Bonneville America Forums Forums Technical Forums Accessories Front sprocket size?

What size front sprocket do the BA have?
Can I buy a sprocket for the Bonneville and use it on my BA?

/Bonneswe

17 teeth is standard on the TBA. The Speedmaster is 16. And welcome here!

Welcome to the Ba.com Jesper!

You will find all the info you need about the BA here on the forum, use the message board search or post a question and there is always someone that got the answer for you.

Again, Welcome aboard!

Johann

Thanx you guys!

Tbe America, Bonneville and T100 all share the same 17 tooth sprocket. The Speedmaster has a 16. I don't know what the Thruxton has, but I would think the 16 is likely. You can get an 18 or 19 here http://www.newspeedmaster.com/html/18_tooth_sprocket.html but you'd probably only like the 19 if you had the big bore kit in your engine or lived in a very flat area. There are usually a few 16's available on the classified section of these forums.

Welcome to Bonnevilleamerica.com where Triumph's rule and Harley owners drool. I like the 18T sprocket

I've been running the 19T sprocket since day one. with the modifications (Freak,jets,EPCO Exhuast, K&N Filters,Drilled slides,etc...)I haven't had to install the bigbore kit I purchased. Just letting her breath will give you enough power to use the 19T.

I have considered this. How is it two up ???

Quote:

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I've been running the 19T sprocket since day one. with the modifications (Freak,jets,EPCO Exhuast, K&N Filters,Drilled slides,etc...)I haven't had to install the bigbore kit I purchased. Just letting her breath will give you enough power to use the 19T.

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I am putting a 19 on my TBA today. I cant seem to figure the science of it but figure I should not be looking for 6th gear at 60 and the bike should have enough low end torgue to handle the larger sprocket. I would assume jumping up two teeth will be about a 10% change in lower RPMs at high end and a 10% disadvantage at low end. As I have no real urge to be a drag racer with 60ish hp I doubt the lower performance at low end will be a big deal to me.

Satxron, I would love to hear how you like it. I just bought a 18T for my TBA but haven't had a chance to put it on yet (I need to borrow some bigger tools - and I thought I was well equipped!). I did want to try going up, but figure I'll try one tooth at a time. I do ride 2-up quite a bit and I guess you just have to see for yourself.

18 - big bore, no air box, head work, long slash pipes. I think 17 to small, 19 to bi, 18 just right

I have the 18, good choice, at 70 mph you don't feel like there should be 1 more gear ...

RamSound, procratinated but it will be on tomarrow. Will post my thoughts on it. I thought about the 18 tooth also but figured the difference would be too small. I am constantly clicking up at 55ish looking for a gear so we shall see. I have a friend that likes to ride so will try a 2 up for you also. I think it will be fine.

Thanks for the update, I'll be waiting for your results. I hope to get the 18T on mine THIS WEEK as I've procrastinated way too long. I've been told that at 60-70 mph, one tooth will drop the rpms by 500. That's definitely noticable and should stop my wanting to shift over 60. I'll post my findings as well.

RamSound, here is a little app that will give you an idea of the gain you will get. I have no tacometer but think at 70 I am at about 4000 RPM. This link and application says the drop in RPM on a 19 is about 400 thats significant. If you don't know, your rear is a 44 tooth. Hehe if that is correct the TBA will then have a top end of 130.

Calculator

Thanks for the calculating app. I saved it for future reference. My TA is currently stock with a 17 front and 42 rear sprocket. The 865 SMs are 16/43 stock. Anyway, it looks like the rpm drop may be less than I was told. According to the calculator, I would drop 250 rpms at my present 4500 and gain 5 mph if I held the 4500 rpm. That's still very significant. I just want to be sure I still like the bottom end. Right now I really want to loose the urge to shift over sixty.

I told you 44 tooth sorry- Okay, 19 tooth main- From the light more twist to make it move. Once moving feels the same in first. 2nd seems a bit taller. 3rd and 4th are obviously taller, 4th into the 50s is not annoying rpm levels. 5th seems endless! No need to reach for 6th gear, not even in inkling to shift up. There is reduction in RPMs but as I have no tachometer can's say what that reduction is. At least a few hundred lower at 60-70 MPH> No two up information but no doubt two up will not be an issue.

Ok, I finally got my stock 17 changed to an 18T yesterday and it made way more difference than previous posts or the chart app indicated. It takes a bit of the quickness off fast starts but still starts fine in 1st 2-up. 5th is like an overdrive now for use only above 45 mph. There's no tendancy to want to shift to a "6th" anymore. At 3000 rpm it was doing about 50 in 5th where now is more like 57. There is at least 10 mph difference at 4000. The chart app said 5. I like it, but couldn't possibly imagine going up to a 19T. I'm no speedster, but I don't want the gears to get too tall. I've got an overdrive now, what would you want to go higher for. Saxtron, I'd put my money on you eventually dropping to an 18T - you gain a lot without giving up very much. Our bikes torque range is up there (rpms) and quickness is partly what makes this bike really cool. I don't want my Harley friends leaving me at all the lights.

I just ordered one lol, not unhappy with the 19 though it still gets out of the hole fine. For 30 bucks or less I may as well have the 18T available too. The problem with the chart is the lack of a tach. I assumed the TBA at 70MPH is turning 4000 RPMs. The RPM part is critical to the little app.

All I know is I am very happy not reaching for 6th gear.

I do have a tach on my TA. It is definitely useful for such comparisons. By the way, you can get sprockets for under $20. from newbonneville.com or bellacorse.com. The aftermarket sprockets are high quality but don't have the rubber on either side like the stock Triumph ones. I'm not sure if it makes a difference or not as I haven't had enough time to compare.

