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Old 11-26-2014, 11:10 PM   #1981
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Quote:
Originally Posted by cplus View Post
90 spur

21 = 7.92

You get very little granularity at those ratios though.

For example, 20 = 8.325 and 22 = 7.56

Big jumps. Stick to 64p for mod.
I am not sure what you call granularity, but the jumps are the same in 64 pitch as well. Your comment is then misleading because changing pinions of course is bound to induce large differences especially at low tooth count values, simply because of the mathematics. For instance a one tooth difference to a 20 tooth pinion is 1 in 20. The larger the pinion, the smaller the difference (for a 40 tooth pinion, the difference would be 1 in 40, of course). The result is then that if you want smaller variations (a smaller increase in ratio) you have to change spurs, not pinions. For the example above, 1 tooth in 90 is a very small difference and the result is you can hit 8.0167 (21/91) or 7.84 (21/89). You can get even finer increases if you look at combinations (spur/pinion) as a whole. For instance 96/21 will give you 8.07 FDR. And you could stick with a 21 pinion and have available 95/21 which will give 7.9886, and 94/21 which will give 7.9045 and so on.

The only difference is that 64 pitch will allow more combinations to be used before you run out of room for adjustment on the motor mount simply because of the smaller diameter increase between two spurs/pinions of neighbouring size (one tooth difference). I haven't checked these sizes because I do not run mod, so you'll have to do the checking to see what fits. At our track however, people run mod with 48 pitch without problems and their FDRs hover around the same values.
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Old 11-27-2014, 01:47 AM   #1982
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Thanks for your sharing your insight.

Last edited by cplus; 11-27-2014 at 04:02 AM.
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Old 11-29-2014, 10:38 PM   #1983
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Ive been using the stock chassis with smokem top deck for 17.5 blinky with some great results!!
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Old 11-30-2014, 06:23 PM   #1984
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yesterday was my first time driving a touring 1/10 car, it was fun! 17.5 on fdr 4 and gear diff with 500000 oil in front. easy and stress free drive. i do have a question, my rear keeps sliding a little until i stand up the rear shocks. but it kinda square off sometimes. do you think placing abck to stock position with a harder spring will solve it?

low grip carpark surface. everything stock except the front diff.
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Old 12-01-2014, 12:45 AM   #1985
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Not enough info, my friend.

Does it slide out on power, off power, when neutral (coasting), what?

Your rear end is obviously losing grip but you need a clairvoyant to guess why (see above) if you don't let us know. The solution is going to be different.

At a guess I would look at roll centres first (admitting you have the spring ratios right, the right tyres, and the rear gear diff and so on, which is all as far as we know a mystery) because of the low grip surface, which makes me think the car needs to roll a bit to put some weight on the outer wheel to plant it down.
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Old 12-01-2014, 01:00 AM   #1986
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Does it slide out on power yupz! it does that
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Old 12-01-2014, 01:09 AM   #1987
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Quote:
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I am not sure what you call granularity, but the jumps are the same in 64 pitch as well. Your comment is then misleading because changing pinions of course is bound to induce large differences especially at low tooth count values, simply because of the mathematics. For instance a one tooth difference to a 20 tooth pinion is 1 in 20. The larger the pinion, the smaller the difference (for a 40 tooth pinion, the difference would be 1 in 40, of course). The result is then that if you want smaller variations (a smaller increase in ratio) you have to change spurs, not pinions. For the example above, 1 tooth in 90 is a very small difference and the result is you can hit 8.0167 (21/91) or 7.84 (21/89). You can get even finer increases if you look at combinations (spur/pinion) as a whole. For instance 96/21 will give you 8.07 FDR. And you could stick with a 21 pinion and have available 95/21 which will give 7.9886, and 94/21 which will give 7.9045 and so on.

The only difference is that 64 pitch will allow more combinations to be used before you run out of room for adjustment on the motor mount simply because of the smaller diameter increase between two spurs/pinions of neighbouring size (one tooth difference). I haven't checked these sizes because I do not run mod, so you'll have to do the checking to see what fits. At our track however, people run mod with 48 pitch without problems and their FDRs hover around the same values.
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Old 12-01-2014, 03:35 AM   #1988
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Quote:
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Does it slide out on power yupz! it does that
Yeap, you need more roll (after you make sure you have a light oil in the rear diff - that means no more than 2k CST). See above.
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Old 12-01-2014, 03:36 AM   #1989
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Quote:
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Ah, shucks!
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Old 12-15-2014, 12:04 PM   #1990
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Is anyone else doing that shorty conversion like kentech does? I've considered it but seems like the weight would be very unbalanced on one side.
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Old 12-15-2014, 02:18 PM   #1991
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anybody know if the 419 gear diff fit on the 418 ?
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Old 12-15-2014, 03:09 PM   #1992
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yes it does, guaranteed by kentech
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Old 12-15-2014, 04:54 PM   #1993
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Yep, it's the same size, it also fits 417, 416.

It's smooth but so was my original one. It might be more noticeable in mod than stock
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Old 12-23-2014, 07:12 AM   #1994
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MY 418 STILL OUT RUNS THE 419 WITH CLOSE SETUPS....
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Old 12-23-2014, 07:17 AM   #1995
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Top decks are not interchangedable....
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