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Car is getting slower in 1/4

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Old 06-27-2011, 07:44 AM   #21
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Do not run drag radials on your IRS! If anything find an extra 2 v6 wheels and throw some slicks on them if you want to run. IRS+DR's=broken half shafts every time.

Back to the issue at hand. I think its all in the 60' and the spinning after shifts thats hurting you. Spinning will add MPH but hurt ET. Its been proven many times. Also, clutch slipping is probably the reason for the slower 60'. Plus tires could have been "newer" and bit better back 2 years ago. Overall, I think your car is still performing the same, just the clutch might have seen its better days and the tires might not be as grippy as they were. Track prep too is also a concern to check into.
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Originally Posted by PurpleIcedGT View Post
Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".
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Old 06-27-2011, 10:43 AM   #22
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Teej....why is it okay to run slicks but not drag radials?
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Old 06-27-2011, 10:48 AM   #23
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Radial means stiffer sidewall than a slick. Running full slicks give you the soft sidewall to absorb the shock of a launch. Drag radials stick great, but they have a radial sidewall which is still stiff and shocks the halfshafts hard on a launch, contributing to their failure.
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Originally Posted by PurpleIcedGT View Post
Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".
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Old 06-27-2011, 11:00 AM   #24
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Slicks will kill irs halfshafts fast as well, i got 3 terminators drivers berween 470 and 520 and a tow truck driver to attest to it.
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Old 06-27-2011, 11:05 AM   #25
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Well if there is an issue with the half shaft before putting the slicks on it will break. But you'll have less chance breaking with a slick.
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Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".
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Old 06-27-2011, 11:25 AM   #26
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Originally Posted by teej281 View Post
Well if there is an issue with the half shaft before putting the slicks on it will break. But you'll have less chance breaking with a slick.
May be less chance but it still a good chance of failure regardless especially with high hp. A 400 hp car with irs has the same axle failure rate as a 500rwhp car woth a 28 spline SRA, both woth equivent tires
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Old 06-27-2011, 11:32 AM   #27
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There are guys running 9's on stock half shafts with 700rwhp on slicks...
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Originally Posted by PurpleIcedGT View Post
Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".
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Old 06-27-2011, 11:37 AM   #28
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Another thing that makes me further disagree about this slap a slick on and go theorybis that for car under 300 wheel HP a full blown rinkle wall slick is probably to much tire forthe power level which means your reall gonna have to come off the line hard and high in the rpm range so u dont bog it out which honestly maybe more stress than coming off the softer with a drag radial. I mean if you think ur gonna put a slick on a 260rwhp and come off the line at 2500 you got another thing coming.
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Old 06-27-2011, 11:39 AM   #29
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Originally Posted by teej281 View Post
There are guys running 9's on stock half shafts with 700rwhp on slicks...
Im sure there is, i can also read on the internet people running 9s on a horrible stock chevy 10 bolt. My 3 examples are from first hand expereince of friends cars at the track not what some guy managed to get away with on the internet, just saying. I think your JDM roots are showing a little Teej dont take offense.
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Old 06-27-2011, 11:59 AM   #30
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There are guys running 9's on stock half shafts with 700rwhp on slicks...
yeah...but if they are running autos that absorbs some of the shock as well.
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Old 06-27-2011, 12:22 PM   #31
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Sidewalk shock absorption makes sense.

I left the line @ 5k on dr's. Just sayin

I doubt he will break an axle. The cobra IRS come with a 28 or 31 spline axle?
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Old 06-27-2011, 12:36 PM   #32
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Sidewalk shock absorption makes sense.

I left the line @ 5k on dr's. Just sayin

I doubt he will break an axle. The cobra IRS come with a 28 or 31 spline axle?
99-02 came with 28 spline, not sure about Rs, and Termis have 31 spline.
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Old 06-27-2011, 12:58 PM   #33
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Hitting an IRS with a launch on a slick is like launching an IRS car with an auto in it. There is not a hard shock like there would be a drag radial.

