Thanks! Good point. I am going my LBS today to get a new chain and front sprocket (12k miles). If nothing else, I will feel better about protecting the engine case with all new parts. I really want to add the 17 on front, but I just don't want the chain that close to the engine case. I guess as long as it clears it doesn't matter, and if it comes off it doesn't matter either (get out the checkbook). But, that idea will have to grow on me. Thanks again everyone for your comments and advice!
Sprocket change for highway
- Thread starter JCW800
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As a more recent biker than most in this forum ------I always found it odd that our cars turn over at ,say 2200 at 70 ---but our bikes need to be about twice that. Yes , I know its all about the horses etc. but it does feel odd. In the light of this, 5000 at 70 doesn't sound bad ---both my old Honda CBF1000 and Kawasaki versys were running 6000 at 70. I too am looking at my T120 with a view to re-gearing ---I guess we all have a common goal of making the bike fit our needs as far as possible, for me I should have bought the speed-twin BUT have had to compromise because my wife wants to join in on the occasional ride-out. Don't get me wrong the T120 is lovely and I am fortunate to own it but it is very over geared! as some have noted 6th gear is designed (in this instance) for easy cruising---pretty much what the bike is aimed at. When out with my riding buds --I need to change down to 3rd! to make the fast overtakes that Scottish roads demand , 3rd covers from 30-85 which surprisingly keeps up with the leader who is mounted on a Kawasaki sx1000, (albeit in this limited range). It is not ideal however , having to jump all over the gearbox on a bike designed to cruise! ----SO I am looking at a different rear sprocket. Several owners have changed to a 39T rear as it fits without changing the chain etc. and some have done the research using the gearing charts which are available ---these charts suggest that this gearing matches the bikes power/torque best. I contacted JTS one of many companies who make them but are only available through dealers. These are high quality steel items ----so I don't know how much they cost yet. JTS DID however supply a gearing comparison chart-----the 39T lowers the gearing by a tad over 5%. Doesn't sound much but some report that they feel the difference ----one contributor has fitted one but not been on a long ride yet so maybe will wait until he reports. Certainly at the moment the T120 is tricky at road junction and traffic jam speeds as 1st is too high. So it may make the bike more 'comfortable' overall----but I am reticent to maybe lose the single gear overtake ability that I have presently hmmmmm. choices, choices.
2bazookas
Member
I was curious to see how much difference the sprocket change would make. So, I have started with the front sprocket. I pulled the 16T and installed a JTF52-17RB. I took some before and after pictures of the RPM's at various speeds to compare the difference. There is a slight difference in the RPM's. Where I notice it mostly is in first gear. When doing sharp u turns I need to feather the clutch a little more and when I am taking off from a stop light on a flat road I use first gear now instead of second. It doesn't seem to wind up as quick with the 17T sprocket. Longer legs, if you will, but it is subtle.
16T/25 mph = 2500 rpm/3rd gear
17T/25 mph = 2400 rpm/3rd gear
16T/40 mph = 3400 rpm/4th gear
17T/40 mph = 3200 rpm/4th gear
16T/55 mph = 3900 rpm/6th gear
17T/55 mph = 3600 rpm/6th gear
16T/70 mph = 4900 rpm/6th gear
17T/70 mph = 4700 rpm/6th gear
I am ok with this change. I'm not sure if I want to go a step further with a 47T vs 50T rear sprocket. It would be nice if someone that has done this change could give us some data comparisons to reference. I watched this video on u tube and found it informative. Front & Rear Sprocket change
16T/25 mph = 2500 rpm/3rd gear
17T/25 mph = 2400 rpm/3rd gear
16T/40 mph = 3400 rpm/4th gear
17T/40 mph = 3200 rpm/4th gear
16T/55 mph = 3900 rpm/6th gear
17T/55 mph = 3600 rpm/6th gear
16T/70 mph = 4900 rpm/6th gear
17T/70 mph = 4700 rpm/6th gear
I am ok with this change. I'm not sure if I want to go a step further with a 47T vs 50T rear sprocket. It would be nice if someone that has done this change could give us some data comparisons to reference. I watched this video on u tube and found it informative. Front & Rear Sprocket change
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I made the change to a 47 on the rear, and now I LOVE the Tiger. The gears pull longer and stronger and it’s not screaming at highway speeds. Before it felt so “bottled up” due to the low gearing. Now, it’s free to run. For the haters, leave yours as is. But, I will never go back. Happy New Year! (Yes, I bought a new chain and front sprocket too.)
