Author Topic: Gear ratio and consistency  (Read 436 times)

Offline BK

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Gear ratio and consistency
« on: December 28, 2020, 08:14:07 PM »
Figured this section was good for a gear discussion.
Any thoughts or experience as to what might be more consistent.
My car has 4.30 gear now I have a set of 5.30s if it looks like it might be more consistent.
The track I race at has been running 1/8 mile and doesnt look like that will change any time soon.
1700# Altered, SBC, 630hp @ 6500, 560ft-lbs @ 4700, 1.76 glide. 15x33 slick, converter flashed to 5200 RPM but that engine was about a 100hp less.


Offline THE FRENCHTOWN FLYER

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Re: Gear ratio and consistency
« Reply #1 on: December 29, 2020, 05:33:22 AM »
I am running an altered too.  Last year I looked at my car. When I built it we were racing the full quarter mile in Super Pro brackets. Now almost every (insured) track has switched to eighth mile S/Pro racing. In addition, even the smaller mom-n-pop strips have taken to doing effective starting line prep for good bite. I'm using 4.30 gears and 12 x 32 slicks on my 1800# altered with an inline six. So I asked myself "why am I still running 4.30 gears and a 1.76 'glide and carrying a huge tire down track?" I need more gear and less tire. So I switched from a 12 x 32 to a 10.5 x 28S which not only increased my effective gear ratio but also reduced the rotating mass of my tires since each of the smaller tires weighed about four pounds less. I did not change gear ratios.
I picked up about .05 in the sixty and around .10 in the eighth.
My six cylinder is making about 550 HP on gas. It runs 5.6 / 5.7 in the eighth and 9.0 in the quarter.

With 650 HP I'm guessing you are running around 5.1 / 5.2 times. If your track preps the track why not try a smaller tire before switching to a taller gear?
« Last Edit: December 29, 2020, 05:35:04 AM by THE FRENCHTOWN FLYER »

Offline BK

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Re: Gear ratio and consistency
« Reply #2 on: December 29, 2020, 02:39:37 PM »
The engine is new to me this year and I haven't run it yet.
With the engine that was in it 5.70s.
I was guessing more like 5.30s 40s with the added HP and will start the year with the 4.30s.
The reason for gear change is I have them so there wouldn't be any real cost involved to change them.
I dont have tires and we know how expensive they could be.
Did you notice any difference consistency wise with different size tire?

I am running an altered too.  Last year I looked at my car. When I built it we were racing the full quarter mile in Super Pro brackets. Now almost every (insured) track has switched to eighth mile S/Pro racing. In addition, even the smaller mom-n-pop strips have taken to doing effective starting line prep for good bite. I'm using 4.30 gears and 12 x 32 slicks on my 1800# altered with an inline six. So I asked myself "why am I still running 4.30 gears and a 1.76 'glide and carrying a huge tire down track?" I need more gear and less tire. So I switched from a 12 x 32 to a 10.5 x 28S which not only increased my effective gear ratio but also reduced the rotating mass of my tires since each of the smaller tires weighed about four pounds less. I did not change gear ratios.
I picked up about .05 in the sixty and around .10 in the eighth.
My six cylinder is making about 550 HP on gas. It runs 5.6 / 5.7 in the eighth and 9.0 in the quarter.

With 650 HP I'm guessing you are running around 5.1 / 5.2 times. If your track preps the track why not try a smaller tire before switching to a taller gear?

Offline THE FRENCHTOWN FLYER

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  • Your Best Time: 8.28@168 door; 9.00@147 6-cyl alt; 8.53@160 RED
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  • Your Vehicle: (3) Advanced Chassis altered , The Last Logghe altered, '30 RPU
  • General Location: North Coast
Re: Gear ratio and consistency
« Reply #3 on: December 29, 2020, 03:43:53 PM »
The smaller tires were every bit as consistent as my larger tires. I got a real deal on them as a guy had them on his doorslammer and they rubbed so he took them off. A prominent Comp Eliminator inline racer who runs 9" slicks (!) said the stiff sidewall is the best choice for my combo. I lucked out .