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39 Tooth T120 Results

58K views 227 replies 58 participants last post by  tahtye 
#1 ·
The other thread seemed to be getting stale, so I thought I would report on the results of installing a 39 tooth sprocket on my 2016 T120.

I purchased a steel/alloy combo from Supersprox, in silver/black. The part number was: RSB1521-39, silver/black, drawing # 2012.

My bike lift was tied up with my Trophy, so for installation, I put the centerstand up on a 1" board to give the tire extra clearance for removal (not sure it was necessary). Removed both mufflers. Pre-checked the alignment by using digital calipers to see if I could measure the chain-bolt distances accurately. Measuring from the front of the aluminum block to the indent where the bolt screws in, I found pretty much equal distances of something like 1.83 inches on both sides. So I knew I could measure distances accurately on the setup, and that they were equal from the factory. I marked the outside flat of both bolts so I could keep track of turns, just in case.

Removed the axle, tying up the rear brake, changed the sprocket, using blue locktite with 55 nM torque, and with a bit of fussing, got the wheel back on. I turned the adjustment bolts in about 8 turns each. When done adjusting the chain, the clearances on both sides matched to something like 1.38 inches on both sides. I will double check the alignment with a string later, but for now it is definitely not out of alignment. The axle is now near the center of its movement, which makes one wonder if 39 teeth weren't planned, but they installed 37 teeth to meet Euro 4 specs.

As for the results, they are great. It is only about a 5% change, but it really makes the bike easier around town and starting off. It just seems more natural starting out from a light, etc. On the highway, 3,000 rpm is 65 miles per hour in 6th. It is not a huge difference from stock, but it is enough to be noticeable.

As others have found, I would say changing the rear sprocket from 37 to 39 teeth is worth the effort.
 
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#86 ·
Sweet! Post a picture of it! Mine got delayed for whatever reason from UPS, but it's almost here, finally! I'm curious to see what a real one even looks like.
 
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#88 · (Edited)
There really is no point to all this except wasting your $$$'s.

After you have let the clutch out in first and are heading out just stamp it down a gear and head for the red line if you need too.

Isn't that a better idea than one less on the drive or five more on the rear?

Seriously, I have a six speed box on my R.

If I max'd each gear I would be jailed no matter the drive gearing.:grin2::grin2:
 
#99 ·
There really is no point to all this except wasting your $$$'s.

After you have let the clutch out in first and are heading out just stamp it down a gear and head for the red line if you need too.
There is a point. I went 39T on my T120 initially because 6th gear was ridiculously high, giving a theoretical top speed of around 160mph.
The added benefit was better revs when trying to stick to a 30 limit. Previously I was up and down the box between 2nd and 3rd at that speed.

On my 2013 Thruxton, after my tuning mods were complete, I went the other way and raised the gearing a tooth on the front sprocket. That was because I was always looking for a 6th gear that wasn't there. I don't find myself doing that on the Bonnie even with the lower gearing.
 
#91 · (Edited)
Un-F'ing-believable... UPS lost mine. Great, now I get to wait a literal additional year & a half again.

Honestly, what else should I really expect from a shipping company, where on the side of the big brown truck, there is a giant word on the side... And when you sound that word out, it makes the "OOPS" sound (UPS)

I guess I'll just e-mail the dude that I've been trying to buy from for months, to just get a refund.
*sigh*
 
#97 ·
Oh wow... That looks really, really good. Even better than I thought it was going to look, in actual "real" life. I really hope mine gets here.

How hard was it to take off the rear tire? (What I mean is, once you pull the axle out, do like 700 spacers & washers & S%@* come falling out? And when you go to put it back on, is it like completing a puzzle of pieces?)

My dealer will install mine for free. But it's a 2 hour round trip that I would avoid if I could. (Plus, when they greased the back of my rear brake pads under warranty, the rear ABS sensor later got sheared off because they did a "quick" job putting the rear tire on. And they had to send their box-truck to come get my bike. So was that something difficult to mess with as well?)
 
#98 ·
Easy swap since I have the center stand. Tire came off easily, I didn't need extra clearance. Not a bunch of spacers, etc. It was more of a pain dialing in my chain ensuring I could get it to the spec.

I agree on the quality. I wasn't expecting it to be as well made and nice looking as it is, especially looking at it side by side with the stock.
 
