Wheel Diameter - Final Drive

[Apolan]

So i got myself the LFS Tweek, and with it i made a Stock AE86. Now i started messing around with various settings to see how it would (virtually) respond to various modifications. As you can play around with wheel diameter in LFS tweek i noticed you would get shorter gearing with smaller diameter tires. So my question is, does putting on smaller diameter tires (i.e. 185/55 14) provide the same resoults as shortening the final drive? i think it does. The obvious question pops to mind; why would anyone spend money on new "shorter" ring&pinion, when you can get the same resoult for virtually no money?

[firehawk]

Yes, the wheel diameter does affect the gearing. Check out this calculator I made a while ago for visualizing how the changes in gears, final gear and tyre size affect the top speed for each gear;

http://www.r5r.net/index.php?option=com_...&Itemid=48

[Apolan]

wow, great! so as i thought. putting on 185/55 14 wheels instead of stock 185/60 14 is the same as changing the final drive from 4.300 to 4.450.

ps, just one thing i dont understand. whe rpm's in the bottom 5 windows are engine speed in 5th gear? for that speed or what?

[firehawk]

Apolan Wrote:ps, just one thing i dont understand. whe rpm's in the bottom 5 windows are engine speed in 5th gear? for that speed or what?

That's the rpm speed at which you "enter" the gear if you run the previous gear all the way to the revlimit and shift up. So with a completely stock setup, if one accelerates on 2nd gear to 7800rpm and shifts up to 3rd, the tachometer should show 5339rpm. Of course, it's a theoretical figure as one would actually shift up a bit before the revlimit and shifting takes a bit of time but it can be used to get a feel whether the engine stays in the powerband during upshifts.

[Apolan]

superb stuff man!

[NoHachi]

Don't forget that you also lower the CoG without any penalties to your suspension setup..also the less tall tires are a tad lighter. All benefits.

[oldeskewltoy]

only one drawback... gas mileage suffers... unless you have 2 sets of wheels and tires

[Ferret]

Other drawbacks:
Reduced ground clearance.
Your speedometer will read wrong.
Smaller tires will wear fasters than bigger ones.
Cosmetically less appealing.

[Apolan]

Ferret Wrote:Other drawbacks:
Reduced ground clearance. - not really a drawback?
Your speedometer will read wrong. - aaah who cares
Smaller tires will wear fasters than bigger ones. -troo, but they are cheaper
Cosmetically less appealing. -very subjective. i like 185/60 13 on a nice rim more than bigger wheels...

[Ivan141]

ehmm..if you consider less tall to be a 185/50x14 tyre, then the cosmetically less appealing argument is not exactly correct. I've seen konig rewinds with 185/60x14 and with 195/45x14, the low profyle tyres look MUCH better on them.