Launching (tire psi ???)
+ Reply to Thread
Results 1 to 13 of 13

This is a discussion on Launching (tire psi ???) within the Motorsports Talk forums, part of the Community - Meet other Enthusiasts category; hey guys just a quick ? ... i raced hondas be4 i became a subie owner with my honda tire ...

  1. #1
    Registered User
    Join Date
    Dec 2006
    Posts
    28

    Launching (tire psi ???)

    hey guys just a quick ? ... i raced hondas be4 i became a subie owner with my honda tire psi was low around 15psi (obviously for better tracktion) now i hear w/subies tires should be set high(44-46psi) for a better launch - is that true - please explain, thanks
    Team Boost Effect..
    "Drive It Like Its Stolen"

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Moderator Integra96's Avatar
    Join Date
    Apr 2002
    Location
    Utah
    Posts
    16,989
    I Support ClubWRX
    A little wheelspin when launching can be a good thing; otherwise, it's easier to bog and also harder on the drivetrain when four soft, squishy tires grab the pavement at the same time.
    "Did you sleep well?"
    "No, I made a couple of mistakes."
    -- Steven Wright

  4. #3
    Registered User
    Join Date
    Dec 2006
    Posts
    28
    Quote Originally Posted by Integra96 View Post
    A little wheelspin when launching can be a good thing; otherwise, it's easier to bog and also harder on the drivetrain when four soft, squishy tires grab the pavement at the same time.

    so high tire presure is good - for launching
    Team Boost Effect..
    "Drive It Like Its Stolen"

  5. #4
    Registered User tayhadar1's Avatar
    Join Date
    Apr 2006
    Location
    Spokane, WA
    Posts
    1,509
    Quote Originally Posted by STi07 View Post
    so high tire presure is good - for launching
    In terms of the tranny, yes. Wheelspin is good for all wheel drive trannies as it can result in less shock.
    2004 WRX Sti Cobb Stage 2
    GO COUGS!!!

  6. #5
    Registered User elohdaeh78's Avatar
    Join Date
    Apr 2002
    Location
    Long Valley, NJ
    Posts
    706
    i put 42psi in my tires when i race, but i also have stock RE92s that are almost down to the metal, so with a tire with more grip i would even put more than 42psi.
    2005 WRX (Short throw shifter, lightweight pulley,STI Splitters,Tein H-Tech springs,Up/Down Pipe, ERZ Catback, Cobb Stage 2, ASA JH8 with Yokohama ES 100s) 13.680@100.46mph

  7. #6
    Registered User Orbit's Avatar
    Join Date
    May 2003
    Location
    TdO4 12.4@109
    Posts
    135

    Thumbs down

    I get better traction when I lower my air pressure, but it will give you less wheel spin. just be sure to launch high enough to spin the wheels.

    oh yeah, I wouldn't recommend going to low or you will shorten the life of the tire. 3 of my tires will not seal completely on the rim now. really blows. p zero nero's tires. I have to constantly add air now. stick with stock pressure or slightly lower.

  8. #7
    Moderator YBNormal07's Avatar
    Join Date
    Jul 2003
    Location
    PA
    Posts
    6,245
    I Support ClubWRX
    Speaking from personal experience, and having posted one of the fastest stock 04 sti times (if not the fastest---but I'm humble ), I can state that higher tire pressure is better if you are performing a hard launch. If you are performing a soft launch, then you are slipping the clutch. With high tire pressures and a hard launch, the wheel spin adsorbs the majority of the drivetrain shock. With a soft launch, the clutch is adsorbing the majority of the drivetrain shock. When done correctly, they can both provide excellent 1/4 mile times.

    I prefer the higher pressure hard launch method as for me, I was able to achieve better times.

    I did not like using a soft launch as I cringed every time when I smelled the smoking clutch. That is just me though. Others may cringe about a quick release on the clutch and wheel spin (or wheel hop sometimes). However, I also tracked the car quite a bit, and felt the tires are an acceptable wear item, whereas I wanted the clutch to last a while.

