Sizing vs Ride Performance
 

We probably all have bikes that are a perfect fit and we mostly know what size bike gives us that sweet spot where the fit is just right on. But most of us also have bikes that are a size larger or a size smaller than our perfect size. We have these bikes because one or two bikes is not really enough and let's face it.... variety is the spice of life. Duplication is boring. Well my question is how does sizing affect ride performance? I would guess that a slightly undersized bike would tend to be more responsive and perhaps quicker to accelerate while a slightly oversized bike may be more comfortable and an easier "all day" rider. I realize geometry, bottom bracket height, etc. is part of the equation but leaving geometry out of the discussion, what I am really interested in is how a slightly undersized or oversized bike (one size up or down form that perfect fit) affects climbing ability and also stamina. Which bike would be a better climber and which bike would tend to wear you out quicker, one that is slightly undersized or oversized?

Depending on:

- Stem height
- Stem reach
- Handlebar reach
- Seatpost height
- Seatpost setback

One frame size up or down can be the same bike. I don't think the frame size matters, the relationship of the rider to the contact points and how you arrive at that is the important part. The frame is just a hunk of metal holding things in the right position.

This doesn't apply for things like seat tube/head tube angles, wheel base and those sorts of things and their effect on "ride".

Sizing would be more closely correlated to fit, and fit = speed.

The only thing size would affect is the weight of the bike, maybe geometry.

John Cobb has had good success with actually opening people up by make the fit more aggressive, and gaining watts that way.

All that's more scientific than I understand.

I ride a 56, but climb better, I'm sure, on a 54. Of this I have no doubt.
I ride a 56, but some long stretches feel better on a 58. Faster? doubt it.
I ride a 56, and I wouldn't want to descend at speed, on either a 54 or a 58; just no confidence.

Since I changed my overall fit, on every bike, to a more aggressive position, I think my performance is better.
Or I've convinced myself so.

Shortly, I'll be taking the next step, which is up a bit on the saddle, and down more on the bars.
Probably close to a 9-10cm drop.

Unless it makes my butt look bigger.

Your assumption matches mine; "full size" are more comfortable on relaxed rides. A wee bit undersize are somewhat easier to handle on long and speedy runs. "Modern" geometry and sizing in road bikes leans to undersizing (compact geometry) so I gather the outcome in performance should be the same for older frames. I prefer 60/61 c/t frames to my old-school-sizing-should-be-63 cm measurement.

Rothenfield....sometimes I see things on the 'net I wish I hadn't...

Personally I'm used to, and prefer, traditional sizing on the big side. It works better for my knees, back, and neck. I've had bikes that were a little too big, and a little too small. A little too big is more comfortable.

Modern geometry is something I'm still trying to figure out, using effective top tube length, etc. for sizing. Geometry, Ride quality and fit seem much harder to ascertain with compact frames.

+100

Trek 5000 54cm, I'm all crunched up,
Trek 5000 58cm, I could put the saddle on the TT.
Felt F70 54cm, felt like a 44cm, I ended up giving the frame away as an alleycat race prize.
Marin Portofino 52.5cm, felt like a 56cm, had a good fit.
Kestrel Talon 48cm in tri-mode, fit fine, but I felt like I was on a kid's bike.

When I see a sloping top tube, I run.

My intention with the original post was that this discussion focus on traditional vintage bikes with horizontal top tubes. I personally would never ride a sloping top tube bike. Just have no desire to go there, just as I have no desire to ride a threadless stem bike, although I might make an exception for a Neo Primato. I guess I'm just too old school. All my bikes are horizontal top tube. It appears from the posts as though sloping tube bikes have little consistency with regard to how they translate to fit.

Let me restate my original question and add that that I am asking this in relation to vintage, traditional horizontal top tube bikes.

I'm 5'9", like a 31.5 inseam, and I love riding bikes that are borderline to big for me. I just feel better once im up in the saddle. My centurion is a 58, my schwinn is a 23, my fuji looks like a 23.5

Y'know, I found that one of my bikes (My Freschi) fits me just perfectly for climbing, flats, comfort - essentially, everything. So when I decide on bikes to keep, I try to match that geometry and measurements as closely as possible. I look at stem length, saddle height (from crank center) and position, bar width, etc. to help inform my decision-making. That said, I prefer a longer, more stretched out top tube: fit wise, I'm supposed to be riding a 58, but most 60's seem to fit me better, especially for climbing, where I prefer to stay in the drops rather than standing. For longer climbs, where I will occasionally stand up, my 58 seems to be a better match up. (However, that is a modern bike with slightly sloping top tube, and I'm not certain how much modern geometry changes the equation.)

