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Tater
20th March 2010, 12:31
Has anyone run lower than recommended??? I am running 30# in my 19" front and 36# in the rear, and it just seems a bit road harsh to me, and I was thinking about trying 28# in the front and 32# in the rear, as I thing it would soften the harshness a bit, plus the slightly larger patch might increase traction...
Anyone else run simuliar pressures, or have any warnings, or input...???
Thanks and have a good one...Tater...

bigjnsa
20th March 2010, 12:34
Tater, I try not to. I can really tell the difference when i'm nearing 30psi in both tires. There is a wishy washy feeling in the turns.

ReddTigger
20th March 2010, 12:43
running too low causes the tire to flatten out and you'll end up running only on the edges of the tires, instead of the entire tire. you'll lose contact patch, heat the tires more then normal sometimes to the point of failure.

Not recommended.

TripleDuck
20th March 2010, 13:26
The pressure marked on the side wall is maximum pressure and should be used if carrying the maximum weight (also marked on sidewall). This is not a likely scenario. So, in real life, we have to do a little simple math.

A simplified version of the formula the tire reps use at the race track....

1. Add max weight ratings from tire
2. Add actual weight (bike's weight+your weight+cargo weight)
3. Divide actual weight by max weight
4. Multiply sidewall pressure rating by factor determined in "3"
5. That is your starting point.
Note: this starting point calculation does not account for temperature or riding style.

Important: Use actual weight - your bike full of gas and your butt full of taco's wearing that fancy leather weighs more than you think.

Real life
Rear tire rated 761#@41psi
Front tire rated 507#@41psi
max = 1268#
bike weight 570#
butt weight 200#
cargo 20#
actual 790#
770/1268 = .62
.62*41 = 25.4 psi starting pressure.



THIS IS NOT TO LOW. The rule of thumb is a 10% rise in pressure before/after ridinga track session. This also applies to street riding for best grip and longevity.

With a typical South Texas day in the high 80's, we run about 27psi cold in the sportster and will measure ~30psi after 20 miles or so in the saddle.

ride safe bros

ReddTigger
20th March 2010, 13:35
The pressure marked on the side wall is maximum pressure and should be used if carrying the maximum weight (also marked on sidewall). This is not a likely scenario. So, in real life, we have to do a little simple math.

A simplified version of the formula the tire reps use at the race track....

1. Add max weight ratings from tire
2. Add actual weight (bike's weight+your weight+cargo weight)
3. Divide actual weight by max weight
4. Multiply sidewall pressure rating by factor determined in "3"
5. That is your starting point.
Note: this starting point calculation does not account for temperature or riding style.

Important: Use actual weight - your bike full of gas and your butt full of taco's wearing that fancy leather weighs more than you think.

Real life
Rear tire rated 761#@41psi
Front tire rated 507#@41psi
max = 1268#
bike weight 570#
butt weight 200#
cargo 20#
actual 790#
770/1268 = .62
.62*41 = 25.4 psi starting pressure.



THIS IS NOT TO LOW. The rule of thumb is a 10% rise in pressure before/after ridinga track session. This also applies to street riding for best grip and longevity.

With a typical South Texas day in the high 80's, we run about 27psi cold in the sportster and will measure ~30psi after 20 miles or so in the saddle.

ride safe bros

nice math lesson, however, According to all the tire manufacturers this tire pressure you're recommending is to low..

Dunlop (OEM replacement tires) Typical is around 30psi front.. 36 rear.
Metzeler recommends at least 36 front and 38 rear (SOLO riding)
Avon is also similar.

Now Maybe a racing tire has different results but for street riding, I recommend following the manufacturers recommendations.

FoxsterUK
20th March 2010, 14:11
The pressure marked on the side wall is maximum pressure and... Actually, on Metzeler tyres, the number is the recommended normal pressure, not the max.

Tater
20th March 2010, 14:20
Thanks Folks, so I am running about what I am supposed to be running, and for sure not too high pressure @ 30# Frt. & 36# rear, and you agree with the owners manual...
Thanks, I'll stick with that, as tire wear & non-cupping (so far)(3K) looks pretty darn good... (BTW-tires are Dunlop originals)...
And I do try to ride the twisties, got in 220 mi. of pretty good riding yesterday (wore me out though)...lol...
I do run the max on the tire sidewall on my PU & car...
I was just thinking that it might help the ride & traction a bit, but I guess
the best thing besides that or a Mustang seat would the buns of steel work out like the wife does...lol...
Thanks Folks and have a good one...Tater...