Roots in JDM has nothing to do with this at all. Just because the example I gave is off of SVTP, and from a well known, well respected member, doesnt discredit it whatsoever. I have plenty of friends that run slicks on their IRS cars with stock shafts and they have no issues at all.

But just because your friends snap their shafts and mine dont really doesnt give any info towards whether its going to hurt or help. Just gives some examples of what can happen. There is no use us arguing about this because we both know that the other side is not going to give up on their argument. So I'm just going to agree to disagree.

But I will say this...I was not thinking about softer launching. I figured if he wanted to come off as hard as possible, slicks without a doubt. But soft launching and just trying to manage spin, drag radials will work fine.

Also, as far as splines go, 99 had 28 spline inner and 28 spline hubs. 01's had 28 spline inners and 31 spline hubs, 03/04 had 31 spline inner and hubs.

And turbo232, the guy is running stock 6 speed and stock IRS minus the bushings and shock/spring setup that ran in the 9's.
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Originally Posted by PurpleIcedGT View Post
Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".

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Old 06-27-2011, 01:05 PM   #34
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Yes there will be no end to the argument (PS your friend I met with the terminator was swapping his IRS for a solid....lol), moving on. Teej did you even run your mustang at the track? This way you can have a comparision to whether or not the slick is to much tire to be beneficial with your setup because thats gonna be the next trial to wether or not its going to be worth it and this I am curious to because I don't know anyone running a slick on an IRS other than 400rwhp cobras.
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Old 06-27-2011, 01:58 PM   #35
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I would definately agree with Uber, although the sidewall does absorb some of that shock, the extra traction from a slick far outweighs that. An auto car could have much more horsepower but it is a relatively less violent launch than a stick car. And also depends a lot on the clutch in the 5 spd cars, a stock clutch will slip quite a bit on launch and lessen the driveline shock. A modified higher performance car is likely to have a heavier duty clutch that does not slip.

Just my thoughts, not trying to continue the argument.
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Old 06-27-2011, 01:59 PM   #36
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I say uberstang wins the argument because he managed to use a sentence with 61 words in it.

Seriously though, there are many varaibles that can effect how much stress a half shaft is expopsed to. OP's situation is probably not going to break a half shaft either way. It sounds to me like he would still be prefectly fine to run some ET Streets, but that is up to him to decide.

If I were OP, I would try to borrow a set of DRs for a pass or two. Then he'll see how much difference they make for him, and he can then decide what he wants to do from there.
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Old 06-27-2011, 02:29 PM   #37
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Quote:
Originally Posted by teej281 View Post
Do not run drag radials on your IRS! If anything find an extra 2 v6 wheels and throw some slicks on them if you want to run. IRS+DR's=broken half shafts every time.

Back to the issue at hand. I think its all in the 60' and the spinning after shifts thats hurting you. Spinning will add MPH but hurt ET. Its been proven many times. Also, clutch slipping is probably the reason for the slower 60'. Plus tires could have been "newer" and bit better back 2 years ago. Overall, I think your car is still performing the same, just the clutch might have seen its better days and the tires might not be as grippy as they were. Track prep too is also a concern to check into.
The bold portions is the part that really has be debating the statement, per say a 28x1150 ET street drag radial will break a half shaft everytime, but then saying a 28x1150 ET drag slick is perfecty fine is kind of a stretch. Even the big sidewall dragradial will have some cusion in it, but the shock absorbition from the slick isnt great enough to say its safe to run, I can see your point about absorbing some shock but its not absorbing THAT much, plus youll have to launch that slick higher in the RPM range compared to the drag radial and you would think high RPM=more power band= more stress even with the extra cusioning effect compared to lower rpm=lower power band= less sidewall cusion. I just can't see the theory.
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Old 06-27-2011, 02:36 PM   #38
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Yes there will be no end to the argument (PS your friend I met with the terminator was swapping his IRS for a solid....lol), moving on. Teej did you even run your mustang at the track? This way you can have a comparision to whether or not the slick is to much tire to be beneficial with your setup because thats gonna be the next trial to wether or not its going to be worth it and this I am curious to because I don't know anyone running a slick on an IRS other than 400rwhp cobras.
That car has never seen traction before 3rd gear in its life. Never even seen drag radials. Most of my friends that drive mustangs are actually cobra owners. Some solid axle and some IRS. I'm probably going to be grabbing some 4.10's and a 28x10.5x17 Hoosier QTP's to run at the drag strip, and a Centerforce DF clutch sometime in the future. Then we'll see what a 230rwhp car with 4.10's and an IRS on slicks will do...that weighs 4000lbs. lol

