Mixing Tyre Profiles

[PCC]

Regarding tyre setups, what effect does mixing profiles have?

My car was originally setup with 225/50 x 16 on the front and 245/45 x 16 on the back.

Not sure if the speedo was calibrated to the above setup (will have to check out). But, does mixing the % profile have any profound effect on the car?

[HotRodJoe]

Hi Peter,

I don't think anything magical happens when you have matching aspect ratios (profiles) between front and rear. Even some production cars mismatch (like new Corvettes, if I'm not mistaken). As far as aesthetics, personally, I don't think tire setups look right if the front tire has more sidewall height than the rear. But you can obtain the right look with different combinations of aspect ratio and tire width. Just my 2 cents.

Joe

[Cameron Parsons]

In terms of rolling surface, your setup would give you a very even match... Other than that, I notice that you have been trying to raise the rear of the car. A profile change in the rear to a 50 or greater will help that. Will also get a little squirmy if pushed.

225/50-16:
_--sidewall (mm) = 112.5
_--diameter (mm) = 631.4
_--circumf. (mm) = 1983.6
245/45-16:
_--sidewall (mm) = 110.3
_--diameter (mm) = 626.9
_--circumf. (mm) = 1969.5
(0.71)% difference in circumference.

Cameron

[Aussie Mike]

the number you should be concerned with is the rolling diameter.

The profile figure is just a percentage of the tyre width. A 225/50 series tyre has a sidewall height of 112.5mm. This is 50% of the width 225mm. It's only approximate and can vary a little between manufacturers but that's how it works.

Your rear tyre is a 45 series so it's side wall will be 45% of the width (245 x 0.45 = 110.25) that's only a whisker different to the front.

I'm running 45 series tyres on the front and 35 series on the rear but the sidewall heights are the same:
315/35/17 315 x 0.35 = 110.25mm sidewall
245/45/17 245 x 0.45 = 110.25mm sidewall
This means the rolling diameter is going to be the same front and rear.

I think Joe's comment on new cars with mismatching profiles not looking right is an optical illusion created by the wider rear rubber making the sidewall appear smaller. I also think the newer Corvette runs 18" rear rims and 17" fronts which adds to it.

Cheers

[Cameron Parsons]

315's Mike!!

I bet they just about touch in the middle

[Aussie Mike]

That's what Garrett is running under the back of his Superformance. I hear guys in the US are even fitting 335s under the back of their Superformance Cobras.

The 315s fit in fine on the Classic Revival. It was a bit stressful ordering my rear rims as there wasn't much room for error on the offset I'd worked out. I just had to modify the lower shock mounts to bring the shock in a little to give a little more clearance on the rim. I don't think I'd squeeze the 335s in without modifying the top shock mount as well.

Cheers

[Cameron Parsons]

I'm an old fashioned kind of guy and will be running 275/60/15's....

Nice and squishy..

As for Garrett, you know what they say about him ---->

Cameron

[jasonnichols]

I run 245 60 R15 Front
275 60 R15 Back litle too big at front but it looks really good and yes I think garret is........

[Cameron Parsons]

Just one little push and I knew I could start a vicious rumour with no more than an icon..

225 at the front for me...

[Rebel1]

235/60/15 and 295/50/15 for this ole fella.

Yeah...and I agree with what ya say about Garret too.

[Aussie Mike]

If you were making 552 rear wheel HP you could be forgiven for being a bit

Just look at Craig, He's definitely a bit

[750hp]

Need a bit of extra sidewall? How about the BFG 325/50/15 Drag Radial? Mustang drag racers are running 8 second timeslips with this tyre !




Oh yeah.... how about that Garrett guy You guys are so heartless. Never met the guy, but anyone that owns an SPF with that much mumbo can't be all bad.

[Aussie Mike]

By the way,

If Industrial Deafness comes from working with loud machinery, what do you get from working with Morons??

Industrial Stupidity?

I'm having one of those days.

Cheers

[750hp]

Mike - our posts crossed. Nothing strange about me - I'm just your average nerdy bank employee. That's why the police seem to let me off with the odd indiscretion. Pulled over about 8 times in my life, got 1 ticket, a couple of severe warnings and the rest seemed to be an attitude test. Hop out of the car with a genuine smile, have the license ready for them, comment on the lovely Qld weather, hop back in the car and drive away. Much cheaper option than showing an attitude and copping a fine.

If that makes me , then guilty as charged !!!!

[SCOBRAC]

Nothing. Do the math. a 275 mm wide tire which is 45% as tall as it is wide is the same height (same aspect ratio) as one which is 315 mm wide and 35% as tall. Both tires share an almost exact overall diameter.

[PCC]

Thanks guys - as informative as ever

Craig, that black Cobra is a monster - it makes mine look like a baby cobra

The reason for my question was that I was toying with the idea of lifting the profile at the rear thereby lifting the back end a bit. I'm a little reluctant lifting the suspension anymore as the handling is good as is.

From an aesthetic point of view I agree with Mike and Cameron that it is not the profile, but the rolling diameter which is important.

Back to the thinking stage.

On an aside, I am changing the appearance of the instrumentation cluster (hopefully today) and will post a pic later of my Z4 Cobra

[justbetter]

Ah Grain of salt...


Put that in your eye and thats why im

[BMK]

Garrett

Over at Dougs shed this Saturday. Have you been there before?



Beresford Road, Lilydale. Give me a ring if you feel like a drive around to the eastern end of the ring road.

If not, I may try and catch up on the way home as I will obviously come back that way.



Cheers

Bernie

[justbetter]

Love to Bernie and no i havnt been there before , but this little black duck will be tanning his a$$ in Fiji with my beautiful fiancee, and daughter come Friday night.

[Cameron Parsons]

Now you see, it's true....

If you drive one of them danged Superformance doo dads, ya git the girl and the trip to Fiji.



Have fun in the sun

Cameron