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Re: Zipp's Rolling Road and Some Interesting CRR Data [LAI] [ In reply to ]
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LAI wrote:
That took longer to show up here than I thought it would. Also, not sure why anyone would think 55psi is "super low" on a 28mm measured tire.


Super low to me. I know about this breakpoint where increasing pressure causes increasing power on a rough surface, but if I pump up less than 101 psi I get problems wit snake bites (running tubes in my clinchers though, di not have tubeless). Used to pump up upto 122 psi when I still thought the harder the better.

Still with 55 I think I would not get vey far.
Last edited by: longtrousers: Jul 14, 20 0:12
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
LAI wrote:
That took longer to show up here than I thought it would. Also, not sure why anyone would think 55psi is "super low" on a 28mm measured tire.


Super lw to me. I know about this breakpoint where increasing pressure causes increasing power on a rough surface, but if I pump up less than 101 psi I get problems wit snake bites (running tubes in my clinchers though, di not have tubeless). Used to pump up upto 122 psi when I still thought the harder the better.

Still with 55 I think I would not get vey far.

I acknowledged in a later post that this is all biased towards Tubeless. Tubeless is the key for running comfortable and still fast pressures. FWIW, I run tubes in my Time Trial setup and am nowhere near 55psi.

My YouTubes

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Re: Zipp's Rolling Road and Some Interesting CRR Data [LAI] [ In reply to ]
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LAI wrote:
longtrousers wrote:
LAI wrote:
That took longer to show up here than I thought it would. Also, not sure why anyone would think 55psi is "super low" on a 28mm measured tire.


Super lw to me. I know about this breakpoint where increasing pressure causes increasing power on a rough surface, but if I pump up less than 101 psi I get problems wit snake bites (running tubes in my clinchers though, di not have tubeless). Used to pump up upto 122 psi when I still thought the harder the better.

Still with 55 I think I would not get vey far.


I acknowledged in a later post that this is all biased towards Tubeless. Tubeless is the key for running comfortable and still fast pressures. FWIW, I run tubes in my Time Trial setup and am nowhere near 55psi.

Yes I thought that would play a role, tubeless or not.
What strikes me still though is that the article of zipp linked in the first post states:
"The 303 Firecrest has a max tire pressure of 72.5psi (5 bars)"
where I guess that the 303 Firecrest is also suitable for non tubeless use.
5 bars seems to be very low to me, but probably I have to learn and go even lower than the 100 psi I run at the moment.
I'm a bit confused at the moment.
I might try to run 6 bars with conti 5000, I weigh 190 lbs; do you think that would be ok? I would fear flats, especially in a race I rather loose some speed as getting a flat.
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
I might try to run 6 bars with conti 5000, I weigh 190 lbs; do you think that would be ok? I would fear flats, especially in a race I rather loose some speed as getting a flat.


Well your issue is the 190lbs. If you're running something like a 28 then yes, you should be fine around 90psi/6bar. I'm a tubular guy that kind of moved on from tubies, but what I loved about my tubies was the ability to not run ridiculous pressures to avoid pinch flats. Now, that phenomenon is much less a concern for someone of my size, but the fear was still there.

In terms of pressure we need to look at volume and the larger the tires obviously the lower the pressure, all things being equal. In my Time Trial setup, which runs latex tubes and 23mm corsa speeds, I'm around the 6bar mark. but bear in mind that my entire system weight is ~30lbs less than just your weight. I also run as high a pressure I can get away with for the pavement I ride. Most of the stuff I ride on is like glass. For some of the Time Trials I do that have a lot more broken pavement I adjust down.

Really you need to experiment. If you're into testing then find a stretch of road that matches what you ride and figure out what works best. Then you'll have to figure out if pinch flats will be a problem. FWIW, I would ride a slightly higher pressure than optimum if it meant I would finish the race instead of taking a wheel from neutral service.

For testing out what works I suggest http://cdacrr.blogspot.com/

My YouTubes

Last edited by: LAI: Jul 11, 20 3:45
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
5 bars seems to be very low to me, but probably I have to learn and go even lower than the 100 psi I run at the moment.
I'm a bit confused at the moment.
I might try to run 6 bars with conti 5000, I weigh 190 lbs; do you think that would be ok? I would fear flats, especially in a race I rather loose some speed as getting a flat.

I weigh a bit more than you (215 at the moment, have been heavier over the last few years), I haven't run anything above 95psi in years. I can't remember the last time I had a pinch flat. With 23mm GP4Ks (which measure 26mm on my wheels) I'm running around 90psi, and with 25mm GP4Ks (which measure 28mm) I'm running around 80psi. If I were 190 lbs, and/or my tires measured wider, I'd be running even lower pressures...

