Rear Tire Size

[mcdonaldroadcapt]

My Motortrike Trog is running 225/60/15 tires. I need some lower gearing and was wondering if anyone has had experience with running 225/50/15 instead of the 60 series? How far off will speedometer read? I know it will drop the height about 1 3/4 inches of which I can handle with air bags. Any experience?

Thanks.

[Papa Zook]

My Motortrike Trog is running 225/60/15 tires. I need some lower gearing and was wondering if anyone has had experience with running 225/50/15 instead of the 60 series? How far off will speedometer read? I know it will drop the height about 1 3/4 inches of which I can handle with air bags. Any experience?

Thanks.

The change from a 225/60/15 to a 225/50/15 will add a 6.9% gain in your speedometer reading, meaning that when your speedometer reads 60 MPH you will actually be running 55.9 MPH. There are several speedometer calibrators available, one of the better ones being the Speedo Tuner which sells for about $99 for the Big Twin HDs. Link Below.
Speedo Tuner

[John Luciano]

Can you say Good bye gas mileage
See my next post for an apology.......

[Dwight]

I can't tell what year your HD is but if it is a 6 Speed I wouldn't be suprised if you didn't get better gas mileage. My 09 TriGlide would consisently get better mileage using 5th gear. I think the gearing change will be worth while no matter what the mileage does.

Dwight

[Papa Zook]

A very handy tool:

Tire Size Calculator Link




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[1550vt]

I changed my rears to adjust the gearing when I was running a 6-speed. Mine is not a TG, but that makes no difference. If you change the aspect ratio of the rear tires....it will make a significant difference in the gearing. I went to a tire 1-inch smaller in diameter and dropped my gearing by 4%, which put me right in the "sweet spot" with the 6-speed in high gear around 2900-3000 rpm at 75, which the Twin Cam loves.

Time passes...my 6-speed blows-up and I replaced it with a stock 5-speed which resulted in the trike being geared too short in 5th. My solution was to change my output pulley to a 34-tooth, which brought it all back to the stock factory 2-wheeler gearing (3100 at 70mph). All this to say......if you change anything in the drive-train it will make a significant difference. Changing the aspect ratio on the rear tires of a TG is an excellent way to improve 6th. gear and put it in an rpm range where the Twin Cam likes to run, which is around 2900-3100 in high gear around 70-75mph.

I can almost guarantee you that it will not hurt fuel mileage and possibly even help it. All you are doing running up and down the road at 2600 in 6th. gear is lugging the motor.

[John Luciano]

I stand corrected on this ...I find that amazing . I have heard this from others also. I know the Wings like 3,000 RPM as the sweet spot and that is 65 MPH on mine . running it to 3,500 kills the MPG and lugging it to 2.800 makes it lug too much . GW best Gas mileage is between 55MPH and 66 MPH.
Let us know how it works out. A friend once told me that the most efficient use of fuel is running a motor at it's peek HP and torque. Much as we run our Lawn mowers and power tools. Funny HD engineers don't know this .

[1550vt]

John....I have stood corrected so may times on so many things that I can't find an empty spot to stand on...LOL.

But in general, that Twin Cam Harley loves to run close to 3000 and 3100 feels just perfect. I go back to the introduction of the TG. We all noticed that at 70mph in 5th., she was turning 3100. On the EVO, 70mph was 3,000. The TC is more of a "square" motor and likes the higher rpm. Sure.....you can hurry-up and drop it in 6th. gear as soon as possible and it will cruise down there around 2600, but the TG owners that have gone to the 30-tooth output pulley (stock on the 11 model) are reporting a much more "happier" trike and are not complaining about any loss of fuel mileage that I have heard of.

On the other hand...55-65 is my best fuel-mileage range also. I think the parachute deploys on any trike no matter what the brand at around 65.

[mcdonaldroadcapt]

Just finished the job of changing the 225/60/15 tires to 225/50/15 and the gearing results are outstanding! The change puts the powerband just where you want it on a Motortrike. RPM at 70 in 6th gear is about 2800 and perfect. Getting off from dead stop is much improved with no bogging. Speedometer is off about 4MPH fast but I will adjust. If you need tires, this is a cheap way to get the gearing you desire.