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by mullinsm
13 Mar 2018, 3:06pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

elPedro666 wrote:
mullinsm wrote:If you want a comfy ride, try 28mm tyres and you WILL get it; if you want to go faster try 23mm and you WILL go faster.

Can someone please close this thread now before Stephen Hawkins gets involved?


An appearance by the great man really would make my year!

Just a note on the statement above with regard to going faster: World Tour teams are now almost exclusively using 25 to 28mm - including 27mm on TT bikes (annoyingly I forget which team I saw those on) - fitted to wide rims. Pretty sure going faster is all they're into so without wishing to sound overly blunt, you're completely at odds with their thinking...

I'm a trendy consumer. Just look at my stupid phone.


Funnily enough, I don't take drugs either.....
by mullinsm
13 Mar 2018, 11:04am
Forum: Bikes & Bits – Technical section
Topic: Marathon Supreme wired
Replies: 6
Views: 588

Re: Marathon Supreme wired

simonhill wrote:That looks like the old version on SPA website.

Out of interest do the wired have tougher sidewalls? I've been running folding Supremes for a few years and like them, but am always worried about their fragile sidewalls. Ruined an otherwise good tyre by sliding down a pothole - part of sidewall removed.


I used to use Supremes but switched to the cheaper, standard tyre with Greenguard after tearing a hole in one on a towpath in France a couple of years ago. They roll well but I wouldn't trust them on anything but good tarmac after that. The standard tyre is a much tougher thing altogether and I've had no problems with them even on gravel roads in NZ.

I did find a use for the Supreme though - I cut a strip out of it which I now carry as a patch instead of a whole replacement tyre when touring.
by mullinsm
13 Mar 2018, 9:18am
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

Leeflatz wrote:Is there honestly that much difference between 25mm and 23mm tyres?
Been using 23s for years in all weather's, even on tracks and canal bank, no problem.
On these tracks you can manage as long as you don't sit on the bike like a sack of spuds.
Just wondering.
Does 2 mm make that much difference?
Bemused by all the debate I keep coming across.


In short and circumventing all the rather dull physics, no not much difference but some. Bigger tyres are heavier and have more rolling resistance (in most real world scenarios) but tend to provide a better cushion as they have more air in at a lower pressure. If you want a comfy ride, try 28mm tyres and you WILL get it; if you want to go faster try 23mm and you WILL go faster.

Can someone please close this thread now before Stephen Hawkins gets involved?
by mullinsm
9 Mar 2018, 7:49am
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

foxyrider wrote:
Mr Evil wrote:A lot of unsubstantiated talk about the detriment to performance from the increased weight and drag. Let's put some numbers to that:

http://www.slowtwitch.com/Tech/Why_Wheel_Aerodynamics_Can_Outweigh_Wheel_Weight_and_Inertia_2106.html
http://www.biketechreview.com/index.php/reviews/wheels/63-wheel-performance

In summary, the effect of increased wheel weight is approximately nothing. Aerodynamic drag from the wheels is potentially more significant, but it's still small (and tyre width only contributes part of that). Even if you're a racer who cares about these things, the reduced rolling resistance and increased comfort of wider tyres may still be worth it. For normal folk there should be no contest - does it really make sense to use less comfortable tyres just because you're worried that your journey might be a couple of seconds slower?


But if I run lower pressures and fatter tyres it's like riding through porridge! I don't like riding through porridge. And you keep perpetuating the myth that narrow hard tyres are less comfortable to ride on - they are not, now if you factor in RW roads, maybe and only maybe, there might be an advantage running low and fat, we at least know the Pro's think so for stuff like Roubaix. But generally they are on 22c tubulars so clearly riding for 200 plus kilometres at a time can't be so bad on narrow tyres.

On a blind test I reckon I can identify tyre widths fairly consistently just from how they ride. And with the aid of technology I can tell everyone that on a similar ride I need to put out 25-50w more on the bike shod with 28c than I do on the 23c's. Some of that is bike weight but as apparently that makes no difference I can only put the extra effort down to the tyres.

At the end of the day, who cares? I ride what I like, you ride what you like and we're all happy bunnies!


What he said.
by mullinsm
8 Mar 2018, 5:20pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

There are clearly more physicists on this forum than cyclists........
by mullinsm
8 Mar 2018, 4:16pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

Keezx wrote:I think you got my point. :wink:
On a hilly course 5 kg makes a difference , but 120 grams in the wheels, really?
All over the world people are brainwashed about wheel weights, 1400 grams are light and 1800 grams are boat anchors.
For me it's not much more than fetishism.


I know which ones I'd rather do 100 miles on....
by mullinsm
8 Mar 2018, 4:16pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

Mick F wrote:
Keezx wrote:Weight does matter a little bit when accelerating but nothing noticable for your average speed.

Are you saying that a heavy bike has the same average speed as a light bike when moving?
If so, you're ignoring hills. :wink:


And not only hills. The idea that a heavy bike is just as fast as a light bike on the flat is just plain wrong. Certainly the difference is more noticeable on hills, but anyone who has ever toured on a heavy bike knows that, even on the flat, you know you're carrying.
by mullinsm
8 Mar 2018, 3:09pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

Keezx wrote:
mullinsm wrote:
Keezx wrote:IF you compare 2 tyre sizes, then you should use tyres with comparable construction/carcass/thread, otherwise it's useless.


