Ezgo rear end gear Question!!

archer161

Ok, I'm almost done with my built for this year I have turned my stock 2007 ezgo txt into a hunting cart. I have put a high torque D&D motor, altex 500 amp controler, 8- 6volt batteries. I have tested it and it does great, but I have stock tires on it with no lift kit (got stuck a couple times on crossing ditches) I was thinking about going with 23" tires and a small lift, but did not want to lose all the torque I have now. If I go with 23" tires and go with 15.1 gears will that keep me about the same??? I have all the speed I need (more then enuff speed don't care if I slow it down some) and would love to go with a even higher gear in the rear end if anyone knows where I can find them like a 20.1 gear would be my dream gear. Can anyone point me in the right direction??????

BGW

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TerryH

I've never heard of anything lower than the 15:1's. Here's a good place to get them if you decide to do the swap.

15:1 gears

JohnnieB

Mathematically, going to 15:1 gears with 23" tires will loose about 9% in torque.
Tire height also changes final drive ratio, so 22" tires only loose 5% in torque and 20" tires actually gains 5%.

Wider tires will give you more traction and deeper dished wheels and/or stud extenders will give you more clearance, if needed.

With shorter tires, more lift will be needed for same ground clearance.

Like everything else about carts, it is a series of compromises.

ab46501

I'd try the tires first before doing a gear change unless you are pulling stumps or climbing extreme grades. Regardless of the actual % change the perceived torque feel is not that much different IMO.

archer161

Thinks for the info on the gears!! Do you have any specs if I went with the two speed axle from imaginative it has a 10.1 high gear and a 20.1 low gear???? That is using 23" tires.

JohnnieB

I have a spreadsheet that calculates tire circumference in inches from tire height (diameter) and divided that into the number of inches in a mile to get tire revelations per mile.
Then it uses the rear end ratio to determine Motor RPM per MPH, which in turn is used to calculate motor RPM for MPH from 1 up to 50.
Then I duplicated the calculations on another line for different tire heights and/or gear ratios, and calculated the difference as a %.

Mathematically compared to a stock 12.44:1 gears with 23" tires (About 13.5 MPH @ 2500 motor RPM)
10.0:1 will give you a 20% loss in Torque and gain in Speed. (About 17.5 MPH @ 2500 motor RPM)
20.0:1 will give you a 61% gain in Torque and loss in Speed. (About 8.5 MPH @ 2500 motor RPM)

archer161

JohnnieB that helps alot!!!!! That tells me that I'm going to have to spend more money next year!!! Oh, Does most motors turn 2500 rpms or was you just using that as a common??

JohnnieB

I was using 2500RPM as a common reference point.
How fast a series wound motor spins is determined by the voltage applied to it and how much torque it generates depends on how many amps it is allowed to draw.
It is about the same for shunt wound motors, but there are more variables.

On stock tires and a 36V battery pack, a stock TXT cart runs about 12 to 14 MPH, so the motor spins at about 2800 and 3200 RPM with stock gears.(12.44:1)
On the other hand, A stock PDS runs 18 to 19 MPH in Freedom mode, so its shunt wound motor spins at about 4400 to 4600 PRM.
(Note: The motor RPM is limited by the PDS controller - they will spin faster if the speed sensor is eliminated by using an aftermarket controller)

In either case, the max allowable (Safe) RPM is limited by mechanical factors (Bearings, Balance, structural strength, etc.)

archer161

I'm going to try to get my GPS out in the next day or two and just see what speed I have now. Its not fast, but I have alot of torque!! If I am able to get that info I will let you know were I can figure out how many rpm's I'm turning on my cart. Thinks for all the info. again

archer161

Update: I have installed my 22"tires on my cart with a little power loss, but not to much it will still go up the big hills so fare. The biggest thing I found was that I used my radar gun from my work and clocked my cart with 18"tires going 21 mph and when I got the 22"tires on it would only go 20 mph what gives???? I know it is suspost to go faster with bigger tires, but what gives with this!!!