TripleDuck
20th March 2010, 14:27
Actually, on Metzeler tyres, the number is the recommended normal pressure, not the max.

I don't have a metzler in the garage right now...you could be right.

However, the tire manufacturer has no idea what bike a specific tire will be mounted on. The bike/rider may weigh 400# or they may weigh 700#. If you want to ride the same tire pressure regardless of load.....knock yourself out.

I've got a few track laps on my butt and have attended more than a couple tech sessions on tire pressure - its a topic of constant discussion in the performance bike arena. The public information has liability all over it - because the manufacturer cannot predict what tire the bike is to be mounted on. Go talk to a tire rep - a manufacturer's tech rep (not a minimum wage tire salesman). In public forum, they will talk the "published pressure". Out of media ear shot (like at the race track) you will get a different story....and yes street tires are developed on the track....the same rules apply.

my suggestion is do what makes you comfortable and feel safe. I'm just sharing a little bit of info gleened over the last 42 years of motorcyling and works fine for me and my loved ones.

ride safe bros

a45junkie
20th March 2010, 15:01
most manufacturers have a chart for their tires for different bikes i use what they say

khaskins
20th March 2010, 15:04
Low tire pressure causes sidewall failure. Can any one say Firestone tires and Ford SUVs and Trucks. Remember, it was not that long ago.

XLXR
21st March 2010, 06:12
Low tire pressure can cause the rim to bottom out hard against a sharp edged corner like the edge of a big pot hole. That can cause the tire to blow out instantly. If I run 30 or lower in the front, the rim will bottom out.

The larger rear tire can run lower air pressure and not bottom out the rim at the same pressure that a smaller front tire will bottom.

Too much air pressure can reduce the contact patch and reduce hard braking effectiveness.

I had to run 40 psi in stock front Dunlops to minimize squirming at highway speeds. With Metzlers, I run 33 front and 30 Rear. I will increase pressure 2 lbs front and 5 rear if I am carrying extra weight or doing a lot of highway miles. I set my tire pressure based on how the bike feels in corners, hard braking, at highway speeds and try to balance the feel of the suspenson between front and rear. On my Ducati with radial tires, I run 35 front and rear. I have been told that radial tires do not respond to ranges of air pressures like bias ply tires do. That seems to be true.

A few years ago I measured tire temperatures with an infared temp guage at various pressures. You have to seriously under inflate a tire to get a big temperature gain. Speed has a big effect on tire temperature. They cool off very quickly when you stop.

flathead45
21st March 2010, 06:17
I run my front at the full pressure but my rear I run about ten pounds low (solo) and 5 lbs low two up. gives me the best feel for my stiff bike. (fx shocks)

Nitro Circus
21st March 2010, 09:33
The pressure marked on the side wall is maximum pressure and should be used if carrying the maximum weight (also marked on sidewall). This is not a likely scenario. So, in real life, we have to do a little simple math.

A simplified version of the formula the tire reps use at the race track....

1. Add max weight ratings from tire
2. Add actual weight (bike's weight+your weight+cargo weight)
3. Divide actual weight by max weight
4. Multiply sidewall pressure rating by factor determined in "3"
5. That is your starting point.
Note: this starting point calculation does not account for temperature or riding style.

Important: Use actual weight - your bike full of gas and your butt full of taco's wearing that fancy leather weighs more than you think.

Real life
Rear tire rated 761#@41psi
Front tire rated 507#@41psi
max = 1268#
bike weight 570#
butt weight 200#
cargo 20#
actual 790#
770/1268 = .62
.62*41 = 25.4 psi starting pressure.



THIS IS NOT TO LOW. The rule of thumb is a 10% rise in pressure before/after ridinga track session. This also applies to street riding for best grip and longevity.

