[JFM-jr]

Boy did I burn the midnight oil looking over these time slips posted. Looking beyond the final ET and MPH I averaged the first 3 and the last 5 as separate groups and broke down the incrementals. The last 5 runs you were faster to the 1/8th in both ET and MPH by .045 ET and .45 MPH (oddly enough). Now here is where it gets interesting being the 4-5 shift that would normally take place would be beyond the 1K mark. The ET difference between the 1/8th and 1K foot averaged only .017 difference and from the 1K to the 1320 is only .020 so as far as ET goes you made the majority (slightly) of your ET before the 1/8th not after wich is where the 4-5 shift would take place. MPH different story you gained almost 2mph but only saw about about .037 from it. Roughly speaking the ET reduction was split over the run but MPH was favored in the back half of the 4th gear runs.

.5 MPH at the 1/8th was worth .045 ET
2 MPH from 1/8th to 1/4 was worth .037 ET these are averages

Please feel free to double check my math here I went thru a lot of numbers and burnt a lot of time but as I look at every detail this was my findings.

[wnta1ss]

JFM-jr, I agree that the 'hold 4th' trick will only show a small difference on the ET, the difference is more in the mph. Those of us who have bracket raced and came off the throttle or 'dumped it' near the finish have seen this in the other direction. 'Dumping' can lose a noticeable amount of trap speed, but the change in ET is not that big when it's done near the finish line.

It's still worth trying if your tires are tall enough that the car isn't going too fast for 4th. Every little gain right?

[Snowblind]

I've read your post JFM and wnta1ss and it gives good food for thought, I'm working 12hr shifts this weekend but I would like to talk this out.

Ultra's most recent pass makes a good comparison for this thread.

[PRAY]

Originally Posted by Snowblind

I've read your post JFM and wnta1ss and it gives good food for thought, I'm working 12hr shifts this weekend but I would like to talk this out.

Ultra's most recent pass makes a good comparison for this thread.

Ouch, sorry to hear about 12hr shifts on a weekend. Interesting stuff going on over here with all the data break down. Love it.

[wnta1ss]

I'm bringing this back up because there seems to be some interest in the subject showing up in the list thread.

Tire size and how fast the car goes will determine whether this is a trick that you can even try or not. On stock tires, an A8 will shut off around 111mph or so in 4th gear with stock rev limit. I have logged the stock tires at 109mph in 4th at 6409rpm, and the car shuts off when the tach touches 6500, at least it has for me. The speedometer in mine is very close with the stock tires, I have seen it within 1mph of timing lights.

[laynlo15]

Mine shuts off 120-121 with my slicks which are 28" tall but probably a little taller at the traps, they will grow where the Dr's will stay flat.

[wnta1ss]

With 305/45-17 Mickey Thompson drag radials, I saw the same thing that ULTRAZLS1 found with this size, the car with stock rev limit shuts off in 4th at 116.

[PRAY]

Who was running the 29" tires and getting it up to 119+? I can't remember now. The stock tires are not as tall as advertised. I have posted graphs proving that. My graphs are right in line with what wnta1ss is saying. To hold gear in a stock car you will need a 28" tall tire. The stock tire will have 4 shifts.

You will need a 29+" tire to hold gear into the 120's. Laynlo15's slicks are definitely growing at the end of the track. The calculator is telling me you will be at 6,563 at 121 with a 29" tall tire. A taller tire and holding gear seems to be the ticket on stock or lightly modded stock cars. Once you start modding you are going to have to executed 4 shifts. The real question is, what are taller tires doing for you then?

I bit the bullet and bought the Race Stars. I will be doing 305/45/17's 28" for the back and 27.5/4/17 27.8" for the fronts. You guys inspired me. I had to go full tilt with the drag pack. I am a bit worried that my 60fts and ET will suffer over the tire I was going to pick. I was going to run 285/35/18's on a different rim but it didn't work out. That tire is 26.9". I know I am going to have to execute 4 shifts no matter what. It seems to me that the smaller tire would 60ft better and already be going faster by the 4th shift and spend more time in 5th therefor being quicker and faster. What do you guys think?

[ULTRAZLS1]

Originally Posted by PRAY

Who was running the 29" tires and getting it up to 119+? I can't remember now. The stock tires are not as tall as advertised. I have posted graphs proving that. My graphs are right in line with what wnta1ss is saying. To hold gear in a stock car you will need a 28" tall tire. The stock tire will have 4 shifts.

You will need a 29+" tire to hold gear into the 120's. Laynlo15's slicks are definitely growing at the end of the track. The calculator is telling me you will be at 6,563 at 121 with a 29" tall tire. A taller tire and holding gear seems to be the ticket on stock or lightly modded stock cars. Once you start modding you are going to have to executed 4 shifts. The real question is, what are taller tires doing for you then?

I bit the bullet and bought the Race Stars. I will be doing 305/45/17's 28" for the back and 27.5/4/17 27.8" for the fronts. You guys inspired me. I had to go full tilt with the drag pack. I am a bit worried that my 60fts and ET will suffer over the tire I was going to pick. I was going to run 285/35/18's on a different rim but it didn't work out. That tire is 26.9". I know I am going to have to execute 4 shifts no matter what. It seems to me that the smaller tire would 60ft better and already be going faster by the 4th shift and spend more time in 5th therefor being quicker and faster. What do you guys think?

calculator says that's a 25.9 tire....

The calc also says nearly an inch narrower with an inch and a half less sidewall than 305/45/17. about the same sidewall as the stock 20s.

If they are that short...if even 26.9...being narrow, less sidewall and the increased gearing effect you could have some traction problems as a guess...

both hooking up....yeah you might go a touch faster on the 18.

and what about the future?...if they hooked up now you surely be having problems later. Ive seen some pretty healthy cars hookup on the mt et street r 305/45/17. I think you made the right choice overall.

[wnta1ss]

I agree with ULTRAZLS1, more tire was probably a better choice for you. Like he said, the future, you have that LT4 blower sitting on the shelf.

[PRAY]

Originally Posted by ULTRAZLS1

calculator says that's a 25.9 tire....

The calc also says nearly an inch narrower with an inch and a half less sidewall than 305/45/17. about the same sidewall as the stock 20s.

If they are that short...if even 26.9...being narrow, less sidewall and the increased gearing effect you could have some traction problems as a guess...

both hooking up....yeah you might go a touch faster on the 18.

and what about the future?...if they hooked up now you surely be having problems later. Ive seen some pretty healthy cars hookup on the mt et street r 305/45/17. I think you made the right choice overall.

I got the aspect ratio wrong. It must be a 40. It is the MT 285 that is 26.9" tall. I was trying to make it as apples to apples strictly for gearing issues. Tire height to tire height. Traction not being in the equation.

You are both correct. For my personal car with my future plans, the 305 is the ticket for sure. I plan on trapping 122-123 with everything dialed in on the E85. Who knows on the blower. I will need all the width and side wall I can get. Not to mention the 17" rim is lighter and the rotating mass is closer to the axle. The 17" rim and 305 will be such a huge change over my stock tires I will never know the difference.

[laynlo15]

I don't think the 29 will work unless you reroute the harness in the fender well.

[PRAY]

Originally Posted by laynlo15

I don't think the 29 will work unless you reroute the harness in the fender well.

I would think so depending on how narrow it is and what the backspacing is. I am sticking with the 28's.

[mustangcrusher1]

Originally Posted by Snowblind

I'll be interested to see how it works for someone else with a 305/35/20, good luck.



I am DR and skinny now, Roto CAI, seats out and Vitesse (mod?). No tune and all 4 cats still on.

did the Vitesse help you any at the track?