21 replies to this topic

[scoob101]

So I`m still trying to work out what wheels I actually want. I know I want 15" rims, and I know they must be lightweight, but I`m mystified by offset and width. 

 

I need my wheels to be nice and flush with the arch, so they look good. You can see the current ones look recessed by at least a couple of inches How to I determine the correct width and offset to get this right for a 91` Mk1 whilst retaining the handling characteristics??

 

[Rocky eunos]

You should check out Fitment Industries on YouTube, they have some videos explaining how to measure what offset you need for flush fitment e.t.c
Also on the website lots of pics of peoples cars with different wheels and they usually list the sizes/offset

[Bol]

I went through this a couple of years ago and came to the following conclusion for the right balance of weight/handling and appearance:

Standard wheels are generally 6j and ET45. I found that 7j and ET35ish pushed the wheels out far enough to look nice, provide extra grip but not mess up the subtlety of the handling.

Weight is the big issue. I’ve had general “aftermarket” wheels in this fitment which turned out to be surprisingly heavy (circa 16lbs, lots are heavier) and ruined the handling and ride. The standard mk2 5 spoke Enkeis are relatively light (13lbs) and very cheap. They’re ET40 though from memory and 6.5j so might need a small spacer to get the look you’re after.

I eventually settled on OZ Superleggeras (older version of Ultraleggeras) which are ET37, 7j and 10.8lbs. These were the sweet spot for me for a pseudo stock look. I was lucky to find them cheap in need of refurbishment, but Ultraleggeras seem to be cheaper now.

[Rocky eunos]

I have also gone with 7inch wide rims at et35, and handling is much improved with a light rim.

Got some Japan Racing JR5s that weigh 5.1kgs, and the difference it made to the handling compared to heavier rims was astonishing.

[Low Ender]

15x7" et35 here too, Enkei RPF1s which weigh in at 9.8 lb/4.5kg

[scoob101]

15x7" et35 here too, Enkei RPF1s which weigh in at 9.8 lb/4.5kg

 

These? They look jolly nice... (below are 8" wide tho)

 

[MR Wallace]

In 15" the RPF1 have a concave face below 8" wide, which doesn't look quite as good. The 8" are ET28 though which won't fit without rubbing on the arches (but a gentle roll will fix that). Awesome wheels in any size though.

[Low Ender]

Here's the 15x7 et35

 

 

[MR Wallace]

Yeah still look good Especially on such a clean car.

[Low Ender]

If I had been buying new, I would probably have gone for et41. My previous wheels were also RPF1s, 14x7 et 28, and the current closer to oem et35 offset has improved the steering and handling noticeably. I probably prefer the looks of the flat spoked 14s and wider 15s, but I didn't get them for looks. Second hand RPF1s are a sound investment - I had the 14s for 4 years and sold them for what I paid for them, which bought me the 15s. 

[Quinvy]

The only thing that annoys me about these wheels is that they don't supply centre caps for them.

[Zed.]

The only thing that annoys me about these wheels is that they don't supply centre caps for them.

its the cost for me  

Rich.

[scoob101]

If I had been buying new, I would probably have gone for et41. My previous wheels were also RPF1s, 14x7 et 28, and the current closer to oem et35 offset has improved the steering and handling noticeably. I probably prefer the looks of the flat spoked 14s and wider 15s, but I didn't get them for looks. Second hand RPF1s are a sound investment - I had the 14s for 4 years and sold them for what I paid for them, which bought me the 15s. 

 

Why the ET41 preference? Because they would fit more flush?

[MR Wallace]

 

If I had been buying new, I would probably have gone for et41. My previous wheels were also RPF1s, 14x7 et 28, and the current closer to oem et35 offset has improved the steering and handling noticeably. I probably prefer the looks of the flat spoked 14s and wider 15s, but I didn't get them for looks. Second hand RPF1s are a sound investment - I had the 14s for 4 years and sold them for what I paid for them, which bought me the 15s. 

 

Why the ET41 preference? Because they would fit more flush?

 

 

 

ET41 would be less flush than ET35. I'm confused by that being the preference too!

 

@Lowender, do you not think the improved handling is more down to the tyres and having a lower profile now? Up to a limit the lower offset and hence wider track width should be better for handling I would've though.

[Low Ender]

@Lowender, do you not think the improved handling is more down to the tyres and having a lower profile now? Up to a limit the lower offset and hence wider track width should be better for handling I would've though.

 

 

Partly due to lower profile yes, but the steering feel is better and doesn't weight up so much (I have a depowered rack) and the car turns in sharper. The car is designed to have et42 offset, the steering geometry (scrub radius, Ackerman angle etc) is set around this figure. Whatever, it's an improvement to the way the car drives.                           

[Zed.]

 The car is designed to have et42 offset, the steering geometry (scrub radius, Ackerman angle etc) is set around this figure. Whatever, it's an improvement to the way the car drives.

^^ this.

something nobody seems to consider, especially scrub radius  

easy to feel more grip but sometimes narrower tyres & track width can be faster - not forgetting the friction from wider tyres against tarmac or wind resistance.

wider wheels = more meccanical advantage so more extreme cases can pull the steering around  

Rich.

[Bol]

And you can really feel it. Particularly when you add in the unsprung weight of big heavy wheels.

[MR Wallace]

 

@Lowender, do you not think the improved handling is more down to the tyres and having a lower profile now? Up to a limit the lower offset and hence wider track width should be better for handling I would've though.

 

 

Partly due to lower profile yes, but the steering feel is better and doesn't weight up so much (I have a depowered rack) and the car turns in sharper. The car is designed to have et42 offset, the steering geometry (scrub radius, Ackerman angle etc) is set around this figure. Whatever, it's an improvement to the way the car drives.                           

 

 

That's interesting and yes I'm one of those that totally ignores/doesn't think about scrub radius or ackerman angle. In my simple eyes wider is better!

 

My road wheels are a much higher offset (not exactly sure what tbh) and the steering is much lighter than my track wheels but the car does feel more planted with the lower offset wheels, the tyres are too different to compare properly though.

 

It would be interesting to take a high offset wheel and incrementally add spacers to see what is "ideal" - but that may differ depending on use too.  

[noobie]

 

@Lowender, do you not think the improved handling is more down to the tyres and having a lower profile now? Up to a limit the lower offset and hence wider track width should be better for handling I would've though.

 

 

The car is designed to have et42 offset, the steering geometry (scrub radius, Ackerman angle etc) is set around this figure.

 

 

Have to be carefull there. The MX5 is designed around a nearly zero scrub setup not around et42 offset. An increase in wheel diameter or width will change scrub radius (and leave Ackermann unaffected)

Having said that, ET42 is in the right ballpark for a 15x7 with 195s. You'd probably find that increasing tire diameter with a 205 will be a move in the right direction with your ET35 wheels.

[Low Ender]

 You'd probably find that increasing tire diameter with a 205 will be a move in the right direction with your ET35 wheels.

 

Thanks for the insight. In what way would a 205 be better than 195 with et35 wheels?