Changing Pinion/Spur gear in Firehammer, what MPH increase to expect? (FG Marder)

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camncars

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I have a Duratrax Firehammer that I am changing the spur/pinion gear on. The stock gear for this car is a 48 tooth spur and a 19 tooth pinion. I will be installing a 44 tooth spur and a 22 tooth pinion for more top end. I have clocked the car in stock form at 34 MPH. What mph increase should I expect to see with this gear change? I know it will loose low end power, am I going to KILL the low end with this setup or will it be decent. I just do bashing at local parks/fields, no short-track type of racing, so I think I should be okay with this. Top speed estimates anyone????
 
The firehammer came with a CY23cc motor and stock size buggy tires (approx 5.75 inches tall i believe. everything is stock
 
Well, you will loose quite a bit of the low end. You can always swap back though. WHat gears are you getting? The gears are different between FG and DTX.
 
Well, I got the gears already, they are fg gears, and the only thing I forgot to order is the 52mm spur gear carrier, which I am going to order now. I test-fit the gears and they seem to mesh just fine, like I said, the stock gears in the firehammer are 19/48 which total 67 and the fg gears that I found are 22/44 which total 66, mesh should work just fine. I was trying to find a 46 spur and 20 pinion, but they are out of stock (maybe you/someone here know where they stock them in the u.s.a.????)
I do alot of mid/hi speed bashing in large fields so I'm not too concerened about loosing the low end, and if I decide to go to smaller areas it's only a 10 minute job to switch back the gears. I'm looking foward to seeing what kind of mph this will be on my radar gun, should be worth the $35.
 
thats quite a large gear change, one tooth on a pinion can make a big difference.

running 66 teeth total should work fine, ive run 66 total with duratrax gear plate. however with fg gears adding the teeth up doesn't always work. for example, 39, 40 and 41 tooth spur gears all have the same diameter, same with a 23, 24 and 25 tooth pinions. you can run 23/39 totaling 62, or 25/41 totaling 66 and it will mesh just fine on the same gear plate. fg uses regraded gears, meaning the pitch is slightly different, but not enough to cause problems.
 
Here's what I came up, kind of a guess in a sense, but if 19/48=.396 and top speed was 34 mph, then if I go with 22/44 = .5 that should get me 43mph sound correct???? (.5 x 34 divided by .396 = 43) does this make sense?
 
ok, i had 19/48 gears on xtm, it did just under 40mph, then i put a tuned pipe on it,and it was faster top end, what im saying is if you don't have the power to push taller gears,it wont got faster!just got 21/46 gears and now its about the same as my fg,around 50 mph, so the gears you have are going to be extremely high, if you have enough power /revs to get there.so i feel that the xtm with a 27cc engine didnt have enough power to get the top speed out of the standard gears ratio(19/48)until i put a pipe on it! now i got the taller gears,(the gears are blackbone steel or something,and was off ebay new for 40 quid.) i have seen another improvement, but don't think i can go higher as not enough power.i also changed the 16 t layshaft fot a 17.
I will gps the car today if i have time, but it should do around 50mph, maybe a bit more with the 17 layshaft gear, but i really do think its the limits of the engine and pipe power, same with the marder,the best i can get is 54mph with jetpro high end pipe and 28.5 cc engine, i tried next tooth up,but it wouldnt hit top revs that time so didnt have the power to get to the top.
 
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Well, I got the gears already, they are fg gears, and the only thing I forgot to order is the 52mm spur gear carrier, which I am going to order now. I test-fit the gears and they seem to mesh just fine, like I said, the stock gears in the firehammer are 19/48 which total 67 and the fg gears that I found are 22/44 which total 66, mesh should work just fine. I was trying to find a 46 spur and 20 pinion, but they are out of stock (maybe you/someone here know where they stock them in the u.s.a.????)
I do alot of mid/hi speed bashing in large fields so I'm not too concerened about loosing the low end, and if I decide to go to smaller areas it's only a 10 minute job to switch back the gears. I'm looking foward to seeing what kind of mph this will be on my radar gun, should be worth the $35.
21/46 is a great ratio.
 
did you try changing the transfer gear? i have a firehammer also and thats what i did and made a nice differance. the buggy comes with a 16 tooth and the mt comes with a 14, if you put the 16 on the mt you'll still have good bottom end and more top end.
 
did you try changing the transfer gear? i have a firehammer also and thats what i did and made a nice differance. the buggy comes with a 16 tooth and the mt comes with a 14, if you put the 16 on the mt you'll still have good bottom end and more top end.
put a 17 on layshaft , 10 quid off ebay, steel brand new.beteer top end, so now has 21/46 and 17 lay, 48 diff, good for 50mph +, just make sure you have a alloy small mount, even the plastic big mount is starting to go!!!
 
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