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Re: Flanders tire pressures [lanierb] [ In reply to ]
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I just want to ask who won Flanders? Oh yeah... EF came from nowhere and won. Josh/Silca works directly with them. Just saying. ;-). Maybe it was the 450$ pump.

The silca articles on tire pressures are some of the smartest out there. It is free info, free speed.

And i just ordered their digital pump. I figure 1% accuracy will be good enough, given their best is 0.5% accuracy (but with an analogue dial where the eye can decieve).

What did it for me was the article on “comfort frames”. The stiffer “race” vs more compliant “endurance” frames effect on ride comfort was often in the difference of 4psi in tire pressure. Why am i going for all these marginal aero and weight gains when i am possibly throwing much of it away with tire pressure innaccuracy with a cheap pump?

As they say in the world of scientific research: “garbage in = garbage out”. If you are serious about getting the marginal gains from tire pressures... step one is accurate pressures.
Last edited by: Rocket_racing: Apr 10, 19 16:12
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Re: Flanders tire pressures [G-man] [ In reply to ]
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G-man wrote:
Have been running 28-32s on most all my bikes for the past ten years or so. I don't think it is very likely at pro riders weights to pinch flat a 28 tubular at 80-90psi. 32s at 75 psi seem pretty darn firm. I am 100kg and have never pinched a 28 clincher at 75 psi with some pretty big hits. I sort of grain of salt those numbers, but if that is what they ride that is what they ride.

I’m waiting by with popcorn for when somebody calls you fat. 😂

When I put 28’s on my gravel bike for road use, they were remarkably fast at 60-ish PSI.
(I’m about 70-ish kg)
And still plenty o protection for riding off-road on carriage trails and light single track.


float , hammer , and jog

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Re: Flanders tire pressures [Murphy'sLaw] [ In reply to ]
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Hey Murph, I resemble those remarks. And I am also old. On another post I mentioned I also have a 49 year old Silca Pista pump that is daily user. Now that I am older, fatter and have more money than when I bought my first Silca Pista, I got their new fancy schmancy Floor pump with the 60 psi gauge. It is pure sweetness. I am guessing both of them will long out live my riding days. Be careful about advertising your weight Mr. Murph, sometimes age and good eating add a couple kgs to the body. I raced at a lower weight than you, once upon at time long ago.
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Re: Flanders tire pressures [trail] [ In reply to ]
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trail wrote:
Cobbles are pinch-flat minefields. Even with tubulars. Unless your name starts with Mathieu or ends with Poel, a flat is pretty much game over in the latter half of the race. So they're trying to avoid that.

Hit some of these edges at 30MPH and 60PSI....



1. None of the cobbles at Flanders look anything like this. Even the worst cobbles in Flanders are better than any of the "good" cobbles at Paris Roubaix. I was just in Belgium for Flemish week and did the full Flanders sportif and also rode over to Roubaix one day to do a section of cobbles there. Night and day difference, the Flanders cobbles are sort of fun/challenging, the Roubaix cobbles are garbage and basically feels like you are being punched around. Not sure why anyone would want to do the PR course for "fun".

2. It is pretty hard to pinch flat at Flanders, I did over 200 miles on the course last week and did lots of cobbles running 80 psi on 28mm clincher tires with latex tubes. Can't see any reason why anyone would run over 100 psi. In the sportiv (which had 16,000 riders) I hardly saw anyone with flats.

In short, don't believe the hype.
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Re: Flanders tire pressures [tri_yoda] [ In reply to ]
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tri_yoda wrote:

In short, don't believe the hype.

The hype is low pressure. :) Tradition is high pressure.
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Re: Flanders tire pressures [Jason N] [ In reply to ]
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Jason N wrote:
I also get the impression that the certain sections of the Rouabix cobbles are just nastier than Flanders...but I could be wrong.


Flanders cobbles are like tarmac compared to anything at Roubaix. I did the entire Flanders course last week, very fun. I went over to Roubaix just to check out the velodrome and try out one section (3 star, so not even close to the really bad ones) and it was like an order of magnitude worse than anything at Flanders. I think it is a misnomer to talk about the "cobbled classics". Paris Roubaix is an absolute beast (and I say that based on riding one section of cobbles, it was brutal) and is in a class by itself compared to Flanders. After having a full serving of Flanders and a taste of Roubaix, they are completely different races, especially with respect to the cobbles.

