Air pressure effect on tire wear

[Giblet]

I'm installing the second set of Dunlop D404's on my 82 GK. The shop manual etc recommends 40psi when the passenger load is over 170lbs. Since I weigh a biscuit & a spoon full of gravey shy of 200lbs, this what I have been running. I ride at least 350 miles a week, 90% of it straight down the interstate @ 70-75mph. I only attach the trunk when I am on a trip so there is about 30lbs less weight on the rear tire. I got 12-14K miles on the front & about 5-6K on the rear. Side tread on the rear still looks almost new . The question is, what effect would lowering the pressure a bit in the rear have on tire wear. I think I should get better wear out of the rear tire.

[bwringer]

Actually, you'll get less life with less pressure. You'll build up more heat and the tires will wear out much faster. It's true that lower pressure will make the contact patch a little bigger, but this has much less of an effect than increased flex and heat.

The Dunlop 404 is well-known to not last very long - you're doing well to get 5,000 miles. I got less than 4,000 miles out of a set of Dunlop 404s on my GS850.

For your usage, I'd recommend upgrading to a set of Dunlop 491 tires. They cost a bit more initally, but you'll get at least three times the life and still enjoy excellent grip. I got 12,000 miles on my set, and they easily could have made 15,000 except that I got impatient to try a set off Pirelli Sport Demons.

491s are marked with alphabetic sizes, so your GK would use MM90-19 front and MT90-16 rear (instead of 100/90-19 front and 130/90-16 rear).

[Suzuki mad]

I've had to up the tyre pressure's here to give a better rid on the road from all the poor surfaces we have here in the UK.

Transformed the ride, so I would not advise anyone to lower the pressures.

As for wear, I would suggest that it would mess the tyre walls up being soft and have adverse effect on handling from the rear tyre with less air.

Suzuki mad

1981 GS1000ET
1983 GS(X)1100ESD
2002 GSF1200K1

[Giblet]

Thanks for the replies. My apologies for the delayed acknowledgement. I've been running wide open for the last 3 days and have just now had time to sit down in front of the PC. I wasn't planning a drastic psi change. Just down to the lower recommendation the manual gives. At least I know I'm not nuts on the miles I got out of the rear. I was just expecting better wear on the rear since the front seemed to be wearing so well. I've gone back twice to check when I ordered the rear tire and add up the miles. I'll keep the 491 info in my shop manual. I do like the "very sticky" aspect of the D404's but it does irritate the CFO that I am buying a new rear tire after only 4 or 5 months. Like I said, I have a new set of 404's in the garage so the 491's will be next time around. I bought them through www.americanmototire.com . So, even if I only double my mileage I'm still money ahead.

DUNLOP K491 ELITEII MT90HB-16 RWL REAR - $104.92

DUNLOP D404 130/90HB-16 REAR - $56.64




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[chef1366]

I run with the tire manufacturer's highest pressure recommendation. You will get better gas milege, maximize tire life but your ride will suffer.

[denydog]

I run with the tire manufacturer's highest pressure recommendation.

Is that the maximum air pressure listed on the tire sidewall?

I've always understood that the max pressure printed on the sidewall is for when the tire is carrying it's maximum rated load. So it is essentially the safe upper pressure limit of that tire. Higher load and higher pressure could cause the tire to destruct. The tire manufacturer doesn't generally know what application (vehicle) and loads the tire will be subjected to, so they can't give recommended air pressures for normal, situational use.

That's for the vehicle manufacturers pressure recommendations, which vary depending on weight of the vehicle and passengers, and whether it's continuous high or low speed driving.

Normal solo riding, my manual specifies 24 psi front, 28 psi rear
I rode 440 miles today at 70 to 85 mph, manual specified 28 front 36 rear
Normal two up riding, 28 front, 36 rear
High speed two up, 32 front, 42 rear

The job of the air pressure is to maintain the tires proper shape, allowing some flex for proper contact patch shape, but limiting flex to control heat build up, and provide good handling. Different loads and speeds require different pressures to accomplish this.

