spinconn

Looking for a used bike online and have not done this before. There will be no test ride opportunity and one question I have is on the specs I should look at to determine how relaxed, or upright a position the geometry will afford. I know stack and reach are two specs to consider. Any other specs I should look at to judge that one specific issue?

Also, other than the classifieds here, and used bikes listed on TheProCloset, are there any other good sources for online used bikes?

crazyravr

Thats pretty much all info you need to size up. The ride "quality" is a whole another thing to consider.
Craigslist, Kijiji, FB marketplace, Ebay.

eduskator

Curious to know why you can't test ride the bike? Is it because you're going to get it shipped to your place?

First time buying a bike or you bought road bikes in the past?

Did you consult the manufacturer's website to see if you were within the height range of the bike you're looking for?

spinconn

1. Yes, it will have to be shipped if from some sources. From some sources I can test ride, but not all.

2. Long time cyclist, never fast or talented but at 75 I still ride about 100 miles a week. Never had a top tier bike, Specialized Roubaix was my most expensive, an old steel Pinarello my best, but I will be buying a cheap bike under $2500 I hope, and want at least a 105 groupset, so that means mostly used bikes.

3. My current bike is a GiantContendAR4, which is a relaxed geometry entry level bike and at my point in life I do not want to get more aggressive in geometry than that bike. "My problem is I have an unusual build with very long torso and arms, and very, very short legs. When I try to use a size calculator online it gets confused. The one on the Trek website says something like "sorry, there must be some problem, there is no size for these measurements". Had two bike fittings in the past and the results were less helpful than my own trial and error. So, I am trying to figure it out with geometry specs.

My two LBS within an hour drive do not have anything in stock at this time that I want to test ride but while I keep looking, I wanted to check out internet possibilities. One bike I like is the Canyon Endurace 8 Disc at under 2k, but it is not available in any size that could work for me. So, trying to do this remotely, without handling the bike in person, I figure the more I can use figures (i.e., geometry specs) the better my chance of success.

fishboat

A used bike with a max budget of $2500 doesn't get you a cheap bike. A good price(unicorn pricing by some sellers aside) on a used bike can range from 30 to 50 cents on the dollar. That "dollar" puts you at an MSRP of $5000-$7500 new..not a cheap build by any means.

As for sizing..if you have a bike, or have the dimensions of a former bike, that you know fits you well..then research the geometry of a used bike you're considering and see how it matches to your known bike(s). Older bikes may not have stack and reach numbers available, but they are easy to measure on an existing bike. If the used bike doesn't have geometry specs available on the web, and you can't size it up in person..move on to a manufacturer that does have spec available. While there are lots of great bikes available, that's one thing I appreciate about Trek bikes..the specs are available going back 30+ years.

Iride01 

What fit do you want? Did any of your previous or current bikes seem to give a great fit compared to the other. Or did any of them seem to bother you more than others?

Consider how much saddle to bar drop you might want, if that matters to you. Some I think get uneasy feeling in very aero positions with their head low and out front. Bikes with low frame stack will be able to give you the most aero position easily. Or they'll be the ones you'll have your arms straight and elbows locked trying not to be bent over so far. And that'll be all sorts of issues.

Your proper saddle height on a road bike will be virtually the same no matter what size bike or model of bike you get. And knowing the frame stack will help you decide what fit a bike will give you.

Your Roubaix is one of the most relaxed and least aggressive fit road bikes you'll find. When looking for a new bike, that's the one they wanted to sell me being an old guy. But I knew I was wanting more aero and talked them into selling me a Tarmac. Which is one of the most aggressive fits with lots of saddle to bar drop. And geometry wise, comparing a Tarmac to a Roubaix (2020 models). The frame stack on the Tarmac is 40mm lower. And the frame reach 11mm more. So the bars you can figure will be that much different in their position since the two models have the same bars, stem and come with the same number of spacers under the stem that you can remove to go lower.

But, you don't get to go any higher. At least not without making that beautiful bike into a dorky looking bike. So be careful looking at bikes online. The aggressive fit bikes always look the most aesthetically pleasing to me, especially in the pictures on websites. But if you don't want aggressive, you'd be making a mistake to be swayed by the looks.

Some seem to think that less aggressive fits are better for longer rides. I don't quite agree. I do perfectly well on a long 60 mile plus ride on my Tarmac. However if your riding is going to be less effort and slightly more leisurely, then less aggressive might be better. And for rides of multi day trips when you are carrying everything with you, you'll be at a slower pace, so then too, a less aggressive fit is likely more desirable.

genejockey 

If you have a bike that fits how you want it, or even close to how you want it, you're most of the way there. I bought a Canyon Endurace back in 2020, after carefully measuring the bikes I had, and making sure I could replicate that fit. Canyon took my height and inseam, and recommended a Medium, but I was concerned because the reach and stack were both considerably less than my other bikes. Also, the Medium came with a 100mm stem, which combined with the shorter reach meant a significantly closer bar. I went with the Large, and had no trouble replicating the fit of the other bikes. It took a lot of careful measuring, but it was worth it.

