15T vs. 16T front sprocket w/ 130/90/17 rear for freeway?

[Leadberry]

So, I do a lot of freeway riding.  Nothing really major, but I commute about 15 miles to work, and I live in an urban area so I pretty much take the interstate to get to school or anywhere else around town.  I'm about to replace the horribly stretched, kinked chain (which the PO clearly didn't maintain) and sprockets.  The bike has a 130/90/17 rear tire (bought it that way), and I do most of my riding at an indicated 80-90 mph.

With the big rear tire the bike does feel like a bit of a bus starting from a stop, but it also feels like it's screaming at 90mph on the interstate.  I bought a 15T front sprocket to kind of counteract the oversized rear tire, but now I'm wondering if I shouldn't stick with a 16T given the speeds I ride at.  Thoughts?  Thanks in advance guys. 

[Golly]

Ive just gone the 15/39 rear option.. In Oz the front cost me 15 and rear 25 just waiting on the rear on backorder. Hope that combo is good for freeway riding as that will be my main route of travel to work also.

Sent from my GT-I9210T using Tapatalk 2

[JAS6377]

I put a 17T on mine... But I also have a full exhaust, pods, DIY timing advance, and a rejet. So, I've got the power to spare. It rolls at 5000 RPM at around 70-75.

I'm also kind of paranoid about high RPM on the highway during the summer. I overheated once going to Maryland. It sucked lol.

[gsJack]

16Tx24.2/26.2= 14.8T

A 15T front sprocket would bring you back to stock engine speeds which is where I like mine.  Actually I've been changing back and forth between 15T and 16T lately to keep mine at or close to stock engine speeds:

http://www.gs500.net/gallery/data/500/GSbrakechainlog.jpg

[gsJack]

By the way, I ran my 97 GS with 15/39T for 40k miles including a number of 400-500 mile interstate days at 70-80 mph indicated.  I don't mind my engine singing to me as we go telling me she is OK.     See link above.

Rev:  Was just checking my tire and my chain/sprocket logs and see I had the 15T sprocket and a 130/90 rear touring tire on my 97 GS for my first trip from NE OH to the Smoky Mtns back in 01 following my son on his GS1100E down I77 and thru the mountains including the Dragon.  Also note I had the Z2/Z4 radial tire combo on before the trips to the Smokies and to the mtns of upstate NY the following year.   

[Janx101]

I put a 17T on mine... But I also have a full exhaust, pods, DIY timing advance, and a rejet. So, I've got the power to spare. It rolls at 5000 RPM at around 70-75.

I'm also kind of paranoid about high RPM on the highway during the summer. I overheated once going to Maryland. It sucked lol.

out of interest .. how much of a power gain do you have with the mods? ... and have the mods changed the 'location' of the power in the rev range? 

[JAS6377]

As far as I can tell, it's midrange and up. It really picks up at around 4500. I think I'm running a bit rich, though. It's most definitely snappier than stock with the pods and exhaust alone. The timing advance didn't seem to boost power TOO much for me. I only did 3.5-4°. It does seem to help the throttle response, though.

Edit: If you're looking for actual numbers, I'm not quite sure. I'm too poor to afford dyno time lol.

[Janx101]

Cool ... Not dyno numbers per se... If they were available then sweet but perception by rider alone is good enough for the now ... I'm needing to do my chain and sprockets soon ... And probably going to try a 18/37 or 18/36 perhaps ... So mainly interested in the differences of the power from stock .... It's fairly standard perception that any engine mods are not going to yield a massive amount more power .. And certainly not turn it into a rival for a gix 600 even ....

The use-ability of what power changes there are ... is my focus ..