"I'm thinking of a number between 1 and 10, and I don't know why!"
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Re: Zipp's Rolling Road and Some Interesting CRR Data [Warbird] [ In reply to ]
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Warbird wrote:
longtrousers wrote:
5 bars seems to be very low to me, but probably I have to learn and go even lower than the 100 psi I run at the moment.
I'm a bit confused at the moment.
I might try to run 6 bars with conti 5000, I weigh 190 lbs; do you think that would be ok? I would fear flats, especially in a race I rather loose some speed as getting a flat.

I weigh a bit more than you (215 at the moment, have been heavier over the last few years), I haven't run anything above 95psi in years. I can't remember the last time I had a pinch flat. With 23mm GP4Ks (which measure 26mm on my wheels) I'm running around 90psi, and with 25mm GP4Ks (which measure 28mm) I'm running around 80psi. If I were 190 lbs, and/or my tires measured wider, I'd be running even lower pressures...

I remember a snake bite when I had a bit lower pressure, anyway I have 23 mm front and 25 rear and as I said I pump up to 100 psi at the moment. You have 80 psi. Isn't it strange that zipp restricts such:
"The 303 Firecrest has a max tire pressure of 72.5psi (5 bars)"

I mean at least me but even you as a rather low pressure rider could not purchase this rim because you can only inflate it up to 72.5. I think, but correct me if I'm wrong, that also Tom A and Josh at Silca talk about pressures of 100 psi on rough roads. Although lower pressures are even faster but more prone to flats. This max of 72.5 psi just feels strange to me as if it is a typing mistake.
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
This max of 72.5 psi just feels strange to me as if it is a typing mistake.

Definitely not a typo. The reason is that both the 303S & 303 Firecrest are hookless rims. ETRTO standards only rate any hookless rim up to a max pressure of 72.5psi.

So basically, run higher at your own risk (and no doubt invalidate any warranty cover)
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
Warbird wrote:
longtrousers wrote:

5 bars seems to be very low to me, but probably I have to learn and go even lower than the 100 psi I run at the moment.
I'm a bit confused at the moment.
I might try to run 6 bars with conti 5000, I weigh 190 lbs; do you think that would be ok? I would fear flats, especially in a race I rather loose some speed as getting a flat.


I weigh a bit more than you (215 at the moment, have been heavier over the last few years), I haven't run anything above 95psi in years. I can't remember the last time I had a pinch flat. With 23mm GP4Ks (which measure 26mm on my wheels) I'm running around 90psi, and with 25mm GP4Ks (which measure 28mm) I'm running around 80psi. If I were 190 lbs, and/or my tires measured wider, I'd be running even lower pressures...


I remember a snake bite when I had a bit lower pressure, anyway I have 23 mm front and 25 rear and as I said I pump up to 100 psi at the moment. You have 80 psi. Isn't it strange that zipp restricts such:
"The 303 Firecrest has a max tire pressure of 72.5psi (5 bars)"

I mean at least me but even you as a rather low pressure rider could not purchase this rim because you can only inflate it up to 72.5. I think, but correct me if I'm wrong, that also Tom A and Josh at Silca talk about pressures of 100 psi on rough roads. Although lower pressures are even faster but more prone to flats. This max of 72.5 psi just feels strange to me as if it is a typing mistake.

Actually, I could run the recommended pressure, I would just need a tire that measured at least 30mm when installed on those rims. With a 30mm tire, I would be right at the recommended maximum pressure, with 32mm tires I could run in the mid 60s.

How wide are your rims, and how wide do your tires measure when installed on them? If I put a 23mm tire on my old Open Pros, on average the tire is actually going to measure 23mm, and according to Silca's calculator (and my own testing), my ideal pressure would be about 110psi. Put those same tires on my FLO 60s, and now the tire measures 26mm. And according to Silca (and again, my own testing), low 90s is ideal, while 110psi is noticeably slower and harsher riding. Put 25mm tires on the FLOs, and they now measure 28mm, and the ideal pressure drops again to about 80psi. And 110psi rides like crap.

Also keep in mind that tire widths are very inconsistent across brands. I've seen a lot of OEM spec tires that run significantly narrower than labeled, even on wider rims...

