Finally landed a whale: 1983 Trek 720
09-03-23, 10:50 AM
#101
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I think after a while the only way to answer the flex question is to personally observe or experience it. Everybody has different levels of sensitivity and ability to discern, and no one is listing weights or placements of weight etc. Sure, a guiding principle that a thinner tube over a longer distance will be inherently more flexible is true, but if your partner is anything close to the average woman, the stress she is putting on the frame by herself, and even if loaded, is still very likely less than just me on a much larger and more flex-prone (due to size and my weight) 720 (my '82). I wouldn't worry about it unless she is a super packer and a track sprint specialist.
I'd ask for photos, but in lieu of them being provided, looking at the OP's 720 with 27" tires, I see acres of room for fenders. If those 1 1/4" (32mm nominal) tires are accurate, add about 4mm more in height and width in 700C form (of which there appears to be plenty of accommodation) and I'd say there's plenty of room for true 35mm tires and fenders, which will net anyone with a phenomenal ride (provided the tires are something along the lines of Soma Supple Vitesse or Compase/RH, or at least Pasela 35s).
Ultimately, it's up to you to experiment. I will say that some basic measuring of present clearances on your part will go a long way to you personally answering your own questions regarding clearance. You have the bike and the ability to do this. You likely have other bikes with 700C wheels and larger tires with which you can easily and (crucially!) immediately swap on to this 720. The '83-85 720s were designed around 27" wheels, standard 27" tires, and fender usage. Only 1982 was designed for 700C wheels, and it will fit 32mm tires and fenders, though it's a little snug. Later 720s are bowling-with-bumpers-up easy to fit tires and fenders on. The only Trek/bike they'll be outdone by is a 1985 620 which will fit 40mm actual tires and fenders if you play the game perfectly. It's insane, which is one of the reasons I keep that bike as well.
I'd ask for photos, but in lieu of them being provided, looking at the OP's 720 with 27" tires, I see acres of room for fenders. If those 1 1/4" (32mm nominal) tires are accurate, add about 4mm more in height and width in 700C form (of which there appears to be plenty of accommodation) and I'd say there's plenty of room for true 35mm tires and fenders, which will net anyone with a phenomenal ride (provided the tires are something along the lines of Soma Supple Vitesse or Compase/RH, or at least Pasela 35s).
Ultimately, it's up to you to experiment. I will say that some basic measuring of present clearances on your part will go a long way to you personally answering your own questions regarding clearance. You have the bike and the ability to do this. You likely have other bikes with 700C wheels and larger tires with which you can easily and (crucially!) immediately swap on to this 720. The '83-85 720s were designed around 27" wheels, standard 27" tires, and fender usage. Only 1982 was designed for 700C wheels, and it will fit 32mm tires and fenders, though it's a little snug. Later 720s are bowling-with-bumpers-up easy to fit tires and fenders on. The only Trek/bike they'll be outdone by is a 1985 620 which will fit 40mm actual tires and fenders if you play the game perfectly. It's insane, which is one of the reasons I keep that bike as well.
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09-03-23, 03:41 PM
#102
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Under the top tube with a Zefal clamp-on pump peg.
If I swap this to 700c should 32mm and fenders fit fine?
N.B. if you have cantilever brakes on your bike, make sure you can lower the pads enough to reach a 700C diameter rim (4mm lower) before you invest in new wheels. I built my 720 for 27" wheels, because back then (1982), 700C wheels and tires could only be found in real bike shops, not the small town hardware stores I'd go through on loaded tours. Now, 700C can be found pretty much any place, including WalMart and small town hardware stores, but I can't lower the brake pads enough to use 700C wheels on that bike.
there is some concern about fully loaded performance with the reports of it being too flexible.
Last edited by JohnDThompson; 09-03-23 at 09:01 PM.
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09-03-23, 07:01 PM
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The answer is there is definitely room for 32s and even with a nice fender line. Though I'm running into other issues as seen in this thread.
09-04-23, 04:25 AM
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John, that's exactly what I recall from back in the day as well. With a pair of doohickeys like REG umbrellas or such, a pump can be placed behind the ST.
09-04-23, 07:31 AM
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09-04-23, 07:41 AM
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09-04-23, 12:08 PM
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JohnDThompson Were there any "production" '81-'83 Treks with the seat tube panel and seat tube bottle cage mounts? Of the Treks I've seen, it seems like they didn't introduce the seat tube mounts until 1984, when they dropped the seat tube panel. I take it your build is custom, right?
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