    The thing to remember is you are making a choice as to what gets the most abuse when you choose your launch. The clutch or the tires.

    Another thing to consider is that even with a soft launch and stock or lower than stock pressures, you risk damage to the weak link in the drivetrain....the tranny in the WRX (not so much an issue with later models) and the shafts in the STi. With stock or lower pressures, once the tires hook up, they really hook up....something is bound to give. Personally....I choose a bit of tire abuse every time. I highly recommend against a stock or low pressure, hard launch method. You are only asking for problems at some point in time.
    Last edited by YBNormal07; 03-12-2007 at 04:04 PM.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

  9. #8
    Registered User Orbit's Avatar
    Join Date
    May 2003
    Location
    TdO4 12.4@109
    Posts
    135
    I only do hard launch, and have no problems breaking the tires loose every time, regardless of tire pressure.

    if your tires are spinning allot, then better traction will help you to get a better 60, lower pressure.... if you launch at too low of an rpm you will bog regardless of your tire pressure.. why do you think drag cars use slicks?

  10. #9
    Moderator YBNormal07's Avatar
    Join Date
    Jul 2003
    Location
    PA
    Posts
    6,245
    I Support ClubWRX
    Quote Originally Posted by Orbit View Post
    I only do hard launch, and have no problems breaking the tires loose every time, regardless of tire pressure.

    if your tires are spinning allot, then better traction will help you to get a better 60, lower pressure.... if you launch at too low of an rpm you will bog regardless of your tire pressure.. why do you think drag cars use slicks?
    And now you have leaking tires. I guess if that is acceptable to you, then hey, whatever works

    Maybe I didn't explain myself too well, as the whole point was to demonstrate that when someone drags their AWD subaru, different methods produce different results, and different risks. Sure, you may be able to get a better 60 footer if you use lower pressures in the tires, but it comes at a higher risk. For you, the tire seals are now bad, and this is acceptable. To others, it may not be. But is it worth the risk? I've gotten steady 1.7 sixties with my method, and a few high 1.6's. Not bad imo.

    Comparing a rally based car to a drag car is really not appropriate don't you think? A true drag car setup with slicks has a suspension designed to transfer weight towards the back on launch, a purpose built rear diff, driveshaft, tranny, and axles, and generally, just a stonger drivetrain. The impreza is not a drag car, so treating it like one will only cause it to break. It is amost guaranteed eventually.

    Think of it this way....so if I put snow tires on a drag car, I should be able to keep up with an STi or WRX in the snow yes? Of course not. So, merely trying to make your STi or WRX tires more sticky by lowering their pressure isn't going to make it respond like a drag car either. And I promise you, there will be a broken trans or a snapped axle with this method eventually. No doubt about it. It sounds like the only thing that has saved your car so far is the tires spinning on the rims. If they hadn't, something else would have given. I'm not saying anyone is wrong for using this method. It's just a matter of what you can accept as a loss when something breaks. For me, the tires are easier to replace than the clutch or tranny.

    An impreza modified to operate as a drag car usaully includes the upgrade of the clutch, axles, and sometimes the diff. It also takes some good suspension work to change the weight transfer. In fact, the faster impreza's use an automatic transmission, modified for that purpose, along with stand alone EMS for launch control and pinpoint AFRs. Totally different from your average subaru.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

  11. #10
    Registered User Orbit's Avatar
    Join Date
    May 2003
    Location
    TdO4 12.4@109
    Posts
    135
    haha, your funny i don't think that my tires spun on the wheels all 125 runs at atco.
    I also didn't say that leaky tires is acceptable . i wouldn't recommend going as low as i did. I wouldn't recommend going to much lower then stock. but lower will help. . like you, just trying to show how the results can differ.

    I knew you would bring the drag car thing up too. The car I had in mind was julie's easy street awd wrx.

    http://www.esxmotorsports.com/html/sema.htm



    Quote Originally Posted by YBNormal07 View Post
    And now you have leaking tires. I guess if that is acceptable to you, then hey, whatever works

    Maybe I didn't explain myself too well, as the whole point was to demonstrate that when someone drags their AWD subaru, different methods produce different results, and different risks. Sure, you may be able to get a better 60 footer if you use lower pressures in the tires, but it comes at a higher risk. For you, the tire seals are now bad, and this is acceptable. To others, it may not be. But is it worth the risk? I've gotten steady 1.7 sixties with my method, and a few high 1.6's. Not bad imo.