"I'm thinking of a number between 1 and 10, and I don't know why!"
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Re: Zipp's Rolling Road and Some Interesting CRR Data [Warbird] [ In reply to ]
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Warbird wrote:
longtrousers wrote:
Warbird wrote:
longtrousers wrote:

5 bars seems to be very low to me, but probably I have to learn and go even lower than the 100 psi I run at the moment.
I'm a bit confused at the moment.
I might try to run 6 bars with conti 5000, I weigh 190 lbs; do you think that would be ok? I would fear flats, especially in a race I rather loose some speed as getting a flat.


I weigh a bit more than you (215 at the moment, have been heavier over the last few years), I haven't run anything above 95psi in years. I can't remember the last time I had a pinch flat. With 23mm GP4Ks (which measure 26mm on my wheels) I'm running around 90psi, and with 25mm GP4Ks (which measure 28mm) I'm running around 80psi. If I were 190 lbs, and/or my tires measured wider, I'd be running even lower pressures...


I remember a snake bite when I had a bit lower pressure, anyway I have 23 mm front and 25 rear and as I said I pump up to 100 psi at the moment. You have 80 psi. Isn't it strange that zipp restricts such:
"The 303 Firecrest has a max tire pressure of 72.5psi (5 bars)"

I mean at least me but even you as a rather low pressure rider could not purchase this rim because you can only inflate it up to 72.5. I think, but correct me if I'm wrong, that also Tom A and Josh at Silca talk about pressures of 100 psi on rough roads. Although lower pressures are even faster but more prone to flats. This max of 72.5 psi just feels strange to me as if it is a typing mistake.


Actually, I could run the recommended pressure, I would just need a tire that measured at least 30mm when installed on those rims. With a 30mm tire, I would be right at the recommended maximum pressure, with 32mm tires I could run in the mid 60s.

How wide are your rims, and how wide do your tires measure when installed on them? If I put a 23mm tire on my old Open Pros, on average the tire is actually going to measure 23mm, and according to Silca's calculator (and my own testing), my ideal pressure would be about 110psi. Put those same tires on my FLO 60s, and now the tire measures 26mm. And according to Silca (and again, my own testing), low 90s is ideal, while 110psi is noticeably slower and harsher riding. Put 25mm tires on the FLOs, and they now measure 28mm, and the ideal pressure drops again to about 80psi. And 110psi rides like crap.

Also keep in mind that tire widths are very inconsistent across brands. I've seen a lot of OEM spec tires that run significantly narrower than labeled, even on wider rims...


Thanks for your thoughts. I looked at Silca tire pressure calculator, but that only seems to work in the "professional" version.

Anyway, I measured my sizes:
Front Tire: 23mm 4000 SII measures 24,2 mm Rim: 808FC 27mm running 7 bar 100 psi at the moment
Rear Tire: 25mm 5000 measures 26 mm Rim: Citec 24 mm running 7 bar 100 psi at the moment

In races I run 25mm 5000 on the front, that should aerodynamically still be ok, staying under 27mm of the rim.
Aerodynamically, the rear tire seems to broad for the narrow citec but I think that does not matter because the rear wheel is hidden anyway on the front by the frame. I weigh 85 kg (187 lbs).
Last edited by: longtrousers: Jul 12, 20 1:28
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
I looked at Silca tire pressure calculator, but that only seems to work in the "professional" version.


You get access to the PRO version by entering your contact info...but if you don't want to do that the results for road bike and Time Trial are below







What I used was a system weight of 207lbs, worn pavement/some cracks, install width of 26mm, and Cat 1/2/3 racing. For my tube setup the calculator comes pretty darn close. For my tubeless setup it misses the mark by ~40%. YMMV

My YouTubes

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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
if I pump up less than 101 psi I get problems wit snake bites (running tubes in my clinchers though, di not have tubeless).

Use latex tubes...
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Re: Zipp's Rolling Road and Some Interesting CRR Data [LAI] [ In reply to ]
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Just an FYI, the full version is actually available without entering an email now: https://silca.cc/pages/sppc-form

Not sure why that specific link is hard to find but I was getting a bit tired of receiving the same thank you email after putting in my info every time haha.

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Re: Zipp's Rolling Road and Some Interesting CRR Data [rruff] [ In reply to ]
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rruff wrote:
longtrousers wrote:
if I pump up less than 101 psi I get problems wit snake bites (running tubes in my clinchers though, di not have tubeless).


Use latex tubes...

I use latex. Yesterday I hit a pothole with 100 psi no problem.
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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longtrousers wrote:
I use latex. Yesterday I hit a pothole with 100 psi no problem.

