I got another reminder of just how much affect tire pressure has on the handling of our bikes yesterday. I'm becoming a firm believer that most handling problems on modern sportbikes are caused by having worn tires and/or running too low a tire pressure. I've been having some handling problems recently withe the CBR. Low speed turn in felt trucklike (heavy) and unstable, this was robbing my confidence. On high speed corners the bike just felt nervous...darty....no scarey! I attributed this to the lightweight of the machine and steep front end geometry. I was wrong. I was pulling routine maintenance the other day and found both front and rear tires low by 6 psi. 30 psi front and 36 rear while the book calls for 36 and 42 respectively. Doesn't sound like much but man what a difference it made in the handling. Low speed steering now feels light but accurate, no tendency to overshoot the mark like before while the high speed is now quick and dead nutz stable. My confidence is back, this thing is amazing in the turns. Need to check the 14 next.

Kruz

Car too. Plane much?

you're right about the tire pressure. I took mine in for it's first service in July, the shop set my tires to 30 psi each...I rode home thinking man this thing is not riding right...I about flipped when I checked tire pressure. My bike won't be back in that shop...ever! I've started doing my own maintenance since then. I keep mine at 36/40, and that seems to ride good for me.

Every time I take my bike into the silly shop, it comes back with 36psi in both front and back, and I pump them up to 42psi. They should both be 42psi (at least going by the book), right? -bg

Good habit to get into. I check mine before each ride, just a couple of psi can make a huge difference in how the bike feels and stops. I'm kind anal about chain maintenance too, I clean and lube the chain every 600 to 700 miles too.

On this topic, a lot of guys I speak to miss the whole concept of "cold pressure".

Cold pressure is when the tyres are completely cold (eg. first thing in the morning before riding or after the bike has cooled down for an hour or so). As soon as you ride, even if it's just down the road to a nearby air pump, your tyres will heat up at least a bit and any increase in temp will also increase the tyre pressure. So when you arrive at the pump and punch in a desired pressure of say 42 PSI, when your tyres cool down overnight they will probably be at less than 42 PSI WHEN COLD!

I don't have an air comp. at home, so what I do is check my cold pressures first thing before riding (not as often as I should...) and then check them again when I get to a pump. Normally the reading will have increased a few PSI front & rear. Then I add the diff to what I want the cold pressure to be. For example, I check the tyres in the morning and my rear is at 36 PSI. I then ride to a air pump and check again, and by now it's at 38 PSI. I want my cold pressure to be ~42 PSI, so I pump it up to 44 PSI, making allowance for the 2 PSI that has been added now that the tyre isn't cold anymore.

Regardless of the above, I like to run my tyres at much less than the Owner's Manual's recommended 42 PSI. I heat the tyres up the way I ride, and I like to have some feel...otherwise it's like I'm on ice skates.

On the track it's normal to go down to 28 PSI (what does that do to this idea of "bad handling" when at lower pressure?). So if you use the street like it's a racetrack...don't get to hung up on 42/42 or whatever max pressures the manual may recommend. Just like suspension settings, staying "stock standard" isn't always best.

My 2cents.

bg wrote:

Every time I take my bike into the silly shop, it comes back with 36psi in both front and back, and I pump them up to 42psi. They should both be 42psi (at least going by the book), right? -bg

Same here. You'd think they could at least get that right. You'd almost think some of these places employ people who never owned a treasured motorcycle by the way they treat our stuff.

I recently picked a cheap plastic compressor at Harbor Freight. It looks like a little yellow submarine. It only cost me $6 and it works great for bringing my tires up to pressure. I thought it might have a hard time with 42 psi but it seems to handle that fine (directions claim it will go up to 250 psi). The compressor plugs into a cigarette lighter. I don't think the gauge on the compressor is accurate but otherwise it works great. At 75 cents a fill at the station, this little baby should pay for itself in no time. If it breaks in a year, it will be worth the convenience of having it at home.

On the track it's normal to go down to 28 PSI (what does that do to this idea of "bad handling" when at lower pressure?).

