Bonneville America Forums Forums Technical Forums General Tech So I tried a 19 this weekend....

So I tried a 19t front sprocket this weekend. Fitted it Friday....Put the 18 back on Sunday. To be honest, there wasn't a huge amount of difference but I lost the urgency and strength the bike has low down. Anyway - worth a try and thought I'd share.

i've gone from the stock 17 then 18 then 19 then 18 then 17 and just put the 19 back on.

i prefer the 19 and am willing to give up "off the line" for "cruising comfort".

am going to look for a smaller rear wheel sprocket(1 tooth) and i think i will be happy.

it's pretty good now but would still prefer a little lower rpm on the hi-way.

i did like the 17 for get-a-ways from the stop light crowd but most of my riding is long range hi-way and the 19 works best for me.

stv

I've been running a 19 toother for around 5 or 6 thousand miles, and lately I'm thinking of changing to an 18 as it's a little easier on the driveline and engine on startups.

As a former truck driver, I have many years of the gospel: "In or out - do NOT slip the clutch" on the brain, and the 19 wants a little slip to launch smoothly. If I don't keep that slippage in mind when launching the 19, I get a little bucking in the engine, which is probably grinding some metals into the oil. Depending upon the grade, it sure is nice to shift into 5th at 60 or 70 MPH though, as is the case with the 19.

My next thing is to try messing with the rear sprocket to see if I can fine tune a little as I still feel like I'm looking for 6th when cruising. Sticking with the 18 front though.

So Stephen...I gotta ask...How was SHE???

Yeah, I knew you takin' about a countershaft sprocket, but a certain Steely Dan song came to mind when I read your topic heading!

Cheers,
Dwight
(I gotta "19" on my BA too, and it's great for cruising on level ground, but goin' uphill you'll find you'll have to down-shift a little more)

TrBoam, I use the 19t front and 41t rear sprocket and since I spend more time on the highway, this is the best combination for me.......Angelis

no that would make you above 19/42. Or lets say drop your rpms more.

I knew I'd get that the wrong way round. So if I stay with 18 up front I need to go up a tooth on the rear - to 43 - to get somewhere between the 18/42 I have today and the 19/42 that was too low for me ???

FYI: 18/42 = 2.33:1 final drive ratio; 18/43 = 2.39:1; 19/42 = 2.21:1; 18/41 = 2.28:1; 19/43 = 2.26:1
If you want to get inbetween the 18 and 19 front sprocket (42 rear) and keep the 18 up front you would have to go DOWN one tooth on the rear to a 41. OR, you can put the 19 on front with a 43 rear which would be about the same.

What is your rpm at 70 mph with the 19?

Thanks Bob - I thought it was down one at the rear. Glad you clarified for me.

I show the following true fifth gear numbers for a Speedmaster with factory sized rubber, and 43 tooth rear sprocket, as corrected for the plentiful speedo errors. I do believe the data is the same for the America.

60 mph

17 = 3700 rpm (59 mph)
18 = 3500 rpm (59 mph)
19 = 3400 rpm (60 mph)

``````````````````
70 mph

17 = 4400 rpm (70 mph)
18 = 4200 rpm (71 mph)
19 = 3860 rpm (69 mph)

Our factory tachs are usually off a bit at around + or - x one hundred or so RPMs, but the above is the basic math, rounded to the nearest whole numbers for MPH.

My 05 Speedmaster speedo usually reports around 5 to 7 mph faster than actual MPH, as supported by both the above and also the roadside radar boxes.