Quote:
Originally Posted by minibajaman
No need for a diff on off-road race cars. The gear ratio is probably pretty close to what you need; most Baja cars are running anywhere from 7:1 to 10:1 with a CVT. 4.85:1 is only for bike powered mini buggies and is in no way comparable to a Baja SAE car. You can do the calculations pretty easy to figure out what gearing you need for a top speed of say 35 mph. Or look around on here, I posted a spreadsheet that does the gearing calcs for you several times before.
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While I tend to agree with the diff. statement on high horsepower bike engine based buggies or pro-lites, pro-2s, etc...(off-road vehicles with power), I prefer having a diff. in our car. We are going to convert ours over to a spool soon to test it but as of right now I prefer the diff. to all our older cars which all have spools. It is worth it to me if only for the ability to easily push the car around and to be able to do a slow speed turnaround without taking a football field sized area to do it.
I also agree that 4.85 is way off. Like he said, depending our your setup somewhere between 7:1 to 10:1 will likely be best. Also agree that a top speed of 35 is a good range. That will put you right there with the fastest cars at the competition.
Also, if you are serious about cutting weight you will stay away from UTV tires. Wheels/tires are a place that I see lots of people packing a lot of unneccessary weight.
USF runs a 6-speed out of something but I can't remember what it is from. I think you are going the right direction with the CVT. People bitch about manuals being more efficient but the more competitions I go to the more it confirms that I don't want one. USF and maybe one or two other schools are the only teams that I have seen that are competent in driving their manual cars to the point that they are actually taking advantage of that extra power. Also, if you read what USF has said about their manual, it isn't like they just through it in and it worked. Like any other good team, it took a lot of experimenting and tuning to get it all set up right and working like it does.