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I bought a raco gn to race at a local dragstrip. I am looking to gear it to get better acceleration, it came with 18/30 gears. What gearing would be good for drag racing and where can I get gears to fit the quick change rear?

Attached is the Skellenger gear chart. There are several gear ratio apps for your phone that can help. You need to know the terminal engine RPM and tire circumference for starters. I have a bunch of gear ratios for the Skellenger rear, just let me know what ratio that you need. There are a lot on people here on QSL that I am sure will provide you with more information.

how do i find out the terminal engine rpms?

What engine are you running, how long is the drag strip that you will be using.

The strip is 1/10 scale and my car has a zenoah motor. Not sure bow to tell which one, can't find any numbers on it.

Zenoah G2D is my guess.

Carburetor: G2D-1140--Walbro WY-1A; G2D-1148--Walbro WA-167

Idle RPM: 4000 +/- 300 rpm

Max RPM: ~12000 rpm 1140 version, ~14000 rpm HP 1148 version

About 1.5 - 2 HP

you are probably right vwguru75!!, any gearing ideas?

Next we need tire circumference. I will not be able to help much more with this until next Friday. I am having my house tented to kill pesky termites and I need to move into a hotel Monday. But, I will try to get some numbers for you. If anyone has any ideas please jump in. Once I get a tire size we can work the problem. I am going to call John Foster at Quarter Mortar and bounce this off him as well. I have several gear sets and I am sure we can get you close. Al

The problem is going to be torque. The engine is not going to have the grunt to run a gear and tire combo toget off the line AND have a respectable top end.

Just my opinion.

Do you think it would be best to run a smaller diameter tire?

You are not going to do very good if you have a quickchange rear end. The best gear ratio you can get is 6 to 1. If to are running a motor smaller than a 30.5 then you are going to need to change over to belt drive and get a gear that is closer to 9 to 1. then you can run your 8" tire.
John

thanks for the help. the tires I am running are 5 3/4 in across. this is my first 1/4 scale car so trying to get it to be fast as cheap as I can without to much custom mods. so would the clutch spring be my best bet for a good launch. I don't really care about top speed as much as the launch.

John, what gears would I need to get the 6:1 ratio for the quick change?