advice on launching with IRS and MT DR's

RAPER

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First off, please don't post any comments on getting rid of the IRS and putting in a sold.

went to the byron dragway today and sat most of the day. I only got in 3 runs and didn't fair so well in the 60ft department. I just put in a new diff and I've never actually had the ability to launch the car properly since I've owned it (bought the car with a bad diff apparently). Anyways I'm asking what you guys are launching at so next time I will have better luck.

I have an auburn hd diff with the stock 3.55 in the rear. I replaced all the irs subframe bushings with the MM uerathane bushings as well as the pumpking mounting bushings. I also have a billetflow irs brace on.. I am running the stock halfshafts.

I'm was running 20psi of air in my DR's and they are 275 45 17 Micky Street radials
the best i got was a 1.97 60ftr with a 4k launch which I still bogged out of the hole. If I had more time and could of gotten in more runs I'm sure I would of improved on that, but the same time I seen a fellow brother break a halfshaft prior to that run which discouraged me from getting crazy out there.

Any advice for next time would be appreciated.
 

blck10th

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what clutch? if you have a stocker when I did you can slip it out pretty hard.

I now have a DFX and IRS. i went to slicks. m/t radials would kill my half shafts.

i only ran 14 psi. in the 275 M/T's

also do you have air bags?
 

Wiked03

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First off, please don't post any comments on getting rid of the IRS and putting in a sold.

went to the byron dragway today and sat most of the day. I only got in 3 runs and didn't fair so well in the 60ft department. I just put in a new diff and I've never actually had the ability to launch the car properly since I've owned it (bought the car with a bad diff apparently). Anyways I'm asking what you guys are launching at so next time I will have better luck.

I have an auburn hd diff with the stock 3.55 in the rear. I replaced all the irs subframe bushings with the MM uerathane bushings as well as the pumpking mounting bushings. I also have a billetflow irs brace on.. I am running the stock halfshafts.

I'm was running 20psi of air in my DR's and they are 275 45 17 Micky Street radials
the best i got was a 1.97 60ftr with a 4k launch which I still bogged out of the hole. If I had more time and could of gotten in more runs I'm sure I would of improved on that, but the same time I seen a fellow brother break a halfshaft prior to that run which discouraged me from getting crazy out there.

Any advice for next time would be appreciated.
When I had stock clutch and stock IRS, I was launching at 5500-6200 on 275 MT DRs... 14-16 psi, Straight clutch dump/side step. 60s were in the 1.65-1.75 range

Once you have aftermarket clutch, then game changes a bit.
 

blck10th

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now that I have 28" slicks. I am going to leave @5800.
 

Dana

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First, you are going to break half shafts. That's a fact of life if you have the IRS.
Be happy if you don't break the housing.

Drop the air pressure in the tires and keep raising the launch RPM until it won't hook and then back off a little.

Do not slip the clutch. Slipping creates heat and these clutches will fail if you create very much heat in them.
Just release the clutch quickly when you launch.
 

IZZy

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slipping the shit out of the clutch is the only way to get good 60ft.'s when launchig on drag radials and IRS.

The best 60 I got when launching on that setup was low 1.7's
 

Dana

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slipping the shit out of the clutch is the only way to get good 60ft.'s when launchig on drag radials and IRS.

The best 60 I got when launching on that setup was low 1.7's
Let me say this again:
Slipping creates heat. Heat kills clutches.
It will either cause it to wear out prematurely or weld itself together.
Either result will cause a failure that, at best, could have been avoided or worst case, instant catastrophe.
This is not to say that slipping is never appropriate, but these cars just do not have enough clutch to absorb that much heat and not be affected.

A twin disk may be more suited for this than the single disks that are in there now and that's the way I am going to go the next time around.
 

Flatliner

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I still run my IRS and have good luck in the 1.5/1.6 range with a 16" ET Street, however, the challenge you have is the 17" DR. There isn't much of a sidewall to help absorb some of the shock of launching with the T56. The stock clutch will hold for awhile, but eventually will give out launching hard on a slick. I've broken one shaft and it was right after the DFX went in and I had to adjust my launching style to the clutch and been good since. It can be done on a 17", but expect lot's of frustration.

Personally, I love my MT DR's on the street, never leave home without them... however if you want to get a number at the track and run consistently, then a 26x16" ET street or equivalent on a 16" rim is the answer. Good luck.
 

blck10th

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I still run my IRS and have good luck in the 1.5/1.6 range with a 16" ET Street, however, the challenge you have is the 17" DR. There isn't much of a sidewall to help absorb some of the shock of launching with the T56. The stock clutch will hold for awhile, but eventually will give out launching hard on a slick. I've broken one shaft and it was right after the DFX went in and I had to adjust my launching style to the clutch and been good since. It can be done on a 17", but expect lot's of frustration.

Personally, I love my MT DR's on the street, never leave home without them... however if you want to get a number at the track and run consistently, then a 26x16" ET street or equivalent on a 16" rim is the answer. Good luck.
looking @ my slips from last year. 1.68 was my best. Yes Dana is correct. when I took out the stock clutch it was pretty nasty.


listen to Victor, he has helped me out a lot. i credity most of my first good 60ft. to much of his advice. I have and my first time @the track with my new combo. I was quite pleased.

you best bet is get a set of slicks and it will help you out. they make a 17" slick from Hoosier I believe. get 2 extra rims
 

IZZy

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Let me say this again:
Slipping creates heat. Heat kills clutches.
It will either cause it to wear out prematurely or weld itself together.
Either result will cause a failure that, at best, could have been avoided or worst case, instant catastrophe.
This is not to say that slipping is never appropriate, but these cars just do not have enough clutch to absorb that much heat and not be affected.

