How important is frame size?
 

We went down to the LBS for a new MTB and brought a bike I know I like the feel of, my Trek Roscoe 6. Tried a few bikes Scott acent, Canondale trail SE and GT Avalanche Expert. Went with the expert. Didn't have a dropper post, but had the 1x12 I wanted a better fork (Rockshox Recon vs Suntours on the Canondale and the Rockshox Reba on the Scott) I figured for less money, the nicer fork was a plus, I think the other two had smaller cassettes too. But that may be level dependent and not a huge issue. Either way, they all seemed comparable and nothing night and day different. I was sent away with a med frame on the GT and I ride a Med on the Trek too. But on the GT webpage they say the Med is for a 5'8 to 5'11 person. I am not experienced enough to know what a "perfect" fit feels like. I can stand over the bike in flat shoes and just clear the top bar. They said they could try the small if I really felt it was too large but that it looked good. Riding it, it's so much better than my last 400 dollar bike that it's night and day. Huge step up. Should I really even think about Sm vs Med frame size and is this something that will matter more as I get more experience doing this? Thanks for the replies, over all, it's nice that both of us have upgraded!

You didn't mention how tall you are. Manufactures have different measurements with their frames. For example, I am a L or XL depending how the manufacture designs the frame.

To answer the question in the title, a frame being the correct size is the most important thing when selecting a bike. If you are between sizes, finding the correct size is something you need to figure out. Take both bikes on a 20-30 minute test ride (longer if possible) and pick which feels best.

If you are happy with the fit on your Trek, why not just measure reach of saddle to mid stem on the GT and match it or get really close ?

for off road riding - especially tight technical off road riding - the amount of standover clearance does not appear to be ideal

but I don't know your primary type of riding - and obviously have not seen you on the bike

how is the length ... top tube length ?

what is your height ?

When I was at 300 pounds plus I rode a big heavy duty ChroMo 80's FUJI till I got my weight down. Called it my horse cause I had to jump on and off of it. The only reason I was able to do it was because of my years of experience ridding 70's road bikes.

My suggestion to you is not to get a bike that is too big for you. Especially if you don't have allot of experience ridding...

I'm 5'6, 185lbs with a 31" inseam. That puts me at around an inch over the stand over height on this bike with the 27.5s. I'm going to be honest, riding the Trek and this bike side by side for 30 mins, I can barely tell a difference. GF and I traded off on a 5 mile ride and the only thing we noticed was that the spring fork isn't as good as the air fork and that I will probably want a dropper post for the new bike. Setting them side by side, they are really close.

I picked up the same bike this spring. I’m 5’11” with a 31” inseam. Stand over height feels perfect but the reach feels a little cramped. Their sizing information is just a guide and not going to be perfect for everyone. Sounds like you got the right size.

And standing over the Trek Roscoe 6, the top tube comes up quicker and seems as close/closer. There's maybe a half inch difference if you sit them side by side, and the Trek is supposed to fit down to 5'4. I'm just not sure how to be sure since I'm an amateur. Trust the LBS who said I was good, or trust the "sizing guide" that says go for a small.

Sizing "guides" are just that--a general guide, and are not correct for everyone. I had considered a hybrid once, and like the Trek FX line. Trek's sizing guide indicated a medium was the right size. Went to a dealer, medium was much too small, while a large was perfect. A guide might get you in the ballpark but it's no substitute for actually riding the bike. Didn't buy a hybrid-decided didn't really need one.

I suggest dropping the focus on standover. Sizing modern MTB bikes using standover is a bad idea, and nobody who understands modern MTB fit well would do so.

Go by the length of the reach and how it feels actually riding it.

Frame size for mtb IS very important, because getting the proper frame reach is very important. At least if you are going to be riding technical terrain. If the bike is for more casual riding or mostly paths and rail-trail stuff then you have more leeway to make adjustments with stems length and such.

At 5’6” you could be a med on some bikes and small on others.

If you do decide to make standover a deciding factor (which is a big mistake, IMO) then look for a model that has standover AND proper reach. Going down a size in a particular model just to get more standover can leave you with too small of a frame for the 99% of the time you are riding it rather than standing over it.

As far as whether to go with the shops rec or the manufacturer’s guide… depends on the shop. Did they have you ride the bike around the parking lot and see how you positioned yourself or did you just sit on it in the shop?