I think the bottom line is that you want to control sidewall flex and subsequent heat buildup, but not eliminate it. There are negatives to an over inflated tire, and I'm not sure tire life is improved when over inflated.

In a way, it's like setting your suspension up. You could put the preload and dampng on full and ride around all the time that way. But it's usually thought to be better to match the suspension adjustments to your load and speed for instance.

I know there is much more that goes into all this but it all comes down to balancing the different parameters for the best results.

[Boondocks]

If a tire is inflated to no more than the maximum pressure rating on the sidewall, it is not overinflated. It may ride harder and be less comfortable than the manufacturer's suggested pressures, may not give quite as much traction under very hard cornering or in mud or sand due to a slightly smaller footprint, but will give better traction in rain, longer tire life and improved gas mileage.

Tire inflation pressure is a compromise, with no optimum psi for all occasions. Setting pressures to the higher end is more economical and generally safer. If pressures are not checked periodically, gradual air loss can result in underinflated tires. This is much more common than overinflation. Running tires with low pressure is very dangerous, and a recipe for tire failure due to overheating.

[chef1366]

If a tire is inflated to no more than the maximum pressure rating on the sidewall, it is not overinflated. It may ride harder and be less comfortable than the manufacturer's suggested pressures, may not give quite as much traction under very hard cornering or in mud or sand due to a slightly smaller footprint, but will give better traction in rain, longer tire life and improved gas mileage.

Tire inflation pressure is a compromise, with no optimum psi for all occasions. Setting pressures to the higher end is more economical and generally safer. If pressures are not checked periodically, gradual air loss can result in underinflated tires. This is much more common than overinflation. Running tires with low pressure is very dangerous, and a recipe for tire failure due to overheating.

Hey, that's what I was gonna say

[denydog]

If a tire is inflated to no more than the maximum pressure rating on the sidewall, it is not overinflated. It may ride harder and be less comfortable than the manufacturer's suggested pressures, may not give quite as much traction under very hard cornering or in mud or sand due to a slightly smaller footprint,

If it's riding too hard, and giving less traction, I consider that an indication that it is over inflated for the conditions (primarily load condition). When I say over inflated, I don't mean exceeding the manufacturers limit, I mean inflated more than optimal for the load and speed. More than optimum.

but will give better traction in rain, longer tire life and improved gas mileage.

I don't buy the better traction in rain, or the longer tire life. How can running the tire on a narrower contact patch lessen wear? It seems like it would accelerate wear down the centerline of the tire, by causing wear to be concentrated to a smaller area. My tires wear out from the tread wearing away down the middle of the tire. I haven't seen any of my tires wear out from excessive sidewall flexing heat build up. I'm not suggesting under inflating tires which can cause excessive heat build up, only to adjust the air pressure to load and speed, which is not the same for a lightly loaded bike driven at slow speed, as it is for a fully loaded bike driven fast. My previous post lists the Suzuki recommended tire pressure which I follow.

Tire inflation pressure is a compromise, with no optimum psi for all occasions.

That is exactly my point. If there is no optimum for all occasions, then why would someone recommend that high or maximum pressure is always best.

Setting pressures to the higher end is more economical and generally safer. If pressures are not checked periodically, gradual air loss can result in underinflated tires. This is much more common than overinflation. Running tires with low pressure is very dangerous, and a recipe for tire failure due to overheating.

Yes, under inflated tires can be unsafe and cause other problems, but that in no way means that pressure at the upper limit should always be used. It means people should check thier tire pressure regularly! The correct and safest pressure is the pressure needed to match the conditions.

The only argument I buy here, is that over inflated tires (and by over inflated, I don't mean over the tire manufacturers safe limit, I mean over inflated for the load and speed, which often is much less than maximum.) have less rolling resistance, and can save some gas. But think about it. A tire carrying maximum load, inflated to maximum pressure has little difference in rolling resistance than a lightly loaded tire with less air pressure, because they will have similar sidewall flex, which is entirely appropriate.

