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Rene Herse tire pressure calculator

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Danneaux:
Hi All!

For the last 25+ years, I've used the 15% "drop" tire pressure recommendations developed by American petroleum engineer and Bicycling magazine technical editor Frank Berto in concert with some leading tire makers' data. I've found this worked well for my needs and in the last several years, an Android app was developed from his body of work that makes pressure calculations quick and easy based on bike and rider weight and rider positioning, providing differential F/R pressures. For a bit more on this, see one of my past posts...
http://thorncyclesforum.co.uk/index.php?topic=12834.msg96188#msg96188

Now, Rene Herse Cycles has developed a free online tire pressure calculator based on their own research as developers of the original Compass brand (now also Rene Herse) tires. See...
https://www.renehersecycles.com/tire-pressure-calculator/

It comes with two intriguing caveats...

--- Quote ---The calculator gives you two tire pressure recommendations. Use the ‘Soft’ value for rides on rough roads or if you prefer a more comfortable ride. Use the ‘Firm’ value if you like your bike to have a firm feel. The ‘Firm’ values also provide a considerable margin of safety if your pressure drops a bit. With the ‘Soft’ pressure, you are stressing your tire casing more, and it may wear out faster.

Bicycle Quarterly’s extensive tire tests have shown that – on smooth roads – supple high-performance tires roll at the same speed at either of these two pressures. Pressures between these two values roll a little slower. On rough surfaces, your bike will be faster at the ‘Soft’ pressure.
--- End quote ---
And, at variance with the Berto method...

--- Quote ---Front v. Rear Pressure
Most bikes carry more weight on the rear wheel than the front. However, when you brake hard, almost the entire weight shifts to the front wheel. For that reason, it’s not advisable to run a lower pressure in the front tire.
--- End quote ---
I recently got a pair of free (Craigslist/Gumtree curbside giveaway) nearly new handmade Challenge Strada Bianca Pro 700x36 tires. See...
https://road.cc/content/review/challenge-strada-bianca-pro-tlr-280335
Both are dirty, front one perfect, rear with a 5mm cut in the sidewall I plan to glue and boot with Tyvek before trying on my gravel bike using the Herse pressure recommendations. It'll be a fun experiment to see if I like the tires and to also play with pressures while enjoying some of my favorite gravel roads.

I'm not at all sure the Herse calculator recommendations will work so well/produce similar rollout results if applied to tires with sidewalls stiffer than their own brand. That's why I'm planning to try them with the Challenge Strada Bianca Pros, the closest tires I have to those produced by Herse. If one of you try the Herse calculator and recommendations, I'd love to hear your impressions and results for the tires used.

Best,

Dan.

Matt2matt2002:
Interesting article.
Thanks Dan.

Schwalbe Marathon Plus HS440 Tyre with Reflex - 26 x 1 3/8 Inch / 650 x 35A 37-590
ETRO37-590

Am I right in thinking the tire width is 37mm?

Best

Matt

mickeg:
I am not going to try to figure this out, is one slightly above and one slightly below the 15 percent?

When they first came out with the 15 percent, I thought that was absurdly too low for front, they did not clarify that initially that the front should have more than the 15 percent for braking reasons.  I think it was originally published in Bike Quarterly, I have a one page version with no date.  The ACA version has a date of 2009, I think this came out later.
https://www.adventurecycling.org/default/assets/resources/200903_PSIRX_Heine.pdf

Because I thought it too low, I generally run my front at about 70 to 75 percent of the rear pressure (if rear is at 80 psi, I would run front at about 60 psi).  I have no basis for this ratio that I have been using, but have been doing it for years and it has worked well.  But I have run my front lower than that on rough chip seal when the front gave me too much vibration on the rough pavement.

Right now on my Lynskey with 37mm tires, I have an old Marathon XR on the front, I run that a bit higher than my 70 or 75 percent of rear norm because that is a high rolling resistance tire and at lower pressures it feels like I am pulling a boat anchor.

For touring, I think I usually have my rear about 15 percent tire drop, but with a heavy load that 15 percent might be the tire max pressure or close to it.

Years ago, I basically took their chart and ran the lines farther to the right with a straight edge because with my touring load on the rear tire, I was off their chart.  My 700c touring was on 37mm tires.  I also used the 37mm pressure for my 40mm Marathon (with Green Guard) tires on my 26 inch wheel Sherpa.

I will probably never run tubeless, but I have heard that road (narrow) tires that are tubeless at low pressure can "burp" in corners and suddenly lose enough pressure to cause crash and injury.  I have no clue if these pressures they are talking are low enough to be a hazard for tubeless or not, just commenting on that. If there is a minimum tire pressure listed for a tubeless tire, I would NOT go below that.



--- Quote from: Matt2matt2002 on March 25, 2022, 09:55:03 PM ---Interesting article.
Thanks Dan.

Schwalbe Marathon Plus HS440 Tyre with Reflex - 26 x 1 3/8 Inch / 650 x 35A 37-590
ETRO37-590

Am I right in thinking the tire width is 37mm?

Best

Matt

--- End quote ---

I would say that is close enough.  Or see what they say in the link I posted above.

Danneaux:

--- Quote ---Schwalbe Marathon Plus HS440 Tyre with Reflex - 26 x 1 3/8 Inch / 650 x 35A 37-590
ETRO37-590

Am I right in thinking the tire width is 37mm?
--- End quote ---
Most likely or within 2mm or so...but I always caliper mine to make sure, as actual tire width depends in part on the width of the rim.

Matt, you may wish to double-check the tire size if you intend this for your Raven, as it is a fractional 26in, not a decimal 26in. The diameter is very different, as 26in is intended for rims labeled 559mm, while this one is larger at 590/650A. For more information on the difference, see...
https://www.sheldonbrown.com/tire-sizing.html#fraction

Best,

Dan.

Moronic:
The calculatormrecommends 33psi as the 'soft' pressure for my 50mm tyres at my weight.

That's about what I've found good from trial and error. Although I am starting to think mine work better around the 28-30 mark.

That's G-One Speeds, recommended minimum 35 I think. There was a piece on a good Euro bikepacking site that argued most makers' recommended minimums were way too high for best results.

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