Bike Roll-out tests in Gunnislake

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al_yrpal
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Re: Bike Roll-out tests in Gunnislake

Postby al_yrpal » 25 Jan 2011, 4:50pm

Mick
Keep going and ignore the knockers. Now you know what its like to be an engineer!

It would be interesting to see what wide tyres did to the Mercian. Sidewall stiffness is a big factor too.

Al
Last edited by al_yrpal on 25 Jan 2011, 5:53pm, edited 1 time in total.
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Mick F
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Re: Bike Roll-out tests in Gunnislake

Postby Mick F » 25 Jan 2011, 4:52pm

Tell you what, when I've done the next experiment with the 25mm - actually 22mm - Nutraks to see if there's any difference, I'll play with the pressure. Trouble is, that will have to be another day, as the only gauge I have is on my track pump. Pressures on my 20mm are 120/100psi and when I had 23mm, I had them the same. The Nutraks state 100psi on the sidewalls.

I'll have to go to the station in the car. Does it matter what bike I use? Barbarella is sitting there ready and waiting with her Michelin World Tours. BTW I inflated her's quite hard for her test - 80psi rear and 60psi front. I could check her roll-out again, then reduce pressure in 10psi steps. As I say, another day.
Mick F. Cornwall

reohn2
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Re: Bike Roll-out tests in Gunnislake

Postby reohn2 » 25 Jan 2011, 4:54pm

Mick F wrote:Of course I could do all the tests again using different tyre pressures ............... but I won't.


IMHO unless you do, the tests aren't worth a hoot,to compare the Nutrak's to the Rubino's isn't going to prove anything.
I'm sorry to pour cold water on the tests you've carried out but I'm left wondering what will be proven by comparing say the RSW16's small diameter balloon tyres to the very large diameter 20mm Rubino Pro's fitted to the Mercian :?
To prove anything at all it would need tyres of the same make and type in differing sizes for a given diameter,on the same bike and with the same wheels in very similar conditions,each tyre would need to be tested at varying pressures,perhaps even from the sublime to the ridiculous to obtain any kind of true comparison.
At the very least,as any kind of minimum test, as Ersakus says you would need to find the optimum tyre pressures for each comparable tyre to reach any kind of worthwhile comparison and conclusion at all.
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reohn2
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Re: Bike Roll-out tests in Gunnislake

Postby reohn2 » 25 Jan 2011, 5:01pm

BigG wrote:Just to comment that the width of the tyre as reported by MickF above depends on the width of the rim as well as the structure of the tyre.

Thats correct.
I always believed that the ERTO rating on the tyre referred to its height (and thus the wheel diameter), not its width. Am I wrong?

No you're quite right.
FWIW if I do measure tyres (inflate on the rim) I always measure both height and width even though it is height that matters most.

Of course, the two are related as the cross section of the tyre/rim combination will tend towards a circle when under pressure.

Yep right again!
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Re: Bike Roll-out tests in Gunnislake

Postby reohn2 » 25 Jan 2011, 5:08pm

al_yrpal wrote: ...........It would be interesting to see what wide tyres did to the Mercian. Sidewalk stiffness is a big factor too.
Al


I suspect you mean sidewall stiffness,in which case its bound to have an effect,it also has great effect on comfort too and tyre pressures.
Thats why I don't think Micks tests are of any use so far until he carries out further tests with like for like tyres in varying sizes on the same bike.
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squeaker
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Re: Bike Roll-out tests in Gunnislake

Postby squeaker » 25 Jan 2011, 5:16pm

ersakus wrote:The idea is the bump losses are minimised at optimum pressure and wheels roll better.
But just how 'bumpy' is Gunnislake station car park (the bit with all the chalk marks and orange paint on it...)? :roll:
Schwalbe say that higher pressure is faster on a smooth surface, but slower on a rough one: I thought that was widely recognised? Roads usually have some roughness, varying from 'very smooth' to 'potholed rough chippings on distorted asphalt', so first pick your surface.
"42"

geocycle
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Re: Bike Roll-out tests in Gunnislake

Postby geocycle » 25 Jan 2011, 5:30pm

reohn2 wrote:
al_yrpal wrote: ...........It would be interesting to see what wide tyres did to the Mercian. Sidewalk stiffness is a big factor too.
Al


I suspect you mean sidewall stiffness,in which case its bound to have an effect,it also has great effect on comfort too and tyre pressures.
Thats why I don't think Micks tests are of any use so far until he carries out further tests with like for like tyres in varying sizes on the same bike.