I guess we just don't agree about the value of running more than the vehicle manufacturers recommended tire pressure, guys.

[Boondocks]

If it's riding too hard, and giving less traction, I consider that an indication that it is over inflated for the conditions (primarily load condition). When I say over inflated, I don't mean exceeding the manufacturers limit, I mean inflated more than optimal for the load and speed. More than optimum.

You're welcome to create your own definition, as long as the rest of the world doesn't have to go along with it. See How Tires Work

I don't buy the better traction in rain, or the longer tire life. How can running the tire on a narrower contact patch lessen wear? It seems like it would accelerate wear down the centerline of the tire, by causing wear to be concentrated to a smaller area. My tires wear out from the tread wearing away down the middle of the tire. I haven't seen any of my tires wear out from excessive sidewall flexing heat build up. I'm not suggesting under inflating tires which can cause excessive heat build up, only to adjust the air pressure to load and speed, which is not the same for a lightly loaded bike driven at slow speed, as it is for a fully loaded bike driven fast. My previous post lists the Suzuki recommended tire pressure which I follow.

You don't have to buy it if you've made up your mind that you're always right. If you are interested in an expert opinion, see TIRE PRESSURES IN THE RAIN and Air Pressure vs. Wet Performance. Please explain to us why this is wrong.

Higher inflation pressures lessen tire flex at the contact patch. Continual flexing creates heat and eventually wears the center of the tread. For empirical evidence and an informed opinion on tire wear, see Common Motorcycle Tire Wear Patterns

That is exactly my point. If there is no optimum for all occasions, then why would someone recommend that high or maximum pressure is always best.

Excerpt quoted from the Pirelli Tire catalog:

TIRE PRESSURE
Always inflate tires to the correct tire pressure as indicated in the owner’s manual. However Pirelli US has found the air pressure suggestions listed below will improve mileage and customer satisfaction...

...Sport Touring 130/90 rear: solo 38-40 psi 2-up light 40-42 psi...

Yes, under inflated tires can be unsafe and cause other problems, but that in no way means that pressure at the upper limit should always be used. It means people should check thier tire pressure regularly! The correct and safest pressure is the pressure needed to match the conditions.

If improved mileage and customer satisfaction are not a concern, you're right again.

The only argument I buy here, is that over inflated tires (and by over inflated, I don't mean over the tire manufacturers safe limit, I mean over inflated for the load and speed, which often is much less than maximum.) have less rolling resistance, and can save some gas. But think about it. A tire carrying maximum load, inflated to maximum pressure has little difference in rolling resistance than a lightly loaded tire with less air pressure, because they will have similar sidewall flex, which is entirely appropriate.

I guess we just don't agree about the value of running more than the vehicle manufacturers recommended tire pressure, guys.

You are certainly entitled to your opinion, even if it is manifestly wrong and nobody else agrees with you.

[Jethro]

Holy sh!t, if I get more than 4000 mi out of my shoes I'm one happy camper. I would not complain with 5-6k on the granddaddy of 1100's...

[Steve]

Giblet,

I see that you already have your next set of tires bought (which is not always a good thing), but here is something else to consider. The Dunlop 491 Elite II is being phased out. Some distributors might still have some in stock, but insist on seeing the production date. If they are more than a year old, ask for fresher tires.

Something else to consider...The replacement for the Elite II is, of course, the Elite 3. I just wore out a set on my Wing. The previous owner put about 1500 miles on a set of E3s before I bought the bike. I managed to get another year and a half of use out of the tires. You could still see the tread when I replaced them, but it wasn't above the wear bars, at all.
Oh...total mileage? 23,000. \\/ Yes, I put on another set of E3s.

My previous bike was even heavier than the Wing, it was a Kawasaki Voyager 1300 (980 pounds, wet) 8-[ . I had the Elite IIs on that bike (2 sets) and got 18-20,000 miles on each set. Your GK is not as heavy, but mileage might be in the similar range.

