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how low would you go?

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how low would you go?

Old 06-15-21, 08:56 PM
  #1  
Symox
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how low would you go?

I'm experimenting with lower tire pressures. I mainly ride on decent roads (few pot holes that I generally avoid) with 28mm Gatorskins with tubes. I weight 150lbs and the bike is lightish (17lbs? - Its a Specialized Roubaix carbon fiber with rim brakes).

I had been riding 65psi front and 85psi rear but am thinking of going lower.

I tried 65psi and 70psi rear and liked the better cushion.

Not sure how much lower I should go

thoughts?
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Old 06-15-21, 09:52 PM
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You might be able to go lower by 5 or so psi at the rear, maybe 10 at the front. I'd be happy where you are but I'm about 10-12lbs heavier.
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Old 06-16-21, 12:26 AM
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Plug your numbers in at
https://axs.sram.com/guides/tire/pressure

Looks like 64/68 psi is a possibility.
If you can run less rugged tires, you'll probably get a softer ride. I switched away from Armadillos and there was a big difference in comfort.
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Old 06-16-21, 05:25 AM
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The low end is limited by pinch flats - depending on the width of the rim and size of the tires, go too low and hit a bump and the tube gets squashed between the tire and both sides of the rim and you get a "snake bite" flat. For the setup you describe, 60-65 is probably the lowest PSI you'd want to try unless you are going to be riding on really smooth roads.
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Old 06-16-21, 05:54 AM
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I weigh 170 and run 28mm at 65/65 no problem
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Old 06-16-21, 07:05 AM
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I have 30mm tires but same bike and weight. I ran them as low as 40psi, it sure was cushy but they were slower. I also had a couple rim strikes which if I was running tubes would have likely produced pinch flats. Now I inflate to 60/70 and they are probably as low as 50/60 sometimes... for example if it is wet I won't re-inflate.

Agree with above poster that your biggest improvement now would be to get some more supple tires, those Gatorskins are rocks. Also you don't want to go a lot lower on the pressure if you want to avoid pinch flats.. 50/60psi or so at the lowest would be my guess. Its fun to try that out for a bit if nothing else for the learning experience.
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Old 06-16-21, 07:24 AM
  #7  
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Originally Posted by Symox View Post
28mm Gatorskins with tubes. I weight 150lbs ...[snip]... I tried 65psi and 70psi rear
You weigh ~25lbs less than I do so this is conjecture, but I'll bet you could go to 60psi front and back.
But I definitely wouldn't go lower. Of course, I know that I'm personally not a fan of the squishy feeling I get when cornering on low pressure tires, and I also know some other folks are fine with that sensation, so it's all a matter of preference.
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Old 06-16-21, 08:42 AM
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Missing from all of this discussion is internal rim width. It's critical to effective tire volume, which, in turn, is critical to minimum inflation pressure.
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Old 06-16-21, 08:48 AM
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Originally Posted by MoAlpha View Post
Missing from all of this discussion is internal rim width. It's critical to effective tire volume, which, in turn, is critical to minimum inflation pressure.
Good point. I ride on Velocity A 23 rims. Both bike and myself are about the same as yourself. I [ump up to 70F and 65R. If roads are really bad I would add a bit more pressure.
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Old 06-16-21, 09:58 AM
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Originally Posted by MoAlpha View Post
Missing from all of this discussion is internal rim width. It's critical to effective tire volume, which, in turn, is critical to minimum inflation pressure.
Good point.
When I plugged in the numbers at https://axs.sram.com/guides/tire/pressure I used 17 mm as the internal rim width.
That gave the 64/68 psi recommendation
For 15mm rim width, the pressures recommended are 67/71 psi.
So not a big difference, but the trend is clear.