And to address the most recent comment, its the initial shock that the slick helps tremendously with. The immediate shock that the drag radial would absorb, seeing that its a radial construction, will snap back, which is what causes the snapping of the halfshaft. Now when you step up to the slick it does not snap back and absorbs a lot off the energy of the hard launch.
But I have not run my car at the track. Hope to either get an IRS brace or diff cover as I have a slight leak from the current stock cover. One step at a time.
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Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".

Last edited by teej281; 06-27-2011 at 02:40 PM.
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Old 06-27-2011, 02:46 PM   #39
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That car has never seen traction before 3rd gear in its life. Never even seen drag radials. Most of my friends that drive mustangs are actually cobra owners. Some solid axle and some IRS. I'm probably going to be grabbing some 4.10's and a 28x10.5x17 Hoosier QTP's to run at the drag strip, and a Centerforce DF clutch sometime in the future. Then we'll see what a 230rwhp car with 4.10's and an IRS on slicks will do...that weighs 4000lbs. lol

And to address the most recent comment, its the initial shock that the slick helps tremendously with. The immediate shock that the drag radial would absorb, seeing that its a radial construction, will snap back, which is what causes the snapping of the halfshaft. Now when you step up to the slick it does not snap back and absorbs a lot off the energy of the hard launch.
But I have not run my car at the track. Hope to either get an IRS brace or diff cover as I have a slight leak from the current stock cover. One step at a time.
Or the heated super sticky slick wheel hops on the IRS and its game over half shaft. Teej I'm really not trying to bust your ***** on this but for NEVER running your car at the drag strip you really seem to be sure how its going to react and keep trying to talk how the IRS with the slick is gonna work at the track, just alot of talk when you never even had the IRS on the track with a street tire or a DR. As far as the car never seeing traction before 3rd gear.......the street and a prepped track cannot even be remotley compared in any way shape or form. I truly think a 28 inch slick on top of a prepped track is going to be way to much for the combination of your power level and a little to much stress on factory clutch.
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Old 06-27-2011, 02:56 PM   #40
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Or the heated super sticky slick wheel hops on the IRS and its game over half shaft. Teej I'm really not trying to bust your ***** on this but for NEVER running your car at the drag strip you really seem to be sure how its going to react and keep trying to talk how the IRS with the slick is gonna work at the track, just alot of talk when you never even had the IRS on the track with a street tire or a DR. As far as the car never seeing traction before 3rd gear.......the street and a prepped track cannot even be remotley compared in any way shape or form.
We took Ian's car to the track last year and he couldnt get traction until 3rd gear man. Street just lights them up, at the track it hopped on street tires. Also, if youre hopping on slicks at the track, you need to adjust your setup. Reading and research does not make my arguement any less credible. I've studied multiple cars, followed progress, and have seen many setups work and not work. Thats like saying I know e=mc^2, but since I am not a physics major and practice with it daily, that its not true. I mean you have results first hand of 3 cars. I've read up and followed at least a dozen or more IRS cobras running slicks at the track. Research is reporting what others have found.

There is plenty of info over on SVTP on slicks versus drag radials and all of the tire and suspension guru's will agree with me that on an IRS car, slicks offer less chance of breakage and harder launches.
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Saying there is a 1whp difference between the X and H and trying to justify it as a performance difference, is like walking 100 feet to your car and eating a cheeseburger while saying its fine because you just did "cardio".
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