Tyre size advice & opinions

[gibby]

Right then, a short heads up, when I went to the last Newark meet and I saw Neds blue Rivage and saw that my tyres look dead skinny compared so I've been thinking about putting some new ones on (dont even go there Rob or Ned!  ). The car is currently dropped by about 40mm and they are not adjustable. I'm currently running on 185/55/15s but I'm wanting to go down to 195/50/15s or possibly even 195/45/15s. I found myself being obsessed with tyre sizes as GTI festival yesterday and wanted to know peoples opinions, should I got to a 50 or a 45 profile ?  I'm not even sure if it will look good or not because if I drop down the profile size then I'll get more space in my arches so I'm really undecided on this. Another question is this too, is the 45 profile a harsher ride as I'm guessing it is and it is my daily drive so I'm not sure which route to take. 

P.S. This is all jv's fault as I was quite happy with a 195/50 but jv then mentioned 195/45 and there my dilema started ! 

[gtodesign]

Overall diameters....
185.55.15 584.5mm
195.50.15 576mm
195.45.15 556.5mm

50's are the correct tyre for a Mk1 but they look so cool when lowered on 45's.

[Bronze MK1 Cab]

Gibby, mine are 195/45/15, they look good, but they are a harser ride 

My winter wheels were 175/70/13, so didn't feel any bumps with them, but they looked totally sh1te 

I reckon you'd be best going for the 50 tyre wall, the only reason why mine are 45s is because that's what tyres were on the wheels when I bought them. The 50s are much cheaper too 

[GTiMK5]

I know you probably know this anyway but a decrease in profile without an increase in the wheel size also affects your speedo readings etc. If a profile of 50 with a wheel of 15" is the correct size then to drop the profile to 45 you would need a 16" wheel to keep the speedo working correctly.

[gtodesign]

I know you probably know this anyway but a decrease in profile without an increase in the wheel size also affects your speedo readings etc. If a profile of 50 with a wheel of 15" is the correct size then to drop the profile to 45 you would need a 16" wheel to keep the speedo working correctly.

Not quite, but your on the right lines... To go from a 195.50.15 to a 195.45.15 is a 3.4% difference in overall diameter, therefore if your speedo is calibrated perfectly for 195.50.15's, changing to 195.45's would cause the following;

If your speedo was reading 50mph, you would be doing 48.3mph
If your speedo was reading 100mph, you would be doing 96.6mph etc

[gibby]

Thanks for the replies so far.I know about the rolling radius change and I've got a website saved in IE on my work comp that checks what the speedo is when changing tyre sizes. I'll post it up tomorrow in this thread if I remember. Don't know how accurate it is but it gives you an idea. I think at 60mph it said 50s would actually be doing 59.1 and on 45s it would be 57.9, something like that.   

Anyone else any opinions ? 

[eyeletboy]

i had 195/45/15's on mine but now changed them to 195/50/15's so there looks less of a gap between the arches and the rubber.i would think it will be a smother ride as well.the cars coming out next sunday so i'll soon know the differance and let you know.

[gibby]

Cheers eyelet. I've booked my car in for a Powerflow exhaust to be fitted tomorrow morning as mine has started to blow so seems like a good excuse  and I'm going to whack four new tyres on there too, probably going to go for 195/50/15s I reckon.  Thanks to all that replied. 

I mentioned earlier about the website that you can check the changes to the rolling radius on when you change the tyre sizes from stock, it has been posted on here before because that's where I got it from, but here it is ----> http://www.miata.net/garage/tirecalc.html 

[mix]

low n stretched

[G6dub]

Gary said you need to go for a look like his!

He has 165/45/15 yes 165 nice and stretched you can't buy them in the UK you have to get them from Germany.