What do fat rear tires do for sportsbikes?

Question

You know how sometimes you see those guys on gsxr's that are extended and the rear tire is super fat, what does that do for the bike? other than looking cool of course, but does it make it more stable or something? im sure it would be harder to turn, but going straight i bet it sits easier...right?

Answer 1

It's really more for show, a wider tire does give you a bit more contact patch for traction for straight line speed.  And if you have a worked up Busa or ZX14 wheel spin can be an issue.

In fact NHRA pro stock motorcycles use an automotive drag race tire with a square cross section.   But you sacrifice cornering ability.   Of course when you have a lowerd, streched bike with a megaphone Vance and Hines pipe 3 inches off the ground anyway, you aren't worried about rolling corners.

Answer 2

90% just for looks, 10% increased traction for drag racing...

Answer 3

Fitting wider tyres on standard rims does nothing for the handling, although it does offer a slightly larger footprint it is at the expense of a deformed profile, in other words the tyre is not performing as the manufacturer intended and it is possible that the tyre will break its bead and come off the rim. Of course when fitting the extended swingarm you can fit a wider rim, but then you have the problem of aligning the drive without the chain sawing through the wall of the tyre.

Likewise an extended swingarm, essential for drag racing, increases the wheelbase, something which manufacturers have been trying to reduce for years on sportsbikes, to improve (speed up) the steering geometry, unless the suspension is altered to suit, including moving the mounts, won't improve stability in a straight line it will rather increase the tendency to squat under acceleration.

Answer 4

it offers more stability and better traction due to there being more surface area in contact with the pavement at all times.

Answer 5

Makes them harder to go around a curve. Engineers get paid big $ to figure out the best size tires for different bikes, the only thing you can do is make something about the bikes handling worse.

Answer 6

It seems to be an American thing you have a lot more long straight roads than we in Europe do. We have smaller twisty roads so prefer bikes to go round corners, so no long swing arms or extra fat tyres.

Answer 7

it makes it a lot more laid back to ride as it is easier to balance but it can also make it a lot more bumpier so those tires have their ups and downs.

Answer 8

They are for traction when drag racing, on the super street they use the long wheel base and big tire to get traction and hold the front end down .The longer the wheel base  the less likely you are to get into a wheel stand. Wheel stands slow you down. Sorry boys all of your rocket bikes pull the wheel a lot not because of the motor it helps but the short wheel base is a lot of it. The longer drag bikes do not corner well. Big wheels on something like big dogs is for looks only.

Answer 9

The only performance gain will be in straight line racing.  Longer swingarm = easier to keep the front end down, and the fatter tire = better traction.  But every other performance factor will decrease with the different geometry, as well as negatively effect the overall handling of the bike.  

Personally, I don't care for the looks of 'em that way.

Answer 10

they're seen on the drag bikes and the cruisers they ain't for maneuverability but make great for traction