I am looking for some guidance and help understanding what’s going on, please.

Long story...short.

I have set set up my recently acquired Mikkelsen so that the measurements match my 2 other bikes. However, it seems when I ride the Mikkelsen, it causes my lower back to hurt. How can this be, when the other don’t?

Measurements set equal:
1. Seat set back to pedal (when pedal is at full forward) and cranks are same length
2. Seat height from center of crank to same spot on seat (same seats, straight up through post)
3. Handlebars at same drop when compared to seat height
4. Handlebars same reach from seat (to bars and to hoods).

Am am I missing something?!? In my mind (which could be wrong) these bikes are set up nearly identical...but my back hurts on one and not the other two.

Help???

Is the gearing the same between bikes? I.e. pushing bigger gears on the Mikkelsen?

Crank length different?

Gearing on the Mikk is same as one...easier than the other.

Cranks are ALL 175.

Seats are ALL the same.

I just don’t get it.

Ditto, Spaghetti Legs' questions. Any differences can influence fit and comfort.

Is the frame geometry identical?

Identical saddles, handlebars, brake levers/hoods, crank lengths, gearing, bar wrap, etc.?

I have two road bikes, an '89 Centurion Ironman steel bike, and a '93 Trek 5900, then Trek's flagship carbon fiber bike and still a very good bike by any standards. Both diamond frames, since Trek hadn't yet jumped on the compact frame with sloping top tube popularized later by Giant.

But it's taken months to get the Trek fitting as well as the Ironman. There were many small differences so I took a methodical approach, changing one thing at a time. I have an old C1-C2 neck injury, so fit is critical.

• The Ironman is a 57 or 58cm frame; the Trek, 56cm. Both fit me fine, but that's enough difference to affect reach, etc.
• The Ironman had a Selle Italia SLS Kit Carbonio, which I liked so well I swapped it over to the Trek. But it took months to find a suitable replacement for the Ironman, which now wears an excellent Bontrager Ajna cutout saddle. Without identical saddles it took a lot of trial and error adjustments to suit me.
• A year ago I switched the Ironman from the original 125mm stem to a 90mm. Huge difference in comfort. Recently I switched the Trek from the original 140mm to a 90mm and more contemporary stem -- similar weight, but fatter tube and more rigid.
• The Ironman's original classic drops have always been fine. I tried three sets of drops on the Trek before recently finding an FSA Omega compact that was a huge improvement.
• I'd already moved the aero brakes/hoods on the Ironman up higher, closer to the 1950s-early '60s style, and adjusted the brake lever angle to be vertical rather than splayed outward. Much better. But that didn't help much with the Trek because the original stem and handlebars were different from the Ironman.
• Switching to brifters with elongated reach on the Trek just made the fit worse. Too stretched out. It's only a few centimeters but felt miserable. Switching to a shorter stem and compact drops was a huge improvement.
• The Ironman has a single wrap of foam "cork" bar tape; the Trek has Arundel Synth Gecko, very thick rubbery stuff, and it's double wrapped over some generic foam tape. Some difference in feel on rough roads over long rides.
• The Ironman has 172.5 crank arms, the Trek has 170.
• Seat tube angles are slightly different. Top tube lengths are different.
• The Ironman had a 50/39 double chainring set (now 50/38) and 13-25 freewheel (now 13-28); the Trek has gone through several gearing changes before I returned to the Biopace 52/42 double and 14-28 freewheel it started with back in April.
• Wheelsets were nearly identical (not much difference between Araya CTL-370 and Wolber Super Alpine rims), but tires were different. I had 700x25 on the Ironman, and identical model tires in 700x23 on the Trek. Made a difference in overall feel. I recently switched the Trek to 700x25 and now it feels much better on chipseal and rough pavement.

Regarding gearing, I wouldn't say it makes much difference which combination of chainrings and rear cogs. As long as it has a decent range for my terrain, no big deal. And the Biopace sorta-oblongish-ovalish chainrings feel a little different but not a huge difference -- mostly I notice some advantage on climbs at a lower cadence.

But what really mattered was the gear steps. It's annoying when I'm too aware of the gearing steps, so I went through a lot of changes in chainring and freewheel combos to find a seamless shifting setup for both bikes, without jarring steps between cogs. That alone can save some muscle stress on long and/or fast rides on hilly terrain, with lots of shifting and cadence changes.

I think I've finally got both bikes set up to feel equally comfortable. But it took a lot of tinkering.

Are you measuring your reach from the specific saddle point to the notching-up/crook of the brake lever/shift lever hoods (where it goes from horizontal to vertical when you're riding "on the hoods")? Handlebars can have a lot of reach differences from the clamp to the hoods, and not many people call that out. I am a strident measure-er of bikes so that I get my fitment correct, so I understand when something ends up wrong. One of my bikes feels funny in spite of having my measurements spot on. I'll vary saddle-to-hoods drop a little, but this bike is pretty close to level, which should be fine, but I still need to drop the saddle 1/8" or so.

Saddle angle and hood angle can be different and thus variables. Keep posting, even silly posts like one word a post, to get to 10 posts, and then you can post pictures (upload from computer/"device") and that will help all of us!

Haha. I am well past the 10 posts. I didn’t include pictures, because apparently I only have older setup pictures of all of my bikes.

