Wheel Weight - Total / Rotational

teisetrotter

Bit of a one for the experts here. I am thinking of building, slowly, a new bike with the plan of going down a weight wheenie route ...... but not with the idea of sacrificing performance or indeed the kids inheritance.

So on wheels. You can obviously buy some very light weight wheels, look at the Spada Stillettos at 1260g for alloy at around the £600 mark. But I see there are other arguments about rotational weight which Rolf among others claim can counter the extra few hundred grams on the wheels.

Please spare me the comments of 'who cares'. I want a little project and in the end I want to ride it around the hills and downs of Kent with all the potholes and crud that entails. So this is a little academic answer to fill in the dark nights to come. So humour me ... please.

JayKosta

Since you didn't mention any racing goals, I think you should consider things in this sequence -

1) Reliability - will the wheels be durable to allow you to ride home considering the road conditions, etc.

2) Maintenance cost and time - broken spokes, wheel truing, tires, etc.

3) Your weight and power - reducing the weight of wheels can reduce their stiffness.
This would be made more obvious if you are large and/or very strong.

4) For climbing hills, low weight is an asset. for descending and flats, aero is a consideration.

Jay Kosta
Endwell NY USA

imposter2.0

if your question relates to the relative value of rotating weight v total wheel weight, then read this thread instead...be warned though, there's a few pages of it...

viewtopic.php?f=40013&t=12870011

davidwilcock

Imposter wrote:

if your question relates to the relative value of rotating weight v total wheel weight, then read this thread instead...be warned though, there's a few pages of it...

viewtopic.php?f=40013&t=12870011

You've just cited my favourite ever thread on here.

Well worth a read, if you are in a rush, just pick out P Tuckers posts.

imposter2.0

davidwilcock wrote:

You've just cited my favourite ever thread on here.

Well worth a read, if you are in a rush, just pick out P Tuckers posts.

Mine too. If there was a Booker Prize for internet threads, that would win it..

cycleclinic

Without knowing more about it is difficult to say weather low weight wheels will be a potential problem for you or not.
I have 1360g wheels built using XR-200 rim in 28H drilling.
Low rim weight is something you can feel I do notice the difference when I ride my Trek compared to my Pinerello with it Nemesis rims but I cannot say how much difference the light wheels make but in principle it makes some difference. Like you [OP] I built a light bike for the sake of it.

The XR-200 is about as light as alloy rim gets for it to be reliable and they can be had in 24H and 28H drillings just like the spada's wheels. With the right hub a 1300g build or less is possible. Spada have got the hubs which is how they do it. there rim cannot be much if any lighter than the XR-200. Stan's tried a 350g version of the 340 a while back, alot of people had trouble with them, if the spada rim is similar to this then avoid, if it like the XR-200 they stand a good chance of being good wheels.

Go for light wheels of some sort (I have no experience of the Spada's) it is a WW build after all it's not meant to be sensible.

teisetrotter

Imposter wrote:

if your question relates to the relative value of rotating weight v total wheel weight, then read this thread instead...be warned though, there's a few pages of it...

viewtopic.php?f=40013&t=12870011

Ahhh ha, I did try the search button, but obviously not well enough. I'll read through.

I agree this is not on the sensible route, it's just the normal obsessional approach a man takes to hobbies. I am around the 165 - 170 mark, depending on beer, cake to exercise ratio. Power ........... dunno, I am 46 and still ride with the young boys. I do occasionally race, but in the vets where I hold my own in the peleton in my age group .... but I am not winning anything.

So I don't have to worry about uber stiff, I do worry about pot holes and I am interested in weight.

ugo.santalucia

Teisetrotter wrote:

Imposter wrote:

if your question relates to the relative value of rotating weight v total wheel weight, then read this thread instead...be warned though, there's a few pages of it...

viewtopic.php?f=40013&t=12870011

Ahhh ha, I did try the search button, but obviously not well enough. I'll read through.

I agree this is not on the sensible route, it's just the normal obsessional approach a man takes to hobbies. I am around the 165 - 170 mark, depending on beer, cake to exercise ratio. Power ........... dunno, I am 46 and still ride with the young boys. I do occasionally race, but in the vets where I hold my own in the peloton in my age group .... but I am not winning anything.

So I don't have to worry about uber stiff, I do worry about pot holes and I am interested in weight.

Heavy rims are not good, they feel dead, light rims are not good either, typically... there is a happy medium which is between 400 and 500 grams for a clincher. Hubs need to have good bearings, no play, a decent geometry and a good freewheel mechanism. Spokes carry most of the aerodynamic drag. You can cut them shorter with a deep rim, you can cut the number or you can cut the width... the last two contribute to a marginally faster and lighter wheel. The approaches are either or and not to be attempted all at the same time. A 20 spokes rear wheel with a light rim and light spokes is a crap wheel.
Whatever approach you try, it is very hard to go below 1500 grams for a set of wheels... you can by using light hubs, which are typically disappointing, short lived and don't give you a single second advantage uphill/downhill or on the flat.

cycleclinic

Well potholes are a worry to me too. I ride my light wheels alot and have put a few thousand miles on them so far without incident. I do hit holes, I hit one hard at speed on Tuesday-looked down and the wheel was still fine relief. One day that will not be true any more but I get wheels in all the time that have hit holes and the owner thinks it needs a true until I point out the crack in the rim. These rims are generally heavier (c.500g) as they are the 20H-24H kind as found in various factory wheels.

