Who rides 28mm + tires on tarmac?

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

I go back and forth between 25mm, 28mm and 32mm with butyl and latex tubes. Experimenting with different wheels on race bike and on steel endurance bike. I can tell you that 28mm GP4000S with latex tube at 60 psi is the fastest combination, even on narrow wheel (e.g. 22mm wide) with a tire that measure ~30mm wide. It’s not because I feel faster, it’s because I see more PR’s.
If you think that wider tire is slowing you down, it’s all in your head. Rolling resistance of wider tire trumps ~4 aero watts.
Racing is a three-dimensional high-speed chess game, involving hundreds of pieces on the board.

:arrow: CBA = Chronic Bike Addiction
:arrow: OCD = Obsessive Cycling Disorder

by Weenie


zefs
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Joined: Sat Aug 05, 2017 8:40 pm

by zefs

No way 28mm at 60 psi is faster than 25mm. At that low pressure you can feel the tire dragging a lot. I had been testing them on smooth tarmac with same conditions and the effort was harder compared to 25mm, it was visible on the heart rate readings (no it wasn't fatigue) at same speeds.
The difference was about 2km/h or so at 35km/h speeds. I was using 20 psi less on 28mm (80 psi) which on tests is on par with 25mm (100 psi).

If you use an optimal combo with aero wheels and pump them to maximum psi they could be faster but my guess is they would feel rough since they are less supple.

If not racing sure you can use the benefits of them but they are not both comfortable and faster, only more comfortable, at 60 psi your really don't feel road bumps at all.

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mpulsiv
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by mpulsiv

zefs wrote:No way 28mm at 60 psi is faster than 25mm. At that low pressure you can feel the tire dragging a lot. I had been testing them on smooth tarmac with same conditions and the effort was harder compared to 25mm, it was visible on the heart rate readings (no it wasn't fatigue) at same speeds.
The difference was about 2km/h or so at 35km/h speeds. I was using 20 psi less on 28mm (80 psi) which on tests is on par with 25mm (100 psi).

If you use an optimal combo with aero wheels and pump them to maximum psi they could be faster but my guess is they would feel rough since they are less supple.

If not racing sure you can use the benefits of them but they are not both comfortable and faster, only more comfortable, at 60 psi your really don't feel road bumps at all.
If you ride 25mm tires at 100 psi, I feel sorry for you.
Narrow overinflated tires confuse psychology with reality.
Racing is a three-dimensional high-speed chess game, involving hundreds of pieces on the board.

:arrow: CBA = Chronic Bike Addiction
:arrow: OCD = Obsessive Cycling Disorder

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wheelsONfire
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Location: NorthEU

by wheelsONfire

A dealer told me almost all custom bikes they sell is 25mm. Some 23mm. But never 28mm.
Perhaps it's due to good tarmac. I don't know.
I've been on 23mm and now i have 25mm on one wheelset and 25 rear and 23 front on another.
The front is smoother (Veloflex carbon) rear is Maxxis Campione.
The latter holds air way better + puncture protection works better.
The other set is Schwalbe S-One 24-25mm (now discontinued).
Best all around is probably S-One.
Bikes:

Ax Lightness Vial EVO Race (2018.12.21)
viewtopic.php?f=10&t=156137
Paduano Racing Fidia (kind of shelved)
Open *UP* (2016.04.14)


Ex bike; Vial EVO D

jlok
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Joined: Tue Jun 30, 2015 3:30 am

by jlok

My friends were surprised by my use of 60psi with 28c tire on wide 25mm int width rim. It's plenty supportive and no squirm feeling even when going fast down hill. Point being that talking about psi without knowing the volume is meaningless. You will know when you count how many pumps to make it to 60psi with a 28c on wide rim.
Litespeed T1sl Disc / BMC TM02 < Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

zefs
Posts: 438
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

mpulsiv wrote:
Sun Sep 30, 2018 8:28 am
zefs wrote:No way 28mm at 60 psi is faster than 25mm. At that low pressure you can feel the tire dragging a lot. I had been testing them on smooth tarmac with same conditions and the effort was harder compared to 25mm, it was visible on the heart rate readings (no it wasn't fatigue) at same speeds.
The difference was about 2km/h or so at 35km/h speeds. I was using 20 psi less on 28mm (80 psi) which on tests is on par with 25mm (100 psi).

