Optimum tire pressure?

[oldslowguy]

There's been way too much googling of late. It's time to consult The Org. I've found a little discussion about XX tire pressure in prior threads here, but nothing too comprehensive.

After years of mindlessly following Honda's 42 PSI tire pressure recommendation for the 1999 XX, I've been trying lower pressures, with what I think are satisfactory results. By "lower", I mean 38-39 PSI. My reasoning was that, if 42 PSI is the correct number when the bike is fully loaded, then lower pressures should be OK--perhaps even better--if all it's carrying is little old me, who weighs in at about 165, including jacket, boots, gloves, helmet, and my very heaviest ear plugs.

So what do the rest of you consider the optimum tire pressure? If it isn't 42 PSI, what guided your choice of a different number?

[jblackbird2000]

It really depends on tire, road condition, and riding style.

I am running Pilot Roads, and if I'm just crusing back and forth to work, I keep it right up near 42 for both.

If I'm out playing a bit, then I like my pressures to be 38 up front and 40 in the rear. I've tried going lower in the front, but I personally don't like it lower than 38. But IIRC, some guys are running as low as 36 up front.

I'd say you're doing the right thing, keep playing with it until it's dialed in for your preference.

And look into buying lighter ear protection, my ear foamies don't weigh much at all.

[Furbird]

I run 38 front and rear myself. If it hits anything lower than 32 I can feel sluggishness in the turns and I know it's getting low.

[Justin]

I run 38 front and rear myself. If it hits anything lower than 32 I can feel sluggishness in the turns and I know it's getting low.

Same here.... you can really feel it when the tire pressure drops on the bird... As for pressure, I run 38 front, 40 rear... for long slab runs I'll put the bitch all the way up to 44-45

[bartonmd]

40F/42R commuting/sport-touring

35F/35R with Corsa III's for sport riding or trackday...

Mike

[XXSIVSPD]

I've played around with pressure alot in the last 3 seasons and it does depend on the tire.

When I first started running Pilot Powers the rear was toast at 3500 running 34F 36R but they stuck like glue. Started running 40F 42R slabbing, & 36F 38R in twisties. Got an extra 1000 to 1500 miles out of each rear & still got 1 front to 2 rears. They still stuck like glue in the dry but I lost a bit of wet grip. Not sure if that's due to lower carcass temps, smaller contact patch, or both.

Now I'm trying the Road 2s. At 40F 42R they seem like I could get 10k per rear & I've only slid 'em a few times. Once in the wet passing on turn exit crossing the yellow. Once in the dry being greedy with throttle leaned over, tires still cold. The few times I've dropped them down to 38R 36F grip levels seems awefully close to where the powers were and they take a little less time to warm up.

FWIW I tend to run front of I or back of A at track days, depending on org, & stay within my comfort zone on the street.

[The Krypt Keeper]

taking tire choice into consideration and then riding style..

if your going to cruise go with 42 for best wear and tread life.

Going to WVXXT this yr I went up to 42 front and back to slab it there in time to meet up with the group.

For riding in the twisties I prefer 36F 38R normally on these M3's I been keeping it around 38F and 38R

Check them often..

I do remember a buddy of mine telling me his bird felt kinda squishy. We were riding at a good pace. Popped out the tire gauge and he had.. 19lbs in the rear and 21 or so in the front. Had never checked the pressure within a yr.

[oldslowguy]

Thanks, gentlemen. It's good to know I wasn't off base when I decided to try lower pressures.

But when I saw the 19 PSI rear tire pressure, all I could visualize is someone watching the light turn green, then letting out the clutch lever--and going nowhere, because the rear wheel is spinning inside the tire.

For what it's worth: I was in the local AutoZone today, and persuaded myself to part with $30 to acquire one of these. I was pleased to discover that the box included a pencil type tire gauge that's just over three inches long! It's so small that it readily fits on the front wheel's valve stem, without me having to use a lot of bad language, like I do with all my other gauges. It appears to be accurate, too.

[John01XX]

oldslowguy,

You really should consider making a run down next weekend to Towanda Pa and hooking up in person with a large group of Bird owners from all over the country.

That is if you hadn't already planned on it !

You will see many good idea's for your Bird. I am coming from Florida and have the same Slime air kit packed for travel.

[Dion]

......But when I saw the 19 PSI rear tire pressure, all I could visualize is someone watching the light turn green, then letting out the clutch lever--and going nowhere, because the rear wheel is spinning inside the tire.

Actually the recommended range for power race tires is 21-24R 30F (the rears have a stiffer sidewall)

Powers I run@ 29-31F/R Of course I'm checking them with an IR thermometer right of the track and adjusting all day.

For hard riding on the bird try 32F/34R (this is with powers) You've got to check and tweek.

ymmv

[rideonXX]

According to a very senior rep of Parts Unlimited who has visited the major tire manufacturing facilities---the optimum balance of 'stick' and 'tire life' is at an increase of 10% in pressure from 'cold' to 'heated up' (approx 20 min of YOUR normal riding conditions. Happy trails kel

[RXX]

Thanks, gentlemen. It's good to know I wasn't off base when I decided to try lower pressures.

But when I saw the 19 PSI rear tire pressure, all I could visualize is someone watching the light turn green, then letting out the clutch lever--and going nowhere, because the rear wheel is spinning inside the tire.

For what it's worth: I was in the local AutoZone today, and persuaded myself to part with $30 to acquire one of these. I was pleased to discover that the box included a pencil type PIECE OF SHITtire gauge that's just over three inches long! It's so small that it readily fits on the front wheel's valve stem, without me having to use a lot of bad language, like I do with all my other gauges. It appears to be accurate, too.

