Register Login
The UK's No.1 Chrysler Owners Forum
Reply
 
Thread Tools
Old 23-09-2017   #1
Join Date: Dec 2015
Posts: 167
Thanks: 9
Trader Rating: 0
United Kingdom 
Higher profile on 18" wheel ?

When researching my new 500x purchase, I remember reading that the 18" low profile tyres were a bit too firm in terms of ride, compared to the higher profile of the 17"

But, the model I wanted only came with 18" wheels.

So, have any of you tried gaining a little extra comfort by going up from 45 profile to say 50 or 55 ?
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

theshootist is offline Reply With Quote Quote 
Old 23-09-2017   #2
Join Date: Jan 2006
Location: Warwickshire
Posts: 613
Thanks: 13
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

This all depends on what you are used to. We have a Cross Plus with the 18" wheels on.
Yes the ride is firm but I don't feel it's much more so than on our old Sedici was. I specifically wanted the spec for the 18" wheels as I think they look the part but depends what you want to use the car for. As a 4x2 its not really an off-roader per-se but the ride does allow decent handling considering its height so the stiffness probably caters for that. I really don't think you would notice a difference in ride comfort on a car like the 500X with its performance on a marginally bigger profile tyre. IMO the seats make up for any discomfort in ride quality - they really are excellent.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides


Last edited by Nello; 23-09-2017 at 17:38.
Nello is offline Reply With Quote Quote 
Old 23-09-2017   #3
Join Date: Jan 2011
Posts: 185
Thanks: 13
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

Quote Originally Posted by theshootist View Post
When researching my new 500x purchase, I remember reading that the 18" low profile tyres were a bit too firm in terms of ride, compared to the higher profile of the 17"

But, the model I wanted only came with 18" wheels.

So, have any of you tried gaining a little extra comfort by going up from 45 profile to say 50 or 55 ?
I tried 2 versions on 18" wheels last October, the 2.0 and the 1.4, both I felt were unacceptable in terms of ride comfort to the extent I wouldn't have bought one. I did ask Fiat a few times at the time if it was possible to buy a cross plus and change the wheels to 17 inchers but the replies coming back were inconclusive.

That left me with the only option of walking away from the 500x or upspeccing a cross, to almost cross plus spec.

I found one last month, not exact cross plus spec but goodies on it to about equivalent value. Dynamic safety pack, comfort pack, and spare wheel.

I think the extra 20% wall depth on the cross by dropping down to 17 inch make all the difference, I like it firm, expect it to be but not 18 inch firm.

As for thinking its as easy matter as just buying higher profile tyres for 18 inchers it isn't. Doing so would make the rolling circumference larger, meaning your speedo and mileometer would be inaccurate, and thats just the start, there's a whole load of other potential issues too.
Likes NitramA liked this post
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

cowabunga is offline Reply With Quote Quote 
Old 23-09-2017   #4
Join Date: Dec 2015
Posts: 128
Thanks: 6
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

I'd be really interested to hear if anyone has tried a different profile tyre on 18 inch wheels.
To say the ride is firm is a bit of an understatement.
My old Audi S Line was a limo is comparison.
Wish I'd gone for the 17 inch wheels but I wanted the Xenon headlights.

So, if I were to fit smaller wheels how would you re-calibrate the speedo?
It must be possible.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

NitramA is offline Reply With Quote Quote 
Old 23-09-2017   #5
Ohhh my, yes.
 
Garree001's Avatar
Join Date: Jun 2009
Posts: 1,263
Thanks: 34
Trader Rating: 0
Garree001 has donated!
United Kingdom 
Re: Higher profile on 18" wheel ?

I find the ride more than acceptable in my Lounge. Less crashy than my old Corsa. A little more unsettled than the Fiesta of doom but still fine.

Higher profile tyres will affect the speedo reading. As you're at the biggest sized wheel for a 500x, it's no longer possible to adjust rim and tyre size to give accurate readings. Your only real option is to get smaller wheels and bigger profile tyres to make the overall wheel height the same.

