anybody go to 28mm tires, and NOT like the switch?

Discuss light weight issues concerning road bikes & parts.
Marin
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by Marin

addictR1 wrote:
Thu Mar 28, 2019 10:21 pm
Does plush = slower?
In the case of GP4000 vs. 5000, plusher means faster. Everyone reports the 5000 rides much better, yet it measures quite a bit faster than the older tire.

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Marin
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by Marin

AJS914 wrote:
Fri Mar 29, 2019 1:09 am
BRR isn't showing much penalty to going wider at a lower pressure.

https://www.bicyclerollingresistance.co ... son#drop15
This seems to be a constant source of confusion: A wider tire at is HARDER at the same pressure, so it will provide the same level of comfort / suspension at a LOWER pressure. If you measure at a the same drop (i.e. level of comfort) wide and narrow tires have similar rolling resistance.

The difference is that on a wider tire you have more travel to blow through before you hit the rim, in exchange for a weight and aero penalty. You can run the at even lower pressure with a lower risk of pinching, but then the wider tire will be slower than the narrow on in rolling resistance too.

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Beaver
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by Beaver

...and never forget the surface you are riding on. These lab tests on smooth surfaces equal perfect tarmac - here the narrower tire may excel a bit.

But on rough surfaces even a plush tire may be faster:

Image
https://blog.silca.cc/part-4b-rolling-r ... -impedance

Marin
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by Marin

Plush mostly means tire pressure though. The "rough" surface Josh tested on was *extremely* rough BTW, nothing you would include in a normal road bike ride.

For normal Asphalt, pressures we would deem too high(110 PSI!) still resulted in lower rolling resistance. However, I still prefer lower pressure, but I also prefer tires that still roll well when soft. I rode to the office on 1.9 bars today - on 48mm tires :D

guyc
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by guyc

Nope - I'm running 28mm Turbo Cottons. For the roads I ride on they're absolutely superb.

Mr.Gib
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by Mr.Gib

Beaver wrote:
Fri Mar 29, 2019 12:21 pm
...and never forget the surface you are riding on. These lab tests on smooth surfaces equal perfect tarmac - here the narrower tire may excel a bit.

But on rough surfaces even a plush tire may be faster:

Image
https://blog.silca.cc/part-4b-rolling-r ... -impedance
The yellow line will be of most interest to many riders. The gains from 60 psi to 100 psi are incredibly small on a medium-poor surface. IIRC the yellow line approximates chipseal. The redline re-inforces what a roll down test on gravel showed: that softer was always faster until it was almost flat.
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addictR1
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by addictR1

Well I’m running tubular.. and once my veloflex sprinters wears out, gonna put veloflex Carbon 23 front and arenberg 25 rear.

I’m 160lbs was 145 before last winter.. :(

So what PSI should I run? I usually pump 100 and 110-115 rear on my sprinters.


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ms6073
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by ms6073

Even at your winter weight of 165, I would think 90-95 psi should be sufficient for tubulars.
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RocketRacing
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by RocketRacing

The key with the silca data is to remember the weight it is calculated for. Scale those numbers up or down based on your weight. For me, 110 psi turns into 80 or so psi.

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C36
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by C36

Has any other study been conducted on the topic?
I for sure know that Michelin did test tires over different surfaces for like forever (the axial at least) but never recall anything published confirming silca “blog” whom science appeared very doubtful at times (recall the wheel/tire vertical stiffness that had little solid ground)


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ChiZ01
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by ChiZ01

28mm will have less rolling resistance but 25mm will be more aero on most rims, unless you go super wide like Enve 4.5 AR

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wheelsONfire
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by wheelsONfire

Tire pressures are an interesting topic. But i wonder, if you check your weight distribution on your bike with your typical pose.
You will notice the weight could be like 30/70, 40/60 or somthing like that.
I would guess, this is how much we load front and rear tires to.
I never see anyone taking this into account. Why not?
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nachetetm
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by nachetetm

I find amusing the arguments that some people use to justify that their choice of tire size under their very own circumstances is "the best and fastest" in every single condition. It's like if tarmac condition, rider weight, bicycle used, tire model, tire pressure and many other variants were irrelevant, and it is not. In fact all those factors are more important than the labeled tire width. It would be refreshing to see people dropping those "25mm tires are the fastest, period" comments. We have been through this with 23mm and with 21mm tires, and it has been proven wrong in both cases.

My only suggestion to the OP is "try 28mm, and if you don't like it go back to 25". But I don't see any reason to not to try it. The 30g weight penalty I am sure it is irrelevant and the extra "softness" that some people dislike can be corrected adding a bit more air to the tire. The only reason not to try wider tires is bike clearance. But there are several benefits to go wider, and many of them have been listed already in the thread.

RocketRacing
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by RocketRacing

C36 wrote:
Sat Mar 30, 2019 3:00 am
Has any other study been conducted on the topic?
I for sure know that Michelin did test tires over different surfaces for like forever (the axial at least) but never recall anything published confirming silca “blog” whom science appeared very doubtful at times (recall the wheel/tire vertical stiffness that had little solid ground)


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Tom anhault came up with the same findings independantly. Also... the guys on mountain bikes intuitively have known the same data without actual formally studying it... forever. To a lesser degree, same with race car drivers (but that is a bit different, but “higher is fastest, or lowest is fastest” is the reality they discovered is not true). The rougher the surface, the lower the pressures... the faster you are. But not too low. The trick is to find that sweet spot for every rider/condition.

What is the fastest tire/wheel combo? It is influenced by many factors:
- Wheel weight
- wheel shape (aero)
- mounted tire width
- tire pressure
- tire pressure effects mounted width
- tire width effects aero performance (too wide is bad)
- tire construction (rolling resistance)
- road surface (how rough)

The silca “blog” is worth the read... i say it is essential reading. As is the related “marginal gains podcast.” Josh was a big part of the zipp wheel development process. He also has been and advisor for many pro tour teams (currently EF, prevously with bora/sagan, wiggins 1hr record, etc). When the smartest person in the room speaks, we become smarter by listening.

Also, check out slowtwitch, as it is full of people in competition, many of whom are on the cutting edge of “best practices”. I was learning about tire pressures over there (pre reading the five part silca articles on the topic)... and i started quoting bike rolling resistance numbers (good source, but does not take into account impedance losses from rough surfaces), and someone basically told me... “keep your pressures up if you wish, i just hope you are conpeting in my age group.”

Campervan
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by Campervan

spdntrxi wrote:
Thu Mar 28, 2019 3:27 pm
my 28's are schwalbe pro ones... normally I ride turbo cotton in 24 and 26. You can feel the difference easy..it's plush. Nothing like my WTB Byways @ 650x47..but still.
Would you think the 28 Schwalbe pro one's (tubeless) would be much more comfy than a S-works turbo 26mm?
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by Weenie


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