Tire pressure
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2nd Gear
Joined: Sep 2018
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From: Pittsburgh, PA
Tire pressure
I noticed my tire pressure was low, brought it up to recommended, now it feels like s***. Roads around here suck. Friend of mine recommended going 5 pounds under recommended pressure, which is about where it was when I recognized it was low. Felt pretty good. Wondering if anybody has any thoughts on that. Thanks
Last edited by 18Slim; Jul 24, 2019 at 05:10 PM.
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From: Honah Lee
Under 140 over 90..Ups..wrong thread. Don't listen to your friend. Put them to the manual. Find better roads. Think most are running Michelin but if you still run Harley's Lopps, next tire switch to Michelin.
Made a world of difference on my bike.
Running them 5 lbs lower since they are not radial or steel belt may not affect them. Not really sure. However, running a steel belt radial low will cause the belts to fail near the end of the tires life. Then, they will develop bubbles in the weak area.
Made a world of difference on my bike.
Running them 5 lbs lower since they are not radial or steel belt may not affect them. Not really sure. However, running a steel belt radial low will cause the belts to fail near the end of the tires life. Then, they will develop bubbles in the weak area.
Last edited by Jackie Paper; Jul 24, 2019 at 05:16 PM.
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From: Great State of Canada
I've been using a slightly modified version of this method which has resulted in my running my 2014 Breakout tire pressures at 37 psi both front and rear. The recommended pressures are 42 PSI, (42 psi = the tire's MAXIMUM LOAD RATING).
This seems like a lot of diddling around but in point of practical fact it is not and I quickly was able to determine that 37 psi cold so commonly resulted in 41 psi hot that I just check my tires are at 37 psi now before heading out, regardless of ambient temps. I've now been through 4 sets of tires using this method. I use Ride-On to balance and regularly change tires when wear bars are hit and have yet to experience problems of any sort. The tires perform very comfortably and very well and the (fat) rear, in particular lasts about 1000 km longer than when pumped to the max, thats about a 20% life improvement. I run Dunlop E3's F&R. You'll notice my method involves a 10% differential for the rear tire not 20% per Kelly's method. This owes to another essay I read which stated that running a tire at less than 20% for even a short distance can ruin it irrecoverably so I've exercised an abundance of caution owing to that theory.
I'm not interested in a debate BTW, this is just what I do FWIW.
Ride safe.
.
From Larry Kelly on the Ducati.net List
Determining Best Tire Pressures
You'll get a lot of opinions on what tire pressure to run, but the correct tire pressure for you is not a matter of polling other rider's opinion. Here are the basics you'll need to decide for yourself.
Start with the bike manufacturer's recommendation in the owners manual or under-seat sticker. This is the number they consider to be the best balance between handling, grip and tire wear. Further, if you're running alloy wheels on poor pavement, consider adding 2 psi to the recommended tire pressure just to reduce the likelihood of pothole damage. Just as you would for a car, increase the pressure 2 psi or so for sustained high speed operation (or 2-up riding) to reduce rolling friction and casing flexing. Check your tire pressure regularly as they say.
In order to get optimum handling a tire has to get to its optimum temperature which is different for each brand of tire. Most of us don't have the equipment needed to measure tire temperature directly so we measure it indirectly by checking tire pressure since tire pressure increases with tire temperature. Tire temperature is important to know because too much flexing of the casing of an under-inflated tire for a given riding style and road will result in overheating resulting in less than optimum grip. Over-pressurizing a tire will reduce casing flexing and prevent the tire from getting up to the optimum operating temperature and performance again suffers. Sliding and spinning the tires also increase tire temperatures from friction heating.
A technique for those wanting to get the most out of their tires on the street is to use the 10/20% rule.
First check the tire pressure when the tire is cold. Then take a ride on your favorite twisty piece of road. Then, measure the tire pressure immediately after stopping. If the pressure has risen less than 10% on the
front or 20% on the rear, the rider should remove air from the tire. So for example, starting at a front tire pressure of 32.5 psi should bring you up to 36 psi hot. Once you obtain this pressure increase for a given rider, bike, tire, road and road temperature combination, check the tire pressure again while cold and record it for future reference.
