High Pressure Gravel Tyres

Paddles
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High Pressure Gravel Tyres

Postby Paddles » Thu Oct 11, 2018 10:46 am

Some people say a gravel bike is an "n+1" bike, but I got one to be my "n" bike and replace three others. Anyhow, Plan A was to build/buy a second wheelset so I had a set for the forest and a set for the road, but I've been riding this thing for over a month now with the stock 700c Maxxis 35's and have found them to be pretty good so have come up with a Plan B that is heaps cheaper but still a compromise (much like this bike). I'm chasing some tyres in the 700C 38-40 wide range that can take a bit more pressure. My Maxxis ones are only good for 75psi and I've been through the Maxxis and Schwalbe range and all of their suitable tyres will only take 70-75. I really like the Vittoria Terreno Dry/Zero because they're good for 90psi but I don't know of any others that might fit the bill for me.

I'm a 105kg clydesdale so high pressure and a smaller contact patch is my friend on the road and a taller profile (coming with width) for lower pressure is my friend in the forest. So what tyres have I missed, throw me a bone here :D

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ldrcycles
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Re: High Pressure Gravel Tyres

Postby ldrcycles » Thu Oct 11, 2018 10:56 am

75 pound is already quite a lot on 38-40mm tyres, I'm about 88kg and 50psi was quite firm enough in 40s for me. I could easily have gone down to 40-45 without trouble but I prefer to have plenty of margin re pinch flats. I really don't think there's much to be gained in running more than 75psi in that size tyre.
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Re: High Pressure Gravel Tyres

Postby Mugglechops » Thu Oct 11, 2018 10:57 am

I am running a 700x48 at 45psi at 112kgs on my gravel bike both on the road and in the dirt. High pressures aren't needed they just make it ride rougher.
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Re: High Pressure Gravel Tyres

Postby Paddles » Thu Oct 11, 2018 11:15 am

Interesting, I'm after width at 50psi trail pressures because a taller profile will come with the width. But, the main thing I was after was to make life a bit easier on road loops with friends on road bikes so that's why I was looking for a smaller contact patch. This bike is no slouch and I can comfortably average 26-28km/h over a shorter open road loop with these Maxxis ones at 75, so you guys reckon the extra 15psi (and about 20% less contact patch) will make stuff all difference to me.

I've just looked at the Continental range and they seem to go up to 85psi at 37 wide.

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Thoglette
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Re: High Pressure Gravel Tyres

Postby Thoglette » Thu Oct 11, 2018 12:36 pm

At your weight with 37mm tyres you should be running 50psi on tarmac roads.
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Adding 15psi to your already overinflated tyres will make the ride less comfortable and will significantly increase the risk of a blowout. It might also make you slower.

The problem with your Maxxis is that the construction of the carcass is (relatively) stiff compared to "open tubular" type construction of the best non-tubular tyres.

Products from Challenge (e.g Strada Bianca); Compass and similar should be on your radar, depending on how fast you want to spend.

Panaracer and Conti have some reasonable product too at more reasonable price points but shipping can easily double the nominal price depending on where shop. (My recent experience with them is all in the 630 ETRO size)
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Duck!
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Re: High Pressure Gravel Tyres

Postby Duck! » Thu Oct 11, 2018 1:53 pm

The only thing you'll gain from excessive pressure is risk of blowing the rims apart.....
I had a thought, but it got run over as it crossed my mind.

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Defy The Odds
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Re: High Pressure Gravel Tyres

Postby Defy The Odds » Thu Oct 11, 2018 5:00 pm

Honestly, you are better off with a 2nd set of wheels if it's your only bike.

You actually increase rolling resistance by going to such high pressures.

I have a Toughroad SLR GX 0 and run 40c WTH Nanos have run them as low as 35psi but 40psi is the sweet spot for both road and gravel.

75 would break my back

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Re: High Pressure Gravel Tyres

Postby eeksll » Thu Oct 11, 2018 5:05 pm

on my mavic rims, it has a max recommended pressure for different tyre sizes, the fatter the tyre, the lower the recommended max pressure. From memory its quite low, 40c tyre is around the 55 psi mark.

