I don't know all of the particulars, and don't feel like using the speed calc at the moment to see how much difference it'll make, but Ofna does make a 48T spur for the spider diffs. Part #OFN19345

Edit: I did just visit BrianG's site to figure out the diameter of the Spur gear and it says the 48T will be 1mm bigger in diameter than the 47T. But thats diameter, in reality the spur will only be .5mm closer to the pinion.

Ok, well crunched some numbers for ya.

To fit the 56 series motor in you need to move the centerline of the motor 7mm away from the current location with 47/12 gearing. Does your mount have that amount of slot length avaialbe?

That does not really matter, cuase you would need a much bigger spur to get gearing right if you ran 1000kv motor on 10s. A 62t spur from the old jammin crt would work, with an 11t pinion. That will place the side of the 56 leopard right up against your mech brakes, just as the 1520 is sitting now with the 12/47 gearing. However with a 6:1 ratio that pinion is not going to last very long. Any you would be geared for low 40s. So you could go up to the next higher kv, 1250. That would give you low 50s with your 6.88 tall tire and bp diffs. Or you can go to a 14t pinion, but you are running out of motor mount adjustment then.

The 62t spur is a feeris wheel, but when you run low ratio (numerically) diffs and no tranny you need some reduction somewhere.

Heres the numbers:

1520 = 42mm dia - 21mm rad
56 leopard = 56mm dia - 28mm rad

7mm diff

47/12 gearing = 31.5mm between centerline of gears

Add 7mm = 38.5 to fit the 56 leopard and have the can as close as you have the 1520.

Jugle the numbers on BG's site and with a 62t spur you need an 11t pinion to get 38.5mm between the centerlines.

A 52/21 would also work, but with less overall reduction you would need a much slower spinning motor. Not sure if you could run a very low kv 56 size motor in there. Around 600kv would work, but the load on the motor will be very high.

Thanks linc for doing the crunching... really do appreciate the help!

So...
Yes i do have the 7mm adjustment needed to push the pinion away from the spur due to the larger motor can....
BUT
i do not think that the larger 62t spur you are talking about will work with my ofna spider diff... and OVERDRIVEN, i dont think that 0.5mm will make enough of a difference with y current situation.... I think i did see a 52t somewhere, but i am unsure about that....
But i am worried, that if i use a spur which is too large, it will then hit my top plate on my diff mounts....

Linc, just out of curiousity, will the 56 motor have similar mounting points as the castle motor?

I am now considering turning my motor/diff mount 180 degrees now, and have the motor mounted at the rear and somehow mount the 3rd lipo up front. This would give me more space for a larger motor as i have plenty of space in teh rear.
AND
I wont have any problem clearing my front brake mech. I will just not run rear brakes and i can run what ever pinion size i like and mesh as close as i want.

But i cant work any of this out till my Chassis arrives from GCM....

Linc thanks again!!! i will update this thread when i know more about the space i have to work with....

Im not even sure if the motor will sit right when mounted to the motor mount.... because it will be too fat and hit off the side of the tvps?

You will see what i mean...

Not likely, the 56 leopard has m4 thread holes 30mm apart.

Yeah, post some pics when the chassis comes in.

It would be pretty easy to figure out how big of a spur gear you can put on your CD without it hitting the top plate. BrianG's page has a gear calculator, just need to measure the amount of clearance you have. Another option is a custom top plate that has an opening (slot) in it for the spur gear. The top plate would have to be wider to accomodate the spur gear slot and still connect the diff mounts together, but it would do the job and support both front and rear brake cams.

Yes... i could get one made up. Dejan already has my top plate measurements etc..

But i dont think the Spider Diff works with anything other that a 52t...I havent seen anything bigger as of yet...