NOS88

I've a custom build and professionally fitted bike that feels great on any ride. Recently, I had the bright idea to see if I could get four of my other road bikes setup with the same cockpit measurements. I figured it would be easy. I would just take some key measurements:

1. Seat height from saddle top to center of pedal spindle.
2. Reach from seat center to center line of handle bars.
3. Center of saddle in relationship to center of bottom bracket. (I've the same saddle on all five bikes.)

AND, number three is where I started to run into problems. I can get the same reach from center of saddle to center of handle bars, but I get slightly different measurements in the relationship of saddle center to bottom bracket center. It’s only off by 2 or 3 mm in one direction or another. So, I thought I’d try swapping handle bars with different reach and/or different stem lengths to see if I could get it spot on. (Lucky for me I have lots of spare parts.) OK, so I was able to narrow down the difference a wee bit. But then I notice that the center line on the handle bars is different in relationship to the center of the front wheel axel.

Now, I’m well over 14 hours into this little experiment (over a period of six days) and I’m realizing that there is only so much that can be done to make a bike that is just a little off, in terms of fit, actually fit completely proper. And, I haven’t even started to tinker with things like handle bar drop of ideal saddle tilt. This saddle tilt thing is strange too. On the custom bike I’ve got the saddle perfectly flat. Yet that position on three of the four other bikes doesn’t seem to work. One two, it needs have the nose up a mm or so and on the third, it needs to be up even more to feel right. So, I’m now thinking that custom is custom and anything else is an approximation. I’m giving up the quest for now. That is, unless any of you have any ideas to get me unstuck.

bruce19

I hate these posts. Now I have to actually think. Damn. A couple things that leap to mind. How similar are frame tube angles? And, I usually don't measure seat height from seat to center of bottom bracket. I usually measure seat to pedal spindle. Are all your crank arm lengths the same? I've only set up road bikes but have been pretty successful.

NOS88

I'm measuring my seat height the same way you do. Three of the four bikes have the same frame geometry but different top tube lenghts. One of the others is 1 degree steeper in the head and seat tube with a top tube 2mm shorter. The other has the same length top tube and 1 degree steeper in head and seat tube. I don't know about fork rake on any of them.

tomgdaly

1. Centre of saddle height from bottom bracket.
2. Nose of saddle setback behind bottom bracket. The most accurate way of doing this is to place the back wheel against a wall and measure the distance horizontally (1) from wall to bottom bracket (2) from wall to tip of saddle. Divide and replicate on second bike.
Both the height and setback are now the same - seat tube angles don't matter.
3. The only variable left is stem height and reach from saddle.

PatW

It can drive you crazy can't it? I just go out with an allen wrench on a ride and adjust the seat multiple times until it "feels" right. Even a tiny adjustment makes a difference. Even differen saddles will give different results.

stapfam

Boreas fits perfectly and when I got the TCR- I tried to set it up the same. Even down to same compact bars etc. Near as dammit- I got them exactly the same but the TCR did not feel the same. In fact it was pretty uncomfortable after a 50 mile ride so started tweaking the fit on it and got it right. Quick look at the bikes and they appear to be almost the same but get the tape out and there are differences. That was when I realised that there are too many variables in bikes to use common factors in setting them up.

My main concerns are saddle height and fore and aft of it. After that it is down to getting the bike comfortable and that can take years.

icyclist 

How about another fit with another bike? If it's different than the fit you've already had, then you'll know that either different bikes require at least slightly different fits, and/or that a perfect fit is actually critical.

I have several bikes, they are all set up in similar, not identical ways. I like each of my bikes.

Camilo

I'm having a hard time following the nuances of the thread, so I apologize for any redundant comments. But this park tool chart/guideline is pretty straight forward.

https://www.parktool.com/uploads/file...sitionroad.pdf

The trick, like with all bike fit is to start with the saddle - the position over the BB and height above the BB needs to be exactly the same which requires careful vertical and horizontal measurements. You need to use plumb bobs, levels or both to get them accurate. It can really be fussy. You also need to tweek for stack height of the shoe/pedal combination, which can easily be 1/2+ cm different, which is signficant. Tweeking for the nuances of different saddles is needed if they aren't the same. Tweeking height (if needed, for example, for different pedals, shoes or saddle) can then affect setback, and adjusting setback can in turn affect height. So you have to be careful and go back and forth a little. At some point the changes are so small as to probably be insignificant, but if you are casual about it, they can also be pretty significant in terms of comfort pedaling and also in how they can affect reach to the bars by a cm or so.

