ADVrider

Go Back   ADVrider > Riding > The perfect line and other riding myths
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-21-2012, 03:12 PM   #16
randyo
Beastly Adventurer
 
randyo's Avatar
 
Joined: Nov 2007
Location: Northern NewEngland
Oddometer: 1,556
Quote:
Originally Posted by lucifermutt View Post
suddenly all the topics in faceplant make sense when people randomly slide out on nothing during slow turns. Running your tires at the max psi on the sidewall is eating up half the traction you'd have otherwise...
bs
__________________
RandyO
IBA # 9560
07 VeeStrom
99 SV650
82 XV920R
A man with a gun is a citizen
A man without a gun is a subject
randyo is offline   Reply With Quote
Old 03-21-2012, 03:13 PM   #17
LuciferMutt
Rides slow bike slow
 
LuciferMutt's Avatar
 
Joined: Aug 2008
Location: New(er) Mexico
Oddometer: 11,097
hyperbole

note: that isn't pronounced with a "bowl" on the end.
__________________
You couldn't hear a dump truck driving through a nitro glycerin plant!

Badasses might screw with another badass. Nobody screws with a nut job. -- Plaka
LuciferMutt is offline   Reply With Quote
Old 03-21-2012, 03:47 PM   #18
rivercreep
Banned
 
Joined: Feb 2007
Location: S.E. Pennsylvania (Reading)
Oddometer: 3,243
I found this site helpful for...understanding tires.

http://www.motorcycleanchor.com/moto.../mc_tires.html

Always keep in mind that what's written on your bikes swingarm for tire pressure is a suggested parameter to be used with stock size tires.
One of the many reasons WHY is because the suspension is designed to work in conjunction with the flexability of the tires sidewall. Upping pressure is almost like increasing spring rate (to an extent) and vice versa. An example would be when NASCAR teams adjust their tires pressure a measely 1/2 psi or more and it helps fine-tune their suspensions reactions.
What works best for 1 bike/rider combo might not work for another guy who's 1/2 the weight on virtually identical bikes.

One observation I'm taking away from some of the comments here is a better understanding of why/how some people find themselves in positions where their tires delaminate or chunk. (and they always blame the tire mfg. when they themselves contributed to it)

I'll never claim to be the sharpest tool in the shed but, sometimes after I log off this site, I feel like a freaking genius.
rivercreep is offline   Reply With Quote
Old 03-21-2012, 04:13 PM   #19
antonac OP
Commuter
 
antonac's Avatar
 
Joined: Apr 2010
Location: Philadelphia
Oddometer: 324
Quote:
Originally Posted by HairBear View Post
Odd statement when the sticker on my KLR says 21psi.
No need to run that low, I weigh 145 pounds and carry no cargo

Enlightening stuff, I guess it's not as cut and dry as I thought.
__________________
'06 DL650
"Go soothingly on the grease mud, as there lurks the skid demon"
antonac is offline   Reply With Quote
Old 03-21-2012, 04:23 PM   #20
Kommando
Grumpy Young Man
 
Kommando's Avatar
 
Joined: Nov 2006
Location: Spacecoaster FL
Oddometer: 7,062
I use onroad pressures somewhere between what's recommended and the max on the sidewall. Any more almost always feels too hard and squirrely. Any softer typically generates a LOT of heat on the highway. I shoot for the 10% increase from cold to warmed-up.

I know people who run the sidewall pressures in their cage. Then they wonder why their tires wear unevenly and the ride is crap. I typically run the cage tires midway between recommend and sidewall, but my GF and I corner hard, so MPG is better and wear is pretty even.
Kommando is offline   Reply With Quote
Old 03-21-2012, 05:01 PM   #21
Bucho
Beastly Adventurer
 
Joined: Dec 2006
Location: Maryland
Oddometer: 1,805
Quote:
Originally Posted by randyo View Post
airing down for off road is a placebo
Is this supposed to be sarcastic? Are you really saying that airing down your tires for offroad doesn't help?

