Stated bike geometry that does not make sense
 

Attachment 563874I am interested in purchasing an REI ADV 3.1, but I am worried that the stated geometry is incorrect. The effective tube top is listed as 52.6. Based on the stack and reach measurements and in comparison with the ADV 1.1 I could not picture why its tube top was so short. Anyway, I input the bike listed geometry on Bike Cad and it spit out the the Effective tube top as 54.6. No matter how many times I put in the geo it still sticks with the effective tube top as 54.6 as based on the stack and reach measurements. Am I right to be concerned with this. Any thoughts or observations?
I am intensely interested in this since I may be forced to order sight unseen and I need to make sure I am making the right purchase. Thanks

Stack and Reach only is not enough data to calculate effective top tube length. The important missing number is seat tube angle. Unless you have other information that you didn't share I don't know how your are calculating top tube length either.

Having said this, 54.6cm is about right for a 700c wheeled bike. The way to achieve shorter top tube lengths is to employ a steep seat tube angle (75 degrees) which is a fudge and not good geometry.

If your a short person looking for a small bike that fits well you really need to be looking at smaller wheeled bikes. Seat tube angles are important and if you see seat tube angles of 74-75 degrees then its a fudge.

I did input seat tube and head tube angles into the BikeCad program as well as other metrics it asked for. Funny thing is, I did the same with the other touring bike, the ADV 1.1 (Randonee) and the program spat out the correct top tube length. Which leads me to believe they have a typo for their Medium size effective tube top.

Seat tube angle is 73.5.
Effective tube top 526
Stack 594
Reach 569

I must be hopelessly out of touch with current thinking. You're considering buying a bike, so why don't you simply sit on it, and maybe do a test ride and see how it fits.

After all fit is what it's about, so actual fit trumps any consideration of the numbers. OTOH - if you're a big fan of he numbers for some reason, why not bring a tape measure to REI, and gather the data first hand.

I love number crunching and research for sure. And, per my first post, I may have to order sight unseen. I live 2.5 hours from about 4 different REI Stores. Not exactly easy for test riding ;-) which would help narrow down the decision. My husband likes the idea that I can have the bike mailed to us instead of me driving 2.5 hours away to test ride and buy. But that is besides the point. Point of original question was on the accuracy of geometry of the Medium size ADV 3.1, specifically the Effective tube top of 526. Which when taking the other aspects of geometry into account, makes it seem inaccurate.

I still don't get the OP.

Both real and effective top tube length are stand alone dimensions, relating to the main triangle, and independent of all other dimensions. The length can be whatever the builder wants it to be, subject to some limiting factors related wheel size and overall wheelbase. What happens outside the main triangle, is stem height, reach, angle, etc. aren't relevant.

I don't know the bike, nor (to be frank) do I care, but it's entirely conceivable that the designer shortened the top tube on a smaller frame to maintain some proportion and avoid excessive forward reach for a shorter rider who might be expected to have a shorter torso.

I undrstand the desire to save time and money by not driving 5 hours round trip without knowing. So, why not phone one of the stores and asking if someone might actually measure a frame and report the facts.

If I can get my husband to allow me to go to REI, you can better believe a tape measure is coming with me! But also, if REI stats on the bike geo are off, people who can only purchase online might be in for a rude awakening if they wind up buying a bike that doesn't fit and have to return it, which cuts into their profits and customer satisfaction. Might save them and a lot of paying customers a big headache ;)

Too bad there were not any REI employees on BF that could confirm the effective tube top, stack and reach measurements with an actual tape measure as was suggested, and report back if the geometry is indeed correct on those points.

The size in question, is a size Medium for people 5'6 to 5'9.
https://www.rei.com/product/109339/c...v-31-bike-2017

OK, but that still doesn't give me a basis to try to ascertain whether the number makes sense or not.

I have no idea what other data you're using when you say that, but it's entirely possible that it's just a typo.
So, instead of hoping to find an REI employee here on BF, why don't you go to the source and look for an REI employee in a REI store. Pick one at random, phone them, ask for the bike department, and explain that you're befuddled by what may be a typo on the spec sheet, and ask if he'd be willing to measure and confirm.

Whatever the OP does, I would not recommend making any decisions based on that spec sheet-- it's bonkers. There's only 4mm difference in reach between the smallest and the largest, and the L frame somehow has a longer reach than the XL.

I appreciate your suggestions and efforts to be helpful. I edited my previous post to include a link to REI's website for the geometry of the bike in question. Anyway, I will call them sometime tomorrow, it's too late now they close at 9pm, and ask someone in the bike department to measure for me. Hopefully I can have more of a basis to make a decision on what to purchase by then. I am wanting to take advantage of the member discount pricing on their bikes, which is why I thought I might find some practical suggestions and intelligent discourse on this message board in advance of my purchase.

After a bit more digging, it seems there is a typo with the effective tube top measurement in the size medium. If the ADV 3.1 is the same geometry of the 2016 Mazama, the Mazama effective tube top measurement is 54.5.

Mazama
Frame Size Medium
Height Range 5'6"-5'9"
Effective Top Tube (cm) 54.5
Seat Tube Center-Top (cm) 48
Standover Height 31
Wheelbase (cm) 104.2
Chain Stay (cm) 44.5
Fork Offset (mm) 50
Head Tube Angle (degree) 71
Seat Tube Angle (degree) 73.5

The 526mm top tube length at 73.5 degree seat tube angle has to be an error. The problem is that its hard to know which figure was the error and which is correct.

