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Old 05-05-08, 07:59 AM   #1
trueno92
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what psi do you run on ur folders? 20" wheels and smaller

Hey guys, just with making the transition to a smaller folding bike, I finally got my Schwalbe Marathon's mounted (thanks for all the help, guys + sporting life!) and they got about 75psi in there now. I really enjoy the ride and low rolling resistance, but its on a 16" wheel and was wondering what everyone else runs? no creaks or squeeks in the frame and things seem to be good.. anyone run 100 or more?
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Old 05-05-08, 08:50 AM   #2
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My Schwalbe Marathon 20X1.5's say 45-100 PSI on 'em - that's quite a range! - so I've been putting in 100, maybe even a bit more.
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Old 05-05-08, 09:25 AM   #3
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I have Marathon Plus's on all my folders

Swift=75 PSI
Moulton APB=100+

good choice on the Schwalbe's, bulletproof, nice riding tire
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Old 05-05-08, 09:38 AM   #4
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Lately I have been running my Marathon Racers on the NWT at 60 and 68 psi for the front and rear respectively. The Big Apples on the Mini are run at 50 and 80 psi for the front and rear respectively. Note that I pump up the rear tire on the Mini high since it has a rear suspension.
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Old 05-05-08, 09:54 AM   #5
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yeah the tires are really great, and im hoping i don't have to change them anytime soon (16" x 1.5 = $30 each! yikes)

The range is,indeed, 45-100psi - which is great! probably the highest max spec tire i have ever owned! lol

I was reading about 100psi but then with that being the MAX, i wasn't sure about the tire heating up in hot weather and having a blow out on a long ride on a sunny day..
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Old 05-05-08, 11:44 AM   #6
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Hey guys, just with making the transition to a smaller folding bike, I finally got my Schwalbe Marathon's mounted (thanks for all the help, guys + sporting life!) and they got about 75psi in there now. I really enjoy the ride and low rolling resistance, but its on a 16" wheel and was wondering what everyone else runs? no creaks or squeeks in the frame and things seem to be good.. anyone run 100 or more?
I run 16" marathons between 65-70psi and they're plenty fast for me at that pressure. Any more and I'd feel nervous. I spend part of my time on sidewalks, so I wouldn't go above that unless you're on only good tarmac or a light rider.
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Old 05-05-08, 12:25 PM   #7
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On my Dahon Mu XL with 20" Marathon racers, I am running about 65psi on both tires.
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Old 05-05-08, 12:48 PM   #8
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DT, kendakwest 44 PSI
Birdy Marathon Plus 95-105 PSI
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Old 05-05-08, 02:28 PM   #9
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My Brompton with Velocity Aeroheat (ISO 349 aka 16") rims and Schwalbe Stelvio folding tyres rolls happily at 110psi. Yes it's fast. Bit bumpy but fast.
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Old 05-05-08, 02:31 PM   #10
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65 psi on the Merc 16 inchers and 100 psi on the 20 inch marathons of the TSR30. Both of these are the stated max of the particular tyres used. The fully suspended Moulton is smooth even with rock hard rubber under it.
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Old 05-05-08, 04:42 PM   #11
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70 psi front & rear seems best for me, but I do find the Marathon's seem to be a slow tire at any pressure.

Would Big Apples be any better (faster), or would they just be more of the same?
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Old 05-05-08, 05:19 PM   #12
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Ever since I did roll-down tests and found tyre pressure to be towards the insignificant scale of things, I stopped worrying about it. My Downtube Mini's Big Apples 40psi, the Swift's Conti Grand Prix' at 90psi but long periods (months) sometimes go by without topping up. The R20 I have no idea, hard enough not to be bouncy or squirmy in corners, probably above 30psi.
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Old 05-05-08, 07:40 PM   #13
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I always have run my bike tires and my motor vehicle tires at max. pressure, or a little above, under the impression that it reduces rolling resistance and likelihood of blowouts and increases tire life, only at the expense of a more comfy ride. My motor vehicle tires tend to last a long time. Haven't rode a bike enough in recent years to adjudicate tire longevity.

What sort of tests did you run, Jur?
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Old 05-05-08, 08:36 PM   #14
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451 Stelvios at no less than 110psi
406 Comets at 90-100psi
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Old 05-05-08, 09:03 PM   #15
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What sort of tests did you run, Jur?
I did some roll-down test from an incline, with different tyre pressures. I also had 3 different bikes and different tyres. The results were that tyre pressure made very little difference (a few % at most) to the roll-down time (which was about 40s IIRC), the differences were just about the same as the margin for error. The biggest difference came from different bikes or from an extreme, impractical aero tuck. So because I couldn't really see a proper difference, I concluded that tyre pressure was such a small contributer to overall pedalling effort that it's not worth worrying about it, and that even if the tyres feel different or faster, you can't trust those feelings. This general conclusion was confirmed by another forumer who had done similar, more systematic tests.

So all i worry about these days is that the tyres are not so soft as to cause pinch flats, and not so hard as to negate the advantage gained from pneumatic tyres over solid ones. Hence the Big Apples at about 40psi, so that the balloon effect does its job.
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Old 05-05-08, 09:37 PM   #16
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I did some roll-down test from an incline, with different tyre pressures. I also had 3 different bikes and different tyres. The results were that tyre pressure made very little difference (a few % at most) to the roll-down time (which was about 40s IIRC), the differences were just about the same as the margin for error. The biggest difference came from different bikes or from an extreme, impractical aero tuck. So because I couldn't really see a proper difference, I concluded that tyre pressure was such a small contributer to overall pedalling effort that it's not worth worrying about it, and that even if the tyres feel different or faster, you can't trust those feelings. This general conclusion was confirmed by another forumer who had done similar, more systematic tests.

