Grubee Gen III gearbox
- Thread starter FlyingSchwinn
- Start date
I bought several different sets from Century Spring Corp. in downtown LA. The problem with them is that they have a $40.00 minimum order requirement unless you are able to go to their will call desk and buy them. (No Minimum at Will Call) I first determined that the stock spring had a 40 lb/in spring rate, and then bought a set @ 47lb/in, a set @ 57lb/in. and a set @ 60lb/in. I ended up liking the 60lb/in springs. The part # from Century Spring is J-37 and they cost around $2.50 each and you need a set of three. They Have an on line Catalog at Precision Spring Manufacturer - Century Spring Corp.
ocscully
Thankyou Ocscully. Is the grubee gen III gearbox safe to run with the solid 10-tooth output sprocket as a replacement for the freewheel 11-tooth that comes with the gearbox as original equipment? Could the gearbox lockup running a solid output sprocket at the gear box to a solid sprocket to the rear wheel? Am I correct?: The grubee gearbox is a well-made, reliable unit, as long as you use the appropriate clutch spring rate @ 60 lb/in, always keep the engager in the engaged position and always keep that clutch bell bushing lubed with grease when you hear a clutch chattering noise. These questions are important to me because the price of this system is very good. I appreciate your detailed knowledge of the gen III gearbox. Thanks again.
There are currently two different clutches that work in the Type III gearbox. (See photo below) The narrow clutch and bell on the left in the photo is the one that came with the install kit when I originally bought it. The wider clutch and bell is the clutch that is offered as a replacement for the Type III. The Original clutch uses what is called a Garter Spring to control the engagement and and I was never able to find a source for stronger springs. The Newer clutch on the left uses compression springs to control the engagement. These are the springs that I was able to purchase from Century Spring Corp. (See the link in the PM I sent for more photos and info.)
I had 6000+ miles on my Type III gearbox when I found that I needed to replace the clutch. I bought the newer Replacement clutch from bicycle-engines.com and had some trouble getting the new clutch to work to my satisfaction. So I have switched to one of the 4G Drives for the Honda Motor that uses the newer style clutch but with a different clutch bell that has a 20t Metric Timing Belt Driver rather than the spur gear. I like the newer 4G Drive better than the Type III. The 4G has its problems but it is much quieter and smoother than the Type III. The 4G does not have the engager mech. to deal with either. Though I've never used one of the Grubee 10t fixed output sprockets. I've always had the 11t output freewheels welded up solid at a local fabrication shop. But my bike and motor set-up uses the SBP 4-stroke Shift Kit so there is still a freewheel mech. between the rear wheel and the output from the Drive unit. In fact there are two freewheels one for the crankset chainrings and then the one at the rear hub.
If the lower price is important to you and you don't mind doing a bit of tinkering/fine tuning The Grubee Type III will provide you with alot of fun miles. But if you would prefer not have to tinker and fine tune then You might want to give some thought to the EZM Q-matic Kit.
ocscully
I had 6000+ miles on my Type III gearbox when I found that I needed to replace the clutch. I bought the newer Replacement clutch from bicycle-engines.com and had some trouble getting the new clutch to work to my satisfaction. So I have switched to one of the 4G Drives for the Honda Motor that uses the newer style clutch but with a different clutch bell that has a 20t Metric Timing Belt Driver rather than the spur gear. I like the newer 4G Drive better than the Type III. The 4G has its problems but it is much quieter and smoother than the Type III. The 4G does not have the engager mech. to deal with either. Though I've never used one of the Grubee 10t fixed output sprockets. I've always had the 11t output freewheels welded up solid at a local fabrication shop. But my bike and motor set-up uses the SBP 4-stroke Shift Kit so there is still a freewheel mech. between the rear wheel and the output from the Drive unit. In fact there are two freewheels one for the crankset chainrings and then the one at the rear hub.
If the lower price is important to you and you don't mind doing a bit of tinkering/fine tuning The Grubee Type III will provide you with alot of fun miles. But if you would prefer not have to tinker and fine tune then You might want to give some thought to the EZM Q-matic Kit.
ocscully
Attachments
Thankyou FlyingSchwinn for starting this thread. Thankyou Ocscully for answering my questions. You explained everything very well. It's probably going to take me at least 3 and 1/2 years before I can answer other people's questions. Ocscully, I appreciate the time you spent answering my questions so thoroughly. I'm getting a real good attitude about the people here. I'm receiving more than mechanical knowledge, thanks again.
MotoMagz
Well-Known Member
I ran the 10t non freewheel with my stage III and it is alittle harder to pedal.Once I attatched the Shift kit pedaling was back to normal.I also switched to the 4G and like Ocscully said it is much better but does have a few issues.
Dan
Staff
Ayup, some really great folks here. Not to ramble but a good while back Oscully took great time walking me threw how to figure out gear ratios. Was a whole lotta typing and answering. Is a great resource knowing him and the many fine folks here and a pleasure to enjoy the just "hanging out"