SoSmellyAir

Which year and size is your Contend AR4? Why not just compare its geometry numbers with those of the target bike?

And, if you are riding the Contend with a longer than usual stem -- because you have a "very long torso and arms" -- then surmise that you will likely be OK with a bike with a bit more reach, but not less stack.

spinconn

I agree, my question was basically just what other geometry specs might come into play, other than reach and stack.

SoSmellyAir

IMHO, for comparing two frames for fit -- i.e., setting aside handling for now -- the third measurement (after Reach and Stack) to consider would be Effective Top Tube.

Iride01 

Not really much if you are looking at a true road bike. The seat tube angle might be a little slacker for a road bike that is considered a touring bike. The ones you use for multi-day trips loaded to the gills. If the seat tube angle is extremely slack, then you probably aren't looking at a real road bike, maybe more of a cruiser. Or if it's gone the other direction and steeper, then you might be in TT bike territory.

You can also look at reach from the perspective of Effective top tube length, but consider that the STA on most of your road bikes are going to be within a few fractions of a degree, frame stack will give you a relative number to compare all by. Some makers still don't give effective top tube length. The only difference is it's measured horizontally from top of head tube (generally there'bout) to the seat tube, and frame reach is horizontally from the BB center to the top of the head tube.

Check the bar reach and stem reach though. Especially between different models and brands. Many give the stem length and even bar width on geometry specs now, but for bar reach you'll have to look them up from what bars are spec'd in the description. And all those reaches add up. As well I found the 42 wide bars on the smaller size bike annoying. So I bought some 38cm wide bars and am annoyed no more. Even seem to improve the feel of handling for twisty and fast down hill turns.

As well check for crank length changes if you are considering more than one size of bike in the same model. Too long a crank might be annoying. It's one of the big reasons I didn't choose a 58cm Tarmac over the 56cm I bought. I'd think you'd get use to a shorter crank, but maybe not.

All the other changes in geometry will just be handling perception changes that you'll either like or will get use to. So not so much for fit, but possibly for particular type of cycling you do or terrain and road surfaces you ride on they might be something. But those will even more of a marginal gain type thing for any discussion to get heated over. <grin>

SoSmellyAir

While it is true that (a) Seat Tube Angle ("STA") for road bikes almost always falls within a narrow range spanning only one degree, and (b) Head Tube Angle ("HTA") likewise generally falls within a similarly narrow range of about two degrees, those few degrees may add up to a significant difference in Effective Top Tube ("ETT"). For example, comparing my existing 2016 Synapse with the 2022 Synapse I just ordered, both in size 54 (generally considered as a medium):

2016 - Reach: 378 | Stack: 570 | HTA: 72.0 | STA: 73.9 | ETT: 542
2022 - Reach: 381 | Stack: 570 | HTA: 73.1 | STA: 73.0 | ETT: 555

This comparison made me realize that I may need to order a shorter stem to replicate my existing fit. But one may not appreciate the difference by comparing Reach alone (i.e., 3 mm difference in the above example). Thus, ETT is a key geometry number for visualizing frame size, unless you can do trigonometry in your head; I cannot.

Iride01 

Bikes that many years apart can have quite a bit of different geometry between the same models in the same size. Sometimes the change is even greater and the bike gets put in a difference fit class to appeal to a different market set of buyers..

But generally for the fast down and dirty method to decide if a bike is going to give the very aero or very relaxed fit I might desire, I'll look at frame stack and reach. Once I have some picked out I might get more fiddly with the other things as well as try to estimate what the real reach will be from the saddle to the bars.

Some of the bike geometry sites let you enter in all the custom data to see that. But I find it easier to do with the simple CAD software that's available. Actually I use the 3D modeling sofware Alibre, but I never take it to the extrusion process to make it 3D. But the sketch up part is very simple to show what is needed to know.

Kapusta

IMO, stack and reach is the best way to size up a bike you can’t test ride…. but only if you know what stack and reach you are looking for.

It also assumes that the seat tube angle is also in the right ballpark.

I have bought many frames with no test ride based on stack and reach and they have always fit within 10mm of what I was expecting.

Maelochs

Short seat tube, long top tube, and a fork with a long enough steerer that you can add some spacers if you want to sit more upright---or which is close enough that you could adjust bar height with a new stem.

I would measure your various body parts and make a simple but proportionally accurate drawing of you sitting in the position in which you prefer to ride, and then measure the contact points. I did this and based on those measurements, I have bought three mail order bikes which fit really well.

