DABKO
Well-Known Member
- Joined
- Jul 9, 2014
- Threads
- 21
- Messages
- 359
- Reaction score
- 348
- Location
- Livonia, MI
- First Name
- Greg
- Vehicle(s)
- 2019 DHG Bullitt & 2001 DHG Bullitt
- Thread starter
- #1
Last June I bought a set of M/T ET Street Rs in the 305/45R17 size. Last summer was my first real serious effort running this car at the drag strip.
My car is a stock '15 GT Premium Automatic with the 3.55:1 axle ratio.
This being my first experience with DRs, these Street Rs are an outstanding tire, for my application, they may actually work too well.
With the tires heated up, I launch at 1500 rpm and do not experience any wheel spin. Plus, the car bogs a bit around the 60 foot mark.
My best time for the 1/4 has been 12.678 @ 111.26 mph with a 1.888 second 60 foot. In general, my 60 foot times are in the 1.9 range.
I'm thinking that maybe this tire size is a bit much (width and diameter) for this stock configuration. Versus the stock 235/50R18 tires, these 305/45R17's make the overall axle ratio taller by about 2% (numerically lower).
Looking at the M/T catalog, they offer a Street R in the 275/40R17 size. This tire will have a smaller diameter than the 235/50R18 stock tire and will result in a 6% shorter overall axle ratio (numerically higher).
To help with my 60 ft times, I'm thinking I need some level of wheel spin off the line that a narrower and smaller diameter tire should provide.
Any comments or suggestions?
Run the 305's one more season and try to improve the launches or switch to the 275's? I have a buyer for the 305s and the out of pocket switch would be minimal.
I'm stuck with the 17" tire diameter as I want to keep the Race Star Bracket Racer wheels.
I'm thinking about only adding a tune, either the Ford Power Pack 2 or a Livernois tune. Not sure if the tunes would add low end torque to help with the launches. No other mods planned as I will be updating to another S550 in the next couple of years.
One thing to note is that when I run the line lock with these 305s, after a few seconds of wheel spin, the tires start to grip and actually push the whole car forward. When running on concrete, I end up with 4 tire patches; two from the DRs and two fainter ones from the front 235s.
Thanks.
My car is a stock '15 GT Premium Automatic with the 3.55:1 axle ratio.
This being my first experience with DRs, these Street Rs are an outstanding tire, for my application, they may actually work too well.
With the tires heated up, I launch at 1500 rpm and do not experience any wheel spin. Plus, the car bogs a bit around the 60 foot mark.
My best time for the 1/4 has been 12.678 @ 111.26 mph with a 1.888 second 60 foot. In general, my 60 foot times are in the 1.9 range.
I'm thinking that maybe this tire size is a bit much (width and diameter) for this stock configuration. Versus the stock 235/50R18 tires, these 305/45R17's make the overall axle ratio taller by about 2% (numerically lower).
Looking at the M/T catalog, they offer a Street R in the 275/40R17 size. This tire will have a smaller diameter than the 235/50R18 stock tire and will result in a 6% shorter overall axle ratio (numerically higher).
To help with my 60 ft times, I'm thinking I need some level of wheel spin off the line that a narrower and smaller diameter tire should provide.
Any comments or suggestions?
Run the 305's one more season and try to improve the launches or switch to the 275's? I have a buyer for the 305s and the out of pocket switch would be minimal.
I'm stuck with the 17" tire diameter as I want to keep the Race Star Bracket Racer wheels.
I'm thinking about only adding a tune, either the Ford Power Pack 2 or a Livernois tune. Not sure if the tunes would add low end torque to help with the launches. No other mods planned as I will be updating to another S550 in the next couple of years.
One thing to note is that when I run the line lock with these 305s, after a few seconds of wheel spin, the tires start to grip and actually push the whole car forward. When running on concrete, I end up with 4 tire patches; two from the DRs and two fainter ones from the front 235s.
Thanks.
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