Tire pressures for the track

[IdahoRob]

I've been reading a lot of threads on what tire pressures to run on the drag strip and thought I'd add some of my findings.

Seems most like to run more psi in the front (me too in the early days), why is that? I thought there is a lot more weight in front so need more psi to support the weight compared to the light weight rear.

So I did a lot of testing on my 12 second heavy street trucks as well as the race truck. Of course we can't scale the truck while it's moving down the track, so i had to rely on photos and videos. My race truck is scaled about 63% of weight in the front leaving 37% in the rear. This is most likely similar to street/strip trucks, but I have not scaled a street/strip truck (I will when Dustin's is done this week) at each tire to be sure.

On to the track and weight transfer. On the launch everything moves back correct? Much more weight on the rears, as the truck moves down the track, weight should transer forward. So finding the happy average so we are not fighting the t-case vs front and rear is the goal.

Here is a good photo of the rear taking the hit.

 

[IdahoRob]

But what I found was the trucks were still carrying a lot of weight on the rears down on the big end of the track also. Here is a short clip of the race truck.
http://www.youtube.com/watch?v=Z34ZO6ct378

The race truck has a bit more HP then most street trucks (except dimitri of course) but when testing on my street trucks, I found that bringing the front pressure down to the rears, I picked up MPH with nothing else changed even on a heavy street truck.

So next time at the track try running some tests with front tire pressure changes and you may be surprized. The goal is to have a good guess on the average down the length of the track. Testing will confirm.

 

[DuramaxPowered]

Good info, thanks Rob!!:thumb:

 

[paint94979]

Very interesting... Thanks for sharing

 

[S Phinney]

I think I will give it a try next time out and see what happens. Thanks for sharing. Did you notice any time decreases as well as mph gains?

Sent from my DROID RAZR using Tapatalk 2

 

[IdahoRob]

I could never confirm that as I had a hard time duplicating my 60' times so no real data there. Street trucks that is...

 

[Evan@InglewoodTrans]

Great info thanks.

 

[paint94979]

When I used to run 12.3's at 108 with a GT4094R I ran 30psi on all 4 tires and was very consistent at 1.64-1.68 60's. Fast forward to my S475 I changed tires psi and power and was never able to ever come close to those 60's. I'm lucky to click off a 1.69 now

 

[TheBac]

Looking back on pics of my truck launching, I dont see any obvious differences in sidewall height. Maybe since street tires have stronger sidewalls than slicks and drag radials that they arent affected as much? Either way, its worth checking.

Id have to go back and look, but IIRC my normal pressures were 38/30. I've 100% agreed with your advice on trying to keep rollout the same front-to-rear so the drivetrain wouldnt fight itself down the track. It sure worked well for my truck.

 

[whitetrash21]

I did notice the front getting real nasty on the camber when you came off the throttle. That's some serious suspension unloading going on Watch around the :13 second mark

crappy youtube extraction pic

BTW, that thing is cranking when videoed from the big end of the track

 

[TeaBagger2006]

wes......you know we are in the year 2013

 

[whitetrash21]

FAWK!!! I'm still partying like it's '99

Thread jack over....


For what its worth, when I remembered to air mine down, I ran 35 front, 25 rear. Never varied from that. Don't know that I made anywhere near enough power to make a difference though.

 

[Mpsoldier]

great info going to have to try this :thumb:

 

[IdahoRob]

I did notice the front getting real nasty on the camber when you came off the throttle. That's some serious suspension unloading going on Watch around the :13 second mark

crappy youtube extraction pic

BTW, that thing is cranking when videoed from the big end of the track

On the race truck the toe/camber/caster is adjusted for full throttle, nothing else matters to me

Videos tell a lot, tire pressures from side to side are also something to look into.

 

[whitetrash21]

On the race truck the toe/camber/caster is adjusted for full throttle, nothing else matters to me

Videos tell a lot, tire pressures from side to side are also something to look into.

Lol , I hear you.

It just proves what you're saying about weight transfer to the back, even on the big end, when you see how much actually drops on the front once the throttle is lifted.

 

[FC5452]

Thanks Rob, Now you have me looking at all my passes, On the first 60 on mine you can really see the weight transfer being shown, then at the 1000 see it drop forward, of course I am not making the same power , but the principal applies just the same.

 

[sickdiesel]

On the race truck the toe/camber/caster is adjusted for full throttle, nothing else matters to me

Videos tell a lot, tire pressures from side to side are also something to look into.

because RACETRUCK

 

[07metallicgreen]

i've always wondered about this. i have a hard time launching when i raced but i cut was a 1.9. im no where near your power but i can still see the weight transfer

 

[Dan@PPE]

Rob,

have you finished testing this yet? If so would you mind sharing? 60ft better? quicker e.t.? MPH?