How Much Do Oversize 4x4 Tyres Affect Acceleration ?

[V8RX7]

I know it's never going to be a race car... but a previous owner fitted 305/70/16 tyres to my V8 F150

It seems a lot slower than my previous one albeit that had a slightly bigger engine but I suspect part of the reason is that despite the V8 - it hasn't got the torque to pull the increased gearing caused by the tyres.

I'm wondering if reducing them back to 275/70/16 will make much difference (approx 5% smaller) obviously they will also be a bit lighter too.

Standard size is only 235/70/16 but I'm unwilling to return to them.

Thanks

[Leptons]

That's some increase from standard. Lots I'd say!

[StuntmanMike]

That's a big difference, I wouldn't believe your speedo either.

[skyrover]

According to this site

http://www.kouki.co.uk/utilities/visual-tyre-size-...

Your speed will be 13.3% greater than indicated
When it reads 30mph you will actually be doing 34mph
At 60mph indicated you will be doing 68mph

Edited by skyrover on Thursday 6th March 10:40

[BritishRacinGrin]

I'm not so sure. 305/70 is 5.3% bigger in circumference than 275/70. It'll make a noticable difference but nothing miraculous.

ETA: the standard size though, well yeah that's quite a lot smaller then 305/70.

[Bill]

13% increase in circumference over standard plus 40% wider will have huge effect. I'd be tempted (unless you off road much) to go for 265/60 16 to maintain circumference but also because it's a standard LR size so they're probably cheaper.

[skyrover]

Bill said:

13% increase in circumference over standard plus 40% wider will have huge effect. I'd be tempted (unless you off road much) to go for 265/60 16 to maintain circumference but also because it's a standard LR size so they're probably cheaper.

Standard land rover size would be 235/85 16 or 265/75 16

[Bill]

[cough]Disco 2[/cough]

[skyrover]

That's not a land rover

[Bill]

I don't know what the current Defenders have as standard but the sizes you quote used to be the answer to the aftermarket "how big can I go without fouling" question.

[skyrover]

Bill said:

I don't know what the current Defenders have as standard but the sizes you quote used to be the answer to the aftermarket "how big can I go without fouling" question.

Current stock size for a defender is 235/85 16

largest you can fit without a lift is 285/75 16 or 255/85 16

[V8RX7]

Because this has had the factory option lift the standard tyres look a bit silly.

It's a toy but a toy that is going to tow occasionally

[andy-xr]

I once had a 2.0 8V Frontera on silly tyres, bought for over the winter to get me about. It was ridiculous looking but I bought it anyway.

Going over to my folks, Mansfield to Lancaster Xmas Day morning, couldnt get it past 70, 75 going downhill. I'm sure the tyres had quite a lot to do with it, car just didnt have the power to push it past that.

Ah, here it is

Edited by andy-xr on Thursday 6th March 11:34

[skyrover]

Here's an f-150 on 265/75 16 tyres... my current favourite size





diameter and drag will be a bit less than your current truck, without looking too weedy

[Bill]

skyrover said:

Current stock size for a defender is 235/85 16

largest you can fit without a lift is 285/75 16 or 255/85 16

Interesting. I wonder if I'm misremembering or something has changed (which seems unlikely tbh )

Sorry OP. Is there a factory tyre fitment that goes with the lift?