cbrock

iTrader: (1)

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH HHHHHHHHH. Yes, your equations are correct. Torque is the true power of a vehicle. HP is torque at given RPM. Torque multipliers such as the final gear and transmission do effect torque to wheels. Hence how my 82 olds can push a 2.42 rear with a .69 od and then a lock up TC and still manage to get out of it's own way. You even said it yourself and didn't realise it.

The rotary axle torque is converted to a linear motive force by the tires:

LTF = ATQ / TRADIUS

Your TRADIUS as you stated is the TIRE radius, not the WHEEL radius. Unless you change the height of the sidewall you aren't changing your OVERALL diameter with no change to the *final* gear ratio. When I put rims on my Nissan I kept the stock 15" size but put a tire on it that was 1" shorter than stock. You want to know what I noticed by doing that???? A speedo that was thrown off and 1/2" less ground clearance with no noticable change to 1/4 or 0-60 time. I mean, I'm sure it can't hurt...but it's not night and day by anymeans. Perhaps that's how you run 98 mph, with a 14" wheel. I'm just giving you a hard time on that last shot....but check it out.

use a 205 55 R16 stock T2 wheel/tire size and, by what you're saying, remove 2" from the size. Ok, we now have a 205 55 R14.

Over-all size:
16" 24.8779in
14" 22.8779in

speedo reads 98mph
actual reads 90.1215mph

If you actually removed 2" from the overall height you WOULD accelerate better...you'd also be 1" closer to the ground and have a car that looked like a 4x4 with the monster fender gap you created by losing 1" all the way around.

from this
--O----O-

to

-- o ---- o -

Also by changing the overall gear ratio you sacrifice 1/4 MPH for ET. So your equations are right...but your use of them is wrong. You stated earlier that you didn't change the overall diameter all you changed was the rim size. So according to your equation you didn't change anything. What kind of grades did you get in Dynamics and Mechanics? Hmm, I got an A and a B+.

GLHS

No, what I said was that the sidewall height of the tires themselves are the same, but the overall amount per rotation is 2" more for a 16" rim, vs a 14" rim.

I also didn't calculate the amount of torque loss due to increased weight of the larger tire and larger rim and the increased amount of friction due to the added weight.

cbrock

iTrader: (1)

ok, so you are rolling on 2" less overall height. Odd looking, but ok. So what is your final gear ratio with the help of the smaller wheel/tire combo? BTW, the friction do to the wheel size won't change..the only friction occuring in this system (neglect the friction found in the bearings and such) is due to the road. If you made the tire wider (which you should have done to support the weight of your car on a lower profile tire) you actually increased friction with your setup. Now if you left the width the same, then there is no change. Acceleration due to inertia changes...but once it's up to speed it doesn't really take much more energy to spin it.


I wanna see pics of this car....holy tonka toy looking RX7 batman.

peejay

Same car, same shift points, same day, bad launch vs. good launch.

Of course a different car will have a different MPH/ET correlation... AWD cars or cars with slicks for example will always have better ETs for the same MPH because they do more acceleration at the start of the race. Likewise, FWD cars will always have worse ET for the same MPH because they can't launch for ****.

However, with a good launch, MPH will go UP slightly because the car does more useful acceleration at the start of the run.

GLHS

DimensionTire A: 195/45 R 14 Tire B: 195/45 R 16
65.69" (1668.50mm) 71.97" (1828.09mm)


Effective Gear Ratio Change
Rearend ratio with 195/45 R 14's 4.11
Rearend ratio with 195/45 R 16's 3.75

cbrock

iTrader: (1)

Ok...same day same car....1988 T2

first run: Bog 2.5 sec 60ft...15.2@97
Second Run: Bog 2.5 sec 60ft...14.9@98 (quicker shifting)
Third Run: 2.4 sec 60ft..14.7@98mph

Notice my 60ft's never really changed, thus only a slight change in 1/4...also weather might have changed some too. If I get that down to a 2.0 or 2.1...which should be VERY easy to do (mind you these runs were 3 years ago when the car was my fathers with 25,000 mile on it...didn't exactly wanna spank it off the line). I should see vast improvements. If you like I can take my oldsmobile to the track and experement for you. Oh yeah, it runs a 17.0 @84mph and doesn't even burn a wheel....yet

However, I would bet the farm that if I get off the line faster I'll have 14.0 ish ET at around the same speed if not slightly more. Here's why: I'll be slipping the clutch more not almost stalling. Read: Improved 60ft which will greatly improve 1/4...MPH increase because I'm not rolling down the track @ 500rpm cuz the car almost stalled. How my car will differ from GLHS's is that when I launched like that I had less distance between the car and the traps (not really moving...like a rolling start 5-60mph test in C and D, I had no advantage from being able to vary clutch pressure). In that condensed time frame the car was still able to achieve high trap speeds. In this case it would improve all around. I won't however, be able to provide you with new data seeing as how I'm in the process of putting on a 60-1, fmic, haltech..and all supporting mods. Should be much faster than 14.7@98

