QUESTION: Rat Trap Pass

[Kellie]

What psi are people running with this tire on street/hardpacked dirt, tubeless? Thanks.

[Singlespeed Johnny]

no more than 40psi. depending on your weight, you'd probably be able to run as low as 28 or so.

[Rod Holland]

30 front, 35 rear, on a mix of pavement and gravel/dirt/roots/rocks.

rod

[Patrick Moore]

30 to 40 seems high for a 50+ mm tire. I run my 50 mm labeled/51 actual Furious Freds (tubeless) at about 23-24/26-27 for a mix of pavement, sand (up to 3"), and roots and small rocks, and that seems firm.

Note that the F Freds are considerably lighter (360 grams consistently, at least the 3 or 4 I've weighed) than the RTPs, too (and the FFs are 700C tires).

And even 23 seems high compared to the 15/18 and as low as 12 in front that I used in 60 mm Big Apple Liteskins, though these had tubes. Same conditions, though man! 15/18 psi was wonderful in sand! The FFs require more pressure to prevent sidewall flop.

How do you (plural( decide what pressure to choose? 

[Braxton Colagross]

I run about 19 or 20 psi in the front and 22 or so in the back.

[Clayton]

25 psi.

Clay

[Jon BALER]

The schwalbe big ones are a similar tire, but 700c.  I run them around 25 psi on the road (slightly less in front, and slightly more in the rear), and I weigh 220 lbs.

[Philip Kim]

35 rear 30 front on atlas rims converted tubeless with load for EL casing. Ran a little less on standard - 30 rear 26-28 front.

patrick, compass tires require a bit more psi IME than schwalbe tires due to the thin sidewall casings. 

[Patrick Moore]

I doubt that the RTP casings are thinner than those of the F Freds. If anyone can correct me, I'll stand corrected!

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[Philip Kim]

ahh i was just noting why you may be seeing some higher psi run with RTPs from other, as 30-40 psi is a bit high for a ~50mm tire.

On Wednesday, July 5, 2017 at 2:52:18 PM UTC-4, Patrick Moore wrote:

I doubt that the RTP casings are thinner than those of the F Freds. If anyone can correct me, I'll stand corrected!

On Wed, Jul 5, 2017 at 10:25 AM, Philip Kim <phili...@gmail.com> wrote:

35 rear 30 front on atlas rims converted tubeless with load for EL casing. Ran a little less on standard - 30 rear 26-28 front.

patrick, compass tires require a bit more psi IME than schwalbe tires due to the thin sidewall casings. 

On Wednesday, July 5, 2017 at 9:01:20 AM UTC-4, Patrick Moore wrote:

30 to 40 seems high for a 50+ mm tire. I run my 50 mm labeled/51 actual Furious Freds (tubeless) at about 23-24/26-27 for a mix of pavement, sand (up to 3"), and roots and small rocks, and that seems firm.

Note that the F Freds are considerably lighter (360 grams consistently, at least the 3 or 4 I've weighed) than the RTPs, too (and the FFs are 700C tires).

And even 23 seems high compared to the 15/18 and as low as 12 in front that I used in 60 mm Big Apple Liteskins, though these had tubes. Same conditions, though man! 15/18 psi was wonderful in sand! The FFs require more pressure to prevent sidewall flop.

How do you (plural( decide what pressure to choose? 

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[Mark in Beacon]

I've always been slightly curios as to the accuracy of the tire pressure gauges. What are people using, and how are they calibrated? I'm just guessing, but the numbers reported here could be closer, or further apart, or who knows. I know people say there is a smaller optimum range with these, and you need to keep the sidewalls from collapsing, but I think once you ride them a bit it doesn't matter too much.

I've been riding my RTP bike almost exclusively for the past few months. I put some air in, give it a squeeze, make sure not to hard or soft, and go. Then when they start to get bouncy, I put some more in.

Just checked now, and according to the gauge on my Orange pump from Nashbar, I had 20 front, 28 rear. Did a long road ride with lots of climbing yesterday, felt pretty good, but a bit of bounce, so I'll add a few hits. I weigh about 170, and the bike, with handlebar bag and back tool bag, is around the 30pd zone.

I had a mini gauge that came with a flat tire repair kit (that came with a used bike I bought) but I seem to have temporarily misplaced it. I do have a 2nd pump in my car, will check with that and compare.

Anyway, great, fun tire. Also, I have hat zero flats in all kinds of conditions. I run with tubes and a few squirts of orange seal, per Patrick. Knock wood.

[Patrick Moore]

Digital gauge for bike tires -- forget make, but said to be accurate to a fraction of a lb per sq inch. I weigh 175.

I'm not disagreeing, just wondering why RTPs need such high pressure when at least one considerably lighter tire needs considerably less,

[Kellie Stapleton]

The tire max written on the tire is 55, on the website product description says if it’s too bouncy the pressure is too high.

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[Kellie]

Like your photos. Thanks for sharing.

[Philip Kim]

Use a track pump and double check with a tire pressure gauge (https://www.amazon.com/gp/aw/d/B0011W6M4Y/ref=mp_s_a_1_3?ie=UTF8&qid=1499308886&sr=8-3&pi=AC_SX236_SY340_QL65&keywords=bicycle+tire+pressure+gauge+presta&dpPl=1&dpID=41%2B3C1ZlX1L&ref=plSrch)

[Mark in Beacon]

You would consider 20/28 for relatively smooth road riding high pressure?

[Mark in Beacon]

I get what feels like bounce feedback when the pressure is too low. Maybe what I'm calling bounce is really...squish? I think I know what they mean, the kind of bounce when the tire is overinflated, but I only pumped them that high to seat initially. I will try a little ride with 50 psi for the sake of science. (Re: photo. Thank you.)