You need high pressure to prevent pinch flats with latex? I even use them in my MTB and I'm always bouncing off the rim...
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Re: Zipp's Rolling Road and Some Interesting CRR Data [rruff] [ In reply to ]
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rruff wrote:
longtrousers wrote:
I use latex. Yesterday I hit a pothole with 100 psi no problem.

You need high pressure to prevent pinch flats with latex? I even use them in my MTB and I'm always bouncing off the rim...

You have more experience then. I had only once or twice a flat with low pressure, so "n" is too small to make statistical statements, I'm aware of that.
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Re: Zipp's Rolling Road and Some Interesting CRR Data [realbdeal] [ In reply to ]
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realbdeal wrote:
Just an FYI, the full version is actually available without entering an email now: https://silca.cc/pages/sppc-form

Not sure why that specific link is hard to find but I was getting a bit tired of receiving the same thank you email after putting in my info every time haha.


Thanks that works.

I put in my data:
214 lbs system weight;
worn pavement/some cracks
700c/29"
cat1/cat2/cat3 racing
50/50 weight balance

At the moment I have a 23mm in front and a 25mm on the rear. They measure 24 resp. 26.

For 24mm the calculator gives 102,5 psi;
for 26mm 90,5 psi.

I pump at the moment 100psi in both.
So acc. to Silca that's ok whereby I could lower the 25mm a bit.
Last edited by: longtrousers: Jul 21, 20 10:53
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Re: Zipp's Rolling Road and Some Interesting CRR Data [aka_finto] [ In reply to ]
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aka_finto wrote:
longtrousers wrote:
This max of 72.5 psi just feels strange to me as if it is a typing mistake.


Definitely not a typo. The reason is that both the 303S & 303 Firecrest are hookless rims. ETRTO standards only rate any hookless rim up to a max pressure of 72.5psi.

So basically, run higher at your own risk (and no doubt invalidate any warranty cover)

Yes I read a bit and it seems also that these rims require tubeless ready tires (in which you can still have inner tubes I presume) and there is a table which only has 28 and 30 mm tires.
So these rims do not seem to be suitable for the tire sizes and pressures which I am used to.
Curious to see if this concept will get into the other wheels of Zipp too.
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Re: Zipp's Rolling Road and Some Interesting CRR Data [aka_finto] [ In reply to ]
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aka_finto wrote:
longtrousers wrote:
This max of 72.5 psi just feels strange to me as if it is a typing mistake.

Definitely not a typo. The reason is that both the 303S & 303 Firecrest are hookless rims. ETRTO standards only rate any hookless rim up to a max pressure of 72.5psi.

So basically, run higher at your own risk (and no doubt invalidate any warranty cover)

Keep in mind that a huge reason for the push to hookless is because they are dramatically cheaper to manufacture, not because they perform better in any way.

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www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
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Re: Zipp's Rolling Road and Some Interesting CRR Data [RowToTri] [ In reply to ]
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RowToTri wrote:
aka_finto wrote:
longtrousers wrote:
This max of 72.5 psi just feels strange to me as if it is a typing mistake.


Definitely not a typo. The reason is that both the 303S & 303 Firecrest are hookless rims. ETRTO standards only rate any hookless rim up to a max pressure of 72.5psi.

So basically, run higher at your own risk (and no doubt invalidate any warranty cover)


Keep in mind that a huge reason for the push to hookless is because they are dramatically cheaper to manufacture, not because they perform better in any way.


Same shit as pressfit bearings?
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Re: Zipp's Rolling Road and Some Interesting CRR Data [longtrousers] [ In reply to ]
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The SILCA calculator works great on all rims including the 303 hookless, you just have to be sure to use the measured tire width on that rim and not the stated sidewall width.

There also seems to be continued belief that tubeless tires need different pressures than when using tubes, but we just have not been able to show this in any testing we have done. I know Zipp talk about inner tubes fighting against the air pressure by as much as 8psi, which if true would lead to a reduction in pressures when running tubeless, but again, we've tested for this and don't see any change in tire spring rates when comparing tubed vs tubeless, only differences in damping characteristics.

http://www.SILCA.cc
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Re: Zipp's Rolling Road and Some Interesting CRR Data [joshatsilca] [ In reply to ]
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joshatsilca wrote:
The SILCA calculator works great on all rims including the 303 hookless, you just have to be sure to use the measured tire width on that rim and not the stated sidewall width.


I do not remember why I wrote at the time that the calculator is not applicable to the 303 hookless, I played a bit and it works. So I deleted that remark in that post #41.
Last edited by: longtrousers: Jul 21, 20 10:56
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