Whinning Tire Noise From Friction Drives

Discussion in 'Friction Drive' started by Porkchop, Jul 15, 2009.

  1. Porkchop

    Porkchop Member

    This is a heads up for folks with friction drives that have not experienced this factor. I have about 200 miles on my BMP friction drive set up. My bike had semi aggressive knobby tires on it. When riding, it had an un Godly high pitch sound coming form the rear tire. I could barely hear the engine. I drove into my mom's drive way several days ago and she said it sounded like a siren.
    Anyway, I had a flat tire yesterday. Had already bought some spare tires several weeks ago. I decided to try one of my new, almost slick tread design tires on the bike while I had the wheel taken apart for flat repair. I just got through a 3 mile trip and no tire noise at all !!!!!
    Point being, for all that are new to this stuff, if you have a lot of tire noise and don't like it, maybe you need to change to a less aggressive tread tire or even a slick, which is great for dry concrete and asphalt anyway. A slipping rolleron a knobby tire will eat the knobs up in just a few seconds also. The smoother the tire tread the better the grip of the roller and the longer the tire will last. Not to mention now that I have no tire noise I can hear my Honda GX35 engine, it is surprising quiet.
    Hope someone finds this tid bit of info useful ! I know all to well about having to learn things the hard way.

    ..... PC .....
    Last edited: Jul 15, 2009

  2. Mountainman

    Mountainman Active Member

    hey PC
    yes sometimes we just need to learn the hard way
    I know that you are enjoying your new sounding THING soooo much now
    good the knobs are gone -- don't think they are great on the bearings either
    learning THINGS the hard way ?? hey -- sounds like me at times !!!

    as we all love to ride those THINGS
  3. Porkchop

    Porkchop Member

    This might be a little off subject, but then again, maybe not. Talk about luck ! Yesterday I rode for about 5 or 6 miles. Came home and parked my bike in the driveway rather than in the garage because I was going to take my lawn mower in there to work on it. Less than 5 minutes after parking the bike, I went to move it and it felt and sounded funky. I though maybe I had left the friction drive engaged. Not ! The darn thing had a flat. I looked and saw nothing in the tire. Pulled it apart this morning and it had a small slit on the inner side of the tube, the surface that's against the rim. The rubber band that covers the spoke nipples looks good to me. I didn't really bother to check if the hole in the ube was directly over a nipple or not. Who knows ? Might have just been something freaky. I replaced the tube with thicker aone that has Slime in it. Hated to replace my other tire, which is in great shape though. Then again, after hearing the noise difference, I'll probably never use it again. But I am big time glad and lucky the flat didn't happen while I was a couple of miles from home. To far and hot to push a bike ! Anyway, tire tread pattern can obviously make a big difference with friction drives.

    ..... PC .....
  4. Pirate88179

    Pirate88179 Member


    That makes good sense to me. My cruiser tires are what I would call medium tread...not aggressive but not really smooth either. Do they actually make a slick in 26"? If they do, to me that would be the way to go... more contact area as it would be more parallel to the roller it seems.

    I didn't get to order my drive kit yet.....waiting for more work to come in for more money. It is going to be a tight month either way it appears.

  5. Mountainman

    Mountainman Active Member

    it's a fine line !!

    more contact ?? better ?? not always

    because as we ride these little THINGS more and more
    we realize that the least amount of contact with out slipping
    is what we are in search of

    slight touch = faster
    crank that baby down too tight -- will notice the difference -- slower

  6. Pirate88179

    Pirate88179 Member

    That's because of the pressure from the distortion of the tire. If we had real slicks like back in the 60's on our bikes, we would have more contact area and much less pressure needed which gives less distortion and therefore less bogging of the system. I am speaking of the slicks that used to come on the Stingray. They had a flat surface and not a round profile.

    Here is what I could find for 26" slicks on the net so far:


    This is not what I was hopping for as these have a radius profile and not flat.
    MM, do you remember the real slicks I am speaking of?

  7. Porkchop

    Porkchop Member

    Pirate8817 and I talked about some of these issues last week. I'm not real savy on the co-efficient of friction equations, but I do remember a lot of it from college physics. You have square surface and pressure involved it. Why do race cars 99% of the time run slick tires ? Why do tires have tread in them anyway Why do drag race cars have wide tires on them ? I'm speaking in general freindy temrs here, not trying to open up a can of worms or anything. I know the answers to all those questions. Believe me, If I could find the slicks like Pirate mentioned, (which I remember quite well) with rounded transition from tread to sidewall, I'd definitely have them on my pavement pounder ! Not just because for the friction drive, but just in general. To me, it's no big deal. If my bike is dependable and gets over 100mpg, I'm happy
  8. Porkchop