[iamkeith]

Yeah, Mark - i think you want you let air out, not add it!

I just took mine off my all rounder and went back to the original 1.75 compass tires because it was so tedious to tune the bounce out. But, in my case, it was the rim's fault - not the tire's.

Normally, the way to get a high-volume, supple tire adjusted properly is to pump until it just starts to get bouncy, and then let a bit of air out. The smaller the casing, the more forgiving and bigger the acceptable range of pressures.

So, for instance, A 4.5" fat bike tire (on dry, summer trails) will have to be within about 1/2 psi of optimum, in order to both steer properly at one end, and to not bounce you around like a pogo stick at the other.

A 2.75 - 3" plus-sized tire might have a range of 1 1/2 to 2 psi that works and, usually, the lowest you can go without getting pinch flats is the best within that range. There is negligible if any efficiency gain from adding air beyond that, but there is noticable degredation of traction and comfort for every psi over the minimum needed.

Following these, the 2.3" RTP SHOULD have a workable range of maybe 3 psi or so, for any given load? But the caveat is that this would require a rim that is of adequate width to support the tire. I didn't have that with my 519 mavics, so i had to be very careful not to let it get so low that the tire would roll off the rim. Unfortunately, at that point, it was too easy to make it start bouncing.

When i did run them at proper, low pressures, they were sublime - but i was always nervous about cornering, and rolling a bead.

For me, at 200lbs, i think something like 23 rear / 19 front would be ideal. (As noted, i mostly did/do it by feel) BUT... that would be with a well-matched rim of at least 25-30 mm inside dimension. The wider the rim, the lower you can go.

On the other hand, the smoother and more featureless the riding surface, the higher the pressure you can get away with, without feeling the bounce or realizing you're over inflated. But that doesn't mean it's optimum, and i dont think there's an efficiency or tread longevity benefit to having more pressure.

[Patrick Moore]

On these tires, yes. It's actually 23 to 28, and that's front versus rear. 

I consider this the best pressure range for sidewall support and cushioning on combined dirt and pavement; if I rode dirt exclusively, I'd probably drop the pressure a few psi -- indeed, perhaps 20 f and 23 rear. If I rode these only on smooth pavement - but I wouldn't -- I'd see no reason to run them higher. The tires don't bounce or feel squishy.

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[Patrick Moore]

And Keith's remark on rim width reminds me of something very pertinent; mine measure IIRC about 27 mm inside. Narrower rims of course would require more pressure, especially with such thin sidewalls as on the RTP and F Fred.

On Thu, Jul 6, 2017 at 10:12 AM, Patrick Moore <bert...@gmail.com> wrote:

On these tires, yes. It's actually 23 to 28, and that's front versus rear. 

I consider this the best pressure range for sidewall support and cushioning on combined dirt and pavement; if I rode dirt exclusively, I'd probably drop the pressure a few psi -- indeed, perhaps 20 f and 23 rear. If I rode these only on smooth pavement - but I wouldn't -- I'd see no reason to run them higher. The tires don't bounce or feel squishy.

[Clayton]

I forgot to put my weight on my response. I weigh 147 lbs. and run my pressure at 24-28 psi (in general). There are so many factors to consider when deciding on a tire pressure. How bad is the riding surface do you ride on? How aggressive are you in corners? (Don't want to roll the tire off the rim) What kind of ride feel do you prefer?  How much do you weigh? 25 psi is as low as I can go and still have some confidence I won't roll the tire off. When riding in dirt, I run around 20psi. If I had wider rims, I'd run lower air pressure. 

Clay

On Tuesday, July 4, 2017 at 5:05:53 PM UTC-7, Kellie wrote:

[Mark in Beacon]

Am I confused or are you confused? My math shows 20 front 28 rear to be lower or equal to 23/28, not higher.

On Thursday, July 6, 2017 at 12:12:53 PM UTC-4, Patrick Moore wrote:

On these tires, yes. It's actually 23 to 28, and that's front versus rear. 

I consider this the best pressure range for sidewall support and cushioning on combined dirt and pavement; if I rode dirt exclusively, I'd probably drop the pressure a few psi -- indeed, perhaps 20 f and 23 rear. If I rode these only on smooth pavement - but I wouldn't -- I'd see no reason to run them higher. The tires don't bounce or feel squishy.

On Wed, Jul 5, 2017 at 8:50 PM, 'Mark in Beacon' via RBW Owners Bunch <rbw-owne...@googlegroups.com> wrote:

You would consider 20/28 for relatively smooth road riding high pressure?

On Wednesday, July 5, 2017 at 6:56:02 PM UTC-4, Patrick Moore wrote:

Digital gauge for bike tires -- forget make, but said to be accurate to a fraction of a lb per sq inch. I weigh 175.

I'm not disagreeing, just wondering why RTPs need such high pressure when at least one considerably lighter tire needs considerably less,

On Wed, Jul 5, 2017 at 2:57 PM, Philip Kim <phili...@gmail.com> wrote:

ahh i was just noting why you may be seeing some higher psi run with RTPs from other, as 30-40 psi is a bit high for a ~50mm tire.

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[Rod Holland]

I should have mentioned that the 30/35 PSI is with a 240lb rider. The Rat Trap Extralights are mounted on Sun Rhyno Lite rims. That choice of pressures is based on what had worked for me with a pair of 2.15" Schwalbe Big Bens. When I tried the same pressures on the RTPs, they just seemed to work.

rod

[Patrick Moore]

Perhaps the problem is your manner of phrasing the question. 

I read your question as: Do you consider XXX as high enough pressure for smooth road riding? 

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