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25mm tire, latex tube, chip seal, psi reducing

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25mm tire, latex tube, chip seal, psi reducing

Old 06-27-19, 08:32 AM
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masi61
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25mm tire, latex tube, chip seal, psi reducing

How low will you go front & rear on your conventional road bike with 700 x 25 tires & latex inner tubes on chipseal?

I got pounded the other night when I ran 94 front & 104 rear on our 60 mile club ride which is about 1/3 chip seal.

My ride is a stiff aluminum bike (Flyte SRS-3) that is overbuilt and on the heavy side, BTW. And I weigh ~#195 & am 5’11” just to give some data.

So tonight I’ll be back doing the same ride. I think I’ll continue to reduce tire pressures to try to get to a happy, less chattery place. Maybe 82 psi front, 90 psi rear. I’m pretty good @ “launching” to avoid direct hits over known expansion joints, larger bumps & road hazards BTW.

My rims are Velocity A23, and tires are Challenge Criterium open tubular.

How low would you go to increase comfort on chipseal before you stop (due to risking snake bite pinctures)?

Last edited by masi61; 06-27-19 at 09:13 AM.
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Old 06-27-19, 08:38 AM
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I've gone down to 70 on 25s. When I weighed 195 I might not have gone below 75.
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Old 06-27-19, 08:51 AM
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There's a huge range in accuracy (and precision) among pumps. What that means is that it's hard to evaluate someone else's post that they run X psi.

Unless you have a way to evaluate your pump and their pump, the best you can do is to hope your pump is consistent, then experiment.
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Old 06-27-19, 09:21 AM
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Originally Posted by RChung View Post
There's a huge range in accuracy (and precision) among pumps. What that means is that it's hard to evaluate someone else's post that they run X psi.

Unless you have a way to evaluate your pump and their pump, the best you can do is to hope your pump is consistent, then experiment.
I’m using a Zefal Husky pump that I’ve had for over 20 years. It has a decent gauge but I don’t rely on that. I purchased a Lezyne digital pressure gauge and have been using it to check pressures before each ride. Since latex tubes typically lose at least 15-25 psi in just one day, using the digital pressure gauge is almost mandatory anyway. It reads out (vertically which is a bit odd) in 1 psi increments. So long as you have your presta valve fully open and push the gauge on squarely (not off to the side) I trust the reading that it gives.

This is whole experiment of running latex tubes & monitoring pressures for what is optimal has been pretty game changing so far for me.

I’ll post an update tonight to document how the 80 psi front, 91 psi rear set up performs...
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Old 06-27-19, 09:42 AM
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Originally Posted by masi61 View Post
I purchased a Lezyne digital pressure gauge and have been using it to check pressures before each ride [...] I trust the reading that it gives.
Very nice. However, you still don't know whether the guys who answer your post are also using a Lezyne digital pressure gauge. Bottom line, you'll just have to experiment.

A couple of years ago I tested two samples of the same model of digital pressure gauge (not a Lezyne, and one was brand new and the other was about a year old). On the same tire in A/B/B/A testing, those two gauges differed by about 4%. That's not much, and since it was only two samples I don't know if that's typical -- but it made me wary of claims about X psi.
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Old 06-27-19, 09:53 AM
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Tires, rims, riding style, everything matters in trying to make comparisons so almost impossible to generalize. But +1 on getting an accurate pressure gauge that you use no matter what pump you use. At 160lb, I run lower pressures on road than anyone I know (Specialized turbo clinchers and butyl tubes). I run tubeless on a TT bike - even lower pressure than the road bike.
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Old 06-27-19, 10:06 AM
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You might try some different tires. You already got a high thread count in the casing which typically, IMO, should give you a better ride and less rolling resistance than tires with a low thread count. However tread compounds, belts and other construction affect that too.

A better model tire from the same mfr or a similar or better model of another mfr might make your ride feel better without having to go really low on the psi.

I swapped to a better constructed tire and actually raised my psi by 30 psi in each tire and still feel it is a more comfortable ride. Luckily most of the roads I ride are smooth.

Otherwise, it's just that stiff bike on that poor road surface.
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Old 06-27-19, 10:15 AM
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Originally Posted by Iride01 View Post
You might try some different tires. You already got a high thread count in the casing which typically, IMO, should give you a better ride and less rolling resistance than tires with a low thread count. However tread compounds, belts and other construction affect that too.

A better model tire from the same mfr or a similar or better model of another mfr might make your ride feel better without having to go really low on the psi.

I swapped to a better constructed tire and actually raised my psi by 30 psi in each tire and still feel it is a more comfortable ride. Luckily most of the roads I ride are smooth.

