Tyres and wheels for the Elise Mk1

Summary

There is general agreement that the Pirelli PZero tyres fitted as original equipment to the Mk-1 Elise are deficient in wet-weather performance, by comparison to more recent tyre designs. Elise owners should consider using replacement tyres from Bridgestone (Potenza S-02 PP), Goodyear (Eagle F1 GS-D2) or the Lotus-supplied Yokohama Advan Neova LTS. The focus of this document is on replacement or substitute tyres for use on public roads, rather than racing, and the use of the original Lotus rims, not their replacement. It explains some of the key measurements used to describe tyres and rims, some options for choosing new tyres, the available replacement products (as at May 2002) and some of the feedback on the above three, most popular makes. Note: This document is specific to the Elise Mk-1.

Disclaimer

This information in this document is drawn from many different sources and the author disclaims all liability arising from the accuracy of content, and reliability of any recommendations. This document is not authorised or endorsed by Lotus Cars Ltd., and is entirely independent of any vendor, or service provider. It was written in January 2001, and revised in May 2002 (to reflect feedback on the Yokohamas) and obviously, new products, feedback from owners, and testing by Lotus themselves may occur after publication, and supercede the information in this report. Introduction 

The consensus seems to be that the PZero was a good tyre in its time, but that it's wet-weather roadholding is now inferior to newer brands. In the dry, the PZero has better dry traction than many other tyres, but tends to lose it more suddenly - particularly disconcerting for the 'average' driver. Most owners would prefer a tyre which give more 'warning' of traction loss. The problem until recently was that almost all substitutes (for use on public roads, as opposed to track racing) suffered to a degree from the problem of being designed for much heavier cars. Entirely suitable for mainstream vehicles, many brands did not transfer well to the much lighter-weight Elise. As an interim, Lotus tested and endorsed the Bridgestone Potenza S-02 PP for the Elise in 2001 (but used a different Bridgestone - the RE030 - for the new S2). Finally, in 2002, they plumped for the Yokohama Advan Neova LTS as the standard replacement tyre for the S1. Note that this is only available through Lotus garages - beware of any tyre dealers who say they can supply Yokohamas for your Elise but that the 'LTS' suffix isn't important - it is. 

This illustrates the point that different owners use their cars in different ways. Some Elises are used for track-racing, as well as on public roads; some are used as daily transport throughout the year - others are only taken out of the garage in the summer; some owners are happy to renew tyres annually if that means the optimum grip - others will compromise performance to reduce cost. So what you have to do before deciding on the best replacement tyre is to decide your priorities and preferences. For example: 

Do you have 7J (Standard), 7.5J (111S) or other-sized (Exige) rear rims; Is the car used most days, or mainly just in the Summer?; Do you tend only to take it out in good weather? ; Would you like to be able to drive safely in snow?; Are you prepared to renew tyres after as little as 8-10,000 miles in order to get the best performance?; Do you use the car only on public roads?; Does the car take part in any track-days, racing, or airfield days?; Are you prepared to buy new wheels, as well as new tyres? 

It is also worth taking a bit of time to appreciate that tyre designers have to satisfy a set of conflicting technical requirements, all within the cost and production limits of manufacturing. Some of the target requirements include low wear; high adhesion; predictability; good feedback (especially near the limits of adhesion); good cornering; low rolling resistance; resistance to aquaplaning; wet roadholding; comfort; low noise; resistance to kerb scrapes; and so on. Clearly, some requirements are in opposition - such as low wear versus good adhesion. Some are more subtle - resistance to aquaplaning actually conflicts with good wet cornering. Some are quite challenging - such as ensuring the tyre behaves consistently as the tread wears (especially in the wet). Really, the questions above are trying to get you to clearly define what sort of tyre you want, in respect to these technical characteristics.If nothing else, you have to appreciate that you'll always have to compromise in some way or other, even if cost is no problem. 

Nomenclature of Tyres and Rims 

Physical Parameters: Tread-width,Height, Diameter and Bead-width 
 

FIG.-1: KEY TYRE MEASUREMENTS

There are two elements to the wheel - the tyre and the rim. The tyre is usually sized using the  tread width(W) in mm.;  sidewall height (H) in mm, plus the;  tyre's insidediameter (D) in inches.    The rim is also sized using the same diameter (D).In addition, there is a second measure of width, which the average customer never comes across. This is the Bead-Width (BW). It is the distance between the lips of the tyre (called beads), where it fits on the rim. It is usually about 10mm less than the tread-width, and corresponds to the second key dimension of the rim - the rim width (J ).

Tyre Specification

Tyres have these key values embossed on their sidewalls. What causes a lot of confusion is that various other important values are also listed. The format is standardised as follows 

{tread-width-in-mm}/{aspect-ratio-%}-{type}-{diameter-in-inches }-{max.load rating}-{max.speed code} 

So '205/55-R-16-81-V' means: 205mm tread width 55% aspect-ratio (sidewall height is 55% of tread width)  Radial build

Diameter of 16 inches. 