Measurements are are all from a specific point in the saddle. While the bars are different, the end result of reach and drop to the hoods are the same. I will post some pics tomorrow showing comparisons.

I have a similar issue with my stable of rides. All of the measurements are about the same, but a couple of the bikes when I take on longer rides above 60 miles, I have signifcant pain post ride.

I've deduced that the majority of this is due to differences in frame geometry - while the handlebar to saddle measurement may be the same - the angle of my hip to torso is not. Or my foot angle on the pedal might be different through the pedal stroke.

My solution is to follow the measurement s as a guideline and adjust and optimize for comfort.

Doh! Sorry, man. I had too many windows open and mixed it up with another single post member.

I measure from a sit bone position on my saddles--so that's my specific point. I understand what you're doing.

I also measure contact points from the sit bone position at the rear of the saddle. From woodworking I learned about "story sticks". One length of wood that holds all the needed measurements for a project. I rest the end of mine on the DS pedal spindle with the pedal in line with the ST. A pin on the other end rests across the saddle at the sit bone position - checks saddle height. I then rest that pin at the sit bone point with the stick reaching across the bars. A mark on the stick shows where the back of the brake hoods need to be (regardless of TT length, stem length and HB geometry). Holding the stick parallel to the TT helps measure saddle to bar drop.

I set all my bikes the same and they're all comfortable. My frames range from 56cm to 61cm with a couple of mtn bikes that talk inches. Then, again, I'm such a young'n it may not matter.

A friend is a trained and certified bike fitter. I saw that he measures reach from the front of a saddle vs the sit bone position. "Are all saddles the same length? I measure from where the sit bones are." "Ah, that's what they taught us." Hmmmmm.

I was talking to another certified fitter, Northeast regional business and reputation, years of experience. We stood next to my Raleigh Pro - fist full of seat post showing, 1 1/2" drop to the bars, all day comfortable. Sez he "Of course you know that your frame is too big for you." Ah.....

I'm somewhat skeptical of trained, certified fitters.

Get somebody to take your pic as you ride by, if possible in the same position on the bars etc.

Compare the pics to identify any possible biomechanical issues.

My own limited experience is that lower back problems are best resolved by sliding the seat forward.

Get good measurements and take notes as you make (small) changes

Mark Petry
Bainbridge Island, WA USA

Someone may already have mentioned this, but it can come down to fiddly little stuff like:

• Saddle tilt
• Handlebar tilt
• Brake lever position on handlebar

Have you had the frame/fork checked for alignment? I had bikes that gave me back pain, every time I used. One had a steer tube, replaced fork, issues gone. The other needed minor fork, and rear triangle adjusted, Again back issues gone.

I suspect the frame angles are different. Probably not much, but just enough to put pressure on your lower back. I also find the most valuable measurements to duplicate from bike to bike are stack and reach:

My 1st instinct is to saw slide the saddle forward a little and potentially tilt it up slightly.

But I also encourage you to measure something else, bottom bracket to brake hoods. See how that compares to your other bikes.

I try to get all my bikes to the same measurements, probably failing miserably compared to many members.

BUT, being a bit different is for me - THE POINT.
If they all fit feel and ride the same, why have more than 1?

i confess, most of my rides are sub 40 miles.
For longer rides I have a few favorites; the choice depends on terrain.

Good luck finding a solution to the back pain. Ride it more - you’ll find a solution or dump it. Is it a Trek?

edit: does the painful one have a shorter head tube?

I just went through a similar exercise with my two bikes, which have a similar somewhat relaxed touring geometry. The 58ish cm cheapo John Deere bike boom bike was very easy to adjust to be comfortable for hour + rides. The 56 cm Motobecane...it took me 2 months of adjustments and stem swaps to finally be able to ride comfortably (I think the root cause is that the frame is just a bit too small). I was actually about ready to give up on it. Glad I didn't though as, it's now comfortable and I'm eagerly pedaling 80+ miles/week.

What I learned from the this experience is: Two bikes that are similar in geometry and size can have significantly different setups to be comfortable.

Yup. I measure from where my sit bones park. Even with superficially similar saddles, or variations of the same model from the same maker, there are just enough differences that measuring from the nose or rear is good only for a rough baseline setup.

Ditto using the rail marks. Those aren't uniform even with different model saddles from the maker. And rail/saddle angles may not be identical, especially if one saddle has a more flexible shell for rougher terrain. So I can't just transfer the same rail alignment from one bike and saddle to another slightly different bike and saddle.

After that I'll ride a bit wearing my usual kit (pads in shorts/bibs make a big difference in fit), figure out where my sit bones like to park, then measure from that area.

That usually gets me within 1 centimeter of the sweet spot. After that I'll tote a multi-tool or necessary individual tools in my pocket for a couple of test rides and make adjustments during rest breaks. After a couple of rides it's pretty close to perfect.

I think it's best to start with the saddle position relative to the pedals. First make sure the height is the same. (are cranks the same length, pedals similar, cleat position?) Next tackle for and aft. KOPS is a good starting position for most people (mythbusters are full of it). If the OP has a bike that they are comfortable on, start with that. Best if you have someone to help. Sit on the bike in the saddle where you ride most of the time. Take the KOPS with a plumb bob. Note whether the string goes through the spindle, a little in front, a bit behind, etc. Now get on the new bike, and move the saddle until the plumb bob is indicating the same position. When that matches, then, get your handlebar position sorted out.