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Old 09-16-2002, 09:50 AM   #16
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Quote:
Originally posted by modellor
I know the theory of overdrive. I have raced 1:8th on-road for 15 years at International level.

It is faster to use a solid axle in the rear with one-way or solid in the front and overdrive the front end regardless of the track layout.

I take it you have only read a few books explaining the theory of it?
I think I have to agree with modellor on the top speed of the overdriven car. My V-One RR is faster on top than my GRP version by way of a more overdriven front end. (the difference being in the internal gearing) I do notice also, that around the sweepers, when I let off the throttle and get back on it, the RR isn't as punchy. With the GRP, I could just blip the throttle to carry speed out of the sweeper and set up the next turn, but with the RR I need to really get back on the throttle hard after I let off.
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Old 09-16-2002, 09:51 AM   #17
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Quote:
Originally posted by modellor
... I have been doing it for 15 yrs.
I have competed at International level and my bills would scare you.
Lol, great quote!
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Old 09-16-2002, 10:36 AM   #18
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I run a MTX-2 and a GT4 and I'm thinking of just trying out the over drive set up to see what's its like. My question is what should be done to get the overdrive effect? Which pulley should I change?
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Old 09-16-2002, 12:35 PM   #19
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Quote:
Originally posted by tekrsq
The truth is, most TC are overdriven slightly anyway as soon as the rear tires wear.
I thought a car goes underdriven if the rears get smaller than the fronts...all else being the same.
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Old 09-18-2002, 11:48 PM   #20
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Damn fine debate in this thread.

Is it safe for the readers of this thread to conclude that the amount of front overdrive is a matter of personal preference? That is, the less percentage of front overdrive is fast but gets twitchy; so how much twitch can you drive.

If my math is right (it often is not,) the V One RR with its 25T middle belt driven pulley has about an 8% bias to the front. Then I look at some serpent charts and see percentages like 1% to the front.

What are some overdrive percentages that are being used (ammdrew & modellor)?
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Old 09-19-2002, 12:12 AM   #21
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Quote:
Originally posted by RC
Damn fine debate in this thread.

Is it safe for the readers of this thread to conclude that the amount of front overdrive is a matter of personal preference? That is, the less percentage of front overdrive is fast but gets twitchy; so how much twitch can you drive.

If my math is right (it often is not,) the V One RR with its 25T middle belt driven pulley has about an 8% bias to the front. Then I look at some serpent charts and see percentages like 1% to the front.

What are some overdrive percentages that are being used (ammdrew & modellor)?
Which Serpent chart are you looking at?

On the Serpent Impulse / Impact, overdrive is usually used to compensate for different wear rates on the front and rear foams. Rear usually wears faster. A split of about 2 to 3 mm diameter difference between the front and the rear is usually used (i.e. front smaller than rear). Don't know how many percent overdrive that translates too in order for you to have to run that split. You can refer to the website here to automatically calculated overdrive.

http://home.zonnet.nl/realrolfje/pro...t/overdriv.htm

Julius Kolff (Serpent Holland driver at the Worlds) usually drives a split of about 3 mm on the Impulse PRO. I don't think it's because of tire wear but he claims that by using a split, you are able to sit the front suspension closer to the position the car was designed to. For other cars, I don't know if this works right.

BTW, ammdrew is not able to respond because he's competing in the 200 mm World Cup GO SERPENT !
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Old 09-19-2002, 09:40 AM   #22
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Quote:
Originally posted by patelladragger


I thought a car goes underdriven if the rears get smaller than the fronts...all else being the same.
Man I get confused between overdrive and underdrive too! All I know is the front is spinning a little faster than the rear!
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Old 09-19-2002, 10:05 AM   #23
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Default Impact 4WD

My son has been racing an Impact for two years and we usually run the rears 4 to 5mm larger than the fronts. For qualifying we will start with a 68/64 diameters but for the mains we will go about 2 mm larger. We may even cut the outside tires another 1 mm or more larger than inside before a long (30 minute) main to compensate for wear when there are fast sweepers on the track. Running oversize tires will allow tires to wear in to the qualifying diameter where handling improves over the course of the main, besides it helps keep car from bottoming out! Keep in mind that adjustments have to be made with steering throughout the race especially if the outside tires are wearing faster.
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Old 09-19-2002, 10:10 AM   #24
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Default Overdrive

You want the drive ratio close to 1:1. If the rears are undersize then the fronts will have to pull the car down the straight and the rear end will put a drag on drivetrain which can cause engine to overheat. If you overdrive the front then you have to be smooth on the throttle to keep rear end planted.
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Old 09-22-2002, 12:52 AM   #25
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Default Re: Overdrive

Quote:
Originally posted by John Patterson
You want the drive ratio close to 1:1. If the rears are undersize then the fronts will have to pull the car down the straight and the rear end will put a drag on drivetrain which can cause engine to overheat. If you overdrive the front then you have to be smooth on the throttle to keep rear end planted.
Interesting nugget of info regarding the engine heat... thanks.
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