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15 Tooth Front Sprocket: Wicked Good

15K views 62 replies 18 participants last post by  JerryG  
#1 ·
I had put almost 12,000 miles on my 2022 G310GS before I read Jenny Morgan's (JMo on advrider.com) discussion on, and endorsement of, changing out the G310GS' original 16T front sprocket in favor of a 15T front sprocket. So, I switched to 15T, mostly to improve off-road performance and reduce the bike's tendency to stall at the worst off-road moments.

I'm now half way through the MABDR riding with 15T. OMG! I can't stall this bike; it digs in and just goes. It will start from a standstill in fourth fricking gear without stalling (oops - I forgot to downshift). Most of the time, I'm smoothly riding along in third gear with downshifts to second only for tight gravel and rick strewn corners and gnarly uphill. First gear is great too, just too low except when I need extreme grunt or for unknown surface situations like the four water crossings I did yesterday. When I do start in first, I shift up to second almost immediately. This is with TKC80s. I can't wait to finish up these TKCs so I can see how 15T performs with the MotoZ RallZ I plan to use next and/or the MotoZ Desert H/Ts I used in Death Valley (with 16T) and took off to save for future desert use. I'm sure the 15T with RallZs will be awesome.

Of course, I need to mention the flip side, performance on road and at high speeds. In the twisties, the acceleration provided by the 15T is wonderful. At high speeds on highways, I haven't been on a level highway yet, but I did do some long uphill and long downhill grades at highway speeds yesterday. Going uphill, the bike maxed out at 76 mph; going downhill, I got it up to 87 mph. So, I'm confident it will do 80 mph on level terrain. Previously, with 16T, I maxed out at 91 mph, but given my BMW owner's manual claimed top end of 88 mph, I suspect I had a tail wind helping me get that 91. Note, at these higher speeds, I ride fully tucked behind my Rally Raid touring wind screen to lower drag.

So, given the wicked improvement re acceleration and lack of stalling, words fail me when I try to express how strongly I recommend switching to 15T. If you ride your 310GS off-road, if you have ever stalled your 310GS on- or off-road, you should most definitely try a 15T front sprocket. The best thing is - it's cheap and easy, I got mine for $35 and it took me 30 minutes to install.
 
#2 ·
So, given the wicked improvement re acceleration and lack of stalling, words fail me when I try to express how strongly I recommend switching to 15T. If you ride your 310GS off-road, if you have ever stalled your 310GS on- or off-road, you should most definitely try a 15T front sprocket. The best thing is - it's cheap and easy, I got mine for $35 and it took me 30 minutes to install.
Going 15T at the front was the first mod that I did (following JM advise) and never looked back.
Getting more punch at the lower end = better for off road.
Enjoy your trip trip JG.
 
#6 ·
It’s quite a tribute to electronic engine controls how well the 310 can respond to gearing. It’s quite difficult to stall when you consider it’s a low torque, high rpm motor. And yet you can go up or down in gearing and still get acceptable performance. Gear up and you’ll have a better road experience. Gear down for more power application for off-road use. Having both slip/assist clutch plus digital wizardry really adds to versatility.
 
#39 ·
Update on
I got mine at... www.motosport.com ...you'll have to enter your bike's info and select 15T once it shows the sprockets for your bike. I tried to provide the exact link and it didn't test out.
Update: I had to replace the 15T sprocket I got from motosport.com after 11,088 miles. I also needed a new chain, but the rear OEM sprocket was still good. I was ~4,000 riding miles from home in Oregon at the time; fortunately, I bought an extra and brought it with me. I consider this fair wear given that this included the MABDR, the PABDR-X, the Trans America Trail (TAT) Atlantic Spur from the Appalachia Mountains to Cape Hatteras, NC, the BWM National Rally in Richmond, VA; and the Trans America Trail from Hot Springs, NC, to Port Orford, OR.

Now I need to buy a few more spares and motosport.com doesn't list them for the 310GS anymore.

The Sprocket Center is out of Superlite 15T, but has the JT 15T for $26.95 (UK HQ/US warehouse); anyone have experience with JT sprockets?

Amazon has an China AHL version for $15.69; anyone have experience with AHL?

Ebay seems to have lots of listings for $16 no-name versions from China; anyone gone that route?

I generally prefer a name-brand version for this type of part, so I'm leaning toward the JT. Thoughts?

Other options?
 
