lets talk tire sizes, pressures etc

[Sasper]

hi guyz, I havent been posting lately, and as dead as this place is, I still like to check in from time to time.
so, If any of the older members remember me besides my vote for my sister thread haha, I have always been saying that big tires ( 2.1 and bigger ) suck and are stupid etc.
when I first got my KHE 1.9 MAC 1.5 street tires ( its about 1.9" wide ) I fell in love, light , good grip and I like the shape cause I do alot of hang 5 etc, feels round , so shifting to manual 180s feels natural ( not like my ODSY paths did which always felt like (_) kind of. )

ok so, this summer I was talking to this local pro , he rides some 2.3 tires from demolition I think. I asked what pressure he has in there and why.
he said 4.3 bars ( mine are at 6 in the summer, and 5.something in the spring since my wrists are not used to hard shocks. )
and the reason he said, lower pressure helps him hop higher.
 can there be any truth to that?
as in , you press down hard before the bunnyhop and you load the tires with pressure and when you finally start going up .02 seconds later this flex and pressure will give you more pop ?

what do you guys think?

[Narcoleptic Insomniac]

Might be all a mental thing but I feel like higher pressure in the back needs slightly more force to pull up. On the other hand it's faster and more responsive.

[Prodigal Son]

I can't imagine running large low pressure tires. I like riding bowls.

As a mathematics exercise:

(6bars) 14.5 psi/1bar 87psi
(4.3) 14.5 psi/1bar 62.3psi

[G]

I like big tyres. You have to hit them harder to pinch puncture (for a given pressure) and they are more forgiving on hard landings (for a given pressure) but have very similar rolling resistance (for a given pressure).
Personally I run the same pressure (so I get these gains in trade off for a bit of weight) but if you want to run lower pressures then you are more likely to "get away with it" on wide tyres than on narrow ones... It's all personal preference, live and let live etc...


G.

[Sasper]

but what about answering my question, which is that , is there any truth behind bigger tire  - less psi - better bunnyhop?
i dont think so but..

[alaskun]

nosemanuals always came easier to me when I was outrunning a flat/leaking rear tire, so... maybe?

[G]

but what about answering my question, which is that , is there any truth behind bigger tire  - less psi - better bunnyhop?
i dont think so but..

I think that's too subjective. The energy needed to compress the tyre to the rim is simple provable physics, how you bunnyhop and what is "better" has too many variables and will probably vary with the rider. Simple enough thing to try for yourself and see. Build a basic bunnyhop bar, and try it at varying pressures...


G.

[LukeTom]

My perspective is from riding trails. So my experience comes pretty much 100% from that; although I find mannys easier with lower PSI

In regards to trails, a thin tire and/or low PSI on the back leads to some serious pinch punctures if you hang up, but if you tend to land flat the low PSI can be a saviour on your wrists. Also, when you ride sandy trails your psi is almost necessary to be low (and wide tires), or you end up sliding everywhere, and carving them up. But with most places I ride thick (above 2in) and with a PSI between 60-90 depending on the conditions/what I am trying to do (getting through the line or trying tricks etc.)

As with everything it really depends on what you are riding and what you are trying to achieve in your session, so bring a pump!

[JFax]

I can see how it physically could help out. If you compress the tyre upon lifting the front and pressing down on the rear tyre a preassure should build up that could technically function as a spring when you release the rear tyre when lifting it up.

It can probably be calculated but I think that there are too many variables to calculate it easily. No idea at all if the spring force would mount to an amount that would actually help you during bunny-hops...

I can sometimes feel though that low preassure tyres are easier to ride street with compared to mine, that normally run at 5-7 Bar. Not sure if its because of this or just the general feel of the bike.

[bsd510]

but what about answering my question, which is that , is there any truth behind bigger tire  - less psi - better bunnyhop?
i dont think so but..

I find it way harder to bunnyhop when my tires are below 60 psi. When my tires are low, I can sometimes feel my rim bottom out on the concrete when I hop, or it just sucks up all my pop. The only reason I tried running low psi is because of that one rider Andrew Jackson. He could always easily hop up/over the tallest stuff at 40psi  and said riding low pressure helps but when I rode his bike it always felt like shit to hop

I think anywhere from 60-90psi is a good amount. I used to run 90-100 cuz my friend always has 110psi and I liked the basketball feeling, but I found that for wallride grip, bunnyhops, rolling resistance and overall comfort 70-80psi is a good medium.

[bsd510]

Also crooks got somewhat easier when I switched from 2.4 to 2.2 in the back

[condrbkr]

I definitely believe the whole low pressure higher hop thing. I noticed that last Summer when I rode 40psi after reading some bike check on some pro. It did feel like you could compress and 'bounce' a hop. I stopped doing it cause it the spokes came loose a lot quicker and the feeling of bottoming out and hitting the rim bugged me plus riding fast on low psi feels awkward.

[O.G. David]

I run 3 bars front and 4 rear and did for years. I couldn't ride with more pressure, too violent.

[cmc4130]

but what about answering my question, which is that , is there any truth behind bigger tire  - less psi - better bunnyhop?
i dont think so but..

Probably yes.  It's like a mini trampoline.   Also, there could be a mental component to it:  In street riding, if you're going to have a softer landing, you might hop harder/higher, because of subconsciously having less aversion to a harsh landing. 

[goose]

and the reason he said, lower pressure helps him hop higher.

I think I have to agree. I can't do bunnyhops with super hard tires and the first time I noticed that I liked a lower PSI better was when I borrowed a GT Bump that had PowerLite Retro tires on it. That bike felt amazing and made me regret spending all my money on a S&M NG Dirtbike.