Hey guys this is my first post, although I've been accessing this website almost daily since I got my 2006 GS about a year and 7000 miles ago.  Good job everyone, all the different posts on the message board have been really helpful in getting to know my GS. 

So I picked up a nail a while back in my rear tire and temporarily rode around with a plug in it.  I finally decided to get a new tire, so based on the recommendations of everyone on the board I went with the Perelli Sport Demon.  I wanted something a bit wider and also wanted to get a little better gas mileage for my 30 mile one way commute to work at 65mph posted speeds so I got a slightly taller tire.  The size I went with was a 140/80 and I decided that this is the largest Sport Demon that will fit on this bike.  I had heard that a taller tire lowered your gearing but I never saw any actual numbers so I'm posting my before and after numbers to give some ideas on how much the gearing really changes. 

Note: the before is with the stock BT-45's size 130/70 rear tire and I have not changed the front tire so it's still the stock 110/70 BT-45.

6th Gear Before
4,000RPM's     49MPH
5,000RPM's     61MPH
6,000RPM's     74MPH
7,000RPM's     86MPH

6th Gear After
4,000RPM's     52MPH
5,000RPM's     65MPH
6,000RPM's     79MPH
7,000RPM's     93MPH (This was for the sake of testing so please don't yell at me )

5th Gear Before
4,000RPM's     42MPH
5,000RPM's     53MPH
6,000RPM's     65MPH
7,000RPM's     77MPH

5th Gear After
4,000RPM's     46MPH
5,000RPM's     58MPH
6,000RPM's     70MPH
7,000RPM's     82MPH

I love the new tire!  When I finished installing it this morning I took a thirty mile ride to test it out and all the good stuff people say about Perelli's is true.  With the wider tire the bike feels much more stable but is still very flickable.  The bike sits about a half an inch taller and I don't notice any steeper turning that I thought I might experience by having a tall rear tire with a shorter front tire.  There's about a quarter of an inch gap between the side of the tire and the angled bar that holds the rear brake in place.  I'll try to post a picture with the tire mounted on my bike.  Keep up the good work!
Matt

If you want to lower those numbers some more, you can put a 17 Tooth sprocket on the front...  Commuting machine!

How wide a tire did you use to have a 1/4" gap? I installed a 150/70-17 on the back of mine and it literally has about 1mm gap between the tire and break bar.

According to tire mfg specs, the 140/80 Demon penzoil11 has is 141mm wide on a 3.5" wheel.  I had a 140/80 AV46 (142mm wide) on the 02 GS and a 140/80 AV36 (144mm wide) on the 97 GS.  There was little clearance left.

Here's an old pic of the 140/80 AV36 on the 97 GS:



The third pic shows it quite close to the brake torque rod if you can make it out, old pics taken with a Poloroid digital box camera.  Have a better camera now but not a 140/80 tire.   

Sounds about right for jordan's 150/70 although he doesn't say what tire it is.  The 150/70 Lasertec and the 150/70 Road Attack tires I used were 149mm wide on a 4.0" wheel as are quite a few other 150/70 tires according to tire mfg specs.

The 149mm wide 150/70 tires mounted on a 3.5" GS rim would be reduced to about 144mm wide.  Same as the 140/80 AV36 pictured.

I have since bent the brake rod and here's a pic of the 150/70 Road Attack now with adequate clearance:

on the data, how did you take it? GPS? not that it really matters, the trends sound about right. just the stock speedo tends to read high the faster you go, I hear.

i have a 140/80 rear and 120 front. i get higher rpms than your list and actually dont like the taller profile, going back 2 stock
-Alan-

It doesnt matter what the stock gs speedo reads at as it was the same speedo used in both conditions, therefore accuratly protrays the difference between the new and old tire affects on bike performance.

Quote from: Kasumi on June 08, 2007, 03:50:40 PM
It doesnt matter what the stock gs speedo reads at as it was the same speedo used in both conditions, therefore accuratly protrays the difference between the new and old tire affects on bike performance.

Unless it's like my bathroom scale.  The other day I gained 10.6 lbs through the process of urination according to it.

Thanks for that write up penzoil11 

Quote from: Egaeus on June 08, 2007, 07:54:59 PM

Quote from: Kasumi on June 08, 2007, 03:50:40 PM
It doesnt matter what the stock gs speedo reads at as it was the same speedo used in both conditions, therefore accuratly protrays the difference between the new and old tire affects on bike performance.

Unless it's like my bathroom scale.  The other day I gained 10.6 lbs through the process of urination according to it.

LOL! Ive seen loads of bathroom scales like that, just think if everyone had correctly measuring scales, obesity might be down 10% heh.

I guess the 1/4 inch gap was a little generous... I looked at it again and I would say its no more than 2-3mm.  I have yet to use a gps to test my actual speed against what the speedo reads but like kasumi said since I used my speedo for both the before and after, the numbers will be consistent.  I would venture to say that my speedo is off by the 10% that most gs'ers are experiencing (guess I need to get a taller front tire to correct that ). I am posting a couple pics of the gs; one has me pointing to where the brake bar is closest to the tire and the other is the side view of the bike with the new tire.  It lookes gynormous compared to the front tire .
Matt

Holy crap... That tire is pretty damn close.  Careful not to get your tire angle off......