Thinking about a half mile or mile event in my future. What tires do you run or recommend for a 900+hp car?
Sent from my LGLS775 using the svtperformance.com mobile app
Sent from my LGLS775 using the svtperformance.com mobile app
Van315/40/19 R7 from Hoosier Tire for rear. When we have had them made we worked with Hoosier Tire West in Fresno, CA. Depending on your set up the other item to look at is a 2.73 rear gear.
The reason I like the Torque Arm in the rear suspension is the fact the Instant Center is constantly moving with the factory 3 point suspension system. Once you remove the upper control arm and install the TA, the Instant Center never migrates as the body rises or drops on the springs as the car travels over different road surface conditions. The factory 3 point will change the Instant Center of the rear suspension as it travels through its range of motion. This can cause traction issues to occur at the most inopportune time with the worst being snap oversteer. Fortunately with all 1/2 mile and mile events the surface is flat and you'll experience only small changes in this as you go down the course. Having all spherical bearings in the rear suspension allows for it to move with free roll travel without any bushing induced binding, which would be similar to running a slightly stiffer spring.
Looks like i have most of the necessities ill have to make a few changes in the front
Rear runs a bmr watts link that has been welded to the axle. I have solid heims everywhere except on the a arms wich are poly... I built it to be a roll race car as that is what is popular around me, id like to branch out to half mile or mile events just looking for what else would be needed before i went. Wheel size play a factor or is just best to keep wheel weight down?
Sent from my LGLS775 using the svtperformance.com mobile app
Van
I understand the logic behind this gear change. I'm not arguing the point. It gives you an advantage of not having to shift to fifth gear, so you only need to make 3 shifts from the start to finish line. You also have less driveline power loses by running in the direct ratio of the transmission. Even a guy running an earlier stock motor with the 6250 RPM limit will net roughly 195 mph at the end of the mile by doing this 2.73 gear change with the 315/40/19 tire.
You clearly stated........depending on your set up. With that comment you are not saying this mod is for everyone.
What I want to clarify is if the car is going to be street driven regularly with an occasional trip to a 1/2 mile or mile race over the course of ownership this mod will create a down side for these people. Because it will make for a miserable time in traffic in urban areas with constant stop and go traffic. The 2.73 rear gear will more than likely require you as a driver to slip the clutch heavily to pull off from a traffic light or stop sign, let alone if you get caught in a traffic jam. This gear change will be hard on clutches. To those tempted to go mile racing keep in mind what you truly want the car to do for the majority of your seat time in the car.
ET or MPH?
I'm not sure how to post this without the post seeming to be argumentative with you Van. Its not meant to be construed in this manner. I want it to be informative for members to understand the gearing differences. I've thought about how to post without coming off as combative or putting you down. This is the only way I can explain itIt's not too far off of a 3.31 OEM gear in 07-09 GT500's and 13-14 GT500's. Couple that with a smaller tire in the rear (the Hoosier I mentioned is 29-30" tall) go 26-28" tall rear tire it's not as terrible as it may sound on the street.
I've had drag race and street customers call me and we discuss their set ups and tire sizes. Most have changed to 3.73 or 4.10 gears. Similar to what I have done at that mile eliminating a shift they go back to 3.31 or 3.08 gears (depending on their set up) and they manage to achieve their goals and run out the back in 3rd gear and lower their ET.
I'm not sure how to post this without the post seeming to be argumentative with you Van. Its not meant to be construed in this manner. I want it to be informative for members to understand the gearing differences. I've thought about how to post without coming off as combative or putting you down. This is the only way I can explain it
In the heavy truck world all trucks must pass a engineering review after the new owner specifies the option combination of the new truck he ordered. One of the things that must be reviewed is what is called in the industry is the start-ability or grade-ability factor in percent. What this comes down to is how the truck is being built for versus the driveline components specified(transmission & rear axle ratio) for the working being performed and whether the truck will be able to pull off from a stop in those specified conditions. Example would be a heavy dump truck(80K Lbs) that works off-road(soft soil conditions) versus a tractor trailer that never leaves the asphalt while never going over a gross weight of 50K lbs. What they do is look at what the first gear ratio of the transmission and multiply it by the rear axle ration, along with the torque output of the engine at idle versus the specified working conditions of the truck. They want the new owner to be able to start from a stop in whatever adverse conditions he plans on working the vehicle in without slipping the clutch or shock loading the drivelive by dumping the clutch above engine idle to start moving the truck.
Until 2013 all prior GT500 6 speed transmissions have a 2.96 gear ratio in first gear. The 13/14 MY cars have a 2.66 first gear ratio 6 speed transmission
Now lets do a little math to see the actual torque multiplication of the rear axle and transmission ratio combined in first gear
2.97 first gear x 2.73 rear axle ration = 8.1081 combined final gear ratio multiplication factor
2.66 first gear x 2.73 rear axle ration = 7.2618 combined final gear ratio multiplication factor
Since the 3.31 gear is a fast gear for these cars and is stock in the 13/14 MY cars we will use it next
2.97 first gear x 3.31 rear axle ratio = 9.8307 combined final gear ratio multiplication factor
2.66 first gear x 3.31 rear axle ratio = 8.8046 combined final gear ratio multiplication factor
now lets try a 3.15 rear axle ration
2.97 first gear ratio x 3.15 rear axle ratio = 9.3555 combined final gear ratio multiplication factor
2.66 first gear ratio x 3.15 rear axle ratio = 8.379 combined final gear ratio multiplication factor
how about a 3.08 rear axle ratio
2.97 first gear x 3.08 rear axle ratio = 9.1476 combined final gear ratio multiplication factor
2.66 first gear x 3.08 rear axle ration = 8.1928 combined final gear ratio multiplication factor
These comments are meant for everybody to read and comprehend......not for me to argue a point with Van. Everyone thinking of doing a dedicated mile or 1/2 mile car needs to understand what I'm writing if you plan on doing a gear change for top speed, plus driving the car on the street. You may also want to consider if you live in a hilly area where you need to pull off from a stop on a steep grade while tooling around in the car. The first gear of the transmission has as much factor when you look at the math calculations to starting from a stop as the rear axle ratio it is combined with.
As can be seen by doing a little math there are big differences in whether a car will pull off from a standing start more easily than another with different combinations of transmissions and rear axle ratios. Engine torque is always multiplied by each gear ratio it passes through before being applied to the road surface. You can also see that a car with a 13/14 MY transmission or a 2.66 first gear Magnum XL that these cars will be much harder to start from a static position compared to a car with an earlier transmission on the street with the exact same rear axle ratio. In fact the earlier 2.97 first gear transmission has a higher torque multiple combination with a 3.08 rear axle than the stock 13/14 MY car with a 3.31 gear ratio. The 2.73 gear ratio with a 2.96 first gear ratio will finally drop below the start-ability of a stock 13/14 MY car.
For drive-ability the combination of parts makes the sum of the whole and how a car responds to pulling off in first gear of the transmission. This is something nobody ever thinks about. The other thing is not only is first gear ratio different, but the other ratios are slightly different as you go up through the gear box. I believe there are 3 different 5th gear ratios depending on the MY of the transmission. So my point is for you the reader to consider the sum of the parts to make a decision about modifying the car for a dual purpose application.