Cobbles at Flanders and Gent Wevelgem were bumpy (but they were mostly all uphill at lower speeds), but overall there are not a lot of cobbles in these races and besides being a bit bumpy and slower going/more effort they really weren't a big deal. They add some "character" to the race, but they don't seem like any kind of game changer and it didn't seem like there was any special skill to riding them, just need more power.
Last edited by: tri_yoda: Apr 10, 19 21:09
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Re: Flanders tire pressures [Rocket_racing] [ In reply to ]
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The problem is that if you run latex tubes then you could easily lose 4PSI during the course of a long day in the saddle!
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Re: Flanders tire pressures [rmt] [ In reply to ]
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rmt wrote:
Based on the work that Joshatsilca did (when he was at Zipp??) and the extremely interesting articles that he wrote, I'd say those seem surprising. A quote from his articles, talking about Paris Roubaix:

"The 28mm tire in the low-mid 60psi range proved to be nearly 1km/hr faster than the 24mm tire with pressure in the mid 70 psi range (which is what is required to prevent bottoming the tire) when the data was normalized for rider power output."

If you haven't read the articles, they're fascinating:


Sorry - can't find part one
Part 2: https://silca.cc/...ures-are-everything#
Part 3: https://silca.cc/...t-created-the-future


Those are interesting articles thank you for sharing and thank you to the author for writing them.

I'm still not paying $450 but thank you :)
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Re: Flanders tire pressures [joshatsilca] [ In reply to ]
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joshatsilca wrote:
Funny enough, I'm here in Lokeren right now with the teams working on this for both races.

What I know for sure is that all the teams are bullshitting to the media (and each other) about pressures and I'm strictly forbidden from discussing numbers between teams in any detail but can tell you first hand that those numbers are not right. We work with EF and Bora officially and a few other teams unofficially and I'm unaware of anybody running 100+ on 28's.. though it wouldn't surprise me if some of the smaller teams are doing stuff like that, I find all sorts of crazy stuff happening in the little teams ;-)

Laughing so hard at this right now. Thanks for updating us with this tidbit!


-Bryan Journey
Travel Blog | Training Blog | Facebook Page
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Re: Flanders tire pressures [newManUK] [ In reply to ]
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newManUK wrote:
Those are interesting articles thank you for sharing and thank you to the author for writing them.

I'm still not paying $450 but thank you :)

We make $99 pumps too.. ones that will last for 40 years, so its not all bad ;-)

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
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Re: Flanders tire pressures [lanierb] [ In reply to ]
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Well Kristoff apparently won't try tubeless again at Paris-Roubaix. Although it's unclear with the information given what pressure he attempted at P-R, or if the issue was truly specific to tubeless. I'm speculating he was pinch-flatting given the reference to "holes."

It's the paradoxical issue that lower pressure might given reduced rolling resistance and increased comfort, but increase the odds of a catastrophic flat. Josh@Silca wrote a blog post about this sort of assymetry where you go faster, faster, faster....then suddenly drop off a cliff.
Last edited by: trail: Apr 16, 19 6:55
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Re: Flanders tire pressures [joshatsilca] [ In reply to ]
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Josh at Silca, you are way wrong about your $100 pumps being able to last 40 years. My original will be 50 years old next fall and it works as well as the day I bought it. I did blow up the hose when we tried to pop a Conti track tire and took it up to 240psi(14.5 Bar) scared the bejesus out of us. Needed a new gauge after only a few years over 30. Been thru probably 50 head gaskets and 25 leather washers. One freekin hell of a pump.
On another note, I am still wondering what exactly caused Kristoff's punctures. I heard he had very light weight 25 mm Specalized tires on Campy wheels. I wonder if they burped, blewout, pinched or what. I know a bunch of cross riders burping the tires at pressures in the low 30s in cross races, but the mtb folks rarely do. He said he took a big risk and lost. That was pretty stupid thinking in my thoughts.
Interesting how things ebb and flow. I started out riding 28mm Clement Champion Du Mundo silk tires in the 1960s and went as low as 18mm tires in the late 1980s and now my smallest road tire is a 28mm and favorite is a 32mm. I know a lot of bikes won't fit over 25mm tires, but I am betting they all will in a few years. That is nice about disc brakes, they allow for larger tires. I heard a few reports from guys on the Velocipede forum that had all kinds of flat problems on the cobbles last weekend. Thanks for the inside words Josh.
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Re: Flanders tire pressures [G-man] [ In reply to ]
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If kristoff ran actual 25mm tires at his size/speed... i will bet that he pinch flatted and burped at the same time, causing pressure loss and a chain reaction of pinch flats as pressure dropped critically low with even more burping.

