From my understanding, 2 different sizes fit the 16" wheels:

205/50/16
225/45/16

Does that mean that 225/50/16 would also work?

It not so much fitting the wheels as keeping the same overall diameter. 225/50/16 will give a 20mm larger overall diameter affecting gearing speedo etc

To put that into perspective, the difference in diameter between 205/50/16 and 225/45/16 is just 2mm.

Ahh ok i think i get it now..

So if the diameter difference between 205/50/16 and 225/45/16 is just 2mm, whats the width difference? 20mm?

Yes, although this value is affected by the rim width, i.e you could put a 225 on a 7.5" or 8" rim no problem but the actual tyre width would be slightly different.
IIRC the rim width on all Coupé 16" rims is 7" so not an issue.

If that was the case then won't the 225/45/15/16 be the ideal choice since its 20mm wider (bigger contact area) and just 2mm difference in diameter (2mm less won't cause that much uncomfort would it)?

225/45/16 is fine and is the standard tyre size on post '99 coupés, it does offer more grip at the expense of being more prone to tramlining

Cool. Didn't know that it was standard on post 99 coops.

Thanks for your help Ed!

In the time honoured fashion, I have a calculator that might help here

It's the rolling radius that counts here.

205/50/16= 612.2mm

225/45/16= 609.7mm This is 0.4% smaller than standard meaning your speedo will over read by 0.4% (indicated 80mph will be 79.7mph)

225/50/16= 632.2mm This is 3.2% bigger than standard meaning your speedo will under read by 3.2% (indicated 80mph will be 82.5)

One thing to remember, is that your speedo will over read anyway. By changing to a slightly larger rolling radius, you might even make it more accurate. Taking a 5% under read on your speedo (like mine is with 205/50/16) the above become;

205/50/16= 5% under read
225/45/16= 5.4% under read
225/50/16= 1.8% under read

The 225/50/16 should therefore be OK really. Pointless though, in that you won't gain anymore grip from wider tyres (lets not go there though ), and they'll prob be dearer than 205/50/16s.

I've been toying with the idea of 205/55/16s next time. You get another 10mm of sidewall for more comfort, the same grip as the compound can be the same (same model of tyre), the speedo will be more accurate, and they're cheaper by £10 a corner.

Interesting Trappy. Thanks for the comprehensive calculations

I was looking at the Falken 452's and the price difference between 205/50/16 and 225/45/16 is about £20. I would like some wider tyres but wondered if this was worth the extra premium. Will the wider tyres make any noticeable difference?

205/55/16 sounds interesting but surely the bigger sidewalls will compromise handling?

After lots of reading on the subject, it appears that wider tyres will just stretch your contact patch making it wider and thinner. This has no effect on grip, but there was an intersting article in Performance Car recently where a 'techy' from Prodrive was interviewd in a handling article.

He said that wider (and therefore lower profiled) tyres, will improve turn-in response at the expense of ride quality meaning the suspension has to be adjusted to compensate, undoing the benefit of the tyres in the first place. Secondly wider tyres lose some of the 'self righting' of a thinner tyre. Lastly, he said they reduce the feedback from the road, making it harder to feel the break-away point and on the limit balance.

There was quite some emphasis on the relationshp between the sales people (who want de big rims!) and the people setting up the handling and that best handling cars out there are those that have a good influence from the techies. I'll try to scan and upload it, bloody good read

55 profile will probably make it handle a bit 'sloppier', but the billy/ eibachs are loosening my teeth after nearly 30k miles, and I think a smoother ride would make most road cars faster in the real world. At anything over 50mph on a bumpy back road, there's the very real sense that I might be airborne at any minute...

Trappy

Very interested in your comments - I am just having a set of wheels refurbed and was going to buy a set of 205/50/16.

Your comments about using 55 intesests me for 2 reasons:

1. I live in Sheffield and the roads are lousy so 55's would mean for comfort.
2. My coupe has the front lips on and I have caught them on speed bumps and my drive 3 times already.

Questions

a) I presume 55's would lift the body of the car higher off the ground?
b) would there be any problems with clearance within the wheel arches?

cheers spookone

If you put 205/55/16 on instead of 50s you would only raise the car (in theory) by 2.5mm, dont think you notice it

Thanks for your comments Trappy. I look forward to the article.

Roads in Glasgow are terrible as well so the 55's would be a strong consideration. I would be interested to know what the clearance on the arches are like too as the current 205/50/16 look very close to them.

Anybody?

I need to order my tyres :-)

Questions

b) would there be any problems with clearance within the wheel arches (or anything else) using 205/55/16 on 16" VT wheels?

Desperate to buy a set of new tyres so this is a repeat of my entry on another thread but...

Will 205/55/16 cause any problems with clearance in the wheel arches?

Come on, one of you experts MUST KNOW

Is your car lowered spookone?

