How many RPMs with stock rear diff?

[KJShover]

I do not understand how the rear wheel tire size or rim size affects the speedometer if the front tire size is the same as stock.

Your right, It wouldn't change a thing with the stock diameter front.

The diameter of the rear tire effects the engine RPM at speed. eg. say cruising at 4500 rpm with the stock tire diameter nets you a certain speed. The R's would be higher with a 17" wheel and a lower profile tire and lower with an 18" rear wheel. But unless the front wheel's diameter is stock it won't change a thing in the speedo's reading. if the front wheel's diameter is higher or lower, the speedo would read slower and faster respectively.

A popular mod is to use a different hub from a Venture. This will change the rear gear ratio and thus lower the RPMs and increase your bikes range. With a Venture hub swap, the 5th gear overdrive, and an 18" rear rim, the Vmax just might just pass as a distance bike :biglaugh:


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[[email protected]]

I do not understand how the rear wheel tire size or rim size affects the speedometer if the front tire size is the same as stock. (I know there is always some error in motorcycle speedometers). When I was in grade school, we had to measure the school yard with a wheel that was one yard in circumference and had a clicker on it. You only had to count the clicks to know the distance covered. It would not matter how fast you walked or ran, the distance would be the same. Why is that principal changing on a motorcycle if the speedometer cable is connected to a stock size front tire? Thanks.

The rear wheel doesn't change your speed reading but it will effect what rpm the engine is running at a certain speed.

100 mph is 100 mph. But, if you have a 10" tall rear tire the engine would be turining way more rpm than if the rear tire was 30" tall.

If your measuring wheel in school was the size of a lawnmower wheel it would turn many more times than a measuring wheel that was the size of a tractor wheel. But if they are both calibrated correctly you get the same length measurment

 

[Redbone]

With the overdrive fifth Approx:

60mph = 3000
70mph = 3500
80mph = 4000
90mph = 4500

Maybe one of my customers on here can verify what they are getting and the tire sizes being run.
My numbers match those while running the stock wheels w/ 170/ xx 15 rear and a 110/90 18 front. I run the RS 5th with my current setup.

Rear Diff Ratios:
Venture is a 10% reduction (3.66 vmax rear ratio vs 3.33 venture rear ratio)

Overdrive/Stock Fifth gear ratios
Vmax 26/28 = .928
RS Overdrive 21/28 = .750

Not sure if the excell sheet attaced correctly and it's been a long time since I verified that the calculations put in there are correct.

Sean

It is a very worthwhile mod if you do a lot of LD riding.

 

[El Canadiense]

You are all right in that the taller, not wider tires or Venture diff will just lower your RPMs at a specific speed which in turn gives you better mileage and more miles out of the small VMax tank. My VMax seems to be revving pretty high for the speed at which shows on the speedometer. I guess I will get someone to follow me in a car and let me know what speeds I am actually travelling. Thanks to everyone for their quick responses.

 

[Rollie]

Running a Venture diff. with Michelin Pilot Powers in the 17" flavors :

3500 rpm = 60 mph

4000 " = 70 "

4500 " = 80 "

5500 " = 100 "

I can't tell any seat of the pants difference in accelaration drop off either from the stock punkin' . unk: Aftermarket cams , Stage 7 , Kerker 4 - 1 .

 

[El Canadiense]

Has anyone heard about different ring and pinion gears being available? Was thinking that maybe another ring & pinion may be made to use on another vehicle that will fit into the VMax. Or maybe even a ring/pinion supplier? Any information would be appreciated.

 

[khm28043]

Great Thread! I have always wondered why my rpm's were so high at cruising speeds. I found out that my stock speedo was about 5 mph at 55.

The other day when I thought I was going 90, the man with the blue lights informed me I was going 100... Thank God he was a fan of the V-max. After a few minutes of nervous conversation about the bike he told me to slow down and go have fun at a lower speed.

 

[Biker Dash]

Has anyone heard about different ring and pinion gears being available? Was thinking that maybe another ring & pinion may be made to use on another vehicle that will fit into the VMax. Or maybe even a ring/pinion supplier? Any information would be appreciated.

