Selden Posted March 23, 2018 Share Posted March 23, 2018 (edited) Based on many positive industry reviews, I decided to try a new Pirelli Angel GT on my 1999 R1100RT. Unfortunately, I wasn't paying attention when I ordered from Amazon, and didn't discover until after it shipped that I had ordered a 120/60-R17 instead of the recommended 120/70-R17. I read a bunch of size comparison articles, decided there would be no harm with the lower profile, which might lower the seat a smidge — always an important consideration for someone with a 29" inseam. The 120/60-R17 measures ~10 mm smaller in diameter than the old (very worn) Michelin PR3, which translates at most to ~2-3mm difference in height at the front of the seat, which is barely noticeable, but it's definitely slightly easier to get both feet on the ground. The bike stands up very slightly more on the sidestand, with no noticeable difference in hoisting it on to the center stand. The main difference will probably be that it makes an already optimistic speedometer even more so, but that could help reduce the risk of speeding tickets. If you are inseam-challenged, it might be worth looking into a lower profile front tire. The Amazing Randy mounted the new tire yesterday, and I went out for a ride today. Like any new tire, it turns in far easier than the worn tire it replaces. Other than that, it's far too soon to tell anything about handling. I hope that when it gets some miles on, it won't start howling the way all my PR3s did. Edited March 23, 2018 by Selden Link to comment
Bud Posted March 23, 2018 Share Posted March 23, 2018 Good luck and let us know how it works out, long term. Link to comment
Paul De Posted March 24, 2018 Share Posted March 24, 2018 The smaller diameter will also effectively decrease rake and trail slightly which would tend to make the steering slightly more responsive. And to the degree that it does this on a R1100RT that is a good thing as I always felt the steering on my R1100RT was too slow requiring a lot of input force to get the bike to be flickable. When you get the tire scrubbed in and some miles come on back and share if it did make your RT more flickable...inquiring minds want to know Link to comment
LittleBriar Posted March 24, 2018 Share Posted March 24, 2018 I would expect you couldn't do this on a newer bike with ABS, traction control due to the difference is wheel speed? Link to comment
dirtrider Posted March 24, 2018 Share Posted March 24, 2018 I would expect you couldn't do this on a newer bike with ABS, traction control due to the difference is wheel speed? Afternoon LittleBriar I would be very surprised if a 120/60-R17 vs a 120/70-R17 made either the ABS or the traction control default. The usual difference between the two tire sizes is around 20mm difference in diameter (Selden says he only has 10mm?). That is only around a 4% difference & probably well within the variation window built into the ABS & traction control systems to account for tire pressure, tire manufacturing differences, as well as cornering (tire lean) diameter changes. Link to comment
Selden Posted March 25, 2018 Author Share Posted March 25, 2018 I was comparing diameter of a totally shagged PR3 with a brand new Angel GT, so 15-20mm is probably about right when comparing two new tires. Different brands of the same nominal size may not measure the exactly the same. Link to comment
duckbubbles Posted March 25, 2018 Share Posted March 25, 2018 Very easy to ding the front wheel with a 60 series tire. DAMHIK Frank Link to comment
Paul De Posted March 26, 2018 Share Posted March 26, 2018 Very easy to ding the front wheel with a 60 series tire. DAMHIK Frank Good point as I had to replace my rim after a hard square edge hit with the stock 70 series Metzler. So I maybe more prudence on speed when the road is really bad.. Not sure that Seldon would see the journey to the center of the earth deep potholes like we get in freeze/thaw country through! Link to comment
GordonB Posted March 26, 2018 Share Posted March 26, 2018 On a lighter note there is this; Pothole swallows motorcyclist Link to comment
Lowndes Posted March 26, 2018 Share Posted March 26, 2018 (edited) Very easy to ding the front wheel with a 60 series tire. DAMHIK Frank Good point as I had to replace my rim after a hard square edge hit with the stock 70 series Metzler. So I maybe more prudence on speed when the road is really bad.. Not sure that Seldon would see the journey to the center of the earth deep potholes like we get in freeze/thaw country through! Paul de, we have our own reasons for potholes down here in the Sunny South. Meteor Crater is one of our medium-size potholes. You may have heard of it. Edited March 26, 2018 by Lowndes Link to comment
Whip Posted March 27, 2018 Share Posted March 27, 2018 I would expect you couldn't do this on a newer bike with ABS, traction control due to the difference is wheel speed? Afternoon LittleBriar I would be very surprised if a 120/60-R17 vs a 120/70-R17 made either the ABS or the traction control default. The usual difference between the two tire sizes is around 20mm difference in diameter (Selden says he only has 10mm?). That is only around a 4% difference & probably well within the variation window built into the ABS & traction control systems to account for tire pressure, tire manufacturing differences, as well as cornering (tire lean) diameter changes. I think he meant 20mm diameter difference would only lower the bike 10mm. It should change the handling a bit. I have no idea how it would affect the ABS. Link to comment
dirtrider Posted March 27, 2018 Share Posted March 27, 2018 I would expect you couldn't do this on a newer bike with ABS, traction control due to the difference is wheel speed? Afternoon LittleBriar I would be very surprised if a 120/60-R17 vs a 120/70-R17 made either the ABS or the traction control default. The usual difference between the two tire sizes is around 20mm difference in diameter (Selden says he only has 10mm?). That is only around a 4% difference & probably well within the variation window built into the ABS & traction control systems to account for tire pressure, tire manufacturing differences, as well as cornering (tire lean) diameter changes. I think he meant 20mm diameter difference would only lower the bike 10mm. It should change the handling a bit. I have no idea how it would affect the ABS. Morning Whip It wasn't stated that way & in fact was a measurement not a lowering statement ( The 120/60-R17 measures ~10 mm smaller in diameter than the old (very worn) Michelin PR3. Selden did post later that it was comparing a worn tire to a new tire. Link to comment
Rougarou Posted March 27, 2018 Share Posted March 27, 2018 Tire size comparison I used on of these types of tools when I was in the off-roading to calcuate gear changes, but it does come in handy for other things. 1 Link to comment
Selden Posted April 3, 2018 Author Share Posted April 3, 2018 Here is a 300-mile update, more on the Pirelli than on the tire size. It's a tire. Compared to some new tires I have used, it doesn't fall in to a turn; very neutral. Other than that, I can't tell the difference from any other front tire I have used on the RT. I will probably put another Angel GT on the rear wheel @~130,000 miles, which is coming up fast, as we're trying to do a lot of 2-up riding this month to get ready for a big trip. Link to comment
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