Each manufacturer is different. Each tire model is different. A tire design that runs cooler needs to run a lower pressure (2-3 psi front) to get up to optimum temperature. The rear tire runs hotter than the front tire, road and track. So the rear tire cold-to-hot increase is greater. Dropping air pressure has the additional side effect of scrubbing more rubber area.
When I used the tire pressures recommended by Ducati (32.5F/36R) for my 916 on my favorite road, I got exactly 10/20% on a set of Bridgestone BT-012SS. So I guess I'm an average rider and the BT-012SS runs at an average operating temperature compared to other brands.
For the track you'll have to drop the cold tire pressures an additional 10/20%. Track operation will get tires hotter (increasing the cold-to-hot pressure range) so starting at say 32/30 psi now should bring you up to the
same temperature (and pressure) that 35/39 psi gave you for the street.
Don't even think about running these low track cold pressures on the street.
Finally, dropping tire pressures on street tires for track use has its limitations, so street compound tires on the track often get too hot and go beyond sticky to greasy. That's why you have race tires. Race tire compounds are designed for severe operation at these higher temperatures for a limited
number of thermal cycles. On the other hand, race tire on the street usually won't get up to the appropriate temperature for good performance. At street speeds, the race compound often won't perform as well as a street tire.
Larry Kelly
'95 916
Determining Best Tire Pressures
You'll get a lot of opinions on what tire pressure to run, but the correct tire pressure for you is not a matter of polling other rider's opinion. Here are the basics you'll need to decide for yourself.
Start with the bike manufacturer's recommendation in the owners manual or under-seat sticker. This is the number they consider to be the best balance between handling, grip and tire wear. Further, if you're running alloy wheels on poor pavement, consider adding 2 psi to the recommended tire pressure just to reduce the likelihood of pothole damage. Just as you would for a car, increase the pressure 2 psi or so for sustained high speed operation (or 2-up riding) to reduce rolling friction and casing flexing. Check your tire pressure regularly as they say.
In order to get optimum handling a tire has to get to its optimum temperature which is different for each brand of tire. Most of us don't have the equipment needed to measure tire temperature directly so we measure it indirectly by checking tire pressure since tire pressure increases with tire temperature. Tire temperature is important to know because too much flexing of the casing of an under-inflated tire for a given riding style and road will result in overheating resulting in less than optimum grip. Over-pressurizing a tire will reduce casing flexing and prevent the tire from getting up to the optimum operating temperature and performance again suffers. Sliding and spinning the tires also increase tire temperatures from friction heating.
A technique for those wanting to get the most out of their tires on the street is to use the 10/20% rule.
First check the tire pressure when the tire is cold. Then take a ride on your favorite twisty piece of road. Then, measure the tire pressure immediately after stopping. If the pressure has risen less than 10% on the
front or 20% on the rear, the rider should remove air from the tire. So for example, starting at a front tire pressure of 32.5 psi should bring you up to 36 psi hot. Once you obtain this pressure increase for a given rider, bike, tire, road and road temperature combination, check the tire pressure again while cold and record it for future reference.
Each manufacturer is different. Each tire model is different. A tire design that runs cooler needs to run a lower pressure (2-3 psi front) to get up to optimum temperature. The rear tire runs hotter than the front tire, road and track. So the rear tire cold-to-hot increase is greater. Dropping air pressure has the additional side effect of scrubbing more rubber area.
When I used the tire pressures recommended by Ducati (32.5F/36R) for my 916 on my favorite road, I got exactly 10/20% on a set of Bridgestone BT-012SS. So I guess I'm an average rider and the BT-012SS runs at an average operating temperature compared to other brands.
