15" wheels; an alternative?

[Splat]

So, I've been giving the 15" wheels question some more thought, and I'd welcome your comments and suggestions on the following..........

I've read everything that I can find on 15" wheels and the Westfield Eleven, most of it by Jan, and it's all good advice. Thank you! But.....

The Dunlop Racing tyres just aren't road-legal here in the UK. If you had an accident, the loss-adjuster sent out by your insurer would pick up on the tyres straight away and you'd be disowned by them. Not good!

Dunlop Racing actually make more than one tyre combination that'll fit the Eleven. The L-section tyre in size 450L15 for the front (with the CR48 (or R6) tread pattern) can be paired with the 500L15 rear (with it's slightly different CR65 tread pattern). The L section tyres allow the figment of quite wide rims.

Alternatively, you can fit the Vintage-section tyre with it's R5 tread-pattern; 450-15 (F) and 500-15 (R). These require much more narrow rims and the tyre is much more square and narrow.

The L-section tyre has been available "forever", but the Vintage-section tyre has been unobtainable for a couple of years now; ever since Dunlop stopped production of it's historic tyre range at Fort Dunlop and moved it to Europe. Rumour has it that the Vintage-section tyres will be produced in Eleven-friendly sizes later this spring.

I was initially holding out for the Vintage-section tyre simply because in the larger sizes (16" and above) some fitments have been homologated for road use. But the 15"s haven't and I've decided that I don't wish to fall foul of the law!

The following table shows the dimensions of all of the 15" Dunlop Historic Racing tyres and the permissible rim widths. As ever, tapping on it will expand it to a legible size!! Notice that the L-section tyres permit much wider rims. I've also included a diagram that explains what dimension is what! The section width is only correct when the tyre is mounted on one particular rim width. Mount the tyre on a wider rim and for every .5" increase in rim width, the section width increases by .2" (and vice-versa for a narrower rim).

[Splat]

So Jan has successfully equipped a number of W Elevens with L-section tyres front and rear. The dimensions of the front tyre seem critical and the 450L15 has an overall diameter of 609mm and a section width of 156mm. I've found a road-legal, radial-tyre alternative with the corresponding dimensions of 616mm and 147mm.

At the rear, the dimensions of the 500L15 are 631mm and 187mm. My alternative is 646mm and 167mm.

The front tyre has a greater overall diameter than the Dunlop, but it's only by 7mm. Or, looked at another way, the sidewall is 3.5mm taller! At the rear, the sidewall of my alternative is 7.5mm taller than the Dunlop, but clearance isn't so much of an issue here (I think??).

My alternative tyres appear to be much less wide than the Dunlops, but don't forget that they are of radial construction rather than crossply. The actual tread width of the Dunlops is much less than their section width. The tread width of the radial tyres is much closer to their section width.

So, the overall diameter of my radial alternatives seems to be very similar to the L-section Dunlop crossplys and their section width is less, even if you allow for growth if fitted to a wider rim.

Here is the spec. sheet for the Michelin XZX radial tyres (obviously the bottom two of the three sizes available!).

[Splat]

So, if the XZX is a comparable size to the Dunlop, what wheels to mount them on? The front is suited to a 4"-wide rim, with a maximum permitted width of 5". The rear is 4.5", maximum 5.5"

I run Spridget splined hubs with 9" discs and MGB callipes at the front and the 1"-wider-than-ideal disc-wheel rear axle with hybrid disc-wheel half-shafts/Spridget splined hubs at the rear (how many hyphens in one sentence?) So, proper splined hubs front and rear, not bolt-on converters.

I presume that the more spokes a wheel has, the greater the loads it can bear and the longer it'll stay in true for? But the Eleven doesn't exactly overload it's wheels, I don't do that many miles per annum (almost 3000 last year was exceptional!) and...... I prefer the cosmetic look of the lower spoke-count! And for that same reason, I'd like to keep the same spoke-count and lacing front and rear, which probably means picking one wheel to serve at both ends.

I think that the two most likely candidates for off-the-peg wheels from MWS are these two. I suspect that the one to go for is the 4.5" width, given that both inset and backspacing are so similar and the tyre will end up in a very similar place. But, as I said at the start, I'd really appreciate the thoughts and observations of others!

[Westfield 129]

Here is what I can tell you from my own experience:

'Doesn't matter if you use the L section or standard section tires in sizes 500X15 and 4.50X15. They both fit. You will likely have different front and rear tread petterns, but you will have tubeless tires with the L, which is a nice thing to have. MWS wire wheels in the appropriate sizes will work with tubeless tires. Quite well, in fact.

