Buy the Right Size Road Bike -- Making Decisions
https://vimeo.com/251048545/bc15fa750c
First we need to draw basic conclusions about the setup of our current bike. All of the components need to be considered together and we need to determine if the bike itself is telling us a story.
First we’ll start with the parts that are somewhat flexible -- those things that we might even have some control over and can change on the next bike. So we’re going to note the setup and position of these parts on your current bike and from this we’ll grade each part on a very rudimentary scale so that we can quantify the changes we’ll want to make to the new bike.We’ll be looking at each part through the lens of whether it points us toward making the reach and height of the handlebars lower/higher or shorter/longer.
For instance if you have a 60 mm stem on your current bike -- this being very short we would grade as needing a shorter reach on the new bike so we would note “Reach(-)”. There will also be degrees of changes needed, so for instance with that 60 mm stem we might grade that a (-3) meaning we need a large adjustment (shorter) of the reach for the new bike. I’ll go into this more explicitly after we collect this information, but our over-riding goal is to incorporate as many of these adjustments into the geometry of the frame so that we don’t need to make compensations with the parts as much since this can lead to compromises in handling or balance on the bike.
Using our 60 mm stem example, we would be looking for a bike with a shorter effective top tube measurement such that it allowed us to then use a more “standard” sized stem around 90-110 mm long. Having our positional changes built into the improved geometry of the frame allows us to make fewer compromises.
Cockpit Reach
Saddle fore/aft
Saddle forward -- shorter reach (effective top tube)? Reach(-)
middle of the rails -- reach is good?
Back on the rails -- longer reach? Reach(+)
~4 cm of total adjustment, 2 fore and 2 aft so the scoring reflects this
(-1) - (-2) fore, neutral, (+1)-(+2) aft
Stem length
60mm (-3); 70mm (-2); 80mm (-1); 90mm-100mm(0); 110 (+2); 120 (+3)
I want to make clear that having a 110mm stem doesn’t mean that it’s too long -- merely that there is room in the reach to play with should we need to make adjustments to the reach in some way
Seatpost Setback
0mm -- shorter reach (-) ; (-1)
10-25mm -- no adjustment
>25mm -- longer reach? (+1)
This measurement will only be given a +/-1 because the saddle fore/aft will factor along with it
Handlebar Height
Stem Rise
(-10* to +10* -- 0) (+12 to +15 -- +1.5) (+15 to +20 -- +2) (+20 to +25 -- +2.5) (+25 to +30 -- +3)
At 90mm 10* rise = 1.5cm rise
Headset Spacers*
25-40mm spacers -- Stack + ; (25-30mm, +1) (30-40mm, +2
10-25mm spacers -- no adjustment*
0-10mm spacers -- Stack (-) ; -1
*We can only read so far into this measurement because most riders have had no choice in the matter how many spacers they were left with on their bike. So if you have a bike and all the other signs are pointing toward needing more head tube length and yet you only have 5mm of spacers under the stem because that’s how you got it, we won’t assign any meaning to the lack of spacers (we certainly won’t give it a check mark for a shorter head tube. We’ll simply consider that when looking for new bikes -- if they have the full number of spacers available then we might consider this bike to be considerably further along towards being a good fit.
What Now?
So now we need to consider the final score of our bike’s stack and reach.First look at the chart for each, and consider if the numbers represent a pattern? Do you have minus numbers in all or most of the “reach” metrics? Do you have “plus” numbers in all the stack metrics? Vice versa? Either way, how we proceed is pretty clear….if your reach numbers are all negative, then we’re clearly going to be looking for a bike with a shorter reach/effective top tube than you currently have. (How much shorter? More on that in a bit)
But what if there’s discrepancy? For instance for reach, what if the saddle fore/aft is “Reach -2” because the saddle is slid forward moderately, the stem length is “reach 0/neutral” because of a 90mm stem and the seatpost setback is “reach +1” because of a 27mm setback post? This is where it gets tricky and we have to look at two things:
Namely, how did you determine your saddle fore/aft position? Was it slid forward because you were trying to shorten the reach of the bike, or was it slid forward to optimize the hip position relative to your feet? And how comfortable are you on the bike and do you have symptoms as noted in the previous section that you struggle with?If your saddle fore/aft position was set in order to shorten the reach instead of optimizing hip position then we can take this scenario as a net negative -- meaning we need to shorten the effective top tube on the next bike. Even if the saddle position was set for the hips, if you have on the bike symptoms -- saddle issues, hand pressure, neck/shoulder discomfort, back pain, knee symptoms etc -- then it’s likely that we’re still going to want to err on the side of a shorter effective top tube on the next bike. In general the golden rule -- a small bike is usually easier to fit than a slightly-too-big bike -- applies.
Notes on Long Stems (and more)
You’ll recall that in numerous instances I’ve mentioned that it’s much easier to fit a bike that’s a little (or even moderately) too small than one that’s even a little too big. This has ramifications for what we’re doing here.I need to make clear that even though we’re assigning a (+) value to stems longer than 110 mm this does not automatically mean that we’re going to be looking for a bigger bike for you in your next purchase. For example if you have a 110 mm stem(+2), a standard setback seatpost (0), and your saddle pushed back on the rails slightly (+1); this would give us a total score on the length of the bike of +3. BUT, this doesn’t mean you should go out looking for a frame that’s 3cm longer than what you currently have. This is because couched in the idea that a smaller bike is easier to fit, is the notion that steps we take to make a bike longer (via a longer stem and/or pushing the saddle aft on the rails) have a much smaller negative effect on the bike’s balance, handling and overall fit than the steps we take in order to shrink it.
For reasons that have to do with how our weight is draped over the bike, negative effects are rare even when we go to extremes in stem length (130 mm? 140 mm?) saddle aft, or seatpost setback. But slide the saddle forward a little, and shorten the stem to 70 or 80 mm and often bad things start happening -- the bike can feel twitchy, we can struggle to get weight off our hands (uneven weight distribution), and the bike can create problems for us in general. This same phenomenon occurs in regards to bar height -- lowering it a bunch is often no problem, but go a centimeter or two too high and the balance of the bike can go wonky.
So there’s an uneven relationship when we’re adjusting bikes. Going back to the start -- why am I having you grade a 120 mm stem as a +3? Simply because only by noting down all the bike metrics can we see if there are conflicting bike parts -- i.e. a 120 mm stem (+3) with a zero setback seatpost (-1) and the saddle slid forward (-1). One part is giving us a positive number while the others are giving us a negative number -- something isn’t right and we may have just found a large opportunity to improve the size and fitting of the next bike. If all your parts are telling you to subtract from the reach of the bike (70 mm stem, saddle slid forward, etc) then you know pretty clearly that you need to go with a bike that has a shorter reach next time around. But if all the parts are giving you positive numbers, there’s a good chance that you won’t need to diverge drastically from your current geometry on the next bike.Whether you make changes (and by how much) will depend on what we find out in the next section where we go into the symptoms you experience on the bike.