Cycling Thread

[Bill Bumface]

Originally Posted by Fuzz

So I guess the answer depends on the type of trail you are riding.

Not really. Anything but a very hard packed pristine dirt road is considered "rough".

The Schwalbe test did it on grass, packed dirt and loose dirt I think.

If you aren't on a road, lower is better.

[combustiblefuel]

Originally Posted by Northendzone

got home yesterday and my back tire was flat like a pancake - so the tubeless conversion went ok on the front, not so well on the back.

Now need to go and pick up anotehr bottle of orange seal and fix this.......

Both systems essentially work the same way. The only real benefit of tubless is it knocks of a few 100 grams of weight.

[combustiblefuel]

Originally Posted by Bill Bumface

Not really. Anything but a very hard packed pristine dirt road is considered "rough".

The Schwalbe test did it on grass, packed dirt and loose dirt I think.

If you aren't on a road, lower is better.

No way . the less tire touching the ground (more pressure) the less rolling resistance you'll get. Less pressure is better for absorbing bumps but if you have any sort of rear suspension then this would negate the need to have lower psi in rear tires. Basically, the article is saying low pressure tires act as a suspension system that allows a hardtail to maintain controle sacrificing speed.

[Coys1882]

So what PSI are you guys talking about when you say you're running high and low?

[Bill Bumface]

Originally Posted by combustiblefuel

Both systems essentially work the same way. The only real benefit of tubless is it knocks of a few 100 grams of weight.

Not even close. The top cause of flats around here is pinch flats. Go somewhere with cactus or thorns and sealant saves the day. Yes I know you can use sealant in tubes, but no one does.

Tubeless setups are heavier in many cases because of the thicker sidewall on a lot of the UST tires and the weight of the sealant.

Originally Posted by combustiblefuel

No way . the less tire touching the ground (more pressure) the less rolling resistance you'll get. Less pressure is better for absorbing bumps but if you have any sort of rear suspension then this would negate the need to have lower psi in rear tires. Basically, the article is saying low pressure tires act as a suspension system that allows a hardtail to maintain controle sacrificing speed.

This is also completely wrong. I wish I could find that Schwalbe study as it points it out very clearly, but you are interpreting the other article wrong. When you hit a bump with high pressure, your whole wheel has to move up to go over the bump. Even with suspension, that is a bunch of energy being soaked up by your damper, as well as lifting the weight of your wheel and lower fork (if front) or wheel, derailleur and swing-arm (if rear).

With lower pressure, the tire just deforms, and there is barely any lifting force transferred.

[Bill Bumface]

Originally Posted by Coys1882

So what PSI are you guys talking about when you say you're running high and low?

High for me would be over 30psi

Low would be under 25.

"Normal" is between 25-30.

I'm just over 200lbs with gear on, so a lighter person can go lower. I think I'm typically about 25psi up front and 27psi in the back. Basically once I start to feel my wheel rimming out of little lips or jumps I put a bit more air in.

[cracher]

^ wow. do you take drops with 25psi? Has it every been a problem running that low?

For my FS bike, I don't have high end shock and fork (RP23 and float 140RLC). It does ok on moderate hits, but the stiction makes the suspension not do much for small chatter. My spinal cord tells me that lower (not bumface low though) pressure helps a ton.

[bossy22]

I run 25psi with a 2.25x29 tire. I'm 180lbs. My buddy runs 23 psi with a 2.1x26, but he's 147 lbs. I use sealant to allow me run a lower pressure and not have to deal with pinch flats. I'm not a weight weenie. I'd be better off to lose 10 lbs than 100gms from my wheels.

On my road bike I have HED ardennes wheels. They are a 23mm width, along with a 23/25 roubaix tire, that I run at 90psi. Super comfortable setup for 4+ hour days, and faster than my old mavic ksyrium wheels at 15mm width with a 21 tire at 120psi. Those just rattled my fillings out.

A wider tire with low pressure provides lower rolling resistance, less deflection, and more stability. This is why wheel makers like HED, ZIPP, Reynolds, Enve, etc are all going to wider wheels for road bikes.

[Fuzz]

Giving PSI without tire size doesn't provide much information. A big tire can run much lower PSI.

[Bill Bumface]

Originally Posted by cracher

^ wow. do you take drops with 25psi? Has it every been a problem running that low?

Nothing super crazy, because I'm a chicken, but it handles stuff around 2' no problem. I've rimmed out a couple times if I hit a rock with the rear, but pretty rare.

Originally Posted by Fuzz

Giving PSI without tire size doesn't provide much information. A big tire can run much lower PSI.

Tire sizes are also always made up. That was a 2.4" up front, that is probably closer to most 2.3 or 2.35 and a 2.1" in the back.

This year I've gone back to a slightly wider rear, as I didn't notice a big enough difference going narrower to make it worthwhile.

[Northendzone]

i am currently 260 lbs (and working hard on lowering it) - i have to think i could not run lower than 32psi unless i really enjoyed the feeling of rim out.....

