Road Cycling - Will the improvement be noticeable?

This is one of those questions I usually cringe at, because basically "it depends" on factors I can't quantify.

So here goes:

I have a loaded touring bike. I don't usually go too fast on it (cruising at less than 15mph), but sometimes I'd like to go a little faster. Acceleration is poor. I think some of that sluggishness is due to the weight of the wheels.

Anyway, I'm thinking of buying some lighter wheels for some of my unloaded weekend rides. I want something practical, that can take some bumps and not be too harsh to ride.

Here are the weights of the main components (hubs will be the same)

==========loaded Touring ========= New setup
Rims ========565gms===============470
Tires ========550==================320
Spokes ======240 (36)===============213 (32 - 14g)

Total =======1355 ==================1003

So each wheel on the new setup would be 352 grams lighter. In addition, I would use a tighter cassette on the new rear wheel (11x23 vs 11x32) and save another ~95 grams.

I know there are lighter options, but just considering the examples listed above, will the new setup be noticeably faster and easier to accelerate when cruising in the 15-20mph range?

Other factors that will influence the potential speed include tread (touring tires have a more rugged tread, lighter tires are smooth), inflation (80psi vs 100+psi) and the tighter cassette will allow for a better selection of gears versus the large 3 tooth jumps on the touring cassette. Everything else (equipment, riding position, terrain) will be the same.

The answer seems obvious (yes, the lighter wheels will be noticeably better), but I'm not sharp enough to know if this translates into 1mph or 3mph or ? for my cruising speeds on the flat. I'd guess it would be vastly better on the hills.

Thanks.

I can tell you that I will not be able to feel a 350 gram difference. My bike weighs only 18lb, but I weigh 215.. So 350 gram is half my daily weight fluctuation.
If you are not a top shape rider that has maximized his/her body ability to improve, it will be hard to notice a 350 gram change..

things that will help you speed up: slick, thiner tires (23c), higher inflation (120psi +), and lots and lots of training.. I improved my average speed by getting low rolling resistance tires (Conti Grand Prix Supersonic) which go up to 145psi. and I could feel a significant difference in my speed...

I can tell you that I will not be able to feel a 350 gram difference.

I have to disagree..

I recently had 200g savings on my front wheel. My front wheel used to weigh about 800+ grams, now its down to 600g.

My average increased by 4kmh on my last 80km ride. (prev ave: 30kmh~31kmh, curr. ave: 34kmh)
I can accelerate faster too.

I'm also planning to get those hutchinson tires w/c weigh 200g each. My current tires weigh 380g each. The 180g diff. would be good.

The total savings of ~1.5 pounds should definitely be noticeable. Especially in quick accelerations and climbing. For the flats, I wouldn't expect any significant gains since the amount of accelerating is somewhat limited. Aerodynamics play a greater role in flat courses.

I can tell you that I will not be able to feel a 350 gram difference. My bike weighs only 18lb, but I weigh 215.. So 350 gram is half my daily weight fluctuation.



First of all, that's 350 grams for the front wheel, and abouy 450 for the back.

Second, my concern is with the loss of rotational mass, not the overall weight of the bike. That's 800 grams of weight in the wheels that I no longer have to accelerate.

But, as someone else pointed out, it probably won't mean much on the flats.

This is one of the most discussed and argued concepts in biking, filled with urban myths.

For a couple of resources, see:

http://www.analyticcycling.com/WheelsConcept_Disc.html

According to Jobst Brandt, author of "The Bicycle Wheel"


Forget about the rotating weight, whether rotating or not it is just
>plain weight. This rotation stuff is another part of the myth and
>lore of bicycling.
>
>Jobst Brandt <jbrandt@hpl.hp.com>

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=ISO-8859-1&threadm=372a1da4%40news3.enter.net&rnum=4&prev=/groups%3Fq%3Drotational%2Bbrandt%2Bmass%2Bfaster%2Bgroup:rec.bicycles.tech%26hl%3Den%26lr%3D%26ie%3D UTF-8%26oe%3DISO-8859-1%26group%3Drec.bicycles.tech%26selm%3D372a1da4%2540news3.enter.net%26rnum%3D4

This is one of the most discussed and argued concepts in biking, filled with urban myths.


Denver,

Thanks for actually reading my post and having a relavent response.

It appears that changing the wheels would have a small effect, but not due to the reduced weight.
I'm not racing, so it's not worth the expense.

Saving some weight will be noticeable, but only when doing quick acceleration... which is why it is noticed a lot.

However, in terms of maximum cruising speed on smooth roads, high pressure narrow tires are the only items that would make a significant difference.
So tour with 700x32, or maybe with 700x35-37 rear and 700x30-32 front, and do sporty rides with 700x28 or even 700x25 if you have smooth roads.

Personnally, we have so many potholes in Montréal that I don't see the use for lightweight wheels.