Otherwise, it's just that stiff bike on that poor road surface.
The Challenge tires seem like they should be pretty plush. My titanium road bike has spoiled me. On that bike Iím running low thread count, 700x23 Tufo Calibra tires with Vittoria latex tubes and they are wonderful !

I think I now am ready to live a little & start phasing out old, reliable Flyte. We have been through a lot together though!
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Old 06-27-19, 10:42 AM
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Yep, the Challenge Crit's do look like they should be a great tire. Step or two up from the Vittoria Rubino Pro III's I been using for the last few years.

Aluminum bikes are supposed to be notoriously stiff. I don't know, I've never road aluminum much, certainly never owned one. I'm on steel which in light bikes is usually springy in the places you want it to be springy.

So yeah, the chip-seal might be a good excuse to spend a good penny on a carbon bike or another titanium. Or spend less on a really good steel bike, though it's hard to find a truly light one anymore.
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Old 06-27-19, 10:46 AM
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I got good results with my aluminum bikes running 90 front and 95 rear. Minimal buzz on chipseal and pretty smooth over expansion joints. Similar rider weight at the time.
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Old 06-27-19, 12:37 PM
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Originally Posted by horatio View Post
I got good results with my aluminum bikes running 90 front and 95 rear. Minimal buzz on chipseal and pretty smooth over expansion joints. Similar rider weight at the time.
This has been my usual experience as well. I think part of the issue for me is that where I normally ride the aluminum bike every week and am used to it, I had set it aside for about 2 or 3 weeks (I was having a chain slippage issue that Iíve since resolved) and solely had been riding the Ti bike.

Iím going to do 60 tonight again and will report back tonight on my tire pressures and what (if any) impact they have on my ride comfort. I have been known to just get achey due to illness (I do currently have a sinus infection & get body aches with that) which impacts my ability to make my body act like a resilient suspension of its own. I like to unweight the pedals and occasional coast while standing in the saddle while my cranks are in the 3 oíclock/9 oíclock position while easy rolling over some of the nastier hazards. This doesnít happen as much when you donít feel well.
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Old 06-27-19, 07:51 PM
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Just got back from the group ride. I went with 81 psi front, & 86 psi rear. We rode 50 miles tonight and avoided the loop with the worst chip seal. The comfort factor was better though. I think I may go even lower next time. Something like 75psi front and 82 psi rear and see how that feels.
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Old 06-28-19, 06:01 AM
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Originally Posted by ldmataya View Post
Tires, rims, riding style, everything matters in trying to make comparisons so almost impossible to generalize. But +1 on getting an accurate pressure gauge that you use no matter what pump you use. At 160lb, I run lower pressures on road than anyone I know (Specialized turbo clinchers and butyl tubes). I run tubeless on a TT bike - even lower pressure than the road bike.
I'm in the same weight category (156 #) on 28mm tires so my experience is quite different than the OP. I got my pressure recommendations from Jan Heine and that has worked well. https://www.google.com/imgres?imgurl...DYAyUQ9QEILjAA
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Old 06-28-19, 08:36 AM
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I'm 6'3", 210 pounds and run 90 PSI both front and back on my bike. Right now I'm on GP4000 tires with Vittoria latex tubes and am happy with the comfort and feel. Mostly smooth roads with some chipseal and I haven't had a flat yet this year.
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Old 06-28-19, 10:48 AM
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I've used 75/85 on my 23s no problem, but my weight is 152.
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Old 06-28-19, 11:08 AM
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Originally Posted by Reynolds View Post
I've used 75/85 on my 23s no problem, but my weight is 152.
This about where I think Iíll settle with my 25mm tires on my slightly wider A23 rims. My weight is between 190 & 195# currently. I think my 25ís might be more like 27ís on the A23 rims, Iím gonna check it with my metric dial calipers..,
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Old 06-30-19, 09:55 AM
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Originally Posted by masi61 View Post
This about where I think I’ll settle with my 25mm tires on my slightly wider A23 rims. My weight is between 190 & 195# currently. I think my 25’s might be more like 27’s on the A23 rims, I’m gonna check it with my metric dial calipers..,
Turns out that the 25mm Challenge Criterium open tubulars on the A23 rims measure at 28.1 mm wide.

I further lowered the pressure for today’s ride to 78 psi front & 84 psi rear. Comfort over bad roads was even better. There seems to be no downside to this. The tires corner well, roll fast and absorb the shock of broken placement much better on my aluminum frame Flyte.
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Old 06-30-19, 11:52 AM
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I recently changed from 23 mm Gatorskin tires and 'normal tire pressures (Velocity A23 rims and 95'ish pounds tire pressure front/back), to Conti GP 5000 tires (23mm) and 75 lbs front, 80 pounds rear. This has made a HUGE difference in my attitude toward really crappy chipseal. While I am still glad to be off it, I no longer change my rides just to avoid the stuff. My weight is around 160 lbs.

