Opening "A can of worms"?

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Opening "A can of worms"?

Postby Readit » Sun 13.08.2017, 18:46

I am sure i will be shot down if flames for this post, but here goes. Having seen Phil's Pacific Blue Elan equipped with 17" wheels I started to read the various threads on "Wheels and Tyres". it is well known the original UK Elans had 15" wheels and US and Bugatti S2 Elans had different types of 16" wheels. Some threads make reference to larger wheels filling the wheel arches better as per Peter Stevens original concept.

Now here is the question. if the wheels fill the arches better then the wheel and tyre combined must be larger? This would affect the rolling circumference of the wheels, the speedo accuracy and gear ratios. I may be wrong but surely a larger rolling circumference with same gearing , same power will make the car slower?

If acceleration is desired then surely 15" low profile tyres would increase it but at the expense of top speed. Any comments?
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Re: Opening "A can of worms"?

Postby Saltire » Sun 13.08.2017, 19:17

You need to consider the wheel and tyre combination together, not the wheel separately. The important thing is to maintain the same rolling radius between wheel/tyre combinations. So a 15" wheel with a given tyre - say 205/60 - would be replaced by a 215/55 16 or 225/45 17 combination. All three will have roughly the same diameter and thus maintain speedo gearing and so on.

Whether he tyres will cost the same is entirely another matter :D
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Re: Opening "A can of worms"?

Postby chipp » Sun 13.08.2017, 19:59

I stuck a set of S2 wheels on my first SE and could feel the difference in the handling straight away. There felt like a lot more weight on each corner so I changed them back.
I believe the S2 had some extra strengthening in the suspension set up that is not present on the SE and it was noticeable with the newer wheels.
If you are thinking of changing to a larger diameter wheel and tyre, maybe take some consideration over the combined weight as well.

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Re: Opening "A can of worms"?

Postby muley » Sun 13.08.2017, 20:00

The thing is: the 17" wheels with an offset of +? 42 mm stand prouder by approx 15mm so look like they are filling the arch better. Even though rolling radius is similar.

Phil's solution looks good IMHO.

Cheaper, too.


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Re: Opening "A can of worms"?

Postby Elanlover » Sun 13.08.2017, 20:35

I had custom 17" wheels made with the correct offset some years ago. They look great and handle lighter than stock. Yes, lighter. The tires are sized accordingly such that the circumference is roughly the same and the speedo reading is still accurate. If you search the forum you'll find a link to a website that allows you to calculate the correct tire size needed for an increase in wheel size to keep the circumference roughly the same.
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Re: Opening "A can of worms"?

Postby Readit » Sun 13.08.2017, 21:23

So filling the wheel arches better is only achieved by changing the wheel offset or by using spacers.

If the offset stays the same and tyre profile is reduced on a larger wheel to keep the rolling circumference the same, then the gap to the wheel arch would stay the same.

Phil also pointed out to me that if you go for 17" wheels then the existing brake discs look puny, but if you upgrade to larger brakes, there is no going back to original wheels.
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Re: Opening "A can of worms"?

Postby Elanlover » Sun 13.08.2017, 23:32

Depends on what you mean by "filling out the wheel arches". If you mean making the wheels look "bigger" in that they now seem to be closer to the contour of the arch then you're not likely to do that with larger wheels. Going to a 17" wheel but then reducing the profile of the tire so its the same circumference (and the speedo, etc. still work properly) means they still have the same circumference as stock - it's just that there's more wheel and less tire. If you want to fill out the wheel arch this way it's best achieved by lowering the suspension IMHO. If you want them to stick out more from the hub and out into the street (yes, an extreme example) then spacers or new wheels with an offset less than +60 will do that. But why would you want that? It looks decidedly non stock (no offence to those with +45 offset wheels because that's the closest we can get to stock with off the shelf rims) and you run the risk of the tire rubbing harshly against the bodywork causing any number of problems.

I went slightly wider than stock with mine and I think I'd prefer to go even a tad wider if possible. The rears should be no issue but the fronts might foul on the brake lines or other goodies in there. I went with 17x7" wheels and kept the +60 offset. This means the wheel sticks 1/2" further inboard and outboard (1/2' on either side of the hub). No issues so far and I think a 7 1/2" or possibly 8" wheel might have been ok.
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