Aussie,are we talking racing tires like BT-02s here? If so, I can agree that racers run lower tire pressures to get better cornering grip but street tires are constructed differently with regards to tire compound and construction.

A lot may have to do with type of tire and amount of wear on the tire as well. Some tires have a stiffer carcass than others depending upon ply type, ply number and ply orientation and low pressure will affect them differently. All I know is that the Bridgestone BT-014s that were OEM on my 14 handled AWFUL if the front pressure dropped below about 36 psi. I called it digital steering. I now run Dunlop radial Qualifiers on the 14 and they seem to be much more tolerant of low pressure. The CBR has OEM Bridgestone BT-015s and 6 psi too low in the front made them downright unstable. It might just be a Bridgestone thing but a lot of the guys on these forums have complained about heavy or unstable steering when running lower than recommended pressure in their street tires.

Kruz

* Last updated by: Kruz on 9/3/2009 @ 9:32 AM *

Kinda like a tire or oil thread...,
I run the RoadSmart's at 34/36 which is the highest PSI I've ever ran.
The Pirelli Corsa IIIs I usuallly run would be at 31/32 street and 27/28 plus 1 psi for cold days.
But the Pirellis as designed with soft sidewalls and work best if they give.
Had a fellow 14 rider ask Me and one of my high speed backroad buddies what to run saying he was at 42.
He had recently skidded off the road due to cold tires and had big bucks into rebuilding.
We strongly suggested less. Its usually only 50ish degrees here and need the flex to warm the tires. He went to 3 or 4 different sites asking same question.
I see his bike for sale as a wreck. Guess he liked the higher psi. Poor sucker.
In warm states it might not matter so much.
If you are staying close to legit it might not matter.
All tires feel different.
No one setting is gonna work make to make, model to model, bike to bike, region to region.
I can guarantee that you run that high of pressure with us with temps in the 50's we will be waiting for you. Tires wont stick as well when they are that hard. Nor will they warm for a long time.
As Assie was mentioning. If you can get that 2psi swing between hot and cold you are close to right.
If it takes forever or doesnt rise 2psi you are too high.

My dealer set my OEM tires to 36ish when I had it serviced right before last winter. I got my compressor working finally during the winter, and first project was checking the bike tires. Hmm.. I thought the manual said 42 psi?

Well, I took a little pressure out anyway, always like to store vehicles with lowered pressure in the tires.

This spring, I aired front and rear to 42 psi when I woke the bike up, and found it handled better than I remembered during its first season.

For how I ride, I just follow the specs of the tire manufacturer combined with the bike manual.

Man, I'm typing this on a small notebook computer and spending more time fixing miskeys than writing anything. How do kids text on cell phones anyway? LOL

You would think a back road is out of the way or out of town. That seems like enough of a heat set to keep the tire up to temp just getting there. Unless, skiff, it's right behind the house, you both start off with cold tires and one bites the dust, the other does not?

Someone mention an oil thread? Dis someone who can't ride with cold tires, if not watching MotoGP, someone goes off with a hot tire after a few laps going in? You would think a hot, low pressured tire has more grip, squeezing down a fatter profile? Less chance of slipping?

Just check tire flexing in these slow-mo videos. These guys would not even think of running 42 - 38 - not 34 psi. For optimal grip, the need to keep the pressure down.

* Last updated by: bgordon on 9/4/2009 @ 7:27 AM *

I like to run 40 psi in each (cold)

The stock 14 tires always felt best to me at 42/42. Any "truck-like" handling I've ever felt on my ZX was immediately attributed to low tire pressure - usually the rear, which seemed surprising. I check 'em often... Check your pressures often, guys - it may save you in an unpredictable situation...

Just check tire flexing in these slow-mo videos. These guys would not even think of running 42 - 38 - not 34 psi. For optimal grip, the need to keep the pressure down.

http://www.youtube.com/watch?v=U4bYGZfG0G4&feature=related
http://www.youtube.com/watch?v=IsrGPwKlpkM

These guys are insane... hope I never have to count on tire pressure if both wheels on the zx14 are up in the air.

