MPH drop / Tire Size

[SonicBlueSVT]

Hello,

First off I had a great time at the Hallsville event! It was nice metting some of you and watching the trucks go down the track and I wish to meet more of you as time goes on.
Now to my question.

My race setup on the truck is running 16x8's in the front and 16x10's in the rear. Both tires are 26" tall and so I was forwarned that I would mostly likely be going through the traps in OD. So for my first run I didn't turn OD off just to see. Well everyone was right! At about 75 yrds before the traps the car went into OD yet still ran my best time (12.5@109). Click here for video. Watch for the puff of exhaust near the end of the run. That's when it goes into 4th (http://www.sonicbluesvt.com/L-Video1.wmv) The truck totally nosed over when it went into OD like I expected it would and so for the next run I would hold it out in 3rd to see if it could make it and to hopefully better my et and mph.

I had a little worst 60ft on the 2nd run vs. the first pass, (1.79 vs 1.76) my 1/8 mile times were both 8.0@86, but at the end of the track I was able to pass through the traps right at 5,500rpms in 3rd which netted in a 12.6@106mph.

My question is how did I loose 3mph??? Was I getting out of my power band at all?? I should have done another run but I had to leave early and didn't have time. Both runs were made with the coolant being at the exact same temp and so I don't think heat had anything to do with it.

Any suggestions??

BTW, those Mickey Thompson Drag Radials HOOK :d

Thanks.

[03LightningRocks]

One thing you will find out, is that our trucks typically loose time with each pass. I can't tell you how many times I went to the track and my first pass of the day...was my best.

It can drive you crazy trying to better that first pass....:d .

The temp was rising and track conditions deteriorated(sp) as the day went on, so your first pass was made under better conditions than your second.

I wouldn't let it make me nuts.....but you will want to move to 28's before you start making alot more power. I just had to move to 30's. It happens;)

On the MPH...believe it or not...your MPH can go up if your tires spin a little.

[WA 2 FST]

Chris,

I've seen plenty of drag cars setup with 2-speed or 3-speed autos...and they cross the traps sometimes 1000+rpm past where they should be if they had another gear to upshift into.

But these cars are never worried about trap speed, only ET, so they give up some top-end in order to better their 60', 330', 1/8th mile times ... and then just carry it out farther down the track.

The truck may have nosed over when it shifted into OD, and it might even lose some ET compared to leaving it in 3rd, but I am very confident that by leaving it in 3rd you lost some trap speed. As Ron pointed out very astutely, 3mph may not _all_ be b/c you left it in 3rd. But I do believe that is a significant part of it.

Get some 28s and the problem will be solved. :)

[WA 2 FST]

BTW, great video. Michael did a good job getting that footage for you.

One question I have for you (and others will undoubtedly know this too). How do you get that good of a burnout? My truck kept wanting to move forward like it was getting too much grip while I was trying to heat them up. And yes, I did have my foot on the brake. Maybe I just didn't get enough water on the tires to start, I don't know. But my burnouts were very short compared to yours.

I would kill for a 1.7x 60' time. I'd have been right there with ya! 12.5x for sure. :)

[Mark #2]

One thing you will find out, is that our trucks typically loose time with each pass. I can't tell you how many times I went to the track and my first pass of the day...was my best.

It can drive you crazy trying to better that first pass....:d .

The temp was rising and track conditions deteriorated(sp) as the day went on, so your first pass was made under better conditions than your second.

I wouldn't let it make me nuts.....but you will want to move to 28's before you start making alot more power. I just had to move to 30's. It happens;)

On the MPH...believe it or not...your MPH can go up if your tires spin a little.
Ron,
Do you still have the 28s? Are they any good?
Mark

[03LightningRocks]

Ron,
Do you still have the 28s? Are they any good?
Mark
I sold them to BClightning. He said he wanted to buy my fronts too. But he hasn't contacted me in a few weeks....I dunno if he has run into problems or what.

Sorry about that Mark....I put them in the for sale forum and got bombarded by emails. I guess used Wheels/Tires don't come up for sale very often.

Rocks

[SonicBlueSVT]

Wess, when I do a burnout I just plant my foot into the brake and pretty much floor the gas pedal, (floor it then feather it.) The rpms usually go to around 5k and then it shifts into 2nd gear. In 2nd it bogs and so I give it more gas until I'm around 4k and I hold it there until I see lots of smoke coming from both sides of the truck :burnout: I'm sure you could just select 1st gear and just hold it at like 5k for a while and that would work too :)

If you don't give the truck enough gas to begin with then you might not be able to hold the burnout and the truck will start to walk on you or start to go sideways.

Hope this helps!

[WA 2 FST]

Thanks Chris. I was wondering if you were doing 2nd gear burnouts. Figured it had to be shifting into 2nd to get the tires spinning enough to do it that well.

Obviously I was just not giving it enough gas when I was starting my burnout. I'll know next time.

[Mark #2]

There is only one way to do a correct burnout.....Line lock.:tongue:

Reference: BoneDaddy's parking lot and sewer system:beer:

[True Blue Aggie]

There is only one way to do a correct burnout.....Line lock.:tongue:

Reference: BoneDaddy's parking lot and sewer system:beer:
If someone could host the final round run at Hallsville, I could show you a burnout......but I was equally impressed with Mark's efforts to flood the sewers with smoke.