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Jaguar XKE Tech Tips

Many of following tech tips were compiled from the member's of e-type Digest from jag-lovers.org. There are no implied guarantees. These suggestions are from other XKE owners on how they solved similar problems or challenges and may illustrate varied and occasionally contradictory conclusions to the same problem. Please forward any questions, comments, criticisms, or suggestions to mhicks@mathe.com. Commercial use is strictly prohibited. Ó Copyright 1998 by Mark Hicks. Legal Restrictions

Tires & Wheels

Tire/Wheel Problems

Tire Specs and Brands

 

Protecting your Wheel's Spokes & Splines

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Tire/Wheel Problems

TIRE RUBBING - INCORRECTLY INSTALLED BUMPER STOP

There has been much discussion over the months as to whether the 205/70/15 tires will fit a Series 1 without rubbing the rear rubber bump stops. Some say they fit, others have removed their bump stops due to rubbing. Well my 205/70/15 Goodyear Comp T/A's fit my old '66 OTS, but the same tires didn't fit my new ' 66 OTS. Both cars had replacement bump stops. It turns out that the replacement bump stops I purchased from BAS have a 15 degree angle, and they have to be turned inward. Sure enough, I had them both turned inward on my old car, and I mistakenly had them turned outward on the other. A quick turn to the inside, and now the tires clear the bump stops on both cars. The 15 degree angle isn't noticeable unless you look for it. I suspect that all dealers supply the angled product, we just have to pay attention.

 

Tires Specs and Brands

ARE YOUR TIRES TO OLD TO BE SAFE?

Always replace your tires every 5 years even if they look good. Rubber does not age well and hardens, dry-rots, cracks, and otherwise decomposes over time. A perfect looking tire can destroy itself at highway speeds. Don't Risk It!

To find out the age of your tires, look for the letters "DOT". On the end of the same line, you'll find three numbers, for example "417". This means that the tire was manufactured in the 41st week of the year '97. (Remark: Don't know how to tell "1987" from "1997" etc., but as far as I remember, it has something to do with the little sign which follows the three digits. On my '97 Dunlop tires, it reads like a < (small arrow/triangle, pointing to the left).

CONCOURS SPECS

The "Offical" JCNA National Concours D'Elegance Rule Book lists the following as the correct tire size for E-Types:

 

I) XKE Series 1 3.8 & 4.2 -- 6.40x15

II) XKE Series 2 185 x15

III) XKE Series 3 E70x VR15 (205/70xVR15 -- under old system an "E"

Aspect ratio tire is a 185, but 205 is correct, as the industry standards changed in the 70's...only a 205 tire is correct. If you order tires and ask for an "E" ratio, they will try to order 185...thatís wrong, use only a "205")

The "Red line" tires are O.K. for Series II cars. However the "rule" book notes that 185 x 15 radials "did not come with a side aspect ratio molded into the tire. It was however a 75 side aspect ratio tire. The 75 aspect ration is no longer an industry standard. Use either a 70 or 78 aspect ratio. Goodrich and Michelin are sources.

The "book" also notes that "Wall or stripe/color is optional." On the other hand, if you aren't concerned with being perfectly "authentic" then try radials on the older models...you will "lower" the car slightly and as has been noted, get a misread from you speedometer. But, the car will probably handle much better.

 

WHAT KIND IS BETTER?

It is my belief that wider tires are better on dry roads, narrow on wet. I think that wide or narrow, a tire puts roughly the same number of square inches of rubber on the road. The important difference is the shape of the patch. Wide tire, wide patch, better lateral control for dry handling. Skinny tire, long patch, better traction for the wet.

Radial tires give it up all at once, bias tires lose grip a little at a time. This is why bias tires work in a drift: you have aural input to help you through the curve. Try Hoosiers or Mickey Thompson's if you want a

high-performance bias ply tire. Mickey Thompson Indy Profile's have been made in the same molds since 1966, so you have a modern tire with a vintage design.

New tire should have the same circumference as the old tire to avoid speedometer error. My favorite tire size calculator is at:

http://www.miata.net/garage/tirecalc.html

Most old-style tires were 75 or 80 profile. Don't assume that your new tires are new. Tires can sit on the shelf a long time waiting for a buyer, especially the specialty tires many of us use. In the United States, every tire has a Department of Transportation code, which looks something like: DOT DBUA A44 414 GCD 415. The last three digits are the date code. In this case, 415 means the 41st week of 1995. Don't pay for a new tire which has already spent half it's useful life in the back room!