Need to be a bit careful here peeps, the numbers on the sidewall do not necessarily relate to the real world.
205/50/16 has a diameter of 611mm
205/55/16 has a diameter of 632mm
So you would actually be raising the car by 10.5mm and reducing the arch clearance by the same amount.
You could try it but I think you may find it rubbing.

Hi Kelv

I have only had it a few months so I am not entirely sure - have been wondering as it does seem a little on the low side.

But to be honest I dont think so???

I was asking Joe @ Countrycrusising and he mentioned that 55's should be ok.

Not the words I tend to entertain when it comes to tyres, I much prefer definitely to should

So you advise against it then Ed?

Yes, it's not a standard size for the car and unless someone posts that they have run this size for a significant length of time with no problems I wouldn't touch it myself.
Glancing back through the comments on this thread, it should clear the arches, it may improve ride comfort, it may make the handling a bit sloppier.
Too much conjecture, not enough proof for me

Thanks for your opinions Ed

Hi Kelv

What decision have you come to regarding the 55's?

I am desperate to lift my front lips that additional 10mm off the road and get a more comfortable ride on the pot hole filled roads of Sheffield.

As Ed has mentioned above... has anyone ran 55's and did you have any probs?

Why don't you be the pioneer of 55's and let us know how it works out?

Ok - let me know how you go on first - then I will give them a try :-)

I am still tempted ?!?!

Someone must have pioneered the 55's...

Anyone?

spookone, if there was someone that have tried them, they would have said something by now.

A little touchy arent you?

I was just trying to inject a little humour into the question of 55's - if you don't want to play, you don't have to.

I think you do need some sleep :-)

A little touchy?

You were asking for comments from people who have used 55's like a million and one times..to the point of starting a new thread (that i have to merge with this one).

I doubt anyone has tried it yet..or atleast give it some time for someone to reply!

Ok i'll go take a nap now.

OK I will get my coat :-)

I tried some 55's on........









Can't remember for the life of me what happened though?

I did read somewhere that 55's can be run on the coop, without real problems, they may get a bit close to the bottom arches though, especially on the back arches, I would imagine.

Do a search, I'm sure there are answers somewhere

Cheers Patch.

I think I will fit 50's after all -I was worried about the back arches - I admit defeat :-)

I've had 205/55/16 at the rear for a while , no problem whatsoever , one day i've dropped them to the front and it was fine too.You'll ask what suspension? It was KW-2.

Anthrax - thats interesting and just in time as I need to order tyres pretty quick and can go for pirelli rather than Falkens with 55's.

One last question - what is KW-2?

Dont all laugh :-)

KW variant 2 coilover suspension

OK Anthrax / Kelv (was hoping you wouldnt notice I was still carrying a torch for 55's :-)

Does this mean that you having KW-2 and fitting 55's with no problem means that my standard suspension set up should mean I have if anything more clearance?

Logically that would be the case. Depends on what height the coilovers are adjusted to..but i would imagine it to be lower than standard.

I've just bought some 50's spookone, but if you do get the 55's in the end, it would be good to hear your feedback on them too.

Yes , it's lower than standard and you'll have even more clearance

OK as Kelv suggested I am going to Pioneer (even though Anthrax has run with them) the 55's.

Just ordered a full set of 205/55/16 Pirellis to go on my newly re furbed smoke silver wheels (havent seen them yet).

I wont have the time to get them put on the coupe for a week or so but will let anyone who is interested have my opinion once they are on.

Should give a slightly more pleasurable ride on the nasty roads of Sheffield and give a little more clearance over the dreaded speed bumps etc.

I had 205/55/16 on my last coupe!

Well I say that it had 50's on the front and 55's on the back no idea why??.

But I was very soon to change to 50's all round as the wheels on the back looked very odd to the ones on the front.

The sidewalls looked massive and made the alloy look like 14" not 16" if that makes senselike an offroad wheel but on a coupe

Coupe 16vt "plus" factory dimension is 205/55 r16 (16x6,5 et40 rims) and they dont scrub.
I'm not sure they would work flawlessly on 20vt though; does 20vt have slightly different suspension geometry (different pillar on 20vt), changing the pivoting radius (horizontal plane) of the wheels?

OK Guys and Gals

Collected my re furbed alloys from Metal Magic (I am very, very picky and have to say they did an amazing job - I was blown away by the quality of the work) and had my new Pirelli 55's put on it.

I know there has been various concerns as to if they would catch etc. and I am pleased to report they dont!!!

The ride is completely transformed, the bad roads of Sheffield no longer have me dreading taking it out, and it is now far more enjoyable for every day driving.

The tyres obviously look a little larger but no where near as large as I was imagining and they actually fill the wheel arches better and I like the look.

It has the added bonus of lifting the car 10mm so the speed bumps are also easier to negotiate.

