What pressures are you running your 28mm's at?

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Pierre86
Posts: 25
Joined: Mon May 13, 2019 3:53 pm

by Pierre86

backdoor wrote:
Tue Aug 06, 2019 5:57 am
85-86kg here and running 28mm Grand Sports on a set of 25mm wide Belgium+ rims. Th wider rims make a difference.

I run them at 85psi front, 90psi rear. Mostly run on chip seal. I've tried running them lower (down to 65) but it's a noticeably slower cadence or tougher pedal on long rides at my weight with the lower air pressure.

I will set em up at 90/95 and by the end of the week they are ~75/80 and I air them up again.

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I'm on Belgium +'s, weigh more, run smaller tires and my pressures are lower than that:
25c Gp4k (29.5 measured) at 70f
25c Veloflex Corsa (27mm) at 80r

You should definitely go lower
S6 Evo
S5 Aero

by Weenie


backdoor
Posts: 18
Joined: Tue May 21, 2019 9:54 pm

by backdoor

Multebear wrote:
Wed Aug 07, 2019 12:51 pm
It really doesn´t make sense, to move to wider tires, if you don´t want a more comfortable ride. This means, if you run the same pressure as before with narrower tires, you don´t really get any advantage. You just get a heavier tire than before. I´m aware, that the air chamber is bigger, which gives you marginally more comfortable ride than with 25 mm, but nothing of any importance.
I don't necesarily agree with this. Multi-Surface rides could be the reasoning for going wider. If you were on the road only with good surface then yes, going wider would only be for comfort.
Multebear wrote:
Wed Aug 07, 2019 12:51 pm
There´s no need to go wider, if you don´t drop the pressure. AND if you drop the pressure, you might as well go significantly lower. I run my 32 mm with 2.8 bars (40 psi). I´m 90 kg. I ride all sorts of rides with those tires. Gravel, road, mountains, mountain descents e.g. Those rare occassions I run 28 mm, I´m doing 3.5 bars (50 psi). With wider tires you get better grip, especially when riding lower pressure.

You have to be careful with dropping pressure. For one - most tires are not designed to bulge out in the middle. If so then the casing is losing performance and will also wear out much faster. I don't disagree that bulging sidewalls make for a more comfy ride, I'm just saying it's not how the tire was designed to perform. More importantly you need to make sure you don't

"rim out". If your on a known patch of 50 miles of dirt and gravel road, go for it. But if you are jumping sidewalk curbs or railroad tracks you can kiss those 1200.00 carbon rims good bye because you wanted a more "Comfy" ride. The percentage of getting a pinch flat or sidewall cut goes up as the pressure goes down as well.
Multebear wrote:
Wed Aug 07, 2019 12:51 pm
But riding 80ish psi with 28 mm tires, IMHO that´s just totally missing the point of going wider. Might as well just go 23 mm and stay there. It´s faster and lighter. Don´t jump on the marketing BS about wider being faster.
Not true at all. On my road bike the 25mm tires are not going to make it up this -
Image
But had no problems getting up with 28mm slicks @ 85psi on my gravel bike. Would have been a much easier ride at 60 or 70psi or 32mm knobbed tires @ 45-50psi for sure. But I run the 28s @ 85/90 because its quicker on the road as this path is 12 paved miles from the house. Running 28s, I can still jump on old logging roads like this and while its not as plush a ride the 28s are much more manageable in the dirt and gravel than the 25mm's on the roadie. Granted if I weighed 70kg or 150 pounds I would be running at a lower PSI.

Here is a pretty good blog post on performance gains at different tire pressures - https://janheine.wordpress.com/2015/02/ ... d-details/

rides4beer
Posts: 172
Joined: Wed Nov 28, 2018 5:27 am
Location: SC

by rides4beer

Ran my new 28mm GP5Ks today at 75/80psi, very comfortable and handled great. They measure just a hair under 30mm on my 21c rims.

