New tires for the Old Ride

[Fearless]

I just installed new rear tires old ones were cracked between the tread ribs around the tire good tread but just for safety off they came. I did however mess with the gearing a little. OEM was 205X65R 15 two years ago I changed the front pulley to the now 30 tooth which I believe is standard on all Tri.s. Not really liking the RPM range I was running I switched to a 205X70R 15 not much change by the tire comparison chart we shall see. When running 65 to 70 it seemed like the motor was really screaming and the heat really went up so now I have to wait and see. Any thought or comments welcome. Ride safe Fred

[ultrafxr]

Fred, there were some posts a while back (about a year ago I think) about changing tire size to lower rpm. At that time the posters either referenced this website or I found it. In any case it give you Tire Size Comparison: https://tiresize.com/comparison/

If I'm understanding it correctly based on your new size compared to oem size it would lower your revs / mile by 3.15657%. I recall in the posts I mentioned that they had gone up to a '75' size tire - 205 / 75 /15 which would drop revs / mile by 6.060606%. Both the 70 and 75 series are a bit taller than the oem 65 - the 70 by 0.8" and the 75 by 1.6" but I don't recall any mention of clearance problems. Obviously your 70 works OK. I'm thinking about going to the 75s possibly but I've got to find that thread and refresh my memory.

[Fearless]

Fred, there were some posts a while back (about a year ago I think) about changing tire size to lower rpm. At that time the posters either referenced this website or I found it. In any case it give you Tire Size Comparison: https://tiresize.com/comparison/

If I'm understanding it correctly based on your new size compared to oem size it would lower your revs / mile by 3.15657%. I recall in the posts I mentioned that they had gone up to a '75' size tire - 205 / 75 /15 which would drop revs / mile by 6.060606%. Both the 70 and 75 series are a bit taller than the oem 65 - the 70 by 0.8" and the 75 by 1.6" but I don't recall any mention of clearance problems. Obviously your 70 works OK. I'm thinking about going to the 75 series possibly but I've got to find that thread and refresh my memory.

Yes there was a lengthy discussion about tire size. It is easier to change the series ie 65.. 70.. or 75, to change gearing. I just wanted to tweak it RPM operating range for my riding area. The tires are not that crazy expensive, if 70 series doesn't do what I'm searching for I'll try 75 series. With less than $110 in the tires Goodyear Viva 3's (recommended by a friend in tire business we shall see). In the case they don't work I can always use the 70 series on my utility tip bed trailer so no real waste. You are correct the are no clearance issues, 75 series would be closer for sure however there seems good room for overall height but not so much for going wider, is not needed anyway. I gained about 3/8 " of ground clearance to boot travel safe Fred

[headheaded]

I will be watching this thread ! I would like to lower my RPM's also. I wonder if this will effect the speedometer or cruise control ?

[ultrafxr]

I will be watching this thread ! I would like to lower my RPM's also. I wonder if this will effect the speedometer or cruise control ?

Yes it does affect the speedo. The comparison web site I posted a link to gives details. I always use the GPS to show my speed so that’s not a worry. If you use a tuner such as TTS or Power Vision they can correct the calibration.

Doubt it would affect the cruise control.

[Fearless]

Yes it does affect the speedo. The comparison web site I posted a link to gives details. I always use the GPS to show my speed so that’s not a worry. If you use a tuner such as TTS or Power Vision they can correct the calibration.

Doubt it would affect the cruise control.

The comparison chart I looked at only gave the 70 series a slower variance on less than 1 mile per hour at 60 heck the Harley Speedometer is most likely off more than that. And the 75 series just over 1.2 mile an hour not enough to get yourself in trouble. Now it's the wait to get good weather to see where I'm at with this experiment LOL. Big dollars to change front pulley if you can't do it yourself tire size not so much. ride safe Fred