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Old 11-02-2020, 04:24 PM   #43
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Originally Posted by RobbyBeefcake87 View Post
I've seen some dip into the 1.8s as well. There's a guy that just posted a 1.7 60' on a 12.0 run with a stock m6 1le. I figured stock for stock eventually a 1le would probably get the best m6 60' due to a tire advantage.

Excited to see what the new a10 1le's do with the 2.85 rear end.
what sucks is he must've really botched 3-4 on that 12.0 run. car went 90 in the 1/8 and only 113 in the 1/4? wheres the other 3 mph?

i don't see the auto 1LE doing any better because of the gear ratio. maybe the tire.
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Old 11-03-2020, 07:55 AM   #44
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what sucks is he must've really botched 3-4 on that 12.0 run. car went 90 in the 1/8 and only 113 in the 1/4? wheres the other 3 mph?

i don't see the auto 1LE doing any better because of the gear ratio. maybe the tire.
Yea I think the tire and slightly more aggressive 2.85 rear end combo might yield nice results, but probably mostly the tire.

Yea that mph wasn't very impressive, I've gone a bit faster on 13 second runs lol.. could also be an error or issue with the track sensors, who knows.
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Old 02-02-2021, 04:46 PM   #45
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I got a 1.75 60 ft on a M/T ET Street S/S with just a K&N Blackwing Cold Air Intake & Ported Throttle Body 11.66@119.79
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Old 02-02-2021, 05:29 PM   #46
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I got a 1.75 60 ft on a M/T ET Street S/S with just a K&N Blackwing Cold Air Intake & Ported Throttle Body 11.66@119.79
Super nice pass, congrats for sure. Running a 10 speed auto ? do you remember if the car stayed in 5th gear thru the traps? or did up upshift real close to the end of the 1/4?. Great MPH, car is making some horse power, what was the DA or what was the temp? Did you flat foot the car off idle or did you foot brake torque it up and then go? I am prepping my 2021 LT1 10 speed auto to get do at least a 11.80 pass, please understand my interest and thank you.
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Old 02-04-2021, 03:44 PM   #47
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I think you guys are bass-ackwards on your shift point thinking. If the car shifts by MPH from the rear wheels, then a taller rear tire will make your shift point (rpm) higher. A smaller tire will see more revolutions of the tire at a given MPH. So the car will THINK it’s doing 60mph when in fact it’s only doing 58 mph.

I just put a set of the 275 35 20 Nitto 555r2’s on my car yesterday. The stock LT1 with run flats says they are 27.77 inches diameter according to the tire spec. The 555r says it is 27.56. Pretty close so I went with it. The car shifts at 6300 rpm in full auto. I didn’t pay attention to where it shifted before I put the tires on but plan on switching back in order to check. My phone GPS shows the car to be off by 1 mph. The car will show 60mph when my phone GPS shows 59mph.

Despite the measurements per the specs, here is a side by side of the stock 245 against the Nitto 275/35. I’ll tell you what the REAL measurements are in the next few days as I’m going to measure them.
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Old 02-04-2021, 04:43 PM   #48
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I think you guys are bass-ackwards on your shift point thinking. If the car shifts by MPH from the rear wheels, then a taller rear tire will make your shift point (rpm) higher. A smaller tire will see more revolutions of the tire at a given MPH. So the car will THINK it’s doing 60mph when in fact it’s only doing 58 mph.

I just put a set of the 275 35 20 Nitto 555r2’s on my car yesterday. The stock LT1 with run flats says they are 27.77 inches diameter according to the tire spec. The 555r says it is 27.56. Pretty close so I went with it. The car shifts at 6300 rpm in full auto. I didn’t pay attention to where it shifted before I put the tires on but plan on switching back in order to check. My phone GPS shows the car to be off by 1 mph. The car will show 60mph when my phone GPS shows 59mph.

