Ultima pinion choice.

[Mad Racer]

Can anyone advise me on what pinion to start around with a sport tune motor.

23t i think.

Racing on a medium seize 10th scale track.

Any help much appreciated.

Cheers.

Mark..

[RichieRich]

I assume you're taking about the older Ultimas with 32 pitch gears. I would start with a 15 tooth pinion. The Ultima does not have the best ratio range since the spur is rather small and cannot be swapped.

The internal ratio is 3.03 and the spur has 44 teeth. So, from there you can calculate your gear ratio with different pinions.

[vwjuice]

I ran a 13tooth with a 27turn in my daughters' outrage last year and it just spun the tires on the approach to the jumps. On the straights it was passed left and right cause of no top-end. I think the richierich is dead on, 15tooth would be the way to go.

[Mr. ED]

Seen you propose a 23 teeth pinion, I guess you have the 0.5module spur?
Best thing to start with is count the nr of teeth on your spur as they came in different versions.

[RichieRich]

Who's proposed a 23 tooth pinion?

The Ultima came with a standard 44 tooth spur (.8 module) which is nearly 32 pitch. Therefore, you can use 32 pitch pinions. At least I've never had any problems.

Some of the "newer" Ultimas based on the original gearbox have 48 pitch spur gears. I am not sure how many teeth those have but I think those came with a 20 tooth pinion stock. In this case, it's probably a good starting point for a stock-type motor.

[Mad Racer]

Thanks guys.

Im starting with a 15t tan work my way up.

What was the standard pinion with the first gen Ultima.????

As they came out with a Mabuchi 540 im pretty sure.

Gee this Ultima is light as and i think its going to rip on the track.

Thanks again.

Mark.

[dreambmx]

I used to run an 18 tooth on ovals. You had to modify the motor plate though to get it to mesh properly.

[Mad Racer]

Thanks but my pinion of choice was spot on.

WOW this buggy was so good on the track at the Australian Vintage Meet at Sydney.

Jumped really well and was super smooth every where. The tranny was so quite i couldnt hardly hear it,

Was a great meeting with it and is my favorite buggy now.

[Returning_Jim]

I know this thread is kinda old but I've been pondering this as well and thought it would be better to add to an existing thread rather than start a new one.

Nobody asked the thread starter what tires he was using. If he happens to be using modern larger diameter tires then all suggestions need to be adjusted accordingly.

What are people using on their Ultimas with modern tires? I'm running CRP front axles which adapt to Tamiya wheels. My wheels are from a "Desert Gator" IIRC, and I'm trying to use Pro-Line Dirt Hawg tires. These are quite a bit larger in diameter than the stock old-timey Ultima tires.

I'm thinking I need a 12t or 13t with these big tires.

James

[Mr. ED]

Hey Jim, modern tires are not bigger on the outside diameter. They have a larger inner diameter for the larger wheels. The idea is to reduce the tirewalls higher so it deforms less under sideway loads

[Returning_Jim]

Ed, thanks for the reply.

I do understand the principle you are talking about. And I was aware that that was the goal back in the late 80s when the 2.2 wheels first came out. However I got it in my head that in the ensuing years between then and now, 1/10 buggy tires grew in diameter for some reason. The picture below shows why I got to thinking that.

I have here an Optima wheel with a street tire on it (from one of the scale series kits) next to my Desert Gator wheel shod with the Pro-line Dirt Hawg. I overlaid another Optima wheel and tire over mine in Photoshop because I didn't have any vintage dirt tires to compare with. I did the jaggy cutaway to show that I have properly maintained the scale. Anyhow, you can see that if you ignore the spikes, there is a drastic difference in diameter. On the Optima side, I put the red dimension lines about half way up the spike height since I figure that's about equal to the Dirt Hawg tread depth. ...So this is why I said what I did. I don't have much else to look at around my house to draw other conclusions. Are the Dirt Hawg tires just abnormally tall in side wall??

thanks,
James

[losiXXXman]

Part of the issue is the dirt hawg tires. I find that they do have a higher sidewall. I think the reason is, if running these "streetish" tires on say a concrete off road course, the additional sidewall gives additional ground clearance. A useful tool if running off road on hard concrete. (saves parts!)

[Returning_Jim]

Can you recommend another "dual purpose" type of tire but which has a "normal" side wall height?

Thanks

P.S. cool blog

[Hcp22]

Can this be to any help perhaps? From the Ultima manual (0.8 pitch)

[Returning_Jim]

Yep, that is quite handy, thanks. Given that I was going to run a LeMans 240ST, and my larger tires, I'm thinking of trying a 13T.