Launching Twin Screw / IRS car on 2-step (full boost)

[Avenger]

Hey there,

Currently installing a bunch of mods and wanted your input on the situation. I will be running a 2.3 Whipple @ 21psi on race tune. Car is still running the IRS with the following...

- RAM Street dual disc clutch
- BilletFlow brace
- MM urethane subframe bushings
- MM aluminium diff bushing kit
- PST carbon fiber driveshaft (supposed to minimize drivetrain shock as it twists under launch)
- Stock shocks / springs / half-shafts

I'm also installing a N2MB WOT Box and was hoping to launch the car on the 2-step at full boost (yeah, I know... carrying a spare half-shaft ). I just bought a set of Bogarts D10 and I'm seriously wondering what tire to run. I wanna stick with a 26" tire as I won't be running out of 4th gear with that setup (still full weight). Choices are (please chime in if I'm missing something)

- MT 26 x 11.5 x 16 ET Streets
- M&H Racemaster 26 x 12 x 16 slick

I'm thinking the 12" slick will provide better traction but might actually be TOO wide for a 10" wheel. What are your thoughts on tire choice and my plan in general ? Has anyone actually used the N2MB WOT Box at the track ? I've heard great things about the no-lift shift feature but has anyone actually managed to leave the line at full boost with a similar setup ?

Thanks for your input ! :beer:

Alex

 

[rw95gt]

you need to find out how wide they really are. im running the 26/11.5/16 et streets and they are only 9" or so wide. i don't think the 26/12/16 will be to wide.

 

[Avenger]

Looks like the tread is 12" wide.

http://www.mandhtires.com/store.php?crn=71&rn=348&action=show_detail

 

[IronTerp]

Nice setup! I'm now running 28" Hoosier full slicks on my D-10's and have had some decent success. Going through the traps at 6,000+, although I do have a set of 3.73's sitting on the bench ready for install. The 28" height with the wider sidewall will also help to absorb a little more of the shock fromthe launch which could potentially protect your stock half shafts a little more as well. Ran the ET Streets for awhile and they were decent as well.

Slick tire widths don't seem to affect traction with Terminators as much as other cars. I see you've run the QTP's in the past. Darn good tire as well.

Here's your choices in 16". If you have the luxury of runing a full slick, they will usually have a bit of an advantage over a DOT slick.

Rear Tire Slick Options - 16" Rims:
Hoosier Full Slick...................28.0/10.0-16
Hoosier QTP.........................26 X 9.50-16 LT
.........................................28 X 11.50-16 LT
MT ET Drags........................None
MT ET Streets.....................26X10.50-16LT
........................................26X11.50-16LT
........................................28X11.50-16LT
M & H Racemaster-Full..........26 x 12-16
M & H Racemaster-Cheater....26 x 12-16

 

[rw95gt]

i just measured my et streets. the tread width is 9.75". they hook very good imo. i will go with a 28" tall tire when i finish off these. for the power you will be making i would go with a 28" tire.

 

[rtusnake]

How hard does your clutch hit the tires? If its any aggressive clutch, you can kiss the halfshafts goodbye if they tires hook. I broke 4 halfshafts after putting in a spec stage 5, leaving on my msd 2 step

 

[IronTerp]

How hard does your clutch hit the tires? If its any aggressive clutch, you can kiss the halfshafts goodbye if they tires hook. I broke 4 halfshafts after putting in a spec stage 5, leaving on my msd 2 step

What kind of tires were you running?

 

[rtusnake]

28x10.5x15 et drags. I ran slicks for two years with a spec 3+ and never broke a halfshaft

 

[IronTerp]

28x10.5x15 et drags. I ran slicks for two years with a spec 3+ and never broke a halfshaft

Interesting. So that Spec 5 was the difference. Steel flywheel I presume?

 

[Avenger]

Actually, that clutch is really smooth, that's one of the strong point of a twin disc. You could drive my car on the street and think it's the OEM clutch. Still debating 26" or 28" tire...

I like the 3.55 gear and think it's great for the street. I have no intentions of switching to a 3.73 and really want to get the most out of that setup. Wouldn't a 28" tire put me out of the powerband on the bottom half ?

 

[rtusnake]

Interesting. So that Spec 5 was the difference. Steel flywheel I presume?

Fidinza aluminum

 

[rtusnake]

Actually, that clutch is really smooth, that's one of the strong point of a twin disc. You could drive my car on the street and think it's the OEM clutch. Still debating 26" or 28" tire...

I like the 3.55 gear and think it's great for the street. I have no intentions of switching to a 3.73 and really want to get the most out of that setup. Wouldn't a 28" tire put me out of the powerband on the bottom half ?

26" tire will be alittle easier on the drivetrain as well

 

[04spinbra]

28x10.5x15 et drags. I ran slicks for two years with a spec 3+ and never broke a halfshaft

i have the spec 3+ what are you launching at and are you dumping the clutch or slipping??thanks

 

[rw95gt]

this is interesting. i would think the larger tire would protect your drivetrain not the smaller tire. the larger tire will add more cushion. i don't think the 28" tire will hurt your low end power. it should help you get out of the hole better. do they make any 27" tall tires?

 

[IronTerp]

this is interesting. i would think the larger tire would protect your drivetrain not the smaller tire. the larger tire will add more cushion. i don't think the 28" tire will hurt your low end power. it should help you get out of the hole better. do they make any 27" tall tires?

This was always my understanding as well. However since they do reduce effective rear gear ratio, they would decrease torque multiplication and thus may not be quite equal to a shorter tire getting out of the hole. Unless, the actual rear gear ratio was changed to compensate.

M & H makes 27" full slicks in 15" diameter, and I also believe there is a ET Street offering here, but don't know of any in 16".........

 

[rtusnake]

i have the spec 3+ what are you launching at and are you dumping the clutch or slipping??thanks

I was leaving at 5500 on the two step. I'm sure it was slipping some protecting the shafts. I would preload the drivetrain then just dump it. Low 1.5s

This was always my understanding as well. However since they do reduce effective rear gear ratio, they would decrease torque multiplication and thus may not be quite equal to a shorter tire getting out of the hole. Unless, the actual rear gear ratio was changed to compensate.

M & H makes 27" full slicks in 15" diameter, and I also believe there is a ET Street offering here, but don't know of any in 16".........

Thats what I was getting at with the smaller tire. With the heavy car, tall tires and 3.55's takes alot to turn over the bigger 28" tire putting more strain on the driveline

 

[BlckBox04]

if its a mcleod twin disc dont expect it to last long....

 

[Posi]

Thats what I was getting at with the smaller tire. With the heavy car, tall tires and 3.55's takes alot to turn over the bigger 28" tire putting more strain on the driveline

It might be more strain but it's absorbing more than it's putting out. The sidewall is working in the favor of the car. Plus we make plenty of torque to get out of the hole. (just don't look at my car as an example)

IMHO

26's= more SHOCK to the drivetrain

28's= Not near the shock because of the sidewall wrinkling more.

 

[Posi]

OP go with a 28" tire and don't look back. I just went through what you are thinking about doing and in the end the car if it is setup remotely close the 28's won't hurt you. Nor hopefully break anything.

Plus you're going to be launching at instant full boost so that will help get the initial hit or forward movement going as well. I got a WOT Box and can't wait to try it out either.

Good luck.

 

[Avenger]

posi, what kind of 60ft did you manage to pull out of those 28" tires ? The guy I'm buying the D10 from has cut consistent 1.5X with 26 x 11.5 x 16 ET Streets with diff brace and urethane bushings throughout the suspension. No offense to anyone but if I end up running low 1.6X on the new setup, I'll be pissed...