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PostPosted: Sat Apr 05, 2014 1:15 pm 
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No one says run em at 60psi.. But 80-100 is plenty even for a fat bastard like myself

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PostPosted: Sat Apr 05, 2014 2:20 pm 
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Location: Belgium
Hi,

No wonder you descend so well then. :mrgreen:

In general the better the tub/tyre (high true tpi count) the higher the pressure they can be run on.

Ciao, ;)

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Posted: Sat Apr 05, 2014 2:20 pm 


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PostPosted: Sat Apr 05, 2014 3:58 pm 
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Location: Wherever there's a mountain beckoning to be climbed
mallardducks wrote:
Wolber Invulnerable steel (!) belted tubs for training - anyone remember those?
You mean the Wolber Vulnerable to Steel Belt Flatting the Tire it is Supposed to Protect?


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PostPosted: Sat Apr 05, 2014 7:27 pm 
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project3 wrote:
My previous wheel set was a zipp alu clincher with 23mm conti GP 4000s and now I'm using zipp carbon tubular with conti sprinter gato and I do not feel any diff between clincher and the new tub wheel. All my friends are excited about it and asking me any diff.

I was told that tub suppose to feel lighter and spin faster. My tub front wheel is 115psi and rear is 120 and I'm 56kg.

Psi wrong or the choice of tires for tub ?

To really answer need to know:

-Road conditions
-Type of riding
-Tyre you are using both brand type and profile
and of course the weight you provided, assuming your bike and kit is under 10kg

I WOULD put more pressure in a GP4000 or a Tufo than a 320tpi or silk. Simply because the flex of the tyre. You don't want those stiffer tyres to flex so much.
Those pressures sound like good smooth road TT pressures for your weight. For a RR maybe a wee high, for a crit I'd drop them 10psi and for training/general roads with bumps I'd drop them 20 psi.
Maybe drop pressure 25 PSI if they were 25mm, soft tyre.


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PostPosted: Sat Apr 05, 2014 11:20 pm 
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Posts: 4444
Location: Canada
@project3 & dha, you will have no issue with the glue job based upon a reasonable inflation (which you are using, @dha).

@project3, I am slightly heavier than you. For good weather and on 'normal' (I.e., reasonable asphalt) roads I typically run 100/110ish front/rear. Now, I know that is probably too much pressure and that my wheel is slower than it cold be, but I personally like the feel of a harder tire :noidea: . In the wet, I will run10-15 psi lower.


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PostPosted: Sat Apr 05, 2014 11:47 pm 
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Location: Belgium
Hi,

Quote:
I WOULD put more pressure in a GP4000 or a Tufo than a 320tpi or silk. Simply because the flex of the tyre. You don't want those stiffer tyres to flex so much.


Only on very good to excellent road surfaces though such as a track....

Ciao, ;)

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PostPosted: Sun Apr 06, 2014 6:36 am 
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For a given road would you inflate stiff tyres higher or lower than supple tyres?

I think you want less supple tyres deforming less - and therefore higher pressure.


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PostPosted: Sun Apr 06, 2014 9:48 am 
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Fdegrove I learned how to corner fast racing 250 production motorcycles as a young man
That's where I get it from.. You'd be surprised how far you can lean a road bike over if you have the right tire pressures.. Let's just say I scrub the veloflex labels off my tires with use... :mrgreen:

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PostPosted: Sun Apr 06, 2014 10:16 am 
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Geoff wrote:
dha, you will have no issue with the glue job based upon a reasonable inflation (which you are using, @dha).


Veloflex carbons (glued!) to zipp 202s. I'm 64kg, bike is 6.8.


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PostPosted: Sun Apr 06, 2014 4:35 pm 
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Location: Canada
Nice setup!


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PostPosted: Sun Apr 06, 2014 4:40 pm 
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Zoro wrote:

I think you want less supple tyres deforming less - and therefore higher pressure.


From what I've read I think you have it backwards. You want a supple tire (think 320 tpi) to have more pressure because it is more flexible and can handle bumps, cracks, rocks, and debris without taking away too much energy. The harder less supple tire needs less pressure because it is stiffer and needs less pressure to flex when running over debris and cracks. Remember it takes energy (speed or forward motion) to move the bike up and over debris. This is why the better and smoother the road the higher pressures can be used.

So basically you're trying to find the sweet spot between higher pressure improves rolling resistance and lower pressure improves overcoming cracks and debris.