With a typical South Texas day in the high 80's, we run about 27psi cold in the sportster and will measure ~30psi after 20 miles or so in the saddle.

ride safe bros

Were these calculations for bias or radial? As XLXR said, they respond quite differently to tire pressure/temperature changes - radials are much more stable.

flashedwards
21st March 2010, 09:56
When I first got my 1200N it felt like I was riding in a cross wind that came and went on the freeway. The tech. at the dealer tightened up the fork head bolt just a tad and recommended that I run 36 pounds in the front not 30. That made a huge difference...and when I added a fork brace it really was rock steady. Adding those xtra pounds of air to the front made a huge difference..it didn't follow the cracks in the pavement like it used to.
Flash

Tater
21st March 2010, 12:58
I just wondered about the pressures, especially the front tires, since they seem to make no difference between the 21" smaller diameter tire and the 19" somewhat larger diameter tire pressures in the owners manual...
I have always though the larger diameter tire would require less pressure under the same load...
Thanks and have a good one...Tater...

whittlebeast
21st March 2010, 13:27
I have to go with XLXRs explanation on this one. For what it is worth my 900 lb racecar runs 15 psi on bias plys, my 400 lb shifter kart runs 11 psi with bias plys and my 1700 lb Civic racecar runs 36 psi on radials. In all three vehicles, the only thing that matters is the time from point a to point b. My point is all three of these have tire pressures to control very different issues and the pressures compared to weight defies logic.

Remember that almost everything that a dealer tells you is some sort of answer to maximize their profit balanced against the answer given by a lawyer. Sadly, your happiness is farther down on their list of priorities.

AW

whittlebeast
21st March 2010, 13:51
Regarding pressures that the racers use compared to the pressures that street bikes require. Race vehicles almost never deal with potholes and other such obstacles that cause the wheel to snake bite the tire/tube. The recommended tire pressure on a streetcar tire has everything to do with what is known in the industry as the government brick test. It is a balance act of peak pressure in the tire and not snake biting the tire. Ask those same tire engineers what pressure to run to get the best lap times and they will tell you to start 10 lbs higher and see how it feels.

AW

Bone
22nd March 2010, 16:07
Personally I prefer to run my tires on the higher end - a little above recommendations for firmness and mileage. I rarely run them at so high a pressure that I feel any traction difference.

That said, Metzler typically recommends running their tires at higher pressures than what many bike OEM's recommend for other brands (like Harley with their DungFlops).


Actually, on Metzeler tyres, the number is the recommended normal pressure, not the max.

This is not my experience.

And I wonder if tire manufacturers are required by law (in the US or the EU) to label tires with the max number.

As TripleDuck points out the tire manufacturer doesn't know what bike (size, weight load) its tire will wind up on, the BIKE manufacturer gives the recommendation (and sometimes the tire manufacturer will publish their own specs on their website for bike and tire combos) but what's on the sidewall is normally a MAX pressure for MAX load rating NOT the recommendation.

FoxsterUK
22nd March 2010, 17:25
Personally I prefer to run my tires on the higher end - a little above recommendations for firmness and mileage. I rarely run them at so high a pressure that I feel any traction difference.

That said, Metzler typically recommends running their tires at higher pressures than what many bike OEM's recommend for other brands (like Harley with their DungFlops).




This is not my experience.

And I wonder if tire manufacturers are required by law (in the US or the EU) to label tires with the max number.

As TripleDuck points out the tire manufacturer doesn't know what bike (size, weight load) its tire will wind up on, the BIKE manufacturer gives the recommendation (and sometimes the tire manufacturer will publish their own specs on their website for bike and tire combos) but what's on the sidewall is normally a MAX pressure for MAX load rating NOT the recommendation.My experience is also that most tyre manufacturers put the max pressure on their tyres and they label it so. However with Metzeler tyres they deliberately do not say its the max pressure but the recomended pressure.

You can check this here: http://www.us.metzelermoto.com/web/fitment/metzeler/selectSearchTyresForm.do?mySelectActived=confirm&myEntryPoint=%2Ffitment%2Fmetzeler%2FhomeMotoFull&brandVehicle=4967&modelVehicle=109760&versionVehicle=217540&consent=Y where it tells you the recommended pressures for their tyres and you will find this is the same pressure on the side of their tyres.

Bone
22nd March 2010, 18:17
My experience is also that most tyre manufacturers put the max pressure on their tyres and they label it so. However with Metzeler tyres they deliberately do not say its the max pressure but the recomended pressure.


