Tyre Profiles...

[Andie_M]

Right well...

I got new tyres all round now. Vredsteins, which apparently i keep saying wrong haha! Apart from that, I changed the profile. Which I really shouldn't have done I think. The ride has got a lot rougher, and the back end seems to grip less. Lowered the back profile, noticed a big difference in how the tyre looked straight away!

So anyone else done this? Or got any advice, bar getting different tyres cause i cant afford it! lol

[cfc1]

What size(s) did you get?

Original sizes = 185/55x15 front..... 225/45x16 rear.

[GIDDLEPIN]

[1bloke1dog1mr2]

I've wondered about this for ages (a year or more). Still haven't decide on size: 15", 16", 17" so I'm still stuck with the flakey originals!

[cfc1]

If you are getting new wheels.. I'd go for 17".. 205/40x17 front and 225/45x17 - 225/40x17 rear.. but.. going 17" you WILL need to lower the car too.. the extra height with the 17" on makes the car unstable at higher speeds.. lowering cures it.

[1bloke1dog1mr2]

AND my tyres are like new, so I'm thinking 15" all round (I have the pre-face lift). Would love to go 16" just to cover the arches more, but will probably stay away from 17" now you've said. The originals are really spoiling the look!

[T600]

If you are getting new wheels.. I'd go for 17".. 205/40x17 front and 225/45x17 - 225/40x17 rear.. but.. going 17" you WILL need to lower the car too.. the extra height with the 17" on makes the car unstable at higher speeds.. lowering cures it.

How can that be cfc1? Shouldn't you should keep the rolling radius the same when you change wheel and tyre sizes. e.g. larger wheel, perhaps wider tyres, but correspondingly lower profile to compensate. If that were the case then you wouldn't alter the ride height at all. Or do the wheel / tyre combinations you've recommended alter the rolling radius?

[GIDDLEPIN]

AND my tyres are like new, so I'm thinking 15" all round (I have the pre-face lift). Would love to go 16" just to cover the arches more, but will probably stay away from 17" now you've said. The originals are really spoiling the look!

Mine's the pre facelift (with the wider rears) I'm on my third set of Yoko's and I love them, once they settle down they don't let you down when pushing hard, ok you don't get megga mileage out of them but i never got the car to drive in granny mode ;)

[1bloke1dog1mr2]

AND my tyres are like new, so I'm thinking 15" all round (I have the pre-face lift). Would love to go 16" just to cover the arches more, but will probably stay away from 17" now you've said. The originals are really spoiling the look!

Mine's the pre facelift (with the wider rears) I'm on my third set of Yoko's and I love them, once they settle down they don't let you down when pushing hard, ok you don't get megga mileage out of them but i never got the car to drive in granny mode ;)

Decided then! Found a great website, has anyone had any experience of these guys?

[GIDDLEPIN]

AND my tyres are like new, so I'm thinking 15" all round (I have the pre-face lift). Would love to go 16" just to cover the arches more, but will probably stay away from 17" now you've said. The originals are really spoiling the look!

Mine's the pre facelift (with the wider rears) I'm on my third set of Yoko's and I love them, once they settle down they don't let you down when pushing hard, ok you don't get megga mileage out of them but i never got the car to drive in granny mode ;)

Decided then! Found a great website, has anyone had any experience of these guys?

What for?...................These?

[1bloke1dog1mr2]

AND my tyres are like new, so I'm thinking 15" all round (I have the pre-face lift). Would love to go 16" just to cover the arches more, but will probably stay away from 17" now you've said. The originals are really spoiling the look!

Mine's the pre facelift (with the wider rears) I'm on my third set of Yoko's and I love them, once they settle down they don't let you down when pushing hard, ok you don't get megga mileage out of them but i never got the car to drive in granny mode ;)

Decided then! Found a great website, has anyone had any experience of these guys?

What for?...................These?

They would just totally go with my pink steering wheel cover and fluffy dice!

[cfc1]

If you are getting new wheels.. I'd go for 17".. 205/40x17 front and 225/45x17 - 225/40x17 rear.. but.. going 17" you WILL need to lower the car too.. the extra height with the 17" on makes the car unstable at higher speeds.. lowering cures it.