We have a set of CS Hi-Max tires on my wife's 850. There is still tread on them, but not enough for our trip to Nebraska in August, so I am going to put E3s on the 850, now that they have expanded their line to include those sizes. \\/


.

[Giblet]

Holy sh!t, if I get more than 4000 mi out of my shoes I'm one happy camper. I would not complain with 5-6k on the granddaddy of 1100's...

Geeze! Didn't mean to stir up a stink but then I suppose it doesn't take much with this crowd. I was getting 7-8K on the various Chinese tires I was running (CS Hi-Max, Kenda 637). I was hoping to come closer to 10K on the rear with the 404's. But, this bike has been one long experiment & since it gets 35-40 mpg (vs the Sierra's 16-17) and only costs me $14/mo in insurance I'm still ending up spending way less getting myself to & from work. I'm just going to leave well enough alone with the air pressure since I am happy with the day to day handling & ride and look to move up to Elite III's or something comparable in 4 or 5 months. I just recieved this set of tires Thursday but I'm too busy to bother trying to return them so on they go this week sometime.

[denydog]

You are certainly entitled to your opinion, even if it is manifestly wrong and nobody else agrees with you.

I don't know that nobody else agrees with me. I didn't ask everyone:-D and I'm not taking your word for it.

Oh yeah, apparently Suzuki agrees with me, because it's their recommendations that I'm following. But ya, let's write them off, they only designed the motorcycle and specified the tires. Lets follow some obscure web links instead.

How Tires Work. Nice link! I wasn't trying to redefine overinflation. I was trying to explain to you what I meant by over inflation, as in over inflated per the vehicle manufacturers recommendation, but you missed it. Over inflated to the tire manufacturers maximum inflation pressure is not the same thing. Where did you get the impression that I was recommending under inflated tires anyway? I've been supporting the recommended inflation pressure as found in your manual for the most part. I just think it's generally wrong to pump em up to the max pressure on the sidewall. But if you like it, OK.

Nice try with the link anyway, but those car tire links did not address my points at all, so were pretty irrelevent. "Air Pressure vs Wet Performance" I already know for instance that under inflated tires will perform poorly in the rain. But I never suggested anyone should under inflated tires. I'm only suggesting adjusting the inflation pressure to the load (recommendations) rather than blindly using the tire's max pressure limit. Near the bottom of the page you linked, it states "Adjust your tire pressures as indicated on the vehicle tire placard or in the owner's manual." which is exactly what I've said. Thanks.

And a link to competition car, tire recommendations, for temporarily increasing pressure for racing in the rain? What is that about. Do you really expect me to add 6-10 lbs of pressure every time it rains?

And that link on wear patterns, recommending tire pressure for a Honda Valkyrie and VTX to reduce uneven wear and cupping. Like I'm going to just follow that. What, those bikes must weigh 700 lbs, and I don't even have uneven wear and cupping.

Maybe you didn't think I'd read your links? You need to work a little harder on your research. BTW- I can show you links that show that space people are living among us.

And I haven't seen the source, but Pirelli giving a blanket inflation recommendation for tires that may be used on motorcycles that can easily vary in bike and rider weight by 200 lbs or more? Sounds a little too much like "one size fits all". I try to be a little carefull believeing what I read, it may have come from the marketing department. :shock:

You don't have to buy it if you've made up your mind that you're always right.

I made up my mind I'm always right? Where did that come from. I'm only right this time! It's only an opinion, and it's better than always thinking I'm wrong! I'm not sure your issues are with tire pressure.

Oh, and for point of reference, saving a few bucks on gas and tire mileage are not my top priorities, ride and handling are. I'm going out to lower my tire pressures now, after having bumped them up for 500 miles of high speed riding I did this weekend. Load and speed my man. One size does not fit all.

[chef1366]

I run the tires with the highest pressure recommendation because I am 6'6" and weigh 300lbs. Plus my wife rides along alot. Plus I eat up tires and get bad gas milege (due to mods) but I drive aggressive.
NO FEUDING ALLOWED:-D