Frame Sizing
 

I just picked up a 1988 Trek 400T. It's in good shape and I got it for a really nice price.

The lady I bought it from is approximately the same height/proportion as me and she's had the bike for 20 years and she says she's perfectly comfortable on it. I think it's too big for me. After dropping the saddle, I'm comfortable riding the bike- to the pedals, to the handlebars- all good. However when I stop, I'm effectively sitting on the top tube.

I'm 5'8" and wear 30" trousers.

What size bike should I be riding?

Trouser size means nothing.

http://www.veloweb.ca/bikefit.html

Sizing is difficult from just height and inseam, but we all generalize anyway.
Trek sized the 400 in inches in '88, so my unscientific size for you would be between the 21" & 22.5", with the 22.5" probably feeling a little large. Trek measured the seat tube c-t.

Same height never really means same frame size.
She might just have longer legs than you proportionally, which I think is the typical situation when comparing physiological measurements between men and women.

Chombi

Some people say they are comfortable on bikes that are 9 sizes larger than what the charts recommend, and others ride with their knees level with their hips.

- Ultimately it boils down to what is best for you over the long haul.

+1 on some people not following the charts. I usually go a couple cms longer in the seatpost then what is recommended and I have seen others on C&V say the same.
OTOH I have never had a professional fit done.

Some folks like 1+ inches between the top tube and the "stuff", others ride such that they can't stand over the top tube without leaning. It's all a matter of preference. Aside from ym modern Cannondale all my top tubes nestle quite snugly "up there".

As long as the bike fits you and is comfortable I wouldn't worry about the standover. You just lean a little bit so you don't crunch the top tube. However, if the way it is not makes you feel unsafe then I would look at doing something different. Coming to a stop and starting again in traffic is the very last place you want to feel the slightest bit twitchy or tentative on the bike.

You should be able to comfortably get off the seat in a panic stop and get your feet flat on the ground standing over the top tube...

When stopped, wearing typical riding shoes, you should be able to straddle the bike while keeping both heels (feet) flat on the floor. If you cannot do this, basically, the bike is too big for you. A little too small can be dealt with. A little too large is, flat-out, too large.

There you have it.

The bike is too big for you.

I also heard from racers quite a bit in the 80's that they try to ride the smallest frame they can to maximize stiffness and response. It must be true cause I remember feeling that I had such a gigantic bike at 56CM compared to what was mostly lined up on the start lines in criteriums I watched back then.

Chombi

I disagree with this. You can make a small frame work but the ride could be compromised. Often times a frame that is slightly larger yields a much better ride and in that case as long as you can straddle it still I say the slightly larger frame is the way to go. I think that most stores these days size WAY too small for most riders and don't take comfort of the ride into consideration.

53-56cm.

I'm 5'8" w/ 29" blue jean inseam. Ideally you want to buy based on top tube size. I fit well on bikes w/ 54cm TT's. I own a variety of bikes with a variety of seat tube lengths but they all have 1 thing in common, they're all have 54cm TT's +/-.

+1

I recommend you read this.

I think you did not comprehend what I wrote, so I will quote it for you here, "... you should be able to straddle the bike ...".

Ride, schmide, ... Ever come down hard on your top tube of a frame that is just too big? Ever had to tip sideways to get off your bike. Failing to do so can hurt. Slipping while doing so can hurt - plasic soled riding shoes are a good way to cause this trauma.

The fact that the OP even notices this is proof positive (to me) the bike is too big for him.

Go get a dfifferent bike. Sell this one and get on that fits.

What a long winded explanation of something so simple.

Put on your riding shoes (or something similar, or take off your shoes). Throw your leg over the bike and try to stand erect with both feet flat on the floor while straddling the bike.

1. If the top tube/brake cable is touching your crotch, the bike is too big.

2. If the top tube is much more than 1" away from your crotch, the bike is probably too small (but might be workable, maybe).

3. If the top tube/brake cable are about 1" from your crotch, the bike is just right.

If you think it is too big, then it is too big. Size is a personal decision. Before dumping the bike for something smaller, I would take it for a long ride.

+1 Don't base your size on what other riders do. What if they are riding a bike that really doesn't fit them either? Do you want to copy their mistake.

Ultimately, you make the choice, and I think you have.

+1

I agree with Mike. This is a pretty simple baseline. I used to ride a bike which I couldn't comfortably straddle; it was my dad's bike, and I was about 10 years old. No sense worrying about your "stuff" every time you approach a red light.

I read it and comprehended. This is what I disagree with. As long as you can touch the ground if the top tube is in the crotch a bit I think it's fine if that is what gets you the highest comfort level while biking. I hear about the fear of smacking the goods alot but I have not known anyone that has done that or done that myself. It is a fear tactic in my mind. I don't agree with sacrificing ride quality for an extra half inch of crotch room. Just my opinion.

I have a Surly Cross Check with a 58 cm seat tube. It was a deal I couldn't resist. It hits my pubic bone when I straddle it. I had to put on a very short stem to have a comfortable reach for me. Now, the bike works very well for me, and I feel perfectly safe. Others wouldn't feel the same way.

I have several other bikes, all smaller. My smallest bike is a 1971 Raleigh Super Course and has a 54 cm seat tube. I found I couldn't get comfortable on it with drop bars because the stem height was so low. I put on riser bars, and that was good. I currently have no-rise/no-drop bars, and that's good, too.

So sometimes, a few changes in equipment can compensate.

This is NOT to say you can or should do the same. There's a chance you can't do it with this bike.

Well, I think an experienced rider can get away with a too big bike better than a newish rider. I've owned and ridden 60cm and over frames, but 56cm is really my size..

I disagree, for a traditional frame, unless the person is of unusual stature, there should be at least one inch clearance over the top tube. Many people purchase bicycles too large for them because it is easier to get the handlebars up high so they can sit straight up, they really just need a different style of bicycle rather than trying to justify poor fit and misguiding others in the process.

To the OP, your "trousers" have nothing to do with bicycle fit, your inseam does and unless you are fitting a "compact" or sloped top tube frame, if it is a traditional level top tube road bike, you need and should have clearance over the top tube when standing over it in your stocking feet, about one inch minimum.

Why one inch? Everyone has different proportions so standover is over-rated. Ride comfort is most important and sometimes people feel better on a larger frame. I had a Fuji League that was a size bigger than what I normally ride but the geometry on it made it feel as good as some of my smaller frame bikes. That had very little crotch room for me. If I went by 1" of clearance I would be riding a small frame that would be uncomfortable to ride. If that stat works for you that's great but it's not for everyone. That's why actually riding a bike is the best way to see what size works.

One inch is a decent rule of thumb, useful for many people on road frames, though it doesn't have to be a hard and fast rule.

Thanks to everyone for the insight and everything!


I fully expect that you will subconsciously work in the word "trousers" into conversations. It's going to shock you, just as it shocked me the first time I said "Oh Dear" and "For Land's Sakes."

And to think that all this debate on TT/crotch clearance was made moot by compact frames and their back sloping TTs...."Small Medium.........or Large"??
Frankly, I prefer the debate than the ugly back sloping TTs......:D:thumb:

Chombi