# Changing Tire Sizes?



## tj4fa (May 25, 2008)

The tires on my 91' Ranger EV have apparently been sitting on the donor vehicle for a while prior to the conversion and are dry-rotted and need replacement. The tread in some areas appear to be seperating. They are P215-70-R14s.

My ' 91 Dodge Caravan before the engine spun a bearing had basically new tires and are P195-75-R14s. According to the calculator shown below, the new size is a little narrower and a tiny bit less tall by the comparison readout from the website linked below.










Do you think the size difference would be a significant factor (good or bad) swapping the tires over from the van to the Ranger? 

This is the website link to the online calculator.

http://www.miata.net/garage/tirecalcold.html

Thanks for your opinion/pros/cons concerning the swap-out.

Terry


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## madderscience (Jun 28, 2008)

Short answer is they will work fine so long as you aren't exceeding their design parameters. And typically, narrower tires roll better. 

But when do I ever give a short answer...

If the tires on the minivan are only rated for 30-something PSI, I wouldn't use them. Rolling resistance is probably going to suck.

Smaller diameter tires will increase your effective torque at the expense of higher motor RPMS at a given speed, but this might be a good thing on an EV.

If you are looking around for tires anyhow, one of the best bang-for-buck ways to improve your range is to use the best low rolling resistance tires you can find. 

These might be a little too small for your ranger, but the bridgestone B381 (185/70R14 is the only size) is one of the best low-RR tires out there. 1200lbs per tire load rating, 44psi. I've got a set on my MR2. other options: Goodyear integritys and sumitomo srixon4's come in more sizes, so there will probably be something that fits your truck. If you've got a ton (literally or figuratively) of lead in the back of the ranger, it might make the most sense to use 60 or 80psi light truck tires in the back, and low-RR tires in the front for the best performance.


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## tj4fa (May 25, 2008)

Thanks for the info MS!

I just went out and checked to see what brand and ratings were stamped on the sidewall.

The Caravan has Goodyear Viva 2 tires (from Wal-Mart). The Max Pressure shows 44psi and Max load is 1400lbs.

I'm still tempted to use these (as right now other than re-mounting and balancing them they're basically "$free") but since I'm about 1500-1600 lbs heavier in the back than the original rear unloaded, I might be better suited to heed your recommendation and use a Light Truck tire (at least on the rear) as you suggest.

Thinking that the front brakes receive at least 2/3rds of the braking duty (and weight shift from rear to front), the transfer of weight onto the front tires when braking might be somewhat higher as well.

I know I won't be able to take them to Wal-Mart to get them mounted. The last time there they would only install the tire size that was indicated on the door sticker. Probably a liability thing.


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## elevatorguy (Jul 26, 2007)

Let me know if you find LT tires for the ranger, I don't think they make them for 14 inch. I am still trying to figure out which tires to go with too..
I think 185/70/14 would be a bit small for the ranger, but I am not a expert.


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## tj4fa (May 25, 2008)

elevatorguy said:


> Let me know if you find LT tires for the ranger, I don't think they make them for 14 inch. I am still trying to figure out which tires to go with too..
> I think 185/70/14 would be a bit small for the ranger, but I am not a expert.


Will do.

The 195/75/R14s on my van might have to "rotate" over to the Ranger for now (budget getting low ).

Bad thing is that to rotate them over and still keep the crappy Ranger ones on my van will cost me about $80-  (quote from the guy up the street).


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## Ioku (Sep 27, 2007)

tj4fa said:


> Thanks for the info MS!
> 
> I know I won't be able to take them to Wal-Mart to get them mounted. The last time there they would only install the tire size that was indicated on the door sticker. Probably a liability thing.


If you have other tire shops tell you they can't mount the tires, just take the wheels off your ranger and just bring them in, I work at Sears auto and we have lots of people do this.


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## tj4fa (May 25, 2008)

Ioku said:


> If you have other tire shops tell you they can't mount the tires, just take the wheels off your ranger and just bring them in, I work at Sears auto and we have lots of people do this.


Exactly what I'm hoping of doing later today!


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