Try searching forums like MTBR (there is a Trek sub-forum there) to see how others sizes up on Roscoes.

It was raining when I bought so they let me take the bike home to ride and said as long as there was no major damage I had 30 days to decide. The only reason I mentioned stand over height is it's the only thing I could think of and I don't know a lot. I won't be doing anything technical. It's been a progression to get here from where I was a few months ago. The bike shop had me stand over it, sit on it, ride it at home and has been great about communication. I think I'm just overthinking. At 5'6, there have been a TON of times I've purchased items that just didn't fit (bows, guns being the most common) and the learning curve on fit there was expensive. I didn't want to even risk it, so I'm trying to triple check everything. Riding it feels great, I did six miles the first day on loose gravel and dirt road hills. Which is 90% of my riding. I found I really noticed the difference in gearing from the Trek 1x10 to the GT 1x12. My low end made for easier climbs and on the high end I can hold a faster pace easier. So I'm liking that. The fork is also night and day. We get some washboard out here and the Rockshox seams to react smoother and more quickly where the spring fork on the Trek seems to always be "catching up". I've made a few connections locally and will be going from my trail rides to some low end downhill next summer. So hopefully my understanding of this stuff will go up the more I do it. Right now it's hitting hunting season and this is going to let me get some distance off road where people usually can't get to. Other than that, it's fitness. I run a lot but I notice that the bike is far easier on the joints. I tend to enjoy a 6 mile bike ride far more than a 6 mile run these days.

There is no advantage to a bicycle to big for the rider, or one to much to small either.

A really long or really short stem affect steering and handling.

A super long seatpost or one jambed way is affect pedaling geometry.

A good fit is essential.

BTW, the top bar always wins!

rusty

Lol, I'm an inch or two over the top bar. I rechecked with the bike shop and they assured me fit is good. If it was the smaller frame, they said I would be sitting really upright almost the same as a hybrid. They actually said a smaller frame would feel like the Verve where my reach was short and I was sitting almost strait up. Since they know more, I think I'm going with it. Riding it feels good and I will have a few miles in this year deer hunting to really see how I like it. Next year I will begin a few more technical trails and see how that turns out. It was a weird progression from the verve to a mtb but I think this is more what's needed for my activities. Hopefully the next few posts will be more about the rides and less about figuring things out.

I cant straddle the top tube on several dual suspension bikes i have had (and have )

Granted -- a dual suspension bike is a different animal, - but just throwing that out there for the folks that claim you need to have top tube clearance in all cases

Standover doesn't matter when riding. Proper sizing and fit is based on cockpit length.

If you're comfortable, IMO it's settled. My wife, 5'5" but long legged for her height, rides a M Felt 29er better than any of her previous bikes. Standover may be over-valued since (normally) you don't put both feet on the ground simultaneously when stopping.

To put standover into perspective for me:

I’ve been riding a new MTB since April. I have never checked the standover. And until I checked yesterday, I had no idea if I have any. Turns out i don’t.

I ride very technical terrain, and regularly need to bail or put a foot down. Never notice the standover.

Even if you have standover on flat ground, When you have to dab on a trail, it won't be flat. If you were depending on standover clearance, you will get racked.

Right.

Whenever I dab a foot, I am also going to be leaning the bike in that direction, anyway. With the non-dabbing foot on the other pedal, you have a lot more clearance.

Also, in those times when I do go over due to not being able to plant a foot on the ground, it is the saddle - not the top tube - that is in my way.

A too tall or a too small frame can have bad consequences on your back or kness and on your position in the cockpit, also don't cut the steering pivot too much other wise it would impact your back badly. I always had 17.5 -18 inch sloping MTB frames. I always made sure before having my bikes assembled that the riding position would suit me.

Fit is always important on any frame that you plan on riding. Standover not so much but actual fit on the bike is supremely important and really the most important because if they bike doesn't fit you and you aren't comfortable on it size wise you aren't going to ride it and enjoy it so why buy it.

Going to have to trust my LBS then. They say the frame is the correct and it seems to fit fine. Time in the saddle and experience is probably what I need. Once it's spring again I plan to hit the trails early and often.

fwiw - if I'm climbing a steep hill, w/ tree roots & stall & stop, the top tube is significantly higher than when the bike is on level ground

are you really gonna wait that long to ride it?

forgive my ignorance
how do you bail
what is dabbing?