[macker]

Different PSI sweet spot for each bike/tire type. Road bike 100 to 110 psi, Mountain bike 25 to 35 psi, Fatbike 5 to 10 psi. I know what some of the studies say and maybe it is a mind over matter thing but I have always found I can go much faster with as little as a 5 psi increase in tire pressure. Not as comfortable but faster!

[cracher]

Originally Posted by Bill Bumface

Nothing super crazy, because I'm a chicken, but it handles stuff around 2' no problem. I've rimmed out a couple times if I hit a rock with the rear, but pretty rare.

This scares me a little bit. While I'm relatively new to mtb, I dabbled in competitive bmx in the late 80s and early 90s... old habits die hard, so I still am pretty rough on bikes (no formal coaching back then, so I don't do anything smooth like the kids do today). Given how expensive hoops are, I think I would sacrifice some rolling resistance so make sure my fat ass doesn't drive a rock through my hoops. 32psi on a 2.25" tire on a 24mm rim vs my 190lbs including camelbak is about as low as I'd dare to go...

[Hevishot]

Can you MTB guys get some sort of foam insert or Bib Mousse like we have for dirt bikes or is it just tubes,HD tubes and tubliss setups?

[Bill Bumface]

Originally Posted by cracher

This scares me a little bit. While I'm relatively new to mtb, I dabbled in competitive bmx in the late 80s and early 90s... old habits die hard, so I still am pretty rough on bikes (no formal coaching back then, so I don't do anything smooth like the kids do today). Given how expensive hoops are, I think I would sacrifice some rolling resistance so make sure my fat ass doesn't drive a rock through my hoops. 32psi on a 2.25" tire on a 24mm rim vs my 190lbs including camelbak is about as low as I'd dare to go...

I'm not a smooth rider either apparently as I've broken almost everything on my bike beside the fork. While running with tubes still I'd already bent my wheels many times, to the point they were garbage last year. I bought some Havens, and even after mashing the pedal mid corner when my wheel hit a rock and deflected, I torqued the derailleur cage into the spokes, stopping my rear wheel dead, and the wheel only went a tiny bit out of true from the bent spoke. It was so slight the bike mechanic said he wouldn't even bother truing it yet, so this far the wheels have made a big difference in that department.

[combustiblefuel]

Originally Posted by Hevishot

Can you MTB guys get some sort of foam insert or Bib Mousse like we have for dirt bikes or is it just tubes,HD tubes and tubliss setups?

You can technically experiment with anything. I came from a motorsport back ground and have used ms tech for years.

You dont have to use cookie cutter parts mtb companys shove in your face. I know guys that run High density impact foams between the tire and tube. Works great when riding in wet weather and on rocky terrian. The only limitation is your imagination.

If it dose not exist make it.

[combustiblefuel]

Originally Posted by Bill Bumface

Not even close. The top cause of flats around here is pinch flats. Go somewhere with cactus or thorns and sealant saves the day. Yes I know you can use sealant in tubes, but no one does.

Tubeless setups are heavier in many cases because of the thicker sidewall on a lot of the UST tires and the weight of the sealant.



This is also completely wrong. I wish I could find that Schwalbe study as it points it out very clearly, but you are interpreting the other article wrong. When you hit a bump with high pressure, your whole wheel has to move up to go over the bump. Even with suspension, that is a bunch of energy being soaked up by your damper, as well as lifting the weight of your wheel and lower fork (if front) or wheel, derailleur and swing-arm (if rear).

With lower pressure, the tire just deforms, and there is barely any lifting force transferred.

1.Pinch flats are most likely to happen because you are running an inadequate psi.

2. If your suspension is properly setup yhen it should never have a negitive effect other wise what the #### is the point of buying a fully?? Just lower your psi and you have a air bage system. Lowering psi is good for traction that is all.

[Bill Bumface]

Originally Posted by combustiblefuel

1.Pinch flats are most likely to happen because you are running an inadequate psi.

2. If your suspension is properly setup yhen it should never have a negitive effect other wise what the #### is the point of buying a fully?? Just lower your psi and you have a air bage system. Lowering psi is good for traction that is all.

Please go re-read the article. You've misunderstood it.

If you run 40psi to avoid pinch flats from taking big hits you're sacrificing rolling resistance, comfort and traction.

[Reneeee]

I just started riding again heavy after a two year hiatus due to a knee injury and dual Surgeries. Anyways, for anybody that rides downtown and leaves their bike in public, what's the likelihood of stolen bikes nowadays? any advice would be warranted.

[habernac]

Originally Posted by Reneeee

I just started riding again heavy after a two year hiatus due to a knee injury and dual Surgeries. Anyways, for anybody that rides downtown and leaves their bike in public, what's the likelihood of stolen bikes nowadays? any advice would be warranted.

If your bike is a decent one, the likelihood of it disappearing is 100%. I'd never leave a bike unattended for more than a few minutes downtown.