    Porkchop Member

    O.K Pirate88179, after the conversations you and I have had in the last week or so, and reading your posts on this forum, I can see where you're headed. Looks like this forum has you hooked and reeled inlike the rest of us 'lil fishies in the deep blue sea ! Ha ! Ha ! Just going on with you a little. No offense. Welcome aboard. I'm still a newbie myself. Look how many times Moutainmoan has posted. I told hm before I don't see where he finds time to ride !!!!
    No reply necessary, but feel free to. Just polking you guys in the ribs a little !
  9. Mountainman

    Mountainman Active Member

    I remember those old time Stingray slicks all so very well
    my buddy way back in the sixties built up a 45 speed String Ray
    it was a cool little THING of a shift that THING all over the place
    rumor has it that the first Stingray was built by a father and son team
    right here in Hillcrest, San Diego
    Swchinn stole the idea
    gave the father and son team the first one off the production line for free
    gave it to them for free !! WOW -- what a special THING to do........

    inbetween these fun posts -- I still have plenty of time to ride those THINGS a lot......
  10. Pirate88179

    Pirate88179 Member

    Mountain Man:

    Yes, only a few lucky kids on my block had the Stingray and the rest of us wanted one, ha ha. I heard a similar story about its development. I hope it is not true but it probably is.

    So, does anyone make a flat slick like that these days? Even if I had to swap to 20" on the rear (it would lower it) would not bother me all that much. I have just not been able to find any on the net yet. I didn't notice what the newer Stingray's have on the rear. I just hope they are out there somewhere.

    I have read many of your posts while searching around this forum and I enjoy them. Be careful out there.

  11. Happy Valley

    Happy Valley Active Member

  12. Esteban

    Esteban Active Member

  13. Pirate88179

    Pirate88179 Member

    Those are close in that they have a flat profile but, the ones I remember (on the rich kid's bikes, not mine) had no tread on them at all...a real slick. Now, in today's sue happy society, maybe you can't offer a real slick because some kid might ride in the rain and get hurt. Is my memory correct about the one's in the 60's being real slicks? I could easily be wrong about this...what do you guys around my age (51) remember?

    This flat profile, in my opinion, would work better with the friction drive units out there. Either that, or they need to make a drive roller that has the same radius profile of the tire being used. Either way you get more contact area with less down pressure needed to drive without slippage.

  14. Porkchop

    Porkchop Member

    I remember them all to well. They were completely SLICK. No tread what so ever. Not worth a flip on wet ground of any kind, nor loose debris such as sand, gravel or loose dirt. They were great for slide outs though and leaving black marks on concrete drive ways and side walks ! Hee ! Hee !
  15. loquin

    loquin Active Member

    Bill - I'm not aware of any flat slick 26 inch tires. :(

    But... you do NOT want a roller that has a concave surface to 'match' the radius of the tire. At all.

    Here's the problem. If you have a roller that is 1.5 inch at the widest part, and 1.25 inch at the narrowest part, and it's placed in contact with the tire:
    the 1.5 inch portion is trying to make the tire rotate faster than the 1.25 inch portion of the roller at the same engine RPM ... about 20 percent faster!!!

    So, either the 1.25 inch part of the roller will be grinding away at the crown of the tire, or the 1.5 inch portion will be grinding away towards the sidewalls of the tire, or BOTH will be grinding away at the tire.

    In any case, your tire will be ground away soon, AND you'll be wasting a huge portion of your available power. Not a good situation.
    Last edited: Jul 24, 2009
  16. loquin

    loquin Active Member

    all other factors being equal, slick tires are the best on just about any kind of surface, wet or dry, for traction. They cannot hydroplane on a bicycle (unless you're running them at 15 psi or so.) On a BICYCLE, tread is NOT needed to 'channel water.' About the only time you would want tread is with snow (because as it compacts the snow, some will be forced into the tread, providing more traction.)
  17. Pirate88179

    Pirate88179 Member

    I see what you are saying but..I respectfully disagree. You are correct about everything you said except the part about them wanting to go different speeds. The tangent point of the largest diameter of the tire will be in contact with the smallest diameter of the drive roller, in your example, 1.250". The largest diameter of the drive roller, in your example 1.5" will be in contact with the area along the radius of the tire closer to the center point of rotation thereby making a smaller diameter tire. (effectively)

    I have not run the math on this but I think you will find that the reduced effective diameter of the rotating tire will be exactly compensated (equilibrium) by the larger diameter drive roller and will then be running at the exact same speed.

    As I see it, the real fly in the ointment here would be the unknown radius the compression of the tire, which we would need some for traction, that would be formed. In other words, it may not be possible to make it match exactly because you might push yours down just a little harder than me, or visa versa and I believe this would then alter the required radius.