Your weight is light so you can get away with more. If you go for a light rim (XR-200 veloicty aerohead e.t.c) then 28 spokes on the rear will be fine and so will 24 on the front. The spoke could be Sapim Lasers so long as the hub has wide flange spacings (the geometry ugo refers to). If you go for a more aero wheel with a deeper rim, lower spoke count, then the weight will end up being higher unless you use carbon rims.

An example would be XR-200 rims 24F/28R with laser spokes/alloynipples and Novatec A171/F172 hubs. weight would be 1420g.
The lightest 30mm deep rim on the market (alloy) is the Kinlin XR-300 a pretty decent rim really. that in 24F/24R with with Novatec A171/F172 hubs (the the F172 can be had in 24H drilling) weight would be 1560g.
Miche hubs can be suppiled in 20H and 24H drillings so an slightly more aero wheel is possible with these but the weight will go up more as the hubs are heavier.

The later wheel is a bit more aero and stiffer. Which is more robust I am not sure but I would say they would fair abou the same hitting holes.

Light hubs like Novatec A291/F482 should be used by riders who accept there downsides and have other wheels when the weather is a bit poor and not used by ridesr that heavy as that loads the bearing more. I have many wheels and whole shop to build more when I need and to fix issues when they occur (thankfully they have not occured yet). so I can use "unrelaible" light hubs and not worry not everyone is the same position as me.

All light weight hubs have there downsides. for some it may be unrelaiblity in poor weather, for others it is poor geometry requiring deeper rim or higher spoke drillings or expensive. the worst light hubs will have all three downsides.

blinddrew

Going back to the OP's question about total vs rotational, and still staying firmly within the "humour me" camp, I had a read of the first couple of pages of the linked thread (too much anger, people should relax more) and it occured to me that there was a couple of things that were being missed in the arguments.
Firstly that inertia exists in 2 types, linear and rotational, most of the discussion seemed to be about linear inertia which is fine for looking at the movement of the bicycle as a whole but rotational inertia increases as a square of the radius. Ergo taking weight off the rim will have a much greater effect on the rotational acceleration of the wheel than taking it off the hub. Hence light rimmed wheels appear to "spin up" much more quickly.
The other thing that seemed to be being dismissed (at least it was in the first few pages, they may have got onto it later) was real-world affects on the maths. Unless you ride on a track, and especially if you're unlucky enough to ride on rural roads in the UK, the road surface means you are constantly being decelerated by bumps and rough surfaces. Some of this is absorbed (and released) by the tyre, some by the frame etc but all of it results in an increase in entropy. You're also constantly accelerating against changes in wind. What this means is that you will generally feel the effects of a lighter bike / wheels more than you should because from the moment you get on to the moment you get off you are constantly working to overcome decelerations even if you're maintaining a constant speed.

mpie

blinddrew wrote:

Going back to the OP's question about total vs rotational, and still staying firmly within the "humour me" camp, I had a read of the first couple of pages of the linked thread...

I scanned through it too. Apart from the inevitable knee=jerk reactions you get on internet forums, the main thing that stood out for me was the lack of appreciation for the distinction between science (which deals largely with absolutes) and engineering (which focusses on 'what matters'). As an ex-scientist and practicing engineer, I long ago learned that particularly in a field you don't have deep experience in, it is very dangerous to make snap judgements on what matters and what doesn't. Even more so what that distinction depends on human perception which can be both incredibly acute, but is also hard to evaluate. There seems to be quite a parallel with this tread and similar threads on hi-fi forums about whether different digital interconnects sound different. Both can be proved/disproved depending on what assuptions you make in your science. Both end up with the dichotomy of 'I can feel the difference' but 'I can't measure/prove it'. For some people that's not good enough. I've learned to live with it - it's the joy of the art called engineering.

imposter2.0

blinddrew wrote:

Going back to the OP's question about total vs rotational, and still staying firmly within the "humour me" camp, I had a read of the first couple of pages of the linked thread (too much anger, people should relax more) and it occured to me that there was a couple of things that were being missed in the arguments.

If you'd read more than the first couple of pages, you would have seen that neither of those things were missed.

blinddrew

Imposter wrote:

If you'd read more than the first couple of pages, you would have seen that neither of those things were missed.

Fair enough, there was only so much negativity I was willing to wade though. :¬)

teisetrotter

Yes it is a pity about the petty squabling, but that is interesting advice. I'll use it to start building up the spec' I can't find much on these Spada's and the weight seems to be lost in the hub. How I am not sure and whether they are fair weather lookers only.

The real conclusion in that long thread was that whilst any weight loss equals less to push around, ignoring the counter productivity of flex etc. Other than that it was an academic study into something that makes infinitesimal difference for the average person.

So I'll continue with my personal bike build based on a good reliable light weight wheel that looks good in my eyes.

ugo.santalucia

Teisetrotter wrote:

Yes it is a pity about the petty squabling, but that is interesting advice. I'll use it to start building up the spec' I can't find much on these Spada's and the weight seems to be lost in the hub. How I am not sure and whether they are fair weather lookers only.

The real conclusion in that long thread was that whilst any weight loss equals less to push around, ignoring the counter productivity of flex etc. Other than that it was an academic study into something that makes infinitesimal difference for the average person.

So I'll continue with my personal bike build based on a good reliable light weight wheel that looks good in my eyes.

This mr Spada builds wheels, fine... if you want a set of hand built wheels, why don't you get one made bespoke for you, rather than one made by someone who has no idea of who you are, how much you weigh and how far or fast you ride? Could it be that if it's made for you, it will suit you better? Just guessing...

teisetrotter

I agree and that is the exact conclusion I had come to, probably not clear in my post though.