Perhaps I'm misunderstanding something, but running low air pressure for offroad works very well. It lets the tire spread out for a larger contact patch. Assuming you have a soft high profile tire, it also lets the tire have plenty of flex to sort of wrap around rocks ect... to give a little more traction. Obviously how low exactly depends on a lot of factors. I run anywhere from 14 to 8 pounds offroad.
Bucho is offline   Reply With Quote
Old 03-21-2012, 05:40 PM   #22
ibafran
villagidiot
 
Joined: Apr 2007
Location: chicagoland
Oddometer: 1,286
The 10% guideline works for me. That said, here's MHO:
On my 05 Sprint: factory specs; 36F/42R. Front Dunlop max is 42. Rear Mich. RP3 max is 42.

In the dry and on clean pavement, the psi can be pretty high and not affect traction nor ride quality. Recently at a track and turning touring speeds (sub-90mph) my tires grew to 48F and off scale 50+R psi. The tires did not slide around. But they did not provide much feedback either. It is amazing how high the psi can be and still work well under track-like conditions.

The urban street is an entirely different matter than the highway or track. The street has a lot of irregularities that require tire flex for good traction. And the street doesn't heat the tires like a track. So the rubber may not get real pliable and the tire may not get harder psi from heat build-up. PSI on the street is a little more stable.

A really max inflated tire will have lower rolling resistance. In order to get the extended mileage such lower rolling resistance offers, the bike has to be ridden in such a manner as to keep the rubber from being sheared/abraded off the tire. With a slightly smaller contact patch that must pass power, hard braking and hard acceleration will shear more rubber off the tire faster in that limited contact patch. (Too low psi makes the contact patch squirm and quickly abrades rubber in that manner.) In order to make tires last, and fine balance point has to be achieved between the highest psi possible and getting the useful traction desired. The factory specs usually are pretty close to a good place to start. Vary from those specs as you desire knowing that you are trying to get a balnce point somewhere else.

High psi usually does not work well in the wet on the street. The smaller and harder contact patch allows the front tire to lock much easier at slight irregularities. And once that the wheel is locked in the rain, it continues to slide much easier than in the dry. This is why it is so much harder to save a front wheel slide in the wet than in the dry. Same for the rear. Once broke loose in the wet, it is harder to get the rear hooked up if the tire is harder with high psi.

FYI, I average 12k miles on a set of tires because I ride softly as much as possible. Knowing when where and why shredding rubber is desirable is fun. Knowing how not to shred rubber is economical. YMMV
__________________
"beware the grease mud. for therein lies the skid demon."-memory from an old Honda safety pamphlet
ibafran is offline   Reply With Quote
Old 03-21-2012, 06:32 PM   #23
randyo
Beastly Adventurer
 
randyo's Avatar
 
Joined: Nov 2007
Location: Northern NewEngland
Oddometer: 1,556
Quote:
Originally Posted by Bucho View Post
Is this supposed to be sarcastic?.
I'm very serious, no need to air down (radial tires)it does not make for better traction it makes for dented wheels if anything
__________________
RandyO
IBA # 9560
07 VeeStrom
99 SV650
82 XV920R
A man with a gun is a citizen
A man without a gun is a subject
randyo is offline   Reply With Quote
Old 03-21-2012, 06:46 PM   #24
perterra
-. --- .--. .
 
perterra's Avatar
 
Joined: Sep 2010
Location: Tejas
Oddometer: 7,400
Quote:
Originally Posted by randyo View Post
I'm very serious, no need to air down (radial tires)it does not make for better traction it makes for dented wheels if anything

I dont have radials, does it do me any good?
__________________
My Father was my maker. Poverty was my maker. Distrust was my maker. I have met them all my life.


IBA 22425
perterra is offline   Reply With Quote
Old 03-21-2012, 07:00 PM   #25
DAKEZ
Beastly Adventurer
 
DAKEZ's Avatar
 
Joined: Mar 2007
Location: OR
Oddometer: 19,690
Quote:
Originally Posted by randyo View Post
I'm very serious, no need to air down (radial tires)it does not make for better traction it makes for dented wheels if anything

WOW.

