raria

Hi,

This has always confused me so please help me get unconfused!

With touring bikes I've found that there are two main types of geometry.

Geometry #1 : The geometry found on bikes such as the LHT or Trek 520 where:

a) ST and ETT length are approximately the same
b) hence ETT varies depending on size.

See attachment 1 for an example. Its the LHT geo chart.

My question does not concern this type of bike. Instead it concerns bikes of geometry #2

Geometry #2 : The geometry found on bikes like the Fuji Touring, Windsor Tourist etc where:

a) ST and ETT length are not closely related
b) hence ETT varies just 3-4 cm across all sizes. For example the 49cm ETT is 54.5cm and for the 58cm ETT is 57.5cm

See attachment 2 for an example. It's the Fuji touring geo chart

With this second geometry I find it hard to understand what's a good fit by ETT length which is the typical technique I use. I like to ride a road bike with ETT about 55-56cm which normally fits one size in most bikes. But for the Geometry #2 bikes this fits 4 sizes for the Fuji 49cm (54.5 ETT), 54cm (55.4 ETT), 56cm (56.6cm ETT) and 58cm (57.8cm ETT)

Realistially how will it differ/matter if I get the 49cm, 54cm, 56cm or 58cm?

Currently I have a 54cm but whose to say the others are not better fits and I should just change the stem length by a cm or two to get teh 55cm ETT length I like?

Brian25

I do not know about you, but I am short and like most people I am preconditioned for at least two things A) Mount/ dismount from the left side of the bike and B) swing my leg over the back of the bike. I used to tour on a 52cm bike, and now that I am touring on about a 40cm, I do not need to swing my leg up and over my tent and pad that are on my rear rack, I am able to step over the top tube (much easier). Most tourists 1) buy a bike that is too big and 2) Do not consider the step over- ability when buying a bike. 3) And ride with a silly upright position. I can not speak for you, but for me, as long as the effective top tube is 52- 54 cm I am good to go with the right stem/ spacers.

Tourist in MSN

When I get on the bike, I (1) stand slightly more forward than you would from the swing-leg-over-back-loaded-rack method, I (2) bend my leg at the knee quite sharply, and (3) swing my knee over the top tube in front of the saddle. Thus my knee has to be high enough to clear the top tube, but not clear the saddle for height.

raria

Thanks I get it. Your saying the bigger bike will be harder to mount with a fully loaded deck. But I don't find that a problem. I just tilt the bike over and mount with it at 45 degrees. I rarely tour with more than 25 pounds so its not a problem holding the bike.

The problem to me is for these Geometry style #2 bikes. There are so many frames with about the same ETT length that I'm comfortable with and I'm lost to know which one to get as I don't know the ramifications.

jefnvk

Just a consideration, though: I didn't have an issue, until I had an issue. Wrecked on a tour and pulled my groin, all the suddenly that became incredibly difficult to do.

Not a great argument against going bigger, just something to keep in mind.

Tourist in MSN

Years ago when top tubes were always horizontal, there was a theory that you should have a fist full of seatpost between the saddle and the frame. But with sloping top tubes, that no longer applies.

I think you need to look at stand over height and then probably get the tallest frame that is not too tall for standover. If in doubt, go with the shorter of the two that are closest so you do not have a stand over problem. With shorter frame size, you might find it is hard to get the bars as high as you want them. A larger frame size might also be less likely to have toe overlap, but if the top tube length is nearly the same on several frames the wheel base probably is nearly the same on all those sizes too.

The windsor tourist photos I have seen, some had quill stem and some threadless. Not sure about Fuji. Adjusting the handlebar height and reach is different with different stem types. I just bought a new bike last month, needed a new stem to change the reach and bar height, but with threadless it was easy to figure out what stem to buy and bought it. Quill is harder to change.

raria

Other people mentioned the stand over height but not the head tube length. Your right they vary quite a bit and on smaller frames the stack would be a good deal smaller (even though the reach would be similar) which may not be comfortable for riding.

mstateglfr 

The #2 geometry is all wonky because those frames use a variable sloping top tube. The smaller the frame, the more severe the slope, which amplifies the difference between top tube and seat tube.

the best way to compare your current bike to these options would be to compare stack and reach measurements because that allows different geometry frames to be compared equally.

those are really wonky measurements, regardless of sloping top tube. The smallest bike they offer has 535mm of ETT and a significant HTA.