For the track you'll have to drop the cold tire pressures an additional 10/20%. Track operation will get tires hotter (increasing the cold-to-hot pressure range) so starting at say 32/30 psi now should bring you up to the
same temperature (and pressure) that 35/39 psi gave you for the street.
Don't even think about running these low track cold pressures on the street.
Finally, dropping tire pressures on street tires for track use has its limitations, so street compound tires on the track often get too hot and go beyond sticky to greasy. That's why you have race tires. Race tire compounds are designed for severe operation at these higher temperatures for a limited
number of thermal cycles. On the other hand, race tire on the street usually won't get up to the appropriate temperature for good performance. At street speeds, the race compound often won't perform as well as a street tire.
Larry Kelly
'95 916
I'm not interested in a debate BTW, this is just what I do FWIW.
Ride safe.
.
Last edited by HKMark23; Jul 24, 2019 at 06:04 PM.
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2nd Gear
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From: Pittsburgh, PA
This is good stuff. Thanks. I don't know a whole lot about tires, but enough that -5 psi probably wasn'ta great idea. Harley Dunlops, recommended 36 front, 40 rear. It is a STIFF, slamming ride. Will look at 10/20% and see what I come up with.
Road Captain
Joined: Nov 2018
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From: Hendeson, NV
Tire Pressure and Rear Shock Pre-load Must Work Together
I have bought two bikes in the last 12 months. BOTH of them were delivered with tire pressures that were about 6 lbs under inflated. A mechanic told me this was normal because of the belief that under inflated tires provide a softer rider and avoid the sales department having to adjust the pre-load on the rear shocks during the test ride process.
I spent about a month last year researching tire pressure. I highly recommend Pat Hahn's book Maximum Control, Mastering Your Heavyweight Bike for an excellent discussion of the effects of tire pressure on riding and handling characteristics of a bike. A summary of my research is that the tire pressure recommended in your owner's manual is the best place to initially set your tire pressure. It can then be adjusted ONE POUND AT A TIME for temperature, road conditions and your desired "feel". Check your cold tire pressure at least weekly, more often if your roads are poor.
Based on Hahn's discussion and other research, IMHO you will safely achieve more improvement in adjusting for rough local road conditions by reading your owner's manual and adjusting the rear shock pre-load than trying to compensate by under inflation of tires. You should also find your bike more stable and have better tire life once your rear shock pre-load and tire pressure settings are properly adjusted close to the factory recommended settings for your weight plus any added weight--such as heavy options, a passenger and luggage. BTW: The owner's manual for my 2019 Low Rider has an excellent discussion on tire pressure and recommended settings as well as adjustments needed for changes in ambient temperature.
I spent about a month last year researching tire pressure. I highly recommend Pat Hahn's book Maximum Control, Mastering Your Heavyweight Bike for an excellent discussion of the effects of tire pressure on riding and handling characteristics of a bike. A summary of my research is that the tire pressure recommended in your owner's manual is the best place to initially set your tire pressure. It can then be adjusted ONE POUND AT A TIME for temperature, road conditions and your desired "feel". Check your cold tire pressure at least weekly, more often if your roads are poor.
Based on Hahn's discussion and other research, IMHO you will safely achieve more improvement in adjusting for rough local road conditions by reading your owner's manual and adjusting the rear shock pre-load than trying to compensate by under inflation of tires. You should also find your bike more stable and have better tire life once your rear shock pre-load and tire pressure settings are properly adjusted close to the factory recommended settings for your weight plus any added weight--such as heavy options, a passenger and luggage. BTW: The owner's manual for my 2019 Low Rider has an excellent discussion on tire pressure and recommended settings as well as adjustments needed for changes in ambient temperature.
Last edited by Las Vegas Jim; Jul 25, 2019 at 09:35 PM. Reason: One phrase addition.
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Those that suggest under inflating tires don’t remember the Ford Explorer & Firestone fiasco. Ford decided the easiest way to lower the center of gravity, and reduce rollovers, was to under inflate the tires. Then they had serious accidents, with fatalities, due to tire failures.
