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Advantages of using 20c Front and 23c Back Clincher(24 posts)

Advantages of using 20c Front and 23c Back ClincherPet
Jan 16, 2002 2:55 PM
Hi guys, need your feedback in having 20C Front and 23C back clincher setup....interesting as I notice one of the senior club rider having this setup in the race. By the way is it illegal and the advantages. Any suggestion and experiences related would be greatly appreciated

Thanks,
Pet
Not illegal for racing, we used to run wider in the frontMB1
Jan 16, 2002 3:04 PM
for bad roads. Gave more control and shock absorbation.

Give it a try, see how it works for you.
alot of disadvantagesLewis
Jan 16, 2002 3:56 PM
A 23c has less rolling resistance than a 20c. The last thing you want is LESS contact at the front of your bike. If you're gonna slip do you want the front or rear to slide?

A 20c is slower, has less control and isn't more aero. The only thing is the tire maybe a couple grams lighter.

I can't think of any advantages to this setup.
alot of advantagesWoof the dog
Jan 16, 2002 4:13 PM
A 20c has less rolling resistance than a 23c due to a higher psi rating, such as on Vredestein Fortezza tires.

A 20c is faster at higher pressures, more control and is more aero. It is sometimes 40 grams lighter per tire = 80 grams of rotating weight out of the picture.

You would be able to get away with these tires just fine if you are a light rider and don't do wet criteriums. For crits I had used 20c just fine, but I have to agree that for more control you want a 23c not a thinner one if you must have two different tires on your bike.

I've had plenty of experiences with slideouts. With the front sliding, you hit the pavement and kind of slide with the bike, seems like, while if the rear slips out you fall on your hip and stop in about 5 feet while your bike keeps on going another 10 feet. Your body is probably the most effective way to stop - with its large surface area and that extra stickiness...funny how you never rip your lycra but get deep cuts in your body.

Hope this helps

Woof the dog.
20 vs. 23 - one more timeKerry Irons
Jan 16, 2002 5:01 PM
At equal inflation, a larger tire (of the same construction) has lower rolling resistance due to reduced tread and casing deflection. Narrower tires have higher pressure ratings, which compensates for this. There have been no studies showing that narrower tires at rated pressure are lower rolling resistance than wider tires at rated pressure (or the reverse). Lots of people think that the feel of a harder narrow tire means that it is faster, but testing does not support this. They probably are about the same, but anyone who claims knowledge had better deliver some new data, because I'm not aware that there is any "old" data to support a conclusion. A 20 vs. a 23 is more like 20-25 gm per tire than 40, so the weight savings is minor. Harder tires have worse traction, because higher pressure means a smaller contact patch on the road. All that said, the differences between brands and models is much more significant than the difference between sizes, with the Vred Fortezza Tri Comp rated as the lowest rolling resistance tire in the last test I saw.
20 vs. 23 - one more timeDaniel H.
Jan 17, 2002 5:07 PM
Would you have a link to the rolling resistance test or could you E-mail me the results, I am really interested in the facts.
Thanks
Some dataKerry Irons
Jan 17, 2002 6:05 PM
Here's the information I have. I haven't searched lately so there may be more current information available. The last two figures are a friction coefficient and the number of watts per hour attributable to the tire resistance (I believe at 25 mph). For reference, you're delivering about 300 watts at 25 mph.