Wheel rim widths can be increased to 6" for the 500X15 in either section, and 5.5" for the 4.50X15 If you want to run a 5" or a 4.5" rim for the front and rear, it will work just fine for both sizes. I have done rear rims in 6", 5.5" and 5" with excellent results. Fronts have all been 5"(72 spoke for strength), as the rim is easy to source from MWS, and works on both L and standard section tires. While I too like the lower spoke count, I don't like to be truing rims every year. So far, the 72 spoke have been very reliable, and can mount tubless tires.

I suspect that a 5.5 " front wheel would fit with the right back side spacing, using the 4.50X15 (an approved rim width with either L or standard Dunlop race tire) as the tire is narrow in both cross section and tread width. Narrower than the 13" tires, in fact.

If you go to a larger diameter tire in front than the 4.50X15, it wont fit. Not even 10 mm larger... Not 5mm larger... You will have a problem with the lower body panel behind the front wheel, and the body work, specifically the headlight buckets. You can roll forward, but you can't turn... There will be contact problems with suspension travel up front. You will rip out the headlight wiring and damage the buckets at the first turn.

So, if you decide to go with a 60 series aspect ratio, then stick to a tire that is the same diameter as the 4.50X15, Don't go any larger, as the tire wont fit within the body work.

Vintage 16" rims are not a solution for reasons that are obvious. Weight. width and diameter, even in vintage sizes. Maybe if you had a C type replica...

I have corrected a couple of cars that had 155X15s up front (Michelin ZX) that were too large in diameter, so that is not a solution. Torn up alloy and headlight buckets were the usual damage, generally done on the way out of the driveway. It could be that a 155/15 will fit, but from the late chassis that I have worked on, even a few mm will put the tires into the headlight buckets. You need to fit the tires and check the suspension travek and steering arc to see if you have a problem with the headlght buckets befor you take it on the road. It would be a shame to hit a bump when turning and have your lights go out in the dark.

Possibel Fix:

You may be able to fit the 155s if you move the headlight buckets forward in the bodywork using spacer rings or washers. There should be room under the covers to do this. Also, you will need right angle connectors for the headlights. Wires have to come out the side of the connector plug, rather than out the back.

Feel free to run a 165 in the rear. Plenty of room back there.

Or... you need to find a road tire in 4.50X15 and 5.00X15 (Dunlop Roadspeed bias ply?) from one of the vintage tire specialists.

Otherwise, you are stuck with a 15" 50~60 series tire that will be smaller in diameter than the 4.50, and will need a wider rim... Not really a solution. Potholes will destroy your rims, and the thing wont steer properly.

Front tire width is only about 4", and the cross section is not much wider. Actually, the 4.50X15 is smaller than the usual 165 or 185/70/13 in both tread width and cross section, but only slightly larger in diameter.

If you need to have a road approved tire, then the 15s may not be practical in the UK. That said, I know a few guys that are running vintage race Dunlops on their D type replicas...

[Splat]

Blimey, Jan! That was quick. Were you sitting at your computer waiting for someone to post??

In reverse order. The Dunlop Racing Vintage tyres are homologated for U.K. road use in some popular, usually larger sizes (e.g. XKs and DBs). Hence their legal road use on Cs and Ds. None of the 15s are road legal, so it's a no-go for the Dunlops.

The Michelin XZX is interesting because it's available as a 145R15 for the front, rather than the problematic 155 or greater. The 145 has a diameter only 7mm greater than the 450L15s that you use successfully. That's 3.5mm of extra tyre fore and aft. Will that impinge on the sill to the rear or the headlight to the fore when the 450L15 doesn't? I don't know.

I suspect that I may have to start off with some careful measuring of my current 13" Vredestiens and their clearances and ultimately (maybe) buy a single wheel and tyre for the front for test-fitting?

Regardless, thanks for the reply. Much appreciated. And if you get the opportunity in the near future to look at a 450L15 equipped car and make a judgement on whether or not 3.5mm of extra tyre will fit, it'd be very welcome info!

[Westfield 129]

450L15 is identical to a 450X15 in diameter (24", 609~610mm). No difference. The additional rim width is not a factor at all. It is still narrower than the 165/13 or the 185/70/13. The diameter is the real problem, and the L fits without fouling the headlights, provided you use side wire plugs (I believe that the factory harness has them).

I have installed the 450L on all the cars, as they are tubeless. Rim width chosen was 5.0", which is the measuring rim width used for the L tire and recommended. 5" rims fit the W11 front and rear (any rear axle combination, even with bolt on adapters), if you want only one rim size. Of course, you can use 4.5" rim width if you want to stick to a smaller spoke count.

If you stick with the MWS 5" wide rims, you get tubeless mounting, and some additonal strength in the wheels, which is advantageous with the limited suspension travel.

In the rear I have mounted center laced wheels to get a little more rear track, and to center the tire inside the rear bodywork, using the wire wheel axle.

