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View Full Version : Tried a 42 rear this weekend !!



mille-ryan
10-21-2003, 02:35 PM
Well saturday night in the dark I slapt on a 42 tooth rear sprocket I had still from my old Mille. First off , Aprilia did sum improveing on the carrier bolts, they are now 6mm allen on the back side, so yuo have a good bite surface to torque from, no more slipping off and busting yer freaking nuckles. Bike is much more fun to ride now, not such a big burst of speed after 7grand, pulls a lot better out of corners as well. My chain was plenty streched too, with almost 1000 miles on it, so fit was no prob. I think a 43 would fit in as well, just be real close to the front. So go ahead and do it, its fun, and the old stuff fits just fine :D :D

Italibikefreak
10-21-2003, 04:22 PM
what's the stock gearing on the new bike? It seems like the gearing is to high. Can I go up two in the rear and get better acceleration?

mille-ryan
10-21-2003, 04:35 PM
Dam thing is a 15-40. Thats all I did was 2up.

Thunder Factory
10-21-2003, 08:07 PM
Hey Ryan.

Glad to hear you liked the 42 on the rear. :banana:

Just for reference , stock gearing is 16/40, I know as I tried a 15 on the front and the OE sprocket has 16 stamped on the reverse! :p

mille-ryan
10-21-2003, 08:43 PM
Aha, thanks for the correcto Thunder, have no idea why I said 15 in the first place.

Italibikefreak
10-21-2003, 10:47 PM
Man I think I might go three up in the back that is really a small 40 is kinda small isn't it. That's why my friends RC-51 kinda walked away from me a bit.:rambo:

stinky
10-21-2003, 11:22 PM
I'm going +1 on the rear and -1 on the front.

Thunder Factory
10-22-2003, 12:49 AM
Ryan

I know what you mean about not knowing why you say things at times, happens to me regularly at my age. :p

Concerning the options for gearing. Ryan mentioned that a 43 would possibly ft with a bit of chain stretch and I agree completely. I fitted the 42 and the rear wheel has come forward in the adjusters a bit of course but without some more chain stretch I think the 43 will be on the edge of the adjustment range so will wait another 1000 miles or so before fitting one.

I ran a 15 on the front a couple of weekends ago, and while this is equivelent to going to 43 at the rear and felt good I'm not happy with going small at the front as it will increase wear on the chain.

When playing with the ratios I tried the 15 front and 42 rear and it was way too much from my point of view, but it's all personal choice in the end. :micah: :bond:

bilter
10-22-2003, 04:39 PM
I would just like to point out a technical fact. My intention here is not to appear arrogant but chains do not "stretch" over time. The reason they lengthen is that the bushings that the pins go through wear. This allows more free play between the bushing and the pin causing the chain to have more space between links. Now if only I could improve my spelling!

Thunder Factory
10-23-2003, 12:28 AM
Originally posted by bilter
I would just like to point out a technical fact. My intention here is not to appear arrogant but chains do not "stretch" over time. The reason they lengthen is that the bushings that the pins go through wear. This allows more free play between the bushing and the pin causing the chain to have more space between links. Now if only I could improve my spelling!

Always good to know he technical points, I was using "stretch" as a description of the chain getting longer, rather than meaning the components were physically changing like a rubber band.

Matt
10-23-2003, 03:23 AM
Is the stock gearing 16/40? That would make a ratio of .40 (or is it 2.50?)

Would it not be better for the chain life to have 16/41, 42 or 43 which give a nice, almost infinite decimal of a gear ratio...or does it not make any difference? I have tried to avoid too even ratios.

Matt

Thunder Factory
10-23-2003, 03:36 AM
Originally posted by Matt
Is the stock gearing 16/40? That would make a ratio of .40 (or is it 2.50?)

Would it not be better for the chain life to have 16/41, 42 or 43 which give a nice, almost infinite decimal of a gear ratio...or does it not make any difference? I have tried to avoid too even ratios.

Matt

Stock is 16/40 which is a ratio of 2.500.

Don't know the situation regarding the decimal bit, I prefer adding to the rear instead of removing at the front as I believe it's better for chain wear.

Just for information and to save people working it out the ratios for different combinations are:

15/40 2.667
16/40 2.500
16/41 2.563
16/42 2.625
16/43 2.688
16/44 2.750

Finally 15/42 which I tried as an experiment and quickly removed :asshole: 2.800

Matt
10-23-2003, 04:56 AM
I quite agree, Thunder. I went one smaller in the front (on my Duc) and the most noticealbe change was a new vibration at low speeds. Too early to say whether the chain has worn out, it's been ok so far.

Matt

stinky
10-23-2003, 07:24 AM
Taking this one step further, I've calculated the total ratios in each gear using the primary and secondary gear ratios given in the manual for a few sprocket combos. Listed highest to lowest gearing.

16/40 (US Stock):

Gear Primary Secondary Final Total
1 1.935 2.267 2.500 10.968
2 1.935 1.632 2.500 7.895
3 1.935 1.300 2.500 6.290
4 1.935 1.091 2.500 5.279
5 1.935 0.960 2.500 4.645
6 1.935 0.885 2.500 4.280


16/41:

Gear Primary Secondary Final Total
1 1.935 2.267 2.563 11.242
2 1.935 1.632 2.563 8.092
3 1.935 1.300 2.563 6.448
4 1.935 1.091 2.563 5.411
5 1.935 0.960 2.563 4.761
6 1.935 0.885 2.563 4.387


16/42:

Gear Primary Secondary Final Total
1 1.935 2.267 2.625 11.516
2 1.935 1.632 2.625 8.289
3 1.935 1.300 2.625 6.605
4 1.935 1.091 2.625 5.543
5 1.935 0.960 2.625 4.877
6 1.935 0.885 2.625 4.494


15/40:

Gear Primary Secondary Final Total
1 1.935 2.267 2.667 11.699
2 1.935 1.632 2.667 8.421
3 1.935 1.300 2.667 6.710
4 1.935 1.091 2.667 5.630
5 1.935 0.960 2.667 4.955
6 1.935 0.885 2.667 4.566


16/43:

Gear Primary Secondary Final Total
1 1.935 2.267 2.688 11.790
2 1.935 1.632 2.688 8.487
3 1.935 1.300 2.688 6.762
4 1.935 1.091 2.688 5.674
5 1.935 0.960 2.688 4.994
6 1.935 0.885 2.688 4.601


15/41:

Gear Primary Secondary Final Total
1 1.935 2.267 2.733 11.991
2 1.935 1.632 2.733 8.632
3 1.935 1.300 2.733 6.877
4 1.935 1.091 2.733 5.771
5 1.935 0.960 2.733 5.079
6 1.935 0.885 2.733 4.680

Thunder Factory
10-23-2003, 09:17 AM
Stinky

If you really want to see some numbers let me know and I can mail you an Excel spreadsheet which will let you calculate every concievable ratio using different sprcockets and even tyre sizes!

Anally retentive or what! :banana:

mille-ryan
10-23-2003, 09:20 AM
All those numbers make my head hurt :ban:

:happy:

GeoR
10-23-2003, 09:36 AM
Yeah the numbers would be a lot more useful if it included road speed @ rpms in top gear.
That's really all you need to know to figure out your choice of sprockets, at least for the street.

stinky
10-23-2003, 08:15 PM
Originally posted by Thunder Factory
Stinky

If you really want to see some numbers let me know and I can mail you an Excel spreadsheet which will let you calculate every concievable ratio using different sprcockets and even tyre sizes!

Anally retentive or what! :banana:

I concede. You are King Nerd! :worship: