View Single Post
Old 06-16-2008, 10:08 AM
HoughMade's Avatar
HoughMade HoughMade is offline
Motorized Bicycle Elite Member
Join Date: Apr 2008
Location: Valparaiso, IN
Posts: 624
Default Re: Grubee Gearbox- run it with lube!

Originally Posted by Pablo View Post
Sounds interesting and promising. I love stuff like this - nothing like garage trial and error with lubricants. I have not seen this gearbox, nor do I know the design - so I am not an "expert".

I know lubes and greases pretty well, so I will just say a few things/ask a few questions.

1) For wear protection the brand of "stop smoke" may matter. Some do have antiwear agents, some are just very heavy so called bright stock base oil with viscosity improvers (thickeners). In some gearboxes this VI may shear (thin) permanently.
Thanks- good info. What brand would you suggest?

2) Why didn't this gearbox come with fluid in the first place?
The "instructions" with the gearbox state that it can be used wet or dry. They also say that if you want to run it wet, use engine oil. Several people have tried it and it has not worked for them. This method is suggested by a vendor who sells this gearbox (bicycle-engines) and has been used successfully by my friend for a while.

3) What type of grease is recommended?
No specific grease was recommended, but I had been using Lucas X-tra Heavy Duty (pretty green color).

4) Does this gearbox get hot with use?
Warm- yes, hot- no. My differentiation between the two is whether I can put my hand on it without pain...the answer is yes, but I don't have near the nerve endings I used to.

5) What is the exact design of the clutch? Does grease normally get on it?
See the pictures below, a few picks of the setup.

5) There are SAE 250 gear oils made, that have huge room temp viscosity, even at 100C the viscosity is over 500 cSt. Then no need for the 50% thickener, which in my opinion could possibly lead to early gear wear - I'm not saying his with any certainty, but it's something to be considered. OTOH an SAE 250 gear lube may not be right at all for the clutch. Lubrication can be a series of compromises.
Indeed, good info. Thanks.

Lemme know - again - not trying to scare anyone. It's just my mind I can't control… just gets to racing when lubes are involved!
Thank you- I'm always up for improvements, but people have thousands of miles with grease and with this mix- but that does not mean we can't do better!
Attached Images
File Type: jpg centrifugal-clutch-kit.jpg (30.0 KB, 311 views)
File Type: jpg gear-box-example2.jpg (9.6 KB, 491 views)
File Type: jpg gear-box-example.jpg (8.2 KB, 199 views)
29/10ths cubic inches of raw power.
HoughMade at
Reply With Quote