Another man of action . Glad to hear you enjoy the change and your thoughts are right in line with mine . The next step would be 1 less on the back and from my experience that could easily be to much . Not worth the bother .
In regards to the highest gears having very close ratios is common and required . Overdrive style gearing works on autos , but they are considerably more aerodynamic than a Tiger 800 with hard luggage . My Can Am 250 was fast enough to win an ice racing championship but when geared for the only half mile of the season shifting from 4th to 5th exposed the issue . It took to long to get it up to speed in 5 probably 75 mph or so . It was faster to reverse the gearing and let it scream its poor little guts out for the last part of the straightaway. Next summer the 250 GP engine was in a Champion frame with six speeds from a 175 cc donor engine which hit the trails in the GP chassis .
In regards to the highest gears having very close ratios is common and required . Overdrive style gearing works on autos , but they are considerably more aerodynamic than a Tiger 800 with hard luggage . My Can Am 250 was fast enough to win an ice racing championship but when geared for the only half mile of the season shifting from 4th to 5th exposed the issue . It took to long to get it up to speed in 5 probably 75 mph or so . It was faster to reverse the gearing and let it scream its poor little guts out for the last part of the straightaway. Next summer the 250 GP engine was in a Champion frame with six speeds from a 175 cc donor engine which hit the trails in the GP chassis .
Brooke, I really think 47 was right, unless you were wanting to totally turn in it into a street bike. I cut about 400-500 rpms at 70 mph, so it still runs 4500ish. I did it to cut rpms at 70 mph, but what I love most is more very strong roll on power from a stop. Right after I did it, I took it on the highway and down the entrance ramp in 5th gear I was doing 80 mph before I knew it. As an old enduro rider, it felt like going from a KTM200 to a KTM300. It feels like it has more power, so I don't believe I lost any noticeable torque on the low end. Whatever works..... Thx
Exactly my thoughts . I have not changed gearing on the Thruxton R yet but apparently many have . One in particular is a drag racer who is going quicker with taller gearing . It seems the R pulls so hard in first that it’s difficult to make the 1. 2 shift before hitting the rev limit , which makes perfect sense based on my experience.
Idaho Tiger
Member
My past experience with my Honda 929RR - stock steel sprockets, would contradict that. I had always heard you should change them together, but I went to change out the chain, I bought the new sprockets and after I got the old ones cleaned up, I put one on top of the other and they were identical - no visible wear at all, so I returned them and got my money back. I did 3 chain changes on that bike and got the same mileage out of all 3 chains 16-18K without ever having the change the sprockets. I had a similar experience with my 2 Triumph Sprint 1050 ST's which I was getting 20K per chain and never needed to change the sprockets. Now, I am guessing if you ride in dirt a lot, or don't keep your chain properly lubed, your results may vary... but, I no longer hold to the "new chain must have new sprockets" rule. If a sprocket shows signs of wear, change it. If you doubt your ability to see the wear, buy the new ones, and clean up the old one and compare them and find out before you put install it. If there is no wear, return the new ones and save some money. That said, if you are going with an aluminum rear sprocket to save weight, different story - aluminum wears much faster, especially riding in the dirt.
