Help with Vintage Trek 720 Fit?
 

Hello,

I was wondering if someone could help me determine whether my bike fits me. I got an '82 or '83 Trek 720 that belonged to my Dad fixed up and am fearing it might be too big for me, just going by the sizing charts. (Feels fine to me, who knows nothing about bikes!) From some research on vintage-trek.com, I can determine by the serial number that it was an '82 or '83 and a size 22, which from the old geometry chart means 56cm seat post and 56cm top tube. I'm 5'7" with a 31" inseam. I've included a lot of detail below but the tl;dr version is: Can someone confirm whether this bike is too big for me and, if it unambiguously is, tell me if that's something that is just likely to affect performance (which I can live with), or is likely to cause me pain (which I'd like to avoid)?

When I ride the bike it feels great, but I'm also a complete novice and wouldn't know what to look out for anyway. I'm also not really used to the drop handlebars. I guess I would say it doesn't feel big, but I don't know what a big bike would feel like in any case. The only thing I notice is that I get some pain in the back of my neck right where it meets my shoulders after about 30, 40 minutes of riding. I don't know if that's from the fit, or because I'm not used to the posture one needs for drop handlebars and just need to beef up the muscles there, or even because I have a Bern (I think Watts model) helmet that's not really optimal for that head position.

As I said, I'd like to take this bike on what seem to me like long rides (although for seasoned cyclists they're probably fairly short): around 30-60 miles. I don't have money for a fancy (or even decent) road bike, so having a hand-me-down like this would be great if I can make it work. I've also read that the vintage Trek 720's are great and somewhat coveted, so I'd be loathe to give it up, especially as it's straight from my Dad, who was the original purchaser.

What I'm mostly looking for is someone to tell me which of three possibilities is likeliest: 1) The bike's not actually too big for you, hooray! 2) The bike is too big for you, but if you don't care about optimum performance, you should be fine. 3) The bike is too big for you and is likely to lead to some pain if you put a lot of mileage into it, a sign of which is already the soreness you get in your neck.

Thanks for reading and any help you can provide!

It is big, but not too big.

1. If you standover the frame, does it clear your jewels?

2. If you ride long distsnces, do you still find it comfortable? If not, you can get a shorter stem.

This bike will work totally fine for you.

We can make all kinds of hypothetical rhetoric on why it is or isn't the right size for you, but until you actually go out and start having aches and pains or find that it seems to limit your performance then none of this will really matter.

I'm 5' 11" and rode a 64 cm bike for over 35 years and was comfortable on it for the riding I was doing at the time. As I've started riding longer, further and faster I've sized down with several sizes between to currently a more sensible 56 cm frame and wonder if 54 cm in this particular geometry might have been even better.


3) neck muscles might just be getting use to having to do more work than previously. Or you are straining to keep your head up to see further down the road. In that case I usually find the helmet at fault. If you can't adjust it to stay out of the way of your vision so you don't have to raise your head up so far, then get another that doesn't obscure your vision when leaned over.

Ok, great. Thanks! I do get enough standover clearance. Just barely, but enough. I'm not worried about getting injured, for example.

Other than the neck pain, which sounds like it might just be from inexperience, it's actually by far the most comfortable bike I've ever ridden. I actually raised the stem as high as it could go, so I'll try lowering it and see if that helps.

Re: Iride01: That makes perfect sense -- I just have to ride it and see how it feels. When I was googling it seemed like some people are very particular about fit, but the sense I'm getting from the replies is that it's more subjective and depends just on how it feels to the individual rider. & re: neck muscles, that's probably it. My current helmet definitely restricts my range of motion, so I'll try a new one. Thanks for the help!

I'm an inch taller than you with the same inseam and feel like 22" frames are too small. I really prefer 23"/24" frames on older steel bikes. On older bikes, especially, the nice thing about riding a frame size that is a bit close in standover is that your saddle gets lower and closer to the height of the handlebars.

That bike is likely too large for you. I own several vintage Treks (including a 22.5 720) and I worked in a shop when those bikes were made and sold. Your inseam is long enough to clear the top tube comfortably but that top tube is on the long side given your dimensions. A shorter stem might help but the next size down (a 21 inch frame) would help even more is my guess.

Here's my bike fit primer: https://www.bikeforums.net/21296948-post3.html

Go through the steps and see if it feels right and looks right in the mirror. If you can make it so, it's a fine fit. Might not be optimal for performance, but you won't be racing it either.

If you need to adjust reach by going to a different stem:
This bike probably has a stem which locks in place by tightening the Allen screw in the center, so it's called a "threaded" or quill stem. My guess is that this bike is big enough that you can install a threadless stem adapter and use any of the zillions of threadless stems available.
https://www.amazon.com/s?k=threadles...=1FFKYRFSZSIJE
https://www.amazon.com/s?k=threadles...f=nb_sb_noss_2

Be careful with your neck. Make sure you keep it straight in general, not just when you are riding. Lowering the stem likely wouldn't help, but you are encouraged to experiment with saddle/bar height angle etc etc. Maybe look into that shorter stem like I was suggesting if you take that bike seriously.

Thanks, everyone! I really appreciate the help. I'll ride it around with it to see how it feels, get a new helmet, and swap out the stem. If it ends up not working, hopefully I can sell it or find a good trade.