Ramsound: Newbonneville.com is 19.95 or whatever then tax and shipping took the 18T to 28 bucks. Anyhow??? You have a tach on your BA?? hint hint. What RPMs at 70 when you had the 17T sproket on it and where are you taching now with the 18T

Actually, I can't remember exactly but at 3000 rpm I used to be doing 50 and now it's 57. At 4000 it's about 10 mph faster (about 78). I probably should have made a chart before, but didn't think about it. The one tooth made a really noticable difference - I think I'm gonna like it.

I got my 18T from BellaCorse.com and it was 24.94 including shipping and handling.

I went up one tooth on my America to an 18 tooth. For solo riding it was great but for 2-up riding, that I do most of the time, it was a pain in the butt. I found myself down shifting a LOT more then before for those up hill climbs or coming out of a curve that I had to down shift to. I would rather have the stock 17 tooth any day. Yea, you no longer reach for that 6th gear with the 18 tooth but you down shift a lot more then the reaching for 6th. Just my opinion.
Ride Safe

If you are in between a rock 18t and a hard place 17t you can always fine tune your final ratio by replacing the rear sprocket.

The stock rear sprocket is 42 tooth. With a 17t front your final ratio is 2.47 If you jump to an 18t you final ration is 2.33. If you want a little closer to the 18t move up to a 43 tooth rear. This will give you a final ratio of 2.39 If you want to stay closer to 17t ratio. Keep the 18t front but put a 44 tooth in the rear. This will give you a final ratio of 2.44


I also wonder whenever sprocket sizes come up nobody ever talks about changing the rear sprocket. Every bike I have I usually only change the front sprocket once and fine tune with the rear sprocket.



Fryguy

Interesting, Fryguy, I do feel the stock 42/17 is a bit low and I'm getting used to the 42/18, but as ezrider stated it is noticebly slowler on take offs 2-up. I may have to eventually try (after my trip to Daytona) going to the 18/43 like the new T100 and Thruxton. The 44/18 is almost back to stock. Will the stock chain fit both larger sprockets or is a different chain required? I guess the reason many of us change the front is that it is an easier change (from what I can tell). Which set up do you use?

When I am usually looking into changing sprockets I always say what I am going to be using this bike more for? I start at the front sprocket. You get the most jump in ratio changing the front sprockets. I use the rear sprocket to fine tune the ratio. Currently I am using the 18/44 setup. It still gives me a low end grunt with a little less revs on the highway, the key word is a little.

Yes the chain can handle changing both sprockets unless you go with a 17 front with a 47 rear for a ratio of 2.76 I have never tried this setup but you may have to get a longer chain. This will move your power range to all be under 3500 RPM. Great for racing bar to bar, not to good on the highway. Also, some say this decreases you wheelbase
and helps your bike handle a little better. I have yet to see this but it sounds like a good theory.


Fryguy

If it's not too hard to do, I guess I need to order a 43 sprocket and give it a try. I do want something a little higher than stock. I ride about 60% city / 40% hwy. but where I live there's usually some highway riding on every local trip. I'm sure the new 18/42 will be best for the long trip to Daytona in March. I really want to find the best compromise to avoid changing sprockets back and forth. Thank for all the input - big help!

Not a problem. To change the rear sprocket, its pretty simple. I loosen the rear axle bolt and pull the axle out of the singarm until its flush with the rear wheel. This will enable you to swap out the rear sprocket. Just make sure the you loosen the rear sprocket bolts before you loosen the axle bolt.


Fryguy

Boy, Fryguy, that's a heck of a lot simplier method than described in the shop manual. It starts with "remove the rear wheel". I assume that in your method you can use a lift with the rear wheel just touching the ground. I may have to give this a shot. Two questions - does the Triumph front sprocket with rubber isolators make a difference? I got my 18T from BellaCorse, but only the Triumph has the rubber. And - Where is the best place to order a rear sprocket? Also, in your earlier post, you didn't mention the possibility of a 17 front and 41 or 40 rear. (17/41 2.41:1, 17/40 2.35:1) Would that make sense? Ok, that was 3 questions, but I couldn't resist.

Right,

The manual tells you to remove the rear wheel. You don't have to, I think they tell you to do that to cover their ******.
You can use a lift to take all the weight of the bike off the rear tire. Loosen the sprocket bolts, then loosen the axle bolt, lift the bike, then slide the axle flush with the end of the wheel. Then you can take of the rear sprocket and replace it. Then just do the reverse to put back together.

In regards to the 17t front sprocket with larger tooth rear sprocket will increase the ratio's that probably wouldn't be good for all around riding.

A 17t with a 43t rear will give you a ratio a 2.53. If you bump upto a 44 rear tooth if will give you a ratio of 2.59 which is closer to the stock Speedmaster ratio of 2.63

You can get the sprockets from JTsprockets.com They make replacement sprockets for all bikes. The rear sprocket type is a JTR 1792. Coincidentally, The America's and Speedmaster rear sprocket is the same as the 00-05 Suzuki GSXR 750's as well.


Fryguy

I found Brent can get them as well. In my previous post I asked if you had thought about 17T with a SMALLER rear, not larger. (17/41 = 2.41:1 or 17/40 = 2.35:1). Going one down in the rear with the stock 17 would also move the same direction. Also, you didn't comment on the rubber isolators, any significance?

Sorry about that.

Yes you can go lower in the rear but only one tooth to a 41t. This is the only sprocket they offer under 42 teeth. With a 17t front and 41 tooth rear it should give you a ratio of 2.41 which will put you between the ratio's of 18t front/43 rear of 2.39 and 18t/44rear ratio of 2.44.

My replacement front sprocket does not have the rubber isolators on it and I am not using them. I have had no adverse reactions yet.


Fryguy