Proace4

I am sure they aren't letting it fully eat in the tune. But, regardless he took a manual car on 18" drag radials and went 8's... If/when (not sure if he has) he switches to a 15" setup, we shall see just how much he drops et wise.... With or without Mr. Shorts expertise. While talking to them, either he or Jared(I think it may have been Jared) mentioned that I would do better on a 315 rather than the 335. That he has seen better contact on the 315 than the 335's due to tire/wheel sizes. I have quite a bit pulled out down low in my tune as well to try and establish traction... Lastly, I wasn't debating on if a 15" setup would be better, just offering my take for a roll racing tire that fits on an 18" wheel.

LSOHOLIC

Right on.....that group of guys are very sharp (Eric, Jared, James and Brian). When they talk I listen, they have a lot of experience and knowledge to share....when their willing to share it....LOL.

And I was not trying to say anybody was right or wrong.....just what works for me and the guys I run with. I run a 325/50-15 MT DR on the street but a 26"x8.5" slick at the track. To different worlds.....and my car would obviously and definitely slow down at the track with that 325 on it (I don't make enough HP). But...on the flip side, I would annihilate the 26" in a traction limited environment. (Hey, while were on the topic of traction limited, you going to be at the NO PREP RACE in Wichita on May 10th ??)

Here is a pic when I was fitting an old left over set of Prostars from my Chevy II.





This is my last who rah on this subject..........

I look at it like this, a "wider" tire has an advantage in a horizontal traction limited environment (cornering) and a "taller" tire has an advantage in a vertical traction limited environment (straight line). Think of coefficient of friction and which way the tire is being stressed during these operations.

26" tire has 82" of rollout
28" tire has 88" of rollout
So a difference of 6" more rollout with the 28" tire.

Speaking of straight line performance, the taller tire has a larger contact patch on the ground at all times. Because in the real world the circle that is our tire....is not perfectly round, because of vehicle weight and air pressure in the tire.

Example; So if both tires have 20 psi in them and have the same weight vehicle pushing down on them, the "taller" tire has a larger foot print at any given time. Next is the available rubber per revolution.....so if a 26" tire has 82" of rubber per rev before it gets back to the "used" rubber again and a 28" has 88" before it gets back to the "used" rubber.....which tire stands a better chance at maintaining traction ?? The more that tire makes contact with the surface (revolutions), the more its wearing away it traction potential. So if you have an extra 6" of rubber per rev it stands a better chance of maintaining traction.

Think of holding a flat piece of rubber 10" wide 2" long in your hand and dragging in on the ground with pressure from your body weight for an hour in a straight line. Not take a 10" wide 8" long piece (6" more rollout) and drag it for the same time with the same pressure. Which one is going to lose in coefficient of friction first ?? That is what more rollout does per rev, it allows the tire to maintain traction longer because of the "extra" rubber per rev. The longer the contact patch is, the more gradually break away occurs. If you shorten the contact patch, the break away occurs more abruptly.

Now combine the larger footprint with the larger rollout (6" of extra rubber) plus a larger sidewall......and its a no-brainer as to why the "taller" tire wins.

Plus on cars like late model vettes, a larger sidewall plays a bigger role than usual. Because of "our" lack of rear suspension, the sidewall helpes tremendously with absorbing shock and maintaining traction because our rear suspension are so ridged.

Hoped I explained it well enough....lol.



Thanks......

.

Proace4

No I agree that a 28" tall tire is perfect/ideal for traction and for sure in combo's setup tp optimize it. They kill my cars top end to the tune of 10-12 mph, but my 1/8th mile and 60ft pick up a few tenths easy. And they absorb so much off the hit, it may be a reason I haven't broken anything yet.

But in my setup, RPM is power for me. The quicker I can get through it, the quicker the car is. To an extent. I have pondered switching to a 3.73 rear gear and running 28's before.



My dig racing setup, patiently awaiting funds to purchase the fronts to complete the setup. 28x10x17 hoosiers. Dead hook but balloon on the big end and rub slightly and kill mph because of gearing.

I will probably attend the no prep but I won't drag my pile out there. It's no 1/8th mile car for sure.

Hanging out with them, bruce(fartpipe) and dustin(belack porting(big thanks for the badass intake btw)) gave me a lot of pointers and tips. Jared made a few good points about 18" drag radials and after these 335's have been used up, I plan to switch back to a 315. Save weight and supposed to work better.

dprescott878

Great information in this thread. Maybe someone can help me out. I have a 06 Z-51 M6 that puts down around 750/680. I don't run the 1/4 (stock trans and rear still) but do enjoy the 1/2 mile events. Last years Houston Half Mile I ran on 345/35/19 NT05r's at 20-22 psi and traction and had major traction issues until 3rd. I recently picked up some Weld RTS (17x4 and 17x11) w/ MT ET Street's (315/35/17). I noticed the MT ET Streets are a much shorter tire than the NT05r's and they don't seem to "fill" the rear fender wells at all. I am contemplating buying the taller M&H 325/45/17's. Which rear tire would be better for the 1/2 mile events (not timed/trap speed only). I am running the stock 3.42's, any info will be greatly appreciated.

