Has anyone encountered this problem? I'm driving a '73 MKIII GT6 and I decided to treat her/me to a set of minilites to flush out the arches. I figure 205/70/13 should do but now I'm reading that the 7" wheel can take 215/60/13. Please feel free to conmment.



Edited 1 time(s). Last edit at 07/28/2010 11:17AM by sam74.

sam74,
I think you will find that 205 width tires will rub unless the inset/offset/backset of the wheels is just right. 215 width tires will of course be even more difficult to avoid rubbing problems. Another issue is the nominal diameter of the tires; in the case of the 215/60 tire it is about 23.1", the 205/70 tire works out to be 24.3". The standard tire is 155/80 which has a diameter of 22.76". So the 205 tire is kind of tall which will aggravate any clearance issues. If your car is swing spring rather than Rotoflex you may find that you don't get as much benefit as you may expect because the wider tires tend to run on their edges when the car leans in a corner. Another issue to consider is how well the car will behave on wet roads; wide tires must move more water out of the contact patch to get down to the road surface so there may be a greater tendency to hydroplane; especially on very wet roads. Matching the wheels and tires that someone else has used can get you through these issues, but you must really match them perfectly.
Best of luck,
Paul

Samuel,
This link http://www.discounttire.com/dtcs/infoTireMath.dos is a great way to do tire calculating, although I'm not sure if I'm allowed to post that or not. Like Paul said, trying to match a tire as close to the original diameter will help but as far as the width, maybe someone else knows how wide you can go. I have a set of 185/70/13 on my MkI but I'm pretty sure my rear end is about an inch narrower on each side compared to the MkIII. I get rub on the front sometimes but not on the rear.
ryan

I know a 205 tyre can fit under a MkIII GT6 as I have a pair on mine, on 6.5" rims (sitting a bit too high in this old pic)

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http://triumphulation.blogspot.com/

Thanks Paul. You have left me with a few points to consider. I will post a pick in the next weeks.

Great pic Stephen. 205 seems more and more to be plenty for the GT6 and looking at your car the width seems just right. Cheers.

I've got 205's on the back of mine, still waiting to purchase for the front.
I know they fill the wells nicely and don't seem to hit when hitting bumps.

185's on the fronts now and they seem about right.

Not to hi jack the thread but are there any advantages, disadvantages in running different sizes front and back?

I like the way the car sits with this arrangement.

Hi Tracey! I'm not an expert, but it has been explained to me that when changing tyre sizes you are in effect changing the ratio between the wheels and the diferential. Also, the sequence between wheel rotation and the speedometer will be out of sequence. I'm sure someone else will give you a more detailed answer.
Try this website out: http://www.kouki.co.uk/utilities/visual-tyre-size-calculator. It will give you a guide to hw the replacement wheels will alter your driving set up.



Edited 1 time(s). Last edit at 08/06/2010 12:21PM by sam74.

Thank for the reply.
I knew that the taller tire would necessarily alter the revolutions of the speedo. ie make the speedo read slow...
I'm not teribly worried about that as I've never had an old car that the speedo was right anyway.

I'm wondering if the taller tire on the rear, shorter up front would have too much of an adverse affect on suspension, handling, etc...?

I can't think of anything other than the front wheels spin a bit faster to keep up with the back.