Weight distribution on bike (front and back) -- undated with road bike info

Triathlon Forum
1

I know I’ve seen the numbers somewhere, but I looked through all the fit and geometry experiment articles and can’t find it, other than references to balance.

What percentage of the weight of the bike/rider should be on the front and rear wheels, respectively?

Here’s why I’m asking: I did the weighing of my bike, front and rear wheels, with me on it in position, and came up with 56% on the front wheel. I knew I was over the front wheel, and this just confirms it. I thought I saw some references to 40% front/60% rear, but when I throw that into some calculations, with my positioning (Cg 16.4 cm foward of the BB/nose of the saddle), I end up with (on 650s): 37 cm chainstays, 71.2 cm front center (!!!), and a wheelbase of 107.6 cm (I’m just under 5’10"). So I’m wondering if I’m just thinking wrong. Raising the weight percent on the front wheel does lower the front center some, but what is a good number to shoot for?

2

53/47.

3

53% on the front or rear? Thinking it’s rear, just want to verify.

4

Unless i’m seeing things Tom is saying 53 front/ 47 rear…you could probably get those # by moving back a m/m of so…

5

There’s not a right/wrong answer. On road bikes, you’ll have more weight on the rear wheel; on TT bikes, more on the front. If you can handle the bike, don’t worry about it.

IIRC – I’ve got 55% or so on the front wheel. My rule of thumb is that I have to be able to ride the bike no-hands. Too much on the front, and I can’t. I can ride my bike no-hands very easily and steadily.

6

That’s a good criteria, and honestly one that I can only truly say was true of one bike I’ve owned – an old Schwinn Cimmaron that I had modified with slicks, drop bars and road brake levers for commuting. I wonder what the geometry of that bike was…

7

Tom’s got a BMW and a tri bike confused…

8

Okay, with the 53/47, the “it doesn’t really matter”, and now “confused with a BMW” talk…

Here’s another posit: Is the thinking that there is going to be more weight on the front wheel generated from the fact that we’re all either riding converted road bikes, or bikes that aren’t quite “there” yet, or is it actually an ideal set-up? The reason I ask this is that, in reading Dan’s “Geometry Experiment” article, he’s changing the bike pretty radically to get less weight on the front wheel (or more for comfort, with the result of less weight on the front wheel), and the results sound, at least to me, pretty ideal.

9

I know I’ve seen the numbers somewhere, but I looked through all the fit and geometry experiment articles and can’t find it, other than references to balance.

What percentage of the weight of the bike/rider should be on the front and rear wheels, respectively?

Here’s why I’m asking: I did the weighing of my bike, front and rear wheels, with me on it in position, and came up with 56% on the front wheel. I knew I was over the front wheel, and this just confirms it. I thought I saw some references to 40% front/60% rear, but when I throw that into some calculations, with my positioning (Cg 16.4 cm foward of the BB/nose of the saddle), I end up with (on 650s): 37 cm chainstays, 71.2 cm front center (!!!), and a wheelbase of 107.6 cm (I’m just under 5’10"). So I’m wondering if I’m just thinking wrong. Raising the weight percent on the front wheel does lower the front center some, but what is a good number to shoot for?

http://forum.slowtwitch.com/gforum.cgi?post=152349;search_string=weight%20distribution;#152349

10

Damn! Good detective work! Yeah, yeah, I know… “Search on ‘weight distribution’…”

Thanks. That’s EXACTLY what I was looking for.

11

Damn! Good detective work! Yeah, yeah, I know… “Search on ‘weight distribution’…”

Thanks. That’s EXACTLY what I was looking for.
:wink:

12

47/53, as tom says, is about as good as you can get on a tri bike. this, because of the steeper seat angle and the fact that you’re laying your torso on the front of your bike.