Tubular would have kept the air and been ok as long as they did not pinch flat.

25mm would be a risky choice.
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Re: Flanders tire pressures [Rocket_racing] [ In reply to ]
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Trail, Gman and Rocket -

So Vittoria had given the new Corsa TLR 2.0 to teams a few months back, and honestly, theses things are a bit like magic.. super low Crr and really beautiful ride quality. A couple of the teams put them into racing straight away and have had some great results. A couple of big races have already been won this year on this tire and there is a real sort of magic reputation that the tire has taken on with riders and some of the staff.

Problem of course being that while the overall race speeds have only gone up a few km/hr over the last 20 years, the speed over the pave sectors, particularly Arenberg have risen dramatically. It is common for teams to essentially do a leadout for their key riders onto the harder/narrower sectors, so Arenberg for instance is seeing speeds 5-10kph faster than 20 years ago. This puts way more stress on the tires and wheels and leaves way less margin for error when the tire impacts the cobble edge.

For example the extra 5mm or so or distance between the rim edge and road surface of riding a 30mm rather than a 25mm equates to a ~70% increase in the energy required to bottom the tire against the rim.. so there are some non-linearities in play here that can really bite you in the ass if you aren't accounting for them up front in the math..

So yes, his punctures were pinch-flat / tire damage type punctures caused by riding a tire that was just way too small for these speeds. They could have offset some of this with considerably higher pressures, but of course that presents it's own different problems.

Also, for Rocket_Racing, you can easily pinch flat tubulars here as well.. we saw quite a lot of that in the early days of trying to develop carbon rims for Roubaix.. we could make rims that were more or less unbreakable, but then the failure just transferred to the tire, which made it abundantly clear to everybody that the solution just had to be larger tires.

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
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Re: Flanders tire pressures [joshatsilca] [ In reply to ]
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I want to see crr data on the corsa and corsa speeds with the 2.0 compound. Conti made some big gains with the gp5000, and i assume the corsas will at least keep pace, but all i have seen is marketing bar graphs with no real numbers.
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Re: Flanders tire pressures [joshatsilca] [ In reply to ]
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Josh, can you share any data of the new corsa tubeless on the pecking order of crr?
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Re: Flanders tire pressures [Rocket_racing] [ In reply to ]
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Can't say at this moment, and honestly we've worked with team stuff which isn't 100% production.. but I can say that these tires are exceptional and everybody who tests, touches, rides them is extremely impressed, and compared to tubulars they are definitely faster. There is chatter through the peloton about them and riders in teams that got a couple of pair are actually asking to use them.. which says that in 2 months the tire has gained a reputation.

I think that Vittoria was very, very smart with the way they introduced this one to the peloton.. each team got 2 pair, and it's created a real desire to be the rider that gets to ride them. Had they given the team 100 tires and told the riders they had to ride them, there would be revolt.. so they've hit the sweetspot of right technology and right psychology with this one, though in reality the teams have a long way to go on the logistics front with tubeless.

Either way, the situation at UAE with Kristoff was unacceptable in my mind, but there were also 5-6 of the small teams making equally bad or worse decisions, but for a team that size with that budget, resources and access to knowledge.. unacceptable.

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
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Re: Flanders tire pressures [joshatsilca] [ In reply to ]
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Yeah, some marketing going on there for sure. Give the pros some hot non-production stuff and let it build. Obviously they make fast tires (corsa speed tubeless)... or none of it would work.

So are the pros using a tire closer to a corsa speed, or the corsa? I presume the former.

So, the question on your podcast about why pros continue to use tubular in the face of some pretty fast tubular options... sounds like tubeless may quickly become the standard in a few years, at least on the flatter events. One big high profile failure/injury could slow it down however.

I would like to see the calculus where, all else equal, when crr vs weight show their advantage (thinking average grades).
Last edited by: Rocket_racing: Apr 16, 19 19:15
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Re: Flanders tire pressures [MarkyV] [ In reply to ]
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MarkyV wrote:
was there a vid or link that didnt come thru?

Sure was

Cobble video from Caley Fretz on Insta.

The above poster is a physiologist employed by PEARL iZUMi. However, statements are not made on behalf of nor reflective of PEARL iZUMI in any manner... unless they're good, then they count.
-----------------------------------------------------------------
instagram.com/robertpickels
twitter.com/RobertPickels
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