DaveSSS 

Effective top tube is irrelevant when using stack and reach. What is relevant is the seat tube angle. In rare instances, a frame might have an oddball STA that would require a seat post with zero setback or a lot of setback, like 32mm. In my size, a 74.5 degree STA is most common, but I sometimes see 74 or 75. 75 definitely requires a 32mm setback for me, but if the frame has a proprietary post with only 20mm, I'd pass.

Also remember that reach can only be compared at ONE stack height. If comparing frames with a 20mm stack height difference, subtract 6mm from the reach of the frame with the shorter stack, assuming that 20mm of spacer would be added to make both the same height.

Stem angle is relevant for frames with integrated bars. A -6 degree stem angle will raise the bars by 15-20mm compared to a -17. I have two frames with -6 integrated bars and chose a short stack than I would have for a -17 stem.

DaveSSS 

This analysis is wrong. If the saddle is placed in the same position relative to the BB, the reach will only differ by 3mm. Your analysis compares reach to the seat post at the stack height. Obviously, a steeper STA just requires the saddle to be moved back further on the post to place it in the same location, relative to the BB. All measurements must be taken relative to the BB.

SoSmellyAir

Yes, I realized that and have purchased a 0 mm offset seat post to compensate for the 1* decrease in STA.

SoSmellyAir

Geez, we have had this debate before: Bike Forums - View Single Post - Retired and want to get back into cycling in my 60s.

1. With Reach, Stack, and Seat Tube Angle, one can calculate the Effective Top Tube.
2. With Reach, Stack, and Effective Top Tube, one can calculate the Seat Tube Angle.

It is just trigonometry. Thus, it makes no sense whatsoever to say that STA is relevant while ETT is not, or vice versa. You are used to looking at STA, while I am used to looking at ETT.

DaveSSS 

ETT is not needed to determine if a bike fits. It might have some value if it actually told the difference in saddle setback, but it doesn't. I've bought my last 6 frames using stack and reach only, but they all had the same 74.5 degree STA. If one has a 74 or 75 degree STA, I still wouldn't need the ETT length. The saddle setback is saddle height times the cosine of the STA. At my 73cm saddle height, 1 degree of change is about a 12mm difference.

​​​​​​Comparing ETT lengths gives you a difference that's measured far below the saddle height, since today, it's a horizontal line from the top of the stack to the centerline of the seat post.

When I setup a new bike, I set the saddle position relative to the BB first, then go on to comparing the reach to the bars.

tomato coupe

This is it in a nutshell …

urbanknight

This is where certain measurements tend to become more important. I have long thighs but short shins, which makes me require a LOT of setback for the saddle and I won't buy a bike with more than 73.5° STA (preferably 73 or less). For you, I would be tempted to say you just need a much longer stem. Since you're a seasoned rider, you have a baseline to start with. Is there something you don't like about the fit on your current bike?

spinconn

Yup, old age is about adapting to diminishing capabilities without giving up.

This bike is my most relaxed geometry of all and I got it because my old body could not deal with an aggressive geometry for any more than a few miles. It is more upright than I was used to and is an entry level bike that I figured would be replaced with a better one if it resolved the issue. It worked so well I just kept it and that worked for the last 2 years but now it is not enough.

I want to get even more upright. Well, no, I don't want to, but I need to. I figured I could use this bike for a starting point to estimate what specs might work for me now. I am not terribly gifted with trigonometry knowledge and understanding so while all of the comments have been appreciated, and informative, some are also over my head.

So, today I travelled more than usual to visit a couple of bike shops farther away and took some test rides. As we all know, nothing beats a test ride and I learned a lot. For starters, I learned that I am going to just be patient and travel farther until I ride one that fits just right.

I am grateful we have so many different types and brands of bikes to choose from, and so much knowledge on this forum.

SoSmellyAir

What stem length and angle are currently on your Contend AR4? You can try a stem that is shorter and/or has a more positive angle, which would put you more upright. Consult this stem calculator: Stem Comparison Tool | yojimg.net.

I have just ordered an endurance bike, and in my research, the recently released Pearson Forge has the highest stack:reach ratio (at least in my size): Carbon Road Bike | FORGE - Pearson1860

Maelochs

A rider with short legs and a long torso and arms needs a shorter seat tube and a longer top tube--or needs a very long stem and long-reach bars. Reach is great but it only measures from the vertical off the BB … Reach might be enough, but it depends on how short the rider’s legs are. Anyway … yes, the OP needs a bike with a long front end and an upright but short seat tube, I think.

I already explained the method I use …. Others’ methods will vary, but I, like the OP, have odd proportions and have learned how to adapt.