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Recreational Cyclocross and Gravelbiking This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

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Old 04-19-17, 06:52 PM   #1
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Tire width vs. weight

So I got my one Panaracer GK SK 40mm in today. It measures 41mm on my 22mm ID rims. I was expecting 41mm to "look" wider than it does. That got me wondering...is the difference of 2-3mm between tires even noticeable out on the (gravel) road? I'm thinking about the Maxxis Rambler which weighs in under 400g while this GK weighs 485g.. I would think the loss of ~100g of rotating weight would be much more noticeable (read: faster, nimbler, funner) than 2-3mm of width. Especially at the same PSI. What do you gravel veterans say?
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Old 04-19-17, 07:18 PM   #2
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Well the cross-sectional difference between a 41mm tire (true to size) and a 38mm tire (true-to-size) is 16%.

Whether you like the trade off in size/pressure/handling depends on you and what you ride on terrain and condition wise.
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Old 04-20-17, 08:16 AM   #3
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Well the cross-sectional difference between a 41mm tire (true to size) and a 38mm tire (true-to-size) is 16%.

Whether you like the trade off in size/pressure/handling depends on you and what you ride on terrain and condition wise.
I plan on finding out. If the grip of the 38mm isn't distinguishable from the 41mm tire and it's over 100g lighter then it seems like a no brainer.
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Old 04-20-17, 10:33 PM   #4
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Nominal and actual widths vary. One of my bikes has 700x40 Michelin Protek Cross Max, weigh 1,100 g each, but the tires are closer to 45 wide. The other bike wears 700x42 Continental SpeedRides, under 500 g each, but they're closer to 38 wide. The SpeedRides are lighter, quicker and great all around tires but not as stable as the Michelins on rough gravel, railroad ballast and soft sand washouts.

But I don't know how much of those felt differences are due to width, tread, or the bikes themselves. The Michelins are on a long wheelbase hybrid with spring suspension fork -- it feels very stable in rough gravel and soft stuff. The other bike with the Contis is a rigid mountain bike with geometry closer to a road bike. Quicker overall but demands more attention on tricky terrain.
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Old 04-20-17, 11:04 PM   #5
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One of my bikes has 700x40 Michelin Protek Cross Max, weigh 1,100 g each, but the tires are closer to 45 wide.
Bizarre thing: here, the 700x32 is spec'd as 35-622, the 700x35 as 37-622, and the 700x40 as 42-622. It's like someone somewhere knows that they run wide, but they list them narrower anyway.
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Old 04-20-17, 11:19 PM   #6
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True dat, but I like those Michelins so well I wish I'd gotten the 700x45s when they were available. My long wheelbase hybrid has enough clearance.

BTW, here's a note on Bike Tires Direct for the Michelin Protek tires:
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"The Michelin Protek 700c Tire is available in 700c x 28, 32, 35, 38, and 40mm sizes (ISO 28-622, 32-622, 37-622, 40-622, 42-622). Please note that in the larger sizes the ISO measurement is 2mm larger than the common (700c) size printed on the sidewall."
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Old 04-21-17, 06:27 AM   #7
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I plan on finding out. If the grip of the 38mm isn't distinguishable from the 41mm tire and it's over 100g lighter then it seems like a no brainer.
Depends on the conditions, too. Same deal as with CX, a little bit of water in a short time can completely change a course....or not.

2-5mm of rain on a topographic high-point flat chipped-limestone on dirt, you probably wouldn't notice a difference....if that same path was the low-point in a valley, the water would pool and that gravel path would be mostly mud with embedded limestone chips. Which if you're able to spin up and keep momentum through probably wouldn't matter aside from splatter and minding your steering traction.
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Old 04-21-17, 06:48 AM   #8
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Nominal and actual widths vary. One of my bikes has 700x40 Michelin Protek Cross Max, weigh 1,100 g each, but the tires are closer to 45 wide. The other bike wears 700x42 Continental SpeedRides, under 500 g each, but they're closer to 38 wide. The SpeedRides are lighter, quicker and great all around tires but not as stable as the Michelins on rough gravel, railroad ballast and soft sand washouts.

But I don't know how much of those felt differences are due to width, tread, or the bikes themselves. The Michelins are on a long wheelbase hybrid with spring suspension fork -- it feels very stable in rough gravel and soft stuff. The other bike with the Contis is a rigid mountain bike with geometry closer to a road bike. Quicker overall but demands more attention on tricky terrain.
There you go.
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Old 04-21-17, 06:50 AM   #9
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Depends on the conditions, too. Same deal as with CX, a little bit of water in a short time can completely change a course....or not.

2-5mm of rain on a topographic high-point flat chipped-limestone on dirt, you probably wouldn't notice a difference....if that same path was the low-point in a valley, the water would pool and that gravel path would be mostly mud with embedded limestone chips. Which if you're able to spin up and keep momentum through probably wouldn't matter aside from splatter and minding your steering traction.
Good call. I feel like once the conditions get that bad I'm not going to worry so much about the tire. BUT, I haven't done it yet so I will reserve judgment for when I actually have some experience.
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Old 04-21-17, 10:50 AM   #10
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Wider is better - the monstercross fad gave way to bikes that could take the wide tire the CX bike couldn't.

Enter the adventure/gravel road bike and the rest is history.
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Old 04-21-17, 12:12 PM   #11
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A heavier but more supple tire will be faster than a lighter stiffer tire on most surfaces.

