Bike weight impacting speeds
 

Sooo (another thread :)).

I haven't started to race yet but I am upgrading my bike from a Domane ALR4 to a Emonda SL6 Disc Pro. The bike I currently ride is 22lbs (Domane) the Emonda I am getting is 17.32lbs.

Why I am interested is because I am almost in the range for being a possible "lead pack or break away" finisher for the D riders in the ECCC (College cycling "league" in USA Cycling). Their averages for roughly 20-40 mile road races are around 23-24mph. Right now in group rides I can average 22mph every week we ride on my Domane.......

So I know speed conversions based on weight are super broad and determined by a lot of factors. The bikes are basically the same when it comes to how aero they are (not very) even though the Aeolus Pro 3 wheels on Emonda may be slightllyyyy more aero.

So lets say we put both bikes (Domane and Emonda) on a straight away for 20 miles completely flat and no head/tail wind. How much faster is the Emonda compared to the Domane in this situation.. Basically I am just trying to find out if just changing to the Emonda is enough to get me to 23/24ish mph average simply because it's less weight.

A few things first:

It's not about the bike.
Especially not in collegiate D.
You're probably not being held back by your current bike, despite not being the lightest bike in the pack.

That being said, this calculator is relatively okay for stuff like this. Bike Calculator The calculations I get show an increase of about 4 hundredths of a mph. So....

On the flats, weight isn't gonna change things basically at all. Weight really, really only matters on climbs. Aero is everything on the flats and on low gradient climbs. Spend the money on bike fit, power meters, head units, gas money to races, pizza, kits, literally anything but a new bike, honestly, when you already have a newer, nice bike.

I mean I weigh 115lbs so I am built for a climber and I want to race in more distance road races with climbs and I want a bike that will give me the advantage. Anyways I can get the Emonda new for over 50% off and I won’t have that chance forever.

Well, you asked about completely flat, so I answered about completely flat.

If you weigh 115 and want to climb and are at the pointy end of races then it can certainly make somewhat of a difference in that specific case. But it still won't be extreme.

Most racers wouldn't recommend buying a new bike to start racing.

Being 100 pounds heavier than you and having ridden a 55 pound touring bike I can assure you the weight makes little difference on a flat, steady cruise.

Check out Analytic Cycling, you can play with numbers there.
https://analyticcycling.com/ForcesLessWeight_Page.html

You keep asking the same question in different ways, and clearly want/think you need a new bike. You keep getting the same answer though. And until you start doing climbing races, and realize you want to keep doing them and have an aptitude for them (it's more than being skinny), you're best served hanging on to your cash. Don't buy anything. Accumulate. If you get there then you can buy something worth climbing uphill. I'm speaking as a guy who transitioned from crits and RRs to only doing hill climbs. You can spend a lot of money in this sport on good ideas only to realize you don't like the particular discipline, you're not really good at it, it hurts your body, that new girlfriend sure cuts into training time, those 2nd year classes sure are hard, that frat looks like fun...

I had TT bike that sure seemed like a good idea, a deep discount, and the answer to a bunch of problems. I rode it a handful of times, and then took a bath selling it.

Your 17 pound bike will go up mount washington faster than your 22 pound bike (assuming you're as comfortable on both bikes). Are you doing mount washington?

The time savings drop from there.

Buy a bike when you need a bike. You don't need a bike. Beyond that do what you want. But you keep getting the same answer.

Let them N+1, it's America. It's not like 15 rusty trucks parked across the front lawn.

If they were a 40 year old middle manager with cash to burn and just wanted a new bike then have at it.

As a collegiate racer with limited resources, thinking that a new bike is going to make a meaningful difference in performance, I think we're all more hesitant.

With two water bottles my race bike weighs almost 23 lbs.

In college, when I won our conference championship and overall my bike weighed closer to 24 lbs. With nothing aero anywhere (aero hadn't been invented, yet. ;D).

Like I said in two or three of the very first threads you made, you have to learn how to ride efficiently in a pack. Basically you need to be invisible. That's the only way you're going to survive these races at your current weight and power output.

This is how I ended up with a cross bike. Went to a practice on my MTB. It seemed fun. Bought the bike. Did more practices and a couple of races and decided, I really don't like cross.

I now dust it off once a year to use in our team's cross race. At this point, it's so old, there isn't much value left in it - everyone wants disc brakes and 11-speed and gravel geometry...

Unless the plan is to solo off the front and stay gone, the new bike plan won't pan out unless your events are hill climb TT's or fondo based timed climbing segments.

If that's the case, go for it, if not.....then don't confuse desire for something cooler with any functional improvement in 23mph road race.

