Road Bike, Cycling Forums banner
1 - 12 of 12 Posts

·
Registered
Joined
·
66 Posts
Discussion Starter · #1 ·
Sometimes regardless if it's a smaller frame. Or no core strength. Spacers and stack hight under the stem is needed to provide an efficient and comfortable ride.

With that said. Some frames out there are great great deals. But can be a size to big or to small. Usually isn't a problem as long as the fit matches.

But if one gets a smaller frame. And needs to raise the height on the steertube to have a good reach. Is there a certain point where the height of the steer tube effects more then just fit? And can start to dictate how the bike drives?

Thanks
 

·
Big is relative
Joined
·
11,887 Posts
Sometimes regardless if it's a smaller frame. Or no core strength. Spacers and stack hight under the stem is needed to provide an efficient and comfortable ride.

With that said. Some frames out there are great great deals. But can be a size to big or to small. Usually isn't a problem as long as the fit matches.

But if one gets a smaller frame. And needs to raise the height on the steertube to have a good reach. Is there a certain point where the height of the steer tube effects more then just fit? And can start to dictate how the bike drives?

Thanks
It's not a great deal if it doesn't fit you. If you need a ton of spacers under the stem to make it fit, pass on it.

If the fork is carbon, there are some rules of thumb, one I heard was two times steerer diameter in spacers. You're probably using a longer stem as well which creates a potentially dangerous condition where you could snap the steerer. Using a bunch of spacers won't affect the handling of the bike but if you're doing it to make a small bike fit you, you need to consider things like exposed seatpost and toe overlap on the front wheel. Get a bike that fits you.
 

·
Registered
Joined
·
6,832 Posts
Good question. Spacers don't change trail nor wheelbase, so therefore by themselves, they shouldn't affect bike handling. However, bike handling is not just about the bike riding by itself without a rider. Handling will involve a rider. So now with a rider, a high spacer stack might change the center of gravity of bike plus rider because a higher stack might not allow the rider to get lower. Also with a higher stack of spacers, I think the handlebar will feel a tad more flexy.

A 3 cm raise is within acceptable range. Beyond that, then I think it may negatively affect handling, especially in aggressive situations.
 

·
Registered
Joined
·
8,224 Posts
3-4cm of stack height is going to be insignificant in how the bike handles.

Especially for new riders having the bars up a bit may help until they develop more flexibility. In that case it is better to have a few spacers beneath that can be removed as flexibility improves.

Any added flexing in the steerer will be minimal as the steerer is larger in diameter, thicker in section and has a much shorter unsupported length than say a handlebar.
 

·
Crank Addict
Joined
·
1,943 Posts
When I first built my Venge, I had 25mm of spacers plus the 15mm aero upper bearing cover. I've gradually lowered the stem and have not got it all the way down with just he 15mm aero upper bearing cover and cut steerer tube. I've notice notice a difference in handling, but I have noticed a difference in stiffness in the front end.
 

·
Registered
Joined
·
9,657 Posts
Good question. Spacers don't change trail nor wheelbase, so therefore by themselves, they shouldn't affect bike handling. However, bike handling is not just about the bike riding by itself without a rider. Handling will involve a rider. So now with a rider, a high spacer stack might change the center of gravity of bike plus rider because a higher stack might not allow the rider to get lower.
That's pretty much it. And bike design comes into play.

It's about weight distribution and what weight distribution a bike was designed for. In a vacuum spacers have nothing to do with anything. But if you have a ton of spacers it's probably a good indication that your weight distribution will be outside of the parameters of where a bike is designed to handle well.

Let's look at two hypothetical bikes. One with a 20CM headtube and one with a 10CM headtube. You set them up identical by slamming the stem on the 20CM headtube bike and by adding 10cm of spacers to the other.
They'd be the same fit and have the same length steer tube, just that with one the steer tube is exposed and the other it's under the headtube. It's very unlikely the one with 10cm spacers will handle well though despite having the same steer tube length as the slammed one despite having the same steer tube length. That's because the bike with the 10cm head tube was designed to have more weight over the front (more aggressive) than the one made with a 20cm headtube. It's not because the steer tube is exposed and covered with spacers vs being under a head tube.
 