But, starting with the saddle, once you get them identically placed, it's pretty simple to adjust reach to the handlebars or brake hoods and saddle/bar drop.

In my (limited) experience, it's impossible to get the same "feel" and fit unless you have the exact same handlebars and levers on both bikes. I have two bikes which measure very close if not identical to each other in where the saddle is in relatinship to the bb. Both use the same saddle. Both have the same reach from the hoods to the saddle nose and saddle/bar drop.

But the bikes feel totally different because the handlebars and shifters are different. Different length stems are needed to get the reach about the same, but the different dimensions of the bars made me decide if I wanted the bikes to be identical in the tops, drops or hoods. I chose hoods. But still, I'm much more comfortable on the hoods on one bike compared to the other because of the subtlties of reach and hand position caused by the way the hoods sit on the bars and the shape of the bars and hoods. Both bikes are rideable, but I definitely prefer one over the other. I've tried tweeking, but have decided that if I want the bikes to be identically comfortable, I'll have to match the levers and bars too.

Hope this helps.

CrankyFranky

It might be interesting to do it the other way around - to have professional fitting done for you on all of 'em. Then, compare how different your critical measurements are. If you're still looking at 1, 2, or 3mm difference, well chalk that up to your adaptability - after all, you do have different TT, diff angles, not to mention rakes.

I bet that even if you do this, they will all still feel different.

I had an somewhat similar discussion with my orthopod who also has written for Rivendell in the past. He told me (paraphrasing) "you can discuss theory about this and come some conclusion, but you may be overthinking it - the best thing you can do is to have the bike professionally fit to you."

donheff

OK, so the custom bike fits you well and informs you of the numbers you want to match. It would seem that you would start with the crank to seat length first, setup the seat for proper knee over pedal next, and then see where you are with respect to the handlebars. If they are off you would approach that with stem and/or bar changes to get close to the right numbers. Once you got it all together you would probably find that the bikes are so different the new one doesn't feel right. Time to see a pro?

AzTallRider

Personally, I think that trying to make bikes with differing geometries match exactly is both futile and unlikely to produce the desired results (those being comfort and performance). The most common denominator is saddle height, but even that can vary a bit between two "perfect" setups. It's because what matters in fitting is dynamic, and many factors come into play as you pedal the bike. If you have greater bar drop, that might influence the saddle angle, which might influence the saddle height. Being a touch more stretched out may mean you need to be a touch higher... or lower. It all comes into play, and what matters is what happens when you are pedaling, not when you are in a static position. Different geometries will handle differently, and that may mean that you want to be further forward on one bike than another bike with different angles/wheelbase/fork/etc. You are seeing that when you expected to see the front axle in the same place and it wasn't. What matters is the handling and how you feel when riding the bike.

Proper fitting is a process, not a single event, and the 'perfect fit' changes with your fitness and goals, which may also differ from one bike to the next. IMO, you can't just peg the relationships that work on one bike, and apply them to another.

bruin11

https://velonews.competitor.com/2012/...shimano_219260

Timtruro

I don't believe there is only one correct or comfortable fits, regardless of geometry etc. you can over-engineer this like anything else.

Barrettscv 

Hi,

Try this;

Adjust the saddle to the crankset first, ignore the reach for now. The seat-tube angle might not be the same on each bike. Use a level and a plum to set the location of the saddle.

Once the crankset to saddle relationship is set, adjust the reach and handlebar-to-saddle drop.

You might be buying new stems.

qcpmsame 

NOS,
The only thing I can see that pops out is when you are taking the seat to center of bottom bracket measurement the height of the bottom bracket from the ground would have to be the same on every bike I would think. If a bottom bracket of a bike is higher or lower than the custom bike this difference has to be considered in making all the measurements the same. The different heights if they exist would also change the angles of the head tube and the down tube wouldn't they? I think this would make a difference. Maybe so, maybe not.

As said above, you can over engineer these points too. (This coming from a man with engineers disease really bad.)

Bill

tsl

I haven't read through the entire thread yet, so this may already have been covered.

First, numbers two and three are reversed. The second thing you do is set saddle setback from the BB. Saddle to bars is the third thing.

Second, the measurement should be to the nose of the saddle, not the center.

To do this, you'll need either a plumb bob or a drywall T-square, and a four-foot level.

