going up Ophir isn't really that steep.....but I'd still go +3 in back and do the 15t in front - just because I like to argue let's see a picture going up Imogene's last climb to the top from the Telluride side... that could probably use a 14
http://www.cafehusky.com/threads/my-ride-down-the-continental-divide-on-a-terra-650.35093/ In my ride report I talk about my views regarding the 15 and the 16 tooth counter sprockets. As FAB mentioned above it is an easy swap to do for the riding conditions you want.
I'll work on that. The problem is that no one I ride with in these circumstances carries a fricken camera! I can't wait to get back to all those passes. There were a tone of roads to explore above timberline in that area. A good place to be with the Terra! Though the 511 might be a better choice for some of that. A perfect gear match that you and HF are working up is probably a good idea, but I will remain flexible.
I plugged these number into gearingcommander.com With the stock chain 14T will extend the wheelbase by about 10mm, whereas the 15T/50T combination will reduce the wheelbase by about 10mm from stock, or 20mm less than the 14T but with the same net result on gearing. I'm guessing reducing the wheelbase will give better control than increasing it.
Thanks for the replies. Good info Highfive. I decided on the 15T. When the rear needs replacing I may go up 2 or 3. I installed a Booster Plug at the same time so I'm sure that accounts for some of the improvement I'm seeing. One thing I did notice was that before the gearing change, 4000rpm in 5th gear was 60mph on the bikes instruments and 58mph on the GPS. After the gearing change, 4000rpm still shows 60mph but the GPS indicates 62mph. Does that make any sense? I've been thinking about this for awhile.......and I've got one helluva headache.
Well, we've been assuming that the ABS sensor at the rear wheel does speedometer duty. Maybe RPMs are still used for speedometer duty? But then what the hell is the ABS sensor used for on non-ABS bikes? You could possibly try disconnecting the ABS sensor at the rear wheel temporarily just to see what happens.
While I've not exhaustively studied the speedometer sensor, mine works fine coasting downhill with the engine off, so I doubt the rpms have anything do do with the speedometer.
Attempting to calculate speed based on RPM is too complex because you have a gearbox in the mix. The two logical measurement points are at the wheel, or at the countershaft.
The gearbox just adds a multiplier to the calculation, not very complex. But, I meant the countershaft, which would be similar to a car. I refer to it as rpm since it's directly proportional to the rpms, is all. I still think the abs sensor is doing the job, and was just offering possibilities of explaining why the gps/speed relationship may have suddenly changed. But, likely something else entirely.
I think the cause of the illusion that the speedo/tach has not changed with the gearing is because with 16T 4000RPM =58MPH and with 15T 4000RPM=62MPH. At 60MPH the needle should be pointed either 130RPM north or south of 4000RPM. Given the crude gradient of the tacho dial, with both gearings the needle will be pointing more or less at 4000RPM.
Just got back from a little ride trying to figure out the speedo, rpm, GPS relationship. So yesterday, after changing to the 15T, my instrument readings were 4000 rpm, 60 mph with my GPS showing 62. Today I was expecting the same thing. What I got was exactly the same readings I was getting before I changed the countershaft sprocket. 4000rpm, 60 mph and 58 mph on my GPS. Before I left I zero'd out the trip meter and the GPS. Both showed 34.6 miles traveled. If I had any, I'd be pulling my hair out by now. Maybe the NSA is messing with GPS signals as well as my phone calls and emails.
So... Can I get away with swapping out the 16T to a 15T without adjusting the rear wheel? Looking on gearing commander, the distance between sprockets only changes 3mm, I'm only a layman when it comes to these things, but is 3mm enough to warrant adjusting the rear back? I think the problem might stem from trying to remove the sprocket with the chain in place.
The links are 5/8" apart, so yes if you go from a 16 tooth CS to a 15 tooth CS your chain would have 5/16" more slack in it. But most of the bikes, or at least mine, seem to need more slack than it actually has as more load is placed on the bike.
49/15 = 3.27 ( 11.2% increase ) The stock gearing is just a bit too high in 1st gear, for my taste. It needs a bit more torque off the bottom, and I think a 4% increase ought to be the ticket. Seems another inmate tried this and was very happy with it, but I don't recall where I read it. Shouldn't hurt the top-end cruise at all....might actually improve it, giving it a little more pull in 5th gear against a headwind. That's not such an issue until you're running the slab with packed saddlebags catching a lot more wind resistance. I MATCH 100% your experience at low gear, very long ratio in firts speed. as soon as you have installed 49/15 i will be glad to hear news. next chain change i will look fordwards this ratio.. i think is the best oof road.. I wonder how will be the top speed then??
I put a 15 tooth on yesterday and tried it today. As far as I'm concerned this is the way the bike should have come stock. I found that I was either too high in one gear and too low in another before. With the 15 the ride was just better. Not over or under revving and power always right there when you need it. Taking off from a stop is improved too. I was afraid that the gearing may have been too low but it was just right. With the 15 and the throttle adjusted this bike is so much nicer to ride!
Well, I got the 16T off and the 15T on without touching the back axle, but it put a heap more slack in the chain, way more than 5/16". The chain is now sitting on the swing arm when it's on it's stand in Neautral. You can push the bottom half of the chain up to hit the swing arm without a problem. A little too loose I think.
