Bike Fit Help - Comparing reach and stack

Looking into a new bike for the spring and as much as I want to support an LBS, the pricing is just so out of line even after international shipping. I’ve never had a proper fitting (or a proper fit bike as it turns out) so I am going a bit by spec. For most frames I am right on the edge of fitting into the high end of a 54 or low end of a 56. My preference is to go with a 54 and have a slightly shorter reach than stretch out into a 56 or have a really short stem. Anyway, looking at stack/reach numbers of various bikes, they all seems to come in very close. Of four possibilities, would the 4 bikes be similar in fit or does the 5-10mm make a huge difference?


5-10mm can actually make a big difference in the feel and fit of the bike. Now, there are lots of ways to make bikes fit with different stems, bars, seat posts, etc. Can you make the 54 fit like a 56? Probably. But there are other factors at play between the sizes such as wheelbase that can change the way the bike feels also.

My suggestion as someone who just went through the same decisions is to go get a bike fit with a fitter who uses something like Retule(and not your bike). Have them spend some time setting the stack and reach to match the bikes you are interested in and see how they feel. Learn what numbers feel best to you and then you can shop with more confidence. A fit is really worth the money.

It’s easier to make a small frame fit larger than a large frame to fit smaller.

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The first Medium (543x388) is the only outlier. The others are pretty close. It has a longer reach and lower stack so you’d be stretching that much further.

Some aren’t picky, but I personally notice differences in stack height can change the way a bike feels even more than reach. I prefer a low front end and have never gotten along well with higher stack frames which have become more common with taller head tubes relative to frame size.

Definitely get a fit first or find a bike with similar measurements to test ride.

Why wouldn’t you get a fit and have your personal measurements/capabilities drive the decision? Anything anyone posts on here is going to be (necessarily) making a ton of assumptions about you and your body

In an ideal situation, I totally agree that get fit, use the numbers to find the closest possible match Reality is that compromises will have to be made to fit a budget. A Retul fit is $350 on it’s own and then have to track down a bike that fits the fit specs in the price point I need to hit. Even a basic measuring tape fit is $100. I know that some would argue that it is well worth worth, but I would rather put that money into getting the most out of a bike within the budget. I’m not an elite athlete looking to get every last drop of performance or marginal gains for a race bike, so it can be less than perfect fit.

How much do you plan to spend on cycling in 2019? You are likely to get the most of of your spend by putting some amount of that money into a bike fit instead of the actual hardware

This will also be a helpful post:

What are the dimensions of your existing bike? Does this work for you? If so, you can use the bike geometry calculator in the above post to find a bike that matches pretty close.

Existing bike, a 56sm Stevens SCF is sold so I can’t take direct measurements. It fit too big for me, with reach being my issue and now I can see why. If I remember trigonometry well enough from the specs I found (before stack and reach were a thing).

Stack 539
Reach 396
Eff. Top Tube 555
Seatpost Angle 73.5

Ive used this to get my 2 road bikes as close as possible