    All in all it would probably not be worth the effort. And, you are right, if there is not a very good match with the cross-sectional radius of the tire, it would chew that tire up pretty fast.

  18. loquin

    loquin Active Member

    No, it won't be, Bill.

    With a friction drive, the diameter of the tire has ZERO to do with the final speed of the bike. It is essentially a transfer roller, between the friction drive roller and the ground... You could have a 1 inch diameter tire, or a 100 inch tire. The 1 inch diameter tire would be spinning at a furious rate, while the 100 inch diameter tire would be spinning at 1/100th the speed, but, the GROUND speed of the two would be identical. Speed calcs for friction drive systems depend upon the roller diameter and the RPM. And, that's all.

    Suppose you have a roller that's concave. (saddle-shaped) And, it's an extreme case, with the narrowest part at 1 inch diameter, and the largest diameter of the 'saddle' is 1.5 inches.

    You're running at 7000 RPM.

    The roller is spinning at the same RPM for both the two points on the roller, correct?

    This means that the linear (tangential) speed of the roller at the narrow point is
    7000Rev/Min * 1 inch * 3.14 * 60 Min/Hr * 1/5280 ft/Mile * 1/12 Inch/Ft = 20.8144 MPH

    And, for the wide part of the roller, at exactly the same RPM...
    7000Rev/Min * 1.5 inch * 3.14 * 60 Min/Hr * 1/5280 ft/Mile * 1/12 Inch/Ft = 31.2216 MPH
    Last edited: Jul 28, 2009
  19. loquin

    loquin Active Member

    If you take this argument to the extreme, assume a concave roller that's 1 inch in diameter at the thin part, and 26 inches in diameter at the wide part ... contacting a wheel that's 26 inches in diameter. And, 7000 RPM on the friction roller.

    The narrowest part of the roller is in contact with the outer surface of the tire, whereas the widest part of the roller would be in contact with the 'tire' 1 inch away from the hub center.

    The outer part of the tire would be spun at a linear speed of 20.8144 MPH. (and, at 269 RPM)

    But, the wide part of this roller would have a linear speed of
    7000Rev/Min * 26 inch * 3.14 * 60 Min/Hr * 1/5280 ft/Mile * 1/12 Inch/Ft = 541.17 MPH !!!

    So, assuming that a roller that's 26 inches in diameter, spinning at 7000 RPM, is trying to transfer that speed to a portion of the tire that's 1 inch in diameter. This means that the tire is going to be forced to spin at 26 times this RPM, or 182000 RPM.

    But, it's obvious that the tire can't be forced to spin at two different RPMs at the same point in time.

    I ignored the difference in the earlier discussion, as the difference in linear speeds between 1.5 inch and 1 inch rollers is 50%, but the reduction in tire diameter from 26 inches to 25.5 inches is only 1.9% less. The 50% difference in speed 'trumps' the 1.9% difference in speed.

    If the roller and the tire had the same diameters, and the narrow part of the roller had the better friction... The outer part of the tire would be spinning at the same tangential speed as the roller, but the outer part of the roller would be rubbing against a part of the tire that CAN'T move (radially in relation to the roller,) as it would be the hub...

    The picture below is a gearing analogy...

    Attached Files:

    Last edited: Jul 28, 2009
  20. Pirate88179

    Pirate88179 Member


    You make some really good arguments here and I will have to go back over your examples and think about this a while.

    I agree 100% that if your bike and mine are identical, same engines, rollers, rpms, etc. except yours has a 26" wheel and mine has a 20" wheel that we will still go the same speed. (This alone dispels my prior argument)

    The information and experience I was drawing upon was my 20 years in the precision machining industry. One of the many machines my company owned was an ID grinder that had a radius on the drive motor roller (It was a large radius maybe 8") but the roller was only 1" in diameter. It used a flat belt that drove a flat pulley for the grinding tool and it would spin at over 12,000 rpm. So, here we have a radius shape on a flat surface (the belt, 2" wide) and also a flat surface on the driven pulley and, that belt did not wear out or slip in any way.

    I am having trouble reconciling this personal knowledge of mine with your statements, all of which I agree with at this point. I will give it some more thought.

    It may all be a moot point in that, due to the flexible nature of the tire, the drive roller "sees" the tire as a mating flat surface anyway. In other words, if the tire were solid steel and still had the same shape, we would then have very little contact area between the drive roller and the "tire". But since the tire flattens out, as it does on the road surface, my idea for the radius matching roller amounts to nothing.

    I appreciate your responses to my posts and your explanations which I will re-read. My brain does not work as good as it used to, ha ha, but I am really getting into the MB stuff and I love it.

    Take care and thanks,