See all the talk about the Venture hub? That's exactly what you're looking for it sounds.

Myself, I think I would rather go with the Overdrive gear in the tranny. That way, I still have the acceleration in the lower gears, but can cruise longer distances in 5th. (once I leave town, anyways lol)

 

[Miles Long]

You are all right in that the taller, not wider tires or Venture diff will just lower your RPMs at a specific speed which in turn gives you better mileage and more miles out of the small VMax tank. My VMax seems to be revving pretty high for the speed at which shows on the speedometer. I guess I will get someone to follow me in a car and let me know what speeds I am actually travelling. Thanks to everyone for their quick responses.

On a recent tour, I had ample opportunity to see the changes that a venture final drive (it's NOT a differential!) makes, when traveling in 5th gear at constant speed(s)
- an average of 35 kilometers more per full tank (15 liter main, plus 5 liter aux.) of gas, before fuel warning light. In my case, this meant I could go 295-305 kilometers (180 miles), before reserve.
- contrary to what others have found, best mileage was obtained while riding on secondary roads, at a constant 85-95 kph (around 3k rpm). The engine, exhaust and carburation is completely stock. Set up and loaded for touring, however, the bike is about 150 pounds heavier than stock.
- at highway speeds (100-120 kph, 36k-40k rpm) vibration at the handle bars and pegs is noticeably reduced, mirror image stay clear, unlike running with stock FINAL DRIVE.
On another topic, previously while running a well-used front tire (stock sized Metzler 880), I noticed the speedometer was a tad optimistic (by about 5 kph), when compared to indicated GPS speeds. With a new tire of the same brand and size, the speedo is almost spot on, at cruising speeds (90-100-120, etc). The larger radius of a new tire must be just enough to make the difference.
Everything being said, the Venture drive mod is a very useful one, if doing a lot of highway riding.
Cheers!

 

[josephjhaney]

I am tempted to look into this mod, but I really like the off the line acceleration the Vmax has as well, as a genera question, how much is that tempered by the mod?

 

[Bruiser1198]

I am tempted to look into this mod, but I really like the off the line acceleration the Vmax has as well, as a genera question, how much is that tempered by the mod?

I had a 17" rear wheel with a 180/55-17 and had the Venture rear end and low end acceleration did not suffer at all , the gearing was just enough of a change as not to spin the rear tire as much and hook up better , my bike was a 96 with stage 7 Kerker 4/2/1 exhaust and Nitrous . I did keep the stock rear end also but with the 17" wheel it just spun the tire like crazy and to give you an idea I am not small at 6'3" 320lbs. Just my .2 cents , Later VMOA #953 Kurt

 

[[email protected]]

I say it all depends on your riding style.

If you are into long rides or just cruising, the venture drive is great.

If you like to hammer on the bike from corner to corner the venture drive removes a lot of the excitement.

I am running 17" wheels front/back. I recently installed a venture final drive (that ones for you miles :biglaugh and during the first test ride I though something was wrong with the bike for a minute. Then I realized, it was not feeling sluggish because of an issue, it was because of the venture drive.

It didn't take long to get used to it. Its kind of nice to have if you are cruising along the highway or going for a leisurely ride. But, if you want to be in hooligan mode it takes some of the fun out of it.

 

[Redbone]

Unless you add a bunch of HP in front of the Venture final drive you're going to end up with a little slower but with little better fuel mileage Vmax.
I liked the Royal Star 5th gear mod when I had it in Redbone but still when your letting your inner hooligan out 5th gear is kinda a dog. Gears 1-4 are still fun though!

 

[one2dmax]

.3 tenths of a second at the track (about 6 bike lengths which is a ton). Also, less spunk so not as easy to get that front wheel up (especially when the longer rear swingarm).

Sean

 

[Bruiser1198]

I never had a problem with mine but then again I launched at about 6,000 rpm so maybe that's why I was happy with it.

 

[Hellboy]

I just took my bike out with a GPS and found that in 5th at 3000 RPM it does 48MPH and at 4000 RPM it does 64MPH. The speedo is 1 or 2 MPH off, better than I expected. That is stock size tires and diff.