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Twins Technical Talk Technical Talk for Hinckley Triumph Twins: Bonneville, T100, Speedmaster, America, Thruxton, and Scrambler.

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Old 11-08-2012, 08:13 AM   #1 (permalink)
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Scrambler sidecar gearing

I recently collected my scrambler sidecar outfit from Watsonian. On my way home the bike happily cruised at 75/80 MPH on the motorway. I'd like to be able to keep this as a comfortable top end speed, but find the gearing too high in the lower gears. The Scrambler is on standard gearing. What sprocket changes would reduce my tall gearing without ruining the ability to cruise comfortably at motorway speeds?. I'd like to try and get it right first time as money is tight at the moment.

Thanks

Rob
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Old 11-08-2012, 08:48 AM   #2 (permalink)
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Go down a tooth on front. That shouldn't hurt your cruising speed and will cost next to nothing.
Other than that, anything you do is going to be a compromise one degree or another.
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Old 11-09-2012, 08:20 AM   #3 (permalink)
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if you go down 1 tooth on the front your rpm should rise about 600 at 70 mph
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Old 11-09-2012, 08:32 AM   #4 (permalink)
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You can't have your cake and cruise at low rev's too. Any gain it bottom end will be felt as a loss (more rpm at a given speed) at the top.

Just remember that a single tooth change on the smaller, front sprocket will make a bigger difference than a single tooth on the rear. Front sprockets are considerably cheaper to swap out and don't require removing the rear wheel entirely. You can muck around with ratios for $20 a sprocket.

I personally run one tooth smaller on the front and stock rear because I mostly ride around the city and like the more punchy feel off the lights. (and sometimes like to light up the back wheel when it's wet) but do find she sings a little sharp on the highway at 110kmph. Interestingly it hasn't significantly increased my fuel consumption even on long h'way runs.


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Old 11-09-2012, 08:44 AM   #5 (permalink)
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Quote:
Originally Posted by timpee77 View Post
You can't have your cake and cruise at low rev's too. Any gain it bottom end will be felt as a loss (more rpm at a given speed) at the top.

Just remember that a single tooth change on the smaller, front sprocket will make a bigger difference than a single tooth on the rear. Front sprockets are considerably cheaper to swap out and don't require removing the rear wheel entirely. You can muck around with ratios for $20 a sprocket.

I personally run one tooth smaller on the front and stock rear because I mostly ride around the city and like the more punchy feel off the lights. (and sometimes like to light up the back wheel when it's wet) but do find she sings a little sharp on the highway at 110kmph. Interestingly it hasn't significantly increased my fuel consumption even on long h'way runs.


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Interesing you haven't noticed a drop in economy?
I've been debating dropping mine one tooth, even have the sprocket ready to go.
I was running a LeoVince and felt a rise on RPM on the hwy made it even more ear splitting.
Last week I went back to stock exhaust, maybe now is the time to swich out the sprocket.
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Old 11-10-2012, 12:33 AM   #6 (permalink)
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i was quite surprised but probably shouldn't have been because i had a similar experience when i added an extra tooth to my old XTZ660 before i set off around Oz. i was doing it with the express intent to reduce my fuel consumption and was interested to see if it would up the top speed of the bike too. if it made a difference to fuel use, it wasn't one i could pick from the normal variation you get depending on what type of riding you do and more interestingly, it didn't alter the bike's top speed of 165* either. she just sat at slightly lower rev's at the same top speed. perhaps wind resistance is more important at higher speeds?

*all high-speed tests were performed under controlled conditions on suitable private roads.
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Old 11-12-2012, 04:02 PM   #7 (permalink)
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I have nothing to add but would love to see some pics of your rig! A scrambler with a sidecar sounds awesome!
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Old 11-12-2012, 06:21 PM   #8 (permalink)
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scram with sidecar...........
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Old 11-12-2012, 08:07 PM   #9 (permalink)
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Those Watsonians are beautiful I went for a 16 tooth front on my Bonnie/Dmc rig.I don't ride fast so I've not noticed a loss of top end speed. The extra tooth makes it easier on the clutch when starting on a hill. The chain adjusters took up the extra slack so going back is easy.I'd say do it.
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Old 11-12-2012, 11:48 PM   #10 (permalink)
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Steering?

Hi -

It doesn't appear as if you have made any modifications to your forks or triple tree. True? If so, is it not difficult to steer? Have you considered doing so? Thanks.
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