60/40 on a road bike is great in theory, but you can’t get this if your hands are on the drops and you’re riding on the rivet. 60/40 becomes 55/45 becomes 52/48, and so forth, depending on where you sit.

put your rear wheel in your trainer, the front wheel on a scale, level the bike, and move around on the saddle and the handlebars. you’ll see how weight distribution changes.

personally, i don’t think tri bike handling is a big problem when you’re in the aero position. it’s when you’re out of it that the problems can occur. i think ashburn’s right, if you can ride no hands you’re in pretty good shape.

at the same, time (and i have no good math for this) i think the problem isn’t simply weight distribution over the wheels per se, but how much weight sits in front of the steering axis. when you’ve got a big aero bar out there, and your hands are out there, and if the stem is long, and the distance between the stem clamp and the hand-hold position on the pursuits is long, then you have a lot of what gerard calls “tiller” and you also have a lot of weight on that tiller.

the steeper your seat angle, the more weight is on that tiller. if your pursuit bars are angled down, you have even more weight on the tiller. while descending, even more weight. while braking, even more weight. and so forth.

again, i’ve got no good math on this, but i think the pressure on a system to oscillate increases, and the ability of a system to resist an oscillation once started decreases, as more and more force is applied to the steering axis (and more leverage increases that force). accordingly, if your wheel isn’t exactly true or the rim is the least bit wavy in its construction, you get speed wobble when you brake. or you just get wobble at a certain speed, braking or not.

of course, speed wobble is an issue unto itself and one can spend a lot of time on this (without ever coming to a concrete set of answers) but i think BOTH weight distribution AND the force applied to the “lever” attached to the steer column contributes.

one last thing. i mentioned that this is more a problem when NOT in the aero position. when you ARE in the aero position your weight is resting on a place much closer to the steering axis (almost right on top of it). when your hands are on your pursuits, next to your brakes, this dynamic changes for the worse. i’m not saying you shouldn’t be on the pursuits when in dicey situations, i’m just saying that problems often tend to manifest themselves on tri bikes with hands on the pursuits, while descending, while braking, and this is the triple whammy that places a ton of weight forward of the steering axis.

13

I guess it is too obvious to just suggest when decending on a tri bike we should slide back on the saddle as much as possible then right?

14

“when decending on a tri bike we should slide back on the saddle as much as possible”

of course. but there are practical limits to this, and when braking the weight just comes right back forward.

15

if you can ride no hands you’re in pretty good shape.

That has always been a test of mine. All to many buddies cant go no handed on their Tri bike for even a second - where as I can take off my coat, sit up and eat, move around and be stable. Oddly enough I also decend MUCH faster than the same guys who cant go no handed.

16

Okay, I wanted to update this thread with some info on the weight distribution of my road bike and position, just for sh!ts and grins.

Turns out that I’m riding my road position pretty steep too – according to Dan’s angle finder chart, I’m at 77 degrees! I do find this position very comfortable, even with a road set-up in front, and have no problems using the drops, but I’ve for years needed crit bend or 8-bend road bars. Now the interesting part is that the weight distribution on this bike, which is only .1 inch shorter in wheelbase and .05 shorter in front center, is 43% on the front wheel and 57% on the rear. And the bike handles VERY well.

Just some interesting, though probably ultimately useless, data.

17

“according to Dan’s angle finder chart, I’m at 77 degrees”

keep in mind that this is running through a point midway fore/aft on the saddle. in reality, if you’re riding a zero-offset seat post, the probably corresponds to a bike with a seat angle of 75°, or even 74.5°. this is easy to see. look at the fore/aft difference between the center of the saddle’s upper and the center of the saddle’s rails. they’re offline by about 3cm. this is probably 2°.

then, of course, there’s where you sit on the saddle which, for me, is aft on my road bike and noseward on my tri bike.

but my point is that you ought to filter “my” seat angle calc against this reality. i tri-bike ride at 81.5° of seat angle, measuring through a point midway fore/aft on the saddle. this is best accomplished on a bike that is actually built at perhaps 79° of seat angle.

18

Good input. I simply used the nose offset and Center-to-14cm behind nose dimension to get the angles. The saddles are virtually identical between the two bikes (both Bontragers with the cut-away “wings”). These are both on Softrides, too. But the difference of how I sit on the two bikes probably makes as much as 2-3°. I was just shocked that I was (apparently) riding that steep on my road set-up, and might have been a clue as to why I was trying to go SO steep on the tri set-up. I still need to get some pics taken of me on the bike to get my body angles while riding.