Some cars allow limited adjustment to the speedo but I am unsure whether the 500x does.
__________________
Quote Originally Posted by karbineftw View Post
It sure looks like it's erect from my angle.
Quote Originally Posted by volxstu View Post
Hit somebody at 50.. they die. Hit somebody at 60.. they die quicker.
Signature by alexh365
Garree001 is offline Reply With Quote Quote 
Old 24-09-2017   #6
Join Date: Dec 2015
Posts: 167
Thanks: 9
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

I understand the need for a similar rolling circumference etc

I am guessing that whatever tyre that is on the 500x offered with 17" wheel is the same circumference - I cannot see FIAT going to the trouble of different gearing etc - easier to just make the rolling circumference the same, surely ?
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

theshootist is offline Reply With Quote Quote 
Old 24-09-2017   #7
Join Date: Dec 2006
Location: Southampton, Hampshire
Posts: 3,093
Thanks: 211
Trader Rating: 0
s130 has donated!
United Kingdom 
Re: Higher profile on 18" wheel ?

To add a little confusion here I'm wondering if the 500X (with SAT NAV) self calibrates.

To expand my 500X Cross Plus speedo exactly matches my Garmin SAT Nav. Now this, compared to older Fiat models which usually read 5% to 10% high, is rather unexpected.

I only found the speedo/sat nav correlation AFTER being caught by a mobile speed camera doing 79MPH on a dual carriage way. I also know I was knowingly driving at 80MPH (thinking the Fiat speedo was traditionally high).

This and other "not so sure" experiences lead me to thing that periodically the vehicles speedo self calibrates to a stable GPS (0.1MPH accurate) value.

Technically from a manufacturing point of view the vehicle is programmed with a default ABS wheel speed and tyre/rim size. Given an integrated SAT NAV then this default value could? be refined over a period of time. This would also allow the system to accommodate tyre wear (smaller rolling distance & increased speed).

Why is this relevant to fitting a different profile tyre on a rim? Well *IF* there is a system wide correlation then changing a tyres profile *may* self correct and adapt values to the new situation.

Also the 500X has TPMS. This is a passive system as there are NO pressure sensors in each wheel. Instead the ABS system monitors wheel rotation (in a straight line determined by steering angle) and can detect an underinflated tyre. So yes there is tight integration regarding wheel size, speed, pressure, etc.

When my tyres hit the minimum tread I'll try to remember to do a 3 way test.

Speedo at 60mph on motorway, Sat Nav speed and to cross check a stop watched timed 1.6km motorway marker timed period.

Without access to detailed manufacturer information, much of which is never disclosed to dealer level master technician level, we will be guessing, and as I have done, trying to understand actually what really happens, etc.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

s130 is offline Reply With Quote Quote 
Old 25-09-2017   #8
Join Date: Mar 2011
Location: Berkshire, UK
Posts: 896
Thanks: 55
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

There is a calculator and further information on changing tyre and wheel sizes here:
http://www.etyres.co.uk/how-to-change-your-tyre-size/
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

TrevC is offline Reply With Quote Quote 
Old 25-09-2017   #9
Join Date: May 2010
Location: Yorkshire
Posts: 184
Thanks: 9
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

Quote Originally Posted by s130 View Post
To add a little confusion here I'm wondering if the 500X (with SAT NAV) self calibrates.

To expand my 500X Cross Plus speedo exactly matches my Garmin SAT Nav. Now this, compared to older Fiat models which usually read 5% to 10% high, is rather unexpected.

I only found the speedo/sat nav correlation AFTER being caught by a mobile speed camera doing 79MPH on a dual carriage way. I also know I was knowingly driving at 80MPH (thinking the Fiat speedo was traditionally high).

This and other "not so sure" experiences lead me to thing that periodically the vehicles speedo self calibrates to a stable GPS (0.1MPH accurate) value.