However, look at my buddies chevelle...lost a few mph but gained 3 sec. Here's what happened. Stock 66 chevelle. 3.08 open rear diff, first run ever in his life: 17.0@98mph smoking the tire to the 1000ft. Changed to a 4.10 rear and slicks (better 60ft. Went 14.7@91 (he has since done mods hence his best 14.1 posted earlier). Now what changed. He put slicks on the car and a MUCH better rearend. He runs 3 seconds faster but lost MPH. Now we all know a chevelle would be much faster than 17.0 stock...so that's a bad TIRE SMOKING launch. Did he think with a good launch that'd he'd be able to run 13's...nope. He is now that quick cuz of the slicks and the better gear ratio. But his advantage is his 60fts much like the awd cars. Again, John shepards car (awd talon...highly modified )...4 tires spinnin off the line. Fast ET but waaaaaaaaay off trap speeds. His traps are as fast as some open wheel dragsters. His car would never...ever, run in 8's as his mph would suggest. He just ran a 9.66 @147 at the DSM shootout....previous to that I was seeing 9.8 -9.9 @ 150ish. Again, quicker ET but lost MPH. Sean Glazar
went 8.8 in his awd @ 153...damn near as FAST as Shep but 1 sec faster with much more power. Pretty much, the only time 1/4, 60ft and trap speed all improve is with gains in HP or huge weight gains and or car setups (suspension tweaks)

cbrock

iTrader: (1)

Oh yeah, going from a 3.75 effective to a 4.11 isn't going to cause a massive drop in ET, but it will, slightly improve.

GLHS

Again a smaller wheel will allow more torque to be produced to the ground, if the traction is there.

Torque produces acceleration, wheelspin does not.

so if car A runs 15sec, with 14" wheels and car B runs 14s with 16" wheels, but car b doesn't spin at all , but car A spins bad.

Car A will be faster than Car B if Car A has traction, hence the increased amount of torque

GLHS

Show me proof of this.

My friend put 4:11 gears in his mustang which had 3:73 before, and increased the ET by almost 1 full second. Same wheels no other mods.

cbrock

iTrader: (1)

Well sweet then when I change from my 2.42 open to a 3.43 posi, I'll fly. Well, ****..that's 1 full ratio change to your buddies .36 I'll have an advantage 2.8 times what he had...so he dropped 1 sec, so I'll drop 2.8 seconds...**** that's 14.2 sec. I'm sure there were other factors. Weather (huge factor), track conditions, shifting speed/style. But I'm sure you'll say nothing changed. I think impala guys see about 1 sec going from a 3.08 to a 3.73...but they're all auto cars which will allow the car to work better with the stock Torque converter. And please quit saying 14" wheels to 16" wheels...people are going to start selling their T2 mesh wheels for phone dials and not see a difference. <-he changed the overall diameter.

GLHS

matter of fact it is a automatic 4.6L mustang.

again if they did change their rims, they most likey would see quicker times,hence the increase in torque.

I am not rying to get anyone to change thier rims, they would have the same awful wheelspin I get, but worse.

unless they got slicks

cbrock

iTrader: (1)

So we've finally worked our way back to the original question. You'll have happen to you what happened to the chevelle. You have massive wheel spin...same as the chevelle. You put slicks on the car, same as him..and your ET's will drop but so will your MPH. So expect around Mid 14's@umm..lets say 94mph not high 13's @ your original 98 .


NOTE TO ALL T2's...DO NOT..I repeat..DO NOT race 5.0 mustangs rolling around in downtown areas rolling on those 13" reverse offset 110 spokes wheels. Their overall diameter has change greatly and should be 3+ sec faster than stock...no other change.

adamlewis

GLHS, youre too ignorant to live.

You have just found your way on to my ignore list. Thinking that changing tires gets more torque to the ground is about as stupid as trying to use an airpump as a supercharger Please go away before you infect anyone else on the board.

adamlewis

peejay

This is what I mean. You had a bad launch on the first two runs. The third run you launched a little better. On all three cases MPH stayed fairly constant, getting a little higher as ET went lower. That's because MPH is mostly determined by power/weight and power/drag.
Now... We have a special case...

Actually, most Chevelles are 17-second cars or worse. They're heavy and most of them had small-blocks or worse yet straight sixes and they went nowhere. I'll bet his engine didn't make much power beyond 4,000 either.

When he went to 4.11 gears, he was probably going beyond the engine's ability to turn RPM at the top end. It was making noise but no power up there. That's why he had a stellar ET (he could launch hard and pull hard in the first part of the track) but his MPH tanked because he went TOO far with the gearing. Now that he has the gears, he needs to build his engine up to handle that kind of RPM.... or he needs to step down to something like 3.55 gears.

Zach McAfee

Good stuff Peejay. I feel like were in court with all these different cases.

And now for exibit C...

