Why does the FL have different wheel diameters?

Superluminal · February 13, 2017, 10:59

I was pondering this after reading about a few owners who have swapped to equal sized aftermarket rims. Just for interest really, as I have not owned a car with different diameter wheels before. Surely Toyota could have adjusted overall rolling diameter can be adjusted via tyre profile? I understand the benefit of additional width at the back, but what is the benefit of having a larger diameter rim (and/or larger overall rolling diameter)? Is it just aesthetic, and is it normal for mid-engined cars? What are the downsides of equal sized aftermarket rims? Does anyone have any ideas?

jonty · February 13, 2017, 13:50

It's aesthetic, makes the car look a bit more raked forward, nothing more than that!

insx · February 13, 2017, 14:15

I seem to recall that when I asked this, the answer was more grip/less oversteer.

Bernie · February 13, 2017, 14:20

Toyota considered the change an improvement to handling

m http://media.toyota.co.uk/2002/10/news-in-brief-2/ m

JoeCool · February 13, 2017, 16:09

Colin Chapman is on the record as saying you can't make a car handle 'properly' with the same diameter front and rear wheels.

It's a big factor in a cars geometry, so it will have a handling impact.

Carolyn · February 13, 2017, 17:09

The 16" wheels are also a little wider. All adding up to a slightly larger footprint at the rear. Interestingly, Dan at Rutland MR2 tells me the racers prefer 15s all round.

I changed my 15" rears for 16" and found the biggest improvement was straight line stability.

Of course a bit twitchy on the straights is no big deal on the track.

Superluminal · February 13, 2017, 17:34

Thanks, guessed it was mainly for looks. Maybe to counteract the huge wheel arch gaps!

lamcote · February 13, 2017, 21:15

Toyota clearly felt they wanted to put wider tyres on the rear with the facelift model. Two parameters that have a particular impact on the ride, handling, traction, gearing are tyre diameter and the volume of air in the tyre. For a 215 tyre, using 45 section on a 16 rim is the closest you can get to matching both the diameter and volume of a 205/50 15 tyre from the pfl. This would minimise the need for retuning the suspension by Toyota and therefore minimise the cost.

Superluminal · February 14, 2017, 07:58

Quote from: "lamcote"Toyota clearly felt they wanted to put wider tyres on the rear with the facelift model. Two parameters that have a particular impact on the ride, handling, traction, gearing are tyre diameter and the volume of air in the tyre. For a 215 tyre, using 45 section on a 16 rim is the closest you can get to matching both the diameter and volume of a 205/50 15 tyre from the pfl. This would minimise the need for retuning the suspension by Toyota and therefore minimise the cost.

That is very logical and makes complete sense so it will probably be the answer I give to anyone that asks me. Thanks!

jonbill · February 14, 2017, 17:53

I read an interesting site a while back, about diameter and widths against footprint.
Surprisingly, footprint is more or less exclusively a function ot vehicle weight. Given 255/50/18 and 165/50/14 tyres on the same car with similar inflation, contact patch size is the same.

JoeCool · February 14, 2017, 20:40

Yeah, I learnt this 4x4ing in Australia. I Did a few courses. When you think about it, it's the pressure in the tires that dictates the contact patch. The air is supporting the car. The tire just bends to the point where the air can do it's job.

We'd run as low as 8psi on the beach, and that was fine. Until you sank!

jonbill · February 15, 2017, 08:54

Quote from: "JoeCool"Yeah, I learnt this 4x4ing in Australia. I Did a few courses. When you think about it, it's the pressure in the tires that dictates the contact patch. The air is supporting the car. The tire just bends to the point where the air can do it's job.

We'd run as low as 8psi on the beach, and that was fine. Until you sank!

Thats a great way of thinking about it!