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View Full Version : Tyre size 20" rims



Steven
24-10-2005, 10:37 PM
just been down to local mag dealer talking to him about putting 20" deep dish mags on, although they currently have R20 225 35 tyres on them and this is over what the legnum should have as it should be R20 225 30.. he reckons it will only affect speedometer reading... be any probs wid AYC and the like? or i could just swap the tyre for a ****tier 30.. not tht its something i want to do as for what i might be getting is a hella cheap package :leer:

KiwiTT
24-10-2005, 10:56 PM
20" :o That will look good.

However, You will certainly effect its ride and possibly the finer points of handling in the corners.

I read somewhere, where the M3 with 17" out-handled a 18" version.

However, if you are only after the looks and you keep the diameter as close to stock (+/- 1-2%) you should be OK. But do put the 30 profile on. Do a serach for tyre size calculator just to confirm.

SGHOM
24-10-2005, 11:04 PM
ever thought about 22's, & a tin of black paint ?? :rolleyes4 /Devil5 :curtain:

Quail
24-10-2005, 11:55 PM
Dont do it! Your handling and acceleration will go down the drain!

Kieran
24-10-2005, 11:55 PM
Mmmm..... I think Kiwi's got a good point - there will be so little 'give' in the tyres that you could upset the handling. Stiffness is nothing without the right amount of compliance (oo-er). I think 20s will make the car feel skittish and on rough tarmac, I can imagine that it will tramline everywhere - and the AYC/TC might pick up on this and have a fit trying to control it all.

Kenneth
25-10-2005, 12:58 AM
The reason behind the handling issues are due mainly to weight. the tyre profile affects safety (load index has a relationship with profile) and comfort but should not adversly affect the handling on their own.

The weight of 20" rims is likely to be significant unless they are some ultra ninja wheels that cost an arm and a leg.

There are a few ways that weight affects the handling... here are the ones I can think of off the top of my head.

1) rotational momentum- your brakes have to apply extra braking torque to the disk to slow down the extra mass. This will result in more stress on your brake components.

2) Suspension - Your suspension has to move the wheel fast enough to keep the tyre on the road (at least it will try to). The heavier the wheel the more work the suspension needs to do. Try moving an object quickly then seeing how quick you can reverse its direction. now try it with a heavier weight. thats what your suspension does.

3) Turning - Your wheels work like gyros. The heart of a gyro is a spinning disk. the inerta of the disk keeps it facing the same direction even though you move the outside bits.
So, the more weight in your wheels, the less they want to turn. you will have to overcome this force to turn the wheel.

mpau009
25-10-2005, 01:54 AM
he reckons it will only affect speedometer reading... be any probs wid AYC and the like? or i could just swap the tyre for a ****tier 30..

My understanding was that if your rolling diameter is increased by more than 5% you have to get a Lov Volume Vehicle cert (under $300), because they want to see that you can still turn, and stop, and general safety stuff. You could probably get away with it, but the wof people might notice?

What sort of price deal are you getting? any chance of setting up a club discount type of thing.... /yes could definately use some new mags

i3ooyah
25-10-2005, 11:33 PM
Mmmm..... I think Kiwi's got a good point - there will be so little 'give' in the tyres that you could upset the handling. Stiffness is nothing without the right amount of compliance (oo-er). I think 20s will make the car feel skittish and on rough tarmac, I can imagine that it will tramline everywhere - and the AYC/TC might pick up on this and have a fit trying to control it all.

the thing is if you get 20's its purely for looks and nothing else so all that stuff wont matter about handling, etc as stefan prolly doesnt care and just wants to appear popular to the opposite sex with his big feet

Steven
25-10-2005, 11:35 PM
not sure about club discounts as this pretty much a one off deal, $3000 with tyres for 20" deep dish he said the package was worth $6000, but after what Kenneth said im not too sure about it anymore.. it would look good but im not sure if im keen to make it a sluggish beast

Steven
25-10-2005, 11:38 PM
the thing is if you get 20's its purely for looks and nothing else so all that stuff wont matter about handling, etc as stefan prolly doesnt care and just wants to appear popular to the opposite sex with his big feet

:smug: so the truths out :embarasse

Kenneth
25-10-2005, 11:45 PM
not sure about club discounts as this pretty much a one off deal, $3000 with tyres for 20" deep dish he said the package was worth $6000, but after what Kenneth said im not too sure about it anymore.. it would look good but im not sure if im keen to make it a sluggish beast

Depends on what you want to do with your car :)

If you enjoy it for performance then you deffinatly want to consider the handling effects. If you just like to be able to squirt down the motorway and drag off other cars then its not such an issue.

Find out what they weigh before making your decision also. If they are light weight racing rims or some such then it might be well worth it.

Big 20" bling bling chromies are probably going to weigh a fair bit though.


hehe, other thing is that if they REALLY ARE worth $6000, then maybe you can on-sell them for a bit of a profit ;)

Kenneth
26-10-2005, 02:21 AM
Oh yeah...

4) changing the un-sprung weight (wheels etc) can apparently affects gas milage quite significantly.

Personally I am not really that into squeezing every last drop of fuel efficiency out of my motor, but if you are then dont put heavier wheels on.


When I get around to putting new wheels on, my intention is to go with 17s and add extra width for cornering. Only reason I would consider 18 is if I was planning on some huge brakes.