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Discussion Starter #1
Hi Y'all,

I just bought a new Bonneville 2018 T120 Bonneville from a very nice shop in Greensboro NC, Select Cycle. There were two issues with the bike. 1) the seat is a bit low for my 6" height. 2) the gearing is all-together too high, especially noticeable getting underway in 1st gear.

To fix the seat, I bought and installed a British Customs "Slammer" seat, which is about 1" taller where you sit. I had to remove the rear grab bar and other related chrome parts to fit the seat. The bike looks better (more "old-school badass") and it sits higher.

To fix the gearing, I bought a black, 40 tooth sprocket from Supersproxets USA for $45.95 (Product ID: RFE1125794 Product Name: RFE2012 for Triumph 1200 BONNEVILLE T120 [2016-2019]) Installing the sprocket was easy. It was a bolt-on perfect fit. There was enough extra length in the chain so that all I had to do was move the rear wheel forward, nearer the front end of the chain's adjustment range. I spent 15 minutes making sure I got my chain adjusted just right...especially not too tight!

The bike rides much better with the lower gearing. Second gear is more usable where before it was too tall for parking lot speeds. I have no idea why Triumph sells the bike over-geared (IMO). I highly recommend this easy mod!

More mods to follow, including the X-pipe and new megaphone style pipes.
 

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Well done and welcome. You have done exactly what i am contemplating. Where did you source the sprocket? Direct from the manufacturere? Is it the alloy/steel stealth model?

Cheers.
 

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There has been a lot of discussion on here of people changing out rear sprockets to 39T or 40T. I changed my stock one to a 39T and no longer even notice the difference (it wasn't much difference in rpm/x mph anyway). Does make the bike feel slightly less overgeared. I think I got mine from Supersprox too. Also, with stock gearing the axle seemed near the end of its adjustment range - not positive of that, however.
 

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… Also, with stock gearing the axle seemed near the end of its adjustment range - not positive of that, however.
I just had the rear wheel off of my '16 T120 to replace the tire. I have the stock chain and sprockets. Chain tension has needed adjusting only one other time before since the bike was new. This was one flat at the 500 mile service. I adjusted it out one more flat this time. That's two flats total.

The adjuster plates come off when the axle is removed. I found that I still have a good 1/4" or more available chain adjustment. Taking a single flat each time, that's many years of adjustment. I'll need a chain and sprockets before there's no more adjustment available.

You don't even lose your chain adjustment when the rear wheel is removed. The adjuster bolts and lock nuts are easier to get at, too.
 

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Discussion Starter #7
new seat

At the same time that I put on the new 40-tooth rear sprocket, I installed a new seat. As I mentioned above, my goal was to raise my seat height to provide more legroom. I purchased the seat from British Customs using their 20% off deal.

It turned out great! The new seat is about 1" taller and quite a bit firmer. Here are some pics to compare the stock seat with the "Slammer" seat. I removed a bunch of chrome tubing at the rear of the old seat that came with the bike.

Next week I am installing an X-pipe (TEC Bike Parts). I am looking forward to the new sound/noise...thump..thump! In preparation, I ordered a new set of Torx bit including a T-55 for the big frame bolt! I've watched a couple of YouTube videos for guidance.

Bruce
 

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At the same time that I put on the new 40-tooth rear sprocket, I installed a new seat. As I mentioned above, my goal was to raise my seat height to provide more legroom. I purchased the seat from British Customs using their 20% off deal.

It turned out great! The new seat is about 1" taller and quite a bit firmer. Here are some pics to compare the stock seat with the "Slammer" seat. I removed a bunch of chrome tubing at the rear of the old seat that came with the bike.

Next week I am installing an X-pipe (TEC Bike Parts). I am looking forward to the new sound/noise...thump..thump! In preparation, I ordered a new set of Torx bit including a T-55 for the big frame bolt! I've watched a couple of YouTube videos for guidance.

Bruce
Sounds like you a have a plan. Personally I think the Meerkat x pipes looks, sounds and performs better. Here is a link from a run I did month ago with the Meerkat. The Gopro doesn't pick it well but with some headphones you get a better prospective.

 

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Discussion Starter #11
How much longer is the new seat.
In response to your question AJ, according to my measurements, the original mgf seat on my 2018 T120 (pictured above in this thread) is 28.5" long.
My new British Customs Slammer seat 27.75" long.

The Slammer seat is 3/4" shorter (in length front to back).

Bruce
 

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In response to your question AJ, according to my measurements, the original mgf seat on my 2018 T120 (pictured above in this thread) is 28.5" long.
My new British Customs Slammer seat 27.75" long.
The Slammer seat is 3/4" shorter (in length front to back).
Bruce
From those photos, the new BC seat appears longer. but per the above actually isn't. I am guessing you removed your chrome grab handle for personal preference not because it wouldn't fit back on with the new seat, do I have that right? Thanks.
 

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Discussion Starter #13
The Slammer seat may look longer in the photo but the picture is distorted by the camera lens. The Slammer seat is shorter by 3/4". I removed the grab handles because the seat installation instructions provided by British Customs said they had to be removed to fit the new seat. It also says that in the advertisement on BC's website. But now that I think about it, I am not absolutely sure that it is correct since I didn't try it. In any event, I like the look without the added chrome pieces.
 
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