Oostal

I'm curious as to what would be the effect of longer stem and shorter top tube on bike cornering or descending. I ride a frame that has 57 cm seat and top tubes (both centre to centre). To avoid the elbows from locking I had to swap the original stem to 9 cm one. I am 5'11 (181 cm) tall and have inseam about 33' (84 cm). If I stand next to my bike and put my elbow against the tip of the saddle, stretch the fingers out, then my middle finger reaches the middle of the stem (if this test indicates anything). The bike is a mid-90s high end steel frame with a classic geometry. I have the feeling that the bike is rather unresponsive in corners. It feels like driving with a large limo to the corner. In our group I always loose a lot of ground in the corners, whereas otherwise I am fairly strong. I'm sure that 90% it has to do with my skills, but I'm still wondering about the effect of the frame. How would the handling be affected by going for a 56 frame and 10 cm stem or even 54 frame and 12 cm stem. I have noticed a lot of riders of my height on smaller frames.

grolby

The only meaningful impact on handling from changing frame size or stem length is weight distribution. Having a weight distribution that is closer to equal between front and rear will help the bike feel more planted in high-speed turns than having most of the weight on the back wheel. But you generally need to start out with the right fit to begin with - slapping a longer stem on a bike isn't necessarily going to make the bike feel better. A 90 mm stem, despite some claims by the ignorant, is a perfectly normal length and certainly won't cause handling problems. And there are way too many other variables to ascribe handling issues to frame size or stem length first. Weight distribution matters, but the front end geometry is far more important. And your elbow test means absolutely nothing. I would suggest test riding a few different bikes, if you can at least go around a couple of fast corners with them, and see if they feel any better than your current bike. If so, consider replacing your old bike. Life is too short to ride a bike with crappy handling.

StanSeven

Here is a source of good info not only on stem length, but how all the pieces are related

https://www.cyclingtips.com.au/2011/0...bike-handling/

A shoter stem makes handling quicker. This article mentions a longer stem adds to stability, which is another way of saying it deosn't feel responsive in turns. Regradless if you change, you quickly adapt and won't notice the difference after a few rides with that small of stem adjustment.

You might want to have a professional fitter take a look at your setup. I'm about your dimensions and was fitted for a custom bike. It turned out with a 56cm seatube (c-c) and a 57.2cm toptube. I use a 110 stem on it. My favorite bike is a 56 (with 56 tt also) and a 120 stem.

I'm wondering if you aren't stretched out enough. What angle stem are you using?

grolby

I really have to disagree. Stem length certainly effects the steering feel, but this is a matter of adaptation. It does NOT effect the actual steering response of the bicycle. That's all about the front end geometry. A long stem isn't going to make a bike feel non-responsive in turns. It means somewhat more movement of the bars is required for a given amount of rotation of the steerer, but this does not effect stability. It does slightly reduce the effect of inadvertent steering inputs, but again, the different between (say) a 90 mm and a 120 mm stem is sufficiently small that a rider can easily adapt to this difference. A longer or shorter stem isn't going to make the bike more responsive in corners.

Keep in mind, by the way, that 110 and 120 mm is very long for a stem. Roadies who are accustomed to aggressive aerodynamic fits are used to thinking of that length of stem as normal, but 90-100mm is much more typical, and any road bike will handle perfectly normally with stems of that length.

This doesn't make much sense, given what you're already saying about stem length. The OP is saying that the bike doesn't feel like it wants to turn; above, you argue that a longer stem = more stability, which you believe is equivalent to the bike being less responsive in turns (it's not, necessarily, but never mind). But now you're suggesting that the OP is too stretched out. Huh?

The best way to get a better sense of how your bike handles and whether it's good or not is to ride more bikes. You will immediately recognize the difference between a bike that handles in a way that you like and your own. And eventually you can make a connection between a bicycle's geometry and fit and how the handling feels. But this can only come with experience on other bikes.

EDIT: Having read through that article, it's not a remotely trustworthy source of information on bicycle geometry and handling; the author doesn't know what he's talking about. 70mm of trail isn't considered low - it's VERY high. And the claim that track bikes have slow steering to compensate for a high bottom bracket is laughably wrong. I wouldn't believe a word of that article.

merlinextraligh

OP, learn to corner. Read up on counter steering.

Davis Phinney wrote some good pieces on cornering if you can still find them. Asthe winningest American crit racer ever, he knows how to get around a corner.

Also watch how the fast people in your group go through a corner.

Lastly, quit questioning your equipment; that's only holding back the confidence you kneed to develop.

carpediemracing 

I think that a slightly longer stem is beneficial to cornering. The reason isn't "handling" per se but weight distribution. Specifically, with identical positions between two bikes, one using a longer stem (and shorter top tube) and the other using a shorter stem (and longer top tube), the top of the steerer tube will be closer in with the first bike (shorter top tube). This means the front wheel is closer in towards the rider. More weight on the wheel (since most of it is on the rear wheel anyway) helps cornering.

This is assuming both bikes have otherwise identical geometry (seat tube angle, etc).

Consider an extreme example:
1. 57 top tube + 9 cm stem (from OP), giving you 66 cm total distance.
2. 116 top tube + a rear ward facing stem that is 50 cm long, giving you 66 cm total distance. Look at the dernys in the following picture (link: https://www.bobkestrut.com/images/2005dortmund.jpg)

In the first bike the front wheel would be somewhere familiar, like a normal bike.