Well he has shown a first order relationship that a heavy poorly-aerodynamic bike with small wheels rolls less well than a light aerodynamic one wiith larger wheels (and that wheel quality on his mercian probably make very little difference in this kind of test). Whether this is wheel size, weight or aerodynamics is not proven. In my view tyre properties are secondary at this scale of difference.

An experiment using stepped tyre pressure tests on the same bike could work if the means and SDs are recorded accurately.

More simply, what about adding 10kg to the mercian - how much shorter will he finish, more or less than the RSW16?

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Re: Bike Roll-out tests in Gunnislake

Postby PBA » 25 Jan 2011, 5:31pm

Mick,
Have considered getting another cyclist involved? It seems to me that someone with, say, a tourer would be able to contribute wider tyre data and presumably a different body mass as well.

One thing not being investigated of course is the way in which power is transmitted to the road. There is discussion of bump losses above but these must surely be greater at reducing the amount of power reaching the road rather than effecting the rolling ability of the bike?

Either way - good effort. Regardless of the validity of the results, you deserve credit for actually getting out and making the attempt.

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hubgearfreak
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Re: Bike Roll-out tests in Gunnislake

Postby hubgearfreak » 25 Jan 2011, 5:48pm

Mick F wrote:The figures and method wouldn't stand up to scientific analysis, but so what?


that's just it :D

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al_yrpal
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Re: Bike Roll-out tests in Gunnislake

Postby al_yrpal » 25 Jan 2011, 6:03pm

I think Mick has conclusivly proved that Mercians roll better than lesser bikes for a start. As for position and air drag, they are irrelavent because its overall bike performance that we are all actually interested in.

From there you can move onto tyres, tyre pressures etc to find out if these substantially alter results . (I can't help think Mick has started something he may come to regret!)

I know this much, I can outpace light people on lighter bikes downhill substantially and my momentum will carry me considerably further on any following uphill stretch. That is before they glide effortlessly past me when they eventually overtake. :cry:

Al
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Re: Bike Roll-out tests in Gunnislake

Postby herzog » 25 Jan 2011, 7:11pm

hubgearfreak wrote:
Mick F wrote:The figures and method wouldn't stand up to scientific analysis, but so what?


that's just it :D


Why wouldn't they? What kind of scientific analysis are you thinking of?

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Re: Bike Roll-out tests in Gunnislake

Postby Malaconotus » 25 Jan 2011, 7:15pm

geocycle wrote:More simply, what about adding 10kg to the mercian - how much shorter will he finish, more or less than the RSW16?


I'll wager adding 10Kg will make the Mercian go further, not shorter at all.

Graham

reohn2
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Re: Bike Roll-out tests in Gunnislake

Postby reohn2 » 25 Jan 2011, 7:31pm

al_yrpal wrote:.......... its overall bike performance that we are all actually interested in..........
Al


Really I thought it all about tyre prefomance which began with Mick being fed up with people not agreeing with his assumptions that his very narrow tyres were faster than wider varieties,so he then lent a forum member his 23mm R/Pro's for him to compare.
When it turned out that he had compared 23mm with another make of 23mm tyre (Gatorskins I think) and found that the Pro's were a little better we were no further on.
Then we got into the comparison tests which Mick carried out,which has only proved what most folks already suspected, that the Mercian would roll further than the other bikes.
If Mick wishes to prove anything at all it needs for the same tests to be carried out with the same bike running the same tyres in a variety of sections ie; Rubino Pro's in 700C x 20/23/25/28mm. Tests upto now have been like poking a stick in a dark place at midnight whilst wearing a blind fold! or in other words because of the vast difference in machinery,wheel diameters, tyres and tyre pressures, the tests prove nowt!
It doesn't really matter which bike the tests are carried out on so long as they are carried out on the same bike with the same tyres in a variety of sections of that tyre,and a variety of tyre pressures,then,on a roll test atleast,some conclusions can be drawn.
I can understand that Mick doesn't wish to go to the considerable time and expense of such tests, but that is the only way anything can be concluded IMO.
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Freddie
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Re: Bike Roll-out tests in Gunnislake

Postby Freddie » 25 Jan 2011, 7:49pm

Then there's the question of whether rolling down a hill onto a flat has much to do with anything, anyway.

reohn2
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Re: Bike Roll-out tests in Gunnislake

Postby reohn2 » 25 Jan 2011, 8:00pm

Freddie wrote:Then there's the question of whether rolling down a hill onto a flat has much to do with anything, anyway.


Agreed!
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