Speed difference between 25 and 28 tyres

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vjanda
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Speed difference between 25 and 28 tyres

Postby vjanda » Sun Jun 12, 2016 21:48 pm

Hi folks,
can anyone tell me what sort of speed gain if any I could expect by switching from 28c tyres inflated to 90psi to 25c 110psi?
I ride my 28s around 18mph on the flat at a medium pace.
Cheers :lol:

thecycleclinic
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Re: Speed difference between 25 and 28 tyres

Postby thecycleclinic » Sun Jun 12, 2016 22:12 pm

none on a smooth road on a rough road it will depend how rough the road is. in most cases no difference in speed will be noticed.
http://www.thecycleclinic.co.uk -wheel building and other stuff.

vjanda
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Re: Speed difference between 25 and 28 tyres

Postby vjanda » Sun Jun 12, 2016 22:17 pm

Thx, I guess I'll stick to my 28's and train more to get faster :)
It is beyond me how pro riders can ride 130k at 45k/h.
I can hardly hit 40 going bloody downhill.

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davidof
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Re: Speed difference between 25 and 28 tyres

Postby davidof » Mon Jun 13, 2016 20:48 pm

I have no idea but what I can tell you is there is a 1100m climb behind my house, largely 8-10% grades. My fastest ride up on 23mm tires took 1h02m on a carbon framed road bike. I rode it on a 1977 bike I got out of a skip with 28mm cheap Michelin tires and it took me 1h12m, I could probably have ridden it in 1h05m on that day on my carbon bike. So yeah, the tires probably don't make much difference, fractions of a minute.

vjanda
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Re: Speed difference between 25 and 28 tyres

Postby vjanda » Mon Jun 13, 2016 21:03 pm

Good to know.
I thought the higher pressure and lower rolling resistance of a 25 might gain me 5% but I guess I was wrong and too optimistic :)
Thanks

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Charlie Potatoes
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Re: Speed difference between 25 and 28 tyres

Postby Charlie Potatoes » Tue Jun 14, 2016 07:21 am

The truth, as I see it, is that nobody knows.
Although I have read some posts on this forum where you'd be forgiven for thinking otherwise.
"You really think you can burn off sugar with exercise?" downhill paul

vjanda
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Re: Speed difference between 25 and 28 tyres

Postby vjanda » Tue Jun 14, 2016 08:27 am

One thing is for sure, a lighter bike is a faster bike.
I recently sold my old mtb and got a sirrus pro that's about 8 lbs lighter. I recon I gained almost 2mph.
Next mission is to drop 8lbs of body fat :)

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Step83
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Re: Speed difference between 25 and 28 tyres

Postby Step83 » Tue Jun 14, 2016 08:48 am

Was going to say youll get to a point where all the bike weight saving in the world will make no odds. Its easier an cheaper to loose weight yourself than off the bike.

Regarding tyres don't forget tyre pressure comes into play as well, lower pressure will increase the contact patch with the ground giving greater traction to a point. Think how hard it is to ride on a low tyre, its about finding the sweet spot for your total weight with the bike and the tyre pressure.

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Singleton
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Re: Speed difference between 25 and 28 tyres

Postby Singleton » Tue Jun 14, 2016 09:07 am

It's not as simple as 25mm v 28mm tyres unfortunately.

There are many places on the web where you can get informaiton about rolling resistance of tyres. The current perceived wisdom is that wider tyres have a lower rolling resistance for the same pressure - but the actual figures vary by tyres and tubes.

Hours of reading here: http://www.bicyclerollingresistance.com

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Bobbinogs
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Re: Speed difference between 25 and 28 tyres

Postby Bobbinogs » Tue Jun 14, 2016 09:26 am

vjanda wrote:One thing is for sure, a lighter bike is a faster bike.
I recently sold my old mtb and got a sirrus pro that's about 8 lbs lighter. I recon I gained almost 2mph.
...


mmm, I think that 'evidence' neatly overlooks a whole heap of factors. As an example, if you wore a weighted running jacket of 8lbs I bet the Sirrus would still be faster than the MTB, maybe as much as 1.73mph faster (approx).

Fenix
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Re: Speed difference between 25 and 28 tyres

Postby Fenix » Tue Jun 14, 2016 10:30 am

Both of the pressures you mention are too high unless you're extremely heavy.