Lugan
Posts: 153
Joined: Wed Oct 26, 2011 9:02 pm

by Lugan

Why are so many posting tire pressures without telling us their body weight? It's all irrelevant without that.

rides4beer
Posts: 172
Joined: Wed Nov 28, 2018 5:27 am
Location: SC

by rides4beer

rides4beer wrote:
Thu Aug 08, 2019 4:15 am
Ran my new 28mm GP5Ks today at 75/80psi, very comfortable and handled great. They measure just a hair under 30mm on my 21c rims.
Guessing around 93kg rider, bike, water, etc.

Bigger Gear
Posts: 469
Joined: Fri Mar 27, 2009 6:58 pm
Location: Wet coast, Canada

by Bigger Gear

77kg

25mm Vittoria CorsaG Control on HED Belgium+, measure 28.2mm wide run at 75f/80r.

32mm Compass Stampede Pass on HED Belgium+, measure 33.1mm wide run at 65f/70r.

This is for paved riding on everything from smooth tarmac to rough chipseal and even some light gravel mixed in.

montster
Posts: 1
Joined: Wed Jun 19, 2019 6:23 am

by montster

65kg, ~8kg bike

Continental GP5000 28mm, 48.0psi front, 50.0psi rear, latex tubes, spirited road riding/racing

25.5mm internal width rims, tires measure out to be 31.2mm stretched

Pretty good so far.....

Multebear
Posts: 1318
Joined: Sat May 02, 2015 10:11 pm

by Multebear

rides4beer wrote:
Wed Aug 07, 2019 2:21 pm
Are you running tubes or tubeless? I just mounted up a set of 28mm GP5Ks on my road bike, they measure at 30mm with the 21c rims. I've been running 80/90 on the same tires on my other bike (10psi lower than what I run on tires that measure about 27mm), I'll try going a lil lower and see how it feels.
Tubes.

Multebear
Posts: 1318
Joined: Sat May 02, 2015 10:11 pm

by Multebear

backdoor wrote:
Wed Aug 07, 2019 9:55 pm
Multebear wrote:
Wed Aug 07, 2019 12:51 pm
It really doesn´t make sense, to move to wider tires, if you don´t want a more comfortable ride.
I don't necesarily agree with this. Multi-Surface rides could be the reasoning for going wider. If you were on the road only with good surface then yes, going wider would only be for comfort.
Agreed.

backdoor wrote:
Wed Aug 07, 2019 9:55 pm
Multebear wrote:
Wed Aug 07, 2019 12:51 pm
There´s no need to go wider, if you don´t drop the pressure. AND if you drop the pressure, you might as well go significantly lower. I run my 32 mm with 2.8 bars (40 psi). I´m 90 kg. I ride all sorts of rides with those tires. Gravel, road, mountains, mountain descents e.g. Those rare occassions I run 28 mm, I´m doing 3.5 bars (50 psi). With wider tires you get better grip, especially when riding lower pressure.

You have to be careful with dropping pressure. For one - most tires are not designed to bulge out in the middle. If so then the casing is losing performance and will also wear out much faster. I don't disagree that bulging sidewalls make for a more comfy ride, I'm just saying it's not how the tire was designed to perform. More importantly you need to make sure you don't

