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25mm to 28mm road tire

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25mm to 28mm road tire

Old 07-07-19, 01:04 PM
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sirjag
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25mm to 28mm road tire

So changed out the tires on my new Contend SL1 Giant bike...Man the bike should have came this way in my opinion. I ran 95-100lbs in my 25mm, and just a tad less in the 28s at 95lbs max.

The drive is so much smoother and less harsher on my ass and hands! The bike feels more planted and secure at 25-35mph as well.

I hear that 25mm tires and smaller go faster downhill...but also that very few people are elite enough to notice the difference....

Can I have some opinions and possible explanations of why the 28s feel so much nicer?>

thanks yall,
JAG
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Old 07-07-19, 01:12 PM
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I've gone from 23's, to 25's, and now 28's. I won't look back.
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Old 07-07-19, 01:23 PM
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Originally Posted by sirjag View Post
Can I have some opinions and possible explanations of why the 28s feel so much nicer?
Wider tires tend to be taller, so they have more "travel" as a suspension mechanism, allowing you to pump them squishier without increasing the risk of bottom-outs. They also tend to give a better-behaved and less-squirmy ride than a narrower tire, if both are pumped to the same degree of compliance.

If you upgraded to a suppler and higher-performance tire, this could also have a lot to do with it. If you have two tires of the same size and you pump them to the same pressure, but one is much stiffer than the other, the less-stiff tire will tend to be more compliant on road irregularities.
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Old 07-07-19, 01:25 PM
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Originally Posted by HTupolev View Post
Wider tires tend to be taller, so they have more "travel" as a suspension mechanism, allowing you to pump them squishier without increasing the risk of bottom-outs. They also tend to give a better-behaved and less-squirmy ride than a narrower tire, if both are pumped to the same degree of compliance.

If you upgraded to a suppler and higher-performance tire, this could also have a lot to do with it. If you have two tires of the same size and you pump them to the same pressure, but one is much stiffer than the other, the less-stiff tire will tend to be more compliant on road irregularities.
thank you Sir. My two tire types were identical, just a sizing difference. Both the standard Giant road tires...

JAG
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Old 07-07-19, 02:44 PM
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Originally Posted by sirjag View Post
...and just a tad less in the 28s at 95lbs max.
You should be able to get away with lower pressure unless you're a really big/heavy person.

But yeah, slightly larger and lower pressure tires are great,
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Old 07-07-19, 03:29 PM
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Originally Posted by WhyFi View Post
You should be able to get away with lower pressure unless you're a really big/heavy person.

But yeah, slightly larger and lower pressure tires are great,
Im 5'11" at 205lbs! I feel like a phat ass though! Is 200lbs considered heavy in the cycling world?

JAG
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Old 07-07-19, 03:37 PM
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Originally Posted by sirjag View Post
Im 5'11" at 205lbs! I feel like a phat ass though! Is 200lbs considered heavy in the cycling world?

JAG
I'm 5'11" 190... but even at 215, I was running 65f/70r psi in 30mm tires.

In terms of road cycling, yes - 200lbs is heavy.
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Old 07-07-19, 04:08 PM
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My bike came from the factory with 25mm tires. I switched to 28mm. Definite improvement in comfort, handling, and speed. I really would like 32mm but the rear wheel tire doesn't have enough clearance for the frame, so I'm stuck with 28mm. ( 32mm will fit on the front but lightly brushes up against the frame so I'm stuck with 28 there too.
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Old 07-07-19, 04:57 PM
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There are numerous charts with recommendations on the web for various tire widths and carrying capacity. I've been using this one with good results. https://www.google.com/imgres?imgurl...DYAyUQ9QEILjAA
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Old 07-07-19, 05:01 PM
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But that chart shows pressures that is below the 85-125psi stamped on both the rim and tire.... Mine are tubless by the way..if that matters.
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Old 07-07-19, 05:31 PM
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The pressure stamped on the tire has a lot more to do with legal issues and a whole lot less to do with performance.

The pure pressure vs weight charts also don't take into account rim width which has a big impact on tire profile. The wider the rim, typically, the higher the tire sits from the rim. The higher it sits from the rim, the more protection it provides to the rim from road defects. The more protection implies you can lower the pressure accordingly. Ride quality improves and to a large degree, speed improves unless you are riding on a track with almost perfectly smooth surfaces.

I've found the charts that Enve provides on their wheels to be pretty good for rim width in general (here's an example). I've also found the guidance that Josh Poertner has given in his "Marginal Gains" podcast to be helpful (Josh is the owner of Silca and formerly the technical director for Zipp). I think it's this podcast where he comes up with some really practical way to get your tire inflation correct. Surprisingly, it's lower - not higher - than you think.

