345/30ZR20 tires on GTR rear
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Joined: Mar 2020
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From: Northeast USA
2020 AMG GTC
345/30ZR20 tires on GTR rear
Does anyone have an experience using Michelin SC2 345/30ZR20 (240) on GTR? Any issues with rubbing? specifically because of the rear axle steering.
Also, any dry track experience and the difference between the 325 and 345?
Also, any dry track experience and the difference between the 325 and 345?
Thread Starter
Joined: Mar 2020
Posts: 591
Likes: 341
From: Northeast USA
2020 AMG GTC
Thread Starter
Joined: Mar 2020
Posts: 591
Likes: 341
From: Northeast USA
2020 AMG GTC
For track days I am now running CUP2's 345/30-20 rear, and 275/35-19 front on a 2020 GTC. If the 2018 GTC has the same wheel well space as the 2020, you can safely run these with no rubbing. However, adding any rear spacer to the original 20" wheel with offset 46 or any lowering, will cause rubbing when going over quick road deeps or bumps. Fronts has no issues with the 275 and IMO the 285 will do fine as well.
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Thank you G.P. I cant find any info that would support any differences from 18-20 on the C other than the interior changes. I’ll have the wheels off to deep clean and ceramic coat along with a pad change so I’ll check †he wheel backspacing †hen.
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Keep in mind, for track usage, there will be characteristic changes to consider.
GTR 275 fronts and 325 rears stock, 50mm of stagger. So to maintain current characteristics you’ll want to maintain that stagger / contact patch. If you increase the stagger/contact patch differential you’ll add in more understeer, if you decrease the amount of stagger you will add in more oversteer or “rotation” to the car.
For a highly skilled driver, more rotation is usually desirable, hence why the setups on many professional race cars. For less skilled, more understeer is best as it is more predictable and easier to control.
And by less skilled, that can be anything from someone only doing a couple track days a year, or someone that is not looking for instruction, just enjoying their car in a safe way….that is in no way something to look down at, the best drivers take ego out and learn the car one step at a time, they end up the safest and fastest out there years down the road.
GTR 275 fronts and 325 rears stock, 50mm of stagger. So to maintain current characteristics you’ll want to maintain that stagger / contact patch. If you increase the stagger/contact patch differential you’ll add in more understeer, if you decrease the amount of stagger you will add in more oversteer or “rotation” to the car.
For a highly skilled driver, more rotation is usually desirable, hence why the setups on many professional race cars. For less skilled, more understeer is best as it is more predictable and easier to control.
And by less skilled, that can be anything from someone only doing a couple track days a year, or someone that is not looking for instruction, just enjoying their car in a safe way….that is in no way something to look down at, the best drivers take ego out and learn the car one step at a time, they end up the safest and fastest out there years down the road.
Last edited by dlefty; Oct 16, 2022 at 11:48 AM.
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Thread Starter
Joined: Mar 2020
Posts: 591
Likes: 341
From: Northeast USA
2020 AMG GTC
Keep in mind, for track usage, there will be characteristic changes to consider.
GTR 275 fronts and 325 rears stock, 50mm of stagger. So to maintain current characteristics you’ll want to maintain that stagger / contact patch. If you increase the stagger/contact patch differential you’ll add in more understeer, if you decrease the amount of stagger you will add in more oversteer or “rotation” to the car.
For a highly skilled driver, more rotation is usually desirable, hence why the setups on many professional race cars. For less skilled, more understeer is best as it is more predictable and easier to control.
And by less skilled, that can be anything from someone only doing a couple track days a year, or someone that is not looking for instruction, just enjoying their car in a safe way….that is in no way something to look down at, the best drivers take ego out and learn the car one step at a time, they end up the safest and fastest out there years down the road.
GTR 275 fronts and 325 rears stock, 50mm of stagger. So to maintain current characteristics you’ll want to maintain that stagger / contact patch. If you increase the stagger/contact patch differential you’ll add in more understeer, if you decrease the amount of stagger you will add in more oversteer or “rotation” to the car.
For a highly skilled driver, more rotation is usually desirable, hence why the setups on many professional race cars. For less skilled, more understeer is best as it is more predictable and easier to control.