"rim out". If your on a known patch of 50 miles of dirt and gravel road, go for it. But if you are jumping sidewalk curbs or railroad tracks you can kiss those 1200.00 carbon rims good bye because you wanted a more "Comfy" ride. The percentage of getting a pinch flat or sidewall cut goes up as the pressure goes down as well.
Agreed. But you have to go pretty low in order for the tire to bulge out for this to be the case. At my weight (90 kg) the tire doesn´t bulge out at 50 psi. And that´s pretty low tire pressure.
backdoor wrote:
Wed Aug 07, 2019 9:55 pm
Multebear wrote:
Wed Aug 07, 2019 12:51 pm
But riding 80ish psi with 28 mm tires, IMHO that´s just totally missing the point of going wider. Might as well just go 23 mm and stay there. It´s faster and lighter. Don´t jump on the marketing BS about wider being faster.
Not true at all. On my road bike the 25mm tires are not going to make it up this -
[img]https://.cloudfront.net/2nNPs9qFs7uq4PTpv19rUz8sIjGFt7OpURPd-3sYPBo-2048x995.jpg[/img]
But had no problems getting up with 28mm slicks @ 85psi on my gravel bike. Would have been a much easier ride at 60 or 70psi or 32mm knobbed tires @ 45-50psi for sure. But I run the 28s @ 85/90 because its quicker on the road as this path is 12 paved miles from the house. Running 28s, I can still jump on old logging roads like this and while its not as plush a ride the 28s are much more manageable in the dirt and gravel than the 25mm's on the roadie. Granted if I weighed 70kg or 150 pounds I would be running at a lower PSI.
My answer to the OP was in the context of riding wider tires on-road, which I was under the impression was the question at hand.

The fact that you ride uphill on a gravel road on your roadbike with 80 psi on 25 mm tires, well that´s definitely not part of OP´s question. And why would you even do that at all? In order for this to succed, you need to at least lower the pressure to 50-60 psi. You obviously have better grip with wider tires on gravel. Who in the world would disagree with that.

That said, why in seven hells would you even ride 85 psi on gravel? Are you trying to brake your balls or ruin your back?

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nycebo
Posts: 127
Joined: Fri Nov 13, 2009 8:04 pm
Location: New York, NY

by nycebo

@multebear, in response to your last question: because people are stubborn as hell. They need only listen to any cycling podcast of late and learn that lower pressure (especially on non steel plated roads) is where it's at.

But then again, no need to beat a dead horse. They are happy and we are happy. Fine by me.

bikesrdangerousmmk
Posts: 112
Joined: Thu Jul 30, 2015 3:54 am

by bikesrdangerousmmk

~25mm internal, 28 Corsa 2.0 tlr, ~30.5mm inflated width

55/60 - 65/72psi. (F/R)

190-205ish lbs for rider and bike. Road setup

backdoor
Posts: 18
Joined: Tue May 21, 2019 9:54 pm

by backdoor

Multebear wrote:
Wed Aug 07, 2019 12:51 pm
backdoor wrote:
Wed Aug 07, 2019 9:55 pm
Multebear wrote:
Wed Aug 07, 2019 12:51 pm
But riding 80ish psi with 28 mm tires, IMHO that´s just totally missing the point of going wider. Might as well just go 23 mm and stay there. It´s faster and lighter. Don´t jump on the marketing BS about wider being faster.
Not true at all. On my road bike the 25mm tires are not going to make it up this -
[img]https://.cloudfront.net/2nNPs9qFs7uq4PTpv19rUz8sIjGFt7OpURPd-3sYPBo-2048x995.jpg[/img]
But had no problems getting up with 28mm slicks @ 85psi on my gravel bike. Would have been a much easier ride at 60 or 70psi or 32mm knobbed tires @ 45-50psi for sure. But I run the 28s @ 85/90 because its quicker on the road as this path is 12 paved miles from the house. Running 28s, I can still jump on old logging roads like this and while its not as plush a ride the 28s are much more manageable in the dirt and gravel than the 25mm's on the roadie. Granted if I weighed 70kg or 150 pounds I would be running at a lower PSI.
My answer to the OP was in the context of riding wider tires on-road, which I was under the impression was the question at hand.

The fact that you ride uphill on a gravel road on your roadbike with 80 psi on 25 mm tires, well that´s definitely not part of OP´s question. And why would you even do that at all? In order for this to succed, you need to at least lower the pressure to 50-60 psi. You obviously have better grip with wider tires on gravel. Who in the world would disagree with that.