I am very very happy with the result - glad I took the gamble and would recommend 55's if you want to make every day driving a little more comfortable

Excellent news spookone. Glad to hear its running well. How does it handle?

Pics please!

Glad to hear it

Just remember, your speedo is now a little more 'accurate' so don't go driving at 5% more than the speed limit because you know it 'isn't really going that fast' (I do this all the time).

My Track tyres are 205/55s on the front and 225/50s on the back - they fit but it is a tight squeeze

Fitted my refurbed alloys with 55's today.
Car seems to ride better and less crashy.Loads of speed bumps around here

Havent had a huge test as im going to take the car for tracking soon but overall feels good so far.

blackcircles are doing 4 x 205/55 R16 W (91) for £218.24 delivered (£10 off if buy 4, I usually go to Bracknell Tyres for fitting around £7 a corner) which seems a good price, I was gonna go for 225/45's as normal but they're around £70 each. Quite like the idea of a slightly more accurate speedo and I can always reset the ride height with my FK's

Falken 452's are cheaper from Camskill in that size but I fancy trying the T1-R this time.

Hmmmm....now I'm wondering about 225/50's since they're the same overall size as 205/55, so same benefit for speedo, back to same 50 profile as original, but still a wider tyre for that bit more rim protection, bit more pricey though at £77.45 each from Camskill...(to be honest that's what I have been used to paying in the past for a few previous sets of Marangoni Zeta's)

205/55/16 doesn't actually make the speedo more accurate.

The radial difference between 205/50/16 and 205/55/16 is 3.35% . Apparently you should keep it within 2.5%.

That means when your speedo reads 70mph,your actual speed will be 72.35mph with the 55's.

If you speedo was accurate, I'd agree. Next time you've got the GPS in your car, see what you're actually doing when yur speedo says 70mph

It doesn't matter whether your current speedo is accurate or not.

If your speedo is already inaccurate with standard sized tyres (205/50/16), its going to be even worse with those tyre sizes (205/55 and 225/50).

Diasgree. Typically my speedo reads 10% high, eg: when I'm doing 77mph by GPS, speedo says 70 With the 205/55 or 225/50 tyres, the circumference is bigger as you say, so the error will be reduced since when I'm doing a real (GPS) 70mph the speedo will now say 74.5mph.

If the speedo was reading low, then yes, the larger tyres would make it worse.

The "keep it within 2.5%" rule is only of any use if you have a roughly accurate speedo to start with

Come on man, grey matter- ENGAGE. If it's under reading (which I know it is) and you fit a bigger wheel/tyre combo, the speedo will be only more accurate



WTF? I'm sorry, there is no way that your speedo is reading low (your explanation is suggesting that btw). In Autocar's road test the coop was reading up to 10% lower than actual speed. Mine under reads by 5% across the board. No car is going to under read with standard tyres...

A bigger than standard wheel/tyre combo on a coop will make the speedo more accurate.

Ah yes sorry i overlooked that. It would be better if your speedo was under-reading. Just had the impression that speedo's in most cases over-read.

Well I even confused myself, what I meant was: at a true GPS indicated 70mph, speedo used to indicate 77mph with fairly bald 225/45x16's.

Now I have 225/45x17's on 17" Momos and speedo reads 72mph albeit with full tread of course.

But I think I went too large, see http://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1008062&#Post1008062

How are folks getting on with 205/55/16's with lowered cars? I know Anthrax was ok, has anyone had any issues at all?

I need to buy some new track rubber for my car, and this profile is extremely cheap

Well mine passed the MOT OK, only problem is a slight rubbing on the "corrugated" wheel arch liner on full lock sometimes

Is your car lowered Dave?

Yes, but I'm not sure by how much. I think the best way to define it is to measure the height of the top of the sills front and rear both sides. I did end up at 28cm +/- 1cm when I first raised it up from being tooooo low, but that was with OE wheels and 225/45x16's. With the 225/45x17's I expect I am a little higher now. I've got the FK coilovers with Bravo top mounts.

Can i ask why bravo topmounts?Do they fit fine on a standard setup?

I will be lowering mine soon with 55's so will post feedback as soon as

The FK's come as standard with a solid ball bearing mount, too hard for me and many others, the bravo mount has a big chunk of rubber and makes all the difference in getting the cheap-ish FK coilover solution to work, IMHO they're no good without the bravo mounts, but we're going a bit off-topic here. If you're lowering with Eibach springs for example you should be OK on 205/55's since the tyre is no wider (205) than standard.

Thats fine then,i should be lowering 30mm with 205/55

My current front track rubber is 205/55, a tight fit but no issues and lowered.

Does anyone have a picture they can post of a 20VT running the 55 profile tyres so we can see how it looks?

justg picked up some 20vt wheels running 205/55's think I might change them as they seem massive, anyone got any pics with 55's on?