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General Category >> Rubber Side Down! >> Chain conversion and Schwinn speedo... error
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Message started by Rockin_John on 08/22/08 at 21:39:19

Title: Chain conversion and Schwinn speedo... error
Post by Rockin_John on 08/22/08 at 21:39:19

Hey folk, finally got my 17:43 chain conversion on, and after a couple hundred miles with it in town and on the highway I couldn't be happier with it! I went with the steep 17:43 instead of the lower 17:45 despite my 250+ weight; because I was pretty sure the thumper could handle it on takeoff, and I wanted it to putt along nice and lazy on the highway. All has worked out just fine so far, and I don't see any problem loading another 50 pounds of gear for traveling (which I usually go pretty light on what I haul when traveling).

I went ahead and splurged on a cheap eBay o-ring chain and ended up with a bit over $100 in the conversion. On top of the conversion I've just added new tires and maxed out the rear tire size.

Now I'm awaiting my National Cycle 4.5mm Dakota windshield and I'll be about halfway home to a long haul road version of the Savage!

One thing still has me vexed though: In an attempt to keep my speeds reasonably legal, I added a Schwinn digital speedometer, and it seems to be good up to about 40-mph or so; then the readings go all whacky.

It never ever shows anything over 60mph, like it is stuck in the high 50s even when I'm passing everything on the expressway... (probably running 80mph). I don't know what to think, I've moved the magnet and pickup around a couple of times, and triple checked the math on my wheel diameter input, and nothing seems to help? Anyone have a clue as to what I might be doing wrong? Or maybe I go a bad speedometer unit?

TIA to anyone who can help with the speedo!

Title: Re: Chain conversion and Schwinn speedo... error
Post by verslagen1 on 08/22/08 at 21:51:30

Is it reasonably accurate up to it loses it?

My guess, move the magnet closer to the pickup or get a stronger magnet.

Title: Re: Chain conversion and Schwinn speedo... error
Post by Rockin_John on 08/22/08 at 22:07:09

5A495E5F404D4B49421D2C0 wrote:

Is it reasonably accurate up to it loses it?

My guess, move the magnet closer to the pickup or get a stronger magnet.

I don't know how accurate it is at lower speeds... just guessing I'd say it is reading slow at low speeds.

I can't get the magnet much closer, it's within about 1/8" now... Maybe I will try the stronger Rat Shack magnet thing, but I don't think proximity is the problem. Dunno though, I'm at a loss. :-?

Title: Re: Chain conversion and Schwinn speedo... error
Post by Skid Mark on 08/22/08 at 22:14:37

Mabe check the wire for dammage. Its thin and could be dammaged easily.

Title: Re: Chain conversion and Schwinn speedo... error
Post by youzguyz on 08/23/08 at 02:09:53

This may sound obvious, but what is the range of that Schwinn speedo?
If it never goes past 60, maybe it's because it can't!!!
I know the Sigma's will (at least mine did), but that doesn't say all of them go that high.
After all.. when was the last time you saw a bicycle doing 40mph?

Besides that, the suggestions made by others are good ones.

Title: Re: Chain conversion and Schwinn speedo... error
Post by Rockin_John on 08/23/08 at 05:52:37

30263C332E3C3033490 wrote:

Uhh... Yeah I checked that before I bought it! :D

Supposed to be good for 99.9kmh or 99.9mph depending on setting.

I'm gonna try the "bigger magnet" theory; because I don't know what else to do. If that doesn't work, I'll take it back and tell them it is defective. ;D

Title: Re: Chain conversion and Schwinn speedo... error
Post by verslagen1 on 08/23/08 at 07:02:21

7F69737C61737F7C060 wrote:

I have done at least twice, once in a group ride (100 mile round trip, the posted speed was 40, chippies pulled us over gave us a warning) and once solo for an hour (yep one L of a tail wind) :o

Title: Re: Chain conversion and Schwinn speedo... error
Post by Sandy Koocanusa on 08/23/08 at 07:04:19

When I first mounted my Schwinn speedo, it would read up to 80 or so (as fast as I had taken it to that point) no problem. Then I switched the front wheel and remounted the magnet. Now it does exactly what you are describing at about 75 mph. I had trouble mounting it on the new spokes, which are a little thicker and slicker. I think it's placement of the magnet. One of these days, I'm going to try a stronger magnet. I think that will do it. Let us know if you try it first.

Title: Re: Chain conversion and Schwinn speedo... error
Post by verslagen1 on 08/23/08 at 07:08:24

How about flipping the magnet over?

Title: Re: Chain conversion and Schwinn speedo... error
Post by Rockin_John on 08/23/08 at 08:28:56

475443425D5056545F00310 wrote:

How about flipping the magnet over?

I thought of that one too... maybe it was a +/- "pole" thing... Didn't make a diff.

I'm gonna try the rare earth magnets from RAT SHACK, and if that doesn't work; I'll leave them installed; return the Schwinn to Target, and find a bike shop with a Sigma.

That should fix it.

I'd sure like to know how fast I'm thumping along with these new sprockets. Feels like 80-85mph when it sounds like 3-3.5k RPM! I need to hook up my clamp-on inductive tach temporarily when I get an accurate speedo working. I'm curious as heck to see if all my gearing and tire size math is anywhere near the real world numbers.

Title: Re: Chain conversion and Schwinn speedo... error
Post by 1st2know on 08/23/08 at 11:06:49

Where on the wheel is the magnet mounted?

The closer to the axle, the slower the speed of the magnet, making it easier to register - if it's - say near the spoke nipple, it will fly by the sensor, perhaps not registering as often. The computer is going to sample for signal so many timer per second - each time, it will sample - (true or false) - if false, it probably assumes that the magnet hasn't made it around yet - in that split second that it's not sampling the magent can wiz by.

Putting it close to the axle may help at hwy speeds, but may disrupt readings in town.

Or, print this topic off and keep it with you - when the cops pull you over and ask you why your'e speeding - hand 'em this thread - I'm sure they'll understand ;-)

Title: Re: Chain conversion and Schwinn speedo... error
Post by Rockin_John on 08/23/08 at 14:15:46

I've got my sensor close to the axle, and was running the magnet in the depression on the disc side of the wheel. I guess even at 1/8" away it didn't like the little magnet that came with the unit.

Rat Shack didn't have any of the "rare earth" magnets in stock anywhere in town; but I bought some of the rectangular ceramic magnets and 3M high temp double sticky tape. (Lost one magnet because it wouldn't hold itself.)

So far it is reading good up to 75-80mph. (Done on the service road to the expressway, and no sooner did I let off the throttle than a cop pulled off a side street going the other way on the two way service road. Avoided a ticket by || much! I'm surprised the popping of the Supertrap didn't make him turn around, but he let it go... Whew!!! :o 8-)

Anyways, thanks for the suggestions folks, it seems to be working now, if I'll just pay attention to it and behave myself! ;D