And by less skilled, that can be anything from someone only doing a couple track days a year, or someone that is not looking for instruction, just enjoying their car in a safe way….that is in no way something to look down at, the best drivers take ego out and learn the car one step at a time, they end up the safest and fastest out there years down the road.
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Thanks for the info. It makes sense that a larger delta between front and back will cause the rear to hold better than the front and potentially tend to cause understeer. What is also interesting is that the GTC has a 40mm delta (265F/305R) which gravitate to more rotation (oversteer) while both GTR and GT BS has 50mm delta (275F/325R and 285F/335R respectively) which gravitates more to understeer. It looks like the GTC is built for higher skilled drivers then the GTR and GT BS (lol
You can’t compare that variable across brands, models, etc…..
as example, IF staying staggered on say a BMW M2 car for tracking, the stock 20mm stagger has been proven by many track regulars to be the fastest lapping set up.
Advanced drivers on the platform will go to a really wide square set up for more front end bite and vehicle rotation.
Thread Starter
Joined: Mar 2020
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From: Northeast USA
2020 AMG GTC
I am sure your just being funny at the end….but for the sake of correct info for others, the GTC set up, wheel/tire, suspension parts and settings, and the such are set up differently than a GTR. The stagger comments I made are relevant to the same exact variable of car and set up, in no way to be a guide for any car out there.
You can’t compare that variable across brands, models, etc…..
as example, IF staying staggered on say a BMW M2 car for tracking, the stock 20mm stagger has been proven by many track regulars to be the fastest lapping set up.
Advanced drivers on the platform will go to a really wide square set up for more front end bite and vehicle rotation.
You can’t compare that variable across brands, models, etc…..
as example, IF staying staggered on say a BMW M2 car for tracking, the stock 20mm stagger has been proven by many track regulars to be the fastest lapping set up.
Advanced drivers on the platform will go to a really wide square set up for more front end bite and vehicle rotation.
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2020 McLaren 720s Spider
Stock wheels absolutely. Consider that you can put at least a 15mm spacer in with the stock setting - with a 345 your adding just 10mm outward push. There is a lot of room inside - the GTRs can run a 355 with the right wheel offset.
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Keep in mind, for track usage, there will be characteristic changes to consider.
GTR 275 fronts and 325 rears stock, 50mm of stagger. So to maintain current characteristics you’ll want to maintain that stagger / contact patch. If you increase the stagger/contact patch differential you’ll add in more understeer, if you decrease the amount of stagger you will add in more oversteer or “rotation” to the car.
GTR 275 fronts and 325 rears stock, 50mm of stagger. So to maintain current characteristics you’ll want to maintain that stagger / contact patch. If you increase the stagger/contact patch differential you’ll add in more understeer, if you decrease the amount of stagger you will add in more oversteer or “rotation” to the car.
With all of the differences in the two car set ups there are other factors contributing to steering response.
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The GTC/GTR have a different set up that goes far beyond contact patch. Different weight, different offset, different tires/compound, different suspension entirely, different aero, different scrub radius etc. You are combining contact patch with stagger, and while they have a relationship with each other, they don't mean the same thing.
With all of the differences in the two car set ups there are other factors contributing to steering response.
With all of the differences in the two car set ups there are other factors contributing to steering response.
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The big change between the two cars is actually in the front with the GTR wheels having an 18mm offset change, It's a wider rim than the tire size change too.
Lots going on.
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Yeah but simple isn't the right picture. The 50mm stagger you are referring to isn't accurate. The tires are different but so is the rim width and wheel offsets etc. So that 10mm of difference in the stagger really isn't telling you much of anything until you factor in wheel size and offset too.
The big change between the two cars is actually in the front with the GTR wheels having an 18mm offset change, It's a wider rim than the tire size change too.
Lots going on.
The big change between the two cars is actually in the front with the GTR wheels having an 18mm offset change, It's a wider rim than the tire size change too.
Lots going on.
The rest was just a bit of sarcasm someone posted about GTC drivers being more skilled. I didn’t want to get long winded on that particular side bar, but appreciate you covering me on it.