I don't race much, but I know for sure it ain't the bike. Or the engine frankly. It's the stupid and inexperience that lies between my ears.

Use the money instead to get to and from a bunch of local crits or something your college isn't doing. Or use the money to take weekend trips to the mountains or somewhere fun to ride for training with buddies.

Own a meter yet? Have a TrainingPeaks or other subscription? A coach? Put the money to those.

I make no bones about just being an engineer that likes "gear" and "kit" when I can afford it. It's fun, it's cool. It won't make me win though. I just like it and like to geek out.

You said you are joining college soon, right? Enroll in a physics course, then you will be able to answer the question yourself.

Dropping weight isn't how you improve the flat-ground cruising speed of a bike.

I rode my touring bike to work this morning, very heavily loaded for camping, it weighs about 70lbs right now. Normally on my commute the same bike weighs 30lbs. I ended up going a couple mph slower than usual, and a good chunk of that was because of the air drag from four full panniers and a rack pack, plus the fact that I was riding at a slightly lower effort level than normal.

You're looking for a 9% speed improvement by dropping weight?
Even if you're doing an uphill time trial rather than riding on flat ground, 5lbs isn't going to net you anything close to that. Maybe if you dropped tens of thousands of dollars putting together an exotic 7lb road bike, you could see an effect of that magnitude.
On flat ground, 5lbs isn't going to have any tangible effect on cruising speed. Power required to accelerate the bike+rider will be a few percent lower, so you may have an ever-so-slightly easier time holding onto things out of corners or whatever.

In the words of Simon & Garfunkel, you are hearing and not listening

Your question above (emphases yours) is a very simple physics question. On a mostly flat parcour, weight mainly affects rolling resistance. Assuming semi-decent aerodynamics, 5 lb reduction in mass results in maybe 0.1 mph speed increase. I plugged in your weight (115 lb or 52 kg) and assumed you are doing 205 W (to ride at 22 mph). Changing the bike from 7.7 kg (17 lbs) to 10.5 kg (22 lbs) barely results in an increase of 0.1 mph. You'd get better speed increases by using faster-rolling tires (increase of 0.2 mph). Put it another way, you could ride a bike made entire of unobtanium and having a mass of 0 kg, and you still can't get a speed increase from 22 mph to 23/24 mph based on decrease of mass per se (the speed increase for a 0kg bike would be 0.2 mph).

On a 6% climb, you'll be ~0.4 mph faster. Over the distance of a mile, that comes out to be 10 seconds.

You can play around with the various parameters here: https://gribble.org/cycling/power_v_speed.html


I should also note that those bigger-framed riders may just climb as well as or even better than you do. I was a full-on fat-ass at 174 cm and 72 kg and broke away on a hilly circuit race while racing ECCC D1 (back when there were enough riders for two separate fields in the Ds). By the same token, you should not presume that a willowy built per se is indicative of climbing prowess. A poster here (@carpediemracing) had a build similar to yours, but aerobic endurance wasn't his forte; what he is good at are sprints. He is very good at seeking shelter in the pack and then punching it

Physics class seems like a good idea. Also 15lbs is lighter than 17lbs, so there is still room for improvement.

spend the money on burritos and strength training instead.

I'm rebuilding juniors climbing bike this weekend. Do I measure weight with or without cages and pedals?

Do you want theoretical or practical weight?

The guys on the Weight Weenies forum usually remove pedals and cages. but you need both to actually ride the bike, so that weight matters in the end.

Also, you won't remove your pedals and cages for a UCI weight check so why bother weighing without them?

If you're doing a UCI check, I love the new Wahoo trick that has a tiny bolt so you can screw the Bolt to the mount, which makes the computer a part of the bike for the weigh in. I think they've done that with other items in the past to make them count.

I am a Weight Weenie member and often get criticized - esp on wheels because I provide weight ready-to-ride. I agree with you it is the whole thing - including the kit.

Stuff that is optional - a cage, I can see leaving off. Pedals, no. They are just done that way as people have options as to which pedals they use and there are a lot of games played lighting the pedals and putting more mass in the shoe cleats.

This will be ~12# build (with pedals). It could be closer to 11# but that means more cash and getting rid of steel spindles in the pedals and cranks, something that at least emotionally makes a big difference.

Some here may recall a big fail on UCI weight and National DQ.

This is for fun / hill climbs as light bikes are significantly faster up long 50-60 min climbs solo.
For racing - junior is bringing his regular bike which will be 3# heavier. But it is faster.

How about an update from OP on collegiate racing?

Just putting this out there: You're going to crash/get crashed in collegiate. Race what you can replace.

Also, in the D's, fitness and pack skills are the deciding factor in the races. I hope OP figured this out.