Trek 7500 parts question
09-03-21, 02:34 PM
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Trek 7500 parts question
My Trek 7500 is about 25 years old. I haven't ridden it much these past few years but resurrected it after crashing my road bike. I replaced the tires and have ridden it a few times now. I noticed in a couple of gears there seemed to be a slight hitch and the chain or something would skip when I went over a bump. I brought it to the bike shop and the guy said the chain and cassette appear to be working fine and it's shifting ok and his best guess was the spring in the derailleur was weak. He said to live it if possible as the parts they have now are no where near the quality of the original.
So my question is, is the original Shimano Deore derailleur and 7 speed cassette still available for the bike? If not are any aftermarket parts more reliable and better than others?
Are people out there still riding their Trek 7500? I asked the guy if a modern fitness bike would be that much better and he said not as much as you'd think as the 7500 was a really good bike.;
So my question is, is the original Shimano Deore derailleur and 7 speed cassette still available for the bike? If not are any aftermarket parts more reliable and better than others?
Are people out there still riding their Trek 7500? I asked the guy if a modern fitness bike would be that much better and he said not as much as you'd think as the 7500 was a really good bike.;
09-04-21, 07:16 AM
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I agree with the bike shop that a modern bike today won't be a big step up from your 7500, but I don't necessarily agree that modern parts aren't as good as they were back then. The original derailleur model is not made anymore, but you can get stuff that'll work very well. The Shimano Deore RD-M591, available in both black and silver, may be the closest version of what's commonly available new today. It's designed for a 9-speed drivetrain, but should work well with your 7-speed configuration. Of course, you can get new old stock or used parts on eBay and other sites as well, but you take the risk of getting something that's just as worn out.
That is, if your rear derailleur is truly worn out. We may be able to help you troubleshoot if you can give us some more details. When does the chain feel like it skips? Only after a large bump...and does it happen in any gear combination? Chains will flop around some after bumps, moreso if the derailleur springs are weak...this is true. Does the derailleur feel tight to you when manipulating it by hand, or do you agree with the shop that it feels too loose or floppy?
That is, if your rear derailleur is truly worn out. We may be able to help you troubleshoot if you can give us some more details. When does the chain feel like it skips? Only after a large bump...and does it happen in any gear combination? Chains will flop around some after bumps, moreso if the derailleur springs are weak...this is true. Does the derailleur feel tight to you when manipulating it by hand, or do you agree with the shop that it feels too loose or floppy?
09-04-21, 09:26 AM
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In some gears, the drivetrain action doesn't feel entirely smooth. It's kind of hard to explain but almost like something is "catching" a little bit like say you had some gravel in the drivetrain. It's not horrible but noticeable. This seems particularly true when it's on the fifth and sixth most smallest rear sprockets. I do not notice it when in the larger sprockets. I almost exclusively keep the chain in the middle of the three front sprockets. The chain seems to skip when going over a large bump and moving along pretty fast. Again I "think" this mostly occurs when on the smaller rear chain rings. As I mentioned, in the bike shop the mechanic said everything was working properly and measured properly so I think the "catching" feel but be mostly under load. I'm not a real heavy guy, about 160-165lbs. The shifting action between gears is still very smooth and precise.
The bike although 25 or so years old, doesn't have a tremendous amount of mileage, I would say certainly less than 5K. The original tires still had tread on them, just the sidewalls were rotting so I never had enough miles to wear out a set of tires.
The bike although 25 or so years old, doesn't have a tremendous amount of mileage, I would say certainly less than 5K. The original tires still had tread on them, just the sidewalls were rotting so I never had enough miles to wear out a set of tires.
I agree with the bike shop that a modern bike today won't be a big step up from your 7500, but I don't necessarily agree that modern parts aren't as good as they were back then. The original derailleur model is not made anymore, but you can get stuff that'll work very well. The Shimano Deore RD-M591, available in both black and silver, may be the closest version of what's commonly available new today. It's designed for a 9-speed drivetrain, but should work well with your 7-speed configuration. Of course, you can get new old stock or used parts on eBay and other sites as well, but you take the risk of getting something that's just as worn out.
That is, if your rear derailleur is truly worn out. We may be able to help you troubleshoot if you can give us some more details. When does the chain feel like it skips? Only after a large bump...and does it happen in any gear combination? Chains will flop around some after bumps, moreso if the derailleur springs are weak...this is true. Does the derailleur feel tight to you when manipulating it by hand, or do you agree with the shop that it feels too loose or floppy?
That is, if your rear derailleur is truly worn out. We may be able to help you troubleshoot if you can give us some more details. When does the chain feel like it skips? Only after a large bump...and does it happen in any gear combination? Chains will flop around some after bumps, moreso if the derailleur springs are weak...this is true. Does the derailleur feel tight to you when manipulating it by hand, or do you agree with the shop that it feels too loose or floppy?
Last edited by geepondy; 09-04-21 at 09:29 AM.
09-04-21, 06:16 PM
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It almost sounds like the indexing might be off just a little bit, and the chain links are catching some of the teeth weirdly in the smaller sprockets. It'd be helpful to have it up on a bike stand to investigate closer. If you can get the "hitch" to happen as you turn the cranks by hand, see if you can tell if it happens once per wheel revolution. You can slow it down and watch closely to see if a chain inner link or outer link is catching on one of the teeth. Some of the teeth have a twisted shape to them to aid in shifting, and the chain can sometimes catch on these teeth if not properly centered on the sprocket. If it's doing this, then a half turn or turn on the barrel adjuster may help tweak that positioning just a little bit.
09-19-21, 06:45 PM
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Also, be sure each link in the chain rotates smoothly with no tight spots. This sounds like a chain problem more than anything so inspect carefully. You might find a spot where the chain is slightly twisted; a small tweak with two adjustable wrenches can straighten it out. If the pivots or rollers are tight, flexing the chain from side to side will loosen them up enough. Do this by holding the chain on either side off the stiff link and pushing the chain as if you were trying to widen the link plates.