McBTC

You may have noticed that on both charts the head tube angles for all sizes are relatively slack compared to non-touring road bikes (and consequently, tour bikes oftentimes have more mechanical trail). Tour bikes usually have relatively longer wheelbases to better accommodate larger tires and fenders (e.g., more space between the rear wheel and the seat tube). And, the forks and rear drop outs have eyelets that can be used to mount racks. I noticed only recently that there has apparently been an urgent discussion in recent years about tour bikes with less trail as better for those who like to mount their panniers on the front instead of the back.

boomhauer

I went with the smaller of the two frames when picking out my Surly Troll and had some regrets.
Since I like to sit perfectly upright I picked a medium frame instead of the large. My thinking was that the bars would be closer to me so I wouldn't have to bend over.
Much to my surprise, I'm at the limit on the seat post, right up to the line. Also, I had to buy an extension for my uncut fork. I get to sit upright, as I wanted, but my steerer tube looks excessively long.
None of this is really a problem; it's the most upright comfortable touring bike I could ever hope for. I love sitting perfectly upright so I can look around at the world.

Tourist in MSN comments are right on the mark. I wish I consulted him before my frame purchase

raria

How do you mean wonky? In what do you mean by hta question mark

Tourist in MSN

To elaborate a bit more, my comments suggesting to focus most on stand over height was specific to the OPs comments about bike models where the different sizes have very little variation in top tube length. When there is more top tube length variation between different sizes, you need to focus more on that too.

mstateglfr 

i think the geometry of the #2 frames is wonky....meaning curious/odd/different.
the head tube angle(hta) is extreme and that is common for smaller frames with 700c wheels due to wheel clearance and toe strike.

Thats coming from me though and i prefer a bike with 72/73 degree hta and sta.

raria

So I just happened to be browsing the Trek Hybrid FX geo chart (see below) and it has the same whacky situation.

ST difference from S to XL is 19cm
ETT difference from S to XL is 4.5cm?

So with these whacky geometries what happens with the bigger sizes to accomodate the minimal increase in ETT length? Taller people naturally have longer arms and torsos. So do they make you more hunched over to negate the minimal increase in ETT?

McBTC

The bigger frames generally come with longer stems and raising the seatpost to accommodate longer legs can take the seat further from the handlebars and stretch a rider out, perhaps requiring a rise in the bars or flipping the stem and adjusting the seat on its rails. Additionally, going to a setback from a straight seatpost also opens things up. A figure you do not have listed is the 'stack' and that may be something of interest to get a handle on if you want a bike with more handlebar rise without a lot of spacers or a stem extender to get the bars, e.g., up level with the seat.

stardognine

Yeah, I noticed that right away, about my ST600. The TT length increases quite a bit, as ST length increases. So you need to pay attention to BOTH, sometimes. 🙂

raria

As you say since the ETT length is tightly linked to the ST length there are only 1 or at best 2 sizes to consider.

But for type #2 bikes just based on ETT are all about the same. Now I could of course ride them all, but have you ever been to a LBS which stocks even one Fuji Touring let along multiple sizes of Fuji touring?

Tourist in MSN

I have not worked for a bike manufacturer, so my guess is only a guess, not based on fact. But, I am guessing that when all of the different sizes use the same wheel size, that the designer can't shrink the top tube as much as might make sense for the smallest sizes.

In this case, the smallest frame size has a seat tube of 38 cm, the wheel radius is roughly 34 cm. Thus the top tube can't get very short when the wheel size is that large.

Also, flat bar hybrids used in urban settings that favor a more upright posture probably correlate to a shorter reach than a drop bar bike too. Thus, I can see how the larger frames would have a top tube length that does not get very long.

I know I did not answer your question, just throwing out a few thoughts.

djb

Here was my conumdrum looking at buying a Surly Troll--and wanting to put dropbars on it.

I tend to be comfortable on a ett 55 ish cm toptube bike for dropbars, more or less a medium frame. On paper, a med troll has a ett of 596mm, and a small 571.

Well, a small must be right right?
The more I thought about it, it didnt make sense for a 5'10 guy to be on a small frame, and ended up getting the medium and using a short stem (55 or 60mm) as well as drop bars that are not very "long" (distance from tops to where hoods are, and yes, diff bars have diff dimensions, which makes a diff)

bottom line, is that on paper, the troll didnt make sense, and I figure its because it was designed for mtn bike bars, ie with sweepback, and then of course they ended up selling them with Jones bars, which REALLY come back towards the rider.

so bar choice is a factor, and despite working around the oddness of a troll frame, a short stem works and the bike handles wonderfully, even fully loaded.