Front Tire Skinny vs Fat tire

[Mark_M]

I was reading some reviews on the Kawasaki Vulcan 900 custon and the classic and the author states in there that the skinny tire has a drawback

I quote from motorcycle daily by authur Alex Edge

"The chassis is slightly different from that of the 900 Classic, with an additional degree of rake (33 degrees versus 32). The 900 Custom also features enhanced braking power, with a single 11.8" (300mm) front disc squeezed by a twin-piston caliper, while a 10.6" (270mm) disc is slowed by another twin-piston caliper out back. The bigger rear brake is important, since you won't be able to put much braking force through that skinny front tire."

I request info from you guru's in the forum to respond with your personal experiances, is it really a very big difference a skinny to a fat front wheel?
I really love the look of the Vulcan Custom but the above review made me rethink my choice.

[StarWatcher]

Since 80+ percent of braking power is done with the front brakes I'm not sure I understand his stated reasoning for the larger rear brakes. Since you and the either of the two bikes are about the same weight the biggest effect on braking should be the size of the contact patch on the front wheel and the characteristics of the tire. Will your dealer let you drive or at least put them to a parking lot comparison test before you buy?

--Mike

[flb_78]

Skinny tire, Fat tire, doesn't matter in braking. The difference will be in handling, Skinny tire will turn in faster, Fat tire will be harder to turn, but, Skinny tire will also follow road cracks a lot easier then fat tire.

I dont agree that 80% of your braking is in the front. A cruiser has a lot of weight in the back. My Venture slows mucho faster while applying the rear brake with the front brake then the front brake alone and the Venture has twin discs up front.

[Plane Dr]

Several things here. Cruiser, means no weight transfer to the front for braking. Especially with the exagerated rake. So the front wheel is pretty useless compared to other designs. Second small contact patch on the skinny tire so less friction area, less brake force.

Also the skinny cruiser tire is designed to have that nice round profile even further reducing contact patch.

The chasis geometry will affect the handling as well. However wider wheels have more rotating mass farther from the center of rotation (proportionally) so will tend to turn slower (or actually resist turning more strongly).

Personally, they are messed up and contrary to what a motorcycle is. But hey if a rolling blingy lawn chair is your thing. More power to ya!

[Harri 650 Fan]

Every bike, no matter what type or how long or how tall, shifts weight to the front wheel when braking. It's a matter of physics. That is why your front suspension compresses during braking. See the attached from Proficient Motorcycling by David Hough. If you aren't familiar with this guy, he is just incredible. His books are fantastic.

[Mark_M]

This is the bike Kawasaki Vulcan 900 custom that has the skinny 21 inch tire.
I guess I will have to get a test ride some how to determine the riding and hanling differences between the custom and classic [fat tire].

[dukey33]

Skinny or wide won't make that much difference in contact patch while braking (for street riding conditions). The load transfer onto the front tire will make it flatten out and increase the contact patch. Holding all else equal, the skinny tire will deflect more since it holds less air volume and thus has less load capacity. The fat tire holds more air and will deflect less. Without doing actual footprint tests, one might guess it all equals out.

Bottom line, if you like the look of the custom, get it. Cruisers are mostly about looks anyways. That's why I like them. You'll never have to "explain" that bike to anyone, rider or non-rider.

[Plane Dr]

Okay gents some interesting information not entirely accurate...

Weight transfer yes every bike has it. Now then. Since the brakes are the starting point let's start there. Just for simplicity sake lets assume both bikes generate the same braking force (patently false but lets use it anyway). The c of g of the sport bike will higher than that of the typical cruiser, though the actual mass will be less so again lets go with an equal moment/arm above the front axle. Now finally given that the distance from the c of g of the bike is different cruiser being long (front wheel way out there) sport bike being short (front wheel tucked in) the moment reacted due to the short arm to the front wheel is higher on the sport bike than the cruiser. Therefore it has to generate more "weight transfer". Also we have neglected the different dynamics of the suspension design. So given we neglected the better brakes, better rubber, suspension and the higher c of g, I stand by my earlier statements.

Second, air is very compressible. The more volume the easier to compress since you have less net change per volume. Therefore a fat tire with lots of air compresses more. But that argument is bubkus since the stiffness of the tire and sidewalls is the determinant.

Flat out if you want fashion go with fashion. Function is not for everyone nor when solely considered is it often flattering.

[StarWatcher]

A handy calculator concerning weight transfer during maximal braking can be found here in this thread:

http://www.msgroup.org/forums/mtt/to...erms=model,xls

In the image below I've plugged the numbers from the Kawasaki site for the Vulcan into the calculator. I've also modified it to add a section at the bottom showing the amount weight transferred to the front wheel assuming the the formula:

Weight Transfer = Total Weight * Deceleration Rate * Center of Gravity / Wheelbase

where Total Weight = the bike and a 200 lb. rider.

If you want to play with it, this calculator can be downloaded ( minus my changes ) in the thread mentioned above.

[dans_stratus]

I think everone is over analizing what is a very small difference in two bikes that are virtually the same. I own an 08' 900 kustom and my freind own the 07' 900 classic. I have ridden both and while I'll admit to some minor difference in steering and road vibration due to the different tire size, I notice no signifigant difference in braking. Bottom line is buy the one that looks best to you.



DAN_STRATUS