Gauge cluster/ tire size change ?

CivicSpoon · 01-20-2005, 02:02 AM

Ok I just thought about this, so bare with me on this.

I have CX that came with 175/70/13 rims, during the summer time I use 195/50/15 rim. With that change, my speedometer is as close to accurate as possible. This summer I plan to get new tires for my 15's as well as a gauge cluster with a stock tach. I'd like to get narrower tires that 195's, just for the fact that my car understeers horribly with that size (more understeer and no PS sucks). I'm also planning to get a motor swap this summer as well (I'll explain why I mention this too).

So here's what I'm curious about. I understand the whole tire size effecting the speedometer thing. But what tells my car the tire size to be calibrated to? I mean what tells my car that it came with 175/70/13 wheels on it and not 14's? I'm assuming it's probably the vehicle speed sensor. But couldn't I change the VSS with one that came from the vehicle the motor I swap in came from; thereby changing the accuracy of my speedometer?

If anyone can shed some light on this I'd appreciate it.

97CivicX · 01-21-2005, 12:04 AM

your car doesnt know what size tires you have. if you went from 13's to 18's it be very off.

switching the vss is an interesting idea. maybe if the 01+ (with 15' wheels) vss fit, you could have it accurate. or you could just have a shop calibrate it for you...

CivicSpoon · 01-21-2005, 12:21 PM

The car has got to know somehow that I'm using 13's over 14's from the DX, LX, EX, Si. There has to be something that is calibtrated to it. Otherwise either my car and the VX would be off using 13's instead of 14's like the rest of them. But it is the VSS that is calibrated to it?

97CivicX · 01-21-2005, 04:24 PM

from the factory your car is calibrated with the wheels it has. if you get larger/smaller wheels it can be recalibrated. the car wont do it itself

CivicSpoon · 01-21-2005, 05:41 PM

Yeah I understand that it's not going to change on it's own. I just wasn't sure what I would need to have recalibrated or if there was something I could replace.

BullShifter · 01-21-2005, 08:42 PM

The wheel diameter doesn't matter, it's the overall diameter of the tire that makes a difference. To learn all about proper plus sizing go to www.tirerack.com AND www.whalentire.com to see what your speedo will read and how much it will be off. Spend 10-15minutes at those 2 sites and you will be all pro when it comes to the difference in heights.

Buy the correct sized or plus sized tires and you will not have worry about recalibrating anything.

CivicSpoon · 01-21-2005, 10:01 PM

I'm an idiot, I'm not writing the things I mean. When I said the size of the wheel I ment the rim and tire, but then I just refered to the rim size. I should have been more clear on what I ment. I got a book that has a ton of info on wheel diameter (tire and rim) and I looked at that miata site about getting the right size so my speeedometer isn't off. I was just thinking that I might be able to get a different size tire for my 15's if my car was calibrated for a bigger size rim. Right now I've got tires on my 15's that are almost perfect; when Im going 60mph my speedometer says 60.1mph according to that miata site. I just hate the understeer from the 195 and I'd like to go down to the 185's (of course matching up the right tire height). With my car now, putting on 185's it's going to be a problem with my speedometer being accurate.

BullShifter · 01-22-2005, 11:58 AM

Using skinny tires all the way around will make the understeer worse, a skinny tire in the rear will help loosen it up. Understeer is a Front wheel drives worst enemy. The best thing you can do to help neutralize or increase oversteer is to install a larger rear sway bar and I highy suggest a reinforcement kit with a larger rear bar. Lower tie's aren't a bad idea either.

Suspension Tech makes decent sways for the money www.jegs.com
Reinforcement kits - http://www.beaksproducts.com/Products.htm
Tips - http://www.heeltoeauto.com/marketplace/beaks/?N=A

jameskersten · 01-22-2005, 10:33 PM

you can change the size of the rim all day as long as you keep the same circumfrance the same. that is how you keep the vss you got now. shouldnt be any reason to change anything

jameskersten · 01-22-2005, 10:34 PM

and the size difference in tires you use between a 13 and 15inch tire is usually so little it would matter much anyways.

CivicSpoon · 01-22-2005, 11:52 PM

I'm planning on getting sway bars (front and back unless someone can give me a reason to only get 1). I'm just doing some planning incase the sway bars don't fix the understeer enough. My car didn't come stock with any sway bar, so I was originally looking at the beaks kit. But I've heard of subframe rip out problems in the rear with them on the EK's. Which is strange because that article you gave me talks about using the beaks kit to help that from happening.
Oh well I'll just get the parts and see how it goes.

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