Yet another tyre pressure thread...
 

So the manual for R1200S states recommended tyre pressures to be set to:
front = 2.2 bar (32 psi), rear 2.5 bar (36 psi).
Stock tyres were Metzeler Sportec M1 and that tyre pressure worked fine for me, up until i got a rusty nail in the rear so I had it patched up.

So a few days ago I bought a new set of Metzeler Sportec M3 and I come home check the pressure and it's like 2.9 bar (42 psi) front and rear, so i deflate them to 2.2 front and 2.5 rear.

Today I go to work and the tyres look like they're sagging a bit, so i check the pressure and it's as i left it over the weekend, but it doesn't feel that good on the road. I'm now looking at the Metzeler website and they list the following tyre pressures for M1 and M3:
front = 2.5 bar (36 psi), rear 2.9 bar (42 psi).

Who should I trust then? I'm inclined to inflate the M3s to Metzeler's specs, but I don't have enough experience to decide what's better. Any thoughts?

According to a Metz/Pirelli tech, you should follow the tire manufacturer's recommendations, not the bike manufacturer as tire specs change even within the same tire.

That said, I usually follow the bike, but if this feels a bit squigly just up it a few pounds. I look at these things as a guideline anyway. Tire pressures are as personal as riding styles.

I usually compromise a bit between the two and then throw in my own usage and weather as well. But I always use the bike's OM (not the tire mfg who I think just tends to make blanket recommendations for huge classes of bikes) as the starting point. I'll go up/down a few psi to try and get neutral steering - I hate having to hold bar pressure in a turn.

32/36 sounds low - I suspect that's with a very light load, so except for the track, I'd tend to go a little higher.

When you're stretching a tire to make it home, go higher, up to the limit on the tire sidewall. My experience is that bumping from 36 to 44 psi will double how long that remaining tread will go to get you home.

- Mark

Thanks for the advice.

I put more pressure in, 2.4 front and 2.8 rear and the ride feels better. But that's completely subjective ofcourse.

I was running 34/38 in my M3's but I'm a big guy ~115kg and they felt good MOST of the time, they got a bit squigly when pushed.
They also flattened out a lot. But that's a combo of commuting and being a big guy.

I was happy with the feel and the wear on the fronts so I went up just 1psi to ~35 and I upped the rear to 40. Much better, and no squigly feel even with my weight.
I can't notice a loss of traction with that 2psi change.

I've not tried 42, because I'm happy @ 40. :)

Ant

Seems to me that there is NOT one proper tire presure number. Depends on rider weight, type of tire, and type of riding. I never liked the feel of 36/42 for aggressive sport riding. Didn't "feel" right for good traction. But, I'm also only 142 lbs. I like 33/35, give or take a pound.

I'm with Mark on this.

The tire manufacture doesn't know if the tire is going on a 375 or a 575 lb bike (and in extreme cases, even wider ranges) so their blanket recommendation can't possibly be right. (except when they've spec'd an actual application chart, but even then, they often look like devoid-of-weight-context generalizations)

Otoh, the bike manufacturer doesn't know what the tire's construction is, except for that one particular tire, and even then only of the same generation, and thus can't be sure of pressure appropriate for your subsequent tire choice.

So, like Mark, I say fudge it in between and tweak to suit. And as Mal said, the rider weight and preference are further variables. Hard to objectively defend much different of an approach.

I am in the camp which recommends that you adjust the pressure to the weight being carried by the tires and you desired result.

Will add that unless you have dropped the coin for a gauge whose accuracy is certified and has a temperature adjustment chart, there is no sense getting worked about plus or minu a couple of PSI. For that is about as close to the actual as the typical gauge is going to get.

tires help make you go.
they help make you stop.
rumor has it, they even pitch in when you're in the corners, and do somethat good.

in addition to all those nice attributes, tires perform an even more important function by being the front line of your suspension system. they're always the first to get there, the first to react and the only factor that decides how much energy is passed to the "rest" of the suspension.

get a great air pressure gauge. become exceptionally anal about tire pressures. keep a log. always approach tires as though they were tires, but more importantly, part of the bike's suspension.

in nascar, a one pound change in tire pressure is the equivalent of a 60 pound change in spring rate.
not sure how all that translates to bikes, but it's easy to experience: jack up the tires to the max, go ride a little while.
traction will be on par with the Barbie Malibu Corvette.

bleed the tires down to the middle, ride some more, notice you're not playing slip & slide anymore, the ride is smoother, the feel is more confident.

then run them down to "too low". bike gets squirmy, sluggish, vague. tip-toe your way back to compressed air.

that's phase 1.
phase 2 is learning how to separate front and rear pressures in your head, and discovering how they effect the bike.
if you get to phase 2, you're better than most.

phase 3 and up is all about sidewall flex, different brands, compounds, tire profile, etc...things most of us don't understand, feel, notice or know about.


screw the stickers. nose-thumb the manual.
play with the pressures. feel the feel. you'll get the hang of it.

I can actually feel the difference between 1 pound more or less, but really, on the street, I'd say as long as you're in the ballpark, who cares. It is not the track. We are not being timed. We are not trying to run as fast as we possibly can. There is a difference between tweaking the pressure to get the max out of it and being safe.

my goal is to find something that works over a reasonable range of requests, then just stay on top of it by being anal about the pressures being set correctly.

i find a brand/size i like and tend to stick with it. i like the comfort zone of consistency.

i'm trying to remember how much air bleeds out of a tire naturally. 1% every 24 hours? something like that....

(having used the SmarTire system (as did steve carlton), you learn a lot of real-time info about what your tires are actually doing. you can see heat cycles come and go and you can dial in a sweet spot based on temperature by varying psi until you find what "sticks" the best. it's yet another way to approach it).

here's a third way: we used to totally toss the tire gauge sometimes, and instead would measure the OD of the tire to adjust the pressures. when the tire was XX millimeters large when measured around the peak, it was good to go. if the tire had 6 laps on it, that mm number would be adjusted. ya don't see anybody doing that anymore. probably a good reason too.

Its TIRE by the way.........:confused:

yea dang it, and they're usually all the same "colour" too.
i know. i went to University!
sheesh~!

Yes, you ARE confused.

> Its TIRE by the way......... :confused:



"Tire?" Not in the majority of the world :confused:

yeah and it is "it's", by the way :D

It's is possesive, its is the contraction for it is.

:confused:

they're you have it

Sorry. Other way around.

Tire pressure experts are like the motor oil gurus, whatever suits your riding style is usually a perfect number.If you keep the psi close to the tire gods specs, you are in good shape.Plus or minus a few psi won't make a huge difference..

Point being, there is supposed to be an apostrophe in it... :D