Over inflate, do you do it?

[StudEbiker]

I know that back in the day, my buddy that rode trick bikes would pump his tires up to crazy inflation. WAY beyond the recommended pressure. IIRC I think he used to run about 90 psi in a 20" tire. Anyway, I'm sure I would get rid of some rolling resistance if I did it, but I don't want to be crazy either. The max pressure listed on my tires is 65psi. Do you think running 80 would be okay or is it not worth it?

 

[TPA]

depends on the tire. High quality tires have a very pliable, flexible sidewall that does not sap energy as badly as stiffer tires.

I have Schwalbe Big Apples in 2.35" size. I do not notice much difference between 20psi and 60psi as far as power consumption goes, but the ride is much softer at 20.

You should be able to easily fold good tires. Cheap ones...not so much.

 

[GTR2EBIKE]

I inflate to the max psi on the sidewall of the tire or tube whichever is lower. HOWEVER today I was inflating my front mountain tire from my mountain bike(no motor) it said 20psi after a while of pumping i said to myself this cant be 20psi anymore, stopped pumping reached down to take the valve of to re-seat it and KABOOM(much louder in person). Not a fun experience my ears hurt for about an hour

 

[StudEbiker]

I inflate to the max psi on the sidewall of the tire or tube whichever is lower. HOWEVER today I was inflating my front mountain tire from my mountain bike(no motor) it said 20psi after a while of pumping i said to myself this cant be 20psi anymore, stopped pumping reached down to take the valve of to re-seat it and KABOOM(much louder in person). Not a fun experience my ears hurt for about an hour

Yeah, I've noticed that sometimes on air pumps if you don't have the head on all the way it will feed pressure into the tire, but not show a pressure reading.

 

[AussieJester]

I run 110psi in my wheelchair tires (rated for this pressure) and can tellz when they deflate over time to around 80psi you REALLY notice the difference its ALOT harder to push about....That said i wouldn't recommend over inflating tires on an e-bike your doing pretty high speeds a blow out on the front tires is the last thing you want ...been there done thats...

KiM

 

[liveforphysics]

Buy an extra tire and tube of the type you plan to use.

Get it to a worst-case-scenerio temperature with a heater in a cardboard box (or whatever you have handy).


Clip an air line to the valve, stand back, and slowly dial the regulator up on the air compressor tank until you see the tire start to deform badly or explode. Note that pressure, give yourself a safety margin (maybe -30% of burst pressure?).

At least that's how I would do it. Nobody can verbally give you a magic number to shoot for on a forum. Some tires will take 100psi forever with out an issue, others might explode at 40psi. Test, and you know.

 

[StudEbiker]

I think I'll just run at the recommended pressure. A front blow out would suck for sure.

 

[auraslip]

After a certain point the tire starts to bulge out. The bulging increases the tire contact with the ground. This increases rolling resistance, and is the opposite of what you want.

BTW why would you risk safety and comfort for a few extra watts saved? I try to run my tires as LOW as possible.

 

[Mark_A_W]

The rim is the issue.

You may have a catastrophic failure of the rim if you go too far.


I run my hookworms at 65psi. Soft tyres make the bike all squiggly. Suspension takes care of the bumps.

 

[jbond]

Modern tyres, modern rims, treat the max pressure as the minimum and you'll be fine. And a 65psi max tyre will happily take 75-80. But there's a trade off. Wide tyres need less pressure for the same rolling resistance and the rolling resistance benefits of over-pressure are small. If you run say 80 in a 65psi tyre, you may find the ride comfort unacceptable with only a small gain in rolling resistance. The other factor is that heavy duty tyres like the Marathon Plus in small sizes like 700c-32c are very stiff so that plus 90-100 psi will get very uncomfortable. However narrower tyres tend to have higher max pressures, less wind resistance and less weight in the rim so for all out speed go on the small side of the compromise and push the pressure as high as you can get away with. That's why road racers run tiny tyres at 120psi upwards. But we've got an electric motor, right? So our side of the compromise tends to 45c widths and upwards at lower pressures.

For years my hybrids all had 700-32c tyres at >90 psi because I thought ultra hard, narrow tyres was the way to go. Now I've got an e-bike with 1.75"-26" at 70 psi and I wonder why I put up with that uncomfortable ride for all those years.

 

[liveforphysics]

After a certain point the tire starts to bulge out. The bulging increases the tire contact with the ground. This increases rolling resistance, and is the opposite of what you want.

BTW why would you risk safety and comfort for a few extra watts saved? I try to run my tires as LOW as possible.

This is 100% wrong. In all respects.

 

[Mark_A_W]

I've had a single wall rim (the crap one you get with a hub motor) open out as I pumped up the tyre.

Rims are rated for maximum size tyres (1.75, or 2.5, etc) and my understanding is it's related to the angle of the pressure from the tyre.

