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Friday, September 25, 2009

Slick Tires Installed

Today was not a good day at all, so I did not get any of the testing with the old tires redone. By the time I was done being frustrated by life, all I felt like doing was installing the new tires to see how they work, so that's just about all I did.

I didn't fix the rightside rear axle-nut clearance problem, so I still have to take the rail loose to put it on or take it off. I think I'm going to go with the hole thru the cargo pod and rail to get to it--it's the easiest to do. Whenever I have a day where things are going better for me and I am not afraid I'll totally screw it up. :-(

Here are the new tires, on the bike:

If I had any spray paint, I'd give them white sidewalls. Since I don't, I'm trying to remember where I put the latex wall paint that's off-white, and I'll use that, even if it peels off later--the visibility factor of light colored sidewalls is large enough I want it back.

Here's a shot of them with some dirt on the treads, so you can see the contact area they have rolling over dirty pavement. Nice and wide area, compared to the MTB types.

Closer shot below:

Also shows the brakes, which need readjusting again.

Speaking of brakes, here's a shot of the rear wheel with new tire, plus the brake arm extensions I had to make:

The arms fit the 26" wheel fine, but they are about 1/8" or more from being long enough to hold the pads on the 24" rim without rubbing the sidewall even if I have them properly installed, before engaging the brake!

So I cut the slotted tabs off a set of bent up calipers off some junked bike and bolted these tabs to the existing arm tabs at an angle, giving me just the right positioning of the pads.

The pads are at the funky angle when not engaged because the downward force on the calipers is so strong that at speed if I brake hard the calipers are pulled downward at their wheel ends so far the pads would tear into the tire if I didn't do this. As they are, they end up gripping the rim perfectly once engaged, and angle normally to the rim.

I had tried some retaining tabs bolted to these tabs, with a hook that went up and over the frame stays above, but when I braked hard they just bent, slipped over the frame, and jammed the brakes against the rim so I had to actually unbolt the pads to get the jam cleared. So I'll live with the flexing until the calipers break off at the swivel/mounting bolt or something.

I like the feel of these tires a lot better than the old ones. It sort of feels like they might be doing better shock absorption, but I think it's probably just because I don't have any of the knobbly vibration I did before. It's especially noticeable in turns, because of the front wheel now being a smooth curved surface instead of rows of rubber rocks, basically.

Since I couldn't do any scientific testing today, I took some photos of the side-view of the contact patches for the various tires I had on the bike. They're not all on the same rims, since I didn't want to unmount the bike's wheels with the new tires just for this.

Front new tire:

Rear new tire:

Old front tire from powerchair:

Old MTB/road hybrid tire:

Original "roadmaster" wheel tires I started with:

26" Cheng Shin I use on my upright bike, which was in use on Crazybike2 for the rear most of this month until today.

That's it for today, except to report that I kept having the pedal chain come off and get jammed up in the rear sprocket during all riding today, about every few hundred feet, to the point where I finally got frustrated and just tied it up out of the way and used the motor for everything instead.

The problem is getting worse, but I cannot see *where* the slackness is coming from:

  • There's no additional wear measurable on the chain at any point; I cannot see a difference between it now and when I marked it on the tape for making it up when i redid the frame.
  • The chainrings don't seem any different, but I can't really measure those. Photos appear the same when I compare them.
  • The frame itself does not appear to be bending or shifting, but I didn't do any accurate measurements right after the modifications to compare to now; it's just a by-eye thing.

The motor chain is not having a problem at all, just the pedal chain. And I can't see the mechanism by which it is being popped off, either, as it happens at random times, with no one thing causing it.
  • I can hit a pothole or a bunch of bumpy road and nothing happens, but later if I am just cruising BAM it pops off, even with no change in speed, torque, etc.
  • I can shift gears one time and it'll pop off, but the next shift doing the same thing doesn't do it.
  • Pedalling harder than the motor is spinning (which puts tension on top of the chain and loosens the bottom) doesn't make it happen any more often than running the motor without pedalling at all (which forces tension on the chain along the bottom and loosens it on top).

So I'm stumped; I only know that it always happens at the rear end of the pedal chain, not the front. I'll have to put a chain tensioner back on to stop it from happening, because this sucks.


  1. My chain pops off and gets jammed between the small end of the rear cassette and the frame. The dérailleur seems a bit defective because it is so stiff, mainly. I did adjust the limit screw on the dérailleur, which probably helped, but it is hard to say for sure since I haven't been slamming the dérailleur over to the highest gear anymore.

  2. Unfortunately in the case of my pedal chain, there is no derailer to adjust; it is just a straight unshifted chain.

    Something in the changes to the frame to open up that middle section must have misaligned it, and brought the tension down just a bit; I just can't see what it is to fix it. Instead, I'll have to put a tensioner on there again (adding noise).

    If I had a half-link, it might fix the problem by shortening the chain the other 1/2 link. I'm not certain there is a full half-link worth of extra chain I could take out to do it, though.

  3. As to the stiff derailer, does oiling it make any difference? If not, try taking the cable and chain off and see if it moves freely then. If it does, it's probably your cable sticking somewhere in the path, possibly from a kink in the cable or shell.

  4. I had a problem like that and the only way I found it was by putting the bike on blocks and manual spinning it over for a while. Eventually I found a spot where the two gears had teeth that were just a little bit too much out of line and the chain would pop off now and then... maddening problem!..... Bent one of the gear teeth over just a little and the problem stopped went away.

  5. Yeah, neither of these sprockets is the straightest, but it's not a single-tooth kind of problem; rather the whole thing is more like a warped record. :-/

    I already tried straightening them out long ago, but to little result. Even so, they weren't a problem until now.

    I'm really thinking the frame is twisting just a bit under some circumstances, less than I could notice, and causing it.

  6. I should do that instead of just putting up with it. I might have tried those things but forgot what I found.


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