Ha ha funny. I fixed it for you. I had a plug in my rear tire this summer out west, for about 2500 miles. I was pretty anal about checking the pressure at every gas stop (every 3 hours or 200-ish miles) I have a slime kit too, and they are very cool, btw. The little gauge BLEW UP on me though. Damn near put my eye out. I got my slime compressor for $10 after mail in rebate, so I can't complain.

I'm just sayin'

[oldslowguy]

Ha ha funny. I fixed it for you. I had a plug in my rear tire this summer out west, for about 2500 miles. I was pretty anal about checking the pressure at every gas stop (every 3 hours or 200-ish miles) I have a slime kit too, and they are very cool, btw. The little gauge BLEW UP on me though. Damn near put my eye out. I got my slime compressor for $10 after mail in rebate, so I can't complain.

I'm just sayin'

Yikes! What ungodly pressure was that tire inflated to? Now that I have my Slime pump, and the plug gun I bought about 10 years ago--well, I almost wish I would have a flat, just so I could see if I've purchased the right stuff. Well, just a little flat, in the garage, if possible. Not one of those flats where I scratch yet another handlebar weight. That's no fun.

For what it's worth: the latest TP numbers are 36 in the front, 38 in the rear. In particular, the lower number in back almost completely eliminates the bike's tendency to slither around on the ()*)(&^* tar squiggles New York's DOT thinks is OK for patching highways.

[RXX]

OK, so I got a new rear last week and was inflated to whatever PSI at 600’ or so above sea level. I assume I need to revisit since I am at >5000 ft? And going to 11,000 feet....

350 pound load total. Michelin Road 5 GT’s.

Thanks in advance!

[superhawk996]

From sea level to 5,000 feet your gauge will read higher by about 2.5 PSI with the same amount of air in the tire, not a huge difference.  For clarity; if you were at 40 psi at sea level and rode up to 5,000 that same gauge would read about 42.5.  Should one adjust for it?  Dunno.  If you had decided that 40 was perfect for you my gut says that you should run the indicated 42.5 instead of dropping it to 40, but don't know.  Never gave that any thought before.

[superhawk996]

This is assuming it's a normal gauge open to the atmosphere.  There are some calibrated gauges that are 'blind' to the atmosphere, that gauge would read 40 anywhere.

 

Also, this is all my theory, I could be totally wrong.

[JaBr]

I found this YouTube video to be very useful...

 

Dave Moss Tuning - Contact Patch

[tomek]

6 hours ago, superhawk996 said:

From sea level to 5,000 feet your gauge will read higher by about 2.5 PSI with the same amount of air in the tire, not a huge difference.  For clarity; if you were at 40 psi at sea level and rode up to 5,000 that same gauge would read about 42.5.  Should one adjust for it?  Dunno.  If you had decided that 40 was perfect for you my gut says that you should run the indicated 42.5 instead of dropping it to 40, but don't know.  Never gave that any thought before.

Yep, those are reference gauges. if it reads 40s psi at sea level absolute pressure inside of the tire is 40+14.7=54.7 psi. If you get to high elevation where atmospheric pressure is at 10 it is gonna read 54.7-10=44.7 psi. Absolute pressure inside of the tire won't really change, amount of air is constant,  and since the tire is not balloon the volume won't change either.

Tire has steel belts, etc. so it's shape won't change in relation to changes of atmospheric pressure. Unlike, let's say balloon Steve Fossett used to fly around the world.

 

So, don't do anything, tire pressure is fine.

 

 

 

Edited September 23, 2021 by tomek

[superhawk996]

3 hours ago, JaBr said:

I found this YouTube video to be very useful...

 

Dave Moss Tuning - Contact Patch

I think that's the first time I've heard someone advocate running the same pressure F&R.

[Banshee]

For me it's 42F/R.  Any lower & the bike wants to stand up in corners.

[SwampNut]

On the XX if I ran that high up front, it was shit.  Every other bike has been different, I can't think of any bike that tuned well at the same PSI front and rear.

 

EDIT:  I got my first good tuning advice on the XX from Avon, as they sent me some of their first XX-specific tires (rated for the speed and weight), and wanted good feedback.

[tomek]

Tire pressure? It depends on many, many factors. Many if not most of real performance tires run higher pressures in the front. 

  

 

Edited September 27, 2021 by tomek

[superhawk996]

17 hours ago, tomek said:

Tire pressure? It depends on many, many factors. Many if not most of real performance tires run higher pressures in the front. 

 

Are there similar charts for street sport tires?

 

I've always assumed that the rear could be run with less than the front just based on their size, but since all the factory recommendations are for more in the rear I assumed I was ignorant to something.

 

Just about every Jap sport bike I've looked at recommends 36/42.  The Ducs I had with the same size tires recommended lower, and from memory the F&R pressures were closer to each other.

[tomek]

2 hours ago, superhawk996 said:

Are there similar charts for street sport tires?

 

I've always assumed that the rear could be run with less than the front just based on their size, but since all the factory recommendations are for more in the rear I assumed I was ignorant to something.

 

 

Well, Dunlop Q3+ is a sport street tire, and good choice for up to mid level intermediate track riders. It is also recommended optional for my street VFR12 per Dunlop official web page. 

If you look at first chart from my previous post they recommended 28-32 cold, or before riding, air pressure. However, if you use tire search option from their page you end up with this.

   

 

 

[tomek]

42 psi. Confused yet? Lol.