Load-rating of 81 

V-Code indicating maximum sustained speed (V=149mph/240Kph max.)

Aspect-ratio The sidewall height ('H' in Fig.1, is not quoted as such. It is used as part of a formula representing the aspect-ratio of the tyre, basically the height (H) as a percentage of the tread width:

Aspect-ratio (A%) = (Height (H) / Tread Width (W)) * 100 

Thus a 205/55 tyre has a 55% aspect ratio, where the sidewall is 55% of the 205mm tread-width. In which case the sidewall would be 112.75mm. But no one ever quotes this value - only the aspect-ratio%. 

For example, the standard Mk-1 Elise rear wheel is a 205/55-R-16 (width 205mm, height is 55% of the width). The same 7"-wide rim can take a wider tyre, i.e. 225mm, but the aspect ratio has to be adjusted to compensate, and becomes 45% (i.e. a 225/45-ZR-16). The front-wheel on all Mk-1s is 185/55-R-15, but some owners will fit wider front tyres(usually 195/50-R-15) where they want the same tyre all-round, because the manufacturer doesn't produce a tyre as small as a 185/55. There is a limit to how far you can go with this, because at some point the rim simply can't carry the fatter tyre. Either it's going to come off the rim, or seriously affect the handling in some way, and/or scuff the wheel arches. Generally, you can't readily increase the width by much more than 10%. 

If you opt to fit the Bridgestones or Yokohama's to the front of your Elise, you will have to resort to using a wider tread, since they aren't available in the original equipment size of 185/55-R-15. The replacement will be a 190/50-R-15 (10mm wider, 50% aspect ratio). This will affect the handling and you may take time to adapt, even 'though the overall effect may be to improve the car's handling. 

Speed Rating: The following tyre speed categories are suitable for fitting to the Elise: 
 

Lower ratings - 'N','P','Q','R','S', and 'T' are not. 

Rims:{width-rating}Jx {diameter-in-inches} {rim speed-rating} {offset-distance-in-mm} 

Rims are described using two key values, the rim-diameter (D), and rim-width (J) measured between the flanges where the tyre actually attaches to the rim by its beading. This is measured in inches, and suffixed by a 'J'. The rim-diameter (D) is the same measurement as the tyre's diameter (D). Thus a '7½J x 16' is a rim of7.5" width and 16 ins. diameter. 

FIG.-2: KEY RIM MEASUREMENTS

The 'J' classification was defined in recognition of the fact that the same rim width can happily carry a range of tyre widths. In general, you can fit a tyre whose bead-width ('BW' in Fig.-1) is between ½" less and 1½" more than (J). So 7½J means that you can fit a tyre whose bead-width is between 7" and 8½". The bead width is usually about 1cm less than the tread-width, so a 225 would have a bead-width of 215mm. 

In the case of the Elise 111S, Lotus replaced the 7J wheel used on the Standard model with a 7½J wheel when they decided to fit 225mm tyres as original equipment. This wasn't strictly necessary, but clearly they felt it was a better match in terms of handling. 

Speed-rating: I haven't bothered to research this, since I'm assuming that Lotus have chosen rims, which are suitable for the Elise in the first place. If fitting new rims, you'd have to check on this for yourself. 

Offset: Elise rims are offset - the point at which the rim is attached to the hub is offset from the central plane of the rim (see above). This is absolutely critical to how the suspension is set up and tuned. If you change this offset, you'll need to change the suspension. You may even find that a different rim is unusable. Be wary of anyone offering replacement rims who doesn't discuss this issue with you. 

Pitch Circle Diameter This is the circle described by the bolts as they rotate around the centre of the hub. Even if you have the right number of bolts in your new rim (yes, it's been known ..) the pitch circle diameter of the new rims has to match the hub. The bolts will also have to be of the right length etc. as well. Yet another complication to changing rims. 

Up-stepping: This term is used to describe the situation where you preserve the same Outer Diameter of the wheel when increasing the tread width (W) and decreasing the aspect-ratio (A) by changing the rim diameter i.e. buying a new, wider-diameter rim. The reason you might do this is in order to preserve key handling characteristics, while getting the benefits to using a lower aspect-ratio.See Fig.-3: 

However, it means a complete replacement of the rims. This may be an option for owners who are serious about racing, and interested in fitting a completely separate set of wheels for competition use. Again, you'll need to discuss this with a specialist in racing modification, and have a pretty clear expectation of the exact benefits to be gained - which neatly leads us into the question of new rims. 

