Lowering + Bigger Wheels vs Speed bumps

[Swinginking 3]

Hi Guys,

Would like a little advice on this, 

 

Currently sat on 17inch standard wheels with huge enough wheel gaps to fit my head in. 

So I am wondering If I stepped them up to 18inch wheels and then lowered the car a tad bit (or vise versa preferably) would this reduce the wheel gap without actually reducing the car height so I wont be terrified of speed bumps? or am I thinking this wrong, and the 18 inch wheels (alone) wouldn't increase car height but would reduce wheel gap? 

[Deacon 1357]

1 hour ago, Swinginking said:

Hi Guys,

Would like a little advice on this, 

 

Currently sat on 17inch standard wheels with huge enough wheel gaps to fit my head in. 

So I am wondering If I stepped them up to 18inch wheels and then lowered the car a tad bit (or vise versa preferably) would this reduce the wheel gap without actually reducing the car height so I wont be terrified of speed bumps? or am I thinking this wrong, and the 18 inch wheels (alone) wouldn't increase car height but would reduce wheel gap? 

Changing the wheel size won't change the arch gap only changing the tyre size will do that and if you go too far off you will throw the speedo way off. 

So with an 18" wheels you'll have a lower profile tyre than you would with a 17"

To get rid of the gap you'll need to lower it really. 

[bassett 48]

I'm lowered 30mm on springs with 18s that acheive the same wheel size as 17s. Never scraped on a speed hump yet in South London although I don't use it for a daily commute but face many in the local area and it's fine with full width humps and the little ones

[Captain Duff 79]

I would start with what you want the car to do. The stock wheels are reasonably light for OEM (tad over 9kg a corner if memory serves), but you will get better handling if you can go lighter, 6-8kg a corner for example (so look out for the weight specified for the rims you are interested in, if they don't specify a weight it generally means that they are not light!).  Going lighter is harder and more expensive to do if you want to go to 18" rims than if you get 17".

As others has said, 18" will mean lower profile tyres. You may like the look of these, but bare in mind the state of your local roads and the less protection to your precious rims that a low profile tyre means.

But back to what you want the car to do. If you are looking for track then 18" rims and low profile tyres with some added width compared to OEM might suit. If you are not tracking but daily driving then  sticking to 17" but altering your suspension may be right for you. And then if you are looking for a tuning looks and stance approach then you will have different options still.

In terms of lowering I have recently dropped 20mm from stock on some KW v3 coilovers and that seems fine for clearance (I initially - and by mistake - went down 40mm and that was not good at all!). A drop of 15-20mm is fine and also means that you have less to worry about in relation to alignment geometry, more than 20mm and that is more of an issue, although I would always recommend a specialist 4 wheel alignment following any suspension changes anyway (and at one of the specialist garages that are active on this forum, if you go to non-performance specialists they will just be using the OEM alignment calibration figures which would not be correct).

A cheap lower can be achieved by new springs on OEM suspension, but these may not improve handling (in fact they may do the opposite), which is why it may then be better to go for a quality compete coilover replacement, but of course then your budget stretches significantly, which brings things back to what you want the car to do afterwards