I am going to give 25mm tires a shot on the rear where I have a bit of extra room.

BTW, these pressures are verified with an external gauge (with readings that match the gauge on my pump).

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Old 06-30-19, 04:12 PM
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Originally Posted by masi61 View Post
Turns out that the 25mm Challenge Criterium open tubulars on the A23 rims measure at 28.1 mm wide.

I further lowered the pressure for todayís ride to 78 psi front & 84 psi rear. Comfort over bad roads was even better. There seems to be no downside to this. The tires corner well, roll fast and absorb the shock of broken placement much better on my aluminum frame Flyte.
Assuming a ~20 lb bike and tires that measure out to 28mm, you could probably go down a little further on the front. The Dorky Pants tire pressure calculator is recommending 72 front, 89 rear.
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Old 06-30-19, 04:37 PM
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Originally Posted by ThermionicScott View Post
Assuming a ~20 lb bike and tires that measure out to 28mm, you could probably go down a little further on the front. The Dorky Pants tire pressure calculator is recommending 72 front, 89 rear.
Interesting. All my weekend riding companions are riding Continental Gatorskins with butyl tubes pumped up to like 110 psi front and rear.

Iím really delighted about these high thread count Challenge open tubulars on the A23 rims, for my next ride Iíll try bringing the front pressure down closer to the 72 front you mention.
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Old 07-21-19, 02:31 PM
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Today I rode with 72 psi front and 83psi rear on my 25 mm Challenge tires. Nice comfort on our local mixed roads.

The Challenge Criterium open tubular clinchers with Vittoria latex tubes have exceeded my expectations.

All 3 of my weekend riding buddies are riding Continental Gatorskins in 700 x 25 with butyl tubes @ 100 psi or greater. They all have the current wider carbon road clinchers (2 have disc, one have rim brakes). I think they are missing out on a hidden secret and they are operating on an old notion placing avoidance of flats over lightweight/better grip/lower rolling resistance.

I was trying to drop a hint that my lightweight, low pressure setup with my aluminum A23 rims was applicable to their high volume, lightweight carbon clincher wheels. I suggested that the carbon rims they were all riding would be extra sweet with latex tubes, open tubulars and lower pressures. The guys listened - a little. I decided to drop it. The mention of having to monitor tire pressures and pump before each ride (due to the porous nature of the latex tubes) was a deal breaker for at least one of the guys.
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Old 07-22-19, 05:56 AM
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I use butyl tubes in cheap Continental Ultra Sport II -- 25 on my old steel bike, 23 on the '93 Trek 5900. At 150 lbs I can run the pressure pretty low for comfort without risking pinch flats. For the 700x25, usually around 85-90 psi rear, 60-70 front; for 700x23, 90-100 rear, 70-80 front. I could go lower. But I'm mostly guesstimating -- my pump gauge and separate gauge are 10 psi apart. Who knows? I split the difference and go by feel.

As soon as I hit the first rough seams on the nearby access road training circuit I'll know whether I got the pressure right for that day. Getting the lower pressure just right adds a lot of confidence on a fast roller coaster route with some sketchy pavement on fast turns. I really want the pressure just right on that road. There are some patches of unavoidable bad pavement, especially at the bottoms of downhills leading into curves -- typical stuff found on old farm to market roads where the low spots flood regularly. There's a choice between multiple ripples running perpendicular to the direction of travel, or tire-width seams running the direction of travel with an inch high ledge, or just plain ol' fashioned potholes. I aim for the ripples. If the pressure is just right the bike floats across that stuff with nary a bobble. Get it wrong and it's terrifying at 25-35 mph.

Sometimes I'll bleed out a little air on rides when my neck is aching (old injuries). Really helps, especially on longer rides. Can't say I notice any difference in average speed, but I'm already pretty slow. A good day is averaging 16 mph over 50 miles on typical Texas rural roads. A better day is finishing it and not feeling beat up.

One reason I like the cheap Conti Ultra Sports is because they perform as expected based on the rolling resistance review site. The reviewer noted that the Ultra Sport II tires don't suddenly become sluggish at lower pressures, but maintain reasonably low rolling resistance at lower pressure without suddenly turning into glue. Big improvement over other comparably priced tires like the Vittoria Zaffiros, which are slugs at lower pressure, harsh at high pressure and just unpleasant tires. I preferred the discontinued Schwalbe One V-Guards but those were prone to nicks and cuts, although they didn't flat often. But the Conti Ultra Sport II are so good for the money I haven't bothered trying anything else for the past year. Some folks who've tried 'em aren't enthusiastic about 'em. Most folks I ride with use Gatorskins, which feel like lead filled garden hose. I haven't had enough flats with the Ultra Sport II to put up with the disadvantages of heavy duty flat protection.
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