Also, if you're running a smaller tire at the same PSI as a larger tire you're either under-inflating one or over-inflating the other. You want a set percentage of sag, like Berto's 15%, you need to run the smaller tire at a higher pressure - which can reduce grip and comfort. I went back and forth between 38mm width Pari-Motos and 42mm wide Baby Shoe Pass' and the smaller tire was a harsher ride (at the same sag) and felt less sure-footed in rain and rough/loose gravel.

3mm in width is an additional 16% air volume for the larger tire.

https://janheine.wordpress.com/2013/...limeters-make/

FWIW I've never found a narrower, higher pressure tire more fun on gravel or dirt than the wider alternative. Unpaved riding has several considerations more important than weight.
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Old 04-21-17, 12:27 PM   #12
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Bizarre thing: here, the 700x32 is spec'd as 35-622, the 700x35 as 37-622, and the 700x40 as 42-622. It's like someone somewhere knows that they run wide, but they list them narrower anyway.
Schwalbe does the same thing, the ISO spec suggest a wider tire than the vernacular description: "40-622 (700 x 38C )".

I don't get this.
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Old 04-21-17, 01:57 PM   #13
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Wider is better - the monstercross fad gave way to bikes that could take the wide tire the CX bike couldn't.

Enter the adventure/gravel road bike and the rest is history.
Thanks for your input. I'm looking forward to my first proper ride on tubeless 40s.
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Old 04-21-17, 01:59 PM   #14
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Originally Posted by Spoonrobot View Post
A heavier but more supple tire will be faster than a lighter stiffer tire on most surfaces.

Also, if you're running a smaller tire at the same PSI as a larger tire you're either under-inflating one or over-inflating the other. You want a set percentage of sag, like Berto's 15%, you need to run the smaller tire at a higher pressure - which can reduce grip and comfort. I went back and forth between 38mm width Pari-Motos and 42mm wide Baby Shoe Pass' and the smaller tire was a harsher ride (at the same sag) and felt less sure-footed in rain and rough/loose gravel.

3mm in width is an additional 16% air volume for the larger tire.

https://janheine.wordpress.com/2013/...limeters-make/

FWIW I've never found a narrower, higher pressure tire more fun on gravel or dirt than the wider alternative. Unpaved riding has several considerations more important than weight.
This seems to be the prevailing consensus and makes me wonder why no bike manufactures put the biggest tire in their gravel bikes that they can.
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Old 04-21-17, 04:32 PM   #15
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$$$ and weight and they know that a lot of their gravel bikes are only going to be ridden on pavement.

but some do, it just depends on how you define safe clearance or max tire size. If you consider 10mm from tire to frame/fork on all sides there are a few cross/gravel bikes with max tire size from the factory.
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Old 04-21-17, 05:55 PM   #16
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This seems to be the prevailing consensus and makes me wonder why no bike manufactures put the biggest tire in their gravel bikes that they can.
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$$$ and weight and they know that a lot of their gravel bikes are only going to be ridden on pavement.

but some do, it just depends on how you define safe clearance or max tire size. If you consider 10mm from tire to frame/fork on all sides there are a few cross/gravel bikes with max tire size from the factory.
Also the "judge a book by its cover" shopper.

Most people hop on a bike, tool around a parking lot-and declare yay or nay. A bike that feels like a tank in the parking lot will probably not sell well. And large-as-possible tires, let us face it, handle like tanks in a parking lot.
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Old 04-22-17, 04:48 PM   #17
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Also the "judge a book by its cover" shopper.

Most people hop on a bike, tool around a parking lot-and declare yay or nay. A bike that feels like a tank in the parking lot will probably not sell well. And large-as-possible tires, let us face it, handle like tanks in a parking lot.
Good call.
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Old 04-23-17, 03:34 AM   #18
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Most of the YouTube videos I've seen on gravel riding aimed at newbies come from a road bike perspective. To folks coming from road bikes, a 28 or 32 tire probably seems huge, plenty good enough for gravel.

Locally, the riders I see on gravel bikes with wider tires are coming from a mountain bike background. To them a 32 tire probably seems like the minimum width they'd want for gravel.

Coming from a Motobecane with 27 x 1 1/4" tires inflated as high as I dared, I never got the hang of riding gravel 30 years ago when I was younger and avoided it whenever possible. Most of my encounters with gravel or even sand on a turn ended up with me between the bike and the road instead of the other way 'round. The worst was several miles of gravel on a highway under construction in Mexico on a group ride. Felt like I was trying to ice skate while wearing steel wheeled roller skates and simultaneously trying to juggle eggs and dodge land mines. Didn't occur to me to reduce the tire pressure. I didn't know anyone who deliberately rode gravel or who to ask for advice.

First thing I did after resuming cycling in 2015 was to fit the widest tires the rims would handle on my hybrids. Now I'm actually enjoying riding gravel.

I'd rather have wider than 700x40 and 42, but I'd need wider rims, and some way to clear the front derailer on one bike -- the cable clamp bolt would rub wider tires with the derailer moved to the big ring on the triple.

Having seen a friend's bike with Schwalbe Big Ones (29x2.35, I think), those look just about right for gravel to me. Lightweight tires, but probably not the fastest for a really strong and experienced rider who's fast enough on gravel for aerodynamics to be a factor. But it would suit my preference for staying on top of the bike.
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