Slower with mudguards?

[amediasatex]

....with a 42.5 kg load at 29 km/h. ...but I suspect you’re heavier than 42.5 kg and have two tyres. Multiply the power difference accordingly.

I don't think a weight multiplication is necessary is it? As you say he has 2 tyres, and his load is split between them, assuming 50/50 front/rear (bad assumption I know...) that's a 85kg rider, so the figures stand as they are. if you're massively more or less than 85kg then obviously need to adjust, but not by much really.

But back to the original point, tyres do make a big difference, as you've illustrated there even two 'quick' tyres have a difference of over 4W per tyre, so 8-10W in total. Cheaper/slower tyres can easily reach double that again.

It would be good to get some actual figures of mudguard impacts at different speeds, yaw angles, mudguard widths and clearances from tyre so we could know if the impact they have is in the fractions of a W, single digit W, or double digit W areas.

It's already been proven numerous times that rider position has the biggest effect, followed by clothing and tyres (order dependant on specifics), so even if performance of the rider was a constant (we know it isn't), unless the effect from mudguards is really quite large, it could easily be that all the extra effort people attribute to them is actually 'other things'.

I've been hunting but not found much other than the limited and not particularly rigorous BQ tests...does anyone have any links to some actual decent testing of aero effect of mudguards, with test descriptions and figures? All I can find is anecdata, phrases like "it's obvious", "clearly" and "it's well know that", and dubious/biased correlation with no implied causation. And as we well know many 'obvious' and 'well known' things are demonstrably false when actually investigated.

I want evidence dammit!

[Samuel D]

....with a 42.5 kg load at 29 km/h. ...but I suspect you’re heavier than 42.5 kg and have two tyres. Multiply the power difference accordingly.

I don't think a weight multiplication is necessary is it? As you say he has 2 tyres, and his load is split between them, assuming 50/50 front/rear (bad assumption I know...) that's a 85kg rider, so the figures stand as they are. if you're massively more or less than 85kg then obviously need to adjust, but not by much really.

Agreed, but you can do better than this rough estimate by multiplying the relevant power figure by the ratio of your all-up weight to 42.5 kg and then again by your speed divided by 29 km/h – as long as you use the power figure associated with a similar tyre drop to your own (which won’t necessarily be at the closest BRR pressure to the one you use). The drop can be estimated by comparing load versus pressure to those for which BRR tests.

You’d count the same thing twice if you accounted for both the load difference and tyre count separately. My statement could have been clearer about that.

If tony_mm supplied his weight (and bicycle weight for good measure), we could calculate with useful accuracy the difference his winter tyres make, keeping in mind that the power associated with rolling is higher in the real world than on test drums (by about 1.5 × according to Tom Anhalt; this is because of Jan Heine’s well-known ‘suspension losses’). This increases the difference between tyres too.

It would be good to get some actual figures of mudguard impacts at different speeds, yaw angles, mudguard widths and clearances from tyre so we could know if the impact they have is in the fractions of a W, single digit W, or double digit W areas.

It's already been proven numerous times that rider position has the biggest effect, followed by clothing and tyres (order dependant on specifics), so even if performance of the rider was a constant (we know it isn't), unless the effect from mudguards is really quite large, it could easily be that all the extra effort people attribute to them is actually 'other things'.

I agree with all of that too, and can’t help with the data. I believe my mudguards slow me down because I can feel through the steering that the wind tugs at the front mudflap. But you’re making me start to question even the relevance of that. Besides, my mudguards aren’t aero-optimised (or water-optimised, sadly).

Wind-tunnel testing of bicycles is hard and usually misleading. For example, all sorts of bicycles (like the one on page 3 of this thread) have heavily shaped top tubes notionally designed to reduce drag. If they succeed in doing that for one rider position they almost certainly have the opposite effect for another position, the rider strongly influencing airflow in that vicinity. The rest of the bicycle is as difficult to test or model, and that’s before you get into drafting other riders as we all do for most of the time in group rides and races. What does your aero head tube do when the vortex sheet coming off someone’s bum hits it sideways?

The only sure way to reduce drag in all circumstances is to reduce component size, which is why I strongly doubt that the enormous down tubes on carbon bicycles are aero at all in the messy real world. It’s also why I prefer narrower tyres than are currently fashionable.

[mig]

what if you have a screaming tailwind?

(never happens i know )

[Samuel D]

I sense your question is for fun, but rolling resistance is always lower than a cyclist’s power output, so you quickly ride faster than the tailwind and turn it into a relative headwind. That’s why you never feel the wind on your back for long on a bicycle.

[Brucey]

-unless you are climbing.... in which case you can have a useful benefit from a tailwind. Indeed at one time I think some riders on long-distance rides used to carry kite-shaped things like little sails and used them on their backs when conditions were favourable.

cheers

[tony_mm]

@ SamuelD:

Here you are:
My weight: 149 lbs
Weight of my winter/ rain bike with fenders, Garmin etc...: 17.5 lbs
and 2 x 24 oz. water bottles.

[tony_mm]

Here the link to the Specialized "win tunnel" #aeroiseverything and all their tests and videos.
https://www.youtube.com/watch?v=b-bchlA ... SCDKCKR97t

They are not 100% scientific and it is "only" a wind tunnel test but better than nothing AND it gives some figures


@ ALL:
if your are interested to have Specialized testing fenders/ mudguards vs. without please ask them at #aeroiseverything via Facebook, Instagram etc....
I did already but the more we are the more chance we have that they run a test.

[Flinders]

........

