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Anyone tried 275/35R19 rear tyres? - Ride/Handling/Suspension/Brakes/Wheels/Tyres - The Lotus Forums Jump to content
G. Bell

Anyone tried 275/35R19 rear tyres?

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I don't like the slightly stretched look of the stock sized tyre on the rear rim was thinking about going for 275/35R19 rear tyres instead. Given that 275/30R19 is an tyre size option it seems like it shouldn't be out of the question but does anyone have experience of doing this, if so any comments?

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I'd be amazed if anyone could tell the difference, honestly.  Go for it.

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No reason why it wouldnt work. 9.5" wheel width is the same as the 20" rears on the S and the 400.

275/35/19 will increase your gearing by about 2% over what you run today, but that makes it almost identical to the gearing on a car running 275/30/20 rears.

Edited by mik

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21 minutes ago, mik said:

No reason why it wouldnt work. 9.5" wheel width is the same as the 20" rears on the S and the 400.

275/35/19 will increase your gearing by about 2% over what you run today, but that makes it almost identical to the gearing on a car running 275/30/20 rears.

I need to get tyres all four corners in next 3-5 months I predict 

I am ignorant of tech things so I am unaware of the effects you saying in the thread 

to the simpleton like me if on my NA and I will purchase Michelins as recommended

what size best to go for ? I am only road going no track but I guess I am interested more in looks of the on road .  

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Short answer : I'd go for the 275/35/19

 

Longer answer.

I am not a tyre engineer (although we do have a tyre specialist on this forum). Everything from this point on is a bit theoretical as radial tyres deform at the contact patch - by design - to make said contact patch bigger. The amount of squidge will vary according to tyre type/manufacturer (due to construction, rubber compound, and resultant sidewall stiffness), so the theory will not be perfect, but it wont be a million miles off either.

The bigger the diameter of your wheel & tyre combination, the bigger the rolling radius, and therefore the further the car will go for every rotation of the wheel. 

If we set your oem 255/35/19 as the baseline, a 275/30/19 is 2% smaller, and a 275/35/19 is 2% larger in rolling radius.

Who cares?

(It wont be but) lets assume your speedo today reads perfectly. When it says you are doing 70mph, you are doing a true 70mph.

If you put on a 275/30/19 then you'd be doing a true 68.6mph when your speedo said 70mph.

If you put on a 275/35/19 then you'd be doing a true 71.5mph when your speedo said 70mph.

Neither is a significant enough change to be a concern, and your speedo will be over-reading slightly today (an indicated 70mph is probably a true 67mph or thereabouts)  - so fitting a 275/35/19 probably just brings your true speed closer to the indicated speed. Easy to check with phone/satnav GPS speed readout.

If you replaced your oem wheels with the larger diameter S wheels instead, then the oem 275/30/20 fitted to them is 1.8% larger diameter than your current rear wheel. Which is another reason for my answer above.

Note: there are other factors to consider of course when changing tyre sizes. A slightly wider rear will slightly alter the handling balance that Lotus intended. And the rolling radius of the wheel obviously affects your overall gearing, so a 2% larger rolling radius has the effects mentioned above due to the fact it is increasing your overall gearing marginally. Hence acceleration will be around 2% reduced from where it is today. You wont notice that (you'd see the same kind of change going from a fully worn tyre to a brand new one) but i mention it for completeness. You might also consider mentioning any change to your insurance co. (Not cos it is going to have a negative effect, but cos it is in their interest to avoid paying out any more than theh have to if you ever have an accident, and you dont want that to be a cause of any discussion).

Edited by mik
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I like the short answer lol 

but I bow down to your thorough explanation so I will go with the 275/35/19 in PS4s would I have to go for same in the front but obviously in 18”s?  

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On 14/06/2019 at 13:00, G. Bell said:

I don't like the slightly stretched look of the stock sized tyre on the rear rim was thinking about going for 275/35R19 rear tyres instead. Given that 275/30R19 is an tyre size option it seems like it shouldn't be out of the question but does anyone have experience of doing this, if so any comments?

Stretched look? so why not 285/30?

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4 hours ago, DarrylV8 said:

Stretched look? so why not 285/30?

For me unless I see them in the flesh I find it hard to visualise but I am also concerned wider you go does the car go further away from the handling spec it was originally designed around ?

but I could be wrong ?

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Fair question, but there seems to be slightly less availability in 285/30/19. I can find Mich Supersports for example, but no PS4 or PS4S?

CDM - if changing all 4 you might want to consider a 235/40 on the front too in pace of the 225? (Cars running the larger wheels have 235 fronts and 275 rears. 400s have 235 fronts, 285 rears.

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6 hours ago, DarrylV8 said:

Stretched look? so why not 285/30?

275/35 is the widest of the two ETRTO 'ideal' options for 9.5" rims, 285/35 is an ETRTO recommended spec but is a little ballooned on the rim. Normally I wouldn't worry but the ballooning and the fact you have an extra 10mm of sidewall will both tend to make the rear of the car wander a lot more. I experienced this with going from 225/35R18 to 275R35/18 on my Z4 on 9" rims. It gave the feeling of the car wanting to wag it's tail (as @JayEmmwill attest to) making you feel you're near the limit of grip but you start to push harder it settles down. Not a problem in a car that's a baby GT wanting to munch miles on fast open B-Roads & A-roads, on the Evora I think it's going to spoil the feel and confidence in the car.

@mikI'd be worried about ballooning the front tyres and increasing the front tyre wall height. This will tend to dampen your turn in a little, as you reduce the sidewall height ballooning a little bit is okay as you're mostly end up with about the same amount of lateral deflection at turn in. For instance going from 225/40 -> 245/35 on a 8" rim actually increased the sharpness of the turn in (and exposed even more deficiencies in the Z4's chassis)

Edited by G. Bell
response to mik's post

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