#16 ·
im 90-95kg
$30 eBay screen
have hit the limiter in 6th more than once so hills and wind wouldn't be the issue.
if I sit fully upright then I won't be able to do much more than 145 or so.

don't have too many pics on the laptop but here's one that kinda shows the screen, its fairly tall but its main purpose is to protect the GPS.
with the panniers etc on, around 140 is my max unless its downhill.
I did actually hit the limiter at 180 with the factory gearing on this trip but it was down a long hill, when I got to the bottom I immediately felt the lack of power and dropped straight back to 140ish 😂

Image
 
#17 ·
im 90-95kg
$30 eBay screen
have hit the limiter in 6th more than once so hills and wind wouldn't be the issue.
if I sit fully upright then I won't be able to do much more than 145 or so.
don't have too many pics on the laptop but here's one that kinda shows the screen, its fairly tall but its main purpose is to protect the GPS.
with the panniers etc on, around 140 is my max unless its downhill.
I did actually hit the limiter at 180 with the factory gearing on this trip but it was down a long hill, when I got to the bottom I immediately felt the lack of power and dropped straight back to 140ish 😂
My Rally Raid Adventuring Screen (made from acrylic) cracked nearly in two after taking a rock hit on the Mid-Atlantic Backcountry Discovery Route here. Just few days ago, I bought a version of your windscreen on Amazon (free return in case I don't like it). It's polycarbonate (nearly indestructible) and, like yours, only coast $30 (link below). Given what you've described here, I fully expect to hit 160 kph (99 mph) on the flats and 180 kph (112 mph) going downhill once I install it. If I don't, I'm going to sneak over there and swap out our engines in the middle of the night. :love::rolleyes:


P.S. Given our weight difference and what's pictured on your bike, my GS must be carrying ~23 kg (50 lbs) less than your GS is. I think the engine swap is my only way. 😈

Image
 
#19 ·
Sorry I wasn't clear (unlike my shields 😉 ). My picture is with my Rally Raid Adventure Touring Windscreen which is designed to work with Rally Raid's bar risers and bark busters. That's the one I'm replacing because it cracked nearly in half from a rock strike. I would have bought another one, I like it that much, but since RR changed their new web site and mail pricing system, it's no longer economically viable; I'd have to pay $100 shipping for a $124 windscreen that would be just one more rock away from cracking again.

The $30 polycarbonate windscreen with free delivery and free returns from Amazon solves that problem, but does leave me with the clearance issue. I'll install the Amazon windscreen sometime this week during my TAT prep work. I'll post a picture with it installed then. I don't want it hitting the windscreen, so I will trim it if it does. I've trimmed windscreens before; most recently a few years back to create a short windscreen on my K1300GS. That turned out well, but the edges never had that professional look. For this go around, at $30, if I don't get it perfect, it doesn't matter. I start the TAT on July 1st even if I have to switch back to my little stock non-windscreen. In fact, I may do a test ride with that; that would leave me and my Garmin Nav VI in the open, but it would also be optimal for reducing wind noise around my Schuberth C4 Pro Carbon. I know this because when I stand up and put my head in clean flowing air, the helmet gets ultra quiet.

More to follow.
 
#22 ·
Schuberth's claim of 85 dB is only valid on a naked bike that leaves the air around your head undisturbed. On a bike with a fairing, this is very evident when you compare how quiet the Schuberth is sitting in the fairing's turbulent air vs when you stand up and put the helmet in non-turbulent/less turbulent air above the fairing.
 
#23 ·
I found that on a proper faired unit, like BMW RT or Goldwing the helmet was just as quiet in or out of “clean air”. I’ve only experienced noise issues with the ”let’s slap a screen on there” designs in use today on Adv bikes. Designing things for looks tends to have that result. Many times trying to achieve too many purposes ruins the whole effect. I’d advise try riding with no screen, add screen on same ride. With inadequate design, often better off with no screen than the darn buffeting provided by screen inadequacy. Quietest helmet in world gets noise when bufetted past it’s parameters.
 
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#25 ·
Yes an efficient fairing will be big and not a great fashion accessory. But removing the friction increases over all efficienty and handling on the road going machine. It’s like putting off road looking gear on a street bike, calling it an “Adventure Bike” and expecting it to perform at real dirt operations. Yeah right. It ”looks” like it should eh? The little bikini fairings look like they should work right? Very very rare actually, it’s a design problem inherent to being too small. Much of motorcycle design has gone down the I’ll advised path of “it looks cool” and sells. No real talk of “can it really work”. This is why there’s a preponderous amount of “Adventure Bikes” that are not much for off road without thousands of dollars of added money. Never designed for off the road travel. Personally I found the 310GS to be the worst off road moto I’ve ever ridden in stock form. My beheomoth 1150GSA was far better off road! Just weight too much. A soft sprung street bike with too much weight. only saving grace being BMW didn’t lie and was open about the 310 being for “occiasional light trail use” or something like that. With fist fulls of dollars one can get some dirt use from the 310GS but what if the fashion folks stepped back and let enginneering design a real dual sport around that sweet 313cc power plant? Not going to happen of course, more profits in current platform. So long winded to say “Do you want function or do you wish fashion” fits both windscreens and moto choice.
 