V. Rossi said it during this last race- fun but very dangerous and it requires some serious guts.

These 600 ccs are jumping like dirt bikes...

Aussie,are we talking racing tires like BT-02s here? If so, I can agree that racers run lower tire pressures to get better cornering grip but street tires are constructed differently with regards to tire compound and construction.

Kruz - I'm talking about any "sports" tyres, def. including the OEM 014's. The Bridgeston 002's (which I assume is what you mean by 02? Or do you mean the old 012's?), which are now replaced by the new 003's (which I haven't yet tried) came in a a track-only version (with different compound hardness options) and the "002-RS" street-legal version. I'm getting off the track now though...my point being that what I spoke about in my post should apply to any rubber that is designed for "sports" riding on the street.

I can see that I'm not going to be able to convince many of you to drop down from 42, which is fine. Each to his own and of course everyone needs to feel safe, comfortable and confident at all times when on the bike.

Without wanting to be offensive...I think the problem is that some rider's are mistaking easy/quick steering (what they may call "handling") that their rock hard tyres give them, with the different but more positive/helpful benefits that are created by running at lower pressures. The grip that becomes avaiable if you get your rubber nice and hot 'n sticky, plus some flex in the tyre that allows it to put down a bigger contact patch under hard acceleration & braking, FAR outweighs that "easy steering/handling" you get with those rock hard, 42/42 tyres. Also with tyres at the "right" operating/hot temp (& therefore pressure), the rider (if they are experieced enough) can get a huge amount of feedback from their tyres, which is so, so important when pushing hard whether on the street or track.

Like skiffman was saying, if you aren't pushing your tyres hard enough to heat them up much, then running them at 42 may be fine for you. And for a new rider it may be better to start at higher pressures, for the sake of easier steering? I dunno. I guess if your riding doesn't heat the tyres up, and quickly, then it wouldn't be good to run them too low, as that may create more negative results than positive!

As for local weather making a difference, I'm sure it does to the cold/starting pressure, but I think the aim is always to get to the same operating pressure that is ideal for the bike, setup and rider...regardless of ambient temp. For the street though, it shouldn't be hard to find a supersports tyre that suits most seasons...the problem really is wet vs. dry...another story all together! Here in Queensland, Australia, it's bloody hot most of the year...but I was still going down to less than 30 PSI back & front on the OEM tyres when I was touring through the moutain twisties a few months back. Those OEM tyres aren't great, but I got them working ok with a bit of mucking around (still not great though).

* Last updated by: AussieNinja on 9/4/2009 @ 3:53 AM *

Good stuff Aussie.
Heres a little bit of info from a real pro.

Go back to page one for the skinny on warming tires.
Obviously a rider is going to fall back on what feels good to them.
I bought my RoadSmarts from a tire distributor who also happens to be the local suspension guru.
He did my fork valving and got my Penske for Me.
He suggested 32 as a starting point. I ended up adding a couple of psi.
New model to him and a lot more lbs. than the usual track bike.

http://www.sportrider.com/tips/146_0810_how_to_warm_up_new_tires/setting_cold_tire_pressure.html

* Last updated by: skiffman on 9/4/2009 @ 1:48 AM *

"You would think a back road is out of the way or out of town. That seems like enough of a heat set to keep the tire up to temp just getting there. Unless, skiff, it's right behind the house, you both start off with cold tires and one bites the dust, the other does not?"

Funny you mention it. I do live in the back roads!!!! People come from the urban areas to ride right where i live LOL
No, with our cool wet roads combined with firm tires it would be hard to keep up with our usual mix of built motards, sport bikes and I'm the only retard on a big fat bike.
So your point is right after 15-20 miles all tires would be up to temp.
A side note, most of the tard riders run below 25 psi !!! Light bikes no weight or large hp.

"Someone mention an oil thread? Dis someone who can't ride with cold tires, if not watching MotoGP, someone goes off with a hot tire after a few laps going in? You would think a hot, low pressured tire has more grip, squeezing down a fatter profile? Less chance of slipping?"

