Saving circa 500g on wheels………

…… is it worth it?

I’m building a bike for enduro racing this year but am on a budget.

I know the theory that weight saving at the wheel is more noticeable than anywhere else but my question is this –

Would you consider spending £200 on saving 500g at the wheels over spending the same amount of money elsewhere on the bike for a greater weight saving as a worth while exercise?

Any thoughts?

It depends on the rest of the spec. Especially tyres- the differences are all relative, my traversees are noticably very different to my 721s and that’s about a 500g difference, but if I stick dualplies on them then the higher overall weight diminishes that difference if you see what I mean.

It’s all relative. What about the tyres, brakes, tubes/tubeless and cassette? Are these at an optimum?

I’m really unsure how spending £200 can save you 500g anywhere other than wheels, unless you’re doing something like ditching a dropper post for a carbon one and swapping dh tyres for xc racing jobs.

Mind if you’re going enduro (stage), rather than endurance racing I’m not sure why you’d bother doing that really.

Stick with the wheel change if you reckon you’ve got nothing else to spend the money on, and really want to spend it on the bike.

You can lose about 100g just by spending £50 instead of £25 on a rear cassette.

I know the theory that weight saving at the wheel is more noticeable than anywhere else, but it doesn’t really equate to a difference in performance on a mountain bike, and especially not in enduro racing, when you’ll be carrying stuff and getting wet and covered in mud.

Spend the £200 on good B&Bs the night before the race.

Oh, also… What sort of enduro racing? Proper enduro, or endurance xc?

sorry i mean 12 hour endurance not enduro.

The drive train will be the current stuff I’ve got, X9 rear mech, XT front mech, X0 cassette & XT crank so going any lighter will cost more than £200

vinny – It would be tough to be honest to save 500g for £200 outlay but with some careful shopping around.

+1 for spending slightly more on a light cassette – best bang for your bike. Bikeradar ran an article saying that it costs about £2.48 to lose one gram http://www.bikeradar.com/news/article/bike-weight-saving-more-costly-than-silver-32960
Tyres and tubes also offer economical weight savings.

Will be tubeless with rim strips if using current wheel set or without needing the rim strip if i go for the new wheels.

Tyres will be the same no matter which wheels.

Crest rims.

I went for 2 x 900g tyres, to 2 x 570g tyres(nobby nics). I noticed quite a difference.

If you are spending money to save weight then save it at the rims/tyres for sure. It probably won’t make you much faster but it will fell like it did.

Remember that lossing weight at the cassette is not the same as lossing weight at the rim/tyre/tube. The same weight saving at the rim will reduce the moment of inertia of the wheel far more than the same weight saving at the hub/cassette area so I would pick lightweight rims/tyre/tubes before splashing out on expensive cassettes.

My recent experience –

Changed Orange Five aluminium bars to Syncros Carbon bars – 150g saving

Converted wheels to Stans No Tubes – 100g saving per wheel

The difference to the way the bikes rides after going to tubeless is really noticeable, it’s a lot faster to pick up.

Remember rotating mass has a big influence on the way a vehicle accelerates whether it be a push bike or motorbike.

I would say change the wheels and go tubeless.

If you are riding for 12hrs whatever weight you can save will help, also look at your Camelbak and contents too.

But weigh everything you have first, before spending.

Rotating mass in bicycle wheels has an insignificant effect, however often the myth is repeated.
If anyone can show it makes a difference, rather than claiming it does, I’m open to having my opinion changed.

TBF crikey me sober chum, so does non-rotating weight.

Rotating mass in bicycle wheels has an insignificant effect, however often the myth is repeated.

Can you show me anything that says it doesnt make any difference?

Indeedy, my mechanically adept acquaintance.

It’s interesting how it’s become so widely accepted..

Rotating mass in bicycle wheels has an insignificant effect, however often the myth is repeated.
If anyone can show it makes a difference, rather than claiming it does, I’m open to having my opinion changed.

TBF crikey me sober chum, so does non-rotating weight.

🙄

Can you show me anything that says it doesnt make any difference?

It’s not that it doesn’t make any difference, just that the difference is very small, and is lost in the complexities of the operation of the bicycle.

It’s also almost invariably considered in an isolated way; no thought is given to the whole bike/rider/kit involved.

This is my best reference;

http://biketechreview.com/reviews/wheels/63-wheel-performance

crikey – Member

Rotating mass in bicycle wheels has an insignificant effect, however often the myth is repeated.
If anyone can show it makes a difference, rather than claiming it does, I’m open to having my opinion changed.

It seems I’m in the kind of mood when I ask people making unsubstantiated claims yet demanding proof from others, to apply their demands to their own posts.

skywalker, you can make a contribution if you want to.

I would make a contribution, but I think my time will be wasted explaining it. Clearly you two know better than the laws of physics.

I would make a contribution, but I think my time will be wasted explaining it. Clearly you two know better than the laws of physics.

Come on, don’t be shy. Explain the difference that 500g weight loss at the wheels will make in a 12 hour mountain bike race, Professor.

Having had practical experience (i.e. used) light frames and heavy wheels and also heavy(ish) frames and light wheels, I can tell you I’d prefer the latter any day.

crikey – Member

Explain the difference that 500g weight loss at the wheels will make in a 12 hour mountain bike race, Professor.

The mood can last for a long time sometimes. Explain why a 500g weight loss at the wheels will make an insignificant difference in a 12 hour mountain bike race, Professor?

…and then explain the difference from a 500g weight loss that isn’t rotating…

Well, if you’re feeling keen, feel free.

Or alternatively continue demanding other people provide proof, while ignoring requests for the same. Up to you really.