I suggest OP atleast look into the specs of the rims s/he has.

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Re: High Pressure Gravel Tyres

Postby Paddles » Thu Oct 11, 2018 5:10 pm

I didn't even consider the rims, I'll have to check that out. Alrighty, thanks for all the info everyone. I'm having to do a bit of reading now to figure out this "15% drop" theory :D

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Re: High Pressure Gravel Tyres

Postby Duck! » Thu Oct 11, 2018 7:02 pm

You'll need an assistant to help with measuring the 15%.

Here's the basics: First measure the tyre profile height with no weight on the bike. Measure the gap from the ground to the edge of the rim at the lowest point. Allowing for the thicker tread belt, a 40mm wide tyre may have a profile height around 45mm, but it will vary by the individual tyre model. The measure you come up with is your reference point, so let's go with hypothetical 45mm.

Now sit on the bike, and have your assistant repeat the measurements front and rear. The resulting figure should be 15% less than your reference. 15% of 45mm (.8 x 45) is 38.25. Getting down the fractions of a millimetre is a bit on the tricky side to measure, so as long as you're within a mm or so it'll be OK. Adjust your pressures to achieve the desired figure. Note that due to your weight distribution on the bike, the front will need a lower pressure to achieve the 15% squish.
I had a thought, but it got run over as it crossed my mind.

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Re: High Pressure Gravel Tyres

Postby Mugglechops » Fri Oct 12, 2018 8:09 am

I remember watching Bicyling Australias youtube channel and they reviewed the 3t Exploro with 27.5x2.1 tyres and they said it rode rough on the dirt, which suprised me. I then asked them what pressure they were running and they said 60psi.....
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Re: High Pressure Gravel Tyres

Postby Paddles » Fri Oct 12, 2018 9:48 am

I've done some reading now and the basis of this "15% drop" rule is accepting that a 15% drop is the optimum mechanical profile of the tyre for losses ie a drop of less than 15% gives negligible performance benefit for the tyre and makes the ride more harsh and increases stresses on the tyre/rim. So based on this info the only way to gain a performance benefit and have less losses is to use skinnier tyres at higher pressures and have a potentially harsher ride. Obviously the road surface plays a large part because I'm guessing a rough surface will cause huge losses on a high pressure tyre by trying to deflect the entire load (both rider and bike) instead of simply deflecting the tyre.

So my Plan B doesn't work and the only way to reduce losses is to use a skinnier tyre for smooth surfaces; and for anything less than smooth, using a wider tyre at lower pressures will make stuff all difference. Whilst there's some super smooth roads around here in places, generally our local roads are rough blue metal with repairs all over the place so I'm thinking now it's not even worth my trouble to do Plan A and build a set of wheels for skinny tyres either. So my theory now is I should look at buying some wider tyres with taller profiles that can be more pinch proof in the forest with lower pressures and then for road rides I'll just have to pedal harder to keep up on the smooth stuff and lap up the ride on the dodgy blue metal when the lightweights on their carbon exotica are getting smashed by the bumps. All great info on here, thanks :D

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Re: High Pressure Gravel Tyres

Postby cyclotaur » Fri Oct 12, 2018 11:06 am

I came from road riding to a CX bike then to a 'gravel' bike. It took me a long time to ride lower pressures on the bigger tyres and not think I was losing speed on the road, but the data (including my own) speaks volumes.

I've always ridden 25/28c road tyres anyway at probably 85-90 psi max, and lately a bit less, say 70-75psi. But putting much less pressure in the fatter tyres I run on my alternate wheelsets has taken me awhile.

I now put about 60psi into my big tyres (Schwalbe Marathon Mondial 35 - really a touring tyre) when I pump them up, and then over a few weeks just let them deflate until they start to feel a bit too spongy on the road, at which point I pump them back to 60psi. They get down to about 35-40psi before I feel the need to re-inflate them. In the meantime these wheels float effortlessly over trail bumps, gravel and poor road surfaces. The heavier bike is a little slower uphill on the road but that's due to the extra 2-3kgs more than the tyre pressures, and it descends like a rock. So the gravel bike/tyre combo is no slouch on road rides, and very comfortable, though I recently acquired a 2017 Giant TCR for specific longer, climb-ier road rides.

