I have an old Xpit F4 with GT750 Water Buffalo engine. I just started to use it for AutoX and I think I need to change the gear ratio.The course I ran was
tight and short. not like an SCCA one. It currently has a 16T primary with a 45T on the diff. It has 13x6x20 slicks. The engine is around 90 HP. I do not have
any info on the transmission gear ratios. Ant suggestions ?
AutoX gear ratio
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 Xpit77 |
AutoX gear ratio |
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Registered User
Posts: 16 06/22/08 09:52:09 |
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CanAmwannabe |
Auto-X ratios | #1 | ||
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Registered User
Posts: 91 06/23/08 22:24:06 |
I don't know what your gear/primary reduction numbers are but I use a 15/46 on my Yamaha R1 powered Legrand DSR used for Solo racing, My rear slicks are
21". We run mostly on airport runways so speeds are a little higher than a typical parking lot course.
I would start by dropping the counter shaft sprocket down a tooth to begin with and see how it goes.
Joe Gonzalez
1979 Legrand Mk18 DSR Yamaha R1 |
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Xpit77 |
#2 | |||
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Registered User
Posts: 17 06/26/08 16:36:24 |
Thanks Joe,
I found a 15T and a 14T in one of my boxes of " Too many spares to mention " I will install the 14T first and go from there. Thanks Sports Racer.Net Steve |
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Jake Latham |
#3 | |||
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Registered User
Posts: 394 06/26/08 16:56:27 |
Tommy Saunders (former BM champ) told me he ran 13/48 with his 20" rears. I ran 13/50 with good results on 22" rears.
-Jake |
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Dean Todd |
Easily calculate road speed vs engine RPM/gear | #4 | ||
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Registered User
Posts: 18 06/27/08 21:20:49 |
I have used this sight for years to calculate speeds in gears; not2fast.com road vs engine speed. Use tire diameter of 253, aspect ratio of 45 and diameter of
13 and you get a 21.9 diameter (you cannot just put in 22/10x13). Next plug in the trans ratio, rear end ratio and RPM and it gives you the road speed.
I have run the numbers for a 47 and 48 tooth rear sprockets with 14,15, 16 and 17 tooth front sprockets and gotten the speeds in every gear. It doesn't take very long and makes sprocket selection very easy. I hope this helps, Deane "Zero My Hero" Todd |
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moulckers |
#5 | |||
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Registered User
Posts: 4 06/27/08 22:56:58 |
We changed our gearing recently when we put a Quaife limited slip diff in our 74 Legrand/Gazzorman. The car weighs about 1000# sans driver and is powered
by a fuel-injected 2004 ZX-10R. My son weighs around 140#, me 250+#. We've settled on a 15/50 ratio and run most courses in second gear with 22 or 22.5
by 10 rears.
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Xpit77 |
#6 | |||
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Registered User
Posts: 18 06/28/08 16:20:08 |
Thanks boy`s,
I use to crew a left turn dirt car back in the day. I remember the crew chief, the driver and the owner discussing gear ratio`s I should have listened to what they were talking about. I do remember helping to pull off the rear end gear cover and handling those hot gears....ah ......good times . I will use your advise and get back to you later with the results. Thanks SR.net, Steve |
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Xpit77 |
#7 | |||
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Registered User
Posts: 19 06/29/08 11:50:40 |
I found a new 14T primary on Ebay for $19.00. It`s in the mail.
Steve |
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