Pull trigger on wheel/odd tire combo?

[Pete S]

So I finally located the real deal AMG wheel I have been looking for in an 18" Staggered version in the correct offset for the R129s but from every chart/post I have seen or read I always see 245/40/18s listed for the front and 275/35/18s listed for the back.

The guy selling the wheel/tire combo (Michelin Pilot PS2s) has 235/40/18s mounted on the front and 265/40/18s mounted on the rear. He says I should have no problem as there is a ton of room in the rear fender well to accomodate the higher profile tire and it will just look beefier.

Is this an accurate statement or am I going to have some odd rubbing or speedo issues? I'm no tire guru so what he is saying sounds accurate but there has to be a reason for the MB engineers to have two different profile tires mounted when they rolled off the assembly line. Thanks in advance to anyone who can clear this up.

By the way the deal is $800 + my 17" AMGs that look exactly the same rolling on Michelin Pilot Sports. Mine have 50% tread left he says his has about the same 50% tread left which sounds fair but currently more worried about the tire size but if you want to chime in on good deal/bad deal that would be cool too. By the way the wheels look like these:

[MercedesTheBest]

i don't think that them being a different size by only 10 would change much. they look not to bad those wheels. if those are the ones you like then go for them. only go for the wheels that you'd actually really like otherwise the ones you're in love with may come up and you would have wasted money, or whatever on these ones.

that's just my $0.02

[Pete S]

Mercedes my faves are yours but I have a feel I may wait to long for them. I like this style mostly because of how you can see the wider lip on the rear wheel, I've noticed most of the newer wheels the lip size stays the same it just the angle of the spokes change but I like the visibly wider lip.

[MercedesTheBest]

i do like the visibly wider lip as well. well if you like these ones then you may as well go for it. but if the ones you do like come up that could suck if you spent your money. completely up to you though.

[lynns]

The original R129 AMG Sport Package came with the following:

8.5Jx18" front and 9.5Jx18" rear staggered-width AMG I 5-spoke monoblock alloy wheels
Front 25 mm offset & Rear 23 mm offset, with a 5x112 mm bolt pattern
Front wheels: OEM p/n 66031008
Rear wheels: OEM p/n 66031009
245/40ZR18 front and 275/35ZR18 rear, max. performance summer tires with a rolled wheel arch modification for AMG wheels.

I am currently wearing 285/35ZR18 rear, Conti ExtremeContact DW max. performance summer tires and have no rub problems.

[feedingtherat]

i think the reason for the usual tyre choice of 245/40/18 front and 275/35/18 rear is that the rolling radius (and diameter) is very similar - 245/40 gives an rr of 12.85 inches vs 275/35 at 12.78 inches. the big danger if the rolling radius is significantly different front to rear is that you'll experience asr/abs problems and maybe end up in lh mode. unfortunately i don't know what difference in rr between tyres is allowable.

the tyres you mention come out as follows

235/40/18 rr 12.70 inches

265/40/18

[feedingtherat]

to continue .........

265/40/18 rr 13.17 inches

so i'd be concerned that the difference might cause issues. i guess the only way to be sure is to try them. all the above presumes other issues like offset etc are ok.

[Poundy]

He's probably put them on because they were a cheaper option.
As long as they are 8.5J and 9.5J wheels, just put the correct size on when they need replacing.
The only reason MB put different profiles on was to keep overall diameter about the same when using staggerd widths

[lynns]

Originally Posted by Pete S

The guy selling the wheel/tire combo (Michelin Pilot PS2s) has 235/40/18s mounted on the front and 265/40/18s mounted on the rear. He says I should have no problem ....

Is this an accurate statement or am I going to have some odd rubbing or speedo issues?

Try Tire size calculator - Miata

235/40/18 has 794 revs/mile
265/40/18 has 765 revs/mile
difference of 29 revs/mile, therefore a possible ESP problem.


245/40/18 has 784 revs/mile
275/35/18 has 788 revs/mile
285/35/18 has 780 revs/mile
difference of 4 revs/mile

[RKH]

I think using rolling circumference for calculations gives a better picture than rolling radius.
And if the rolling circumference of all four are within 3% of each other, they are considered as a matched set.