A6 Drag racing. 3.15 with 26" tire vs 3.31 with a 28" tire.

[Bmr4life]

The reading I've done shows that the fastest N/A auto Coyotes are running 3.31 rear gears in the back. In order to stay in 3rd through the stripe, they run a 28" tall tire.

If you run a tire that large, what is the true benefit of using 3.31? Math shows that the larger target negates the benefit of the higher rear end gear?

I'm not doubting the results, just trying to understand what makes this combination better since I am considering gears as one of my next mods.

 

[ViciousJay]

Smaller gear you want a taller tire, and vice versa

 

[Bmr4life]

I get that, I'm trying to understand why the gear swap to 3.31 is done in the first place if you're just going to add a bigger tire that negates it. I doubt (but could be wrong) that someone is so gungho about running a 28" tire that they would swap from 3.15 to 3.31.

In the comparison I posted, is there any benefit to 3.31 with 28" versus 3.15 with 26"? Would the fastest NA cars be just as fast if they stayed 3.15 with 26"?

 

[corepwn]

It's easier to hook the larger tire. Generally people with a power adder will move up to 28s and 3.31s which essentially keeps the factory ratio.

 

[Bmr4life]

Thanks, so that just leaves installing a Circle D or saving up for FI.

 

[Scuba-Matt]

The reading I've done shows that the fastest N/A auto Coyotes are running 3.31 rear gears in the back. In order to stay in 3rd through the stripe, they run a 28" tall tire.

If you run a tire that large, what is the true benefit of using 3.31? Math shows that the larger target negates the benefit of the higher rear end gear?

I'm not doubting the results, just trying to understand what makes this combination better since I am considering gears as one of my next mods.

The 28" tire is going to have a longer contact patch with the pavement vs the 26"
Thats why the 28" tire.

 

[calgarybandit]

I run a 315/30/20 Toyo Proxes R888 27.44 tall tire I ran 11.91 116.9MPH 1.769 60ft at 4400 DA screaming through the line at 7500 RPM in 3rd gear :rockon:

 

[Strpperpolef150]

The 28" tire is going to have a longer contact patch with the pavement vs the 26"
Thats why the 28" tire.

^^ this plus a larger sidewall allowing for more wrinkle

 

[try03venom]

3.15 and 28" tire will cross the stripe at what rpm?

 

[Big Ben]

Great thread. I am about to purchase 275/50-17 M&H tires which are 28" tall to go on some 17 inch bullets I have. I am assuming that I will have to go to a 3.31 then? Sucks as I have new set of 3.55's sitting in a box.

My other option is some 26 inch slicks on 15x8 94 Mustang Pony rim but will these hook enough launching on a 125 shot?

 

[Bmr4life]

I run a 315/30/20 Toyo Proxes R888 27.44 tall tire I ran 11.91 116.9MPH 1.769 60ft at 4400 DA screaming through the line at 7500 RPM in 3rd gear :rockon:

So were you stock or 3.31?

 

[calgarybandit]

So were you stock or 3.31?

No I had 3.73, 4.10 & 3.55 until I found the right combo 3.31 with my converter etc be perfect for when I throw a supercharger on also.

 

[GeorgeInNePa]

The reading I've done shows that the fastest N/A auto Coyotes are running 3.31 rear gears in the back. In order to stay in 3rd through the stripe, they run a 28" tall tire.

If you run a tire that large, what is the true benefit of using 3.31? Math shows that the larger target negates the benefit of the higher rear end gear?

I'm not doubting the results, just trying to understand what makes this combination better since I am considering gears as one of my next mods.

Using a great little speadsheet that I got from wbt, a 3.15 gear, 26" tire, A6 Coyote will have a max MPH of 121.21 @7500RPM, in 3rd gear.

With 3.31s and 28" tires, the same car has a max of 124.22MPH, also at 7500.

3.15s, 27" = 125.87

3.15s, 28" = 130.53

3.55s, 30" = 124.10

PS,
If you are willing to rev to 7700 in 3rd, the 26" tire will get you a max of 124.44

Remember, all these are figured with the tires being as tall as stated. If your 26" tire is actually only 25.7" tall, it skews the numbers quite a bit.

That 7700 RPM limit now gets you only 123.01MPH...

 

[Bmr4life]

Using a great little speadsheet that I got from wbt, a 3.15 gear, 26" tire, A6 Coyote will have a max MPH of 121.21 @7500RPM, in 3rd gear.

With 3.31s and 28" tires, the same car has a max of 124.22MPH, also at 7500.

3.15s, 27" = 125.87

3.15s, 28" = 130.53

3.55s, 30" = 124.10

PS,
If you are willing to rev to 7700 in 3rd, the 26" tire will get you a max of 124.44

Remember, all these are figured with the tires being as tall as stated. If your 26" tire is actually only 25.7" tall, it skews the numbers quite a bit.

That 7700 RPM limit now gets you only 123.01MPH...

Yup, my spreadsheet shows the same data, which led me to this question in the first place. I couldn't see the benefit of running 3.31 with 28" over stock with 26". I get the larger contact patch point, but its only going to be a little bigger. Then I thought that maybe people were running a 26" with the 3.31, but it would max out at ~115mph at 7500 which isn't good.

 

[GeorgeInNePa]

Yup, my spreadsheet shows the same data, which led me to this question in the first place. I couldn't see the benefit of running 3.31 with 28" over stock with 26". I get the larger contact patch point, but its only going to be a little bigger.

The point is, 3.15s and 26" tires will not get you the MPH of the faster NA cars. Many 26" drag radials are slightly shorter than 26". MANY people will not rev their stock bottom end that high, hence the recommendation for 3.31s and 28" tires.

 

[Bmr4life]

The point is, 3.15s and 26" tires will not get you the MPH of the faster NA cars. Many 26" drag radials are slightly shorter than 26". MANY people will not rev their stock bottom end that high, hence the recommendation for 3.31s and 28" tires.

Is there a 27" race tire, because if there is 3.15 with a 27" is better than 3.31 with a 28" if mph in 3rd gear is the main concern.

 

[GeorgeInNePa]

Is there a 27" race tire, because if there is 3.15 with a 27" is better than 3.31 with a 28" if mph in 3rd gear is the main concern.

Hoosier makes some 27" Quick Time Pro bias tires and I think MT makes a ET Street in 27" also. I haven't found any drag radials in 27".

 

[Bmr4life]

Hoosier makes some 27" Quick Time Pro bias tires and I think MT makes a ET Street in 27" also. I haven't found any drag radials in 27".

I checked it out, MT makes a 295/45R17 DR. Its under ET Street Radial II.

 

[Squamishcoyote]

Meanwhile us M6 3.73 guys are screwed

 

[Scuba-Matt]

Meanwhile us M6 3.73 guys are screwed

How is that?