Rabble-Rouser

Posted: Nov 22, 2007 02:34 AM  (Msg. 2 of 162)

Good luck in uncharted waters.............

Posted: Nov 22, 2007 07:37 AM  (Msg. 4 of 162)

Quote:


So you are saying that a non-directional tire would be better than a directional?  Many have been saying they only want directional.  A lot of the tread patterns I have seen look better in a non-directional.

Thanks  

"I'LL SHOOT ANYTHING FOR MONEY"

Posted: Nov 23, 2007 01:57 PM  (Msg. 6 of 162)

what aboutthis one.?>

http://store.coker.com/search.php?mode=search&by_title=Y&by_shortdescr=Y&by_fulldescr=Y&substring=155/80R15

Keep your eye on the road.

Posted: Nov 23, 2007 04:34 PM  (Msg. 8 of 162)

Quote:
It's a 155/80-15, and like I said, I don't want a tire that's smaller in diameter than the stock 170/80-15.  The 155 is an inch shorter than the 170.  That's over 100 rpm higher in 5th gear at 60 mph (+116 rpm for your bike in 4th at 60 mph).  Again, not a big deal, but not what I'm looking for.

Do I look like I'm in the mood for your s**t?

Posted: Nov 28, 2007 01:18 PM  (Msg. 10 of 162)

Hey DCon, not trying to pick a fight here, but wont a smaller OD on the rear tire actually give you more quickness off the line and more speed at the same RPMs and not necessarily more RPMs since a smaller rotating circumference will make more revolutions at the same speed as a larger one?

I only bring this up because I have some friends that used to race quads and they used to put smaller tires on the back for exactly those reasons.  Motor revs the same, but more revolutions are put to the ground for better whole-shots, better shots out of turns, and a bit more top-end on the straight-aways.

What Im getting at here, is that the tire size will effect the abilities of speed, or lack there of, but not necessarily the RPMs of the motor itself....I think.

Posted: Nov 28, 2007 02:18 PM  (Msg. 12 of 162)

DCon wrote: "It's hard for me to imagine that the new tire is going to plump up 30 mm or more in width and 9 mm in diameter, but we'll see."


From your measurements it only needs to plump up 25mm which is less than one inch to attain 175mm. Looking at your BF Goodrich picture of the mounted tire compared to your unmounted tire, it will easily do that.

Also over time I can see how the old tire may have expanded a little. 10mm is only 0.39 inches (0.195" per side). Also a softer tire pressure may cause a wider cross section measurement.

With air in the tire I think it will gain 9 mm in diameter. That's only 4.5 mm per end.

"I'LL SHOOT ANYTHING FOR MONEY"

Posted: Nov 28, 2007 02:27 PM  (Msg. 14 of 162)

The RPM's will be higher because the tire must turn more times to go the same distance.

Keep your eye on the road.

Posted: Nov 28, 2007 08:12 PM  (Msg. 16 of 162)

Quote:
I hope I don't have a reputation as a hothead.  I'm a nice guy!  I'm just a scientist nerd, so I get all picky about details and stuff.

Quote:
I'm going to concentrate my reply on just this part of your post.

Since I'm not changing anything in the transmission or the driveline, there is a fixed relationship between the motor and the back wheel.  That fact alone is what makes leaving the bike in gear when you have to park on a hill effective; the motor won't turn, so the back wheel will not rotate.

In stock trim, the motor turns a little over 11 times every time the rear wheel turns in 1st gear.  In 5th gear, it's a little over 3 and a half.  Therefore, for a given gear, more revs of the rear wheel has to mean more revs of the engine.  The DISTANCE that the bike travels for each rear tires revolution will not be the same for different sized tires; the smaller tire travels a shorter distance.  That means the bike will be going slower at any given engine rpm if the tire is made smaller.

Think of it this way: changing the diameter of the rear tire is kinda like changing gears.  Putting on a larger rear tire reduces the ratio between the engine revs and the rear tire revs (engine rpm/rear tire rpm), and is like shifting into a higher gear.  Putting on a smaller tire has the opposite effect and is like shifting into a lower gear.

Certainly, your friends get better hole shots with smaller tires.  Have you ever pulled away from a light in 2nd gear?

Posted: Nov 28, 2007 10:58 PM  (Msg. 18 of 162)

Quote:


I was comparing how the side walls on a mounted and inflated tire bulges out compared to an unmounted tire. Although, with a narrower rim than what the tire was normally intended for, you may not get as much bulge. On the other hand, just with your unmounted measurements, you already gained in height and contact surface, compared to the stock tire.

You may not want to gain too much more height or width, though. Looking at my bike, it looks like there is not much room on the left side of the stock tire, and the gain in width and height of your new tire is near the outer edge near the area where the swing arm is the narrowest up front. Or, is there something wrong with how my wheel is mounted with a lot more clearance from the right swing arm.  

Do I look like I'm in the mood for your s**t?

Posted: Nov 29, 2007 01:13 PM  (Msg. 20 of 162)

DCon, forget what I said.  Youre right and I know what happened....I thought about it too much.