----<snip>----
Personnally, we have so many potholes in Montréal that I don't see the use for lightweight wheels.


Potholes in Montreal? NEVER! :)

I know what you mean.. I lived there for 10 years, and I remember when spring comes, the flowers and the potholes come into bloom..

Lighter wheels will help with acceleration as everyone has noted and as you have concluded, does not effect overall speed. But I will say that the quicker handling is worth alot. A lightweight, quick handling bike that is stable is pure joy to ride.

Lighter wheels will help with acceleration as everyone has noted and as you have concluded, does not effect overall speed. But I will say that the quicker handling is worth alot. A lightweight, quick handling bike that is stable is pure joy to ride.

It also seems that lighter wheels will help a lot on climbs, if I understood the data from the Analytic Cycling website correctly.

But the cost of adding lighter, conventially-spoked wheels to my trekking-style touring bike is not proportional to the benefits. If I want to go faster, I should get a lightweight road bike with lighter AND more aerodynamic wheels. New wheels and tires (as I specified above) would cost over $250 and yield little. A bike in the $1000+ range would be about 10 lbs lighter (lighter wheels, lighter frame, no rack, no fenders, etc. etc.) and have more aero wheels. And be more enjoyable for faster riding (subjective.)

For example, the Trek 1500 has 20/24 spoke wheels and runs about $1100.

Maybe next year.

This is one of the most discussed and argued concepts in biking, filled with urban myths.

For a couple of resources, see:

According to Jobst Brandt, author of "The Bicycle Wheel"
Quote:Forget about the rotating weight, whether rotating or not it is just
>plain weight. This rotation stuff is another part of the myth and
>lore of bicycling.
>
>Jobst Brandt <jbrandt@hpl.hp.com>


Perhaps some context needs to be supplied with this quote. As stated without any qualifications, his statement is flat out wrong! and perhaps "urban myth" material...

If he qualified his statement that while a bicycle is traveling at a constant velocity then his statement would be true, However, when accelerating there is a difference. Given two bikes with the EXACT same overall weight, there can be differences in the amount of force needed to accelerate the two bikes to a certain speed. The differnce comes down to the rotational moment of inertia of all rotating parts (wheels being the most significant)

This is basic physics. For pure translational movement, F=ma applies. Take two 20 lb bikes, lock all rotating parts, slap some identical rocket thrusters on them and fire them off skidding across a frozen lake bed. The will accelerate at exactly the same speed, even if bike 1 has 3lb wheels and 14lbs for everything else, and bike 2 has 5lb wheels and 10lbs for everthing else.

For rotational acceleration, spinning a wheel up to speed, The equation for motion is T = omega * alpha where T = Torque, omega is the rotational moment of inertia, and alpha is the angular acceleration. The amount of torque required to accelerate a given wheel up to a certain angular velocity is directly proportional to the wheels rotational moment of inertia.

I agree there is a lot of discussion, much of it uniformed on the topic, but broad statements like
"Forget about the rotating weight, whether rotating or not it is just plain weight." is BS as stated.

I'm not trying to be confrontational, so I hope you don't take this the wrong way. Statements like this jump out at me as being wrong. I have a degree in mechanical engineering. I'm not stating that to impress anyone, just to establish some credibility for my reasoning, rather that stating that I read on the Internet that rotating mass does in fact make a difference to back up my postion.

I'm not trying to be confrontational, so I hope you don't take this the wrong way. Statements like this jump out at me as being wrong. I have a degree in mechanical engineering. I'm not stating that to impress anyone, just to establish some credibility for my reasoning, rather that stating that I read on the Internet that rotating mass does in fact make a difference to back up my postion.

red, excellent post. i think what jobst's point is, though, is that rotational mass is negligible, not zero. negligible for all but the most elite sprinters...

sd

Lighter wheels? I've lost 14lbs from my body, and plan to lose another 50lbs. If 350g less on the wheels is noticeable, I'm gonna fly up gradients like grease off a greasy shovel!


"Give me a mountain to slay, a col to defeat..."

Lighter wheels? I've lost 14lbs from my body, and plan to lose another 50lbs. If 350g less on the wheels is noticeable, I'm gonna fly up gradients like grease off a greasy shovel!


"Give me a mountain to slay, a col to defeat..."

I was just about to say that it's cheaper and more effective to cut body weight, if applicable.

red, excellent post. i think what jobst's point is, though, is that rotational mass is negligible, not zero. negligible for all but the most elite sprinters...

sd

Of course wheel weight makes a difference.

I think the point Jobst is trying to make, is that wheel weight is highly overrated in comparison to other things one might do (i.e., lose 50 pounds of body weight or get your legs stronger, or decrease wind resistance, etc.) to increase speed and acceleration.