Park Tool has a great guide to recording the measurements, then transferring them to another bike.

https://www.parktool.com/blog/repair-...-position-road

It's worth all the extra effort, BTW. I had this done at my LBS last October. All four of my bikes were a little off from one another. They're all withing a mm or two now and it's so much nicer when I switch from one to another

bmar

I've used the Park guide, but I find it a bit difficult to make accurate measurements. I like this method much better:

https://velonews.competitor.com/2012/...tically_216035

We used this with great success on a European trip where we rented bikes.


Bill

bruce19

This is where I start too.

bruce19

According to a book I have there are three ways to size a bike frame. This was written before the era of sloping TT's. They are: Traditional, "Eddie" (for Eddie Mercyx) and French fit. I won't go into all the details but the Traditional is a racing fit and yields a smaller frame. The French fit yields the biggest and the Eddie is in between.

BikeWNC

^^^This. I have setup so many bikes at first trying to make each identical by measurement but discovered each bike felt different anyway. Even if everything is transposed perfectly, the bike will feel unique based on its geometry and how you balance on it. Get each bike close then ride it to tweak the contact points so it rides and feels like you want it to. In the end, one bike might always feel better regardless and it is the bike that has the best combination of geometry and fit that suits you. That doesn't make the other bike unrideable, they will just never be as perfect as the "one".

nkfrench 

I bought a "backup" bike at the same LBS that fit me on my "good" road bike. We swapped out stem, saddle, handlebars and did a lot of work to match the fit. The geometry was very similar between the two bikes to begin with. I left my good bike with the shop so they could compare the two side-by-side doing the setup.
And I still could not ride the new bike more than a few blocks without having severe knee pain.
I had dual campus:SPD pedals on the new bike, MTB SPD pedals on the good bike. So I got the same brand of MTB SPD pedals installed; that solved my knee problems.
It is amazing how locked into a certain fit and bike frame/components you can be after thousands of miles on one bike.
I feel like I could have been in the story "The Princess and The Pea".

donheff

I wonder if the pedals would have made same the difference even if the rest of the fit was no so close. Next time start there and see if the rest is really so critical, particularly if you get a bike with a different geometry.

BluesDawg

I generally start with the same kinds of measurements listed here and then I start fiddling with it until it feels right.

volosong

"might"??? No, this is wrong. You will be buying new stems.

I got a BG fit several weeks ago and am a bit unhappy with it. There were some radical changes made, and I knew from the first ride after the fit that something was not quite right. My right knee now hurts to the point where even if I'm not riding, it hurts. The worst is that they have not given me the measurements, either pre or post. I'm going to stay on top of that and demand that they give them to me.

However, some good education has come out of it. As a result of the fit, they lowered the seat a bit and moved it forward. The tech said, (as confirmation to what others have said), that the seat position is set first, and is a constant for a body's measurements. Then the cockpit is set, which is more of a personal preference.

Some of my aches and pains have now been mitigated as a result of the fit; some are still there, but to a lesser degree; and a new pain has manifested itself, (the a fore mentioned right knee pain). I have a long charity ride scheduled this Saturday. They better fit me in on Friday.

NOS88

Update: First thanks for all of the responses. They were appreciated.

What I’ve done is taken my custom built and fitted bike as the base. I then used the Park Tool size chart and carefully measured all the elements using their reference standards. The road bike I picked to work on was the one closest to the base in terms of frame size as measured by top tube and seat tube.

Both bikes have the same seat, Dura Ace component group and crankset. So, I then set about trying to duplicate the measurements from the base to the other bike. It took a little over two hours. (Even though nothing was being cut, I was measuring twice). Today, I took the finished work as my commuter. I must say, it felt fine. But, as several of you have pointed out, it wasn’t the same ride, which I wasn’t really expecting. In fact, the first thing I noticed is how much more compliant the wheels on it were. The base bike has Ksyrium SL wheels and the test bike has Mavic Open Pros on DA hubs.

So, long story short, I’ve several reactions to this whole exercise. First, having the measurements of my best riding bike seems worth the investment. Should I ever need to swap something out, I’ll have a starting point for getting it right. Second, I think there is a SLIGHT advantage to having all my roads bikes set up as close as possible to one another. And finally, there are so many things that go into how a bike rides and feels, that the only way to get a carbon copy is to get two of the same bikes, all set up in exactly the same way, and with the same equipment down to the same inner tubes.
With that said, I’m glad I took the time to do this. It gives me an excuse for N+1. When asked, “But don’t you already have a bike like that?” I can answer, “Yes, but they won’t ride the same.” And, I’ll say this from a position of real knowledge.