If you use a disc wheel axle with bolt on adapters, and want a wider rim in 5.5 or 6", you might have to select a wheel with a 90mm or more backside spacing to center the wheel, or stick to the 5" wide rim. If you want to do this, let me know. I have notes on these combinations and can recommend part numbers. The bolt on adapters may give you a little more rear track width, which can make chassis tuning a bit easier, making for a slower transition to over steer. Again, the backside spacing of the rim will be critical to the track and centering in the body.

There are 5.5" rims and a 6" wide rim that will work with the wider axle with bolt on adapters in the back. You will have to do some additoinal research at MWS to find these.

We dont' have regular availability of 145/15 Michelins, so I have not tried them (7mm wider is going to be a problem, anyway, unless you can move the headlight buckets forward). My own experience with the 155s on my Lotus 7 Series 1 America (15" wire wheels on a 7 were the standard setup for those early BMC A powered 7s) was that they were HORRIBLE tires to drive on. Unpredictable breakway combined with not much grip... No fun to go fast on at all. I switched to the bias ply vintage Dunlop racing tires, and the car was transformed into a predictable, fun to drive machine.

My feeling about these cars is that they should be fun to drive first. My own LHD car is still on 185/70/13s, which are a bit too wide, and too sticky (Feels too much like a Caterham), but the car is predictable, and has plenty of power through an LSD to balance the chassis with throttle. While it is still satisfying fun, I still prefer the 15" Dunlops, and will convert to them soon. A bit less grip and the ability to slide around at lower speeds on the local canyon roads. WHEEEEEE!

From my experience, the only way that you can get a good tire for 15" use is to get a vintage 4.50X15 and 5.00X15 vintage style bias ply road tire, or the vintage race Dunlops. Otherwise, stick with the 13s or 14s if there are tires that fit front diameter requirement.

[jonclancy]

A few quick thoughts, Splat:

TonyL fitted excellently-crafted, cut-down headlamp bowls to my car when he built it.

Your LED set up should allow even more leeway.

IIRC, Mark had the XZX fitted to his very quick car. Smaller size, but great performance.

The body may rub on full lock, but not really a problem.

Rears are fine, so only a minor thing to resolve.

Finally, apart from Wobblies, what did the original cars run?

[Westfield 129]

Original Lotus 11 cars ran wire wheels in 4" width, 60 spoke, same as the Elite and the 7 America. I still have one original W11/7 series 1 America wire wheel from my old '57 7 America.

I'd run 72 spoke wheels as they are a bit stronger, and will require less maintenance as they will remain true for many years on the light W11. Also, they are easy to source if you bend one.

A note on caliper clearance:
One thing you will need to do if you do go to a 72 spoke wheel (and some 60 spoke) is to grind the brake caliper face to clear the wire wheel hub. You will have to take down the outside face of the caliper to the relief (that fits the 13" wire wheel hub) so that the larger hub clears. You can also have your 15" wheels laced to the 13" center hubs, but it is just easier to order an off the shelf rim and grind a new relief in the brake caliper to match the larger diameter. You can do this with a disc body grinder, rotary file, hand file or mill. i have had a machinist mill my calipers, and I have also used a disc grinder to make the appropriate clearance. Easy to do in any case.

The tire on the original Lotus 11 were 4.50X15 with 5.00X15 often fitted to the rear only. Any walk through a vintage race paddock will confirm these numbers.

The vintage racers all run 4.50 fronts and 5.00 rears.

I concur on the fitting of shorter headlight buckets or moving the headlights forward to clear the smallest of the 15" XZX sizes in front. but other than the fact that the skinny Michelins hold up each corner of the car and are "legal", they are horrible to drive on if you are in a sporting mood. They lack any predictability, breakway quickly without warning (other than they stop screaming when its too late). Not that much fun when you have a chassis that is basically oversteering.

One trick to making them work a little better is a tire pressure of 20 PSI or less. Maybe as low as 17 PSI. In fact, that is sort of a rule with any W11 regardless of tire choice.

[Splat]

Thanks for the input so far, guys. Jon, would you post a couple of snaps of your headlamps bowls on this thread?

The wobblies were too early for the Eleven, although many were retro-fitted with them. Sports models were fitted with the 4" wide, 48-spoke wires that were standard on the contemporary MG TF and MGA. This still seems to be the wheel of choice for the more original cars.

And, unlike the 4.5", 60-spoke wheels, MWS have a 48-spoke wheel available to be used for trial fitting to cars. So I've ordered a single Michelin XZX 145SR15 which I'll take over to MWS for fitting. They're on the eastern edge of Slough, so I can pop in either before or after work one day. Although I've leave coming up, so it might not be until mid-March, unless the tyre is delivered particularly quickly.

I'll of course update when I know more.......

[jonclancy]

I'll get that done tomorrow...

J