Veloflex Record, 700Cx20mm, 150psi, 0.0039, 35W
Veloflex Record, 700Cx20mm, 135psi, 0.0042, 38W
Continental Tempo 19, 28"x19mm, 180psi, 0.0042, 38W
Gommitalia Genio, 700Cx20mm, 135psi, 0.0047, 52W
Vredestein Fortezza Piste, 700cx23mm, 150psi, 0.0050, 55W
Gommitalia Genio, 700Cx20mm, 120psi, 0.0052, 57W
Gommitalia Record, 28"x20mm, 150psi, 0.0057, 63W
Gommitalia Record, 28"x20mm, 120psi, 0.0058, 64W
Vittoria Crono CS 20 *, 28"x20mm, 165psi, 0.0058, 64W
Hutchinson Krono Gold, 700Cx23mm, 125psi, 0.0060, 67W
Vittoria Crono CS 20 *, 28"x20mm, 120psi, 0.0061, 68W
Michelin Axial Pro, 700Cx23mm, 110psi, 0.0063, 69W
Criterium Premio, 28"x18mm, 180psi, 0.0064, 71W
Criterium Premio, 28"x18mm, 150psi, 0.0066, 73W
Hutchinson ORO Servizio Corse, 28"x22mm, 150psi, 0.0067, 74W
Hutchinson ORO Servizio Corse, 28"x22mm, 120psi, 0.0067, 74W
Continental Grand Prix, 700Cx23mm, 125psi, 0.0068, 75W
Hey, that supports what I've saidWoof the dog
Jan 17, 2002 10:03 PM
Kerry, do you agree with my conclusions?

woofman
alot of old wives talesLewis
Jan 16, 2002 7:47 PM
a 20c has a different contact patch that creates more rolling resistance. Deflection, etc (as someone else covered)23c is faster. That is scientific fact that has been published in many periodicals.
When the rear slides, you have a better chance of controling the skid. If the front goes out from under, you really don't have a chance to save it. That is why it doesn't make sense to put a 20c up front.
The weight differences are minimal and not enough to make up for the disadvantages.
20c never has more control and as for being more aero, aerodynamic drag is created mostly by the spokes. Everything else is secondary.
Deep V rims = shorter spokes = slower rotation speed of spokes = more aero. Deep V also smooths airflow from the leading edge (tire) turning it into an airfoil.
ok butWoof the dog
Jan 16, 2002 8:14 PM
I refuse to believe a 23c at 110 is faster than a 20c at 160 psi. I hope you are not implying that either. Hell, who said go and practice maximum leaning on these, but they are perfect for road races IMHO, as for crits, just go with lower pressure. I've ridden, and even won a criterium with ~135psi if not more w/ 20c tires.

By the way, I never saved it sliding with the rear as it happens to quickly...luckily i haven't done too many of these either and not looking forward to.

As for aerodynamics, the tire is a part of the whole leading edge, the deeper the better, the smoother! the better. How much better? i don't know, but 20c gives a smoother transition to the rim. You want a faster time? Do all the small things that will add up to a better result.

Seeeeeeeee!!!!!!!!!!

Woof the dog.
what can I sayLewis
Jan 16, 2002 11:28 PM
23c is faster whether you think so or not. I have no bias except to say it is a physical reality. And yes, a lower psi in 23c is faster than a 20c.
It's like gravity or big sales after Thanksgiving- thats the way life is.

Like I said, the main aero drag is caused by spokes. The tradeoffs of 20c far outweigh any benefit, especially for road or crit racing.

Back to the original question, 20c is a bad idea on the front.
what can I sayWoof the dog
Jan 17, 2002 11:19 AM
could you please show me the numbers, the calculations (at different pressures as well as widths). I'd love to believe in what you are saying, but I need something better than one's word.

