Fit/bike advice

[HugoBear]

I have 3 road bikes. One is a cervelo R3, size 54, with a 545 Tt. I run a 100mm stem. One is a strong ti, with a 535tt and 100mm stem, which a fitter said is perfect. The other is a 53cm Pegoretti duende with a 543tt and I run a 100 mm stem. I keep reading on the forum running around a 120 mm stem is optimal. There is a 52x52 Bedford on the forum, which I think would mean I could run a 110 to 120 stem. Would that potentially be a better fit than the bikes above? I feel a little stretched on those bikes but not really uncomfortable. Also, would anyone sell one of the three bikes and buy the Bedford?

[Dave]

To compare the reach of each frame you need to consider the seat tube angle. The Cervelo is 73 degrees. Angles that are steeper will lengthen the reach by about 1cm per degree.

A 100mm stem is about as short as I've ever use and I try to use a 110mm. One reason is to maintain adequate knee clearance, when riding out of the saddle. I use short reach bars (75mm) most of the time, so I can use a 110mm stem.

[carpediemracing]

I don't make a living fitting bikes so that's my disclaimer.

However I've experimented with fit pretty extensively and thought about what I want in a bike etc etc etc.

Basically a 120mm stem will put your bars a certain distance over your front wheel. Okay, a longer head tube will effectively pull back your bars relative to your wheel, but the idea is that you put a certain amount of weight on the front of the bike.

I've found through experiments etc that having more weight on the front of the bike will make it more stable. Do a simple experiment on your bike - go to a descent, do a "Pantani" tuck (seems like an Italian thing but he's the first guy I can think of that does it). Put your butt behind the saddle, arms on drops, totally extended arms, basically put your chest/stomach on the saddle.

That's the epitome of a light front end.

Now do a "Lemond" tuck. Again, he's a rider that used it, it seems to be a "regular" tuck. Put your hands on the drops if you want (or tops to be proper), lean forward until your head is as far forward as you dare. On my admittedly short bike I've burned the bottom of my chin on the front tire, descending at speed while looking where I'm going.

That's the epitome of a heavy front end.

To me the latter position is much more stable at speed. It may respond a bit slower at low speeds, for example you wouldn't want to steer like that at walking pace but you could do a Pantani tuck while fooling around at 4 mph and not screw things up.

Riding a 90mm stem on a bike that I actually like (my wife's) I thought something was wrong because it felt so unstable once I hit 35 mph. With a 120mm stem and everything lowered up front it was much more stable.

Keep in mind that the drops will change location if you go from a traditional bar to a compact or vice versa. My 120mm stem choice is based on a traditional bar. This means that to get the right reach to the drops (because that's where I am if I'm cornering hard, descending hard, in a tight situation in a race or group ride, i.e any time I might need to make an emergency maneuver) it means that I need a longer stem. In my case I went to a 140mm stem with a compact bar, losing about 10mm of reach. I'd try a 150mm but I can't find an appropriate one.

For me the bonus of going with the compact bar is that the tops are now 20mm further away. To me this is a great thing so I want to work with the reduced reach and drop. I'm still experimenting but my next step is to try the FSA Energy bar, a bar that has the same limited reach but has the drop of a traditional bar (but it seems that it's maybe 1 cm less drop due to the ergo/anatomic bend).

[carpediemracing]

Finally, having ridden bikes with shorter top tubes, a 52cm top tube might give you shoe/tire overlap. A 54.5 won't, nor will a typical 53.5. This may be something to consider or at least check out.

I never had a problem with shoe overlap when I had it but it was nice when I didn't have it anymore.

[Dude]

"A 120 stem is an optimal length" is an incorrect statement. The correct way is "A 120 stem is an optimal length for some people." Out of curiosity why would you think that a 120 stem is the correct length? I'm asking, not out of judgement but out of a genuine curiosity to better understand the question.

I generally think of the stem length as a percentage of the top tube. It should be proportionate to the TT length. a 120 stem on a small top tube puts a lot of weight on the front end. a 120 stem on a 61cm top tube is pretty reasonable.

I don't have an answer for you, I just want to squash internet rumors about how to fit a bike.

[Dave]

If you change a 90mm stem to a 120mm, it will have almost no effect on the amount of weight on the front wheel. Only the rider's arms would move a little further forward.

If you have a frame with a 30mm shorter reach, then that's another story. The front-center should be a lot shorter and that will increase the weight on the front wheel.

[HugoBear]

Great point about the shoe overlap. I hadn't considered that.

[HugoBear]

"A 120 stem is an optimal length" is an incorrect statement. The correct way is "A 120 stem is an optimal length for some people." Out of curiosity why would you think that a 120 stem is the correct length? I'm asking, not out of judgement but out of a genuine curiosity to better understand the question.

I generally think of the stem length as a percentage of the top tube. It should be proportionate to the TT length. a 120 stem on a small top tube puts a lot of weight on the front end. a 120 stem on a 61cm top tube is pretty reasonable.

I don't have an answer for you, I just want to squash internet rumors about how to fit a bike.

I think you are right. I am clueless about this and was just going by some comments I have read. When I did go to a fitter with the strong, that specific fitter said the 535tt coupled with the 100mm stem was in his words, perfect. Maybe for me, but clearly not for some others.

