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2018 Bobber Black
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Discussion Starter · #1 ·
Ok maybe not first but definitely right after shorter fenders (which should be first).

So today I got a chance to install the 39t rear sprocket with keeping the 17t up front, then got out for a 35mile mostly backroad ride to break it in. By time I got to my mid ride stop (video will be out Sunday), my mind was blown by what all that small change made!
1. Main reason for me doing this was to get the line of the tread/sidewall on the tire to be perfectly aligned with the edge of the short OEM fender, yes for looks. Now it's within 1-2mm! PS I actually measure.
2. It made the 1st & 2nd gear bong around town go away about 80% or more. Also the 25mph (40ish kph) most neighborhoods speed limit isn't a annoying in between 2-3 gear.
3. With just installing it with the factory length chain it moved the rear wheel up 8mm, which I was expecting the wheel base to be shorter. But I didn't expect it to make as big of a difference as it did on the lean angle. Guessing maybe like 2 degrees, I dont know what it actually is now but it is 100% noticeable.
4. By far the biggest surprise to me is the stock rear shock ride quality with being 6'1, about 200lbs without gear (seat is redrilled 23mm back). The route I took there are normally two bumps it bottoms out on, as well as just knowing how the bike normally reacts on this loop. It didn't bottom out in either spot, with the overall loop being much smoother. My guess is with the rear wheel being 8mm further forwards makes a pretty drastic difference in leverage at the wishbone for the rear shock. If I didn't have a new rear shock to install already (thank you Psychopasta), I probably wouldn't even bother with it anymore.

Thank you for taking the time to read this. Honestly think this is more worth it than exhaust when considering first few modifications for the Bobber.
Video version of this will be out Sunday but couldn't wait to share.
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Interesting, thanks Atopper, I think I might try this - I remember when I changed the sprockets on my hard tail Bonneville it increased the wheel base by about 15mm. Doesn't sound a lot but it completely changed the look and handling of the bike (both for the worse), it wasn't long before I changed it back.
 

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I appreciate the detailed review. Great read.

Looking forward to seeing your video. I assume that it will be ride focused but I would also be very interested in seeing a how-to video. Even more so if you ever do the front sprocket.
 

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2018 Bobber Black
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Discussion Starter · #6 ·
I appreciate the detailed review. Great read.

Looking forward to seeing your video. I assume that it will be ride focused but I would also be very interested in seeing a how-to video. Even more so if you ever do the front sprocket.
Working on the edit now. I tried to film a how to but unfortunately my garage setup is not great for filming(a lot of junk that鈥檚 not mine) but if the clips don鈥檛 make it into the edit of sundays video, there will be a how to on Wednesday. When ever I need to replace the chain and front sprocket I will try to get that filmed too. 馃憤
 

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2020 Bobber Black
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I did a similar mod on my original Trophy 1200 back in 1999 to raise the RPM in every gear (my fuel economy suffered slightly). It made the bike feel much torquier and no more 'tweener gears at low speed. Fortunately now I'm such a huge load on the Bobber I haven't had to resort to making a gearing change necessary, it happily hauls my fat ass in about any gear.
 
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Put a 40t rear on after reading this thread. As suggested elsewhere had to change the nylon washers for steel ones just to get that little extra slack to align the wheel satisfactorily. Not tried it yet, still too cold and wet, but certainly looks the part..



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Little things鈥︹hanged the bolt for something shorter whilst at the same time making it easier to adjust and allowing the original nylon washer to be used to protect the frame. The original plan was to use some spare black titanium bolts but then realised the thread pitch was wrong.
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