17inch wheels vs 18inch wheels

[BLOWN_VXSS]

Hey guys

What is the height difference between 17 inch wheels and 18 inch wheels, just curious as to how this would effect the ride height?

For example I have the standard vx ss wheels and tyres (17x45x235). If I was looking at some 18 inch rims 18x40x235 (I persume this is the standard size) how much higher would the car sit????

Is there an easy way to calculate this - my guess is below but there's probably another factor I haven't considered....

17inches = 431mm + 45mm(tyre profile) = 476mm

where as

18inches = 457mm + 40mm(tyre profile) = 497mm

Therefore the increase in height would be 476 minus 497 which equals 21mm??? Does this seem about right?

Alternatively if someone can measure their 18inch wheel from bottom of tyre (ground) to the hub and let me know....

Cheers

[DaveHAT]

Hey guys

What is the height difference between 17 inch wheels and 18 inch wheels, just curious as to how this would effect the ride height?

For example I have the standard vx ss wheels and tyres (17x45x235). If I was looking at some 18 inch rims 18x40x235 (I persume this is the standard size) how much higher would the car sit????

Is there an easy way to calculate this - my guess is below but there's probably another factor I haven't considered....

17inches = 431mm + 45mm(tyre profile) = 476mm

where as

18inches = 457mm + 40mm(tyre profile) = 497mm

Therefore the increase in height would be 476 minus 497 which equals 21mm??? Does this seem about right?

Alternatively if someone can measure their 18inch wheel from bottom of tyre (ground) to the hub and let me know....

Cheers

Try this: http://www.1010tires.com/TireSizeCalculator.asp?action=submit

May help.

Cheers.

[BLOWN_VXSS]

Thanks TigerSS, according to this the difference (overall diameter) is 2.04mm which is going to make stuff all difference to a cars ride height.

Thought it may have had more effect than that.

[pah]

Hi Monaro 57,

I don't think there's as much difference in ride height as people might think. It's my unnderstanding that larger rims are compensated for by shorter tyre side walls. If this is correct, when you stand a 17" tyre & wheel up against an 18" tyre and wheel, they'd stand as tall as each other (same diameter circles). Larger rims help handling because the associated short tyre wall removes some of the "suspension" provided by the tyre. This of course increases turn in response etc but comes at the loss of ride comfort.

Having said that, even different brands of tyre will give differing numbers of revolutions per kilometre. Don't cop cars need to have their radar calibrated to the car every so often? I'd imagine after fitting new tyres. If they want their radar to be spot on (and I don't know how spot on it needs to be) they might need to have their radar calibrated as the tyres wear down a bit if worn tyres reduce in diameter enough to affect radar accuracy.

I doubt that there's too much difference between 17" & 18" tyre costs these days. One of the risks with 19" rims and maybe even 18" and 17" rims is that the low profile tyres have very little cusioning effect when bumps are hit. This means that banged up rims are much more common these days. Some people run their tyres up towards 40 psi to protect their rims. this probably costs them a bit of tyre life.



PAH

[DaveHAT]

Thanks TigerSS, according to this the difference (overall diameter) is 2.04mm which is going to make stuff all difference to a cars ride height.

Thought it may have had more effect than that.

No worries, hardly worth worrying about.
During a tyres cycle life, they wear down by more than that amount & no one worries.

[BLOWN_VXSS]

I'm trying to look at ways that I can increase ride height by another 10mm or so as it's sitting quite low with the 17's and king super low springs. Don't wanna attract the wrong attention if you know what I mean, and at the same time couldn't stand it being the standard height again. Another possibility I just thought of is maybe I could get a couple of mm's out of raising the exhaust, that is if it can go any higher....

The joys of having a lowered car, but I guess this is the trade off.

[BLOWN_VXSS]

.... or maybe I could get some airbags.

[bobg]

Hey guys

What is the height difference between 17 inch wheels and 18 inch wheels, just curious as to how this would effect the ride height?

For example I have the standard vx ss wheels and tyres (17x45x235). If I was looking at some 18 inch rims 18x40x235 (I persume this is the standard size) how much higher would the car sit????

Is there an easy way to calculate this - my guess is below but there's probably another factor I haven't considered....

17inches = 431mm + 45mm(tyre profile) = 476mm

where as

18inches = 457mm + 40mm(tyre profile) = 497mm

Therefore the increase in height would be 476 minus 497 which equals 21mm??? Does this seem about right?

Alternatively if someone can measure their 18inch wheel from bottom of tyre (ground) to the hub and let me know....

Cheers
The error in your calculations is that you have used the tyre profile ratio as a direct measurement in millimetres.

The second figure in the tyre size 17x45x235 [i.e. the 45% profile ratio] is a proportion in percentage of the tyre cross-section width - not a direct measurement. 45% of 235mm is 105.3mm. Therefore the tyre itself adds 105.3mm between the rim and the ground.

With the same tyre section width [i.e. 235 mm] on 18" rims [i.e. 18x40x235] the tyre would add 94mm [i.e 40% of 235 mm] between the rim and the ground [a reduction of 11.3mm from the 17x45x235 tyres] but the rim would add 12.7mm [half the difference between 17" and 18" which is 25.4mm divided by 2] so the net difference is a raising of the car by 1.4mm.

Regards

Bob G

[chook]

As BobG said it's about 1mm, so basically no difference at all

[BLOWN_VXSS]

Thanks BobG, I had a feeling I went wrong somewhere with the profile size.
Can you go to a bigger profile tyre, say 18x45x235. Not sure if this size would be legal though?
Am I right in saying this could raise the car by aound 13mm in over a 17x45x235. (Hoping i got the figures right here)

[MR.HRT]

Thanks BobG, I had a feeling I went wrong somewhere with the profile size.
Can you go to a bigger profile tyre, say 18x45x235. Not sure if this size would be legal though?
Am I right in saying this could raise the car by aound 13mm in over a 17x45x235. (Hoping i got the figures right here)

Not sure if it would be legal but it would put your speedo out.;)

[VU_SS_UTE]

I'm trying to look at ways that I can increase ride height by another 10mm or so as it's sitting quite low with the 17's and king super low springs. Don't wanna attract the wrong attention if you know what I mean, and at the same time couldn't stand it being the standard height again. Another possibility I just thought of is maybe I could get a couple of mm's out of raising the exhaust, that is if it can go any higher....

The joys of having a lowered car, but I guess this is the trade off.

Get some 19s on it with 35s, that will lift it up a bit.

[555]

Hey guys

What is the height difference between 17 inch wheels and 18 inch wheels

1 inch............... :thumbsup:

[Vulture]

I think what we are talking about here is overall diameter. I'm not sure on your state but in QLD we are not allowed to increase the OD by more than 15mm of the largest factory combo. The Yokohama website has measurements for their tyres. Down the bottom of the page. eg the OD of 235/40/18 tyres is 643mm. This is why a lot of 20 inch combos are illegal. Be careful as some tyre shops are happy to sell illegal combinations.

LINK (http://www.yokohama.com.au/ourtyres/tyre.aspx?tyreid=58)

[VU_SS_UTE]

1 inch............... :thumbsup:

HAHAHA i was thinking about that one, I knew someone would say it