I'd strongly urge O.P. to go to one of the nearby REI stores and try the bike out before buying it. (I drove 4 hours each way, back when I bought mine!) It's cheap insurance to make sure you can get the bike to fit you, and figure out what, if anything, needs to be changed to make it fit. It also gives you a chance to see if the ride is as great as web-surfing indicates it could/would/should/might be. And arrange with the staff to give it a decent ride -- 3-5 miles instead of around the parking lot.

I agree that sizing by feel is more reliable than by numbers.

I drew up the bike in AutoCAD. Yeah, I am pretty certain the TT listed in the specs is off ~2cm.

REI stands behind their products. I can't imagine any issues if the bike were to arrive and the TT was not as per spec with returning it. But I would do my homework first to know what I was going to do if the bike does indeed have a longer TT. Deal breaker? What am I going to do? Do I have another option? The bike shown on the website has a decently long stem. Going 2 cm shorter should work well. (Some gentle negotiation might get you that stem for not a lot of money if the bike isn't at spec.)

Ben

Thanks to all for your responses. Going to try to make a trip up to REI in Pittsburgh today for a test ride. I am hopefully going to be coming home with either the ADV 1.1 or preferably, the ADV 3.1. Whichever one has the most comfortable reach for me and keeps me upright-ish enough. I live 20 minutes from the C&O Canal, which is my prefered place to ride. My present bike, which will hopefully soon be my husbands, is a Jamis Coda Sport 2012 model, size 19. Which is a little too big for me reach wise. I am 5 foot 7.5 inches tall and inseam about 31.25 or there abouts. Anyhow, I have made the Jamis doable with a high rise stem, did 30 miles on the GAP last year, plus multiple shorter day trips on the C&O and my main complaint was my hands, wrists and neck. Too much weight on my hands and not upright enough for neck comfort. To actually feel more comfortable riding I have taken to steering the bike with the ends of my fingers, I know, not ideal. Anyway the proof will be in the pudding, so to speak. I'll post a pic with my pick hopefully later.

I agree wholeheartedly, but numbers help get you in the ballpark, which is why I was puzzled. I was so set on ordering the ADV 3.1 because of the advertised shorter tube top, I almost ordered it sight unseen which could have been a big mistake for me personally if it doesn't fit right. Anyway I am going to test ride as suggested before buying so I will be in a better position to make a correct decision. Thankfully REI has the 1 year return policy. I have been burned twice before purchasing bikes that were too big for me, don't want to make that mistake again. Which is why I have come here for advice from knowledgeable people.

Can't you just message REI directly? :)

OP, did you end up buying the bike? I tried the medium and large frames about a month apart and didn't notice much difference except in standover height. Despite trying to become your neighborhood bike shop, REI's not that great if you have no idea what you're looking for. I felt like there wasn't much care done in building the bikes (bars not flat, seat too far forward) and they couldn't even get my seat height right. Basically, it'd be great if I could rent a bike like this for a week or so to REALLY understand its limits. I was looking at the ADV3.1 as the bargain clone with a lot of features, but I am now more interested in trying the Salsa Vaya and Kona Sutra... buy the best bike you can afford, buy it right.

I did drive to Pittsburgh and try the bike. It fit for the most part, but I hated the handlebars. I would have liked to switch them with the Salsa cowbell bars (which has a much shorter reach) and a shorter stem, and a seatpost with more setback. I am not to fond of the color of the bike either, no gloss to the finish, but would have been all over it if it fit without doing a whole bunch of stuff to it. The bike shop person didn't seem all that interested in helping me out. Besides, with all the changes it would have been more expensive, which my husband would not have appreciated since it is not exactly cheap anyway, even on sale. I went home sized up my own bike again and purchased some Nitto Albatross bars, a velo orange shim to make the handlebars fit my stem, some Ergon GC1 BioKork Grips, a new saddle and some brake and shifter cables. Watched a whole slew of youtube videos and did the conversion myself to swept back bars. The conversion was a success, the bike fits, it looks awesome if I do say so myself, and it was a whole lot cheaper than buying a new bike!
https://www.dropbox.com/s/mmij76e7fi...05012.jpg?dl=0

Well done. So your husband won't be getting your bike after all?

Thanks! Well not this year anyway;) All I want to do at this point is ride it. The C&O and GAP are calling my name. I am hoping we will get some good rides in this year before weather turns wet and muddy again. We work for the school system and have the next month and a half off so looking to take advantage of it.

That's a neat looking bike, several orders of magnitude better looking than the REI offerings and the vast majority of black bikes seen today. :-)

I'm puzzled, though. It's none of my business, but why doesn't your husband buy a bike for himself? If your Jamis is the right size for him, why not buy a 2nd one and adjust it to his liking? Does he have a bike already? Or is he not all that excited by riding? (My last ride with my wife was in 1981....)

So this is/was the Mazama, right? I'm sure the handlebar is an acquired taste.

REI's color choices are doing them no favors this year. Their stores are a sad La Brea tarpit of black mountain and roadies with poo-colored touring bikes. The satin-blah painted fork crown on the formerly Randonee is especially weird.