 

[AussieJester]

After a certain point the tire starts to bulge out. The bulging increases the tire contact with the ground. This increases rolling resistance, and is the opposite of what you want.

BTW why would you risk safety and comfort for a few extra watts saved? I try to run my tires as LOW as possible.

This is 100% wrong. In all respects.

:-| Not only wrong its exact opposite of what actually happens...you thinking what i am thinking Luke? i.e its a very "morphlike" statement LOL


KiM

 

[liveforphysics]

After a certain point the tire starts to bulge out. The bulging increases the tire contact with the ground. This increases rolling resistance, and is the opposite of what you want.

BTW why would you risk safety and comfort for a few extra watts saved? I try to run my tires as LOW as possible.

This is 100% wrong. In all respects.

:-| Not only wrong its exact opposite of what actually happens...you thinking what i am thinking Luke? i.e its a very "morphlike" statement LOL


KiM

I did get a strong morph-like vibe...

 

[fortytwo]

My dad always said you should stop pumping 3 pumps before it will burst!!

 

[AussieJester]

My dad always said you should stop pumping 3 pumps before it will burst!!

Sure he was talking about tires and not condoms ...sorry couldnt resist

KiM

 

[icecube57]

Be careful with tire pressures on single wall rims. Ive been battling this for a while. I have a cheap single wall rim on my x5. I take it to get trued. Its perfect when they get done but as soon as I put a tire and tube on and start pumping you hear the spokes reposition at pressures above 40psi. This unfortunately causes a slight wobble. My lbs wont true with a tire on. I dont have this problem on double wall rims that have the spoke nipples recessed within the rim.

 

[FMB42]

Optimum tire inflation really depends a number of factors which generally include: vehicle/rider weight, road/terrain conditions, riding styles, vehicle speeds, and ambient temperatures, etc. Determining the optimum tire pressure(s) for you, your vehicle, and your riding style/road/terrain conditions can be a matter trail and error.

As for the OP, most modern tires state a maximum tire pressure that is about 40-50% less than the actual blow-out pressure. I myself, tend to stay within the maximum pressure as stated on the tire sidewall. However, I've known several very high speed motorcycle owners (Yamaha 650 turbo w/ modified waste gate, Yam RZ 500 2 stroke 4 cyl. road race replica, etc) that successfully ran their tires at 90+ psi (probably 20%, or so, over max). But then again, these guys routinely reached speeds well in excess of 150 mph...

BTW, using a high quality rim tape is always a good idea (especially when running "double walled" rims).

Here's a SB link that some of you might find interesting:

http://www.sheldonbrown.com/tires.html

 

[auraslip]

I read it online in some recumbent journal. I can't freakin' find it now

Basically they rolled recumbents down hills at different tire pressures. As the psi increased, speed increased. At least until a certain point, at which speed decreased. I don't know if they were just conjecturing; After a certain pressure the tire starts to morph and stretch. Instead of decreasing, the contact patch increases as the tire deforms. Instead of becoming more round it becomes more flat.

 

[julesa]

Lower psi gives you a larger contact patch, more rolling resistance, lower energy efficiency. But you're less likely to lose traction too, on acceleration, deceleration, or while cornering. I'm generally more concerned about stopping power and gripping the road on turns than I am about that last little fraction of energy efficiency.

 

[friedwires]

im running a set of schwalbe fat franks on narrow mtb disk wheels.they're rated at 60 psi max. if i let them get any lower than 60 they feel squirrely on a hard turn,like they're gonna roll off the rim. if i pump em up to 70psi the rear rubs the frame. so my happy medium is 65psi.they get great traction and are stable in the turns.

 

[Kingfish]

Conditions should dictate the pressure.

The only time I exceed the rated pressure is if I know the tire is leaking, and then I will go 10-15 psi beyond; eventually the tube or value needs replacing. Otherwise I rarely exceed the pressure, preferring a softer ride.

~KF

 

[amberwolf]

I want to figure out how to make a bicycle hub/wheel that I can change pressure on the fly as I ride, kinda like the ones on those old half-tracks and similar vehicles the US Army used to use.

Probably will never happen, but it would be kinda nice.

 

[Hillhater]

I want to figure out how to make a bicycle hub/wheel that I can change pressure on the fly as I ride, kinda like the ones on those old half-tracks and similar vehicles the US Army used to use.

Probably will never happen, but it would be kinda nice.

some of the Dakar race cars & trucks use systems for changing tyre pressure "on the run" .

 

[northernmike]

If rolling resistance is your enemy, get a set of Schwalbe Kojaks and super-light tubes.

INSANELY AWESOME. Like, coast for MILES awesome.

And, dead silent. Worth the $.

If pavement is all you're dealing with, that is.

High-pressure tires also make you want suspension, which of course adds weight.

No free lunch.