Quote:
Originally Posted by randyo View Post
high pressure is NOT a safety issue, airing down for off road is a placebo

__________________
“Watch out for everything bigger than you, they have the "right of weight"
Bib

DAKEZ screwed with this post 03-22-2012 at 03:01 PM
DAKEZ is offline   Reply With Quote
Old 03-22-2012, 10:07 AM   #26
randyo
Beastly Adventurer
 
randyo's Avatar
 
Joined: Nov 2007
Location: Northern NewEngland
Oddometer: 1,556
AGAIN, there IS no MAX pressure imprinted on the sidewall of a tire, what you see printed is the MAXIMUM LOAD RATING (weight that the tire can support) the pressure that is imprinted is the pressure you need to support the MAXIMUM LOAD

if you run less than the pressure indicated, the weight rating of the tire is less, what works for your bike and payload can be less, I wouldn't trust 15psi to even support the weight of my bike
__________________
RandyO
IBA # 9560
07 VeeStrom
99 SV650
82 XV920R
A man with a gun is a citizen
A man without a gun is a subject
randyo is offline   Reply With Quote
Old 03-22-2012, 10:23 AM   #27
kerhonky
Adventure Poser
 
Joined: Jan 2006
Location: Selkirk, NY
Oddometer: 1,134
I think it depends on what kind of oil you're running in the bike.
__________________
You learn something new every day if you're not careful.

"When you have to shoot, shoot, don't talk."
Tuco Benedicto Pacifico Juan Maria Ramiriez, otherwise known as "The Rat."
kerhonky is offline   Reply With Quote
Old 03-22-2012, 10:42 AM   #28
LittleRedToyota
Yinzer
 
LittleRedToyota's Avatar
 
Joined: Apr 2011
Location: Pittsburgh
Oddometer: 2,232
Quote:
Originally Posted by randyo View Post
airing down for off road is a placebo
i've read some comments on this forum that are very much divorced from reality, but that one puts them all to shame.

tire deflection is key to off road traction. you don't get much, if any, useful-from-the-standpoint-of-dirt-riding deflection at 15psi and higher. you also get a much smaller contact patch which, on surfaces with little traction, makes a huge difference.

once in awhile, i will forget to air down before hitting trails after dual sporting to them. it takes about a minute until i realize it. "why the fuck is my bike handling like an overinflated basketball on a bumpy ice rink?" "oh yeah, i forgot to air down."
LittleRedToyota is offline   Reply With Quote
Old 03-22-2012, 10:54 AM   #29
Idle
Studly Adventurer
 
Joined: Jun 2011
Location: Northern California
Oddometer: 630
Can't multi quote with my phone...
Dude..
Bro..

Fact is that significantly lower pressures off road will enable you to go anywhere from 15% to 40% faster on the same dirt road or trail. Give back some of that time you saved and cherish your rims through the square rock gardens.
Personally, i'm about 25% faster with less air.

It is fact.


I run 15psi on my 17" street tires off road. 22 or so on the road. My motard and I weigh 510 pounds.
Idle is offline   Reply With Quote
Old 03-22-2012, 11:06 AM   #30
dillon
Low Speed, High Drag
 
dillon's Avatar
 
Joined: Mar 2006
Location: Spokavegas, WA.
Oddometer: 1,647
Running a tire at max PSI under less than max load will result in faster tire wear through the center and less rubber on the road. The other side of this is since there is less rubber on the road and the tire will actually be more round there is less rolling resistance and thus you can see an increase in fuel millage. That max pressure is what the tire is designed to run at at max load(example: my 3/4ton runs around town with 40psi in the rears and 45psi in the front, when im towing i crank all 4 up to 80psi). Running a tire too low will result in heat build up and delamination of the tire plies, this is how blow outs happen. Also running too low of pressure will cause the tire to be mushy and only wear on the outer edges of the tread. When I was setting up off road trucks we used to draw chalk lines acrost the tread and run it back and forth in a straight line to find the ideal tire pressure, if the chalk line was just wore off in the center and still there on the shoulder, too much pressure, if it was worn off on the shoulders and still there in the center, too little pressure. For what its worth I usually run motorcycle tires close to max psi, Im not worried about wearing out the centers as they do this anyway, but it stiffens the tire and makes handling better. Also lowering pressure off road will increase the contact patch of the tire and result in better traction, it will also allow the tire to deflect more, good for loose surfaces, bad for hard surfaces.
__________________
I do stupid stuff, brace yourself...
dillon is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 01:47 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014