I think the size smaller would be a better climber. It may not wear you out quicker, though, being lighter.

Possibly, the size larger would wear you out quicker, as it's a bit heavier, more cumbersome to manuever, and you have to be vigilant about that top tube. The vigilance (OK, call it fear) of that top tube made me a better rider, but the one time I forgot, with slick cleats on a sudden hill.....well, it wasn't fun.

cpsqlrwn, The larger frame would have a longer wheelbase, if geometries are the same providing a marginally more stable ride with a slight weight penalty. If both sizes can be made to fit properly, I don't see much of a difference.

Brad

I just got a 1977 Schwinn Superior. I'm sorta intrigued by the Schwinn fillet brazed geometry and frame characteristics. The frame is a 24" by Schwinn measure which is to the top of the seat collar. But its 23" to the top of the top tiube. I usually ride a 23 1/2 or 60cm frame. The Superior has a somewhat unique measure. I've also noticed the bottom bracket is fairly low as well. Havent ridden it yet but am looking forward to checking out the somewhat smaller frame than I usually ride.

I tend to ride larger frames than I did when I was younger, keeping the bars higher. In general I think a larger frame is more stable feeling.The problem with larger frames is the top tubes get longer as well. So much shorter stems are necessary. Out of the saddle riding also seams a bit slower, you cant really whip the bike around underneath you.

one of my favorite bikes is a 62cm Gitane. Slack angles, plenty of fork rake, I really like the ride quality. I have a smaller 60cm Rickert that is the best firtting of my bikes, and its a dream to ride. It feels light and absorbs bumps well, has alot of snappiness to it. Looking forward to riding the Superior and how its going to compare.

It seems I've posted about this a lot, but...

I vastly prefer a smaller frame, basically the smallest frame I can fit on. Why? For starters, my size. I am 6'1" with a longish torso and long arms. On top of that, I do a lot of long steep climbs, followed by fast descents. I like to have my bar low enough that my back is flat when I'm in the drops and about 30 degrees when I'm on the hoods. I find that position helps a lot when climbing and on the flats. For descending, I like to tuck and get into a downhill skier position. So, it goes without saying that that is important, too.

I used to ride with John and the "wild bunch" on the Saturday morning training races back when he had his shop (Racing Research) in Shreveport, LA. Although he was always big on optimizing power output/speed via a more aggressive/aerodynamic riding position, he told me that he once rode a mountain bike wearing a sombrero (in a road race?) and threw peanuts at the other riders. John said that to win a bike race you had to finish, and to finish you had to be comfortable on the bike. For some riders that equates to a larger frame.

Love that!! +10

andy

All I can say, I am learning a bunch just reading this thread!! :thumb:

Keep it coming..;)

I grew up riding bmx, so i was always on a smaller feeling bike. When i first started getting into vintage bikes, i didn't give too much though to size. So one of the bikes i have that i absolutely love, is an 82' Schwinn Le Tour Tourist. It's too small for me, 21" i believe. I'm 6'. I've taken it out for a few mini-tour bike camping weekends. One of which i did a 7 mile climb over a pass. I was dying!!! Of course i only had 10 gears so that didn't help.

Fast forward to recent and i picked up a 85' Raleigh Alyeska that's about 23". Night and day as far as fit is concerned. I can climb much better, i'm faster, etc. I still love my Tourist and will still do some light vintage touring on it, but nothing that involves a climb.

I think the hard part about being into vintage bikes is finding them in your size. I think it's definitely more important if you're looking for a vintage road bike or touring bike that you still want to ride heavily vs just having around for looks and collect-ability and just riding short distances.

Irrespective of Schwinn's marketing hype, that is a 23" (C-T) or 22.5" (C-C) frame. My Capos use a similar tall seat collar system, and I always consider them 55s, rather than 56s.