4k4m3

My son drives a Kyosho Fazer MK2 (casual 1:10 touring car) with the standard 68T Spur. Standard gear ratio is 6.5 in the car with a 32T pinion.
At our local track, rookie races allow a max ratio of 5 on a 17.5T stock motor.
We could increase the pinion to 37T max (because of motor mounting plate limitation) to reach a ratio of 5.6.
Or we could hack things a bit by adapting a 55T Spur from traxxas 4tec and use a pinion of 33T to reach 5.1
68x37 vs 55x33, the ratios are a bit different but should I expect the car to run wildly differently?

Sir 51D3WAYS

Not hugely different, but quite different indeed. For a given motor, noticeably slower acceleration and a higher top speed. Also higher motor temps. May need a fan.

fyrstormer

iTrader: (1)

It will be slower to accelerate and slower to brake. You'll have to start braking for corners sooner. What you need to ask yourself is whether the extra top speed would actually be useful on the track you're driving on. If you can't reach top speed consistently without crashing into the barrier at the next corner, you're better-off keeping the faster acceleration that a lower gear ratio provides.

the rc guy

ok he cant have the gear ratio he is stuck having its against the rules. this is why I have a Dremel tool with 1000's of bits. cut a new mounting slot so you can run required gear ratio. done it many times

Billy Kelly

iTrader: (9)

not everyone knows these tricks. Or trust their ability to do modifications

BigBuckORamma

Wait...

Do they have a 5:1 limit?

Or a 5:1 requirement?

A 5:1 Limit should mean that you can gear no higher than 5:1, meaning that something that is 6.5:1 is BELOW that limit. Because it takes more motor turns to one wheel turn, meaning you arent over gearing for more top speed. I have never heard of a track complaining of under gearing. You may want to get clarification on what exactly they mean. Because i feel like someone doesnt understand how a gear ratio works. "We wont let you race unless you over gear your car" seems like an odd stance to take.

If it has a 5:1 requirement, they should have some pinion charts, and assist you in getting it set up for racing, if that is your goal. If they have no interest in trying to help you get dialed in for racing...then maybe thats not the track/hobby shop for you?

We have a 21.5 2WD buggy class here, and the gearing requirements for both TLR and AE spur/pinions are clearly posted for everyone.

sosidge

Something to bear in mind...

The TOTAL number of teeth on your spur + pinion needs to be in the same range as the existing gearing for the new gear to mesh.

So, if the Fazer meshes with 32T pinion and 68T spur, you would need a 45T pinion to mesh with the 55T spur in the same mounting holes.

Basically you need your pinions to be 13 teeth bigger in order to mesh with a spur that is 13 teeth smaller. These are big pinions, which brings it's own problems.

I would look for a spur that is only a few teeth smaller if you can find one.

I don't know what Traxxas offer, but one option is RW Racing in the UK, who can do custom gears to order.

Vertebreaker

iTrader: (6)

Like BigBuck mentioned, your gearing should be fine where it is. Novice classes normally do have a gearing limit because they don't want the new drivers launching a rocket down the track and into walls and other cars. So in this case a 4.75 FDR would not be legal but your 6.5 FDR is good.

OffRoadJunkie

iTrader: (9)

I'm not sure if you're accepting racing advice, but a question that some guys on here were getting to is, can your kid race around the track, at his current top speed, without crashing every other lap? If a racer can't get around the track without crashing, then there is no reason for them to go faster. A higher gear ratio will get you around the track 2 seconds faster, but one crash will set you back 10 seconds.