Very interesting. Way way back in the day when I was changing chains every day the sprockets , more so the front ,would be so misshaped that using them with a new chain created a noisy marriage . The thought was that the sprockets were worn to adjust to the greater pin to pin distance of the chain or the chain had to stretch to suit the worn sprockets . Those were the days before o rings of course . Had tv though . I get close to 40 k kms on the tiger before reaching the recommended pin to pin measurements. Things seem noisy and snatchy as I approach that limit but I am sure it would go another 10 k before some thing bad occurred . My buddy notices the same on his Weestrom . Would be interesting to hear from more experts on this one .
2bazookas
Member
Update: I installed the JTR2014-47 rear sprocket and recorded the rpm's at the same speed and gear as with the front sprocket, as noted above. There's a noticeable, to me, effort to avoid stalling at low speed crawling. A little more feathering of the clutch is required. This works for me. My style of riding is a lot of gravel/dirt roads and highway. Not much technical riding for me at lower speeds.
Mackanigbg
Member
I have changed on my 800 XCx 2018 and now I have 17T front sprocket AND 47T as rear sprocket since I only ride on different sorts of paved roads. I really love how it is now! 
Before I saw no reason to use the gears because even on the smaller roads it wasn´t motivated to shift down since the 6th gear was so low.
When I started on 1st gear I almost felt it could have been 1-3-5-7, e.g the gears are too close and there are a 7th and 8th gear missing
Now I get a good and longer pull on each gear and it´s fun to be able to shift down and accelerate out of a curve and then shift up one or two gears
The speed now is 78 km/h (49 mph) at 3000 rpm and 105 km/h (65 mph) at 4000 rpm.
The conclusion for me is that I have gained much better and more relevant steps between the gears and there always is enough power for me, and also for those who drive on gravel roads because you just drive on one gear (or even two) lower than before, and look at the 6th gear as a 7th highway gear
The only disadvantage is maybe that 1st gear is a little high but on my 2018 it´s a little lower from factory than on previous models so it´s not really a problem for me....
Before I saw no reason to use the gears because even on the smaller roads it wasn´t motivated to shift down since the 6th gear was so low.
When I started on 1st gear I almost felt it could have been 1-3-5-7, e.g the gears are too close and there are a 7th and 8th gear missing
Now I get a good and longer pull on each gear and it´s fun to be able to shift down and accelerate out of a curve and then shift up one or two gears
The speed now is 78 km/h (49 mph) at 3000 rpm and 105 km/h (65 mph) at 4000 rpm.
The conclusion for me is that I have gained much better and more relevant steps between the gears and there always is enough power for me, and also for those who drive on gravel roads because you just drive on one gear (or even two) lower than before, and look at the 6th gear as a 7th highway gear
The only disadvantage is maybe that 1st gear is a little high but on my 2018 it´s a little lower from factory than on previous models so it´s not really a problem for me....
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My Thruxton is getting it’s 17 t installed today along with new chain and stock size rear. The original set is still close to new so will save it all . Not a big change , 6 or 7 percent , only 300 rpm at hiway speeds but after the same change on Tigger , which seems perfect for my riding , going with what I know .
Mackanigbg
Member
In my opinion 300 rpm which the 17T is resulting in, is not worth any effort. I notice many is of the opinion it's worth it but it's up to each person to do what they think is the right level.
It doesn't make any difference worth mentioning...
In my case I guess it has done between 800-1000 rpm
It doesn't make any difference worth mentioning...
In my case I guess it has done between 800-1000 rpm
Sounds like a big change is good for you , enjoy the ride . At my age the next big change could be the
last so treading very lightly. Probably closer to 400 rpm on Tigger , which revs 1500 rpm or so higher than the Thruxton at hiway speed .
last so treading very lightly. Probably closer to 400 rpm on Tigger , which revs 1500 rpm or so higher than the Thruxton at hiway speed .
