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Old 01-08-2010, 02:31 PM   #16
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I have one question. During a 5 min quals I sometimes run my tires smaller to keep the car in the sweet spot longer or as long as possible. should I compensate my gearing for a lower roll-out due to smaller tires?
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Old 01-08-2010, 04:11 PM   #17
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I have one question. During a 5 min quals I sometimes run my tires smaller to keep the car in the sweet spot longer or as long as possible. should I compensate my gearing for a lower roll-out due to smaller tires?
This is an incredibly good question given that afm stated the MPH based on tire size. We need the the formula that he used to calcuate the numbers, play around with the numbers a bit and viola - you've got your answer. But that's just math.

If the pro drivers are changing their gearing between the qualifiers and the mains, then this would be one of those pro tips that don't really surface until someone asks a question like this. But think about it though, when you change the gearing, you're also changing the performance characteristics of the car, which means your car will perform differently between the qualifying and the mains - which is probably not a good idea. So if everybody has the same game plan and uses small tires in qualifying and everyone starts off with relatively the same tire size for the main, then with all things being equal, it doesn't make sense to change the gearing between the qualifying and the mains - unless everyone is doing it.

I request a B.S. check on this logic please. Thank you!
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Old 01-19-2010, 09:19 PM   #18
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ok guys,i managed to try out a couple of gear ratios on my 966.firstly i tried the defaut gearing which is 16/19,45/48.my frend noticed the car was fast at the slower part of the track but at the straight it seems to reach the 'peak' RPM faster and 'screaming for the last 1/4 of the straight.Hence,he asked me to up the 2nd pinion to 20 so that i have more top end.

when i tried the 16/20,45/48 ratio,there was a difference as my engine doesnt 'scream' and looks as though it still has more to go.But,im having this thoughts that,if i go with the 1st ratio (16/19 pinions),i would have a closer ratio compared to the 2nd ratio (16/20).So what you guys think?Should i go with the 1st or 2nd ratio and sacrifice the top end?Note,the straight isn't that long too.

Thanks.
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Old 01-19-2010, 11:40 PM   #19
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ok guys,i managed to try out a couple of gear ratios on my 966.firstly i tried the defaut gearing which is 16/19,45/48.my frend noticed the car was fast at the slower part of the track but at the straight it seems to reach the 'peak' RPM faster and 'screaming for the last 1/4 of the straight.Hence,he asked me to up the 2nd pinion to 20 so that i have more top end.

when i tried the 16/20,45/48 ratio,there was a difference as my engine doesnt 'scream' and looks as though it still has more to go.But,im having this thoughts that,if i go with the 1st ratio (16/19 pinions),i would have a closer ratio compared to the 2nd ratio (16/20).So what you guys think?Should i go with the 1st or 2nd ratio and sacrifice the top end?Note,the straight isn't that long too.

Thanks.
gearing depends on the engine that you use also.
for my 966, i'm using the nova 359 and gearing i'm using is 16/49 and 19/45...
my straight is about 50m estimated.

by the way, fastest on the straight doesn't win races; you want to be fast on the infield. basically you would want yr engine to reach its peak/top at about 80-90% of the straight in order for the engine to 'clear out' totally.
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Old 01-21-2010, 10:14 PM   #20
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thanks alot for all of you guys' opinons to date,really appreciate it.

anyways,wat is the effects if i change just a pinion or a spur?all i know is that if i change a spur,it will do changes to the engine and the same goes if i change a spur,it will do changes to the car.

so which is which?
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Old 02-03-2010, 12:29 AM   #21
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anyone knows internal ratio for Velox V8 ?

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Old 02-03-2010, 02:41 AM   #22
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thanks alot for all of you guys' opinons to date,really appreciate it.

anyways,wat is the effects if i change just a pinion or a spur?all i know is that if i change a spur,it will do changes to the engine and the same goes if i change a spur,it will do changes to the car.

so which is which?
I am not sure I understand the questions but I'll take a shot at answering this.

A change in a pinion (metal gear on clutch bell) makes a much bigger difference than a change in a spur (plastic gear on 2 speed).

I experiment with gearing in order to get the lowest lap time on the track I am running on. Not always is the ratio that gives the fastest lap times the easiest to drive due to where the car wants to shift gears.

For instance, the ratio that provides the lowest lap times on our track wants to make a gear change in the middle of a sweeper which tends to kill straight away speed. In order to use this ratio I have to be very careful with my throttle position in order to hold the car in low gear going through the sweeper. If I do the throttle correctly in the sweeper I have a good lap time.

I can add 1 tooth to my pinion and not have to be so careful in the sweeper and basically run full throttle through the sweeper but my lap times are .1 to .3 slower per lap.

The only way to tell what ratio is right for you is to experiment and see what gives you an easy to drive car that yields good lap times.

Lee
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Old 02-21-2010, 08:50 AM   #23
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Also, the top of the spreadsheet has the FRONT to REAR overdrive ratio info based on the diameter of the tires that you have on your car. This is useful because a lot of people run different pulleys on their car. This spreadsheet allows you to change the number of teeth on the pulleys to see what impact it has on the front to rear overdrive ratio.

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is the overdrive ratio meant to be kept as close to 1.0 as possible, what happens if you go above and below?

thanks
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Old 02-21-2010, 11:07 AM   #24
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at 1:1 front and rear r spinning the same speed above 1:1 means the rear is spinning faster than the front car tend to spin out more lower than 1:1 front spinning faster than rear car doesnt spin out as easy but tends to push more in the turns cause the front wheels r pulling the back wheels along hope that makes sence someone correct me if im worng i run my mtx4r at 1.005:1 and as long as your not just hold the wheels one way and mashing on the throttle it seem sto rotated good but not spin out very easy
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Old 02-21-2010, 12:45 PM   #25
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is the overdrive ratio meant to be kept as close to 1.0 as possible, what happens if you go above and below?

thanks
The more you go above 1 (more front wheel drive) the more stable the car will be but the more it will push when on throttle. The more you go below 1 (more rear wheel drive) the more steering you will have on throttle but the car will be difficult to drive because the front wheels won't start pulling until the rear wheels are spinning.

I usually ran somewhere in the 1.01 to 1.04 range. This gave good stability, decent steering under power and I could be aggressive with the trigger coming off of a turn without worrying about the back stepping out too much.

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Old 02-21-2010, 01:32 PM   #26
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The more you go above 1 (more front wheel drive) the more stable the car will be but the more it will push when on throttle. The more you go below 1 (more rear wheel drive) the more steering you will have on throttle but the car will be difficult to drive because the front wheels won't start pulling until the rear wheels are spinning.

I usually ran somewhere in the 1.01 to 1.04 range. This gave good stability, decent steering under power and I could be aggressive with the trigger coming off of a turn without worrying about the back stepping out too much.

Lee
thanks for the replies, I'm actually running 220mm with oneway ect do you think this sort of car will cope with more drive to the rear?
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