like it, I want to believe you and see how this shakes out as you play with tire size. I am curious what the interval times were on that pass (330 and 660).
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From: W.V.C. Utah
Originally Posted by 65Z01
What are your shift points?
With those gears it really benefits you to stay in each lower gear as long as possible due to the 700R/4 gearing. This means that you should be shifting above the HP peak of the engine.
My modified TPI intake (siamese base) lets my L98 build peak HP at 4,800rpm but I get best 1/4 mile times with a shift point of 5,800rpm.
If you can get consistent runs, try shifting maybe 300-500rpm higher to see if ET drops any.
With those gears it really benefits you to stay in each lower gear as long as possible due to the 700R/4 gearing. This means that you should be shifting above the HP peak of the engine.
My modified TPI intake (siamese base) lets my L98 build peak HP at 4,800rpm but I get best 1/4 mile times with a shift point of 5,800rpm.
If you can get consistent runs, try shifting maybe 300-500rpm higher to see if ET drops any.
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From: Hinckley Ohio
Originally Posted by 88421VETTE
My car is all low end torque the next 2 runs I got a little throttle happy on the burnout and made my tires very greasy and spun the tires all the way through first gear and half way through second but still pulled a 2.1 and 2.2 60' :
The et should have been a lot less.....like 15.2 or less.....
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From: Mount Vernon OH
Wait a minute...
I want to get this right...you said:
"Last Friday I ran my Iroc and it pulled a 14.7 @90 with a 1.646 60'".
I didn't read anywhere that you were rear ended by a super gas car that pushed your through the sixty foot timers so I am guessing you actually think you ran a 1.646 sixty foot time. I have been around the dragstrip roughly 20 years and what you are describing just doesn't add up to me. So let's try to figure out what is missing in this equation.
What was your 1/8 mile time and mph? If your car has the torque you say it does it should be a real puller on the first half of the track and it should should lay down on the top end of the track. If it can come out of the hole solid it can pull to the 1/8 mile without peaking in 3rd gear...thus the time and mph should really rock in the 1/8.
If your car makes a lots of torque I can't understand why is it not pulling in 3rd gear past 4300 rpm or running a higher MPH.
"Last Friday I ran my Iroc and it pulled a 14.7 @90 with a 1.646 60'".
I didn't read anywhere that you were rear ended by a super gas car that pushed your through the sixty foot timers so I am guessing you actually think you ran a 1.646 sixty foot time. I have been around the dragstrip roughly 20 years and what you are describing just doesn't add up to me. So let's try to figure out what is missing in this equation.
What was your 1/8 mile time and mph? If your car has the torque you say it does it should be a real puller on the first half of the track and it should should lay down on the top end of the track. If it can come out of the hole solid it can pull to the 1/8 mile without peaking in 3rd gear...thus the time and mph should really rock in the 1/8.
If your car makes a lots of torque I can't understand why is it not pulling in 3rd gear past 4300 rpm or running a higher MPH.
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From: W.V.C. Utah
here is my time slip numbers
If I new how to post Videos I have the Video of the run I ran against a 00 Mustang GT with a 5spd 4.10 gears and 275 40 18 DR's he had a better Reaction (.307 to my .772) time but on the Video you can see me Quickly catch up then he starts to pull away after 300' or so he pulled a 1.9 60' If I can find a way to post the vid I will
RT .772
60' 1.646
330 5.848
1/8 9.274
mph 71.17
1000 12.253
1/4 14.762
mph 90.08
with the 2.1 and 2.2 60's I pulled a 15.1 and 15.2 both at 90mph
If I new how to post Videos I have the Video of the run I ran against a 00 Mustang GT with a 5spd 4.10 gears and 275 40 18 DR's he had a better Reaction (.307 to my .772) time but on the Video you can see me Quickly catch up then he starts to pull away after 300' or so he pulled a 1.9 60' If I can find a way to post the vid I will
RT .772
60' 1.646
330 5.848
1/8 9.274
mph 71.17
1000 12.253
1/4 14.762
mph 90.08
with the 2.1 and 2.2 60's I pulled a 15.1 and 15.2 both at 90mph