150-70 rear tire?

[Yammy]

Has anyone tried this? By my calculation and I may be wrong. It would increase rpm's by 344 @ 60 mph, calculated. The rear would be 1.18 inches lower but a leveling kit raises about an inch so it would be about the same and help 5th gear?

[SilvrT]

....and what's wrong with 5th gear that it needs help???

[Yammy]

....and what's wrong with 5th gear that it needs help???

 

The few extra rpm's may help prevent the lugging especially when pulling a trailer. Might be cheaper than the rear end swap?

[Sylvester]

I don't think so. Yes you increase the rpm in 5th, but fourth will do the same. I have driven my RSMV at 75-80 mph and never shift out of 4th, and never see a decrease in mpg. All I can see is a decrease in handling with the smaller tire. The leveling links were installed to improve the handling, not support a smaller tire.

 

[SilvrT]

The few extra rpm's may help prevent the lugging especially when pulling a trailer. Might be cheaper than the rear end swap?

 

I suppose ... at what speed were you lugging? Why not just drop down to 4th ... that's what I do ... take it up to about 110 km/h (appx 68 mph) and then upshift to 5th ... won't be lugging then.

[V7Goose]

Has anyone tried this? By my calculation and I may be wrong. It would increase rpm's by 344 @ 60 mph, calculated. The rear would be 1.18 inches lower but a leveling kit raises about an inch so it would be about the same and help 5th gear?

I'm not buying your calculations, Laddie.

 

First, you do not specify what specific tires you are comparing (they are NOT all the same size), so I cannot specifically check your math. But for the most part, there is very little difference in the diameter between 150/90-15 and 170/80-15 tires.

CLARIFICATION EDIT: Note here that I was comparing stock 150/90-15 tires with the most common alternate size 170/80-15. When I first read Yammy original post, my brain completely glossed over the fact that he was actually asking about a 150/70-15 tire (which I do not think actually exists, at least not from Avon, Dunlop or Metzeler). All of my comments remain valid, but my apologies to Yammy for not noting this before. A 150/70-15 tire would probably be about two inches less diameter than the stock tire, just like he calculated, but that is just a guess - like with any tire, you would still need to look at the manufacturer specs to know for sure.

 

For example, the Avon Venom 150/90-15 has a diameter of 25.4", and their 170/80-15 is actually 1/2 inch TALLER at 25.9". This means the rear of the bike would actually be raised by 1/4". The same sizes in the Dunlop D404 have diameters of 25.6" and 25.43" respectively, for an even smaller difference.

 

I am going to look at a 170/80-15 rear tire when I need the next one, but I am much more concerned about the side clearance before I make up my mind.

Edited October 13, 2010 by V7Goose
clarification

[BuddyRich]

I was looking at the Pirelli's for my next rear in a 170/80 15.

 

http://www.jakewilson.com/productDetail.do?navTitle=Motorcycle+Tires&webCatId=57&navType=type&webTypeId=447&prodFamilyId=19469&listingId=&sizeAttr=5321

[SilvrT]

 

I am going to look at a 170/80-15 rear tire when I need the next one, but I am much more concerned about the side clearance before I make up my mind.

 

Get ahold of our member "Pecker" as he runs that size.

[Yammy]

I don't think so. Yes you increase the rpm in 5th, but fourth will do the same. I have driven my RSMV at 75-80 mph and never shift out of 4th, and never see a decrease in mpg. All I can see is a decrease in handling with the smaller tire. The leveling links were installed to improve the handling, not support a smaller tire.

 

 

Love this site, all angles are covered.

Your right, I stand corrected, I never thought of the other gears. I did run an 150-80-15, don't remember the make. Got a flat and that's all they had. I did notice more giddy up.

[Yammy]

I'm not buying your calculations, Laddie.

 

First, you do not specify what specific tires you are comparing (they are NOT all the same size), so I cannot specifically check your math. But for the most part, there is very little difference in the diameter between 150/90-15 and 170/80-15 tires.

 

For example, the Avon Venom 150/90-15 has a diameter of 25.4", and their 170/80-15 is actually 1/2 inch TALLER at 25.9". This means the rear of the bike would actually be raised by 1/4". The same sizes in the Dunlop D404 have diameters of 25.6" and 25.43" respectively, for an even smaller difference.

 

I am going to look at a 170/80-15 rear tire when I need the next one, but I am much more concerned about the side clearance before I make up my mind.

 

I may be wrong here too but it's my understanding on a 150 width tire the 90 and 70 are percentages of the width so with a 15 inch rim a 150-90

 

150/25.4*.90= 5.3 inches *2+15= 25.6 inches vs 23.2 inches on a 70, same make and width tire say metzler

 

converted to rpm 3305 and 3641 approximate. I used 4.2 as gear ratio.

[V7Goose]

I may be wrong here too but it's my understanding on a 150 width tire the 90 and 70 are percentages of the width so with a 15 inch rim a 150-90

 

150/25.4*.90= 5.3 inches *2+15= 25.6 inches vs 23.2 inches on a 70, same make and width tire say metzler

 

converted to rpm 3305 and 3641 approximate. I used 4.2 as gear ratio.

If you want to know the actual width and diameter of a tire, you need to check with the manufacturer - each one is unique. That is why I provided the actual published specs for several tires. As I said before, any one particular brand in 150/90-15 is NOT the same actual size as any other particular brand in the same "size".

 

I have found tires of the same size (as stamped on the sidewall) that varied by as much as a full inch in actual measured width between brands and tire series. The same is true with diameter.

