# Can a roller be fitted off-center?

Discussion in 'Friction Drive' started by mifletz, Mar 3, 2010.

1. ### mifletzMember

Does a roller have to be centered exactly in the middle? Can it be displaced to the side, or is centering critical?

<
2. ### professorActive Member

Think about it. Why would it need to be centered? Looks fine to me.

4. ### EstebanActive Member

I have seen plenty of friction drives working well with the drive roller up to 1/3 off center.

5. ### Happy ValleyActive Member

As long is it's not at an angle off-center.....IOW the drive spindle should remain parallel to the rear axle.

6. ### EstebanActive Member

I would believe that if is too much off center, outboard [ engine hanging farther away from bike ] it would cause more stress on the spindle & bearings.

7. ### loquinActive Member

You'll get somewhat increased friction (and associated wear) by having it tilted away from 90 degrees from the plane of the wheel. (On an angle, the tire in contact with the roller on the 'high' side is further away from the axle than the point in contact at the 'low' side. Essentially, you have two different radiuses...(radii?) Since both points on the tire HAVE to rotate at the same RPM, the 'High side' of the tire will be moving past the roller (relative to the roller axis of rotation) faster then the 'Low side' of the tire. This will lead to a scrubbing action, increased heat in the tire and roller, and increased wear.

That being said, if there was a 1/4 inch difference between the two radiuses, it would result in approximately 2% 'speed' difference between the two points. The more 'grip' the roller has on the tire, the more power you'll lose.

This difference in radius of contact is the reason why it's a bad idea to have a concave shaped friction roller.

8. ### mifletzMember

To what sort of pressure should a tyre for friction drive be inflated?

How deep should the roller be depressed on to the tyre: lightly or firmly?

9. ### darwinWell-Known Member

I had that same issue with my BMP/Titan kit and used washers to space it correctly with the u hanger. Tire should be towards the max psi that the sidewall says and the roller should depress the tire 1/4 to 3/8ths of an inch.

10. ### mifletzMember

The sidewall of my Continental "Town & Country" tyre says "inflate 35-65 psi". For normal pedalling 50 was enough for me. Will taking it to 60 bring any advantage when the roller is engaged?

Any disadvantages with a psi near the limit?

At what sort of psi will the tube blow?!

Staton in his instructions says "depress the roller 1/8" on to the tyre". Maybe that is not enough?

11. ### mifletzMember

Tyre pressure for roller drive

My Continental "Town & Country" tyre says "inflate 35-65 psi".

I have been advised to inflate it to 60 for use with a 7/8" Staton roller.

Is this correct?

At what pressure will an inner tube blow?

12. ### ut1205New Member

65 Psi

I have the same setup with a 1" roller. I run 65 psi with a Slime HD tube and a cheap tire. 300 miles so far on 95 deg July days to 30 deg Febuary days with no problems.

13. ### darwinWell-Known Member

Ive tried just an 1/8th and the roller slipped too much, just try it and see what works best for ya. As far as the tire pressure goes think about it. You need traction for the roller to work best, is a soft spongy surface better or a hard firm surface for the roller to drive.

14. ### loquinActive Member

The amount of deflection depends on the motor horsepower, the tire, the inflation pressure, the roller diameter, the rider's weight, and the road conditions.

I'm a big guy, and normally run at 50 psi continental Town & Country tire, a 1.25 inch roller (and the Mitsubishi TLE43,) and deflect the tire by about a quarter inch. If it's wet, you need to be light on the throttle, else it will still slip...

Note that a 7/8 inch roller will have more torque than a larger roller, so, you'll need more tire deflection (all other things being equal) than a larger roller.

Last edited: Mar 10, 2010