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Discussion Starter #1
right iv bought myself a set of amg style 1 alloys for my 170 but they have no tyres iv seen a set the same for sale with 245/40/17 and 225/45/17 tyres fitted are these the correct sizes I want to be buying .the current tyres fitted to the car are I think 225/?/16 rears with 205/?/16 fronts.oh its a 1999 230k 170
 

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My 01,320 came with the AMG package. I checked the label in the drivers door jam and it has front 225/45/17 rear 245/40/17.
 

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Discussion Starter #5
thanks I didn't want to buy the bigger size than I already have then find they foul something 245 and 225 it is
 

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The AMG rims add an inch of width and an inch of diameter.
But at 17", they are not too extreme (some with 18" find them crashy) and the rims fill the arches so nicely I would not want anything bigger.

I suppose I think the design teams tend to get these things right, so I would definitely start there.
If you do a lot of cornering, and find the tyres a bit swaying, then undersize the rubber by about 2cm (ie 225 becomes 205) and that will make the tyre walls trapezoidal, so there will be much less tyre wall movement.

So the SLK R170 AMG front rims are 7.5", with 225 mm tyres, so have 35 mm more tyre than rim, so 17 mm each side.
Similarly, the rear rimes are 8.5" with 245 mm tyres, so have 29mm more tyre than rim, so 15mm each side.
And my Clio has 7" rims with 185mm tyres, so have 7mm more tyre than rim, so 4mm each side.
And the Clio is the epitome of sure-footed!
 

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If you do a lot of cornering, and find the tyres a bit swaying, then undersize the rubber by about 2cm (ie 225 becomes 205) and that will make the tyre walls trapezoidal, so there will be much less tyre wall movement.
... But then don't you have much less grip, as you reduce the width of the tyre?
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As for tyre size, that's right, 225/40R17 for the back for R170 AMG... I am changing them tomorrow actually, and was wondering the best compromise grip/road noise... I had some P.Zero in my previous car, but they generated so much road noise, and I changed to M.Pilot Sport, it was a bit better but still... I wonder if the Yokos would be OK...
 

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... But then don't you have much less grip, as you reduce the width of the tyre?
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Agreed, with all other things being equal, you might expect 10% less grip.
But although the width has decreased, the contact pressure has increased by the same amount, and you are down to the physics of the rubber about how this affects the grip.
And there are times when more rubber is recognised to be detrimental (snow, standing water, etc) so "more rubber = more grip" does not always hold true.

And this depends on all other things being equal; the post-facelift R170 has an additional tie-bar (anti-sway bar) on the rear axle; for a pre-facelift vehicle, this factor may exceed any benefit that a different tyre design could provide to tighten the response of the car going though a series of corners.

And seriously, how often do you drive your car that close to the upper limits of what it is capable of? I suspect improved feel (by reduced sway) may come into effect much sooner than ultimate grip. Of course, hazard assessment would say the danger of failure of ultimate grip is greater, so the ultimate grip is more important. (Poor sway characteristics probably cause the driver to go slower, too, so improves the safety by *reducing* confidence! ;) )

There is a much quoted comment from Colin Chapman that tyres produce maximum braking force at 10% slip; getting one tyre to that optimal configuration is such a challenge, let alone four, that it takes a computer to control each of the wheels independently, and was unrealistic in the (pre-computer) real world. But I do wonder how much this braking force value varies with condition of the rubber, brand of tyre, sizes, configuration, etc, in terms of the maximum braking that can be achieved for a car.

As for tyre size, that's right, 225/40R17 for the back for R170 AMG... I am changing them tomorrow actually, and was wondering the best compromise grip/road noise... I had some P.Zero in my previous car, but they generated so much road noise, and I changed to M.Pilot Sport, it was a bit better but still... I wonder if the Yokos would be OK...
I have a personal bias towards Pirelli, since I have found they work with all the cars I have pushed hard, but I know that for similar cars, this doesn't work. (Vauxhall Nova v Ford XR2; similar cars, but on P6, the Nova was a joy to push in and out of drift around corners, and the XR2 had no feedback until it let go)
And I had Michelin Pilots on my Clio, as specified by Renault, both HX and SX, and neither were good enough for the brakes, and I finally got the braking to work properly when I moved to Pirelli P5.
But tyre choices seem to be a combination of personal preference and how the car is set up.

Anon
 

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Way above my head all this I just go by the feel of the car. Ive never been totally happy with the handling on my 99 230k it has Pirelli P7 tyres with good tread on them but it has always felt slightly not surefooted to me. The ride is jiggly and a bit bouncy and when you steer/point the car it just doesn't feel right but I cant quite put my finger on the problem. Ive had lesser cars that felt so much better on the road ie Ford Puma(best handling car ive driven) and a Gen 7 Celicia im actually disappointed with the SLK.
Dave
 

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Way above my head all this I just go by the feel of the car. Ive never been totally happy with the handling on my 99 230k it has Pirelli P7 tyres with good tread on them but it has always felt slightly not surefooted to me. The ride is jiggly and a bit bouncy and when you steer/point the car it just doesn't feel right but I cant quite put my finger on the problem. Ive had lesser cars that felt so much better on the road ie Ford Puma(best handling car ive driven) and a Gen 7 Celicia im actually disappointed with the SLK.
Dave
Yes, I feel similarly, it is the feel that needs to be right.
Sometimes a bit of bounce and jiggle can be entertaining, if you know where it will be going when it does touch down again. And it does need to be "planted" at some speed (pref open road speeds), to justify the jiggle around town.
But a well setup system should be reasonably compliant at all speeds, even if it does jar as it crosses some of the grand-canyon sized potholes. Note the word system; the road is the input, and there are many "outputs", including steering wheel vibration, seat of the pants, speed through corners, confidence under braking, stability, etc. And the system consists of so many masses and springs, it can be challenging to analyse even once you have the characteristics, so the empirical test "It feels right" is the best we have.

Oh, yes, decrease the P number of your tyres; higher numbers are for "more normal" cars.
And the Continental 5 series seem to have a good reputation; German tyres on German car sounds like a good choice.
 

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Tolak;784681 Oh said:
Ok confused again what do you mean by the P number (do you mean pressure) I always use the tyre pressures on the fuel flap for my size tyres.

Dave :bannana:
 

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Ok confused again what do you mean by the P number (do you mean pressure) I always use the tyre pressures on the fuel flap for my size tyres.

Dave :bannana:
Sorry to confuse.
Pirelli tyrea are P7, etc, and typically the higher numbers are for more "normal " cars..
The ultimate tyres are P0.

I'm currently running the Clio on P5000, having been on P5 until they were no longer available.
 

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I had a lot of 'jiggle' with the cheap tyres that came with the erzatx AMG wheels- every time I went anywhere near the white line down the middle of the road and cats eyes I was all over! and then last week in standing water (I know that is difficult anyway) I couldnt keep her on the road- Can thoroughly recommend Barum Bravvius apparently made by Continental the OEM MB tyre and certainly seems to have good grip in the wet and dry with them just on the front- need to get the back two dont now.
National do an offer on Ebay for two 225/40/18 for £160 fitted/vales/balancing at a national tyre garage near you. Same tyres drive in drive out are £225

And........... I just scraped my immaculate rims down a kerb last night.... Bugger!
 

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Discussion Starter #14
well just drove a 300 mile round trip to pick the rims up and he said they had been recently refurbished and he wasn't lying there like brand fire new:bannana::bannana::bannana: just need to save up for tyres now oh and there was no centre caps so ill pick a set up on ebay
 
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