In the second, the front wheel is really far out there. Virtually all the weight of the rider will be on the back wheel.

Although not actual bikes we race, the illustration shows that, yes, if you have two set ups with the same reach and one has a shorter stem, you will have less weight on the front wheel.

If you have less weight on the front wheel, you can't corner as well. Everyone tries to get their front wheel secure/stable - it's why a lot of new riders don't use their front brake enough, it's why I slide forward on the saddle when making really fast hard turns.

Having said that, for the OP - you shouldn't just compare top tube lengths or frame sizes. You should consider head tube length as well. It may be that you need a frame that isn't necessarily sold off-the-shelf. Take me for an example - I'm 5'7" and have a very long torso. My combined top tube and stem length is longer than your set up (56.5 cm top tube, 12 cm stem, and that's with a full reach bar - with an FSA Compact a 13 cm stem was still way too short). However my seat tube is around 40 cm (compact style - equal to a size S Giant or a 50 cm standard frame).

I still slide forward on that bike, to get more weight on the front wheel. The rear wheel is much more tucked in as I have 39 cm chainstays (vs 40.5 cm for normal). The bike feels rock solid in turns.

There are other factors. Seat tube angle (and the actual factor, saddle set back) really affects effective top tube length and therefore, indirectly affects weight distribution. If you have a very shallow seat tube angle, it puts a lot more weight on the rear wheel. It also effectively increases your top tube length requirements. My frame has a 75.5 deg seat tube angle, much steeper than my old frames. At the saddle it's worth about 1-2 cm of setback (I forget how much) so I subtracted that amount from my top tube length requirement, dropping it down significantly. I wanted about 6 cm more reach but only got a 3 cm longer top tube.

Oostal

Thanks a lot guys! What a great advice! As some suggested, I think it has something to do with weight distribution that in my case could be a bit too much towards the back. Another indication could be that when riding hands-free it seems to be difficult to control the bike. I never had this problem with my previous bike. Unfortunately I do not know the size or geometry of that one as I left it behind when moving from one country to the other.

ps. I absolutely agree that I should improve my skill level. I'm working hard on it every week and see improvements. Yet, if there is something in the bike that I could change to improve handling, then I see no reason not to do it.

hyhuu

This doesn't sound right. It should be the other way around.

One of my bikes is a bit large for my height and during the high speed cornering, if I don't lean forward to weight the handle bar, the front of the bike would float instead of plant as CPD and grolby had succintly explained.

Tuc

The largest part of the effort in sharp cornering comes from the rear, you want the weight and the force of the "wheel gyroscope" being overcome from the rear. High speed but larger radius turns not so much, more balanced F&R, IMHO.

Oostal

hm, this got me thinking now. I did the competitive cyclist fit calculation. Quite a lot to measure there...

My results:
Seat tube ~56 (center to center) or ~57 (c to top)
Top tube 54-55 (center to center)
Stem 11-12

Did not think I have so short hands

ultraman6970

First thing, I believe you are asking the wrong question, is not the same that you are handling the bike pretty bad because the fit is wrong. Than have a bike that handles like cr@p.

Handling in bike has nothing to do with the stem and top tube, the handling in a bike is related to the bike geometry and more precise to the head tube angles and the rake in the fork. Just in case im making this as simple as possible for the op ok?

If you have the wrong stem the bike will handle wrong, but w/o knowing the bike you have is hard to know so a picture could help a lot.

For the record if the inseam you have is right, then your saddle height should be around 73 centimeters if you are way off that then you have a problem. Wont go in details on how to measure that ok? I'm assuming you know.

As for the fit from CC, for many people that thing is always off a few cms for some reason and looks like in your case as usual gave you the wrong top tube The funny thing is that the frame size shown to you is basically a custom made one when probably a 56 center to top x 56 center to center should fit you just fine. The 57 you have right now is not that off either IMO but it depends of the bike because if we are talking about a Ridley damocles in 57 then is way too big... if we are talking about a regular steel road frame then is kind'a ok. Since you have not mentioned the bike you have is hard to know. A picture could help. As for the stem... at your height pretty much everybody goes with 11 and 12, there is no tables or rules for stems because if you have a guy with back problem sure he will go with a shorter one, a more flexible guy with long arms will go with 13 for example. So it depends, but so far 9 cm is way too short for you based in the norms and your height. Since you complain about your handling, then is clearly too short.

Post a picture of your bike and yourself at least seated in the bike will help more.

Hope this helps you.

ilovecycling

IMO, a bike is too big when you have to go < 10cm on the stem to make the reach comfortable. I'm 5' 11" as well with a 33.75" real inseam. I ride a 55cm/Large Look 595 with a 56cm effective (horizontal) top tube length. It feels great with a 100mm stem, but I can also get away with a 110mm stem on it. I can also ride a 54cm with a 110-120mm stem. It just sounds to me like your bike is too big for you, especially if you feel that it handles like an old cadillac in the turns.

AEO

handling is related to weight distribution + caster angle.

stem length only changes steering sensitivity in a very limited scope. If you switch from a 100mm stem to 80mm stem on 42cm bars, then your total leverage will only change by 8mm. a^2 + b^2 = c^2