#30 ·
I had put almost 12,000 miles on my 2022 G310GS before I read Jenny Morgan's (JMo on advrider.com) discussion on, and endorsement of, changing out the G310GS' original 16T front sprocket in favor of a 15T front sprocket. So, I switched to 15T, mostly to improve off-road performance and reduce the bike's tendency to stall at the worst off-road moments.

I'm now half way through the MABDR riding with 15T. OMG! I can't stall this bike; it digs in and just goes. It will start from a standstill in fourth fricking gear without stalling (oops - I forgot to downshift). Most of the time, I'm smoothly riding along in third gear with downshifts to second only for tight gravel and rick strewn corners and gnarly uphill. First gear is great too, just too low except when I need extreme grunt or for unknown surface situations like the four water crossings I did yesterday. When I do start in first, I shift up to second almost immediately. This is with TKC80s. I can't wait to finish up these TKCs so I can see how 15T performs with the MotoZ RallZ I plan to use next and/or the MotoZ Desert H/Ts I used in Death Valley (with 16T) and took off to save for future desert use. I'm sure the 15T with RallZs will be awesome.

Of course, I need to mention the flip side, performance on road and at high speeds. In the twisties, the acceleration provided by the 15T is wonderful. At high speeds on highways, I haven't been on a level highway yet, but I did do some long uphill and long downhill grades at highway speeds yesterday. Going uphill, the bike maxed out at 76 mph; going downhill, I got it up to 87 mph. So, I'm confident it will do 80 mph on level terrain. Previously, with 16T, I maxed out at 91 mph, but given my BMW owner's manual claimed top end of 88 mph, I suspect I had a tail wind helping me get that 91. Note, at these higher speeds, I ride fully tucked behind my Rally Raid touring wind screen to lower drag.

So, given the wicked improvement re acceleration and lack of stalling, words fail me when I try to express how strongly I recommend switching to 15T. If you ride your 310GS off-road, if you have ever stalled your 310GS on- or off-road, you should most definitely try a 15T front sprocket. The best thing is - it's cheap and easy, I got mine for $35 and it took me 30 minutes to install.
That’s great news! After doing the off-road training on mine at the rally I ordered one a few weeks ago for this reason.
 
#32 ·
Here's JMo's rather definitive post on your question...


The "here" in the first paragraph refers to the following web site...


JMo's post is pasted below.

[START OF JMo QUOTE]

Thanks for the quick reply GNR' - for info (and for anyone else wondering), I know someone posted a link to a gearing calculator before, but I found this simple site here that helps to work out the difference in ratios (plus how many +/- links in the chain length are likely to be required too).

Based on the stock gearing being 16/40 - that equals a 2.5 ratio...

15/40 = 2.67 = -6.3% (GNRs bike currently)

16/43 = 2.69 = -7.0% (My bike currently)

15/41 = 2.73 = -8.5%

15/43 = 2.87 = -12.8%

...the percentage change is the drop in speed for the same amount of RPM, or conversely the % increase in torque.

So in summary, changing the front sprocket by -1 tooth (as GNR has just done) offers a little less % change than adding +3 teeth to the rear (as I currently have on my bike), while going to 15/41 offers more of a drop, and is, as I suspected, probably the best combo for more serious off-road use, while retaining reasonable on-road performance too. Any more than that (eg. 15/43) would be too much of a compromise on road I imagine.

for info. the rear sprocket PCD on the G310GS is the same as the twin-cylinder F650GS, so technically you could grab an OEM rear sprocket from that bike (47T) and go crazy - however, 16/47 = 2.94 = 14.9% - so probably way too extreme for most owners.

Hope that helps...

Jenny x

ps. I'm going to hang onto the 43T rear though to pair with a 15T front - just in case I decide to ride the Rubicon on this bike too ;o)

[END OF JMo QUOTE]
 
#33 ·
Jerry G thanks for this. I also connected with JMo and based on how i use the bike I ended up going 15/41. I also had to source the sprockets from Carpi Moto in IT. Seems like US sources have run dry on the 15T and didn't have a 41T. Since I'm coming off 40/15 already, I will report if I notice the change to the 41/15.
 
#36 ·
Most motos come with excessively high gearing. Fine for getting max mpg, top speed (maybe). One of the best bang for buck off road wise is lower gears. Smaller sprokets induce chain wear, think of that As you switch. Second best bang for buck is real off road worthy tires. Just recall that while very capable, the 310 has a major wieght problem that can be an impediment. I believe BMW said something to the effect “light adventure riding” and that’s what they designed for, a success I’d say. A super light adventure bike