Case in point, last nights club ride was accomplished at a dismal 14.5mph average, because the weather was terrible! It was windy, cold, wet and we were having to go carefully. If I hadn't also ridden that same route on the same bike numerous times before, with the same people with an average average (!) of 17-18mph, and solo 20mph, I might have falsely attributed my slow speed to the winter bike/guards rather than the weather, and especially so if I rode a 'summer bike' when the weather was good.

Oh. I tend to feel when I get up to 15mph I'm doing okay (solo). And I thought groups went faster, which has been my excuse.
That put me in my place...
Maybe I can now say that my current rather sad 12mph rides are because of the weather? Pity I used to be able to do 15mph before in the winter, so I can't really use that one.

I am slow at the moment (building up after a long break, plus a short break for the icy weather) but I think if anything is to blame right now it's the wind- I have never had a period of time when wind has been so much of a problem for me. But maybe I notice it more because I'm unfit. Or hey- maybe it's all the mudguards! A new excuse for me to use, great.

[amediasatex]

Speeds are all relative Flinders, I've done just as many rides with an avg. under 10mph as I have with avg. over 20mph. As long as you're having fun (on average) that's all that matters really!

Blame the guards, blame your tyres blame the weather, whatever, "today I just don't feel like riding fast" is as good as any of them, and probably closer to the truth

[Samuel D]

@ SamuelD:

Here you are:
My weight: 149 lbs
Weight of my winter/ rain bike with fenders, Garmin etc...: 17.5 lbs
and 2 x 24 oz. water bottles.

Thanks. So using your stated pressure of 95 PSI, Bicycle Rolling Resistance’s power figures for your tyres, Tom Anhalt’s correction factor for suspension losses on typical roads, and Bike Calculator for a quick estimate of speed versus power, I reckon your winter tyres slow you down by 0.8 km/h around 29 km/h. At faster speeds, the difference would be slightly less. At around 25 km/h, the difference would exceed 1 km/h.

Separately, is your winter bicycle really 17.5 lb (7.9 kg) with pedals, the disc brakes, mudguards, Garmin, etc.? I mean to ask if you have weighed it yourself or are relying on specifications. Then again, your winter hack costs more than my car if my Googling is worth anything.

By the way, it’s fun to watch your speed plummet as you change the air temperature on Bike Calculator from a hot summer’s day (e.g. 30°C, though I once rode in the Alps on a 37°C day) to winter cold. And the calculator doesn’t know you need a draggy winter jacket and have trouble breathing in 3°C.

All in all, it’s no wonder winter feels like hard work.

That put me in my place...

Spare a thought for amediasatex, though. The other day Chris Froome averaged 37.9 km/h on a 224.5 km training ride in South Africa. Admittedly, it’s warm over there at this time of year.

[amediasatex]

And Froome was probably just bimbling and taking the long way back from the shops!

I'm far from quick in my club, midfield mediocre at best, the quick boys still use guards in the wet though

[tony_mm]

Thanks. So using your stated pressure of 95 PSI, Bicycle Rolling Resistance’s power figures for your tyres, Tom Anhalt’s correction factor for suspension losses on typical roads, and Bike Calculator for a quick estimate of speed versus power, I reckon your winter tyres slow you down by 0.8 km/h around 29 km/h. At faster speeds, the difference would be slightly less. At around 25 km/h, the difference would exceed 1 km/h.

Separately, is your winter bicycle really 17.5 lb (7.9 kg) with pedals, the disc brakes, mudguards, Garmin, etc.? I mean to ask if you have weighed it yourself or are relying on specifications. Then again, your winter hack costs more than my car if my Googling is worth anything.

By the way, it’s fun to watch your speed plummet as you change the air temperature on Bike Calculator from a hot summer’s day (e.g. 30°C, though I once rode in the Alps on a 37°C day) to winter cold. And the calculator doesn’t know you need a draggy winter jacket and have trouble breathing in 3°C.

All in all, it’s no wonder winter feels like hard work.
.

Hi SamuelD,

Thanks form checking! I am using the same source and calculator as you.

The difference in average speed between my two bikes is more like 1.5 to 2 km/h and to me as I said due to the tires and the fenders. Certainly also due to other small factors like temperature, clothing, etc...

Yes my winter/ rain bike is quite light but quite expensive indeed with Dura Ace Di2, powermeter, Pro Vibe aero cockpit and the DT Swiss ERC 1100 Dicut 47. But it is intended to be used at least 20 years.


Anyway to me riding with fenders do slow me a little bit but they increase so much the quality of the ride in rain that it is more than worth it. I don’t try anyway to achieve PR under the rain etc....I just want to be able to enjoy my rides even if it is raining. And for that I have a nice dedicated rain bike with fenders. The life is too short to ride a nice bike only in the summer.

[willcee]

REF LAST ...interesting ambitions, I'm referring to Dura ace DI2 in all its forms and your hope to use it, working in 2038.. GLWT, If And thats a Big'' IF'' it were cabled mechanical you could probably see that ambition being realised..as mentioned by Brucey in another part of this tech forum some months ago when the amassed ranks of bike tecks from SKY couldn't get a front or was it rear derailleur of this current DI2 Breed to become connected and operate for a fellow competitor, and I don't know how many generations of DI2 there have been to date..You may have a situation that only a skilled electronics nerd and then if you could pay him to get into its innards if parts were still available and even today some aren't for previous DI2..
On another similar issue the classic car guys are talking with Bosch about the need for old school ECU's for classic Ferrari, Porsche,Lambos, BMW, AUDI etc etc as some are currently unavailable, and it looks like Bosch are listening.. will