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Tyre and wheels size

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J

John_Robertson

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Hello all,

I have a bug eye which I am restoring. I am trying to make a decision on wheel and tyre sizes. The ones I took off were 13x5" rims with 165-70-R13. I would like to go up a size or two in wheels size ie 14"x5" or 15"x5" obviously I would like to keep a similar rolling diameter. I do not want to flare the guards and it will be predominantly a race car. Any sugestions?

Many thanks,
 
I've been happy with the performance of my 165/70 on 13" rims. Are you wanting to change for performance reasons or for a visual effect?
 
My main reason is for performance. I would like to decrease the profile without decreasing the rolling diameter. I also think they might look good too.
 
So, you believe that your current tires are not providing a large enough contact patch? Or are you concern about roll from sidewall flex? You can certainly move up in tire size, but you need to consider how it will effect the rest of your suspension. Of course, you will have a harsher ride, but you are also exerting more forces on the rest of the system that is normally absorbed by a taller tire. Also, if your tire doesn't break grip, will something else break?
OK, you asked what size tire/wheel. If you look at a tire size calculator like: https://www.miata.net/garage/tirecalc.html then you can find what will give you the same rolling radius. You'll find that you can't really go beyond a 14" rim (unless you want to use a rubber band for a tire). So, where do you find a 14" rim with the correct bolt pattern and back spacing? Special order custom I believe. (Might be something available in Australia that I'm not familiar with).
Lastly, to keep your car in line you should fit a rear panhard bar and uprated front sway at a minimum.
The above is my 2 cents (and others will surely have differing opinions)
 
Trevor, I absolutely agree with you. I'm not terribly familiar with the bugeye (although I'd sure like one for a racecar project ... /ubbthreads/images/graemlins/devilgrin.gif ), however, I am working on the same situation with my '76 Midget. I too had 165/70's on my stock 4.5" wide wheels. I'm trying to fit 175/60R13's because that's the smallest DOT Legal racing tire size. They're supposed to go on the moss wheels. In order to prevent sideways travel, I'm working on a panhard rod, and I've already done a 3/4" swaybar up front, as well as hard bushings all around. In a square arched spridget, there's no way to avoid rub without lateral axle location. At current, with the current wheels and tires, I already get some tire rub on the insides of the fenders under hard cornering (as evidenced by the undercoating which is missing in a strange pattern resembling a tire /ubbthreads/images/graemlins/tongue.gif ). I'd imagine that this problem is similar with the bugeye, though the fenders may well be more forgiving. The loss in net tire diameter from 165/70 to 175/60 is about .8" meaning that the car will sit almost a half inch lower when the race tires are on it (it already has only about 3" net ground clearance). Assuming you could get a 14" wheel in the correct bolt pattern that would be lug centering, it should fit, but you'd need to check about proper offset to guarantee that. It'll be hard to get tires smaller than 185/60R14 in a competition tire, so this is another consideration. Consider however, that the stock wheel for a bugeye is either 3.5 or 4" if I'm not mistaken, so the increased suspension loads are huge. The hub will now have to withstand considerably higher cornering acceleration as a result of the improved grip, plus the wheels are heavier. Be prepared to crack check regularly, but I'm not sure what else to tell you. Bugeye58 on this forum has raced a bugeye in the past in SCCA Production racing, so he can give you more specific advice about these things, but he uses (if I'm not mistaken) 13" wheels and tolerates the reduced rolling diameter.
 
Thanks for the points. It is a very good point you raise about regular crack testing which was always going to be on the cards. I have used a tyre calc. and the tyres that represent a mimimal rolling diameter change are 165/55-15 and 165/60-14. I am have a few issues finding a decent tyre with a good compound at these sizes. We can get special make wheels here in Aus. right size and offset etc.. I guess I am really hunting for tyre brand and serries info I suppose?? and or any other people who have experience in larger rims sets on these cars.
 
John.

Ive tried on a set of 16 inch rims on my 69MGB, they came off a 180sx. They fit but they sat inward too much,(Negagive offset i think /ubbthreads/images/graemlins/confused.gif) i would have needed mega spacers and even then the nuts would only JUST have grabbed.

I'm also curious as to how low profiles go too, id love to whack on a set of low profile 16s on my B. Too bad everyone on BCF seems to be a purist and looks at me like... /ubbthreads/images/graemlins/confused.gif ....Such a boring way to look at cars.
mgon16s.jpg

Let us know how you go!

Cheers mate

Jarrod
 
I think I have come to a conclusion. My tyre choice is Yokohama A032R 175/60HR14. These are a highgrip soft compound race tyres that are also street legal. And for wheels, I will be putting them on 14x5" Performance minilight mags.

I think this should be a awsome looking and performing package
 
So, who is the manufacturer of the rims? Are you having them custom drilled for the 4" PCD? What is the offset? This information would be good to have for future reference. Thanks.
 
Do you mean 175/60R13 or 185/60R14? As far as I know, Yokohama doesn't make a 175/60R14 tire in the A032R.
 
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