In the real world you'd not notice any difference between tyres. 5% is a huge amount.

vjanda
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Re: Speed difference between 25 and 28 tyres

Postby vjanda » Tue Jun 14, 2016 10:59 am

I'm 88kg

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drlodge
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Re: Speed difference between 25 and 28 tyres

Postby drlodge » Tue Jun 14, 2016 11:01 am

You'd likely see more of a difference moving to a better tyre, whatever that is. So depends on the tyres you're talking about...?
WyndyMilla Massive Attack | Rourke 953 | Condor Italia 531 Pro | Boardman CX Pro | DT Swiss RR440 Tubeless Wheels
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vjanda
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Re: Speed difference between 25 and 28 tyres

Postby vjanda » Tue Jun 14, 2016 11:09 am

I only got the Sirrus a couple of weeks ago.
It had a nasty heavy Chinese 28 and 35 on the front.
Decided to replace both with Michelin Pro 4 Endurance 28's for starters.
They will save me over 500g in weight alone.
Will report on any speed change in 2 weeks when I get them...

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redhanded
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Re: Speed difference between 25 and 28 tyres

Postby redhanded » Wed Jun 15, 2016 11:36 am

FWIW there is research indicating that narrower and higher pressure tyres aren't faster anyway.

They may FEEL faster as they have a harsher ride and you associate this with going faster, but this doesn't actually mean you are going faster.

https://janheine.wordpress.com/2016/06/ ... confirmed/

Carbonator

Re: Speed difference between 25 and 28 tyres

Postby Carbonator » Wed Jun 15, 2016 15:18 pm

Step83 wrote:Was going to say youll get to a point where all the bike weight saving in the world will make no odds. Its easier an cheaper to loose weight yourself than off the bike.



Really? If its so easy to lose weight then why are we an obese nation with a multi million pound weight loss industry?

It is way way easier to go out and buy a light bike lol.

Cheaper is not really a thing, as if you lose weight you will probably want a light bike all the more, and then there is all the new clothes that you will have to buy!

An 8lb lighter bike will feel much better and more noticable than losing 8lb in bodyweight IME.
The best solution is to do both of course (if you are overweight).

It depends what bodyweight you are losing the 8lb from though of course.

Basically the goal is to be not overweight, and ride a light (well specced) bike.
Its not one v the other, its both!

And leave the financials out of the equation.
If you cannot or (more likely) do not want to spend the money, then just don't.
Bitching about it just to make yourself feel better about spending your money on other things is v sad.

Carbonator

Re: Speed difference between 25 and 28 tyres

Postby Carbonator » Wed Jun 15, 2016 15:34 pm

vjanda wrote:Hi folks,
can anyone tell me what sort of speed gain if any I could expect by switching from 28c tyres to 25c ?

Cheers :lol:


All things being equal it will be almost exactly the same as the difference between 25c and 23c.

Looking to quantify speed gains is a loosing battle (especially on here).

Just get the nicest quality kit that looks good, feels good, and then enjoy riding your bike.

Any speed gains will be a nice bonus that you may never be able to quantify, but if you do, keep it to yourself :wink:

Simon Masterson
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Re: Speed difference between 25 and 28 tyres

Postby Simon Masterson » Wed Jun 15, 2016 18:41 pm

It matters far more that you have the right tyre for your rim, but a perfectly matched combination of 23mm rim and 23mm tyre is not going to give you any benefit easily measurable without a stopwatch. I like wide tyres on the road, and I'd probably try them for TTs if I had wider rims (and clearances allowed). The training tyres I use on my TT bike are 20mm and sluggish, so it's not just the width - it matters far more that you use good tyres, and latex tubes.

Kajjal
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Re: Speed difference between 25 and 28 tyres

Postby Kajjal » Wed Jun 15, 2016 20:51 pm

I found 25mm tyres better but do weigh 100kg. A more noticeable improvement was moving from cheap to good quality tyres. I currently have 30mm tyres on as i go off road a fair bit and need the extra grip. They are smoother on road but a little slower up hill.

vjanda
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Re: Speed difference between 25 and 28 tyres

Postby vjanda » Wed Jun 15, 2016 21:16 pm

I hope I made the right choice with the Michelin Pro 4 Endurance.
I was told they offer good protection while still rolling well.
Can't wait to try them out.


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