Kawasaki Vulcan Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
I just purchased tires last year, and had a nail in the rear tire had it fixed and from then on i have been trying to figure out what is the correct tire pressure for both. They are Shinko 777 hd cruisers, 130/90-16 front with 49 psi COLD and rear 180/70-15 rear with 42 psi cold. With me and passenger a total of 330-350 lbs., and tubes in the tires, someone please tell me what i should be running. Everyone is a mechanic and of course know it all, and im not trusting. So i came here to ask others who would know. Hopefully someone can help me, because, Im really CONFUSED and i want to be safe and get the life of the tires. AND the rail says 28 psi front and 38 psi rear, NOW IM REALLY CONFUSED. HEEEEELLLLPPPP!!!!!!!!!!!!!! PLEASE!!!!!!!!!!!!!!!!!!!!!!!
Thank you to anyone who can help, ill check back tomorrow!!
 

·
Premium Member
Joined
·
1,214 Posts
The max cold pressure on the side of the tire is max pressure, cold, at the maximum load the tire is rated for. I have seen on some tire mfg pages that you should not run more than 6 - 7 psi below that max even if the load is light as a certain minimum pressure is needed to keep the tire shape correct and limit the flexing that would cause the tire to overheat.

Disclaimer - the following is my opinion:

I don't know about a 900, but Kawi says 28 psi for the front tire of the Voyager (same front tire size you listed). That is way too low, but it is a much heavier bike. Many people have had lots of issues with running (even the recommended Bridgestones) at that pressure, me included. Running a Bridgestone at that pressure ruined the tire. It developed a picture perfect wear pattern seen on tires that are under inflated, not to mention that it got scalding hot on the highway. The 900 is lighter than a Voyager, but I have also seen 900 owners comment that 28 psi is too low.

It's doubtful that you are anywhere near the max load on the front tire (that Shinko tire is a 73 load rate which is 805 lbs max on the front tire). I would back that off to 44-45 psi, maybe even a 42 - 43 psi.

That rear is an 82 load rate, which is 1047 lbs. Again, you are not going to be putting that much weight on the rear tire, but it does take more of the load, especially with a passenger, than the front. I would run it at 40 - 42 psi for 2 up and maybe a 1 - 2 psi lower for 1 up riding if you wanted to adjust it that way.

If you start seeing too much center wear, you are running too high. If you get excessive edge wear, the center is buckling due to low pressure. It may take a set of tires to figure out what is right for you.

Of course, you could do like some folks and just run at the max cold pressure. The worst that is likely to happen is that you will wear the center tread out really fast, although, if that is the case, you are probably not getting optimal traction either.
 

·
Premium Member
Joined
·
1,214 Posts
Oops! Just noticed that you said you have tubes. Honestly, I don't have a clue how to adjust motorcycle tire pressures for tires with tubes.
 

·
Registered
Joined
·
113 Posts
I read long time ago here on this forum 41 or 42 both front and rear.
 

·
Registered
2007 Kawasaki Vulcan 900 Classic LT
Joined
·
9 Posts
Running Michelin Commander II on Front and Rear. I went for the middle number and keep both at 40 psi

7k miles on my tires and they look good to me
 

·
Registered
2020 VN900 Classic LT
Joined
·
27 Posts
You mention PSI in your post, but not the weight. The weight part is important. As Sabre-t points out.. The pressure on the sidewall is the pressure you must to use if you're loading the tire to its maximum weight.

Your sidewall should say something like: "Max Load 520 Lbs at 42 PSI".

This means the most weight this tire can safely support is 520 Lbs and if you put that much weight on it, you have to inflate it to 42 PSI. If you have less weight, you don't need to use the maximum pressure.

As a very rough approximation, the Vulcan VN900 is about 650 Lbs and for a rough example I'll use a 50/50 front/rear weight distribution. That's 325 Lbs on the front tire and 325 lbs on the rear.

- 325 lbs is about 60% of the tires maximum load of 520 Lbs.

- 60% of the 42 lbs maximum air pressure is 25.5 lbs. That's pretty close to the recommended pressure on the bike.

In reality the pressure/percent forumula I used above isn't all that accurate. The PSI to weight ratio isn't linear. The example is another a rough approximation for demonstration purposes.

Tire manufacturers publish load & inflation tables. These tables show exactly how many PSI you need in a given tire for various weights. Unfortunately these tables are not made public and as a result, there is a lot of confusion on what tire pressure to use.