Eg .. On my little turbo diesel ute ... Which is a 2.5 4cyl .... I could change the turbo and intercooler setup on it... Without going crazy ... And yield maybe another 10-12% power without completely destroying the more or less constant fuel consumption rate ... But the current turbo 'boost' kicks in at 2000rpm .. Like a lightswitch .. Below 2k it's just not there! And by 4500 rpm is pretty much out of boost ... By putting a slightly fatter section turbo on it and re piping the intercooler ... I could get a more gradual boost 'fade in' from 1500 rpm and fade out from 4-4.5k ... Almost introducing a fuzzy lag effect ... To gain a total jump from 86kw to about 94kw .. (Mates ute dynoed) .. But driving both of them ... If I get motivated and do everything just right I can still keep pace with him mostly ... However as his turbo starts to fade from 4k I can 'almost pull away' and take the lead! ..... Which looks hell funny ... 2 little diesel work utes 'drag racing' on the freeway ... Errrr ... Sanctioned drag strip!! ... While there was a lineup of v6 and v8 traffic behind us waiting to get past  .... His ute in city traffic though is just easier to get going and less drama overall ...

So how what power is available gets delivered interests me ...


But ... As this is a sprocket thread ... And I hijack too many as it is ...

Did you ride with the 17 tooth before the engine work ??  .. I don't see mention of changing the rear so assume that is stock ...

And whether before or after ... 17t ... Changes things ... But I'm thinking that the gearbox with 6 cogs still gives you all available options for gearing vs speed anyway ... I mean .. Seem will say that it's now turned into a freeway cruiser ... And not good for twisty bits ... But I see it as you change gears anyway! ... So change gear in the twisty bits! ... If you get my thinking.

[gsJack]

Intake, exhaust, and jetting mods will give you a 10% HP increase at best starting a bit at mid range but most noticeable on the top end where near full power keeps going close to 11k redline compared to a typical stock curve showing fast power drop off after 8500 rpm peak.





V&H modified a GS making these changes years ago plus some porting and ignition timing work and with a Wiseco 555cc piston change also claimed only a 10% increase in power and torque, limited performance figures showed changes mostly on top end:

http://www.gs500.net/gallery/data/500/GS500tests.jpg

[JAS6377]

...

Did you ride with the 17 tooth before the engine work ??  .. I don't see mention of changing the rear so assume that is stock ...

And whether before or after ... 17t ... Changes things ... But I'm thinking that the gearbox with 6 cogs still gives you all available options for gearing vs speed anyway ... I mean .. Seem will say that it's now turned into a freeway cruiser ... And not good for twisty bits ... But I see it as you change gears anyway! ... So change gear in the twisty bits! ... If you get my thinking.

I actually switched it out from the stock 16T after I did the engine work. I mentioned a little bit above, but I was riding to Maryland on an extremely hot day, and the bike overheated on the highway (I was running lean, and was constantly at around 6200-6500). I decided to richen the mixture a bit, and slap on the 17T front sprocket to bring the revs down. As for the twisties, it's still just as fun. You just have to keep the revs slightly higher (I try for around 6-8k) to allow for engine braking and throttle response.

I can *almost* keep up with my buddy in his CBR600, if he holds back a bit lol.

[Watevaman]

 I can tell you right now I'm considering jumping up to a 17T front versus the 15T I have on now after riding the highway for a bit more than two and a half hours the other day. I was cruising along at 80 or so in 6th and running a constant 7k. Hated it and want to bring that down as much as I can.

[Leadberry]

By the way, I ran my 97 GS with 15/39T for 40k miles including a number of 400-500 mile interstate days at 70-80 mph indicated.  I don't mind my engine singing to me as we go telling me she is OK.     See link above.

Rev:  Was just checking my tire and my chain/sprocket logs and see I had the 15T sprocket and a 130/90 rear touring tire on my 97 GS for my first trip from NE OH to the Smoky Mtns back in 01 following my son on his GS1100E down I77 and thru the mountains including the Dragon.  Also note I had the Z2/Z4 radial tire combo on before the trips to the Smokies and to the mtns of upstate NY the following year.   

Thanks for the input!  I'll give the 15T a shot.

[Leadberry]

I can tell you right now I'm considering jumping up to a 17T front versus the 15T I have on now after riding the highway for a bit more than two and a half hours the other day. I was cruising along at 80 or so in 6th and running a constant 7k. Hated it and want to bring that down as much as I can.

Yeah, while I do a lot of highway riding, the around-town riding is all stop and go, steep hills, pedestrians walking right out in front of you, bus stopping in the middle of the road, etc.  I think a 17T would be too much with the 90-series rear tire (at least in my case).