There's also a really interesting article that Josh wrote about the first win of Paris-Roubaix on carbon rims and what went into that. A lot of it has to do with pretty precise understanding and setting of tire pressure. One of the big takeaways from their research was that seemingly small differences in pressure can have big impacts and it became essential to measure it accurately. When they looked at their pumps when results are wildly inconsistent, they found that they had more than a 12psi variance between pumps and that made the difference between results that mattered and broken rims.

So for me, I've found that I need to adjust pressure based on my tire size, rim width and rider weight.

J.
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Old 07-07-19, 05:41 PM
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Originally Posted by JohnJ80 View Post
The pressure stamped on the tire has a lot more to do with legal issues and a whole lot less to do with performance.

The pure pressure vs weight charts also don't take into account rim width which has a big impact on tire profile. The wider the rim, typically, the higher the tire sits from the rim. The higher it sits from the rim, the more protection it provides to the rim from road defects. The more protection implies you can lower the pressure accordingly. Ride quality improves and to a large degree, speed improves unless you are riding on a track with almost perfectly smooth surfaces.

I've found the charts that Enve provides on their wheels to be pretty good for rim width in general (here's an example). I've also found the guidance that Josh Poertner has given in his "Marginal Gains" podcast to be helpful (Josh is the owner of Silca and formerly the technical director for Zipp). I think it's this podcast where he comes up with some really practical way to get your tire inflation correct. Surprisingly, it's lower - not higher - than you think.

There's also a really interesting article that Josh wrote about the first win of Paris-Roubaix on carbon rims and what went into that. A lot of it has to do with pretty precise understanding and setting of tire pressure. One of the big takeaways from their research was that seemingly small differences in pressure can have big impacts and it became essential to measure it accurately. When they looked at their pumps when results are wildly inconsistent, they found that they had more than a 12psi variance between pumps and that made the difference between results that mattered and broken rims.

So for me, I've found that I need to adjust pressure based on my tire size, rim width and rider weight.

J.
Thank you Sir. So i need to experiment with different pressure and go with what feels the best while not breaking the edge seal of the tire (too low pressure).

JAG
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Old 07-07-19, 06:07 PM
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Originally Posted by sirjag View Post
So changed out the tires on my new Contend SL1 Giant bike...Man the bike should have came this way in my opinion. I ran 95-100lbs in my 25mm, and just a tad less in the 28s at 95lbs max.

The drive is so much smoother and less harsher on my ass and hands! The bike feels more planted and secure at 25-35mph as well.

I hear that 25mm tires and smaller go faster downhill...but also that very few people are elite enough to notice the difference....

Can I have some opinions and possible explanations of why the 28s feel so much nicer?>

thanks yall,
JAG
My road bike came with 25mm tires, and because thinner must be better eventually I migrated to 23s. ...for awhile.

I've been using 28mm tires on my road bike for a couple years now, and see no reason to go back to skull-rattling days of old. A Cannondale Synapse with some forgiving rubber on it is a pleasure to ride. On my commuter I use 32mm Conti GP4Season tires, and love every mile I put on them. They're the only thing between the road and the stiff Cannondale Quick CX frameset.

Frankly, if my road bike could fit 32s, I wouldn't be opposed to putting some 32mm GP5000 tires on it. But, alas, the generation of Synapse I have wouldn't accommodate any tire wider than about 28mm. When the day comes that I decide to upgrade to a newer CF Synapse I'll give strong consideration to 32s (but may end up with 28s anyway, we'll see).
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Old 07-07-19, 09:34 PM
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I prefer 28mm tires but the vortex can only fit 25s with a thin aftermarket carbon RD mount. Otherwise I agree 28s are great wish my ride can fit them but 25 conti gps are awesome and feel great still and I find a carbon wheel set really helps soak up the bumps as well
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Old 07-07-19, 09:57 PM
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Tire air volume is proportional to the cross section circle. Area of a circle = pi * radius squared.

3.14 * (25/2)^2
vs
3.14 * (28/2)^2

The 28 has 25% more air volume (!), and a few mm of extra travel.
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Old 07-07-19, 10:17 PM
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I ran 23s on my Kona JtS for a few years, and tens of thousands of miles.
Sure it was fast enough, but wow... rough roads really made it all the way through my bones.