[ergott]

This

"Frame Fit

A properly fitted bicycle is centered on the stem, which we think of in terms of sizes: small (90-100mm, for frames in the 50-54cm range), medium (110-120mm, for 54.5-57cm range), and large (120-130mm, for 57.5cm and up range). A bicycle built around the proper stem length – giving correct reach – will have optimal weight distribution and handling characteristics. We believe that the cure for a poorly fitting bicycle is not a longer/shorter stem but rather a well-built frame using the correct length stem. Your saddle height and the drop to your handlebars are always taken into consideration when suggesting seat tube and head tube length. We use BikeCAD as a drawing tool and we are not shy about making fit and size recommendations. Our custom frames are built using the following guidelines:"

http://www.hampsten.com/company/designmaterials


Even that is just a guideline.

[carpediemracing]

It's true that a 120mm stem with no other changes doesn't really do anything except stretch your arms out more.

It's when the top tube changes that it becomes significant. I never pointed this out and it's significant that I didn't. With that shorter top tube you'll need a longer stem to get the same reach. That's the right way to increase stem length, keep the reach correct while changing the frame's contribution to reach.

Remember that seat tube angle also affects reach. For example the Lemond frames had super long top tubes. I contemplated getting one until I realized the seat tube angles were super shallow, like 72.5 for my frame, something like that. The frames were fit for a long femur rider like Lemond. Since I'm the absolute opposite of him his frames wouldn't help me. If he had the same top tube on a 75 deg ST angle bike that would have been a totally different story.

For the record I ran a 140-145mm stem (quill so they were sort of random in terms of actual length) with a 525 mm top tube and I think a 74-ish degree seat tube angle (Cannondale 50 cm frames, various vintages, then a Specialized). I had shoe overlap and the reach was too short. The head tube angles were shallow to try and help avoid shoe overlap. Lots of compromises.

Now I run a 565mm top tube (effective), 75.5 deg seat tube, and a 140mm stem with a compact bar, 120mm stem with a regular reach bar (and in the process of getting rid of the latter). I don't have shoe overlap at all even though I'm running a steeper head tube angle (73 deg, which I feel is optimal with a 43mm rake fork).

My bikes are so long and so forward-oriented that I needed to tighten up the rear. Just coasting in really fast turns I'd skitter my rear wheel across the pavement, forget about pedaling. With a 390mm chainstay that's not a problem anymore.

[ergott]

Also, bar reach will impact hand position just as much. You can change the reach of a bike as much as 2-3cm with just the bars. It's all about putting the hands in the right place on a bike that is the correct size.

[HugoBear]

This

"Frame Fit

A properly fitted bicycle is centered on the stem, which we think of in terms of sizes: small (90-100mm, for frames in the 50-54cm range), medium (110-120mm, for 54.5-57cm range), and large (120-130mm, for 57.5cm and up range). A bicycle built around the proper stem length – giving correct reach – will have optimal weight distribution and handling characteristics. We believe that the cure for a poorly fitting bicycle is not a longer/shorter stem but rather a well-built frame using the correct length stem. Your saddle height and the drop to your handlebars are always taken into consideration when suggesting seat tube and head tube length. We use BikeCAD as a drawing tool and we are not shy about making fit and size recommendations. Our custom frames are built using the following guidelines:"

http://www.hampsten.com/company/designmaterials


Even that is just a guideline.

Interesting, according to this, since I ride a short top tube bike, the size range they pair it with is 90-100 mm. So seems like the "optimal" 110-120mm stem is consistent with the very common 56cm Tt bike. Thanks
Also, as many have noted, bars make a difference. I still am in search of a set of bars I really love. All the ones I have are just ok

[Dave]

Advising the stem length to be shorter for smaller frames is not always valid.

My 51cm LOOK 585 frames work great with a 110mm stem and short reach bars. I've got long legs and a short torso - 83cm cycling inseam, 169cm height. If I was several inches taller, with the same leg length, I could ride the same frame with either standard reach bars (around 85mm) and the same stem length, or a 120mm with the same short reach bars.

What brand of brake/shift levers you choose also makes a difference. Shimano has the longest reach and Campy the shortest. I use Campy, otherwise, I'd need a shorter stem.

[oldpotatoe]

I have 3 road bikes. One is a cervelo R3, size 54, with a 545 Tt. I run a 100mm stem. One is a strong ti, with a 535tt and 100mm stem, which a fitter said is perfect. The other is a 53cm Pegoretti duende with a 543tt and I run a 100 mm stem. I keep reading on the forum running around a 120 mm stem is optimal. There is a 52x52 Bedford on the forum, which I think would mean I could run a 110 to 120 stem. Would that potentially be a better fit than the bikes above? I feel a little stretched on those bikes but not really uncomfortable. Also, would anyone sell one of the three bikes and buy the Bedford?

Is your saddle in the correct place? kops is a small 'c' constant but pretty much where ya start with fit.
DO NOT swap a bike because somebody said a 120mm stem was 'optimal', that's bugle oil.

Fit person know what they are doing? If Yes, Listen to them, not anybody on a forum who doesn't see you on a bike, in person, whilst doing a fit.

[RedRider]

Fit person know what they are doing? If Yes, Listen to them, not anybody on a forum who doesn't see you on a bike, in person, whilst doing a fit.[/QUOTE]

Would you go to an online medical forum for a diagnosis and then operate on yourself? Find a professional fitter and get it done right.

[ergott]

One of my road bikes is a 53cm TT and I have a 12cm stem so like I said it's a guideline not a rule.

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