New Wheels?: Personally, I don't recommend you change your rims for public road use, unless you have a very clear idea of the precise benefits that you expect. It's normally done by someone who races their car a lot, and is looking at a range of advanced and expensive refinements. Generally, changing the rims is best undertaken in conjunction with a number of other changes (such as revised suspension, engine tuning, replacement exhausts and so on.). There are lots of people who will be happy to sell you £2,000+ of new rims carrying £500+ of new tyres. For competition vehicles, it may be justified, but for the average road-car, it may be just a waste of money.One exception is if you need winter tyres: 

Winter Tyres 

The Elise is not at all suited to being driven in snow or slush. A few owners have used winter tyres, and reported very favourably on the difference they make, particularly where the Elise is their daily transport. These may well be a good alternative to buying a second car for the winter 

If you want to fit winter tyres to the Elise, Lotus insist you must use 5½Jx15 rear rims i.e. use the same rims on the back as on the front. There's no way that you can fit the recommended size of winter tyre on standard 7Jx16 or 7½Jx16 rims. In practical terms, it's likely that you'd have an additional, separate set of rear wheels if you opt for winter tyres. You may also opt to have a separate set of front wheels as well, for ease of replacement. This document doesn't include much information on winter tyres for the Elise - you should talk to both Lotus and a specialist distributor if you opt to use them. 

Snow Chains: Lotus only endorse one specific snow-chain product, for use solely on the recommended winter tyres. Again, you'll need to refer to a Lotus garage on this. 

Main Replacement Brands

• Bridgestone Potenza S-02 Pole Position (PP): The most widely-used alternative to PZeros.
• Goodyear Eagle F1 GS-D2: Derived from F1 wet-weather tyre. Used more in Germany/Benelux.
• Yokohama Advan Neova LTS: Derived from 340R and various track tyres. Specific to the Mk-1. 

Also have a look at the UK tyre industry public website http://www.tyres-online.co.uk/. This includes a compilation of all the main tyre reviews published in magazines across Europe and other useful information. However, they themselves say that you need to appreciate that different drivers will have different requirements and expectations. Many of the reviews seem contradictory at first.

Feedback from Owners & Magazine Tests

This section summarises the feedback on the three main replacement tyre products currently chosen by most Elise owners. Each description summarises the plus (+) and minus (-) features from the main magazine reviews across Europe, with the review date. To be honest, some of these are contradictory, perhaps reflecting the variation in priorities of the different reviewers. 

Pirelli PZero Good wear and good dry road-holding. Tendency to grip well in dry, but suddenly lose adhesion, when the traction limit is exceeded. Some comments that they need a while to warm-up. Complaints are mainly over relatively poor wet-weather road-holding. Tyre dealers view the Pirelli as a dated design, superceded by other models: 
 

Bridgestone Potenza S-02 Pole Position (PP) Very positive reports from all owners who've tried them. Far superior wet-roadholding to the Pirelli PZero. More progressive break-away at the limits of adhesion. Some indications that they are not the leader in dry roadholding or feedback (albeit by a small margin). However, not in front-tyre size of 185/55 - you have to fit 195/50 size tyres instead (this is tested and approved by Lotus). The most common replacement brand in the UK during 2000 but superceded by the S-03 in 2001, with the latter apparently both in short supply, and getting more mixed reviews Magazine tests +Overall handling -Dry handling (Max Power Dec.98) +Wet handling -Noise, rolling-resistance (Autocar Nov.99)  +Handling, anti~aquaplaning-Oversteer in wet (Sport Auto, June 2000)

Goodyear Eagle F1 GS-D2 A popular replacement in Europe, especially Germany and Benelux. Good reports in terms of superior wet-weather adhesion compared to PZeros, and somewhat longer-lasting than the Bridgestones. On a par with the S-02 in most other respects. Tends to come a close 2nd in magazine trials.  Magazine Tests: +No.1wet handling -Dry braking (MaxPower Dec.98);  Ditto (Autocar Dec.99); +Wet-handling, anti-aquaplaning -Dry braking, Average handling (Sport Auto March 2000)

Yokohama Advan Neova LTS Supplied exclusively through Lotus garages. More 'supple' deformation and more progressive 'drift' under cornering loads mean more predictable handling. More gentle ride. Far superior wet-weather handling compared to the PZeros. Lotus rate this as the best tyre for the Mk-1. However, some owners have reported difficulty adapting to the change from PZeros, and feel that, in the dry, the LTSs are prone to reduced feedback, and distance the driver from the underlying road conditions. Wider fronts seem to initially give perception of understeer (sic). I recommend fitting by a specialist high-performance tyre dealer, and strongly recommend having a full geometry check and adjustment at the same time (about £60-£80). No indication of excessive wear on public roads, but perhaps not best-suited to track racing, where feedback indicates that they wear more rapidly. £425 a set of four.

Useful Websites 

http://www.tyres-online.co.uk/

www.bridgestone-eu.com/

www.goodyear.com/uk/tyres/