tire dimension confirmation

[Chrisrich]

Hello folks.
I'm wondering if someone can confirm a tire dimension for me.
I'm told the Michelin XAS 155/13s are 23" in diameter. I'd like to use these tires (found a set), but I've already gone from Verdenstein 155s (23") to 145s (22") to make the clearance I need at the front.
(Meanwhile, I think the Verdensteins REALLY lack grip, so I'd like to upgrade)
I wonder if someone could measure and confirm that for me -- it'd be a big help.
I can't find a set of XASs in 145 size.
Any other suggestions for a good replacement tire at 22" in the US?

Thanks much-

chris

[oldelanman]

Hi Chris,
Check out this site.......
http://www.tyresave.co.uk/tyresize.html
If you know the tyre size and aspect ratio it will calculate the overall diameter.
Regards,

[SADLOTUS]

Also, check out this site

http://www.carbibles.com/tyre_bible.html

about quarter way down, page two

[msd1107]

The online tire calculators give you a geometric calculation, which may or may not be useable.

Carbible at least applies an industry standard correction (or at least he knows about it.)

Go to one of the on-line tire retailers (unfortunately TireRack does not have the XAS). Look up the tire manufacturer and tire. They should have a clickable link for technical specifications. Usually, tire diameter and rev/mile figures will be available.

Note that the tire size and rev/mile figure can vary between manufacturers, even for the same tire size.

And you can always remove some material from the inside of the wheel wells to get the last fraction of clearance needed. That is how I got my 185/70-13s to fit.

David
1968 36/7988

[andyelan]

Hi Everyone

I think manufactures sizes are really only nominals. I have Goodyear GT2s on my Plus 2 but the spare is a very old G800. All are 165x13 but there's a noticeable difference in overall diameter and width between the two types

Andy

[msd1107]

Andy,

Exactly the point.

I have a spreadsheet that collected the rev/mile data for all manufacturers for various tire sizes. It averaged the reported rev/mile data.

However, that does not deal with the specific situation where, as you point out, different tires (even within the same brand) are constructed differently and have different tread widths, diameters, sidewall widths, and rev/mile figures.

And if that was not enough, we do not know under what conditions the manufacturer reported their data. Was it for a new tire, partially worn, or worn.

Many new tires have a tread depth of 10mm or greater. This means the diameter of the tire will change by 3/4" or more during the life time of the tire, not even taking into account inflation pressure.

And then we have the variability of the cars. There are members that can run some brands and sizes of tires, but these same tires will not fit other cars.

As I went from 155-13 to 165-13 to 185/70-13, I had to make some small adjustments to alleviate points of interference.

I think that Chris wants to know if the XAS will fit. They will, but it might take a little work. I do not think the diameter is so much the problem, but the tread width and sidewall width. It sounds like he has a S1/S2 which are notoriously more finicky about tire size. But if he wants them to fit, he can make them fit. However, be careful to not go over a bump with the wheel cranked over. You will always get interference.

David
1968 36/7988

[mac5777]

Hi, I just called http://store.coker.com/product.php?prod ... t=0&page=1
and they said that it will be discontinued and they have 13 left.
the Dia. 23 inches----I like the rev reduction
the tread width was 6.2 inches----They will fit my Elan
and $223.00 each plus shipping 4 to CA. was $98.00---- will not fit my budget
Dave, is there any other dealer that might still be handling them?
Sarto

[msd1107]

They have at least 40 of the 165-13 XAS at 23.2" diameter.

Might not be an option if you struggle to fit 155-13s though.

As far as other dealers in the US, I don't know. You would think that with the number of sports cars running on 13" wheels, that they could keep a few in stock. They probably could sell more if the prices was different.

David
1968 36/7988

[paddy]

They have at least 40 of the 165-13 XAS at 23.2" diameter.

Are these 70 section or "no section" (ie 80) ?

Paddy

[msd1107]

All the Michelin XAS FF tires are 80 series H rated tires.

As far as other US dealers, you could try to get them to order through longstonetyres.co.uk who ship world wide.

David
1968 36/7988

[mac5777]

David, I like the 165-13 XAS especially the 23.2" diameter. I did try 155x80x13 and they did touch. Last week at Keith's shop, working on the webers, I measured his Elan and noticed that my Elan was almost 2 inches lower in the back than his. The front measurement was the same as his. Looking at my picture, it appears level and I never gave it a second thought that it may be too low. By installing different springs or shocks might solve the tire size restranints. But this is another topic on how to raise my rear end.

[msd1107]

Sarto,

Measure the height of the driveshaft coming out of the differential, and the height of the center of the wheel. These should be the same or you will have power losses through the drive train and camber gain/loss.

I didn't notice anything unusual with your car when I saw it. But it could be that yours is a little low and Keith's is a little high.

Even with optimum suspension height, you are going to have clearance problems on extreme jounce. I removed material from the inner wheel well at the point of interference until it just barely cleared (actually, you probably could stand a small amount of interference under the worst conditions, since they don't happen very often, and the tire and fender are flexible enough to adapt temporarily).

Good luck. The steering and handling are noticable better with the 165-13 and 5 1/2" wheels compared to the 145-13 and 4 1/2" wheels. It might be worth the effort to get the tires to fit.

David
1968 36/7988

[Chrisrich]

I think if I knew I could get them to fit, I'd bust for the $1k to put the good tires on.
Would changes to the preload on the front shocks do anything to resist touching when the suspension compresses?
I suppose I could go back to my 155 verdensteins (which are also 23") and see if I can get them to work properly, and then try to get a proper set of michelin's (if they still have them).
Tough situation.
Wish there were more options.

[Bruce Crowthorne]

Just measured my Mitchelin XASs and can confirm that they are 23 inch diameter.

One point that you have probably spotted is that they don't fit in the spare wheel compartment, so only buy 4 and either buy a cheap tyre as a spare or use a "get you home can of foam".

By the way, I have an unused spare (I bought 5!) if that helps you
Regards
Bruce

[johnsimister]

Can you get 165/70x13 in the US? I have Dunlop SP30 in this size and they seem ideal. Almost identical diameter to 145x13 but more grip and a good-looking tread pattern which looks right on a sporting car. With a 3.54 diff the gearing is just right. As for ride height, Elans seem better with the nose slightly lower than the tail - better turn-in, and high-speed stability is improved thanks to reduced front-end aerodynamic lift. Various experts, notably Nick Adams of Lotus and John Crook of Paul Matty's have told me this.

Tony Thompson's parts list recommends 165/70x13 as the ideal road tyre.

John