Car and bike manufacturers do have access to these tables. They use them to determine the recommended pressure that they put on the frame stickers.. If your tires are stock size, or close to it, just use the recommended pressures indicated on the bike.
 

·
Registered
Joined
·
529 Posts
Michelin once recommended 29 front and 33 rear for classic 900 and Commander IIs. I roll with those numbers.
 

·
Registered
Joined
·
125 Posts
ajddrumm - lot of opinions on what tire pressure use
kawasaki shows 32 psi as listed on the front down tube.
depends on your weight / load and how bike handles for you.
I found 35 to 38 psi in front tire makes steering feel lighter.
I have Shinko Tourmaster tires see my signature for details.
Tires brands make a big difference.
V900 tires need tubes - but my tires say “tubeless tire” OMG now what!!
tire manufacturers have their max weight and pressure listed - do not exceed those numbers.

Most important is tire age do not exceed 5 years on motorcycle tires - if you have questions on this ask Paul Walker.

tire pressures discussion in nothing ask which oil you should use!!!
 

·
Registered
2020 VN900 Classic LT
Joined
·
27 Posts
Just to expound on my long winded post above.. (With another long winded post).

Toyo Tires provides load inflation tables for car and truck tires. (Unfortunately not for motorcycle tires). You can Google for the PDF. (Just search for "Toyo Tires Load Inflation"). It's a large PDF file with LOTS of information to peruse.

I've cut out a bit of the table out of the document and included it below. It shows a list of tires and the proper pressures to use based on weight you want them to support.

Look at the P145/80R12 tire shown first on the list. Look to the right along the row. You'll see it goes to 816. That's 816 Lbs. Now look up in that column and you'll see 35. That's 35 PSI. This means the maximum weight the tire can support is 816 Lbs and if you want to put that much weight on the tire you need to have it inflated to 35 PSI.

On the sidewall of this tire, you would see: "Maximum Weight 816 Lbs @ 35 PSI".

Now if you look along the row to the left of the maximum weight, you'll see lower weights. To the left of the maximum weight, it says 783 Lbs. Looking up in that row it shows 32 PSI. This is the pressure you need to put in the tire in order to support 783 Lbs.

As the weights decrease, so does the required PSI needed to properly support the listed weight.

When a manufacturer chooses a tire for a vehicle, they don't pick a tire that can just support the weight of the vehicle and no more. In the interest of safety, the choose tires that can support more than the vehicle's curb weight.

The de-rating of the PSI as the weight gets lighter than the maximum weight is why the frame or door sticker of a vehicle showing the recommended PSI will ALWAYS be less than the maximum weight and PSI shown on the tire sidewall.

241245
 

·
Premium Member
Joined
·
1,214 Posts
Motorcycle tires do not list a max weight on the sidewall. In the US they are required to use a number that represents the weight rating. As I noted in my earlier post, the tubeless tires that the OP listed the 73 for the front tire indicates a max load of 805 lbs and the rear number of 82 indicates a max load of 1047 lbs.

I'm not sure, but the table jwt873 looks like an auto tire table, not a motorcycle table.
 

·
Registered
2020 VN900 Classic LT
Joined
·
27 Posts
I did indicate that the table was for car tires.. (I wish I could find one for bikes). But they are similar. There's a maximum pressure that is reduced as the weight the tire has to carry is reduced. Also note that in the table they express tire capacity by load index number also.

On showing the Lbs/PSI on the sidewalls.. Some motorcycle tires do... In another tire pressure thread on this forum the poster attached a picture of the max weight/psi on the sidewall of his tire.. Tire Pressure Question - Which One is Right? / Preload Adjustment Question

I haven't looked at my tires yet.. The bike is still at the dealership :( I bought it last month, but couldn't ride it home because there was still too much snow.

It's a new bike.. I picked up the title papers yesterday. Going to get the plates later.. Then hopefully It'll be in my garage by Monday.
 

·
Premium Member
Joined
·
1,214 Posts
I did indicate that the table was for car tires.. (I wish I could find one for bikes). But they are similar. There's a maximum pressure that is reduced as the weight the tire has to carry is reduced. Also note that in the table they express tire capacity by load index number also.

On showing the Lbs/PSI on the sidewalls.. Some motorcycle tires do... In another tire pressure thread on this forum the poster attached a picture of the max weight/psi on the sidewall of his tire.. Tire Pressure Question - Which One is Right? / Preload Adjustment Question

I haven't looked at my tires yet.. The bike is still at the dealership :( I bought it last month, but couldn't ride it home because there was still too much snow.

