Bigger is not always better. You can usually go up one tire size from original safely. After that a lot of thought should go into what you are doing. Steering racks and gears, suspension parts, wheels, were all designed to work with a specific tire and wheel. When you just up and change them all sorts of things start to happen. To much rubber on the ground can give the car a lot of stress it was never designed for. Suspension parts begin to fail and so do frame members. fuel mileage goes down and the car can get very twitchy. 

     Let's look at some of the numbers on a tire. We will start with a 185/85 R15 the stock size of a TR6 tire. the first number is the width of the tire. This tire is 185 mm wide. the second number is the aspect ratio. This is the ratio of the height to the width of a tire. The lower this number the "wider" the tire. The width of the tire is still the same 185 but we can change it to a 75 and we have just lowered the sidewall so the aspect is wider. The letter means it is a radial with out any type of speed rating. It has a safe sustained highway speed less than 100mph. an S rating is 115, H is 130, V is 150 and Z is 150+. As the speed ratings go up so do the handling characteristics and the tread life goes down. The last number is the diameter of the wheel. Now, if my Triumph was supposed to have a 185/85 R15 and I wanted a bigger tire a 195/85 R15 would be fine though you will never find one. So now we play around a little We need to have pretty close to the same rolling circumference or our Speedo will be off and so will our performance so we do not want to just put on a 185/65 R15 tire. To short. A 205/70 tire has just about the same rolling circumference of a 195/85 tire so it will fit and work on the Triumph if we have the wheel well clearance. {on our link page are some sites that can help here}. I happen to know this size works and works well on a TR6 with Mag wheels. You have to change the wheels and you can not go bigger or you begin to run into problems. 

     People with wire wheels need to very careful. First none of the wheels that are 48 spokes will handle today's radial tires! I personally think those of you who ride around on 48 spokes are nuts and have a death wish. The more spokes you can get the stronger the wheel. The stronger the wheel the better tire you can put on. Make sure you do not try to put to wide a tire on two narrow a wheel. You can safely go 1/2 inch wider than the wheel. Or you can put a 5.5 inch tire on a 5 inch rim. {we are talking rim width here}. Besides checking the wire well for the obvious loose & broken spokes. Check the splines, do they look curved are they sharp to the feel? Toss the wheel. Check the hubs the same goes. Solid wheel have their problems too. Check for cracks and worn or egged out lug holes.

     Radial or Bias? What do you want to do. I like both. I prefer to race on bias and drive on radials. I have done both, both ways. If you are planning to be doing lots of four wheel drifts and the like I would recommend bias tires. Much easier to recover and less stressful on your wheels and suspension. If you plan on nothing more than a spirited romp every so often a good set of radials works fine. Try to stay as close to original sizes and dimensions as you can to prevent to much stress. Firestone makes a very good looking 185/16 radial that works very nice on Jags and the like. I know in today's market you can find some Yokahama tire like a 225/65-16 that seems to work and fits. The stress you are putting on your wheels and tires is out of this world. Without doing something to beef these up not only are you flirting with disaster but I can probably walk away from you on a winding road all other things being equal! You get what you pay for big time in tires. Cheap tires are cheap! No mater what type of tire you chose use radial tubes if you need tubes. We prefer Michelin or Classico. Do not use a larger tube than the tire! A 185 /15 tire can not use a 195/15 tube. It can use a 165/15 tube. You pre-war guys with 18 inch tires, try a 16 inch tube. Works wonders.

     Brakes, tires wheels the most important points on your car. Spend your money there first. Then the suspension, then the cooling system, then the engine then the interior! Make it safe and reliable first.