The 23,25 and 28mm were all Conti Gatorskins. The only difference apart from the size was the weight. Rolling resistance theory says the 28mm should be quicker on the roads in question, but they aren't. I suspect the difference therefore is the weight and I imagine that the extra 60g between the 25s and the 28s makes as much difference as the 60g difference between good wheels and very good wheels.


Weight does matter a little bit when accelerating but nothing noticable for your average speed.
No way 60 gr./wheel would have any significanty influence, the tyre width does matter for air resistance though.
My guess is you sit also a bit more aerodynamic on the faster bike.

PS 1 thing which isn't even mentioned here is the fact that the rim inner width influences the tyre width, contact patch and riding properties significant.
Food for thought:
https://intheknowcycling.com/2016/04/03 ... eel-sizes/
I don't bother anymore about 23 mm or 25 mm , take what I can find for a good price, put them om 18C or 19C rims and pump 5-6 Bar depending on the expected road surface.


With all due respect, that's simply incorrect.
by mullinsm
8 Mar 2018, 1:39pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

Keezx wrote:IF you compare 2 tyre sizes, then you should use tyres with comparable construction/carcass/thread, otherwise it's useless.


The 23,25 and 28mm were all Conti Gatorskins. The only difference apart from the size was the weight. Rolling resistance theory says the 28mm should be quicker on the roads in question, but they aren't. I suspect the difference therefore is the weight and I imagine that the extra 60g between the 25s and the 28s makes as much difference as the 60g difference between good wheels and very good wheels.
by mullinsm
8 Mar 2018, 12:11pm
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

I understand the science says that rolling resistance improves with bigger tyres on rough roads, but my experience doesn't support the theory. I have a carbon bike with Mavic wheels and 23mm tyres and when I swap them for 25mm tyres, it is noticeably and measurably slower and that is on minor roads in North Norfolk which aren't smooth by any stretch of the imagination.

I have ridden bikes of similar weight with 25mm and 28mm tyres on and the 28mm is noticeably and measurably slower but is significantly more comfortable.

I have a 700c touring bike with 32mm tyres that weighs 15kg and a 26" tourer with 50mm tyres that weighs exactly the same and the 26" is noticeably and measurably slower by as much as 10% or more.

The common factor is the weight of the wheels and on a long tour, I don't spend too much time accelerating as it's mostly grinding out the miles.

Quad erat demonstrandum.......
by mullinsm
8 Mar 2018, 8:35am
Forum: Bikes & Bits – Technical section
Topic: 25mm tyres
Replies: 86
Views: 7765

Re: 25mm tyres

In my experience, nothing effects the performance of a bike more than the weight of the wheels and smaller tyres will weigh less than larger tyres of the same make and model.
by mullinsm
6 Mar 2018, 3:13pm
Forum: Bikes & Bits – Technical section
Topic: Brake and STI compatability
Replies: 6
Views: 856

Re: Brake and STI compatability

This is a problem I've dealt with over the years and I've found that the Avid Ultimate Shorties are the best with STI levers for touring (see my post on the Thorn Sherpa for more details. Mini V brakes work well, but the clearance can be an issue with mudguards. I've used them with tires up to 35mm without guards and you could probably get away with guards on 28mm tyres OK. The Avids are better though if you can stretch to the (ridiculous) cost.

You could also go for full size V brakes and use a Travel Agent to alter the cable pull, but you're getting to the same price as the Avids then.
by mullinsm
6 Mar 2018, 3:08pm
Forum: Bikes & Bits – Technical section
Topic: Thorn Sherpa
Replies: 11
Views: 1933

Re: Thorn Sherpa

reohn2 wrote:What size is the bike in the photos?


It's a 565s. I'm 5'11" and it's a perfect fit with a 10cm stem.
by mullinsm
6 Mar 2018, 2:21pm
Forum: Bikes & Bits – Technical section
Topic: Thorn Sherpa
Replies: 11
Views: 1933

Re: Thorn Sherpa

mercalia wrote:what is Thorns thinking in haveing long steerers/tubes above the top tube? seems to be the norm? or is it just buyers buying a small frame then not able to cut down the steerer? Is there any advantage to a small frame and along steerer? In my case I have to get an extension tube with my Dawes 1-Down as they cut it all short


The first pic was taken before I'd settled on a bar height I was comfortable with. I eventually settled on 2 10mm spacers and cut some more off the steerer. It may look odd having such a long head tube, but remember the wheels are 26", not 700 and the geometry gives a lower stand over height which is helpful when touring as you have to stop often to navigate (or just breath sometimes!). Despite the appearance though, the geometry really works as the bike is a joy to ride.

I also swapped the stem and the seatpost from the original build and went for a 35 degree Thomson Elite stem and Velo Orange layback seatpost as I didn't trust the carbon one on rough stuff.
by mullinsm
6 Mar 2018, 2:14pm
Forum: Bikes & Bits – Technical section
Topic: Thorn Sherpa
Replies: 11
Views: 1933

Re: Thorn Sherpa

Tiberius wrote:A nice purposeful looking bike there....Nice.

I would want mudguards...did you ever miss them ??


I have fitted mudguards for commuting but I removed them for the trip to NZ as they are apt to get damaged on the plane and with a tent on the rack, you don't get any spray from the rear wheel anyway. You do get wet feet, but in NZ that's pretty much guaranteed as when it rains, it really rains!