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I agree with you to a point. However, every little bit helps. And when one is changing sprockets anyway, going to a 17t is simple and cheap. For what you are trying to accomplish, a 17T would not be enough.In my opinion 300 rpm which the 17T is resulting in, is not worth any effort. I notice many is of the opinion it's worth it but it's up to each person to do what they think is the right level.
It doesn't make any difference worth mentioning...
In my case I guess it has done between 800-1000 rpm
Idaho Tiger
Member
Maybe. It totally depends on who you are. If you...
- ride on paved roads exclusively, and...
- keep your chain lubed (don't let the rollers get/stay shiny without giving it another shot of lube), and...
- keep your chain adjusted as needed by checking it every thousand miles or so (more often with an older chain) and change it when it has stretched too much (about every 14-18K depending on the bike and quality of chain - I don't recommend skimping on quality)...
- run hardened a steel (stock of the like) sprocket in front and steel sprocket in back (stock or the like)...
...you DO NOT need to change every time you replace the chain. I had a CBR 929RR - tons of power/weight ratio 150hp at the crank, and I weight 200 lbs, and I went through 3 chains (45K total) and never saw any wear on the sprockets - on the first chain replacement I bought new ones, clean up the old ones and compared, and NO difference one on top of the other - NONE. After that, I visually inspected on each chain replacement - 14-18K miles each, and never any visible wear, and similar experience with my Triumph Sprint ST 1050, and I got just as many miles out of the chains I put on the older (allegedly worn out according to 'word on the street') sprockets as I got on the original sprockets. That is over 5 chain changes on 3 different bikes - a total of over 100K+ miles of experience. But, if you got money to burn, you can't go wrong by changing them.
On the other hand, if you...
- ride a lot on dirt/gravel roads, or...
- don't pay attention to lubing your chain when it needs it (whenever the roller start to turn shiny) or...
- don't adjust/change your chain as needed or...
- run aluminum sprocket(s) - sure, they are lighter, but they wear MUCH faster...
...you will LIKELY need to change your sprockets with your chain regularly (remove and clean your old ones when you go to buy, and compare to be sure).
That is what I found. When I rode dirt bikes off-road exclusively, I always changed the sprockets with the chain.
Idaho Tiger
Member
Sorry to differ, but there is a world of difference between a 250 and an 800. And, a world of difference between racing ('letting it scream') and riding on the highway for comfort and sport. I made the change on my 2018 800XCa on the front sprocket to a 17 tooth (about the same ratio of change as putting 47 on the back), and it really made a noticeable difference in highway comfort at 75 (I wish I could do the 50 -> 47 switch on the rear, too, but I will be riding off-road with it, and at 10mph it already added 6/10 of a mi/hr in first gear, and I don't want to add any more.... If only Triumph had bumped up 5th and 6th more, and saved me the trouble... but alas, it was not to be....
Good information.
My climate is a lot wetter than yours. I do ride in the rain and the water and sand on the roads are not exactly conducive to long life of chains and sprockets. I do clean and lube the chain after riding in the wet. I do ride on unpaved road about 20% of the time. I do not use aluminum sprockets. I regularly clean and lube my chain about every 400 miles. More frequently during rainy season. And I do change sprockets when I replace a chain. My sprockets are definitely worn by then.
My climate is a lot wetter than yours. I do ride in the rain and the water and sand on the roads are not exactly conducive to long life of chains and sprockets. I do clean and lube the chain after riding in the wet. I do ride on unpaved road about 20% of the time. I do not use aluminum sprockets. I regularly clean and lube my chain about every 400 miles. More frequently during rainy season. And I do change sprockets when I replace a chain. My sprockets are definitely worn by then.
Mackanigbg
Member
Here I found an interesting chart where you can get the gear ratio of different sprocket combinations
It also shows that 16t/47t give exactly the same gear ratio as 17t/50t as mentioned in this thread.
It also shows that 16t/47t give exactly the same gear ratio as 17t/50t as mentioned in this thread.
@Mackanigbg Good information. Thank you for posting it. 