Tubes suck, unless they are punctured, in which case, tubes blow!

Check your spare. A lot of us are carrying vintage spares, which would probably be worse than useless if you actually had to use them. Save the old spare for show, get something safe for the driver.

 

WIDER IS BETTER?

OK, I guess you want more rubber on the road. So do I. Here goes: I currently run 225/60 x 15's on the car. Not a problem. I want to get sticky high performance rubber, but no can do with a 60 or higher profile.

I'm not talking about really good tires, but ultimate tires. However a 50 profile makes the Jag a low rider. Does not fill the wheel well, looks gross. So, I ordered ONE wheel 7" wide. Now, this wheel is a 16" wheel, so it will look pretty close. You can fit a 45 profile 235, possibly 245 tire in there. Very tight fit. The wheel needs 1/4" offset exterior and 3/4" offset internally. Certainly a 6.5" x 15 wheel fits.

 

VARIOUS 2 CENTS ABOUT TIRE CHOICE

  • If you're going to really drive the car, buy performance 205/65 15s and live with the loss of less than 0.5" ground clearance and an inaccurate speedo. I've got Dunlop D40M2s on mine and they're outstanding
  • Mines' got 225/70-15 Dunlop SPs(very old) on 15x5.5 comp wires (tight fit) and one day will have 225/50-15 on 15x7 alloy wheels. None of this is even close to original.
  • On the various conversations about E tires, I was going to offer that my 195x15 Metzlers are just great, aside from occasionally sliding on decreasing radius turns :-) but realized although I have only 5K or less or them, it's been 10 years.
  • My ' 66 E-Type also has the 215/70-15 tires, and they also slightly rub in the same area you describe. We both have tires that are at least one size too large for optimum handling. After vintage racing and autocrossing for the past 18 years, I 've learned that wide tires help only to the point that they fit the wheels/rims. Our wheels run best with the 195 or 205 series tire. The 215 sidewall will flex too much due to the tire being so much wider than the 5" wheel. This causes the outside edge of the tire to "roll over" onto the sidewall edge during hard cornering. The 205 tire will have better sidewall support, thus placing a bigger "footprint" on the pavement than the wider tire when cornering. Of course, a wider wheel and\or lower profile tire will provide better results.
  • I've got Dunlop 205/65s on my 67 E-type OTS (S1.5), on a set of original wire wheels in excellent condition. I drive the car regularly and aggressively, and have detected no tire rub or truing problems with the wheels. The performance improvement with these tires relative to 185s is remarkable and cannot be underestimated. Obviously you must accept the impact the tire change has on speedometer accuracy - a small price to pay in my case, anyway.
  • Using a formula found in Discount Tire Center's web page http://www.tires.com I figured that a change from my original Michelins to a 205/70VR-15 would decrease my tire revolutions per mile from 850 rpm to 790 rpm. This would indicate that 65 mph on the speedometer would be an actual 70 mph and that my original 3.51 axle ratio would become an effective 3.30 axle ratio.
  • I have 205/70 VR 15 Pirelli P5 Cinturato on 6,5" spoke wheels on a '66 Series I 2+2, fit & run w/o any problem.
  • The factory service manual for the 3.8 E-types specifies a 6.40 X 15 size, which translates to 165 X 15. So there is no way to determine the aspect ratio for the early tires. My 1964 3.8 FHC, serial number 890630, was a transitional model manufactured just before the introduction of the 4.2 (door arm rests, vinyl facia covering, etc.). I suspect that the 4.2 E-types were the first to be equipped with 185 X 15 tires.
  • My ' 67 Series 1 has Michelin 185 r15 Redline tires, with 8/32 " tread, that have a circumference of 84 1/8 " when jacked up off the ground, and inflated to 32 psi. I also have a "street" set of tires I use on older wheels for driving ( that way I never have to clean the "good" set). They consist of Goodyear Comp t/a's, 205/70 r15, which measure 82 1/4 " in circumference with 7/32 " tread, when jacked up, with 32 psi. Since the difference in circumference is only a difference of 2 %, I assume that the speedometer difference between the two sets of tires is also 2 %.
  • The original E wires ran 5 and 1/2 inch rims....205 Series tyres fit, but this is probably the limit. Series III E Types have 6 inch rims so you can move up in tyre width again.
  • I use the 225/50s on my road car and on the race car we use the 3" bore which we have pressed down to a rectangular shape for clearance purposes. Be aware that when you put the 225s on you will be straining the capacity of the car's limited width to handle that much rubber... inviting bump and radial steer. We have used different uprights and the GTJ steering arms to balance this effect and we have put back the mastic mountings for the rack to absorb some of the tire steer...
  • Just returned from Discount Tire with 4 new 205 70 vr 15's and new tubes.
  • My 1964 3.8 FHC currently has 165-15 Michelins that are to be replaced by Vicarage with 105/70VR-15s by Vicarage. I was the third owner and it had 165-15R Michelin X tires when I bought it in 1969. I replaced them once, again with 165-15s.
  • British Wire Wheels sells wire wheels for tubeless tires. They seal the spokes with some kind of sealant - it works, cuz that what I drive on.
  • I run 225 60VR15 Dunlops. These are great handling tires, and seem to wear well. There is no noticable interference with the bodywork, but don't try anything wider. I think that many of the reported interference problems are the result of incorrectly adjusted torsion bars.
  • Vicarage recommends 205/70 VR or HR 15s and suggests either Michelin XV (?) or Bridgestones. Tire Rack and Discount Tires (Road & Track current ads) list very few 205/70s, either VR or HR, and none for Michelin. My choice would be a VR rating, but my budget is in the $100 range per tire so I may have to go the HR route. I'm leaning toward the new Pirelli P6000 Sport Veloce that got a very favorable review in the November Roundel (BMW) November issue. There is no 205/70 size for the P6000 listed, however. Am I correct in assuming that a 70 size offers slightly more road ride height than a 65 designation? Bridgestone has a Potenza RE71 in my size VR rated plus the Turanza EL60, also VR rated and 205/70-15.
  • BFG (BF Goodrich) makes them in 185/70VR15, for about $130 each. That's what I'm going to try. Now, I'm planning to autocross the car from time to time, too. Disadvantages are: Very poor wet characteristics, especially if there is any standing water. But I won't drive in the wet. Short life: Treadwear rating of 60 means ~ 10,000 miles max -- but I won't put that many miles on in 5 years. They may not be available long -- some of their lists no longer show this size, but my store says they can still get them. They will only sell them to registered "Club T/A" members, but this is a formality.