Zach McAfee

Oh, but I'm still on cbrock's side.

cbrock

iTrader: (1)

Ok Peejay...my 82 delta 88 with a 307 and the **** rearend is a 17 sec car. His ran 17's cuz he had no clue as to what he was doing (at the time). I rode in it...it pulls WAAAAAY harder than the olds. BTW the chevelle has a 350 small block chevy with a hot cam, shitty heads (for now) and a 650 double pumper. Putting the new heads that we built up should easily throw it in the 12's. And yes they were heavy cars at about 3700 lbs (about 500lbs lighter than my 17 sec delta). I do agree a straight 6 would be quite the piggy. In most respects the old cars weren't that fast..but that's mainly due to traction. Think about it? The bias plys at the time could only be made so wide (that and a lot of timing was done with a stop watch). No tire, no traction. And you're probably right...it probably does make power at 4000rpm and not much more at his 5500 shift point..but ya know what? His car and my olds probably make more torque at idle than yours will make peak.

Back to my car: My MPH in my car stayed the pretty much the same cuz my launch was the same. I'll do the biggests smoke show you've ever seen off the line and I betcha I'll run a sweet MPH and a super shitty ET. ALso, if all you had to do was switch to a smaller tire don't you think you'd see people like Sheperd, Buschur, RX7.com...etc etc running tiny tires??????? Obviously it doesn't work out and in most cases they switch to a taller tire. A lot of the prostreet cars have like 5.10+ rear ends but a 32+in slick...10 frickin inches taller than GLHS's tires. Perhaps GLHS has such a problem with traction cuz he is still running a 195 tire...**** man...I've seen hockey pucks wider than that.

So please, GLHS and peejay, lay off with the BS and just go out and do it. Buy the slicks..put them on the smallest rim you can find and report the numbers. That's all you have to do. If you run a 13.9 I'll be soooooo happy for you. You do however see why I have my doubts and I've had plenty of real examples to show you. Make sure you bring your street tires to do a comparison run.

As a side note, check 2 issues ago sport compact car. They tested a sticky street tire vs a stock type tire vs a slick...find out what happened. I even believe they went with a slightly shorter slick. I'll tell ya what, they didn't drop from a 15.7 to a 13.9..not even F'in close. Again, please buy the slicks and try them out...the best of luck to you. But don't come bitching to us when it's not as fast as you think. Hopefully, for you, I'll eat my words and you do have a 13 sec N/A....but man....I just don't know about that.

GLHS

I am not concerned about making you eat your words.


I am more concerned about getting my car faster and quicker.


Thanks for the good time, its been a bunch of BS, with no real data.

I still want see a N/A like mine, with the same mods running slicks on the same size wheels and what times they get. Not any other examples thanks. Its just not the same.

cbrock

iTrader: (1)

Ok buddy, you're just too smart for me. I'm out like a boner in sweat pants. Good luck finding someone who runs a skate board sized tire.....you might want to talk to the Jr Dragster people. And I understand how all my comparisons aren't the same....man, what was I thinkin...comparing cars that are trying to accomplish the same thing. Samsonite...I was way off



No real data...ha that's all I provided you. With out actual sensors datalogging everything your car is doing, you'll never get any *answer*...especially the ones you're looking for. Obviously your car is waaaay different then the bazillion other N/A guys with **** loads of mods..so why even listen to them, your car is obviously far superior.

cbrock

iTrader: (1)

Peejay...your knowledge just too much for me. He runs a 28" slick and the 4.10. It could use a little more mph, but it's about right for as quick as he's running. Sigh....can't wait for more useful insite on drag racing from peejay. Oh yeah, we ever gonna race...perhaps you can teach me a thing or two.

GLHS

What are you talking about? Alot of N/A RX7s came with 14 " wheels. Its a very common wheel size.

Its okay to admit that smaller wheels with make you quicker, trust me, its okay. Nobody is gonna hate you for it.


PS: I run 205's on my 14s.

David88vert

http://www.staginglight.com/guide/tires.html
http://www.staginglight.com/guide/react.html
http://www.speedworx.com/cgi-local/s...cs_2_tires.htm
http://www.discounttiredirect.com/fe...agRadials.html
http://www.alternativeauto.com/water...ves/hook1.html


Also good:
http://w3.one.net/~rcheek/impala/misc/drag_race.html

cbrock

iTrader: (1)

Yeah a lot with 14" wheels but not rolling on -2" rubber. Saw this and thought of you.

http://cgi.ebay.com/ebaymotors/ws/eB...tem=1846909423

All awesome sites, I really respect the impala crowd. Also my buddy that has been sitting in on this thread races with the guy that runs stagelight.com...they both race at Quaker City raceway, which is where we'll be this weekend.

lxk199

I personally ran a 15.6 in my TII (stock-shifter is shot, needs replacement), at 93 mph. My room mate is running a 89 GTU (heavy weight redux and exhaust) and he runs a 15.4 at 86 mph. I can't seem to find the reason for this discrepancy...who knows....