A twin disk may be more suited for this than the single disks that are in there now and that's the way I am going to go the next time around.

I totally agree but unless he gets a different set of wheels with 26x10 et streets like victor and jimmy suggested that is the only way to launch the car and get good 60ft's
 

Vobraman

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Dan...lets take your car to the track and test all the theories. we can report back which one's just dont work !!!!:eek:
 

Dana

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Dan...lets take your car to the track and test all the theories. we can report back which one's just dont work !!!!:eek:

Thanks, but I've tested all the parts and theories I am going to test with this car. I know what works and what doesn't now and I'm sticking with that.
But, since I've had a good 4 years on this clutch, maybe next year a twin disk will be in order.

The rest of the time will just be dialing in what I already have. There's another 3 or 4 tenths in there.

BTW, Brian, when are you going to post some of the 800 pictures you took of the white car?
 

gnxs

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First, you are going to break half shafts. That's a fact of life if you have the IRS.
Be happy if you don't break the housing.

Drop the air pressure in the tires and keep raising the launch RPM until it won't hook and then back off a little.

Do not slip the clutch. Slipping creates heat and these clutches will fail if you create very much heat in them.
Just release the clutch quickly when you launch.
I still run my IRS and have good luck in the 1.5/1.6 range with a 16" ET Street, however, the challenge you have is the 17" DR. There isn't much of a sidewall to help absorb some of the shock of launching with the T56. The stock clutch will hold for awhile, but eventually will give out launching hard on a slick. I've broken one shaft and it was right after the DFX went in and I had to adjust my launching style to the clutch and been good since. It can be done on a 17", but expect lot's of frustration.

Personally, I love my MT DR's on the street, never leave home without them... however if you want to get a number at the track and run consistently, then a 26x16" ET street or equivalent on a 16" rim is the answer. Good luck.
:ditto:

You'll likely find the sweet spot for air pressure down to the 14-16 range and you'll need to make sure the drivetrain is loaded up and quickly release (but not just sidestep) the clutch with the DRs. If you "shock" them, you'll have no chance of hooking up.
 
OP
RAPER

RAPER

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most reply's i've ever had for a ? on here. thanks so far guys..

I have an aftermarket fidanza flywheel and fidanza 4.3 clutch.. also have 26 spline input shaft in trans.
 
OP
RAPER

RAPER

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also I don't have airbags and I'm running on 500 inch pound MM coilover springs with upgraded bilstein shocks
 
OP
RAPER

RAPER

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you best bet is get a set of slicks and it will help you out. they make a 17" slick from Hoosier I believe. get 2 extra rims
my DR's are mounted on an xtra set of wheels.. my street tires are 18"
 

Since 1964

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I have had level 1's for a long time, and when I ran all the time I eventually launched from 4500-5500 all the time. The tires...MT Bias Ply ET Streets on factory rims spun 2-3 revolutions, bit and pulled me a consistant 1.7. These motors want to start at the top and just blast through gears.
 

FuelSlut

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First off, please don't post any comments on getting rid of the IRS and putting in a sold.

went to the byron dragway today and sat most of the day. I only got in 3 runs and didn't fair so well in the 60ft department. I just put in a new diff and I've never actually had the ability to launch the car properly since I've owned it (bought the car with a bad diff apparently). Anyways I'm asking what you guys are launching at so next time I will have better luck.

I have an auburn hd diff with the stock 3.55 in the rear. I replaced all the irs subframe bushings with the MM uerathane bushings as well as the pumpking mounting bushings. I also have a billetflow irs brace on.. I am running the stock halfshafts.

I'm was running 20psi of air in my DR's and they are 275 45 17 Micky Street radials
the best i got was a 1.97 60ftr with a 4k launch which I still bogged out of the hole. If I had more time and could of gotten in more runs I'm sure I would of improved on that, but the same time I seen a fellow brother break a halfshaft prior to that run which discouraged me from getting crazy out there.

Any advice for next time would be appreciated.
Sounds like u just need to go back and spend more time launching it. u have the right setup, my only advice is turn down the tire pressure to 15.

On my old setup I was cutting 1.6 60ft and no urithane bushings. Had mt drs @ 15psi.
 
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RAPER

RAPER

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thanks.. I'll try to do just that. Hopefully I get one more crack at the strip before weather turns for the worst.
 

10thSVT_03

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A lot of good reading here... I have the 16" ET Streets and was pondering the same question. I will be at the track the 25th also so I will look for you guys..
 

gnxs

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A lot of good reading here... I have the 16" ET Streets and was pondering the same question. I will be at the track the 25th also so I will look for you guys..
Your setup is much more forgiving on the half-shafts. A smooth, but very rapid clutch release from just about any rpm (start at maybe 5300 or so) should work for you. 12-13 psi to start. Victor has had fairly good success keeping his half-shafts alive with a similar setup to yours.
 

10thSVT_03

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Your setup is much more forgiving on the half-shafts. A smooth, but very rapid clutch release from just about any rpm (start at maybe 5300 or so) should work for you. 12-13 psi to start. Victor has had fairly good success keeping his half-shafts alive with a similar setup to yours.
Thank you MUCH appreciated!
 

blck10th

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Your setup is much more forgiving on the half-shafts. A smooth, but very rapid clutch release from just about any rpm (start at maybe 5300 or so) should work for you. 12-13 psi to start. Victor has had fairly good success keeping his half-shafts alive with a similar setup to yours.
:biggthump.

got me a 1.60. but i have 28" slicks. We shall see what 5800 does on the 25th.
 

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