So all i worry about these days is that the tyres are not so soft as to cause pinch flats, and not so hard as to negate the advantage gained from pneumatic tyres over solid ones. Hence the Big Apples at about 40psi, so that the balloon effect does its job.
Laboratory conditions exist because they eliminate variability, thus providing much more accurate results than real world tests. Real world tests exist because laboratory conditions aren't variable enough, and thus are not generalizable to the real world. Fortunately, a happy medium exists; testing similar routes with a power meter.

Don't take this the wrong way, but your roll down tests are not going to be even close to providing you with information on differences in rolling resistance. Your cheapest bike rolled best downhill simply because it was heaviest. Now, if you repeat the experience in a vacuum and get the same results, I'd be more inclined to believe them!

Nonetheless, I would be more content that you feel comfy on your bike than a tad faster!
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Old 05-05-08, 10:05 PM   #17
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Your cheapest bike rolled best downhill simply because it was heaviest.
There was no mention of which bike rolled the best, only that tire pressure wasn't a factor.

What was stated was that tire pressure variation on the 3 different bikes didn't change the results.

"The biggest difference came from different bikes or from an extreme, impractical aero tuck." which doesn't sound like it is likely to be the cheapest bike.

A good laboratory experiment tries to explain as much real world variation as it can. I spent more than a decade as a research scientist and know a lot about the failings of simplistic lab tests and their lack of validity in many real world situations.

There is nothing inherently different in the way physical laws work inside a Certified Research Facility versus the the way they work in the rest of the world.

On rolldown tests I have done there are major differences in time and distance traveled with different riders, presumably because of weight and its,effect on inertia, but I think Galileo showed that mass alone doesn't influence acceleration.

With the same riders, rolldown tests show similar rankings for each rider with different tires and different bikes.

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Old 05-06-08, 12:57 AM   #18
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120psi (maximum) for both stelvios and Conti GPs.
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Old 05-06-08, 01:03 AM   #19
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Don't take this the wrong way, but your roll down tests are not going to be even close to providing you with information on differences in rolling resistance.
You are quite correct, 'other factors' dominated the result, completely obscuring the tyre pressure effects. The test was not good enough to detect those effects. That's why I no longer worry about something which is small in the scheme of things. For TdF racers who look for small advantages pressure is important, but not for me. It is not important for me to arrive at work 30s sooner.
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Old 05-06-08, 01:12 AM   #20
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This table shows some proper tests done on different tyres and sometimes the same tyre run at different pressures. Taking the Conti Top Touring 406 running at either 70 or 90 psi, the time loss in the lower pressure test over a ten mile ride would be 15 seconds - not much, I'll grant you, but it does exist. At 20 miles an hour running both tyres on the softer setting will necessitate that you put in an extra 20 watts of power at the pedals assuming (which you can't) perfect efficiency in the transmission. Twenty watts would easily mean me pedaling twenty percent harder for the same speed - err - no thanks mate.

http://www.hadland.me.uk/rolrec10a.pdf

Information on the testing procedure:

http://www.hadland.me.uk/lafford.htm
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Old 05-06-08, 01:22 AM   #21
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This table shows some proper tests done on different tyres and sometimes the same tyre run at different pressures. Taking the Conti Top Touring 406 running at either 70 or 90 psi, the time loss in the lower pressure test over a ten mile ride would be 15 seconds - not much, I'll grant you, but it does exist.
Wow. 15s in 16km, 30s in 28km - I guessed that I would be at work 30s sooner, I didn't think that guess would be so accurate!
Thanks for those links, I can almost quote them verbatim by now, having pored over those tables for years now!
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Old 05-06-08, 02:53 AM   #22
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That table confirms what I thought about the Marathon - it's a comparatively slow tire.

Big Apples were not rated, so I will ask again - how do the Big Apples compare with the Marathons?
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Old 05-06-08, 03:05 AM   #23
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Big apples are low pressure 'baloon' tire so its rolling resistance will be huge. But you can pump it up to 100psi (if I remember correctly) and I suppose big apple @ 100psi will be comparable (or better) to most 1.5 tires @ 30-40psi.
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Old 05-06-08, 03:33 AM   #24
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Wow. 15s in 16km, 30s in 28km - I guessed that I would be at work 30s sooner, I didn't think that guess would be so accurate!
Thanks for those links, I can almost quote them verbatim by now, having pored over those tables for years now!
LOL - you're right about the time, but I just think of that six watts difference per tyre on the contis for 20 psi. Also, the lower figure was still pretty high at 70 psi. I expect I could soak up half of my feeble available power by running them at 40psi.

Maybe your 'cavalier' attitude to this problem is down to your super human physique. Don't forget, we've seen how you win races on your twenty Jur, and power over all those southern hemisphere mountain rages on a touring folder, not to mention busting the cogs in your SA8 hub through sheer beastly pedaling force. If you have a ferrari engine under the hood a soft tyre may not make any difference to you - me on the other hand, I'm running a coked up prewar side valve that might put out an average 80 watts. Expending a quarter of that in running two softish tyres is not on my agenda, especially since my stirrup pump is so easy to use once a week.




This post has been edited for errors on the wattage and pressure figures in the original post

Last edited by EvilV; 05-06-08 at 07:12 AM.
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Old 05-06-08, 06:13 AM   #25
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Big fat Maxxis Hookworms - max 120 psi. I run them at about 110. Bumps are a bit painful like that though.
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