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Widths and offsets when fitting 18's to an S4 - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums #ForTheOwners Jump to content


Widths and offsets when fitting 18's to an S4


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Hi guys, I'm needing some technical advice regarding wheels and offsets for an S4.

My car came to me fitted with a set of Aussie made ROH wheels which I think are 9 inch fronts with a +22 offset and 11" rears with a +4 offset.

The 9" fronts have a 225/35-18 stretched onto them and the rears are a bit more sensible with a 285/30-18 fitted.

The car drives okay, but darts around a lot and doesn't point as well as I expected it too. My old Ferrari 308GT4 will drive rings around it, which it simply shouldn't do, especially given that the Lotus is 20 years younger.

I've been searching all over for information on the correct wheel and tire width / offset etc when updating the S4 to 18" wheels, but I can find some opinions but nothing technical and specific.

It looks like I will have to have a set of wheels made as I can't locate anything locally to fit it, and if I'm going to have to go to the trouble of having something made, then I really want to make sure that offsets and widths are perfectly correct for the car. 1994 Esprit S4.

I'd love a set of Oz Futuras but they are rare as hens teeth, so I'll have to make do with something easier, but I do want to get widths and offsets as close as possible.

 

Below picture with the ROH wheels.

 

IMG_2083.JPG

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It means the tolerance range is plus 12 minutes or minus 6 minutes on the negative camber setting of 42 minutes (i.e. the camber angle is acceptable if it's between  -30' to -48').

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G'day Ian. 
No, I 'm simply presuming that a 9" front with a 225/35 squeezed onto it leaving just a bare strap of rubber sidewall to the road just cant be right so I'm trying to track wheels and then do the alignment.

In your experience, are the geometry settings on an S4s and an S4 the same. Can you point me at the accurate front and rear settings for the car please?

This arvo I stuck another set of wheels on the car and just came back from a drive. Borrowed wheels from a Ferrari 360 modena.

Front 7.5 +31.5 offset with new Pirellis. Rears 10.5 +39 offset also with Pirelli tyres. The car was still twitchy. Lighter to steer to the right than the left. Didn't follow irregularities in the road as bad. But on two occasions, the rear stepped out slightly under throttle, maybe due to the narrower track.

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I always think it's best to start with the cheapest/easiest things first, so I'd be having a good look underneath at the suspension bushes, steering rack, track-rod ends, wheel bearing play, anti-roll bar bushes etc., all easy things which don't take a lot of time, and cost nothing. You may see something obvious. If not then the geo check is the next cheapest, and will confirm your driving experience.

Thing is, you've just changed the wheels,  and it's still not right, which may or may not be a pointer. By way of an example, when I bought my car, the LHS top wishbones had previously been fitted back to front, negating any castor, and the car pulled to the left as a result. There are any number of TLF members who will testify that the geo makes so much difference to an Esprit's handling.

The geometry settings are all in the Lotus Service notes,  I think under the suspension section. I don't know if they're identical to the S4s as I don't have them to hand right now, but perhaos someone else can confirm that?

Margate Exotics.

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And while we are on the subject. Are these cars really fussy about wheels / tyres / offset. Many cars don't seem to phased, yet others; particularly certain Toyota models; are incredibly fussy. get your offset or backspacing wrong by a few mm and the car handles like crap. How's the S4 with different wheels on it?

 

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Some further research indicates the following:

A bit difficult to understand, but apparently from the service notes.

Front:

Camber -0.7"; + 0.2 deg, -0.1"  (-0 deg 42'; +12', -6')  what the hell does that all mean? +12', -6'???
Castor +3.2"; +/- 0.2"  (+3 deg 12'; +/- 12') within 0.2 deg (12') side to side
Toe  1.0mm toe out overall +/- 0.5mm
Steering axis inclination 9.6" (9 deg 35') nominal

Rear:

Camber -0.9"; +/- 0.2" (-0 deg 54'; +/- 12')
Toe 1.5mm toe in each side +/- 0.5mm    0.2" toe in each side; +/- 0.07"

 

 

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X2 on the suggestion for having the alignment checked. :P

 

ian29gte had the most complete set of suggestions going forward.

 

Your alignment shop will know what the alignment specs mean. If they don't have the Lotus specs in their alignment machine show them your info from the post, above.

 

PS: What tire pressures are you running? THAT could make a huge difference. Perhaps someone else with 18s can make a suggestion...otherwise I'd play with a laser pyrometer, and adjust to get a uniform temp across the entire tread.

 

Those wheels LOOK pretty, BTW! B-)

Atwell Haines

'88 Esprit

Succasunna, NJ USA

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21 hours ago, uzz32soarer said:

Some further research indicates the following:

A bit difficult to understand, but apparently from the service notes.

Front:

Camber -0.7"; + 0.2 deg, -0.1"  (-0 deg 42'; +12', -6')  what the hell does that all mean? +12', -6'???
Castor +3.2"; +/- 0.2"  (+3 deg 12'; +/- 12') within 0.2 deg (12') side to side
Toe  1.0mm toe out overall +/- 0.5mm
Steering axis inclination 9.6" (9 deg 35') nominal

Rear:

Camber -0.9"; +/- 0.2" (-0 deg 54'; +/- 12')
Toe 1.5mm toe in each side +/- 0.5mm    0.2" toe in each side; +/- 0.07"

 

 

 

When I had my geometry checked, the garage used a Hunter Hawkeye alignment system which had the Esprit geometry settings already in the machine database.

Margate Exotics.

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On 10 August 2017 at 11:13, uzz32soarer said:

 what the hell does that all mean? +12', -6'???

It means the tolerance range is plus 12 minutes or minus 6 minutes on the negative camber setting of 42 minutes (i.e. the camber angle is acceptable if it's between  -30' to -48').

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