Goose

[SilvrT]

The following comes from TireRack.com

 

NOTE: what I highlited in red below .... this suggests that if the rim size is the same then all tires having a "225" section width should be the same distance across. That being said, then they should all be the same height @ say 50 as in the example below. -SilvrT

 

Section Width

 

Following the letter(s) that identify the type of vehicle and/or type of service for which the tire was designed, the three-digit numeric portion identifies the tire's "Section Width" (cross section) in millimeters.

P

225

/50R16 91S

The

225

indicates this tire is 225 millimeters across from the widest point of its outer sidewall to the widest point of its inner sidewall

when mounted and measured on a specified width wheel

. This measurement is also referred to as the tire's section width. Because many people think of measurements in inches, the 225mm can be converted to inches by dividing the section width in millimeters by 25.4 (the number of millimeters per inch).

225mm / 25.4 =

8.86"

Sidewall Aspect Ratio

 

Typically following the three digits identifying the tire's Section Width in millimeters is a two-digit number that identifies the tire's profile or aspect ratio.

P225/

50

R16 91S

The

50

indicates that this tire size's sidewall height (from rim to tread) is 50% of its section width. The measurement is the tire's section height, and also referred to as the tire's series, profile or aspect ratio. The higher the number, the taller the sidewall; the lower the number, the lower the sidewall. We know that this tire size's section width is 225mm and that its section height is 50% of 225mm. By converting the 225mm to inches (225 / 25.4 = 8.86") and multiplying it by 50% (.

50

) we confirm that this tire size results in a tire section height of 4.43". If this tire were a P225/

70

R16 size, our calculation would confirm that the size would result in a section height of 6.20", approximately a 1.8-inch taller sidewall.

 

Just thought I'd throw this into the "pot". Someone with some time might want to got to different tire mfg's websites using a specific tire size and see what each mfg lists as actual width and height for that tire. It's an interesting subject - SilvrT

[V7Goose]

You guys can speculate all you want on what the numbers are supposed to mean. I think research is good, as is trying to understand the intent behind something.

 

But the facts are thus: two tires with the same number on the sidewall rarely measure the same unless they are the same brand and model. Sometimes the difference is small, sometimes it is large. I have physically done the measurements to prove this, but even that is besides the point. Just look it up in the manufacturer's documentation.

 

If Avon says their 150/90-15 tire is 6.3" wide and 25.4" in diameter while Dunlop says their 150/90-15 is 6.05" wide and 25.6" in diameter, you are pretty much going to have to accept that they are different sizes.

Goose

 

BTW - if you want to quickly see just how inaccurate that TireRack.com explanation can be if taken literally, just take a quick look down the tire width column for any brand of tire. I just did this for the Avon Venoms, focusing only on tires that have a nominal section width of 150 (such as the 150/90-15). Those tires, ALL Avon Venoms in various 150 sizes, range in width from 148mm through 159mm.

 

The reason this is so is that tire sizes are called "NOMINAL" sizes, which means roughly that the size is an approximation, or something close to the actual measured size.

Edited October 13, 2010 by V7Goose

[Brake Pad]

I run the 180 on the back, But I must baby my bike cause, I shift into 5th at around 55-60

but on the other hand, I've run the bike down to 45 mph in 5th 2 up pulling the trailer

[SilvrT]

The reason this is so is that tire sizes are called "NOMINAL" sizes, which means roughly that the size is an approximation, or something close to the actual measured size.

 

I agree with you ... was just posting what the sizes are supposed to mean according to the original "idea" (if I can use that). My statement used the words "suggests" and "should be" .... I wasn't necessarilly supporting the quotes.

 

I run the 180 on the back, But I must baby my bike cause, I shift into 5th at around 55-60

but on the other hand, I've run the bike down to 45 mph in 5th 2 up pulling the trailer

 

You have a 180 on the rear??? I (if not others) would like to know more about that!

How does the bike handle?

What effect has it had on your rpm vs speed in, let's say 4th & 5th?

What clearance mods did you have to make?

Anything else you can say about it...

[V7Goose]

I just put the following clarification in my first reply to this thread, but because it involves an apology to Yammy, I wanted to put it in a new reply also to make sure that he and others see it:

 

CLARIFICATION EDIT: Note here that I was comparing stock 150/90-15 tires with the most common alternate size 170/80-15. When I first read Yammy original post, my brain completely glossed over the fact that he was actually asking about a 150/70-15 tire (a size which I do not think actually exists, at least not from Avon, Dunlop or Metzeler). All of my comments remain valid, but my apologies to Yammy for not noting this before. A 150/70-15 tire would probably be about two inches less diameter than the stock tire, just like he calculated, but that is just a guess - like with any tire, you would still need to look at the manufacturer specs to know for sure.

 

Goose

[Yammy]

I just put the following clarification in my first reply to this thread, but because it involves an apology to Yammy, I wanted to put it in a new reply also to make sure that he and others see it:

 

CLARIFICATION EDIT: Note here that I was comparing stock 150/90-15 tires with the most common alternate size 170/80-15. When I first read Yammy original post, my brain completely glossed over the fact that he was actually asking about a 150/70-15 tire (a size which I do not think actually exists, at least not from Avon, Dunlop or Metzeler). All of my comments remain valid, but my apologies to Yammy for not noting this before. A 150/70-15 tire would probably be about two inches less diameter than the stock tire, just like he calculated, but that is just a guess - like with any tire, you would still need to look at the manufacturer specs to know for sure.

 

Goose

 

No apology needed. I was just looking for alternatives to a rear end swap. I suppose a rear end swap also effects each gear as well by a set rpm change. I'll bet it'll launch with a 150-70-15. Do both and you'd need a wheelie bar.

I believe some with the vmax were using a 180 rear. Just had to do a washer swap. Don't know if it would work on the rstd.