Despite the measurements per the specs, here is a side by side of the stock 245 against the Nitto 275/35. I’ll tell you what the REAL measurements are in the next few days as I’m going to measure them.
Its been shown the A10 upshifts at WOT by a mph table for each individual gear. If MPH is measured thru the output shaft of the transmission, actual MPH would be sensitive to tire diameter. If a smaller tire diameter makes a actual MPh reading faster by lets say 2mph compared to actual road speed, the trans will still shift at the same programmed MPH but the car will be going 2 mph slower. This scenario should have affect on RPM imo. If the MPH reading came from a front wheel, now the WOT shift should be at a higher RPM because the rear wheels and trans output shaft speed is 2mph faster than the front and the engine should be at a higher rpm at wot shift point. My understanding is if you want to increase the RPM WOT shift points, you have to just go into the MPH wot shift setting and up the MPH for each gear accordingly to get closer to a 6500 rpm shift point and the 2020 and 2021 A10 transmissions are not tunable yet.
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Old 02-04-2021, 05:34 PM   #49
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Super nice pass, congrats for sure. Running a 10 speed auto ? do you remember if the car stayed in 5th gear thru the traps? or did up upshift real close to the end of the 1/4?. Great MPH, car is making some horse power, what was the DA or what was the temp? Did you flat foot the car off idle or did you foot brake torque it up and then go? I am prepping my 2021 LT1 10 speed auto to get do at least a 11.80 pass, please understand my interest and thank you.
Yes 10 speed automatic DA was 312 on that run and just off idle not sure what gear it was in at the traps I’m sure 11.50’s in a negative DA car put down 404 rwhp bone stock
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Old 02-04-2021, 05:49 PM   #50
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I got a 1.75 60 ft on a M/T ET Street S/S with just a K&N Blackwing Cold Air Intake & Ported Throttle Body 11.66@119.79
What size were the M/T ET street s/s tires?
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Old 02-04-2021, 07:21 PM   #51
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If a smaller tire diameter makes a actual MPh reading faster by lets say 2mph compared to actual road speed, the trans will still shift at the same programmed MPH but the car will be going 2 mph slower. This scenario should have affect on RPM imo..
Exactly why a smaller tire would make the car shift at a lesser RPM. In stock form let’s say the 2-3 shift happens at 60mph and in stock form let’s say that is exactly at 6500 rpm. In stock form that’s 726 rpm at the wheel assuming stock tire diameter 27.77. So if the cars computer is in stock form, it says when that tire is spinning at 726 rpm, we must be at 60 mph...time to do the 2-3 shift. If we go with a 1” smaller diameter of 26.77 and the car is still in stock form, it’s looking for that 726 RPM of the tire to know when to do that 2-3 shift which in stock form we said equated to 6500 engine RPM. The problem is that with a 1 inch smaller tire, 726 wheel rpm is only really 57.8 mph and the engine RPM that requires 726 revolutions at the wheel in 2nd gear with the smaller tire will be less than 6500 rpm thus short shifting happens.

At least that’s my theory!
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Old 02-05-2021, 06:31 PM   #52
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So I swapped the wheels back to stock and measured them. The Nitto 555R2 275/35/20 has a circumference of 86.875 / 3.147 that’s 27.60. The advertise 27.56 so pretty damn close! The stock run flat measured a circumference of 87.750 / 3.147 is 27.88 so pretty damn close to their specs too. Despite the optical illusion in the picture, they are in fact pretty close in size.

Then with the stock setup against my phone GPS the speedometer was off by the same as the DR’s and the shift points were pretty much the same too. Looks like we won’t know how tires change shift points until someone does similar experiments with tires more different in size vs stock.
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Old 02-05-2021, 09:47 PM   #53
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What size were the M/T ET street s/s tires?
305/45/17 28” tall
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Old 02-06-2021, 03:40 AM   #54
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Exactly why a smaller tire would make the car shift at a lesser RPM. In stock form let’s say the 2-3 shift happens at 60mph and in stock form let’s say that is exactly at 6500 rpm. In stock form that’s 726 rpm at the wheel assuming stock tire diameter 27.77. So if the cars computer is in stock form, it says when that tire is spinning at 726 rpm, we must be at 60 mph...time to do the 2-3 shift. If we go with a 1” smaller diameter of 26.77 and the car is still in stock form, it’s looking for that 726 RPM of the tire to know when to do that 2-3 shift which in stock form we said equated to 6500 engine RPM. The problem is that with a 1 inch smaller tire, 726 wheel rpm is only really 57.8 mph and the engine RPM that requires 726 revolutions at the wheel in 2nd gear with the smaller tire will be less than 6500 rpm thus short shifting happens.