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PostPosted: Sun Apr 06, 2014 5:31 pm 
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bombertodd wrote:
Zoro wrote:

I think you want less supple tyres deforming less - and therefore higher pressure.


From what I've read I think you have it backwards. You want a supple tire (think 320 tpi) to have more pressure because it is more flexible and can handle bumps, cracks, rocks, and debris without taking away too much energy. The harder less supple tire needs less pressure because it is stiffer and needs less pressure to flex when running over debris and cracks. Remember it takes energy (speed or forward motion) to move the bike up and over debris. This is why the better and smoother the road the higher pressures can be used.

So basically you're trying to find the sweet spot between higher pressure improves rolling resistance and lower pressure improves overcoming cracks and debris.

I meant it the way I wrote it which is the opposite of what I normally read. My goal is using the least energy vs. ride quality. So I should have known what was more important to the rider - and I didn't when I posted. Ride quality is a by-product of a good tyre from my view. Others might say low resistance is a by-product of a good ride.

Thick cases take energy to bend and rebound. An underinflated auto tyre will get warm/hot from the flexing. The cost in lost watts is higher in a stiff tyre than in a supple tyre. So I want them to flex less. So I want more air in them.


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PostPosted: Sun Apr 06, 2014 7:17 pm 
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I do agree that thick cases take energy to bend and rebound, but they also take more energy to overcome cracks, rocks, and other debris. When a rider runs over a small stick if the tire has high pressure the tire will bend less (saves energy) but the rider has is pushed up vertically to get over the stick which requires energy. The energy comes from forward motion and is expelled as vertical energy which slows the rider. If the tire has less pressure it will absorb most of the sticks vertical movement. But this comes as the expense of the loss of rolling resistance from less pressure. If you take two tires, one supple and one stiff, and use ride them at the same tire pressure, the supple tire will absorb more of the vertical movement. The stiffer tire will not flex as much because it is not supple which requires more forward energy to be used to overcome the stick.


That being said I'm speaking purely about which pressures would be faster, without caring about ride quality. If you're goal is least energy vs ride quality I'd guess, assuming you're not a clyde, that you're tires are over inflated if you're running them 130-140 psi.


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PostPosted: Sun Apr 06, 2014 7:51 pm 
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bombertodd wrote:
I do agree that thick cases take energy to bend and rebound, but they also take more energy to overcome cracks, rocks, and other debris. When a rider runs over a small stick if the tire has high pressure the tire will bend less (saves energy) but the rider has is pushed up vertically to get over the stick which requires energy. The energy comes from forward motion and is expelled as vertical energy which slows the rider. If the tire has less pressure it will absorb most of the sticks vertical movement. But this comes as the expense of the loss of rolling resistance from less pressure. If you take two tires, one supple and one stiff, and use ride them at the same tire pressure, the supple tire will absorb more of the vertical movement. The stiffer tire will not flex as much because it is not supple which requires more forward energy to be used to overcome the stick.


That being said I'm speaking purely about which pressures would be faster, without caring about ride quality. If you're goal is least energy vs ride quality I'd guess, assuming you're not a clyde, that you're tires are over inflated if you're running them 130-140 psi.
I understand that and agree - except on many roads 130-140 is not there. Speaking of road riding...Any pressure that causes your tyres to bounce and lose contact with the pavement very often, is too high. It is a calculation/risk that must be made for a race. Any pressure that will reduce friction beyond what is needed to ride, is too high.

Other than those two, for minimal resistance - higher pressure is better. I think we are agreeing based on what you posted.

My reasons are both personal and the experts I've asked and video of experts (I posted video above of the Garmin TDF team mechanic). They ride in the 120ish-130ish range. Francois (FMB and the TT tyres for Sky) says high - the TT bikes with his tyres are run 140-150. The Vittoria site calculator puts many riders over near 130psi.

I would like to see public data that indicates what pressures are too high. I have only seen data to indicate for racing and the TDF - 130 is likely not too high (which was my one line post).


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Posted: Sun Apr 06, 2014 7:51 pm 


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PostPosted: Sun Apr 06, 2014 8:11 pm 
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I'm off to the Redlands Classic today. I'll try to see if I can find some info out there. I found the Vittoria calculator to be horrible. Even 20 psi less than the calculator and my times are slower and I'm bouncing around on bumps and cracks.


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