Sprocket ratios and chain lengths for trackdays

[steve929rry]

The Gen4 has standard front/rear sprocket of 17/45 with 120 links in the chain ( PS: I noticed a few places where 118 links is quoted as standard including chaincommander.com - ignore this it is wrong, I counted them)

Those in the know on this forum say the best combination for trackdays on the Gen4 is 16/43 as it gives a small reduction in gearing with better stability and less tendency to wheelie due to the longer swingarm or wheelbase. According to chaincommander.com 16/43 with the standard 120 link chain will give a 12.2 mm effective increase in swinging arm length and in combination with a 122 link chain you would get a 28.1 mm increase in swingarm and 124 links would give 44.1 mm but be careful as this may be too long for standard swinging arm.

As most club racers would change both chain and sprockets together for 520's, when you use 16/43 final drive do you use standard 120 links or 122 link chain and is 124 links going too far (I noticed Alpha Racing sell a 124 link chain as the "superbike racing chain" but presumably you would expect SBK boys to use a longer swinging arm)?

Measuring my bike's remaining slot in the standard swingarm it looks like 124 link chain with 16/43 may be just about possible as it gives a 44.1 mm length increase.

Steve

 

[alex]

16/43 w/120 on a 525 chain is best IMO.
However HM Racing fitted a 118 link to mine when it was changed to 16/43. Keeping it nimble!

 

[WoKe]

Distance between swingarm mountingpoint and rear axle must be between 605mm and 617mm ;-)

 

[steve929rry]

Thanks for the comments and apologies for the mistake in quoting chaincommander.com it should have been gearingcommander.com - useful calculating tool.

The reasons I was looking for comments and considering increasing the chain length is as follows:
- I believe one of the main geometry differences between the Gen3 and the Gen4 is the underswung swinging arm design which allows for a longer swinging arm and wheelbase. The wheelbase increased from 1425mm to 1441 mm (HP4 Race is 1440mm).
- The standard chain is 120 Links. Alpha racing sell two race chains, one a 520/120L the other a 520/124L WSBK version so it appears the WSBK's have a still longer swinging arm and use a 124 link chain.

It appears from the above that increasing the effective swinging arm length can be an advantage on track but obviously only up to a point as you would not want to make the bike more difficult to turn.

I measured the distance between my swingarm mounting point and rear axle as 604mm with a tight chain and all standard, as the slot in the swinging arm allows for a further 42mm of travel I wondered whether it was worth trying to fit a 124 link chain if there were any known benefits. However, that's probably "a bridge too far" with normal road bike parts so I will stick with 16/43 and 120 links for the time being which would increase the distance between sprocket and rear axle by 12.2 mm. If I notice any improvement in stability at Brno in a couple of weeks I might consider a future increase to 122 links (+28mm over standard).

Cheers,

Steve

 

[alex]

Wsbk have Suter swingarms so maybe be longer. Thus a 124 may not fit an oem gen4. I'd stick with 16/43 120 for now and see how it goes.

- Alex

 

[GavD101]

Hopefully this doesn't seem like a thread hijack. But as we are talking about gearing/chains. Is it worth doing a 520 conversion on a Gen 4? My bike is split between 60/40 track and road. (More track)

 

[alex]

Hopefully this doesn't seem like a thread hijack. But as we are talking about gearing/chains. Is it worth doing a 520 conversion on a Gen 4? My bike is split between 60/40 track and road. (More track)

Main benefit appears to be more choice on sprockets. The weight argument is a bit silly with 200+bhp.
I'll probably do it on my next bike..but it will be track only.

 

[fast_ryan]

520 Conversion

Is it worth doing a 520 conversion on a Gen 4? My bike is split between 60/40 track and road. (More track)

520 pitch chain and sprockets are really only best used on track/race bikes. The main benefit is there is a much wider range of 520 pitch sprocket sizes available for use with aftermarket forged wheels. They also offer a marginal reduction in unsprung weight (but to the detriment of longevity). In truth the small reduction in mass is only really useful if your trying to build a race bike to a minimum specified weight.

If your bike is used on the road, with the occasional trackday, then your best off sticking with a 525 pitch chain and sprockets for longevity. If your doing a lot of trackdays and are routinely altering gearing then a 520 pitch chain and a selection of sprockets is the way to go.

 

[Corkgsxr]

One of the top sbk riders on my track runs a swingarm extender on his R1. So maybe drive is more important than loss of turning

 

[alex]

One of the top sbk riders on my track runs a swingarm extender on his R1. So maybe drive is more important than loss of turning

They do say litre bikes should be stopped turned and fired out...

- Alex

 

[Corkgsxr]

Buddy of mine had Glenn Irwin follow him for a few laps. Was ment to give him tips. This fella was high in sbk cup championship.

Got told your style is for a twin. Too much corner speed. Change your style completely or I can't help you.

 

[GavD101]

Re: 520 Conversion

Good advice. At the moment it is staying on the road for the foreseeable future.