View Full Version : GPR-S in Australia?

27 May 2013, 2256
Hey all,

I've been lurking for a couple of weeks, soaking it all in, and was wondering why no-one seems to be using the GPR-S chassis as the base of their build?

It looks great to me, so much easier than trying to coerce an internal combustion chassis into working properly...

Has anyone imported one of these and put their own batteries/controller into it?

Any info would be appreciated.

28 May 2013, 0728
I owned two GPR-S production bikes before I bought my Zero. I thought the chassis was workable for the garage tinkerer. The chassis is very mild steel and everything is assembled with hardware-store quality bolts. The chassis is easy to disassemble and reassemble with just a few cheap hand tools and it manages to roll down the road reasonably well. However, I wouldn't want to force the bike to exceed about 70 mph, as it starts to wiggle around that speed. The shocks, forks and brake components look fancy, but work like they were made Thailand - which they were, like everything else on the chassis, including the tires. The chassis is well designed to accommodate prismatic batteries and associated electronics and I think the bike would be much easier to just drop EV stuff into, compared with trying to do the same thing with an IC motorcycle chassis. You will end up with a nice little 250-class Asian-designed EV that is easy to construct, but it may cause confusion with the local DMV when it comes time to register it for the road.

28 May 2013, 1408
One other comment about the GPR-S that I just recalled. The swingarm (at least on my bikes) had a brace that extended below the main swingarm rail. That brace can get in the way of the chain run, depending upon the size of your rear sprocket. On my sepex bike, Electric Motor Sport cut the left side of the brace off in order to make clearance for the chain. Attached are some photos of my 2009 model partially dismantled.

28 May 2013, 1424
Here are a few more photos of the GPR-S chassis. These show how the battery boxes are installed in the frame and also show the cut swing arm brace on the left side of the bike.

28 May 2013, 1530
Thank you so much Richard,

That helps immensely. The pictures are especially illuminating :-)

04 June 2013, 1918
I have two GPR-S's and it was a good chassis for the time. It was always challenged for space and unable to fit enough cells to get a competitive range compared to Zero or Brammo's base models. The placement of the motor at the bottom center instead of up & behind the rider means that it takes up valuable battery space. The chain is also unnecessarily long due to that.

The shocks are on the weak side as Richard mentioned. The stock 300 lb configuration + 170 lb rider is on the edge of the shocks' capability. The GPR-S that I retrofitted with 80Ah worth of LiPo cells probably weighs close to 350 lbs and the shocks bottom out going over moderate bumps at speed.