If you use an optimal combo with aero wheels and pump them to maximum psi they could be faster but my guess is they would feel rough since they are less supple.

If not racing sure you can use the benefits of them but they are not both comfortable and faster, only more comfortable, at 60 psi your really don't feel road bumps at all.
If you ride 25mm tires at 100 psi, I feel sorry for you.
Narrow overinflated tires confuse psychology with reality.
I was when doing the tests, now I use 80-90 but on tubeless. Anything less and the speed loss is noticeable.
Thing is, why are you using 60psi? are you riding on worst possible roads or you just like the feel of them?

I am sure there are a lot of riders using lower psi to gain comfort because they can't get comfortable on their bike but usually it's because of not optimal bike fit...myself included. Since I improved my fit I stopped using lower pressures which I thought I had to.

scale29
Posts: 125
Joined: Sat Jun 04, 2011 5:40 pm

by scale29

65 Psi in a 28 (that measures 30 on rim) is equal to around 80psi in a 25c and about 90psi in a 23mm.

I'm 85kg and run 65-70psi rear and 60-65psi front, there's no fold or flop, and they feel fast. I used to run 85 in 25c and 100 in 23c.

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mpulsiv
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by mpulsiv

zefs wrote:
mpulsiv wrote:
Sun Sep 30, 2018 8:28 am
zefs wrote:No way 28mm at 60 psi is faster than 25mm. At that low pressure you can feel the tire dragging a lot. I had been testing them on smooth tarmac with same conditions and the effort was harder compared to 25mm, it was visible on the heart rate readings (no it wasn't fatigue) at same speeds.
The difference was about 2km/h or so at 35km/h speeds. I was using 20 psi less on 28mm (80 psi) which on tests is on par with 25mm (100 psi).

If you use an optimal combo with aero wheels and pump them to maximum psi they could be faster but my guess is they would feel rough since they are less supple.

If not racing sure you can use the benefits of them but they are not both comfortable and faster, only more comfortable, at 60 psi your really don't feel road bumps at all.
If you ride 25mm tires at 100 psi, I feel sorry for you.
Narrow overinflated tires confuse psychology with reality.
I was when doing the tests, now I use 80-90 but on tubeless. Anything less and the speed loss is noticeable.
Thing is, why are you using 60psi? are you riding on worst possible roads or you just like the feel of them?

I am sure there are a lot of riders using lower psi to gain comfort because they can't get comfortable on their bike but usually it's because of not optimal bike fit...myself included. Since I improved my fit I stopped using lower pressures which I thought I had to.
As Jlok mentioned above. It’s all about the volume of a tire, not psi. I just find it amusing the stubbornness of riders who frown upon wide tires and low tire pressure, especially to those who don’t race. Worry about floppy jersey, flexibility, sloppy and misaligned pedal stroke, rocking hips due to saddle height.
Racing is a three-dimensional high-speed chess game, involving hundreds of pieces on the board.

:arrow: CBA = Chronic Bike Addiction
:arrow: OCD = Obsessive Cycling Disorder

Mr.Gib
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Location: eh?

by Mr.Gib

This is an interesting discussion that has a data problem.

We just don't know the effect on rolling resistance of different surfaces at various pressures. On a very smooth surface we do know that higher pressures will be faster. What we don't know is how rough the surface has to be in order to be faster (or the same) at 90, 80, 60 psi etc. There have been roll down tests on gravel that showed that softer was almost always faster, but I am unaware of anything similar on various finished road surfaces. You would literally need to create a road on a hill, divide it into strips, and finish each strip with a different surface.

There is a second factor - internal rim width that also needs to be tested. What has lower rolling resistance - 28mm tire on 17mm internal or 22 mm internal rim? As part of my experiments to eliminate road buzz I have tested these combinations at 65 psi. I have no idea which is faster (seat of the pants felt the wider rim was faster) but what I do know is that that handling/cornering on the wide rim was massively superior on all surfaces including glass smooth. While descending, the grip, line control, and general confidence was mindblowing. On the narrow rim, the tire distortion made it a touch sketchy in some corners.