I cannot imagine why the UK would be any different, but I've been using Metzler tires as my exclusive replacement for OEM tires since the mid-90s and I don't recall ever seeing what you are claiming.

As a matter of fact I just spent ten minutes in the garage with a flash light, I checked the FIVE metzler tires that are currently on our 3 bikes and EVERY SINGLE ONE SAID a variation of

"Max Load ____ Kg (____ lbs)
at ____ KPA (___ psi)"

I say a variation because one of them was an ME 88 Marathon which said

"Max Load 375 Kg at 340 KPA
Max Load 827 lbs at 50 PSI"

More importantly every single one listed a pressure that was higher than either the bike manufacturer's recommendation and/or the recommendation of Metzler in that application chart.

So NO Metzler tire in my possession lists the "recommended" pressure, only the MAX.



You can check this here: http://www.us.metzelermoto.com/web/fitment/metzeler/selectSearchTyresForm.do?mySelectActived=confirm&myEntryPoint=%2Ffitment%2Fmetzeler%2FhomeMotoFull&brandVehicle=4967&modelVehicle=109760&versionVehicle=217540&consent=Y where it tells you the recommended pressures for their tyres and you will find this is the same pressure on the side of their tyres.

Well, their fitment chart helps my point, since of my three bikes, 3 of the 5 metzler tires I currently have installed aren't even listed as options.

The Harley currently has a 140/90/16 on the rear not the 150 or 160, sidewall says "Max 50 psi" - not the 40 PSI that both the 150 or 160 are "recommended" in that application.

Same is true for the Guzzis, even the one where the OEM front tire was still installed. The sticker on the bike said 36 PSI Front, the Metzler website said 32 PSI Front (same tire), the sidewall said "Max Load 257 Kg (567 lbs) At 290 KPA (42 PSI) Cold."

Interestingly even the Metzler website can't be fully trusted as they list different PSI for the same tire on what is essentially the same bike two different years (or essentially same bike in the same year). Sometimes 36 PSI and sometimes 32 PSI (front tire, another Guzzi, two variants of the California models). In both cases OEM lists 33 psi, but the sidewall on the replacement Metzler (from the Metzler application chart) says "Max 42 psi".


So I'm left puzzled with your Metzlers.

Wonder if someone else can chime in...

linkin5
22nd March 2010, 18:20
The OP mentioned traction as an issue, anybody here have any traction issues? I haven't ever had traction issues on any bike with any tire at any pressures, well there was this one time I rode on a flat rear for about 60miles and then there were some issues.

FoxsterUK
22nd March 2010, 18:34
Well that is odd. I'll go investigate :geek

Tater
22nd March 2010, 19:04
The OP mentioned traction as an issue, anybody here have any traction issues? I haven't ever had traction issues on any bike with any tire at any pressures, well there was this one time I rode on a flat rear for about 60miles and then there were some issues.
Is my bike that much stronger than others...lol...
I was thinking mostly about take offs, I know my vn750 had a bit less torque and the grip and take off were about a perfect match, but its pretty easy to breah the rear loose on this bike, or my clutch is slipping one...lol...
Naw, really no traction issues, and I didn't think I said it was an issue, I was just wondered if it might increase the traction a bit, or whatever...
Have a good one...Tater...

Bone
22nd March 2010, 19:20
Naw, really no traction issues, and I didn't think I said it was an issue, I was just wondered if it might increase the traction a bit, or whatever...
Have a good one...Tater...

It does, to a point, I believe drag racers tend to run lower pressures for this reason.

But like everything there is a trade-off, and once you past a certain point the benefit is not only lost but it goes the other way (law of diminishing returns).

XLXR
24th March 2010, 08:11
The OP mentioned traction as an issue, anybody here have any traction issues? I haven't ever had traction issues on any bike with any tire at any pressures, well there was this one time I rode on a flat rear for about 60miles and then there were some issues.

There is a pressure range where their is not much difference, but if you go to either extreme of too low or too high there will be differences. A lot depends on a riders skill to be able to feel the changes. A 10 lb difference should be easy to tell. A 3 lb difference at the extreme ends should be noticable. A 3 lb difference in the middle of the range may not be felt at all.

Weo
24th March 2010, 10:40
Be careful not to go too low on the front tire. If you go too low you'll develop a tank slapper at higher speeds. I learned this the hard way on my sportbike.