 

TIRE PRESSURE

I'm assuming that 1 "atmosphere" = 14.7 lbs at sea level. Then 2.3 atmospheres = 33.81 pounds of pressure. I believe most of my car's service manuals say around 32 - 34 pounds for high speed driving so this sounds about right. Use the 14.7 number to convert to atmospheres.

 

TO SLIDE OR NOT TO SLIDE?

Recently I was conversing with a very knowledgeable Jaguar technician and professional race driver. He swears that the E-type with bias-ply tires will easily outhandle one fitted with modern radial tires. Furthermore, he says that the wider tires often recommended today actually hinder handling in the XKE. His opinion is based upon years of experience on the track and on the street and, while too complicated for me to follow, is rooted in the premise that the E-type was meant, for optimum speed around a curve, to slide through the curve. He points out that wide radial tires make the rear end stick in the curve which does

not allow the oversteering Jag to use its torque to push the car on through. I have done a pitiful job describing his elaborate explanations of the physics involved, but I must say that I was both impressed and confused. It goes against current belief.

The handling superiority of bias-ply tires re E-types has been cited in various articles and books, most notably in mags such as Classic Car & Automobile. At straight-out speed, though, I should think the radial tire would have a greater margin of safety. If Dunlop 6.40X15 bias tires were available at a reasonable price (Coker lists them for a king's ransom), I'd put them on in a minute. My car originally had the Dunlop bias-ply tires and handled much better on twisty roads than the Michelin Xs that replaced them.

 

Protecting your Wheel's Spokes

Never use grease on your wheel splines. When heated the grease liquifies and proceeds to leak through the hub to your spokes coating them and collecting dirt. Instead use anti-seize compound, the same silver substance you use you your spark plugs. It won't liquify, won't make your wheels dirty and guarantees ease of removal in the future. A very small amount gets the job done.. Rule of thumb, about the time you think you've put on enough anti-seize, you've probably applied too much.

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