No, generally those pressures are way too high. It will vary by wheel width, but to give you an idea, here's ENVE's recommendations for their wheels:

You also have to factor in rim width. This chart quite a while ago when most rims were 15-17mm internal. Now you have a lot of rims ranging from 18-21 internal which in turn means that the ideal pressure for each tire size could be even lower. I know HED plus sized rims are 21 mm internal and have a max pressure of 90 psi, even for a 23 mm tire.

The ENVE chart is better than most and if anything a bit low if riding on good pavement and a bit high for riding on poor quality surfaces..
The Michelin chart is way off and HED's recommendation for 90max on their plus sized rims is based on tire blow off pressure and not on Crr considerations... which is true of all rim and tire max and min limits printed on the products or in the sales information, that is a calculated value based on a tested blowoff pressure which is required by law in the EU

We have lots of information on this including data and such at the SILCA blog: https://blog.silca.cc/page/5

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Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
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Based on my reading, I thought those pressures were way too high. However, using the Enve chart I would be running 65 psi. That seems low.

I weigh in at 145 lbs. Closer to 140 on race day. I am running Zipp 808 carbon clinchers. Rear is a 2012 with aluminum brake surface (I'm still running it because my power tap is laced in it. Front is all carbon Firecrest 808. Continental GP5000 tires, 23. I still have to get real installed tire width. I wouldn't have imagined running 65 psi.

Is there a later chart that would apply to my set up?

The bottom of this chart lists that these PSI recommendations are for a tubeless set up. I would imagine the recommendations would be lower for tubeless as the primary concern with lower pressure is pinch flats, but I guess I don't know.

I wish I knew the magic number I should be riding at but the whole thing feels like a guessing game to me.

Those numbers seem REALLY low...

At 180 lbs, with 25mm tyres :

From Calvin386 table, I should put 102 psi
From Enve table (even if 17mm inner width, not 18/20) : 70 psi
From Silca test, on "coarse asphalt" : 90 to 95 psi

Is it me, or the Enve figures are really low, much lower than the Silca rec. ?

Does Silca have a chart or are you referring to their 5 part series?

Where are you seeing even with 17 inner width on enve chart?

I think enves are wider than most so you’ll see the lowest pressure rec with them.

For those questioning lower pressures, give it a shot. I am currently in the process of switching to disc brake wheels and have sold all of my hed +. Currently running the stock cannondale caad10 rims (which I’m guessing are narrow), and am running 60psi on 28mm tires. Haven’t pinched flatted in a couple months riding like that.

Edited to add I’m typically just over 160lbs.

Now I’m mainly doing that for comfort on training rides. I raced last season at 90psi on 20mm SuperSonics on hed + rims. I’ll have to do some experimenting on my new enves to figure out what pressure seems fastest on varying road surfaces (after I determine what tire/size seems like the best for them).

Yes refering to this :
https://silca.cc/...stance-and-impedance

The ENVE numbers would be fine if they were specific to a rough surface. Yes, the width of the ENVE rim tire well plays a factor in lower pressures, increasing volume in the tire and making it behave as a tire of larger width... the thing to remember though is that the tire doesn't gain all the radial height that you would get from the wider tire.. so while you can make a 25mm tire 28mm wide, your rim edge will be ~2mm closer to the ground that it would be on a 28mm tire on a slightly narrower rim..

Having said that, look at the charts in our blog, those are actual measured values on various surfaces and you can see that the difference in road surface roughness is a major factor. Similarly, rider system weight is a big player.. so you can't just go off of rider weight, but need rider+ bike.. and also need weight distribution front/rear.

I typically tell people to pick a starting point and drop pressure from there, but if you are on the ENVE chart, I'd start there and go up a bit.

As an additional data point, I'm 175lbs and ride a 21lb steel road bike with 28mm Corsa G+ on 17.5mm inner width 303's. Tires measure 30.1mm and my optimal setup is 66/68psi front rear while their chart would have me at 56-57psi.. which is a fine pressure, but is well below optimal based on our testing on crappy Indiana roads... on nicer or newer roads the delta would be greater still as my optimal pressure would be greater than the 66/68

I'd suggest listening to our podcast to learn more here, but the real way to do this is to keep a log and test it for yourself on your riding surfaces. We do this with all of our pro teams and athletes and it is invaluable to keep that log so you can go somewhere new, and say 'this looks similar to X' and then you have a solid starting point for you, and your setup.

www.marginalgainspodcast.cc

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http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

 
My rims have inner width of 17mm
Enve chart have a column for 18/20.5mm (19.25mm average) width, the 70 psi comes from this column

Let's suppose a 12% (19.25mm vs 17mm) larger rim give a 12% larger tyre.
According to RBR, this should remove 6 to 9 psi.

