chuckle

yup :)

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36 kona qualifiers 2006-'23 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
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There is something to be said about chip and seal and none of it is good. Not very scientific but you can feel a quick pick up in speed and your legs having to work less when you are rolling down a section of road recently chip and sealed and then run into a section that was done the previous year.

We train on mostly chip and seal but our tt course are all laid out on asphalt roads. This Sunday our state tt championship will be held on our 40K course. Beautifully flat road with one 180 degree turn at the half and one overpass otherwise completely pancake flat.

Interesting, thanks for sharing all your Crr work. I suspected that chipseal is one of the reasons that the Muskoka 70.3 (and now Ironman Muskoka) course is so remarkably slow. Great to see some data.

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Northern Indiana has a lot of it.

One of the primary reasons I gave up with 23mm tires and 19mm wheels.

i'm a firm believer in the 23mm wheels with 25mm tires and chipseal has ceased to be a numbing issue. It also makes Doc happy as he told me to avoid too much vibration after I lost a kidney.

So the shoulder feels as smooth as previously, just has a new (sticky?) topcoat? If your CdA (or air density) was underestimated for the day, both numbers would be closer to previous, but with a similar delta? It will be interesting to see if time changes the values. Is there a suitable section without chipseal that could be used as a sanity check if you do a repeat test?

Yes, the shoulder is smooth... actually what the whole road was like previously. It didn't sound or feel tacky, but something was going on.

I got the temperature and density and all that stuff down, and I've done a bunch of tests out there previously. Although I have been tweaking my position slightly, I'd be surprised if I was off by more than .005 CdA. And the added drag was equivalent to a CdA increase of .038 and .052.

There's another road close that I can use for CdA testing, so that is what I'll use instead.

Hello,

Since they have been chip sealing a lot of roads around me, and I am wondering if you have re-tested this after some traffic as "smoothed" it out some.

Thanks.

Not actual testing, but I did TTs on that course for a couple years after and was always >1 min slower on similar power. 24 min vs 23 min, so ~4-5%. That was mostly on the shoulder too, but some of it has no shoulder. It may have improved a little, but not a lot.

You can test it yourself! It would be good to get more data on this...

I am wondering if one can test it with a Notio. Thanks for posting this. I was trying to come up with a “factor” to compare older times to a “chip adjusted” course. In looking around 3 to 6 percent looks about right. It’s complicated as some chip is done relatively well compared to the nightmare picture you posted.

The CdACrr app seems quite good for Crr testing, but you have to be at slow speed. I no longer believe that low and high speed Crr are the same... especially on this kind of surface.

have you had a chance 6 years later to to test this on wider tires at low pressure? You originally did this at 120 psi.

Nope, haven't done it. I ran 100spi after the test and was still >1min slower on the course. I run 23mm at 80psi for surfaces like this now, but I don't race on that course anymore.

For rough chipseal I think the fattest and fastest tires that will fit on your bike, at the lowest pressure where you can still avoid flats/damage is a good bet. Tricky though. If I'm sure that there are no potholes or large cracks I might try 60psi with 23s. Fat tires and low pressure might even be best for smooth chipseal.

I would be interested in your original test at 120 psi and then do the exact same test on same sets of road with 28mm in same brand of tire at 60 psi and compare the 4 sets of runs.

Also assume that the course is fairly flat so flexing of the the low pressure tire does not factor in.

The Notio has no estimation for Crr as part of its current features. You could do it with the Chung known elevation method that is described in the slide set that defines and explains the method and the Notio would probably help correct for any non-zero wind conditions.

The Notio does have a built in accelerometer/vibration sensor and it does output a summary graph. We have lots of new chip-seal where I live (yeah) so I will put doing some chip seal testing on the list of things to play with. You couldn’t estimate a Crr, but I would assume that there is a correlation between the amplitude of the “buzz” and Crr. If that is true, you could maybe use that to “tune” for an optimum tire pressure. My guess would be that the tire impedance effect really increases rapidly at some pressure and the optimum pressure is just below that point

Well...the "breakpoint pressure" for a particular setup is a function of road roughness, rider mass, AND speed. Roughness and speed work together to determine the amount of energy being "put into" the system.

So, yes...the losses due to energy making it through the tires and being dissipated in the system can vary by quite a bit, depending on the speed.

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Hey Ron- At last year's CA state championships I tested that exact combination on a roughish chip seal road and got 93psi as the optimum for my front tire -- rear was wider rim and tire. I weigh about 170 (body only) and on my TT rig I'm pretty close to 50-50 weight distribution. Not sure how much you weight but, unless you're a clydesdale, based on my testing experience I'm quite sure that 120 was costing you a fair amount on that road.

Oh, I'm sure. As I stated earlier I dropped down to 100 psi with those tires later. We weigh the same. How did you arrive at 93 psi?

Last race I did in early March was on rough chipseal and I ran Pistas (23mm) at 80 psi. Definitely would have liked more cushion, but there were some sketchy broken patches.

One nice thing about the chipseal around here is that the roads tend to not get large potholes or cracks, so you can lower the pressure quite a bit and still survive. There were some big potholes on the Nationals course in CO Springs though! And I found a really bad one in practice. Tires survived (80 psi there too), but my fork didn't.

Chipseal is really hard to gauge since the mix seems to vary so much. The size of the aggregate, how soft the tar is, how well it is leveled and smoothed, etc. Nationals seemed pretty fast except for the potholes. The north side of Moriarty was refinished a few years ago, with asphalt first, then rough chipseal, then another smooth layer on top. It feels great and seems decently fast. Last summer they refinished the south part. I don't know what the eventual plan is, but it was rough chipseal for the race! Hopefully they finished it like the north side...

Ya, so many good tests *could* be done. Lots of work to do it right however. I don't even have a bike that I can run 28mm tires on. On my old TT bike 23s are close.

That can depend on the tire as well. I don’t know what Conti did to their 700x20 GP4000, but that was an incredibly slow tire compared to the 700x23. Too bad. That tire looked great on the old Specialized and HED trispokes, but it was almost Gatorskin slow.

Rough *ish*? Parts of that course are damn near cyclocross. :) Fwiw, at the same weight as you, I also arrived at about the same pressure you did.

I did what you did -- took my known CdA that I've tested a zillion times and then ran a section of the course over and over at different tire pressures. I found that below about 93 the CRR was pretty flat but above that it went up quickly (was just looking for the exact data but haven't located it). Because that tire is so narrow I wanted to keep it at 93 to avoid pinch flats. FWIW I was very fast for the watts compared with everyone else, and I think part of that was getting the tire pressure right. [Unfortunately I was less than a month off a serious crash so I was far from great form and got 2nd :-(. ]

Ah, nevermind, by CA you meant the other California. Much nicer roads up there.

That's great! I guess you lived close? And trail got the same result (edit: different course I guess...); very nice to have confirmation. How low a pressure did you try and was it significantly smoother?

Adjusting tire pressure to find the optimum isn't so tedious as adding in different sizes. I may get ambitious enough to try that.

I doubt the GP4000 was as good aerodynamically anyway in real conditions vs the wind tunnel. We still have a very good small tire in the Supersonic 20mm. The Veloflex Record 23 isn't much bigger.

I don't worry about flats in TTs. Just stay off the shoulders...