The sweet spot for the bigger tyres on the g-bike, over all conditions, seems to be around 50psi. For reference I'm about 1.75m/75kg.
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Re: High Pressure Gravel Tyres

Postby uart » Fri Oct 12, 2018 6:04 pm

Paddles wrote:So my Plan B doesn't work and the only way to reduce losses is to use a skinnier tyre for smooth surfaces; and for anything less than smooth, using a wider tyre at lower pressures will make stuff all difference.


Hi Paddles, forget about the whole skinny/wide thing as being the major determining factor in rolling resistance, it's been shown to be flawed logic.

The main components of tyre loss are hysteresis losses in compression/expansion of the tyre casing (not to be confused with compression/expansion of the air inside it). And similarly with deflection of the tread, particularly if you've got knobblies.

So a tyre with subtle sidewalls and casing - one that can be flattened to form a contact patch with minimal force (as measured without any air pressure) - that's what constitutes an efficient tyre. Variation in RR due to width is almost a second order (minimal) effect. Though it's important to choose a width that allows you to run at a suitable pressure for the terrain, both for comfort and to avoid high suspension losses.

The biggest correlating factor in tyre rolling resistance (RR) isn't with width, it's actually with the tyre durability (unfortunately). That's not to say that a low RR tyre can't be durable, if you've got the right materials and construction. But for any given materials and construction type, the more durable that you make it in terms of tread thickness, and sidewall rubber coating thickness, and ply strength and thickness etc, then the higher RR you get.

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Re: High Pressure Gravel Tyres

Postby Paddles » Sat Oct 13, 2018 12:37 pm

So considering a factor of rolling resistance is how much energy it takes to flex the sidewall, is their any data available on rolling resistance for tyres around 700x40C? For example, I used to use 28c Maxxis Refuse tyres at 90-100psi on my old roadie and they were great, I see that this tyre is available as 40c, someone earlier stated that the Maxxis sidewalls were stiff so how would this tyre stack up considering I use the bike on tarmac and gravel track, not muddy mountain bike territory?

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Re: High Pressure Gravel Tyres

Postby Thoglette » Sat Oct 13, 2018 1:23 pm

Paddles wrote: someone earlier stated that the Maxxis sidewalls were stiff

That'd be me. And I said "relatively", and that is relative to the best that you can buy.

The Maaxis Re-fuse 40mm product appear (based on a number of online reviews and comments) to be pretty darn similar to their other re-fuse products. That is: pretty good performance at a reasonable price, with some stiffness penalty from the puncture guard. So if (like me) you've been happy with their other stuff, you should be happy with these to. Note that the 40mm version isn't on special as often as the 23mm!!!

Unfortunately orthodox thought (hello Conti. Schwalbe, Panaracer) is that you can't sell 32mm+ tyres without some sort of puncture guard. So most of the reasonably priced stuff seems to be blessed (or cursed) with this nonsense.

However, if you can spend twice as much, well, there's better options available.
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Re: High Pressure Gravel Tyres

Postby LateStarter » Sat Oct 13, 2018 1:52 pm

"...data available on rolling resistance for tyres..."

https://www.bicyclerollingresistance.com

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Re: High Pressure Gravel Tyres

Postby Paddles » Sat Oct 13, 2018 1:54 pm

Throw some brands/models at me Thoglette.

I checked out the rollingresistance website and there's not much for these types of tyres.

Edit: I've now read Sheldon Brown's tyre page and can recommend it to anyone who wants the info in layman's terms. I just rummaged through the shed and found a pair of Kenda Kwik Bitumen 700x40C with 60TPI so i'm going to chuck them on with 50psi before my next forest ride out of curiosity and see how they go.

