Lotus Elan

Modern Tyres & Under Gearing !

PostPost by: Verve » Mon Feb 10, 2020 11:00 am

Hi All ,

I don`t know who else has checked this ... but the modern 80 profile tyre is noticably shorter in height ( Rolling Radius/Circumference ) than the original spec` tyres of the same size , that were fitted to the cars in period .... despite me being told by garages that they are the same ...

I know there are "Manufacturing Tolerances" ... but when we physically stood an inflated , original Dunlop spec` tyre against a modern equivalent ... the difference was obvious ... which naturally causes even more engine rev`s out on the open road ...

This was even more evident last week ... when a good friend , had a lovely new set of Super Dougal`s ( of Highly Recommended Longstone Tyres ) original spec` Pirelli Cinturato 145`s fitted to his S3 Elan ... & the new period 145`s again , were even taller than the modern 155/80`s he had just taken off !

This is good news for those wanting to get the rev`s down ( particularly with the 4 speed box ) on the S1-S3`s ... & I suspect the new mega Michelin period 155 or 165 XAS will have the same effect for the later cars !

I have got around the problem on my S4 ( which has adjustable suspension ) , by simply fitting a 165/80 modern classic tyre on the rear .... which according to a tyre calculator , makes it virtually identical to the original gearing of a period 155 : ) !

This makes my Elan even more pleasurable to drive on any journey , even with just a 4 speed box ... just like they did back in the day !

Paul.
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PostPost by: dougal cawley » Mon Feb 10, 2020 5:37 pm

Hi

Can i just say, that there is a lot more to it than simply the diameter. Really the diameter will help the looks by filling the wheel arch, but the effect on gearing will be not be huge. Even if there is an inch difference in diameter (which i doubt, in theory it should be 16mm not 25mm), you are looking at about 4% in your gearing. so the same revs that did 70mph now does a bit less than 73mph which i guess is something.

I don't know what a "modern classic tyre" is, but your car will have nicer handling on a 155 than a 165 (of the same carcass structure). yes it will give a softer ride, but the steering will not be as fast, precise and responsive. sorry there isn't a cheep way round it. My recomendation is to stick to the correct size tyre, but fit a proper classic carcass. For now that is XAS for the 155 & 165 and Pirelli Cinturato for the earlier cars. (However there is good news for the later cars, in that i hope to get Pirelli to make a 155 and 165 this year and i hope to keep the price good).

Paul,

I bet when you talk to our freind who made the change to the Cinturato, you will find that he says the handling is miles nicer. That is because of the carcass. It will be much nicer to drive than on his old tyres, and that is the reason to buy the good stuff.

I am sorry if it seems like i am pulling your post apart, but it is miss guided to think there is a modern tyre answer to what is wanted for an older car. The build in a modern cars is so different, they want different things from their tyres.
dougal cawley
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PostPost by: Verve » Mon Feb 10, 2020 8:32 pm

Hi Dougal ,

Sorry , I seemed to have tricked you ... I totally agree ... and massively support the use of original spec`/size tyres , for exactly the reasons you say ... particularly your Pirellis & Michelins ( I`ve had a set of brilliant XAS`s on another Elan : ) ... and cost should definitely not be an issue on our fantastic & valuable Elans : ) !

I was just reporting what we seem to have found , as another adverse effect of fitting modern rubber with an 80 profile , by further spoiling the "gearing" .... which is already compromised on our Elans with only 4 speed gearboxes ....

I`m sure Rob will be delighted (as soon as the weather allows ; ) , in the finer handling of his S3 Elan with your superior 145 Pirellis on .... and the improved gearing will be an added bonus as well ... especially if you bear in mind he could have had modern 145/80`s on previously , instead of S4 spec` 155/80s ....

As for my S4 ... yes , I have retained 155/80`s on the front for the steering ... I have only increased the rears to 165/80 to get the gearing correct (as my adjustable suspension allows me to do so) ... using Vredestein H Rated Tyres with the Classic Profile ( which I think are no longer available and you used to sell ? ) ... but the gearing improvement ( recovery ) is noticeable & very welcome : )

However , it will be FANTASTIC if you can get the Pirellis back in production , in 155 & 165 spec` for the later cars ... there is a definite gap in the market there ... and it will be nice if they improve the gearing as well : )

Please keep us posted : ) !

Paul .
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