View Full Version : Top speed?

21 February 2011, 1452
I'm wondering what others have for a top speed. Here's my set-up:

D&D ES-15-6 (series, claimed 65 ft-lb, 30 HP peak))
GBS 72V, 60Ah (usually sits around 78-80V)
Alltrax 7245 (450A)

I had it geared 5:1 and it topped out a bit under 60. I just switched to 4:1 and it only gained a few mph. Based on the motor spec, it should go over 4000 rpm, which is 70+ mph with 4:1 gearing. At 60 mph and 4:1, I calculate 3300 rpm...which seems kinda low even for this motor.

So I'm guessing I'm just hitting a HP peak no matter what gearing I have. Curious what others have and whether I should expect a higher top speed, or how I could get there.


Nuts & Volts
21 February 2011, 1503
I have hit 65/70mph (speedo is 5mph-ish off) and will verify with a GPS this spring. That is with 72V 60ah GBS and an agni geared at 5:1, batteries sag to about 70V and 160A.

I don't think you are hitting a HP rating, but maybe. What is your voltage and amp reading at top speed? That will tell you your HP and the voltage sag may be affecting top end.

21 February 2011, 1505
I think your numbers are realistically close at 70mph. I am running 4.14:1 and have done 72 on a long stretch of VA race track. The voltage drop due to battery type/ weight of bike and rider/drag coff will be the variables on whether you get there or not.

21 February 2011, 1508
I think RPM quoted is typically no load. I figured that the D&D Sepex I'm using is rated at 4500rpm @ 72V, but I'll be running 80V. I can't remember the RPM I finally used to calculate top speed, but I'm aiming around 70mph. It's all guess work until I'm on the road though. And my calculations didn't account for voltage sag as N&V points out. I'm going to start out at 4:1 and go from there.

21 February 2011, 1526
My D&D sepex GPR-S, with 24 Hi Power 50 Ah batteries with 80 volts maximum would get up to an actual 62 mph on level ground - when it was new and running at its best. I did once get it to 70, but that was down a long hill. Maximum amperage draw was typically 175 amps at 50 mph, which would drop to around 120 amps as the bike neared its top speed. My estimate of the power output, based upon extensive experience riding low-power IC motorcycles, is that it was making about 6 to 8 hp at the time. Attached are a couple of photos of my motor showing the model number.

I might add that, when purchased, my speedometer was set up to read 8 mph faster than my actual speed and I had to recalibrate the speedometer to get an actual reading. See my recent thread of how this is done.