#105 ·
I really wanted to get that new 39T sprocket from these guys...ordered it early this month, got my credit card charged, and then waited. Called to ask when I could expect it, they didn't know, ended up saying they thought it would be a bit longer, but they couldn't say exactly when...so I said that's enough: while I want this thing, I don't need it, please cancel my order and issue me a credit on my credit card. They've said they've issued the credit, but I'm still waiting to see it appear on my account. A bit disappointed, but maybe I'll get one in some months when they've got their act together better. At $147 this thing is not cheap, but feel a 39T would be an improvement. Oh well, back to the stock 37T that has served and shows no sign of wear.
 
#106 · (Edited)
@grebmrof
FYI... I got mine this week and installed it yesterday... I REALLY like it... How long ago did you place the order? Did you do it through the USA Supersprox site? From what I gather, the "On Demand" section of that site in now accurate, and roughly a 2-week turn-around from order placed, to order received. (I posted two detailed images yesterday in the "Show your Thruxton 1200 mods so Far" thread if you are interested. If you call Supersprox USA phone, ask to speak to Craig, he seemed to be the one at the top of the On Demand Stealth Sprockets in the US.
 
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#107 ·
I had placed the order on Sept 5. First calling them and after talking with them about it, they directed me to their website to place the order, which I did. When I simply checked a couple of weeks later to find out a status I did talk to Craig and that's where I got this indefinite answer that they really couldn't tell me if they had them in, when I would/should expect it...I know a bunch of folks here have gotten them, but I then felt real uncomfortable with when it would arrive. My T120 was apart for a new rear tire, which I had gotten mounted, it was a prime opportunity to change out the sprocket - but our riding season is quickly drawing to a close here in NE Ohio, so I decided I wanted to ride the bike more in the coming weeks vs look at it all apart. Maybe sometime in the next year I'll either reorder from them or perhaps someone else may be marketing them and I'll get one of theirs. Oh well, that's the way it goes sometimes...oh BTW still waiting to see that credit pop up on my Visa account...I hate to do this, but I'm just about ready to file a dispute with my cc company, geez...
 
#108 ·
@grebmrof
Geeze, I'm sorry to read that. I get how frustrated you are. It was driving me bonkers trying to get one on my bike for over a year... I just find it so odd the a few members on here, including myself, were recently able to order one, and actually receive it. I KNOW you're not stupid, but did you try to order one of the "On Demand" ones they actually make in Iowa, from a solid 39t disc sent from the Euro factory in Poland? And NOT the pre-maid, bike specific, ones that they make in Poland, and then ship over. (Ultimately, each are the same product.) The pre-made ones I don't think we will ever see. Well, regardless, best of luck & hope you actually get one someday in the near future. Cheers.
 
#111 ·
Just ordered mine. Biggest concern is getting the chain tension correct. May let the dealer take care of this for me and see about getting the front brake dampers at the same time. Thanks gabbydad for the photos and continuing info on this! I was just in NJ and have to say it is a really nice place! Had dinner at a place called the Blue Claw, cool place!
 
#125 ·
I'm about to pull the trigger on the Supersproxx 39 tooth rear sprocket and wondering how much mileage is too much before I replace the chain as well. I'm only a little over 2k miles at this point but it'll go up before I get the sprocket. Hate to buy a new chain at this point since it's barely broken in but don't want to have noticable uneven wear. I'm probably worrying needlessly right?
 
#128 · (Edited)
I ordered a 39 tooth sprocket off the Supersprox site on Friday, 10/20. Got a forwarded email from them instructing the factory to ship it, then today the factory rep says he doesn't know when he'll know if they can even make it! Since then they've updated the website to reflect lack of inventory. Craig, the rep there, was pretty understanding, but just a heads up... I ordered the last one in black and may never actually get it. Either that or the website was wrong and they didn't have any at the time. I'm thinking JT or another company will have em available before Supersprox gets their act together.
 
#131 ·
Same story here, however I ordered mine (Black 39T) on Wednesday October 18th and at that time I saw the stock on the website change from "available" to "N/A" just after having placed the order. On October 23rd, I received an email from Craig where he was forwarding a request on to the Sales Dept, requesting that they "review the attached invoice" and " please ship the goods". No other official notification regarding shipment just yet. Fingers are crossed.
 
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