Oversized front sprocket safety?

[Daschicken]

I got all my vehicles together in one picture.


jkv, I have some michelin road 5s already on the way. $312 shipped, and can install at work for free.

Originally Posted by Stubby79

Umm...no.

If you have a 16 tooth sprocket and the output "shaft" it's attached to is spinning at 200rpm, the chain is moving 3200 links per minute. (16x200)

If you have an 18 tooth sprocket spinning at 200rpm, the chain is moving 3600 links per minute. (18x200)

You will, however, be spinning the engine at a slower RPM for the same speed, which is probably what you're thinking.

Didn't bother responding to this until now, but yes, the situation I was referencing was LOWERING output shaft speed, not increasing chain speed for the same output speed by increasing sprocket size. Of course the chain will go faster if you spin a larger output sprocket at the same speed!

I am not using this as an excuse to go 85 mph instead of 70 mph!

[jkv357]

Originally Posted by Daschicken

I got all my vehicles together in one picture.

jkv, I have some michelin road 5s already on the way. $312 shipped, and can install at work for free.

Nice group you have there.

I meant Road 5s - not 4s. Let us know how you like them. My RSs like to be hot but take too long to warm up, so i think the Road 5s would be better for me.

[Michael Moore]

If you look in chain catalogs you'll find that most manufacturers would like 17T to be about the smallest sprocket used. Overly-small sprockets do not make for happy chains.

When you have gearing that is too tall, you are in between your optimal gearing, and it is an inconvenience. When you have shorter gearing and wish for taller gears, they will NEVER be there. You can always shift down(unless you are in 1st..), but no matter how many times I lift up on the shifter there won't be a 7th gear.

You might be surprised at how many racers I've explained that to just don't get it. They keep thinking that if they had "4:11 gears they'd really get lost".

If you get a tail wind with the short gearing your ICE is at risk of over-revving, where with tall gearing you just go faster.

cheers,
Michael

[euromodder]

Originally Posted by Michael Moore

If you get a tail wind with the short gearing your ICE is at risk of over-revving, where with tall gearing you just go faster.

It's how I got the Dwarf up! to 175 kph (speedo almost off the clock in 5th) on GPS while it's officially only rated for 164 kph (in 4th)


The tailwind was a long downhill though

[woodsrat]

Originally Posted by Michael Moore

If you look in chain catalogs you'll find that most manufacturers would like 17T to be about the smallest sprocket used. Overly-small sprockets do not make for happy chains...

Not that anyone here would use one but I had a 10t. sprocket on my Honda Reflex trials bike and I think I have a 9t. sprocket in the garage I bought for a trials-ish Honda C-100 build. These are really hard on the chain and obviously don't last long.

Custom rear sprockets are expensive but I use them all the time on my projects. I get mine from Rebel Gears in Tennessee and their products have been excellent. If you run out of room on the front start dropping three teeth on the rear which will give you the same result as increasing one tooth on the front.

While some motors get better mileage at lower RPM's some bikes actually get better mileage pulling more revs. Some of this may have to do with having to run more throttle to pull the "taller" (lower numerically) gearing.

Gearing is the one factor that's greatly overlooked in the motorcycle world and a relatively inexpensive way to change the way your bike runs. There's a reason serious racers have a bunch of different sprockets in their trailer.

[hotshoetom]

Not sure if this is timely enough to help you as I just saw this post today but I have run a 17 tooth front sprocket on my vstrom for a long time...and it works well provided you are not riding in very hilly terrain or with a passenger. Either one of those scenarios and you will find the gearing in first gear a bit steep making it difficult to pull away from a stop uphill. Especially if you are a big guy like me. At the time I did this I weighed approx 250 so no featherweight rider here. For two up riding or in hilly terrain the best overall combo is the 16 tooth front gear. It reduces revs slightly on the highway over the stock setup and helps fuel economy without hurting torque from a stop too much. That said, if you do a ton of highway riding at speeds under 70 mph, the 17 tooth is a good setup for that. Ridden carefully, I was able to get a tick over 60 mpg on several occasions with that setup. It will suck in town but that is the trade off. Let me know how it goes.

[The Atomic Ass]

I had a V-Strom 650 for a bit, same engine as the SV.

17/41 is perfect. It doesn't like <3k in 5th and 6th, and <2k in 3rd and 4th is pushing a bit, (due to the low cylinder count), but the results speak for themselves: https://ecomodder.com/forum/em-fuel-...vehicleid=9131

[hotshoetom]

very impressive results to be sure...I never did that well probably due to the fact that the bike was hauling around more azz with me on it than with you on it lol. Plus I have a taller windscreen and large givi saddlebags that negatively affect aero in addition to my physical size...I did well to get 60 mpg fairly often with careful riding and keeping speeds under 65 mph. I never dreamed when I bought that bike in 2007 that I would keep it this long...but it has been such a good all rounder that I just cant part with it. And now of course its so old no one else would pay anything much for it.
I found that with the load I had on the bike that anything under 3500 rpm in 5th and 6th the engine didnt like much and in 3rd and 4th gear under 3000 it was unhappy. Even at that it didnt want full load on the engine at 3500 in 6th...you had to be up near 4000 before it seemed happy with full throttle.