Trek 950 singletrack sizing
 

I have a '93 Trek 950 with an 18 inch frame.It is in great shape with with the chrome moly frame and a suspension fork. I know the frame is on the small side for me, as I am 5'11" with a 32" inseam. I have about 8 inch of seat post exposed unless I have it dropped low. Does anyone else ride a smallish frame for Xcountry riding ? I want it mostly for atv trails and dirt roads ,,,, maybe a little single track at the local ski slope. Thoughts on weather I should just look for a larger frame or ride this and enjoy it ?

Thanks in advance ,,,,
Bill

I'd look for a size Large (20")

For comparison, I'm around 6'1.5" and prefer a 22" Trek 970 Singletrack.

Cross-country MTB riders always go with small frames if they are serious about it, because it allows them to drop back behind the seat on steep descents and makes the bike easier to handle in tight technical stuff. I have been riding a Marin I bought new 25 years ago and I just rode a very technical single-track trail with it that hosted a race a few days before, and it felt perfect as usual. I could ride an XL size frame easy, but when I bought this luckily I researched it and bought the L size frame, I am about 6'2.5". This is what my bike looks like currently;

https://cimg6.ibsrv.net/gimg/bikefor...36b4a7d348.jpg

In the old days it was common the ride a smaller frame with a big seat to bar drop. Now we have learned better. Ride a bike that fits, newer bikes are more stabil and you will go over the bars less often. Dropperposts make getting the weight back much easier and you don't take a saddle to the gut on landing.

5'11 keep the 18" frame, get wider bars. You're not far off, I am an inch shorter than you & 18" is my preferred sizing. Try a wider riser bar like 750mm. Should help with the overall fit and function.

18 is a Medium and you are a Large. And it's an old MTB so it sits a lot more racy than a new one. A 1990's medium would feel tiiiiiny after coming off a 2023 large bike.

Just for fun...

https://cimg8.ibsrv.net/gimg/bikefor...88f0bffd77.jpg

Not sure about that bike’s particular sizing , but 18” could have been a med or large, and someone at your height would typically be a large.

That said, conventional wisdom around sizing has changed a lot since then. First, the frame reach and ETT length) trumps seat tube length as the fit criteria, and those have both gotten a bit longer especially the former.

I was riding 17” mtbs in the 90s with TT lengths just over 22” (with a 120-135mm stem and 580mm bars) If I were to ride similar bikes now I would go with a 19” with wider bars and much shorter stem. In reality though, I would be unable to get a good fit on a 90’s mtb now because in order to get the frame reach I want I would be on a large or XL bike and that would just not work.

As far as your bike goes, don’t worry about exposed seat tube. Just worry about if it feels OK. You can always use a riser bar or riser stem to lift the bars if the saddle to bar drop is too great.

I looked it up. There were four sizes. 16.5, 18, 20, 22. 18 is a medium.

The seat tube length is still important now because if it's a size too big you definitely won't fit much of a dropper. I'm 5-8 so I'm usually on a medium. (Trek would put me on a "Medium Large" lol. Hard to sell a guy something called medium when there's something called large!) With a 17 inch seat tube for me, a 150 dropper, which seems average, is fully slammed. A 240 dropper is not really in the cards! Seat tubes are getting shorter but haven't done that. OEM droppers are still like 100-125mm playing it safe.