M/T Drag radial size

devon lock

devon lock

12 valve
Joined
May 2, 2008
Messages
419
What size Drag radial are ppl running with 3.55 gears? I am ordering rims and tires next and can't decide between M/T305/45R18 (29'') or M/T 295/50R16 (28''). There is about 5MPH difference between them at 4000RPM.
 
a buddy told me he say 31inch tall nitto street slicks on display at sema, those would be awesome, mickey t's have a 28.8 tall that alot of us use, either way they hook way better than proxes
 
thinking about trying m&h 390/40/17 but 17x10 wheels are kinda hard to find.
 
Right now my tires are 31.5 they are too tall, I am only at 3000 at end of the track. The 29's will put me at around 3500 and the 28's will be close to 4000, just can't decide what would be better.
 
devon lock said:
Right now my tires are 31.5 they are too tall, I am only at 3000 at end of the track. The 29's will put me at around 3500 and the 28's will be close to 4000, just can't decide what would be better.
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3000
 
Dockboy said:
I know...

Why do you think you want to be above that?
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Sorry. I shift between 3700 and 4000 it seems like pulls the best there, I only hit overdrive past the 990 mark. When I used Brads slicks which I think were 32'' I ran faster but lost close 5mph. I was told you should be almost tached out at the end of the track. So I am sure a lower tire should help my times.
 
devon lock said:
Sorry. I shift between 3700 and 4000 it seems like pulls the best there, I only hit overdrive past the 990 mark. When I used Brads slicks which I think were 32'' I ran faster but lost close 5mph. I was told you should be almost tached out at the end of the track. So I am sure a lower tire should help my times.
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You will run faster times if you keep the engine in it's power band which means keeping the engine between 2800-3300...3500 tops. Have you ever dynoed your truck? If so, look at the curve. I highly doubt you are making more power at 3700-4000 than you are at 2800-3200.

I will give you a real world example...

A young friend of mine was doing the same thing as you, shifting at 3700-4000. Actually wasn't even going into overdrive. He was running 12 flats at 113. I told him he needed to shift sooner and as fast as he could. Next pass out doing what I told him to do, he ran 11.5 at 118.

I am in overdrive before the 1/8 mi ;)
 
Dockboy said:
You will run faster times if you keep the engine in it's power band which means keeping the engine between 2800-3300...3500 tops. Have you ever dynoed your truck? If so, look at the curve. I highly doubt you are making more power at 3700-4000 than you are at 2800-3200.

I will give you a real world example...

A young friend of mine was doing the same thing as you, shifting at 3700-4000. Actually wasn't even going into overdrive. He was running 12 flats at 113. I told him he needed to shift sooner and as fast as he could. Next pass out doing what I told him to do, he ran 11.5 at 118.

I am in overdrive before the 1/8 mi ;)
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I did do back to back passes last year one auto shifing at 3200 and one manual shifting at 3500-3700 I ran a 11.35 auto shifing and 11.09 manual shifting. I did run on the dyno last year peak HP was around 3500 and peak tq was around 3300- 3400. I think I might go with the 29'' tires than it will keep me closer to 3500 rather than 4000.
 
Turn the power up and run faster,then you don't have to change gear ratios or tire size
 
devon lock said:
I did do back to back passes last year one auto shifing at 3200 and one manual shifting at 3500-3700 I ran a 11.35 auto shifing and 11.09 manual shifting.
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How are you "auto" vs "manually" shifting? Are you data logging your passes so you can see exactly what the rpms are? If you are using something like a PCS controller, don't be fooled by the shift point setting. The rpms rise faster than the tranny can react. In other words, if you set it to shift at 3200, it actually is shifting somewhere around 3800.

Remember, this is not sledpulling or gasser drag racing! Sledpullers need high rpm for two reasons. One, they usually don't shift so they need high rpms with a short gear for wheel speed. And two, their engine rpms are pulled down into their power range during the pull. Gas enginges typically make more power the higher the rpm. That is why they run lower gears.

This is why dynoing is important. Look for the flatest part of your curve and keep the rpms there. Your rate of accelleration is deterimed by hp not tq.
 
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