95psi - 9 psi = 86 psi

Not 70 psi

The Enve reco is really lower than the Silca, even with rim width correction.

Good for really bad roads ?
And/or for heavy casing training tyres ?

On really bad roads and with big strong training tyres, I could use the Enve rec (80 PSI with my rims)
With GP5000 on reasonnably good roads, I will stick with Silca rec (90/95 PSI with my rims)

Damn. I need to catch up with the times. I've been running 90psi @ 154lbs with Zipp Super9/808 and 23mm Conti GP TT, assuming average to good surface conditions. Probably not too far off for Roth last year but those roads are above average.

Yep I agree with all of this. If enve is correct that a 25mm tire is fastest on their rim I will almost certainly race about 80-85 psi I’d guess.

1. love the podcast---keep going deeper in your thoughts and discussions. Let that mind run loose with discussion

2. can you post what poor/average/good road surface looks like? I just sometimes wonder what definitions are used here. Even fresh laid asphalt looks different, sometimes quite substantially. What does grooved cement count as if we are riding with or against the grain?

Am I right in that they don't mention the weight? Would it make sense, to mount the bike, and get someone else, to inflate the bike wile you are mounted?

No point the pressure wouldn't change.

The only difference is the contact area of the tyre increases so that the area is proportional to the weight it's supporting. Remember the tyre pressure is in pounds per square inch. So if you weigh 180 pounds, and the bike 20 pounds then the front and rear tyre area at 100PSI is 2 inch (so just under 1 square inch on the front and just over on the back). Get off the bike then the pressure is the same, but the contact area is much less (2/10 of a square inch). It's the tyre shape that deforms and not the pressure that changes.

And of course the force on the ground is also 100 psi in both cases. Why a small lady in stilletos will sink into grass whilst an elephant wont.

However, if you use this excuse to get a servant to pump up your tyres for you, then fair play.

HED refers to the chart on their manual (page 7): https://www.hedcycling.com/...hManual_03082018.pdf

Of cause I dit not think of the pressure in that way. But if the deformation of the tyre is importen, how do I find my starting pressure. Is the deformation of 15% still a good starting point.
I once found this formula, and I think it is for calculating the pressure needed for 15% deformation?

PSI = 153.6*lbs/(tyre size in mm^1.5785)-7.1685

They mention weight :

"For this test, a rider on a Cervelo P4 in the aero position was used. A TT position is helpful for this type of testing as it reduces the variability of the aerodynamic drag. A TT bike also has nearly 50/50 weight distribution, so equivalent front and rear tires pressures were used. Rider and bike total weight was 190 lbs, we used water inside water bottles to maintain equivalent total mass over the duration of the testing."

They mention also tyre : Conti GP4000 S2

And rim inner width : 16.25mm (as it is 404 Firecrest), coherent with 25.8mm tyre width measured (27mm measured by RBR with a 17c)

I read that. I was thinking more of an updated baseline chart similar to the one I posted at the top that could be used to make race day tire pressure decisions based on conditions at the event.

Silca's blog is pretty comprehensive. I will probably just make one for myself based my personal stats

Thanks Josh.... This is what I gathered from your articles. I need rider weight plus bike weight plus conditions to determine ideal tire pressure. What shocked me, is how low the numbers are being in the neighborhood of 140 lbs on race day. I would have never even considered those numbers.

It seems the only real answer is to make an informed guess and do your own testing from there. I will be outside soon on a repeatable course. Let the logging begin....

The HED charts are also quite low for optimal Crr based on our testing and data. Looks to me like they just drew a line from their max rim rated pressures making sure to hit all of the multiples of 5 on their way down. It's a method, but based on a rule of thumb/estimation and in no way based on data.

The 15% drop of Berto is another method for starting out, but also leaves a lot to be desired IMO. I'd say those numbers look great assuming rough pavement, but beware the weight distribution. When descending you will take on a more aggressive and front heavy position, and the attitude of the bike in a descent further biases weight toward the front.. so using the Berto charts and static weight distribution results in a way under inflated front tire for any type of high speed or aggressive descending. I would start with Berto and maybe go 2-4% lower in front pressure than rear as a starting point.

Either way, so much of this is based on your body, your setup, and your road conditions, that any of these methods needs to just be a starting point from which you experiment and take good notes!

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Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

I played around with pressure quite a bit over the years, and using Josh's method of starting at say, 90 psi and coming down 5psi until the tires start 'misbehaving' so to speak and then going back up. I'm around the same weight as you running 23mm 4000s, and I've settled on 80psi rear and 77psi front for average road surfaces (yes, that's the subjective part!). I think 80psi is a good starting point for our weight using 23mm tires - though keep in mind the 5000s are a little narrower compared to the conti 4000s in the stamped sizes.

I'm use rims with internal width of 18mm.

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