Math Question
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Novice
Joined: Apr 2007
Posts: 19
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From: Idaho
Math Question
If you had a 90mm high 16" tire that runs 3000rpm @70MPH
what would be the reading with a 85mm high 16" tire?
5mm (0.19685") smaller circumference per revolution
Thanks
Zeroroadkill
'00 FLHRI
A little history about this question:
The Metzler ME880 140/90B16 rear tire is 90mm high and I run 3000rpm @70MPH. The new Metzler ME888 is not offered in a 140/90B16, but instead in a MU85B16 which is 5mm smaller in heigth than the ME880 140/90B16. I'm considering the newer ME888 tires, but need to know how the lower profile tire will effect RPM to MPH readings.
what would be the reading with a 85mm high 16" tire?
5mm (0.19685") smaller circumference per revolution
Thanks
Zeroroadkill
'00 FLHRI
A little history about this question:
The Metzler ME880 140/90B16 rear tire is 90mm high and I run 3000rpm @70MPH. The new Metzler ME888 is not offered in a 140/90B16, but instead in a MU85B16 which is 5mm smaller in heigth than the ME880 140/90B16. I'm considering the newer ME888 tires, but need to know how the lower profile tire will effect RPM to MPH readings.
Cruiser
Joined: Jan 2013
Posts: 149
Likes: 0
From: Treasure Coast, FL
Assuming the 'reading' you are wanting is speed = 68.8MPH
Cheers
Edit: assumed you wanted the new speed @3000RPM .. if what you want is RPMs for 70MPH w/lower profile tire it's 3052
Cheers
Edit: assumed you wanted the new speed @3000RPM .. if what you want is RPMs for 70MPH w/lower profile tire it's 3052
Last edited by zdrifter; Mar 6, 2013 at 01:47 PM.
Outstanding HDF Member
Joined: Jan 2011
Posts: 2,590
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From: Western Illinois, land of bad roads, and corrupt politicians
You might want to consider.... 5mm is not much. Think about it this way. Old 90mm vs new 90mm. There's going to be at least 5mm difference.... more than likely, more than 5mm. Now throw tire pressure into the mix. A difference of 5 lbs in the trie is going to change the tire footprint on the pavement.... probably 5mm or more.
You are not going to notice a change
You are not going to notice a change
Last edited by shooter5074; Mar 6, 2013 at 02:39 PM. Reason: My pants filled up with pudding
Seasoned HDF Member
Joined: Apr 2008
Posts: 10,135
Likes: 4,780
From: Sandpoint, Idaho
Cant be accurately figured untill you compare the "actual" tires. I have seen a very large difference in the same size tires from different makers.
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Road Warrior
Joined: Mar 2011
Posts: 1,456
Likes: 132
From: Deep South, Louisiana
I'm just a simple Coon *** from south Louisiana, but I would have my buddy measure the 90mm tire from the rim to the ground. Then I would let air out until the rim gets 5mm closer to the ground which I would now put me at 85mm. I'm going to guess the tire pressure close to 28-30lbs and I think that would be safe enough for a 2 mile ride. I would go test ride it and have my answer. When I get home I would put air pressure back to normal. I wonder how much the gear ratio has changed?