Technically from a manufacturing point of view the vehicle is programmed with a default ABS wheel speed and tyre/rim size. Given an integrated SAT NAV then this default value could? be refined over a period of time. This would also allow the system to accommodate tyre wear (smaller rolling distance & increased speed).

Why is this relevant to fitting a different profile tyre on a rim? Well *IF* there is a system wide correlation then changing a tyres profile *may* self correct and adapt values to the new situation.

Also the 500X has TPMS. This is a passive system as there are NO pressure sensors in each wheel. Instead the ABS system monitors wheel rotation (in a straight line determined by steering angle) and can detect an underinflated tyre. So yes there is tight integration regarding wheel size, speed, pressure, etc.

When my tyres hit the minimum tread I'll try to remember to do a 3 way test.

Speedo at 60mph on motorway, Sat Nav speed and to cross check a stop watched timed 1.6km motorway marker timed period.

Without access to detailed manufacturer information, much of which is never disclosed to dealer level master technician level, we will be guessing, and as I have done, trying to understand actually what really happens, etc.
In short, no it doesn't.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

robotdancer is offline Reply With Quote Quote 
Old 25-09-2017   #10
Join Date: Dec 2006
Location: Southampton, Hampshire
Posts: 3,093
Thanks: 211
Trader Rating: 0
s130 has donated!
United Kingdom 
Re: Higher profile on 18" wheel ?

Quote Originally Posted by robotdancer View Post
In short, no it doesn't.
What is the long answer?

Even when the vehicles sat nav is truned off it is actually running in the background, hence all the people complaining about the car alert tones for speed cameras.

Also the vehicles SAT NAV speed EXACTLY matches the speedometer.

To much of a coincidence? Well for me anyway.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

s130 is offline Reply With Quote Quote 
Old 25-09-2017   #11
Join Date: May 2010
Location: Yorkshire
Posts: 184
Thanks: 9
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

You might well just happen to have a very accurate speedo. But the nav isn't linked to the car in that manner. If you think about it, the nav head units are from third party suppliers and run differing software (see all the various threads about updating the Tom Tom and 6.5" mapping etc.) and can change at short notice and some cars don't even have inbuilt GPS.
So the inbuilt nav will display a GPS based speed and the car runs an electronic system based on sensors monitoring wheel speed etc.
The two systems don't talk or reconcile hence in tunnels or car parks where GPS is blocked the nav won't display correct speed.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides


Last edited by robotdancer; 25-09-2017 at 13:20.
robotdancer is offline Reply With Quote Quote 
Old 25-09-2017   #12
Join Date: Dec 2015
Posts: 167
Thanks: 9
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

Quote Originally Posted by robotdancer View Post
You might well just happen to have a very accurate speedo. But the nav isn't linked to the car in that manner. If you think about it, the nav head units are from third party suppliers and run differing software (see all the various threads about updating the Tom Tom and 6.5" mapping etc.) and can change at short notice and some cars don't even have inbuilt GPS.
So the inbuilt nav will display a GPS based speed and the car runs an electronic system based on sensors monitoring wheel speed etc.
The two systems don't talk or reconcile hence in tunnels or car parks where GPS is blocked the nav won't display correct speed.
So what do you reckon to going up from 45 to 50 or 55 profile.

Certainly seems to be enough room in the wheel well / arch.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

theshootist is offline Reply With Quote Quote 
Old 25-09-2017   #13
Join Date: May 2010
Location: Yorkshire
Posts: 184
Thanks: 9
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

The best route is to downsize the rim and fit a higher profile tyre. Upsizing the tyre should clear the body work by the looks of it, but the physical increase in size is bigger than you'd expect when you compare side by side. Also as discussed you'll throw out gearing and speedo. Biggest difference will be on dual carriageway and motorway. In essence you'll be running too low a gear on the final drive so engine speed and consequently fuel economy and noise will increase for a given speed. Don't know wether it would be noticeable to be honest as I've not tried a car running a bigger tyre size. Only way to tell is splash some cash and hope 😊.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides


Last edited by robotdancer; 25-09-2017 at 17:40.
robotdancer is offline Reply With Quote Quote 
Old 25-09-2017   #14
Join Date: Dec 2006
Location: Southampton, Hampshire
Posts: 3,093
Thanks: 211
Trader Rating: 0
s130 has donated!
United Kingdom 
Re: Higher profile on 18" wheel ?