    Comparing a rally based car to a drag car is really not appropriate don't you think? A true drag car setup with slicks has a suspension designed to transfer weight towards the back on launch, a purpose built rear diff, driveshaft, tranny, and axles, and generally, just a stonger drivetrain. The impreza is not a drag car, so treating it like one will only cause it to break. It is amost guaranteed eventually.

    Think of it this way....so if I put snow tires on a drag car, I should be able to keep up with an STi or WRX in the snow yes? Of course not. So, merely trying to make your STi or WRX tires more sticky by lowering their pressure isn't going to make it respond like a drag car either. And I promise you, there will be a broken trans or a snapped axle with this method eventually. No doubt about it. It sounds like the only thing that has saved your car so far is the tires spinning on the rims. If they hadn't, something else would have given. I'm not saying anyone is wrong for using this method. It's just a matter of what you can accept as a loss when something breaks. For me, the tires are easier to replace than the clutch or tranny.

    An impreza modified to operate as a drag car usaully includes the upgrade of the clutch, axles, and sometimes the diff. It also takes some good suspension work to change the weight transfer. In fact, the faster impreza's use an automatic transmission, modified for that purpose, along with stand alone EMS for launch control and pinpoint AFRs. Totally different from your average subaru.

  12. #11
    Moderator YBNormal07's Avatar
    Join Date
    Jul 2003
    Location
    PA
    Posts
    6,245
    I Support ClubWRX
    Quote Originally Posted by Orbit View Post
    haha, your funny i don't think that my tires spun on the wheels all 125 runs at atco.
    I also didn't say that leaky tires is acceptable . i wouldn't recommend going as low as i did. I wouldn't recommend going to much lower then stock. but lower will help. . like you, just trying to show how the results can differ.

    I knew you would bring the drag car thing up too. The car I had in mind was julie's easy street awd wrx.

    http://www.esxmotorsports.com/html/sema.htm
    Didn't you say your tires were leaking around the seals? If so, how do you think this happened?

    I'm not sure what posting Ali's car has to do with this, as it is a good example of what I was trying to get across. BTW...I've driven Ali's previous drag car, and helped them rebuild the AUTO transmission once. Doesn't mean I know anymore than you though.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

  13. #12
    Registered User Orbit's Avatar
    Join Date
    May 2003
    Location
    TdO4 12.4@109
    Posts
    135
    I don't know why you keep bringing up my leaky tires. Did you not read my entire first post?

    My only disagreement with you is this:

    Quote Originally Posted by YBNormal07 View Post
    I can state that higher tire pressure is better if you are performing a hard launch.
    But, hey maybe thats what works better on your car. Not on mine.

  14. #13
    Moderator YBNormal07's Avatar
    Join Date
    Jul 2003
    Location
    PA
    Posts
    6,245
    I Support ClubWRX
    Quote Originally Posted by Orbit View Post

    oh yeah, I wouldn't recommend going to low or you will shorten the life of the tire. 3 of my tires will not seal completely on the rim now. really blows. p zero nero's tires. I have to constantly add air now. stick with stock pressure or slightly lower.
    Yeah...I did, and to me this says your tires spun on the rims. A common occurance for tires that grab well and aren't screwed on. Haven't you ever noticed that on a setup drag car, the tire edges are screwed into the rim to prevent this from happening?

    And if you read mine, you'll note I said it's a matter of choice. I never said lower pressures don't work....they are just more abusive to the drivetrain, which I've noticed you seem to not address. No biggee. We'll just agree to disagree.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself. We strongly suggest that you stay away from using aol, yahoo, msn, and hotmail accounts. Sometimes the mail server blocks the emails from our server. As a result you will not receive any notifications including the confirmation email.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •