__215/45/17 vs 225/45/17__
I have a 156 Ti 1.9JTD SW ('04) and was looking for new decent tyres for the worn fronts (215/45 17).
I had a good look around AO and 156.net and google and noticed this thread amongst others and so decided to go with the forum recommended 225/45 17 tyres as they are cheaper and also should have a better ride quality.
Unfortunately, when they were fitted today the garage stated they were dangerous as the tyres almost touch the suspension arm (at the top) and with tyre flex + bearing movement + expanding hot tyres - this 'could' easily be a rubbing point leading to tyre failure. The gap (cold) is maybe around 4mm between the top of the tyre diagonally to the strut curving round the inner corner of the tyre (coming up from the hub).
It was decided a small spacer (3-5mm) might be a possible fix, but we obviously didn’t have any and I didn’t know what affect this may have on steering geometry or possible outer rubbing on the wheel arch. We checked the rear wheels and they had better clearance, the fronts and rear wheels were swapped round and the new tyre (225/45/17) then had a minimum of 10mm clearance from suspension arms on the rear.
The half worn budgets (215/45/17) have around 10mm clearance on the front strut, so I assume brand new 215/45/17's would have a little(?) less clearance than this.
I've now got spanking Uniroyal Rainsport 2's (225/45/17) on the rear and half worn budget's (215/45/17) on the front, which is a bit of a waste of good tyres.
Also, I have a mismatch in tyre sizes on the front and rear axle which It doesn't seem I can fix by getting a another pair of 225/45's (as I had originally planned) due to this clearance issue.
The 4mm gap 'might' have been acceptable to some people and may never had caused an issue if I was lucky, but as I often take my 2 young children in the car I wasn't about to take a chance on 'maybe' or 'might', it's not worth it.
I got back on 'tinternet tonight with a vengeance (assuming that no-one had noticed the dangerous clearance issue) to have a good moan and then found even more related threads (AO & 156.net) with some pointing out possible clearance issues with 225 tyres on the Alfa 17"x7 rims. I wish I had seen those threads before buying the 225's.
So, I've now collected loads of info from various threads on this subject from some of the more 'senior' Alfa brains on the boards (mainly Pascs & DavidC), which I've added below so that it's all in one place, where hopefully others facing the same decision can quickly get a good idea of the potential risks of not using the manufacturer recommended tyre size (which I will never do again, my bad), what the pro's and cons are, and also some info on the related topic of load index. Thanks to the contributors.
Also, all you 156 guys with 225/45/17's on, if you haven't done this already - check the clearance on your fronts against the suspension arm at the top! (& check for tyre wear - in the inner corner, where it wears worst on the JTD's anyways...)
The previous owners existing 215/45's budget tyres were very crashy and felt a bit dangerous for the alloys with lumpy roads and unnoticed pot holes, although it did turn out they only had an 87 load index (rather than the stronger 91).
That was part of the reason why the recommendation of 225/45/17 tyres held appeal (& the lower price really did help…) as they should be slightly softer with higher side walls and more air volume.
When I heard mention of the load index (or load rating) on the forums, I'd never noticed it before, so I looked at the 156 manual (1.9 JTD, 17" Ti wheels):-
__Alfa 156 Owner Manual__
Alloy wheel: 7J x 17"
Tyre: 215/45 ZR17"
(no tyre load index listed, but all 15"+16" alloy tyres are listed as 91V)
ZR: Radial tyre with speed above 240kph (149mph)
91: Load index (capacity), eg 91 = 615kg. ----> Not present in ZR tyres <-----
V,Z: Max speed index. In ZR tyres the speed index Z is before the R.
So basically the Alfa recommended tyre is = "215/45 ZR17", with no load index rating listed (the load index rating is listed for all other tyre sizes). Question: So what load rating is intrinsic to a ZR rating? (17"s must need at least 91 minimum?) Answer: Dunno, it doesn’t appear to have a set rating? (The manual says that ZR tyres don’t state a load index, but my budgets are 215/45ZR17 87!?)
Then I find the recommendation on the boards that 87 is too low a load index for the 156, which makes sense if even the larger tyres are rated at 91. But, most of the 215/45/17 tyres you can buy are rated as 87 ('R' or 'ZR'). With being new to both having a heavy Diesel engine and having 17" rims, and being fed up with the crashy 215 (87) tyres a higher load index seems a good idea. This again points people more in the direction of 225/45/17 tyres as they are plentiful with '91' rating or 'XL' (eXtra Load) or 'reinforced'. And cheaper.
So, load rating and XL tyres and reinforced tyres make it a bit more confusing, especially when your manual doesn’t state a preference.
It looks like 215/45/17 (91/XL/RNF) are definitely the best way to go if you can find them (at a premium).
There is some info below I've grabbed from the web relating to load index.
Tyre Load Rating | Blackcircles.com__USEFUL INFO__
The load index is a numerical code that corresponds to the maximum weight a tyre can support.
A tyre's load multiplied by 2 must cover the gross single axle load of your vehicle.
To determine your load index, locate the number on the sidewall of one of your tyres and compare it with
the load index table.
I’ve often seen ‘XL’ stamped on tyres. What does this mean, and is there a performance advantage?
XL stands for Extra Load – or is sometimes referred to as Reinforced.
Essentially, tyres bearing this stamp are designed for heavy cars rather than ones that carry big loads.
Not only are they constructed to cope with weight, but also the higher tyre pressure these vehicles need to run at.
This marking is usually found on lower-profile tyres used on large cars.
It highlights the fact they are built to a higher weight rating, as there is nearly always a standard version in
the same size in the maker’s range.
What does RNF mean?
RNF indicates that the tyre is reinforced. Reinforced tyres are mostly
fitted on to small / light vans, people carriers and some 4X4 vehicles
and estate cars. More recently, car manufactures such as Audi, Renault
and Saab have been using a new type of reinforced tyre. These tyres
are high-performance, low profile tyres and come as original equipment
on high-performance cars. The extra load carrying capability gives
these tyres more rigidity, enhancing the road holding.
Usually you will notice an appreciable increase in ride harshness and noise using XL tyres, there are some
around that use different materials in the sidewalls to try and counteract these disadvantages but as a rule
XL tyres will give a harder and noisier ride, if you don't need them stick to standard ratings.
The 225/45 tyre was never offered by Alfa for use on the 156 / 147 except on the GTA (which has different offset and wider wheels)
It may be the correct rolling radius but not all 225/45 tyres will fit without rubbing on the front suspension, rubbing the front inside arch plastic on full lock or catching the rear arch when fully loaded - which is probably why Alfa used the 215/45 tyre as a safer option that would not result in complaints from customers
My 225/45's on GTA rims catch the rear when fully loaded too but the wheel offset is 35mm.
What is the offset of the wheels you want to fit - this will play a big factor on the tyres you can fit.
If it was me I'd go for 225/45 tyres - the 215/45 can be a bit hard and 225/45 has a bit more side wall.
Standard Alfa 7x17" wheels have an offset of 40mm.
…40mm are a bit too far in for 225/45 tyres and these tend to catch the inner front suspension where it curves up over the tyre.
I fitted 225/45x17" to my 7x17" Alfa alloys. This was a very tight fit at the front because of the top wish-bone, but any 17" wheel with an offset of about 35 will fit without problem with 225/45 tyres.
215/45x17 is the correct size but a few have fitted 225/45x17 without problems - I guess it depends on the tyre as well as the offset of the wheels.
IMO I would not go for an offset less than 35mm since the standard 215/45 x 17 tyres on the 7x17" wheels are already very close to the suspension. This is with an offset of 40.5mm.
IMO 35mm is the best compromise.
The 225/45 was not designed to go on standard 7" Alfa alloys and can rub the suspension - standard is 215/45.
The correct size is 215/45R17 all round.
Don't use different size front-rear.
No point at all having larger rears on a FWD car.
You will also have different diameters, which will mean the ABS/EBD won't work properly.
The std fit is 215/45R17, although 225/45R17 are used on the GTA.
225/45R17 will fit with the std Alfa 7" rims, but clearance will vary between different make
The original homologated sizes were:
15": 185/65R15 & 205/60R15
16": 205/55R16 (std for all Sportpack/Veloce & all Selespeeds)
Optional 17": 215/45R17
17" can use either 215/45R17 or 225/45R17. Often 225/45R17 are the lower cost of the two.
But all four should be the same size..
I'm surprised you are finding 215/45R17 with "91" that are not XL or RF.
225/45R17 on the other hand are 91 normally and 94 XL/RF
As the 215/45R17 have such a low load index and you have a heavy car
you should be aiming for the upper end of the listed pressure, ie 2.5Bar (36PSI).
Notice that the load index is only 84, so they are not strong enough for a 156 either
The 17" selespeeds have a 40.5mm offset and they definitely do not work with 225/45 tyres (it rubs the gearbox and is about 3-4mm away from the suspension strut).
I AM A GOD
Just noticed that my 2 front tyres are "JUST" touching the inner suspension strut (17/45/225)
The normal pressures for 205/55R16 are 2.2bar F&R or 2.5bar F&R at full load.
In theory the 215/45R17 need higher pressures because of their lower load index: 2.6bar F&R to 2.9bar F&R fully loaded.
ALWAYS set the pressures when the tyres are cold.
225/45R17 are fine at 2.2bar/32psi
Should be 215/45R17
Minimum cold pressure is 2.2Bar (32PSI), never run lower than that.
Everything you ever wanted to know about tyres
Car Bibles : The Wheel and Tyre Bible Page 1 of 4
Car Bibles : The Wheel and Tyre Bible Page 4 of 4