Quote Originally Posted by robotdancer View Post
You might well just happen to have a very accurate speedo. But the nav isn't linked to the car in that manner. If you think about it, the nav head units are from third party suppliers and run differing software (see all the various threads about updating the Tom Tom and 6.5" mapping etc.) and can change at short notice and some cars don't even have inbuilt GPS.
So the inbuilt nav will display a GPS based speed and the car runs an electronic system based on sensors monitoring wheel speed etc.
The two systems don't talk or reconcile hence in tunnels or car parks where GPS is blocked the nav won't display correct speed.
We are possibly getting a little of topic but I'm not convinced EITHER way hence my speculative / questioning post. As for the systems (despite different manufacturers/siftware not communicating with the car then I don't accept this. The vehicles sat nav system can display instructions, distances etc. on the 500Xs multi configurable central dash display. Also some of the vehicles menus/controls get transferred to the radio/nav unit.

We also know that people who have replaced their head unit lose the ability, even after a proxy alignment, to regain some of the setting functions they had on the original Fiat unit. This shows that there is "designed interaction/communication" between the manufacturer's head unit and the other vehicle systems.

I've not done the rolling radius maths yet but I've lost 4mm of tread but both systems still give exactly the same MPH. Also there are Patents on using GPS signal to self calibrate vehicles speedometers dating back several years so there is nothing new in the technology.

Time will tell.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

s130 is offline Reply With Quote Quote 
Old 25-09-2017   #15
Join Date: Jan 2011
Posts: 185
Thanks: 13
Trader Rating: 0
United Kingdom 
Re: Higher profile on 18" wheel ?

Interesting theory by S130 but I'm a bit sceptical, not knowing either way to be honest. One thing I have learnt from it is that I can't trust the speedo to be circa 5%-10% fast so i'll need to watch this.

As for the original tyre subject I did a google and came across this:

http://www.willtheyfit.com

I've equalised width (think both 7.5? although changing this doesnt seem to matter), and equalised offset (again doesnt seem to matter. Then I compare 225 45 18 vs 215 55 17. The speedo error comes out at 1.3%.

http://www.willtheyfit.com/index.php...7-5&offset2=40

Now I wonder if it is possible to swap wheels, and say manufacturers work off say maximum 2% tolerance? I never thought for a moment they'd change the gearing etc and allsorts of other stuff for different models with smaller/ larger tyres.

I noticed some time back that the cross now comes with 16" wheels as an option. I bet those are 215 60 16 because that tyre gives 0.7% error vs 225 45 18.

One thing I tweaked with was the width if you drop it down to 185 then 225 45 18 are close to 185 55 18. But that would be a bit weird, anyway the tyres arent available and would probably be too narrow for the rims anyway.

i think the only option therefore is to try and swap the 18 inchers to 17, or even 16 inch. That said I'd check with fiat first that this is ok and doesnt invalidate the warranty etc. I got nowhere with them when I asked.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

cowabunga is offline Reply With Quote Quote 
Reply
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump
Similar Threads
Thread Thread Starter Forum Replies Last Post
(S) 17" Rims on Low profile tyres. OppanAhsanStyle Punto (Mk2/2b) 20 29-12-2013 23:51
(T) higher boost + higher compression ratio arc Cinquecento / Seicento 2 07-04-2006 18:57
(S) Low Profile 13" Tyres? CinqyAbarth Cinquecento / Seicento 25 31-03-2005 23:19