Sprocket size choices.....does it make a diffrence?

[Jonny Hotnuts]

Someone told me it was better, as in easier on the drive, if you were to use the largest countershaft sprocket and achieve gearing by your primary drive. This person said that it was needed to keep chains from breaking.


For instance:

17-35=[2.06] makes almost identical gearing to 19-39=[2.05]. While the gearing is basically the same this person told me that it was better to run the bigger sprockets....even thought I cant understand why this would have any affect. The HP/torque of the motor is the same, the drive speed will be the same and the same resistance forces at a wall speed are the same.

So was this person crazy or is there some merit to the statements that I dont get?

[Sumner]

Someone told me it was better, as in easier on the drive, if you were to use the largest countershaft sprocket and achieve gearing by your primary drive. This person said that it was needed to keep chains from breaking.


For instance:

17-35=[2.06] makes almost identical gearing to 19-39=[2.05]. While the gearing is basically the same this person told me that it was better to run the bigger sprockets....even thought I cant understand why this would have any affect. The HP/torque of the motor is the same, the drive speed will be the same and the same resistance forces at a wall speed are the same.

So was this person crazy or is there some merit to the statements that I dont get?

I can't see too much difference with your 17 vs. 19 tooth primary sprocket, but if you geared it the same with say a 12 tooth vs. a 17 tooth then the chain going around the 12 tooth is not as good a deal as it is turning around a smaller radius.

I just know from my motorcycle days you wore the chain out faster with a smaller front sprocket.

I'll be interested in others thoughts on this also,

Sum

[generatorshovel]

Larger c/s sprockets definitely make the chain life better , it's the whip around the radius that's hard on chains, but as for saving on chain breakages, but if you are that close to your chains breaking point, investing in a stronger chain would make more sense than changing sprocket sizes , after all , LSR is not about getting another 1000 miles out of a chain ? 
Tiny

[Jonny Hotnuts]

The fact that a larger sprocket combo increases radius making the chain links pivot less could be a factor in how much heat it builds. I will bet this is the basis of what the reasoning was and not the stress load on the chain itself.

As far as chains go I am using the D.I.D. X-ring 530 ZVM2. I have used the EKZZZ 530 and have had good luck with all the quality chains….and as far as mileage…..here is last years chain (and an expensive chain to boot) with only about 25 miles on it!

[Jonny Hotnuts]

Also how much would I expect the diameter of a 22" tire to grow at speed, a little off topic but I am trying to figure out gearing. I assume that a 22" tire will grow about .5" at speed.

[hawkwind]

hey hotnuts excellent chain maintenance  I use tsubaki 530 HQR non oring chain on my turbo bikes, busa is running  a 20T front ,35T rear  with TTS 12% overdrive 5trh and 6th , , the master links recieve a dab of silicone (after cleaning with acetone)  no problems to date ,and because Im a run on the smell of an oily rag racer    here are my secret chain maintance tips ,after a hard week on the salt I try to dismantle /clean the bike as soon as possible to counter the effects of salt corrosion , 1. remove chain and place in a solvent bath , clean thoughly ,remove ,drain & dry , move chain to kitchen sink ,wash with hot soapy water ,dry ,inspect chain for any damage ,if ok place in a container of engine oil and seal ,leave untill required again , to prepair for the bike again ,,remove chain from oil and allow to drain for 24 hours (this removes most of the excess oil ) wipe clean and inspect for any rust / corrosion ,I use a white lithium grease to lube the chain with , it comes in a solvent base and is like water ,place chain in a container of lube and agitate chain ,this allows the lube to access all the links ,rollers etc , remove chain and allow solvents to flash off , chain is now coated with a thin thick coating of lube , it does not fling off easly , chain iis ready to be used again 

[Jonny Hotnuts]

hawkwind, you mean the chain I have in the pic isnt suitable for use this year....I figured with a little wd-40......

[Sumner]

hawkwind, you mean the chain I have in the pic isnt suitable for use this year....I figured with a little wd-40......

........ it looked good to me, it fact I was going to ask if you would consider selling it to me since it had history and that might help my car.

Hawkwind great info, I'll save that, thanks,

Sum

[Rex Schimmer]

Jonny,
Going to a larger sprocket will actually reduce the tension load on the chain. If you think about it, torque is force X lever arm, so if your engine make 100 lb-ft of torque and the sprocket has a diameter of two feet, i.e. radius is 1 foot then the chain would have 100 lbs of tension at your maximum engine torque. If you went to a sprocket that is 1 foot in diameter, radius = 1/2 foot then the chain tension would be 200 lbs. So going with the largest countershaft sprocket does reduce the tension on the chain. Looking at the difference between a 17 tooth sprocket and an 19 the tension reduction would be about 18%.

As posted previously reducing the radius that the chain has to go around is probably the biggest advantage of the larger sprocket.

Rex

[V8Pinto]

hey hotnuts excellent chain maintenance  I use tsubaki 530 HQR non oring chain on my turbo bikes, busa is running  a 20T front ,35T rear  with TTS 12% overdrive 5trh and 6th , , the master links recieve a dab of silicone (after cleaning with acetone)  no problems to date ,and because Im a run on the smell of an oily rag racer    here are my secret chain maintance tips ,after a hard week on the salt I try to dismantle /clean the bike as soon as possible to counter the effects of salt corrosion , 1. remove chain and place in a solvent bath , clean thoughly ,remove ,drain & dry , move chain to kitchen sink ,wash with hot soapy water ,dry ,inspect chain for any damage ,if ok place in a container of engine oil and seal ,leave untill required again ,

Hawkwind,
Do you run a master link?  Or do you break/re-rivet the chain every time?

[Dr Goggles]

Rex wins the six pack

[Dean Los Angeles]

Does anybody use an onboard chain oiler? At the speed of the chain and the length of the run it certainly makes sense. I raced karts in the 70's and the race was an hour and a chain oiler was the only was to make the chain last. Of course the oil went right on the track. You would have to make a cover for the chain to collect the oil.

Rex! Excellent answer.

[V8Pinto]

Does anybody use an onboard chain oiler? At the speed of the chain and the length of the run it certainly makes sense. I raced karts in the 70's and the race was an hour and a chain oiler was the only was to make the chain last. Of course the oil went right on the track. You would have to make a cover for the chain to collect the oil.

Rex! Excellent answer.

This reminds me of an old Bultaco...  Sr. Bulto had the right idea!

[Stainless1]

Does anybody use an onboard chain oiler?

3 of my old HDs have auto chain oiling, I think 1 of them is intentional... 

[hitz]

Jonny,
Going to a larger sprocket will actually reduce the tension load on the chain. If you think about it, torque is force X lever arm, so if your engine make 100 lb-ft of torque and the sprocket has a diameter of two feet, i.e. radius is 1 foot then the chain would have 100 lbs of tension at your maximum engine torque. If you went to a sprocket that is 1 foot in diameter, radius = 1/2 foot then the chain tension would be 200 lbs. So going with the largest countershaft sprocket does reduce the tension on the chain. Looking at the difference between a 17 tooth sprocket and an 19 the tension reduction would be about 18%.

As posted previously reducing the radius that the chain has to go around is probably the biggest advantage of the larger sprocket.
Rex

Rex,
 I always your posts carefully, so I can learn as much as I can. If you reduce the radius doesn't that make the sprocket smaller? Maybe at speed week I can have one of those beers. Make mine O'Douls.
 Nothing was said in this thread about the transmission shifting better when it was turning faster, which a large primary sprocket provides. Maybe that was only in the old days?

 Looking forward to seeing you Speed Week if I can make it.

Harvey