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Re: High Pressure Gravel Tyres

Postby Thoglette » Sat Oct 13, 2018 5:29 pm

LateStarter wrote:"...data available on rolling resistance for tyres..."
https://www.bicyclerollingresistance.com

Rolling drum testing is now pretty much discredited.

Paddles wrote:Throw some brands/models at me Thoglette.

As before: Challenge (Strada Bianca) and Compass (Barlow Pass extralight) for starters.

All a bit rich for my purse (sometimes ETRO 630 is a blessing)
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Re: High Pressure Gravel Tyres

Postby LateStarter » Sat Oct 13, 2018 8:14 pm

Thoglette wrote:
LateStarter wrote:"...data available on rolling resistance for tyres..."
https://www.bicyclerollingresistance.com

Rolling drum testing is now pretty much discredited.

I have done enough riding on crappy roads sucking the life from my wheels to agree that "suspension losses" are also important but Mr Heine's blog does not "discredit" drum testing as an indication of rolling resistance. I note Mr Heine has some skin in the game and that his tires don't actually rate as high in the drum test rankings as he might like as they return higher wattages in the tests. The bicycle rolling resistance test does use a slightly rough drum (rather than completely smooth) as a nod towards suspension losses and the WheelEnergy test lab uses both smooth and rough drums. The BRR site has done interesting comparisions between different sizes of the same tire and does support lower RR for wider tires (at the same pressure) but the trend sometimes falls off again with even wider tires in the series.

As there are no free lunches you have to decide if you want the lowest rolling resistance (RR) and accept the more delicate sidewalls and thinner tread with resultant more punctures or you go for stiffer, harder, difficult to penetrate walls and tread, thus less punctures but higher RR or you try to pick something in between. I don't have any spare watts available so tend to something with a lower RR but also hate flats so want some protection too. At the end of 200kms I have to conserve every watt I have.

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Re: High Pressure Gravel Tyres

Postby Paddles » Sat Oct 13, 2018 8:59 pm

I think that's the trade-off Latestarter, finding the right balance of pressure/width/construction to get the right drop and therefore best comfort and ride efficiency. This has a been a good learning experience for me, previously I've only considered the contact patch size to be a direct relationship to losses.

Cheers Thoglette, I'll look those tyres up.

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Re: High Pressure Gravel Tyres

Postby Paddles » Mon Oct 15, 2018 4:14 pm

Ok gents, the feedback is that I've ordered a pair of Soma Shikoro in 700x42C.

I checked out the Challenge Strada Bianca 36, Compass Barlow Pass 38 and also the Panaracer Gravel King Slick 38. I wasn't going to go tubeless yet even though my wheels are tubeless ready and was willing to sacrifice a bit of rolling resistance as a trade for some puncture protection so found the Shikoro was the best compromise.

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Re: High Pressure Gravel Tyres

Postby Thoglette » Mon Oct 15, 2018 4:19 pm

Paddles wrote:Ok gents, the feedback is that I've ordered a pair of Soma Shikoro in 700x42C.

Great. Decision made!

If you don't mind, where did you order them from? In .au or elsewhere?
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Re: High Pressure Gravel Tyres

Postby Paddles » Mon Oct 15, 2018 4:42 pm

I ordered them through my local bike shop because I try to put my cash across their counter as much as I can, but I did a bit of legwork for them.

The Australian importer for the Panaracer products (Soma, Panaracer, Compass) is SCV Imports (they've got a website) and there's an online bike shop in Melbourne called "Commuter Cycles" that sells all these products too.

Thanks for steering me towards the info on tyres, it's been a good learn. I've dismissed going tubeless as a "gimmick" in the past (and seeing a bloke one day a fair way from anywhere with a flat tubeless tyre and no tube didn't help) but I can now see that the benefit is not just pinch proofing your tyre, but also removing some resistance from the sidewall.

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Re: High Pressure Gravel Tyres

Postby hamishm » Mon Oct 15, 2018 5:56 pm

This is actually a great thread for me to hijack and ask.. what pressure should I (of 90ish kg) put in my 40mm Ramblers? I am currently putting in 60 psi which is clearly way too much and I'm getting hammered by the gravel roads. I am not running tubeless.

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