That said, why in seven hells would you even ride 85 psi on gravel? Are you trying to brake your balls or ruin your back?
I'm not sure you correctly understood my post. I was on 28mm tires. Never would have attempted on my road bike with 25mm tires. The point I was making is that on wider tires I can ride fast on paved roads to get to the gravel and still ride the gravel. (Disagreeing with your point riding 28s @80psi has no merit )

Riding 85 PSI on gravel on 28mm wheels at my weight (86kg/190lbs) is not 7 hells break your balls ruin your back tire pressures. As a matter of fact here is a recent screenshot from a GCN short on gravel tires and reccomended pressures. This shows that for a 185lb rider on a 32c tire 80 PSI is reccomended.
Image

At 50psi on 28mm tires I would bottom out at my weight. To give you an example I dropped my 28mm wheels to 50psi (Using a topeak digital pressure gauge) and took a picture of the wheel standing over the bike with just my upper body weight pressing down on the handlebars. If I was riding at 15mph and hit a curb or a rock or a railroad track at 50psi I could damage my rims and would likely flat.
Image

I'm not crazy. I do listen to the podcasts and I am not jumping on all the latest fads. Using a little bit of science to figure out what pressures to run at is fun. I'm not trying to be a dick or tell you that you are wrong. Just trying to demonstrate why I run the pressures I that I do and how I got to those conclusions as well as the initial disagreement that running 80-85psi on 28's does have a purpose on the road (gives you non-paved options)
Attachments
GCN_TirePressures_Gravel_YouTube.jpg
Tire_50PSI_Rider185lbs.jpg

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nycebo
Posts: 127
Joined: Fri Nov 13, 2009 8:04 pm
Location: New York, NY

by nycebo

Backdoor, that's a cool photo. Given your weight and that photo, I think you could even get away with 75-80. Might be worth replicating the test and photo to see the differences. Thanks for sharing.

backdoor
Posts: 18
Joined: Tue May 21, 2019 9:54 pm

by backdoor

nycebo wrote:Backdoor, that's a cool photo. Given your weight and that photo, I think you could even get away with 75-80. Might be worth replicating the test and photo to see the differences. Thanks for sharing.
If I remember I think 60-65psi was the cushiest ride for me with a decent cushion for the rim with the 28c. Great for full on gravel or mixed rock trails. But it's a slog on harder pack dirt, gravel or road if you are on the flats or climbing.

I'm on the road for another week or so, when I get back home, If I remember I'll take some more photos at multiple PSI levels.

For speed on the tarmac, I've got a good section of downhill that's about 2.4 miles long. It's a section that I can ride from top to bottom without pedaling and I'll hit speeds from 35+ mph to 6mph and anywhere in between. It has sections from -15% to +4%. I've done this ride using multiple pressures to see if the different pressures make a difference in speeds going down the hill.

In reps of 3, I have found that between 85 and 95 psi on the 28c tires gives me the best speed. If I drop below 85 psi then I start to lose speed and above 95 there is very little if any measurable difference.

Keep in mind that my weight, bike weight, road conditions, road type (its chip sealed), weather and tire type (Conti Grand Sport 28s) all play into this number. I didnt save any of the data and cant recall any of the exact numbers.

I do remember the differences were minimal but repeatable using 10psi increments. (I think I used 100, 90, 80 and 70 then tried 85 and 95 without reps as riding up this hill 14 times (30 miles of climbing) was exhausting)

Not super scientific but was suprised at the repeatability of the results and it was fun to do just to see how the pressures of the tire made a difference. So many articles talk about tire pressures but never mention the weight of the rider.

I see posts all the time that riders are like - I keep my tires at 20psi. But they never mention that they weight 120lbs and are riding 40c tires.


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Leviathan
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by Leviathan

Cos it was a quiet night at the hotel yesterday- data from this forum thread: x= Weight in Kgs, y= Ave tire pressure (f+r)/2 in PSI.
Image

by Weenie


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