Potholes in Montreal? NEVER! :)

I know what you mean.. I lived there for 10 years, and I remember when spring comes, the flowers and the potholes come into bloom..

Spring comes to Montreal? :) I figured Montreal was one of those places that had 12 months of winter.

I think there are different bikes for different purposes. If you have a touring bike, it isn't really supposed to be used as a racing bike. If you really want a more responsive bike, pick one up that is built for that. If you want to ride off trail, get a mountain bike or cyclocross. If you want to ride long distances with panniers or commute, then use a touring bike. Try to minimize weight where you can, but realize the limitations/purpose of the bike.

I think you are on the right track.

Alright so who to believe, the rotational mass is negligible or the rotating mass is HUGE crowd?

This thread saving me asking a similar sort of question. I've just had to buy a new front wheel which, due to what the LBS had in stock, is a more expensive wheel (a 20 spoke ALX-290 as opposed to the old 28(?) spoke AT-450 w/generic hub) and I've noticed my speed has generally increased. I still not sure whether to put this down to the new wheel or the fact that I've got another week of cycling in my legs.

Paul

Of course wheel weight makes a difference.

I think the point Jobst is trying to make, is that wheel weight is highly overrated in comparison to other things one might do (i.e., lose 50 pounds of body weight or get your legs stronger, or decrease wind resistance, etc.) to increase speed and acceleration.

Well his quote:

"Forget about the rotating weight, whether rotating or not it is just plain weight. This rotation stuff is another part of the myth and lore of bicycling"

implies that weight is weight - it has ZERO affect whether it is rotating or not. Two 20 lb bikes will perform exactly the same regardless of the weight distribution between rotating and non-rotating parts. He doesn't say it has neglible effect or that it is highly overrated, he says it has NO effect, in fact it is based on some "myth" of bicycling. According to him if you take two 20 lb bikes and add 20 lbs to each of them, but for bike one you fill a water bottle with 20lbs of lead shot and for bike two you add 20 lbs of lead weights to the inside of the rims (where they don't interfere with the brakes - tie them to the spokes near the rim) the two bikes will perform exactly the same. I'm saying that this is BS. For constant speed cruising yes there will be no difference, but for accelerating, bike one will maybe feel a little slower than before you added the weight, but bike two will feel like a absolute turd! there will be a huge difference!

When you say "Of course wheel weight makes a difference" what are you saying? Are you saying that there is a difference between two bikes that weigh EXACTLY the same amount, only one bike has heavier wheels and a lighter frame. If so, you are disagreeing with Jobst, if not you are simply wrong... :)

Your point about there are many other things we could that would make a bigger difference that getting lighter wheels is well taken. I could easily stand to lose 30lbs. Would I be better off losing 30 lbs or spending $800 on some lighter wheels...? Maybe I should cancel my order for my new $400 titanium and carbon fiber kickstand, and just skip that cheeseburger and fries for lunch tomorrow... LOL

the thinner, smoother tires at higher pressure alone will give a large increase in efficiency... and youre saving what i consider to be substantial weight regardless of where it's at (or from)...

i think you will notice a huge difference... albeit i cant give a quantifiable number

not only will it be easier to accelerate, it will be quicker/more responsive in handling as pointed out (due ot conservation of angular momentum)

okay, I was looking at your numbers...470 grams is a fair amount for a rim. what rim were you planning on using? also, 320 grams is a anvil of a tire. I think that my michelin carbons are like 250. if you got a pair of fairly high end training tires, you could take off 300 grams per wheel! remeber, a pound = about 450 grams. thats like a pound an a half just by getting new tires! just try that first and see how you like it.

Well I did end up getting a new bike.

A trek 1200.

My cruising speed is a couple mph faster, but I cannot attribute it to any one factor.

The 1200 is noticeably lighter. I haven't weighed it but I wouldn't be surprised if the weight difference is close to 8 lbs. It has an aluminum frame and carbon fork. The wheels have 32 spokes, 460 gram rims, and 320 grams tires (tires + tuffy liners).

My other road bike is a Trek 520. I have it setup with flat handlebars. It's an all steel bike. 565 gram rims, 36 spokes, 590 gram tires. Add on fenders and a rack. It's a truck. Add on panniers, a handlebar bag, and 3 water bottles, and it's a semi.

I wouldn't be fast on any bike, but even when the 520 is not loaded down I am slower on it (at the same perceived effort) than the 1200. It's probably a combination of weight, aerodynamics, and rolling resistance. The 1200 makes for a nicer ride when I don't want to carry luggage.

Last year my son gave me Bontrager xlite tires (28) for my birthday to replace my Armadillos (28). They are less than half the weight and claim to have low rolling resistance. Running at the same pressure (100psi) I was cruising at least 3km/hr faster on the flat. I didnt notice much difference in acceleration or going up hill, but I did notice the reduced gyroscopic forces made the bike more nimble to manoeuvre.