Tires for 18" wheel, ride comfort and the 3% rule

[ZCFUAE]

Hi,

First of all accept my excuses if I'm posting a duplicated question, but I read quite a bit the previous posts without finding the answer.

Just bought a V 1.6 mpi and I'm happy with it; yesterday drove at 150km/h (~90 miles) and it has a really nice grip, handling,...

But still not that comfortable for a city ride, guess it has to do too with the 215/40 18" tire(hankook ventus 2). Previous posts suggests that comfort can be improved by a tire with higher side wall. 225/40 is a safe bet. But I still would like to give a further step considering:

- the rule of thumb that says that tires should not exceed 3% of the original diameter;
- lighter tires and lower UTQG may be better (not sure, let's skip these variables);
- despite common impression that wider tires are more comfortable: I read a collumnist, citing a German study, saying that wider tires decrease comfort (cannot double check since I can't read German);
- My prime objective is to increase comfort (sidewall height) not braking, fuel economy, odometer,...

so, I came down to three alternatives:

a) 225/40 18" : safe choice;
b) 235/40 18" : change circunference by 2.5%, increase side wall by 8mm or 9% and width by 20mm or 9% too;
c) 215/45 18" : same width of the original, increase sidewall by 11mm or 12.5% and circunference by 3.4%;

I would like to go, eventually, with alternative "c" despite exceed the 3% rule of thumb and, after all, we are talking about of just a few more mm so I guess they will fit without eventual rubbing. Thus, my questions are: first, if someone has tried alternatives b & c; secondly, if a tire expert out there can drop a few lines to comment on the alternatives.

Thanks in advance and sorry for the long post,

P.S.: Some interesting sites below:
Ejelta.com: Tire Size Calculator: 215/40-18

215/40-R18 vs 215/45-R18 Tire Comparison - Tire Size Calculator

P.P.S: I'm not considering changing the wheel size to 17"

[x_Diesel_x]

I have not tried any of your options but seeing the marginal difference to be expected I don't believe you'll notice a considerable improvement of ride comfort.

Akin to airing down your tires a bit really. Although 225/40 will be a nice compromise as prices and selection for that size is better than the other options you are pondering.


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[Curmudgeon]

As I recall, the only forum members who have reported any improvement in ride comfort have done so with the softer sidewall Continental DWS 225/40/18 tires. From their descriptions, the improvements were modest, e.g. "...not a night-day difference", etc.

The Conti tires are also 1 pound lighter than the OEM Kumho rubber despite being slightly larger. Most Conti DWS buyers report slightly diminished handling/steering response (e.g. lesser 'crispness')...some complain, others accept as satisfactory. Besides the harshness of the OEM tires (no experience with Hankook), a major complaint I have with the Kumho 18" setup is the tramlining tendency requiring driver alertness at all time.

[gchin]

Consumer Reports says: All-season tires

They are a popular choice for many older vehicles and are for drivers who want year-round traction, long tread wear, and a comfortable ride. But they typically lack the precise handling and grip of performance tires.


Top Tire Ratings | Tire Buying Guide

[Velos510]

I was also thinking on doing the same thing, swapping out my Khumos for a more comfortable set of tires like the Falken Ziex or even the Continentals, the hankooks look pretty good too.

I'd also like to know if it would be a good idea or even worth it.

[Curmudgeon]

I was also thinking on doing the same thing, swapping out my Khumos for a more comfortable set of tires like the Falken Ziex or even the Continentals, the hankooks look pretty good too.

I'd also like to know if it would be a good idea or even worth it.

It only requires money to find out. Make the swap and then share the answer to your query with us.

Many of us would be most appreciative.

[ZCFUAE]

Thanks for the comments,

Today I used highly sophisticated tool/technique to measure the space available for a tire with a higher sidewall height, I used a ruler and a piece of cardboard... 8) (obviously I'm no expert);

In my V there are a 30mm space, but turning the steering wheels around it shrinks to 15-20mm because of the angles' change. So, I think, a 215/45 18" will fit without any rubbing because it increases sidewalls by ~ 11mm (and the circumference by 3.3% that's just a bit of a stretch of the 3% rule).

I'll use a bit more my tires, just new, than I'll proceed with this change.

Cheers,

[AdelaideSRT]

As long as you've taken in any difference in space caused by spring compression under load, and the potential flex in the sidewall when cornering, you should be ok - would hate to be there if you found out your 215/45 does scrub out in the middle of a nice hard cambered corner...

[MTD]

Plenty of people have slightly upsized their tires without any issues with fit. 215/40/18 or even a 225/40/18. They arent that much bigger.

Slightly wider and taller, they might soften the ride, but they might also be heavier and fuel economy and acceleration might suffer.

Also a touring or more comfort oriented tire wont handle as well as a performance oriented tire.

[tidybowl]

between lowering the car and putting wider wheels and 225/40/18 tires the car rides much better. not as much wiggle in the rear as before. its still there but not nearly as bad.

[cammyfive]

How about moving from the OEM 215/40/18 to a (Continental DWS) 225/45/18? So, if my understanding is correct, slightly wider and slightly taller for more comfort?

[jrhartman]

How about moving from the OEM 215/40/18 to a (Continental DWS) 225/45/18? So, if my understanding is correct, slightly wider and slightly taller for more comfort?

...and will help correct the incorrect speedo reading....


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[Curmudgeon]

...and will help correct the incorrect speedo reading...