·
Registered
Joined
·
66 Posts
Discussion Starter · #7 ·
In response to having to use an extended stem.

We are talking about 54cm - 56cm - 58cm difference.

My size is 56cm, riding a square 56cm bike right now with a 56cm top tube. Sometimes I find myself extending my fingers, knuckles and palms to take stress off my back and such. My height is 5'10.5" so it is a bike in my size. Although I have not taken time to gather demensions of my entire skeletal frame.

There are about 3-4 spacers on it right now too. I cannot gather the sizes of these spacers right now (away from bike).

I'm talking about going down to a 54cm cannondale which already have a reputation for riders needing to go a size lower then their suggested ride hight.

Between stem angle and needing spacers. I cannot imagine the bike needing so many spacers that it may take the bike out of its designed riding porportions. Although I understand I could be wrong. After all. I am here seeking guidance on the subject...
 

·
Registered
Joined
·
5,347 Posts
Bike sizes are much less consistent than shoe sizes. I have 59cm, 58cm and 56cm frames that put me in very close to the same position. Some have taller head tubes than others- my race bike's got the stem flipped up because it's got a really short head tube (and I have long legs for my height). On the others the stem is down.

Frame angles, especially seat tube angle, change the reach. ETT does not take the frame angles into account.

Your having to ride on the tips of your fingers could be because the reach is too long, which could be too long a stem or the seat too far back or both. Or your hamstrings are tight. Or your core is weak. Or all of those. Fixing the latter two take some time during which you might want a shorter stem or higher bars or both.

You might want to get a professional fit.


In Jay's example the bike with 10cm of spacers will handle the same as the bike with a 10cm longer head tube (assuming the frame geometry is the same). But the bars will be flexy due to the smaller diameter of the steerer vs the head tube. And the bike will spontaneously burst into flame from exceeding the manufacturer's spacer recommendation.
 

·
Registered
Joined
·
66 Posts
Discussion Starter · #9 ·
Right on. Thank you.

My hamstrings are tight. My core although may not be weak; is probably not in optimal condition to seriously train road biking as a skill.

I'm not to sure on the seat angle. I can't find geometry specs on the bike so I'd have to figure out how to measure it myself.

The Stem is only 110mm so that could be making a reach for me.

I'll consider a much shorter stem and more propped up position.

All this will help with my current frame. The 54cm won't have me stretched out as far. Will that also theoretically mean that I may need less spacers as well?
 

·
Registered
Joined
·
66 Posts
Discussion Starter · #10 ·
Oh also. Are there any signs that I may have a short torso with long legs? Argh. I shouldn't say that until I actually get my inseam and upper body measurements.
 

·
Registered
Joined
·
5,347 Posts
With a smaller frame the reach will be shorter but the head tube will also be shorter. To get the bars in the same position you'll need to raise them with more spacers.

You need measurements and some comparison to see what your relative body porportions are.

I should have said that modern fitting goes by stack and reach. They are independent of frame angles making it easy to compare different frames. I've been riding a long time and still think in ETT. I should switch to stack and reach now that most frame makes publish those.

You would be well served to get a professional fit.
 

·
Registered
Joined
·
8,224 Posts
Oh also. Are there any signs that I may have a short torso with long legs? Argh. I shouldn't say that until I actually get my inseam and upper body measurements.
Before you go doing to much to change your bike, take a look at this. Have someone help you with measurements. See what the calculator then says.

Nothing is a substitute for a bike fitting, but this should get you closer than your trial and error.

Pedal Force super-light carbon bicycle
 
1 - 12 of 12 Posts
Top