I have an old 7300 Trek hybrid - needs gears
05-21-08, 07:56 AM
#26
Senior Member
Hey bob, a quick way to check how bad your old chainrings are is with a new chain (you changed yours recently so this will work) try to pull the chain away from the sprocket along the front of the chainring. A new chain on a new ring will only let you pull the chain away from the sprocket by maybe a millimeter. A badly worn chain and ring will let you pull the chain up away from the curve of the sprocket by ...*shudder*.... as much as 6 mm or even more. It's skip city or very close to it at that point. A new chain on a badly worn sprocket will indicate only the wear on the teeth since the chain is new and presumably in spec. I would consider the ring teeth to be worn past using if I could lift the new chain away from the gullets by 3 mm (1/8 inch).
We can get away with a lot when we're only dealing with about .2 to .25 hp from the "engine" but worn rings used on a new chain will certainly accelerate the wear in the new chain. That accelerated wear of the chain will then accellerate the wear on the new cassete. So in the end if the setup is truly worn as badly as you say then it could well be false economy to try to get away with the old rings. But this is a feel thing that is hard to judge over the net sight unseen. But from what you've described it sure sounds like it needs the whole enchilada.
And to confirm about the square taper question since I didn't see a definite reply above if youi pulled out your crank bolt and saw a square looking back at you then yes you do have a square taper setup. The one you linked to is a rather heavy and clunky unit as already mentioned but just as importantly you can't change rings on it at all. For a little more money you can get a much nicer setup that comes in a variety of ring options. Just be sure to match the arm length to what you have now.
https://www.jensonusa.com/store/produ...+Crankset.aspx
We can get away with a lot when we're only dealing with about .2 to .25 hp from the "engine" but worn rings used on a new chain will certainly accelerate the wear in the new chain. That accelerated wear of the chain will then accellerate the wear on the new cassete. So in the end if the setup is truly worn as badly as you say then it could well be false economy to try to get away with the old rings. But this is a feel thing that is hard to judge over the net sight unseen. But from what you've described it sure sounds like it needs the whole enchilada.
And to confirm about the square taper question since I didn't see a definite reply above if youi pulled out your crank bolt and saw a square looking back at you then yes you do have a square taper setup. The one you linked to is a rather heavy and clunky unit as already mentioned but just as importantly you can't change rings on it at all. For a little more money you can get a much nicer setup that comes in a variety of ring options. Just be sure to match the arm length to what you have now.
https://www.jensonusa.com/store/produ...+Crankset.aspx
05-23-08, 06:44 PM
#27
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took the 7300 to my LBS and did the works!
Hi all, thought i'd give you'all an update since you all have been so helpful and encouraging!
I kept trying to figure out what parts to buy and it almost seemed impossible to find and or figure out what i really needed, so i just took it on down to Spokes in Vienna Va and had a new Shimano cassette, and crankset, including new spindle put on for 163.00 and to my suprise, i forgot that i had a 25$ credit from a year ago! so that really made my day and plus, the good fellow did it all in 3 hours...wow!
And i also forgot that had put a new double hull wheel on it several years ago with less than 50 miles on it, so i'm pretty pleased with the package now!
So what i'm going to do next is put on some 28cc tires that i bought several years ago as well and see how that makes a difference if any and use it as a "road" bike for long runs as well maybe.
Anyway, it's good to have 2 trusty 7300s ready to go on the spur of the moment, so happy Mday all and thanks again for the very thoughtful help!
BobK
Fairfax Va
I kept trying to figure out what parts to buy and it almost seemed impossible to find and or figure out what i really needed, so i just took it on down to Spokes in Vienna Va and had a new Shimano cassette, and crankset, including new spindle put on for 163.00 and to my suprise, i forgot that i had a 25$ credit from a year ago! so that really made my day and plus, the good fellow did it all in 3 hours...wow!
And i also forgot that had put a new double hull wheel on it several years ago with less than 50 miles on it, so i'm pretty pleased with the package now!
So what i'm going to do next is put on some 28cc tires that i bought several years ago as well and see how that makes a difference if any and use it as a "road" bike for long runs as well maybe.
Anyway, it's good to have 2 trusty 7300s ready to go on the spur of the moment, so happy Mday all and thanks again for the very thoughtful help!
BobK
Fairfax Va