It's a new bike.. I picked up the title papers yesterday. Going to get the plates later.. Then hopefully It'll be in my garage by Monday.
Not sure why you can't find a chart for motorcycles. I did a google search for "motorcycle tire load chart" and the first 5 items up all had the chart. Here's one: MC Tire Load Chart.

There is very little guidance on how to reduce the pressure based on lower than max loads. The primary source is each MC owners manual. They usually say something like "up to (some number) lbs of cargo, use (some number) psi. From (the previous load weight + 1) to (max load the bike is rated for) use (a higher number) psi." This usually is only for the rear tire. The front tire's pressure is not usually changed due to load changes.
 

·
Registered
2020 VN900 Classic LT
Joined
·
27 Posts
Not sure why you can't find a chart for motorcycles. I did a google search for "motorcycle tire load chart" and the first 5 items up all had the chart. Here's one: MC Tire Load Chart.

There is very little guidance on how to reduce the pressure based on lower than max loads. The primary source is each MC owners manual.
That chart shows only the load index ratings and corresponding weight rating.

Tire manufacturers also compile load inflation tables.. (Like the one I included in my post above). These inflation tables show the maximum weight/PSI and the recommended inflation pressures for lighter loads. That's what I'd like to find for bikes. The one from Toyo tires and a few outfits that sell trailer/RV tires are the only ones I've managed to uncover.

Of course, the whole point of my two long winded posts above was just to show the OP that you don't need to inflate a tire to the max pressure shown on the sidewall (if it should be displayed there) .
 

·
Registered
Joined
·
255 Posts
I agree with Les on this one.
Manufacturers test their bikes and supply the pressure rating on the bike. Cars are the same. Most tire mfg. tell you to follow vehicle recommendations.
In reality, brands of tires are different, and each person and their gear has a different weight. So it's possible that you may need to vary slightly.

Use some common sense. I personally tried some higher rates others here recommended and my bike was so squirrelly I couldn't wait to get home and put the recommended PSI .
 

·
Premium Member
Joined
·
1,214 Posts
Using the bike manual recommendations works ONLY if you use the tires recommended (or the way they word it in some manuals, required). A heavy duty tire needs a different pressure than a "regular" duty tire. Tires with different profiles need different pressures.

And, as I mentioned earlier, my and others experience with the Kawi recommended front tire pressure, even on the tire Kawi recommends, is very questionable. For the Voyager, 28 psi in the recommended Bridgestone just does not work.

Slavishly following manufacture recommendations in the face of evidence that they are questionable, just does not make sense, to me. For example, the Ford Explorer/Firestone tire fiasco. Ford ignored Firestone's PSI specs and went with a lower pressure to increase stability, but that backfired as the tires overheated and came apart. Ford claims that the tires should have been spec'd at a lower load limit, but inflating them to Firestone's specs solved the tire problem, though it only made the Explorer instability worse. Following Ford's vehicle recommendations cost many lives.
 

·
Registered
Joined
·
37 Posts
I just purchased tires last year, and had a nail in the rear tire had it fixed and from then on i have been trying to figure out what is the correct tire pressure for both. They are Shinko 777 hd cruisers, 130/90-16 front with 49 psi COLD and rear 180/70-15 rear with 42 psi cold. With me and passenger a total of 330-350 lbs., and tubes in the tires, someone please tell me what i should be running. Everyone is a mechanic and of course know it all, and im not trusting. So i came here to ask others who would know. Hopefully someone can help me, because, Im really CONFUSED and i want to be safe and get the life of the tires. AND the rail says 28 psi front and 38 psi rear, NOW IM REALLY CONFUSED. HEEEEELLLLPPPP!!!!!!!!!!!!!! PLEASE!!!!!!!!!!!!!!!!!!!!!!!
Thank you to anyone who can help, ill check back tomorrow!!
You are on 2 wheels and one has been compromised. Me personally, wouldnt fix the hole, i would get a new tire. Wouldnt take the chance of a plug holding.
 

·
Registered
Joined
·
273 Posts
You are on 2 wheels and one has been compromised. Me personally, wouldnt fix the hole, i would get a new tire. Wouldnt take the chance of a plug holding.
If the tire has been repaired properly, there shouldn't be a problem. No where did he say it was plugged, people do patch tires also.
 
1 - 20 of 23 Posts
Top