LSOHOLIC

When you have a defined "finish" you need to gear your car for the stripe. In a situation like mile racing, where the surface is largely unpreped......so maximum rollout is desirable. ...but unfortunately our cars do not have unlimited gear options.

In a perfect world you would run the tallest tire you could fit, then gear it for the stripe. But with a gear limited car, its a little more tricky. With your current MT 345/50-18 what rpm (in 4th gear) are you going through the stripe at ??


345/35-18 = 86" of rollout and roughly 27.8" in height, with a 4.9" sidewall.
325/45-17 = 88" of rollout and roughly 28" in height, with a 5.5" sidewall.

Need rpm info to base your decision on....

Good luck with your project.....

dprescott878

I haven't ran it with the 17" MT's yet, with the 345/35/19 NT05Rs I was well into fifth before the 1/2 but I'm guessing that's due to the spinning in first and second. I assume that with the shorter diameter tires (315/35/17 MT's) I would be shifting into fifth sooner, although its hard to gauge due to the fact with the taller tire setup I previously ran spun so bad.

I think I will probably sale the MT's (less than 100 miles if anyone interested) and order the taller M&H's.

LS7 BUD

Actually Jared was on a 17" Hoosier drag radial... 315/35/17 25.6" tall...

Proace4

Ya man. That's probably why he recommended the 315. But I was referring to Eric when I said the 18's. Could be wrong on his though. Both are hauling the mail though on lower profile tires.

Nino S

I run a M&H drag radial 345-35-18, 27.5 inches tall and came from a 335/30/19 and I am happy with the taller tire. I am all motor making 560 rwhp and lost a little up top but have awesome traction in 1st and 2nd. I love 40 mph rolls and I am able to start in the top of 1st gear and it usually dead hooks. I have a pro charger P1 kit sitting in my garage to put on so I think it will be great when it is making around 700 rwhp on the 345/35/18 tire too.

LS7 BUD

Eric was on a 17" too... Same one as Jared...

Proace4

Ahh thanks! I guess we talked widths and I never questioned the diameter lol.

PRE-Z06

What did you trap and what's your rev limiter/rear end gear? The NT05R is a 345/30r19 and I've had it hook in 2nd with a ~700rw+ TT C6t though it was a non Z51 trans. Regardless with stock 3.42 gears you can hit 160s in 4th which I imagine where you should be in a half mile race, as winters97gt did 171.5 @800rw+ bouncing off the limiter right before the traps on a 295/45r17 which is about a 1/4" taller than the tire you ran.

dprescott878

My best trap was around 160 flat. I was having to shift into fifth a few hundred feet before the 1/2, which I know killed my mph, shifting around 6200-6300 rpm's. Still stock 3.42's.

Had to "feather" the throttle in first and second or I would spin bad.

The MT ET Streets (315/35/17) hook much better on the street, but being a shorter tire, I'm thinking it might negatively effect my trap speed in the 1/2. That's why I'm wondering if I should switch to the taller M&H's.

Appreciate the info.

LSOHOLIC

Ok..........have a couple of questions for ya...

First of all, Nitto NTO5R in a 345 is a 30 aspect ratio. There is no 35....??

So can I assume you are/were running a 345/30-19 ??

Second, what kind of power are we talking ?? And what is the power adder ??

Third, at what rpm are you making peak hp at ??


Thanks..........

LSOHOLIC

Nitto NTO5R 345/30-19 = 27.36", 4.18" sidewall, 13.43" section width.
M&H drag radial 325/45-17 = 28.30", 5.65" sidewall, 12.60" section width.

Couple things you may already know but will go over.

About your manual M6 trans.....
1st gear 2.66
2nd gear 1.78
3rd gear 1.30
4th gear 1.0

So, in order to help predict rpm drops and ultimately mph expectations you need to break down the shift points.

The math is very straight forward are what its tells you is the inter-gear ratio.
Take your 1st gear ratio and divide it by the second gear ratio.
2.66/1.78 = 1.494
Now divide by the rpm at which you shift, you said you shifted at 6300rpm so.........
6300/1.494 = 4216rpm
This is the rpm at which you would drop to into second gear (this does not take wheel spin or clutch slip into the equation).

The reason I bring this up is, shift recovery in a manual is important. And without looking at your dyno graph its hard to say whether or not its correct.