I still love the bike, though, and have 700x35 tires on it now. VERY nice. Might be a bit slower than it could be for road rides, but I'll probably go to 28s at some point in the near future.
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Old 07-08-19, 04:12 AM
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run 23's, 25's and 28's on the various bikes. if i'm doing serious paved climbing or a 115+ century ride, prefer the 23's,
if i'm doing any significant portion of the ride on dirt/gravel (10+ miles), i'll take the 25's or 28's. urban rides, prefiero the 25's.
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Old 07-08-19, 05:23 AM
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Originally Posted by JohnJ80 View Post

I've found the charts that Enve provides on their wheels to be pretty good for rim width in general (here's an example).
J.
Not sure I understand how Enve, as a performance-based marketer, derives their charts though. Eg. looking at an SES 3.4 chart.. 25mm tire, 150lb rider, inflation of 60psi. Ok, but how do you reconcile this with eg. data from BicycleRollingResistance, which will show better performance at higher PSIs than 60. Scroll about halfway down: Conti 5kTL
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Old 07-08-19, 05:48 AM
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In 2017 I bought an old classic racing bike from a bike mechanic who had set the bike up with 28mm tires. I did the Eroica California ride on that bike (1973 Windsor Pro) when it was still in Paso Robles California. I have been slowly changing all my bikes to wider tires since I got that bike and experienced the ride difference. My Super Mondia allows for the wide 35mm tires that I put on and I love the ride on that bike. Loose sand or gravel on the road are no longer a problem , and , I have scored my quickest Strava time on that bike. Joe
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Old 07-08-19, 06:36 AM
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Originally Posted by sirjag View Post
Im 5'11" at 205lbs! I feel like a phat ass though! Is 200lbs considered heavy in the cycling world?

JAG
170 lbs is heavy in the cycling world.
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Old 07-08-19, 06:43 AM
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True, but Armstrong was 170 when he won the World Championships in 1993. He simply rode away from Indurain, Fondriest, Lauritzen, Massen, Riis, Ludwig, and the world's best riders, and they could do absolutely nothing to catch him.



Of course, he was an even better rider after he lost 20 lbs.
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Old 07-08-19, 06:57 AM
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Originally Posted by sirjag View Post
Im 5'11" at 205lbs! I feel like a phat ass though! Is 200lbs considered heavy in the cycling world?

JAG
I'm 6' 185lbs, and continually get called a big guy in cycling circles, it cracks me up (having lost almost 100lbs, I'm def not as big as I used to be! lol). But when the guys standing around me are 120-150lbs, I guess that does make me big.

They might get me on the climbs, but I always catch them on the other side.
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Old 07-08-19, 06:58 AM
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Originally Posted by sirjag View Post
Im 5'11" at 205lbs! I feel like a phat ass though! Is 200lbs considered heavy in the cycling world?

JAG
Well, the heaviest pro cyclist is 203 lbs, but he is 6'6" tall.
So if you just grow 7", you'll be good.

https://www.procyclingstats.com/rider.php?id=141166
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Old 07-08-19, 07:58 AM
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My '89 steel road bike has gone from 700x18 to 23 to 25 tires, and I'd be using 28s if they cleared the chainstays. In actual practice the cheap 25s are as fast as my more expensive and lighter 23s on our rough rural chipseal. Lots more comfortable too. I weigh 150 and run 'em around 80-85 psi rear, 70 psi front. I could probably go lower.

If we had mostly smooth asphalt, sure, I'd stick with good quality 23s. But there's no advantage where I ride. Rural chipseal is making gravel and cross bikes more practical, or the bikes designed for the cobbles. I wouldn't buy another traditional road bike. No point now the way our roads are maintained.

For us mere mortals, I haven't seen that size is a big factor among the guys I ride with. We're mostly 50something and older. I look like I'm the fittest but the bigger guys with beer bellies often outlast me beyond 50 miles. I'm only a little faster on climbs, but overall it doesn't help much.

Indurain was always a big guy, even bigger than Merckx, and probably weighs about 200 lbs now although he looks to be in good shape in his 50s. He still rides and climbs the same, like a plow horse chugging along calmly, rarely getting out of the saddle. There are some product placement videos of him on YouTube, but worth watching anyway. Inspiration for bigger and sorta-older guys.
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Old 07-08-19, 08:10 AM
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28mm Panaracer Paselas and Gravel Kings run narrow on my various rims, around 26mm actual. I have several road bikes that won't accept other 28mm tires, but the Panaracers clear fine, but with no room to spare. I've found that these Panaracers are the best tires for frames that won't normally clear other 28's.
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