Those are the best in the world at speeds and lean angles we only dream of. They lost the front end all through the Indy race in all classes.
The mechanics soften everything for wet races. Suspension, power delivery, and tires plus psi.

I had a harder time with overheated street/track tires on track days with the 14. Than with them cold for the first 2,3 laps. Have a set of race tires now, but havent done a track day with them....,yet.
I was out of commission for 6 months due to a misjudgment on cold race slicks....,sigh, no tire warmers.
Wadded up my track only bike not the 14.
I'm NOT repeat NOT a tire expert or know much more than I've retained talking to the guys who do know. Racers, tire reps and distributors.
So definately seek from similar yourself.
Most dealerships are usual good for misinformation ;-(

* Last updated by: skiffman on 9/4/2009 @ 2:34 AM *

http://www.sportrider.com/tips/146_0810_how_to_warm_up_new_tires/setting_cold_tire_pressure.html

Heh heh...I know that article! Good one!

Actually I put my hand up admitting I used to weave around like a GP rider when trying to get my tyres up to temp (but also just coz it's fun and feels good!), but after reading that article a few months ago I started experimenting with just hard bursts of accel and hard braking. It works and makes a lot of sense.

Rook wrote :

I recently picked a cheap plastic compressor at Harbor Freight. It looks like a little yellow submarine. It only cost me $6 and it works great for bringing my tires up to pressure. I thought it might have a hard time with 42 psi but it seems to handle that fine (directions claim it will go up to 250 psi). The compressor plugs into a cigarette lighter. I don't think the gauge on the compressor is accurate but otherwise it works great. At 75 cents a fill at the station, this little baby should pay for itself in no time. If it breaks in a year, it will be worth the convenience of having it at home.

Heh I need to go to their website and get one. $6 for a compressor that will do 250 psi ? $$$$$$

On 12 volt car battery ? WOW !

My commercial Hitachi will only do 90 at the tank, and it cost more than 10 times as much.

This is turning into another oil thread, my original point was both my sportbikes feel unstable running lower than recommended pressure in the front, especially on low speed turn in. I never said anything about ultimate cornering grip or anything like that, just instability. Apparently I'm not alone on this, a lot of folks on here feel the same way. I'm talking street riding here, not track. If you push your tires on the streets to the edge of cornering grip you're an idiot and deserve to end up in a ditch. Just my .02

Kruz

* Last updated by: Kruz on 9/4/2009 @ 7:03 AM *

you're an idiot and deserve to end up in a ditch.

That's pretty full on mate. Not a cool thing for one biker to say to another, eh?

From what I've read, lower tire pressures equal faster wear. I run mine at 40 cold front and rear. They seem to stick great for my style of riding, and at 40 they ride a little softer than 42.

What I don't understand is that I was always told under inflation resulted in excess heat and risk of blow out. Perhaps 20-30 psi isn't classed as "under inflation" ?

When doing Californian Superbike School, the first thing they did was drop everyone's pressure (regardless of bike & tyre) down below 30 (can't remember what the exact figure was). They said O.E. pressures were good for reducing tyre wear, but not for grip. I then wonder is the fact that we would run the track for 20 minutes then have an hours break for more classes let the tyres not overheat????

Still pondering what the best pressure is for street riding.
What I also notice on the ZX14 (at 42psi f/r) is the front tyre fairly easily fully compresses onto the rim on severe bumps - I'm therefore inclined at the moment to keep the pressures up for day-to-day street use so as to protect the rim a bit. Perhaps drop them down when going out with ill intent!

Also thinking in winter (wet roads) a lower pressure would be better to increase tyre foot print and increase operating temperature.

The mysteries of life

Pretty much the point I was alluding to. hercsz
The cold wet part.
Dont think any tire on or bikes will work with below 30 psi on the street.
And hope to point out the difference between tires and bikes.

And riders...., sorry I hurt your feelings there Kruz.
Is there anything about wishing harm on another in that book you quote in your signature?
Good thing tomorrow is Sunday, Throw your .02 in the basket....,lol