A test a while ago, where a roadie went up Alp D’Huez 4 times on different set-ups, including with his tyres filled with water IIRC, showed **** all difference to his times (and IIRC his HR was recorded).

That’s the “physics” that skywalker etc appear to be on about – no better test has been done AFAIK…while light wheels fell realy fast, they’re not actuallt significantly faster.

I accept an MTB climb may be slightly different.

Crikey, chum, how am I mechanically inept?

crikey . Do you race, and if so any good?. Just wondering.

If you look at the car world for instance, losing 3kg a corner ( according to pro testers) makes a noticeable difference.

I ( unscientifically of course, but i’m using real data (me) rather than lab data ) notice a difference going from a heavy(ish) wheelset to a light race wheelset. Whether thats unsprung mass or just lightening of the bike doesn’t really make a jot of difference.

Now, if the context of the question ( and OP mentioned saving 500g, a lot of weight) was would i feel the difference between say a 1250g wheelset and a 1050g wheelset, then i feel the difference would be negliable because of the flex and precaution taken on a really light wheelset would ofset the weight advantage. Think Njee on here said that a 900g wheelset was built but they prefer the ride and safety of a slightly heavier wheelset.

So to the OP, spend that money on the light wheelset, you will notice a difference but also choose tyre and tyre pressures carefully. On a light wheelset keep them quite high, say above 33psi because you will feel a tyre roll of the rim any lower than that plus ( IMO) they roll better without losing too much on traction

Skywalker if not for the others then I’m interested to know why.

Once you’ve explained you don’t have to check back and answer any of the others comments as I will draw my own conclusion 😉

My worry is not so much the speed aspect its the pushing an extra 500g or rotating weight when I’ve been in the saddle for 12 hours. How much will it have taken out of me having to rotate that extra 500g over the previous 12 hours 😕

Come on, don’t be shy. Explain the difference that 500g weight loss at the wheels will make in a 12 hour mountain bike race, Professor.

Consider the kinetic energy and “rotating mass” of a bicycle in order to examine the energy impacts of rotating versus non-rotating mass.
The translational kinetic energy of an object in motion is:

Where E is energy in joules, m is mass in kg, and v is velocity in meters per second. For a rotating mass (such as a wheel), the rotational kinetic energy is given by

where I is the moment of inertia, ? (pronunciation: omega) is the angular velocity in radians per second. For a wheel with all its mass at the outer edge (a fair approximation for a bicycle wheel), the moment of inertia is

Where r is the radius in meters
The angular velocity is related to the translational velocity and the radius of the tire. As long as there is no slipping

When a rotating mass is moving down the road, its total kinetic energy is the sum of its translational kinetic energy and its rotational kinetic energy:

Substituting for I and ?, we get

The r2 terms cancel, and we finally get

In other words, a mass on the tire has twice the kinetic energy of a non-rotating mass on the bike. There is a kernel of truth in the old saying that “A pound off the wheels = 2 pounds off the frame.”

There you go, young grasshopper.

Radiogaga, Windy and Skywalker…jeez…did you even read crikey’s linked-to article?

Al, I said adept, y’know, as a complimentary thing…

Interestingly enough, we have done this before…

http://singletrackworld.com/forum/topic/rotating-weight-does-it-make-any-difference-and-why

Anyway, a quote from the above article;

So, what do all these numbers mean? It means that when evaluating wheel performance, wheel aerodynamics are the most important, distantly followed by wheel mass. Wheel inertia effects in all cases are so small that they are arguably insignificant.

How can it be that wheel inertial forces are nearly insignificant, when the advertisements say that inertia is so important? Quite simply, inertial forces are a function of acceleration. In bike racing this peak acceleration is about .1 to .2 g’s and is generally only seen when beginning from an initial velocity of 0 (see criterium race data in Appendix D ). Furthermore, the 0.3kg/0.66lb difference in wheels, even if this mass is out at the rim, is so small compared to your body mass that the differences in wheel inertia will be unperceivable. Any difference in acceleration due to bicycle wheels that is claimed by your riding buddies is primarily due to cognitive dissonance, or the placebo effect (they paid a lot of money for the wheels so there must be some perceivable gain).

crikey . Do you race, and if so any good?. Just wondering

Not anymore 😥
Old age has crept up, hidden by a job and kids, then jumped out on me and scragged me. I crawled around the 3 Peaks this year, might have another go, but a 17 year gap added well over an hour to my time.

..sorry, forgot; changing wheel weight is very noticeable, in that we/you/me can all tell that it’s changed, but it doesn’t have the effect in terms of actual, measureable performance that we assume.

well get back racing 🙂

Anyway, firstly it does say that the vest wheels are those that are light, aerodynamic with no brake rub. ALso this test was on a road bike where (admittedly) wheel weight isn’t as important, wheel aerodynamics are because most of your time your spend at speed. MTB’ing on the other hand is far more stop/start, so ( and its written in there) lighter wheels allow faster acceleration where in many events time can be gained.

So , cynic-al did you read this as well and realised the biase of road riding or are we just jumping on the scientific road bandwagon?.

+1 for light wheels. I’m considerably faster on my ZTR 29er Race Golds 1345 g, tubeless RR and RRon, XTR cassette, ti skewers, and than my Shimano MT75 UST wheelset 1900 g with 2 x NN I use for training.

well get back racing 🙂

Anyway, firstly it does say that the vest wheels are those that are light, aerodynamic with no brake rub. ALso this test was on a road bike where (admittedly) wheel weight isn’t as important, wheel aerodynamics are because most of your time your spend at speed. MTB’ing on the other hand is far more stop/start, so ( and its written in there) lighter wheels allow faster acceleration where in many events time can be gained.

So , cynic-al did you read this as well and realised the biase of road riding or are we just jumping on the scientific road bandwagon?.