Last edited by VicBC_Biker; 06-16-21 at 10:01 AM.
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Old 06-16-21, 01:56 PM
  #11  
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Rim width is key, as is weight and size of tire. At 175 lbs and 16mm inner width, I run 85/90 on 25s. I could go to 80/85 since my tires are over 27 in actually measurement. With my new rims (if I ever get them) that have 19mm inner width, I'll probably run 75/80. I don't like too low a pressure on fast downhill corners. The Zipp site is what I use to plug everything in. When I switch back to tubeless, I can probably run a lower pressure but 80 is just fine and the bike is pretty compliant on smoother roads anyway.
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Old 06-16-21, 04:53 PM
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I ride at 60 on the rear and 55 on the front with 32's and 25 internal width.
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Old 06-16-21, 06:36 PM
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Try the pressure calculator at zipp.com. it's for tubeless tires that are far more pinch flat resistant.
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Old 06-16-21, 06:56 PM
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Originally Posted by MoAlpha View Post
Missing from all of this discussion is internal rim width. It's critical to effective tire volume, which, in turn, is critical to minimum inflation pressure.
Good point. I'm using Mavic Open Pro rims with 15mm internal width
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Old 06-16-21, 06:58 PM
  #15  
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Just tried a ride with 65 front and 75 rear. Maybe my imagination but it felt slower on some sections. Was plenty comfy though
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Old 06-16-21, 08:24 PM
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Originally Posted by DaveSSS View Post
Try the pressure calculator at zipp.com. it's for tubeless tires that are far more pinch flat resistant.
The OP is using tubes. Why use a calculator for tubeless?
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Old 06-16-21, 08:26 PM
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Originally Posted by Symox View Post
Just tried a ride with 65 front and 75 rear. Maybe my imagination but it felt slower on some sections. Was plenty comfy though
One theory to explain why narrow tires at high pressure 'feel fast' is that we associate the vibrations from the pavement with moving quickly.
I certainly had that feeling when I switched from 23mm tires @95+ psi to 28 mm @ 70-80 psi. But the GPS told me my speed hadn't changed- still as slow as ever....
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Old 06-16-21, 08:36 PM
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I'd tell at you for your 5 hour century while upgrading or buying a new bike.
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Old 06-16-21, 09:47 PM
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Originally Posted by VicBC_Biker View Post
One theory to explain why narrow tires at high pressure 'feel fast' is that we associate the vibrations from the pavement with moving quickly.
Which is weird because I feel the exact opposite.
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Old 06-17-21, 02:54 AM
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Run tubulars and go as low as you want.
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Old 06-18-21, 12:49 AM
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Some tires get significantly more sluggish with higher rolling resistance at lower pressures, while some tires experience only a fairly small increase in rolling resistance. Gatorskins start at nearly 20 watts of rolling resistance at maximum pressure. That's comparable to the Conti Sport Contact II 700x32 tires I run on one of my hybrids. They're oh-kay tires but I wouldn't want them on my road bikes. At maximum pressure they roll just oh-kay but are harsh. At reduced pressure they're sluggish and not much softer because the thick, stiff sidewalls will never make for a supple ride at any pressure. At reduced pressure some puncture resistance tires feel like they're pogoing, especially on choppy pavement on sweeping curves. Not fun.

I usually ride tires with reasonable puncture resistance that have around 15 watts of rolling resistance at my preferred pressures, well below maximum. Very pleasant, and I only need to watch a bit more carefully for road hazards. I've had relatively few flats despite riding areas littered with broken glass from yahoos tossing beer and booze bottles out their truck windows.

One way to improve the feel would be to use latex tubes. They feel a bit lighter rolling, but mostly the latex tubes improve the ride feel. It's more comfortable without lowering pressure to the point where tires feel sluggish or handling suffers. I still carry butyl tubes as spares but prefer latex tubes for my road bikes. Really tames the coarse, jarring chipseal that's become the new normal in my area as cities and states have cheaped out on road maintenance.
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Old 06-18-21, 01:05 AM
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Originally Posted by VicBC_Biker View Post
Good point.
When I plugged in the numbers at https://axs.sram.com/guides/tire/pressure I used 17 mm as the internal rim width.
That gave the 64/68 psi recommendation
For 15mm rim width, the pressures recommended are 67/71 psi.
So not a big difference, but the trend is clear.
It makes as much, if not more, difference what type of tyre casing you plug in.

Choose "thin" and the result is 77/82 while "reinforced" comes out to 67/71.

Ppl tend to forget this when they bag on the ride quality of reinforced tyres.
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Old 06-18-21, 07:27 AM
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not on a road bike, 21 front 25 rear, but yeah don't want to go too low



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Old 06-18-21, 02:58 PM
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Originally Posted by Symox View Post
I'm experimenting with lower tire pressures. I mainly ride on decent roads (few pot holes that I generally avoid) with 28mm Gatorskins with tubes. I weight 150lbs and the bike is lightish (17lbs? - Its a Specialized Roubaix carbon fiber with rim brakes).

I had been riding 65psi front and 85psi rear but am thinking of going lower.

I tried 65psi and 70psi rear and liked the better cushion.

Not sure how much lower I should go

thoughts?
I'm 210 and I ride Vittoria Corsa Control 2.0 at 68/70 in a 28c tire and love the plush, fast ride. So I'd say you're still way too high.

Silca has a terrific inflation calculator that takes into account road, weight, tire size when mounted, and riding style in the advanced version. It's from data accumulated over all their time working with World Tour teams on inflation. Check that out. For those weights, the calculator says a lot closer to 71/72 psi front/rear.
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Old 06-18-21, 03:20 PM
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Originally Posted by JohnJ80 View Post
I'm 210 and I ride Vittoria Corsa Control 2.0 at 68/70 in a 28c tire and love the plush, fast ride. So I'd say you're still way too high.

Silca has a terrific inflation calculator that takes into account road, weight, tire size when mounted, and riding style in the advanced version. It's from data accumulated over all their time working with World Tour teams on inflation. Check that out. For those weights, the calculator says a lot closer to 71/72 psi front/rear.
It's tough to know what factors are most important in deciding tire pressure. The Silca calculator doesn't differentiate between tubed and tubeless, and doesn't have sidewall and internal rim width options.
The Silca calculator also demands your email address if you want to use the available choices for pressure calculations.

I think a lot of riders just use the online calculators to get a 'starting point' for further experiments?

Last edited by VicBC_Biker; 06-18-21 at 03:24 PM.
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