Thanx

Woof.
Stop bootstrapping!cyclequip
Jan 18, 2002 6:28 AM
Published figures say for equal pressures the larger tyre has less rolling resistance. If you're basing your argument on the assumption that 20's can be pumped higher (always manufacturer dependant anyway - my Fortezza 20's and 23's both have a 10bar max), then you're on shaky ground. The small differential in max pumping pressures (typically less than 10%) has a negligible effect on the rolling resistance. But then there are the tradeoffs of narrower tyres - comfort and handling go way down.
If 23's were faster...spookyload
Jan 17, 2002 2:41 PM
Then why don't track sprint racers use them. Their races are won and lost within fractions of a second. Same with time trial wheels in the tour. Show me one team that uses 23mm tires during the time trial events. Odd, with all of the high tech stuff LA uses, he doesn't use 23mm either. He spends more time in the wind tunnel than an biker in existance has too.
re: Advantages of using 20c Front and 23c Back ClincherDINOSAUR
Jan 16, 2002 4:23 PM
The advantages are, if you are a bigger rider and subject to pinch flats, a 23 on the rear will be less apt to puncture. A lot of it will depend on your body weight, the types of roads you ride, tire manufacturer, and tire pressure. A 700x23 in one brand, might be equivalent to a 20 in another make, as manufacturers measure their tires diffently. I don't want to get into the rolling resistance debate, a lot of arguments there. I run 23's on the front and rear. I don't race... a 20 for me would mean a harsher ride as I ride mostly chip sealed roads and an al bike...
I'd run a 25 in the rear if I could find one in the brand I prefer....
Pinch flats?spookyload
Jan 16, 2002 5:48 PM
I know you are not talking about the same kind of pinch flats you would get in a mtb tire at 40psi. Do you honestly think a tire at 110psi will pinch flat? It will only pinch flat if you don't check the tire pressure before every ride and let it get down to 70-80psi. If you can pinch flat a tire at 110psi, you need to quit riding your bike off road. Tell me how the extra 3mm of tread will prevent the tube from being pinched between the rim and tire during sidewall deflection. It will blow out the side wall long before it deflects enough to pinch flat.
Pinch flats at 110psiDCP
Jan 16, 2002 6:48 PM
One word "pothole." OK, one word combined with a bit of inattention, an explitive, and an ineffective bunnyhop. Yes, I have done it.
potholes and tailgating cars...guido
Jan 16, 2002 8:31 PM
Yeah, like the one that jumped out from under that big car I was drafting! Flatted both tires. Dented both rims. Bummer.

Interesting discussion. Pet, are you a little woman, say, around 120#? 20C on front, 23C rear, aired up hard, would be nimble and fast for you, I would think. They could handle your "inertial mass." But the heavier the load, the bigger the tires you need, period, in terms of pinch flats, traction, cornering. I shudder when I see a 250# guy hanging over a set of 20C tires. He'll just crush them. Spokes will loosen up. Pinch flats will dent the rim. The little tires won't hold the road very well cornering, or regaining traction after a bump. All that "inertial mass" will easily overcome the tire's grip.

I weigh 155, heavy enough to get pinch flats with 20C tires, but seldom with 25C, never with 28C. 28Cs corner like tubulars, for my weight. But a lighter person would probably love the way 25Cs corner, and so on.
Pinch flats at 110psiDINOSAUR
Jan 16, 2002 9:17 PM
Yes, I have done it also at 110psi. If I ran 110psi I would have a rash of pinch flats at my weight (210). I inflat to 120psi and run this pressure all the time after a lot of experimenting. Body weight and the roads you ride have a lot to do with tire selection and I live in pothole city.
I think it comes down to what works for you....
my head tells me 23c front and 20c back.naff geezer
Jan 16, 2002 8:04 PM
if one were to use different tire widths wouldn't the fatter one up front be better?

more traction and better ride on the braking and turning wheel.
Try this site for information....DINOSAUR
Jan 16, 2002 9:53 PM
http://www.sheldonbrown.com/tyres.html

Scroll down and click on Rolling Resistance...
Thanks for Info...I'm a 23C rider as wellPet
Jan 17, 2002 3:49 AM
Well, I'm a firm believer of 23C for my weight of 160lbs and I just curious with the old preception of tubular is best for competitions, TT or Tri, and if you would observe most of the popular tubular range is at 19C ~ 22C....and that goes the arguement of having a 20C to23C clincher. I've never ride clincher since 5 years back of disaster with my 1 and only tubular wheelset; tons of FLATS. Since than it is 23C Clincher all the way. Guess there's is no right answer, less the differences in road conditions that contribute to the tire selections.
I do it on aero wheelspmf1
Jan 17, 2002 5:38 AM
I think 23's definitely corner better. But if I'm using a set of aero wheels (Spinergy Rev-X), I use a 20 in the front (I rarely use these wheels anymore ... part out of fear). Seems logical to have a skinny tire on the front of a deep dish aero wheel. Since most of the weight goes on the back wheel, it doesn't affect the ride. .
is he a trackie?cyclopathic
Jan 17, 2002 8:25 AM
this is common configuration for track.
the idea is that 20mm is the same size as rim and generates less aero drag.