Thanks for everyones input. I found another tire size comparison calculator that lets you compare as many sizes as you want simultaneously.
http://www.autocrossing.com/cgi-bin/tiresize.cgi

By Don (63.135.203.153) on Tuesday, January 25, 2005 - 06:27 am:

Well if he did he obviously didn't have access to the rubber compounds we have today. It might be OK to use a 70 series for street but you will be soundly wupped by people who know what there doing (comp DOT) if you venture in to autocross competition with those treads.

By John S. (66.142.232.141) on Tuesday, January 25, 2005 - 12:08 am:

Oscar Jackson wrote a short treatise on this subject concerning 1st gen cars years ago. He claimed that the 175/70 was the widest tire to use for autocrossing etc. He felt anything larger would not heat up enough to reach the maximum advantage of the tire compounds for stick. This was due to the low weight of the 1st Gen cars. Because of this, and also due to unnecessary stress put on all suspension members by going too wide and increasing the unsprung weight to too large a degree, I have always felt a 185/60 to be max on a 1stGen and 195/60 to be max on a 2ndGen. Even a 205/60 is iffy, and puts a lot of extra sideload stress on the steering, you can feel this in unnecessary additional kickback.

By Mike S (202.12.144.21) on Sunday, January 23, 2005 - 06:14 pm:

On a 5.5" wide rim I would recommend not going wider than 175 section - so 175/70-13 is a good choice. 165/75-13 will also work well - on a 5.5 inch rim the sidewalls are almost straight so the tread is very stable => good handling. I took the same 165/75-13 tyres from 4.5 inch (Accord) rims onto 5.5inch alloys and the improvement in grip and handling (for the exact same tyres) was amazing.

185/65-13 will also fit, but on a 5.5 inch rim will probably not handle as well as a 165 or 175 section tyre. 185 section really needs a 6 inch rim.

By -Andrew Smit- (Cvcc_Wagon) (154.20.95.104) on Sunday, January 23, 2005 - 02:17 am:

i have put a number of different wheels/tires on my 83 wagon and i have seen very little difference between all of them besides traction. here is a handy site for calculating tire size:
http://www.miata.net/garage/tirecalc.html

By Jonathan (68.193.6.173) on Saturday, January 22, 2005 - 01:54 pm:

I don't think you'll see much of a difference. I've had two different size tires on my Civic ('79 Hondamatic), 175/75-13's on stock 13" steel rims, and 205/60-13's on 13x5.5 Panasports. Acceleration and braking were fine with both size tires.

By Kman (68.40.184.98) on Saturday, January 22, 2005 - 12:56 pm:

I know this topic has been done. I read it all. Yet I have questions. I have 165/70/12's (too small)on stock rims (78 cvcc hondamatic). I bought 13x5.5" alloys. I do not want to overwhelm the brakes, engine and transmission with my new tires. I've done a table for my ammusement.

6.00 crossplies diam.rumored to be 590

size ----- radius diam. mm circ.
155s12 -- 11.03 22.06 560 69.33
155/80/12 10.88 21.76 553 68.37
165/70/12 10.55 21.09 536 66.27
165/80/12 11.20 22.39 569 70.35
175/70/13 11.32 22.65 575 71.14
185/60/13 10.87 21.74 552 68.3
185/70/13 11.60 23.20 589 72.88

If the original 6.00 crossplies were actually 590mm in diameter then it seems it would be OK and most accurate to get 185/70/13 tires. This is what I really want. I'm not going to lower the car or anything, I just want more stability. If the original tires were this large, the cruising speed for the hondamatic would have been 9% better than what I have now. I want it back. I will go smaller if it makes braking unsafe or won't go up a hill etc. What do ya'll think?