The difference was so dramatic that I think much of the industry is missing the boat. Yes wheel/tire combos have gotten wider but there is so much more to be gained. Those of you who think that 25 mm on 17 - 19 internal rim at 80 - 100 psi is perfect handling, I strongly urge you to reserve your judgement until you have spent serious time riding 28 - 30 mm at 60 - 70 psi on rims of at leas 20 mm internal width.

My final thought is that all this talk of massive rubber means you guys must all be on discs. It's a shame that superlight race frames with rim brakes cannot accomodate tires that measure 30 - 32 mm. In fact the majority of real race bikes, disc or otherwise, are limited to 28 mm between the chain stays.

jlok- what rim are you using that has 25mm internal measure?
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

morganb
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Joined: Wed Mar 15, 2017 5:30 pm

by morganb

I've run Open Corsa 28s on 21mm rims on my Tarmacs (both rim brake) and its superb. Actually width is just under 31mm.

jlok
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by jlok

@Mr.Gib Enve 4.5 AR Disc

The first ride was as dramatic as the feeling of first riding Domane, like a magic carpet.
Litespeed T1sl Disc / BMC TM02 < Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

CarlosFerreiro
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Location: Shetland, Scotland

by CarlosFerreiro

Mr.Gib wrote:
Sun Sep 30, 2018 4:56 pm
We just don't know the effect on rolling resistance of different surfaces at various pressures. On a very smooth surface we do know that higher pressures will be faster. What we don't know is how rough the surface has to be in order to be faster (or the same) at 90, 80, 60 psi etc. There have been roll down tests on gravel that showed that softer was almost always faster, but I am unaware of anything similar on various finished road surfaces.
There is this Silca blog post looking at different surfaces.
https://silca.cc/blogs/journal/part-4b- ... -impedance

zefs
Posts: 438
Joined: Sat Aug 05, 2017 8:40 pm

by zefs

Better handling and cornering speed making you faster does not mean wider tires are faster on straight road. How many times do you corner fast compared to going straight on the course of a ride? Also how many times do you hit cobble like sections which is were wider tires with lower pressures are faster?

There are diminishing returns based on tests done about wider tires, thing is people confuse the optimal tire size suggestion by manufacturers with actual measurement on their rims.

Lastly the wider the rim the less the max air pressure (given by manufacturer) you have to use for safety reasons = intended for road and gravel roads (which is why the wider rims were made).

Mr.Gib
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by Mr.Gib

zefs wrote:
Sun Sep 30, 2018 5:59 pm
Better handling and cornering speed making you faster does not mean wider tires are faster on straight road. How many times do you corner fast compared to going straight on the course of a ride? Also how many times do you hit cobble like sections which is were wider tires with lower pressures are faster?
This is assumed, and if you are racing this matters. Of course where you are racing is a factor as well. And don't forget all these big tires and rim add weight.

But still, it would be nice to get closer to the right answer to the question: if you are not racing, then what tire/rim choice is best?
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Mr.Gib
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Location: eh?

by Mr.Gib

CarlosFerreiro wrote:
Sun Sep 30, 2018 5:30 pm
Mr.Gib wrote:
Sun Sep 30, 2018 4:56 pm
We just don't know the effect on rolling resistance of different surfaces at various pressures. On a very smooth surface we do know that higher pressures will be faster. What we don't know is how rough the surface has to be in order to be faster (or the same) at 90, 80, 60 psi etc. There have been roll down tests on gravel that showed that softer was almost always faster, but I am unaware of anything similar on various finished road surfaces.
There is this Silca blog post looking at different surfaces.
https://silca.cc/blogs/journal/part-4b- ... -impedance
Thanks for this. This study loosely confirms the impressions of some of us. Even on good surfaces, very little is gained as pressures rise from 60 psi to about 110 psi, but then rolling resistance starts to increase quite dramatically as pressures rise beyond 110.

So very low pressures can be almost as fast on good surfaces and faster on bad surfaces but do they handle well? I say no unless they are mounted on wide rims.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

by Weenie


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