How can that be cfc1? Shouldn't you should keep the rolling radius the same when you change wheel and tyre sizes. e.g. larger wheel, perhaps wider tyres, but correspondingly lower profile to compensate. If that were the case then you wouldn't alter the ride height at all. Or do the wheel / tyre combinations you've recommended alter the rolling radius?

You would think that would be the case . however in practice it isn't....

My standard fronts = 185/55x15 = Rolling Radius of 292.25

Current Fronts = 205/40x17 = Rolling Radius of 297.9

Difference of 1.93%

Standard rears (Facelift model 2003 on) = 215/45x16 = Rolling Radius of 299.95

Current Rears = 225/45x17 = Rolling Radius of 317.15 (225/40x17 = 305.9)

Difference of 5.73% (225/40x17 = 1.98%)

I preferred the way the 45 profile filled the rear arch better

As you can see there isn't that much of a difference in the overall Rolling Radius of the tyres, but look at this....

Before Lowering

After lowering

I'm not sure why this happens even when you have the same (or as close as makes no difference) rolling radius, but it definitely raises the height of the car.. or at least gives a very visual appearance that it has... maybe it's the lower profile making the gap between the arches look too big?..(Maybe someone will post a piccy of a standard car to compare the 1st pic I posted).. as you can see from the pics above, the 2nd pic is closer to how my car looked (gap between tyres and arches was just a little bigger.. but not much) with the standard wheels and springs

Another reason why the roadster should be lowered after fitting bigger wheels is to do with the aerodynamics on the underside of the front end.. there are two little wind deflectors that sit just infront of the front wheels, these are there to divert airflow around the wheel, with 205 tyres, and this extra bit of height, these deflectors don't do as good a job.. and with the Roadster having a very light front end, the extra air that gets under the car isn't deflected around the wheel causing the front end to get VERY twitchy at higher speeds (if found at about 80mph it got really quite difficult to keep the car in a straight line) Lowering the car lessens the amount of air getting under it making the car feel as planted as it was with the standard wheels.

Sorry I'm not that good at explaining things... but I hope you understand what I'm trying to point out in both points I have made. :)

[Andie_M]

Original sizes...

185/55x15 front..... 225/45x16 rear.

My sizes...

195/55 R15 85V - Front

215/40 ZR16 85W - Back

One of my friends told me to bear up with them, cause they are just new they could still be kinda bedding in... fingers crossed their right...

[cfc1]

OK.. the rears are a lower profile than the original rears, but with your new front tyres you have actually raised the profile by 5.5mm, It's not much.. but could be enough to be letting just a little too much air under the car making the front end feel a little light.

Check and adjust your tyre pressures to 25psi front and 29psi rear.. IF you front tyre pressures are around the 30psi mark at the moment, you should feel the benefit of dropping down to the 25 - 26psi. After doing this.. let the tyres wear in and see how they feel, if after a couple of hundred miles it still feels skittish.. then I'm afraid if you want it to be as it was before, you would need to change the tyres again.

195/50x15 for the front would have been more suited... but unfortunately the advise comes a little too late on this occasion.. but try to remember to ask for opinions in here before you do anything that you are unsure about.. people will only be too happy to give their advice and opinions going by their own experiences of the past.

[Andie_M]

Well as it was, the fronts were off my brothers old mk2 mr2. Just so happened they were 15's so I took them, then the only ratio I could get for the back was as stated.

I'll get beg one of the guys i know to come with me to check the tyre pressures, cause i am HOPELESS at that! lol

lesson learnt i suppose, but trial and error will really tell how they are say back end of next week.

[cfc1]

Take it easy untill you get the feel of what your car is doing. :)

[msherry21]

Women!!!! :!Removed!:

[Andie_M]

dont you start mikey! lol

[msherry21]

ha! buy wheels first, then ask the forum what size to go for...awesome!

I love it!

Yet another blonde moment.

[Andie_M]

i do recall trying to no end to get a hold of you to ask you, but you got back to me after my dad had ordered them so dont start you!