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...and likely assist in diminishing the disconcerting tramlining of the OEM 18" Kumho tires.

[ZCFUAE]

225/45 18" will increase diameter by 4.8% (thus exceeding the 3% rule) and the sidewall height by 15mm, that is a very close call, on my rough calculations, for rubbing while cornering.

215/40-R18 vs 225/45-R18 Tire Comparison - Tire Size Calculator

I think 215/45 18" should fit without problem the tire fenders even while steering around.

regarding wider tires, not sure if they increase or decrease comfort (if that is the issue), since I read conflicting arguments.

Regards,

[jrhartman]

225/45 18" will increase diameter by 4.8% (thus exceeding the 3% rule)

Isn't the three % rule there because you don't want to throw your speedo off by a large amount? My speedo reads 74mph when I am really going 70mph. A 4.8% increase would bring the speedo much closer to being accurate.

^^^
All that being said, test fitting the tires to make sure there is no rubbing would be be key, also to make sure the car doesn't have a 4x4 look due the larger sidewall, but I think that would be unlikely as the stock tires look like rubber bands.



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[Curmudgeon]

As I recall, most V owners have rejected the 225/45/18 tires and opted for 225/40/18 tires with softer sidewalls. The 225/40 ratio tires present fewer issues, e.g. over-correcting the speedo, weight, width, etc. while offering a slightly higher (albeit slight) sidewall.

[cbrmale]

My Australian-spec turbo has Hankook Ventus Prime2 215/40 x 18 tyres and it has a nice, supple ride. And remember that Australian spec turbos have European springs (stiffer), and stiffer dampers than European-spec. And we have some pretty rough roads too! Compared to my previous car (Holden / Opel / Vauxhall Astra Sri - Golf GTI competitor) the Veloster has a luxurious ride! The Astra was a shocker and it rode so hard that sometimes it was hard to modulate my braking (my feet would get bounced against the brake pedal).

I think Americans overdo the soft and soggy ride scenario. If you want taught handling then you gotta put up with a choppy ride, especially at lower speeds. The American Veloster is softer than Europe which is softer than mine, and mine is quite fine.

If you want a rough ride than come pillion with me on my motorcycle. With super-low profile tyres and 80-odd mm of suspension travel, you will learn all about a rough ride! Until then stick with what you have because it's quite fine for a sports car, except you should fit stiffer springs and firmer dampers to extract better handling (closer to what we have stock).

[CRD]

Ive recently replaced my base OZ spec V wheels and tyres ( which came std with the Hankook ventus prime 2 ,215 40 18 tyres ). Ive purchased a set of VT wheels at the right price . I thought they would look pretty cool especially on the Blue V.I didnt want to split the original wheels and tyres in case i wanted to go back to the original look so i decided to purchase a set of tyres to suit . Because the car is used primarily for daily commute I too found the Hankooks pretty firm but still livable. I figured thats how the car was designed and had no problems accepting it that way.To my surprise though , after installing the Turbo wheels with new 215 40 18 tyres the ride immediately was smoother and noticably more comfortable ,it just seemed to take that edge off the harshness . There was no real noticable change in handling , keep in mind that I dont go driving the thing at 10 tenths every where. When i made the decision to replace the tyres it wasnt to change the dynamics of the car. The tyres I ended up using where Nankang 215 40 18 NS2. My decision to use these tyres was based on part cost and part having used them on a number of other daily drivers prevously with no issues.

So i guess to answer the original question. You can find a tyre that wont change the rolling diameter and get that extra bit of comfort you where chasing. You will probably need to talk to a few different tyre shops to find something that suits you.Hope this helps ..




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[Curmudgeon]

As I recall, most V owners have rejected the 225/45/18 tires and opted for 225/40/18 tires with softer sidewalls. The 225/40 ratio tires present fewer issues, e.g. over-correcting the speedo, weight, width, etc. while offering a slightly higher (albeit slight) sidewall.

For those considering swapping up to 225/45/18 tires, I recently parked the V with OEM Kumho 215/40/18 next to the spouse's Fusion Sport with OEM Goodyear RS-A 225/45/18 tires. With only a 0.6 inch higher sidewall, the 225/45/18 appeared to dwarf the Kumho tires. With just a non-tech/spec eyeball comparison to guide my judgement, I would be rather reluctant to install the 225/45/18 tires on the V.

Re: tire weights. I would also be cautious about swapping up to any tires with significantly increased weight per tire. With that in mind, I found it interesting that some 225/40/18 tires (e.g. Conti) are ~1 pound lighter than the OEM Kumho.

[cbrmale]

Kumho tyres are absolute rubbish where Hankook aren't bad. I had 225 / 45 x 17 (stock size) Continental Sports Contact 3 on the Astra and they had a soft tread compound so they wore fast and were prone to punctures. They were good though with fantastic dry weather grip, good wet weather grip and very low noise levels. To fit the 225s on the Astra, Opel changed the steering lock so they wouldn't rub on the inside.

Motor manufacturers specify different characteristics for OEM tyres, so this may be why the turbo tyres ride softer. The stock Sports Contact tyres on my Astra were reasonably durable but the replacements I bought wore very quickly. This is typical when comparing OEM with what's available retail.

I drive my car at the limit when I can, and a Veloster turbo gets a long way sideways without the esp (yet) kicking in. The Hankooks have decent grip and a nice feel on breakaway.