So, shifting at 6300 in each gear looks like this (with 345/30-19 and 3.42's).
1st to 2nd rpm = 4216rpm @ 56mph
2nd to 3rd rpm = 4601rpm @ 84mph
3rd to 4th rpm = 4846rpm @ 114mph
4th @ 6300 rpm = 149mph

Using the same shift rpm points but going to a 325/45-17 and 3.42's looks like this.
1st to 2nd rpm = 4216rpm @ 59mph
2nd to 3rd rpm = 4601rpm @ 88mph
3rd to 4th rpm = 4846 @ 120mph
4th @ 6300 rpm = 156mph

I do not know your combo, but you may be selling your self short on the shift points (rpm).

dprescott878

Yes, 345/30/19. My setup is a LS2 stroker motor, w/ LS3 heads and intake, small comp cam, full exhaust, ECS 1500 kit w/meth. Made 746/678 on a dynojet, peak power at around 6300 rpm's. I am shooting for 165 mph in the 1/2 and was hoping with a better wheel/tire setup and traction I can reach that goal, although it looks like ill have to shift into fifth even with the taller M&H's, which really hurts the trap speed.

Greatly appreciate all the info.

LSOHOLIC

Are you familiar with the theory of average power ??

If your peak hp is 6300rpm, I would not shift there....your leaving hp on the table by shifting at peak hp as well as mph because of rpm drop.
Do you have a dyno graph or more preferably a dyno chart that plots it in a numerical column format ??

.

dprescott878

Here is the dyno sheet. I am fairly new to this and am not that knowledgeable. I have my local shop do all the install and tune work. Thanks.
[URL=http://s288.photobucket.com/user/dprescott878/media/VetteDynoNew_zps4e877248.jpg.html]

Edit: Here is a link, embedding didnt work.
http://i288.photobucket.com/albums/ll166/dprescott878/VetteDynoNew_zps4e877248.jpg

LSOHOLIC

lol.....yeah, can be tricky...lol

I was able to copy and paste the link, but it is hard to make out.

But.....the idea is that average power is quick because there is more power in the usable rpm range down the "track". So instead of guessing on a average power shift point, there is a way to get very close.
Again, its very straight forward math. At each rpm point you add the tq and hp then divide by 2. And continue to plot your power through out the curve. This will show you where the best place to shift is, based on available power and rpm drop per gear.

Here is an example of what I'm talking about. I tried to find a graph that was similar to yours. I'm going to start at 4500rpm and work my way up.
The bolded number represents average power.
4500rpm = 580tq + 500hp = 1080/2 = 540
4600rpm = 585tq + 510hp = 1095/2 = 547.5
4700rpm = 595tq + 515hp = 1110/2 = 555
4800rpm = 600tp + 550hp = 1150/2 = 575
4900rpm = 600tq + 565hp = 1165/2 = 582.5
5000rpm = 615tq + 580hp = 1195/2 = 597.5
5100rpm = 625tq + 600hp = 1225/2 = 612.5
5200rpm = 630tq + 625hp = 1255/2 = 627.5
5300rpm = 640tq + 645hp = 1285/2 = 642.5
5400rpm = 650tq + 660hp = 1310/2 = 655.0
5500rpm = 645tq + 675hp = 1320/2 = 660.0
5600rpm = 645tq + 680hp = 1325/2 = 662.5
5700rpm = 645tq + 700hp = 1345/2 = 672.5
5800rpm = 645tq + 710hp = 1355/2 = 677.5
5900rpm = 650tq + 730hp = 1380/2 = 690.0
6000rpm = 645tq + 740hp = 1385/2 = 692.5
6100rpm = 640tq + 745hp = 1385/2 = 692.5
6200rpm = 635tq + 760hp = 1395/2 = 697.5
6300rpm = 630tq + 760hp = 1390/2 = 695
6400rpm = 620tq + 760hp = 1380/2 = 690
6500rpm = 615tq + 755hp = 1370/2 = 685
6600rpm = 605tq + 745hp = 1350/2 = 675
6700rpm = 590tq + 740hp = 1330/2 = 665





Now this is where your rpm drop and shift points come into play. In the M6 trans the 1-2 shift has a ratio of 1.494 and as you shift higher in the rpm the drop becomes a little greater. So, in the example above...if you shifted at 6700rpm you would drop back to 4484rpm. So, as you can see...the dyno was not pulled far enough to seek the best shift point based on the graph.
Meaning, when you shifted at 6700 (665hp average) it drops you back to basically 4500 (540hp average) which is not the "best" average hp shift point.

Ideally, your shift rpm and your drop back rpm would have the same average power. Like in the dyno graph example above.....if it was pulled further the average would have continue to drop off. Lets say they pulled it to 7100rpm and the power average there was 555hp. So, 2.66/1.78 = 1.494/7100 = 4752rpm.
And what do you know...the average power there is also 555hp. So, from 4750 to 7100.... (remember, this is just an example, if they would have pulled it further on the dyno) there is more average power in the curve than anywhere else with the 1-2 rpm drop (2350 total rpm drop).

******NOTE***** JUST BECAUSE YOUR POWER IS "UP" THERE DOES NOT MEAN YOUR ENGINE CAN SWING THOSE RPM'S. TREAD WITH CAUTION.......VALVE TRAINS AND ROD BOLTS WILL HATE YOU.


.
Here is just an example of "average" power and how its quicker. See how there is more power per rpm drop, if you shifted this example at peak hp (6000rpm) you would have less average power in the usable rpm range

Milan

Right click....save as. Good **** in this thread