At least that’s my theory!
Close, but not quite. It's the exact opposite. These A8/A10 shift by MPH, not RPM. If the car is programmed to shift at lets say 60 mph (6500rpm) with the stock tire. If you use a shorter tire, it'll take maybe 6800 rpms to reach 60 mph and you'll bounce off the limiter by the time the shift actually happens.

I know this because I went to the track with shifting set at stock tire height, but at the track I switched to my 26" DR. I hit the limiter on my 1-2, 2-3, 3-4 shifts. Informed my tuner and 1st thing he said was "are you using a shorter tire?". He sent me a new tune with lower mph shift points.
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Old 02-06-2021, 07:42 AM   #55
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Close, but not quite. It's the exact opposite. These A8/A10 shift by MPH, not RPM. If the car is programmed to shift at lets say 60 mph (6500rpm) with the stock tire. If you use a shorter tire, it'll take maybe 6800 rpms to reach 60 mph and you'll bounce off the limiter by the time the shift actually happens.

I know this because I went to the track with shifting set at stock tire height, but at the track I switched to my 26" DR. I hit the limiter on my 1-2, 2-3, 3-4 shifts. Informed my tuner and 1st thing he said was "are you using a shorter tire?". He sent me a new tune with lower mph shift points.

Actually, the transmission shifts by MPH AND RPM. The shift is a two-step process that is MPH Initiated and RPM Completed. The shift tables require both parameters. I pay a lot of attention to shift points and log every run on the drag strip to tweak the tune shift points.

The shift is initiated at the MPH number in tune (can vary 1 MPH) and completed at the RPM number in the tune (again this can vary by 50-75 RPM or more). Think of it as "nominal" 6500 RPM if that is the target.

For example, my 2-3 shift will initiate at 45 MPH and complete at 6543 RPM (50 MPH). 3-4 shift initiates at 72 MPH, completes at 75 MPH and 4-5 shift initiates at 95 MPH, completes at 95 or 96 MPH.

The 4-5 shift illustrates that the shift will not initiate until the target MPH is reached and if the RPM already exceeds the parameter in the tune the shift will complete almost immediately with only 33 RPMs between initiation and completion.

As for tires, the computer looks at tire height (measured with tire on car sitting on ground) not diameter. There is a place in the tune for that number and it affects the transmission shift points and speedometer. IF you put a taller or shorter tire on the car and don't change that parameter in the tune it will not shift correctly, as grandpa_ss said.

I don't want to question your tuner or you grandpa (and this could be just a matter of semantics), but I would not want lower shift points alone to fix the problem, I would also want the correct tire height parameter changed in the tune.

Of course, that would mean one tune for your street tires and another one for the drag strip.
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Old 02-06-2021, 07:58 AM   #56
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I run the 305-35-19 Nitto 555r2s and really like them for my power level. My best et with those are 11.18@125 w/1.63 60ft. Just a few simple mods, E85, Speed Engineering long tubes and not cats. My C7 consistently hooks every time and rarely see over a 1.67 60ft. I hope to do some tuning on the tranny and break into the 10s this spring. I may need to find a ported MSD if I can't do it with just tuning. I know my Vette is a couple hundred pounds lighter then the Camaro so that is worth a couple tenths. The 305 I run is bout 1/2" taller then the 285 so I don't see any advantage with a 10 speed of running a shorter tire then stock since the A10 has a lower 1st gear the my A8. Yosh6 is right on the shifting on the RPM and MPH, its critical to have those correct so it shifts on time and doesn't hit the rev limiter.
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