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Discussion Starter #1 (Edited)
I'm going to swap tires on my stock rims and looking at options to go wider, especially up front.

Rear there is plenty of space but front is a bit tight, especially with the 7.5mm wider track of the 600LT vs the 570S without extending the fenders which has restricted available space further.

I'm currently running a set of aftermarket wheels for street use that are 245/30/20 front ET37 on a 9" rim. This setup has exactly 0mm margin clearing the wheel well when going full lock, the outer edge of the tire barely touches the arch's fabric liner towards the doors at full lock. This is static but I think compression will increase margins rather than decreasing them so should be OK (haven't tested this yet though due to winter). This could be a good benchmark to understand the max limits of the wheel housing on the 600LT, but will reserve final blessing before i test it under load.

The conclusion appears to be that the diameter is a very important factor where there is only a small margin from stock at full lock inside the wheel arch, there is decent margins towards the outer arch edges as well as in towards the suspension strut. I think this is why people are using 235/35/19's rather than 245/35/19 which was the go to tire for the 570S with its slightly narrower front track.

Stock rim:
19x8 ET 33

Stock tire:
225/35/19

Wider options vs stock:
235/35/19: +3.5mm radius, +5mm poke per side
245/35/19 +7mm radius, +10mm poke per side

245/30/19 -5mm radius, +10mm poke per side
255/30/19 -2mm radius, +15mm poke per side

Note "Radius" (not "Diameter"), the radius is basically how much less gap in the arch you get on each side as well as the diff in ride height.

Stock and my 245/30/20 (which "just" fits) vs 255/30/19
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I think 30 profile 245 and 255 will fit due to their smaller diameter while 35 profile variants would not. 255 will be a bit squeezed on a 8" rim but should work. All these options are within 3% diameter diff of the stock setup so should not cause problem (unless you go extreme on the rear in the opposite direction), the 255/30/19 is just 0.7% diff from stock.

Anyone with experience or "expert opinions" about this before i take a chance and buy a set of 245 or 255's? :)

If this works and you want to max traction you could go 255 front and 305 or even 315 rears with maintained front vs rear balance.

A safe option that im 99% sure will fit and work great is 245/30/19 front and 305/30/20 rear. This keeps front/rear ratio for both diameter and width very close to stock with a slightly smaller diameter both front and rear vs stock which should even give a tiny bit better acceleration and less rotating energy to brake and accelerate.

Cheers
/Roger
 

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The bigger issue is what tire are you planning to use? Different tires have different shoulder profiles and that makes a huge difference. Bridgestones are a soft, rolled angle while Hoosiers are more of a pronounce, sharp, right angle. Plus, some tires are actually have different dimensions despite having the same stated size. For example, a 255/35-19 Pirelli P Zero was much more narrow than my wheel even while the Bridgestone RE71R in the same size was wider than the wheel.

Kurt
 

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Discussion Starter #4
The bigger issue is what tire are you planning to use? Different tires have different shoulder profiles and that makes a huge difference. Bridgestones are a soft, rolled angle while Hoosiers are more of a pronounce, sharp, right angle. Plus, some tires are actually have different dimensions despite having the same stated size. For example, a 255/35-19 Pirelli P Zero was much more narrow than my wheel even while the Bridgestone RE71R in the same size was wider than the wheel.

Kurt
Yes the brand and sidewall/shoulder design is also part of the puzzle, very hard to know exact fitment before someone actually tries with a specific spec and brand on a specific car...

Haven't decided brand yet but its very much leaning towards the new Cup 2 Connect due to performance, availability, pricing and durability, they are now available new new sizes as well so you can go 245/30/19 or 255/30/19 front and 305/30/19 or 315/30/19 rear. There are stickier tires but they are more expensive and lasts a lot shorter, my priority is mainly fun and progressive handing but beating some GT3's wouldn't hurt :)

Since i'm using the stock 8" wide rims I think the 245 will be best visually as its already at the wider end, if i was buying new rims I would go 8.5" with 255's.
 

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I generally run 235 Hoosiers on the front for track events and they just ever so slightly rub on the driver's side, at the very back portion of the fender liner during full to near full left turn lock. Think of it as the 3 o'clock position when viewed from the face of the wheel. No rubbing on the right side. I tried to put a set of 265 Hoosiers on the front as I have a slightly used set from my other car (C63 AMG) but they REALLY rubbed and there is no amount of caster or shims that would make them work. I realize that is a big step from 235s to 265s but it was worth a shot. My point is that you may be starting to push it around a 235. Some brands may allow a 245 or even a 255 but you will just have to test it or hope that someone else here has. Please report back with your findings and good luck.

Kurt
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Discussion Starter #6
I generally run 235 Hoosiers on the front for track events and they just ever so slightly rub on the driver's side, at the very back portion of the fender liner during full to near full left turn lock. Think of it as the 3 o'clock position when viewed from the face of the wheel. No rubbing on the right side. I tried to put a set of 265 Hoosiers on the front as I have a slightly used set from my other car (C63 AMG) but they REALLY rubbed and there is no amount of caster or shims that would make them work. I realize that is a big step from 235s to 265s but it was worth a shot. My point is that you may be starting to push it around a 235. Some brands may allow a 245 or even a 255 but you will just have to test it or hope that someone else here has. Please report back with your findings and good luck.

Kurt
View attachment 209625
Thanks Kurt

Is this with the OEM wheels?

As I mentioned in my post the diameter appears to be very sensitive, if you go both wider and with larger diameter rubbing is very likely... that is the problem with 235 or 245 tires with the stock 35 profile... But going with a narrower 30 series 235, 245 or even 255 would yield a smaller diameter than stock. The unknown is how much the reduced diameters but added width does at full lock inside the fender at the different widths...

My 245/30/20 (7.5mm larger radius than stock) very very barely touches the fur at the place in your pic, there is a small budge into the fender from the doors hydraulic arm and the area inside it towards the center of the car.

I guess a new liner isn't allt that expensive in case it rubs and it isn't really visible either with the wheel in place nor does it do any actual harm to the car.

I think I will go with the 245/30/19 front and 305/30/20 rear Michelin Cup 2 Connect

The 245/30 front has a 5mm smaller radius vs stock (but builds 10mm outwards), a 235/35 (which I guess you ran and most do) has 3.5mm larger radius vs stock (and builds 5mm outwards)... I think the 245/30 will have more room towards the fender at full lock as its a full 8.5mm smaller diameter but only builds 5mm more outwards.

Combining it with the 305/30/20 rear is a nice match as its also slightly smaller radius than stock which helps to keep the rake angle close to stock and avoids any ABS/traction control issues.

I'm just very curious to why the 245/30/19 and 305/30/20 is not the default setup for track or increase traction setups and I have not seen anyone use it after some extensive googling and browsing this forum... Maybe its down to that these dimensions have not been available before, I think these are both new dimension just released a few months ago for the Cup2 connects.

Will update when I try it out in a few weeks time
 

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I am hoping 265/30/19 with a 9.5", higher-offset wheel (40-45mm) would fit with a street/track alignment (not more than -2.5潞 camber). It's the exact same diameter as 225/35/19. What do you think?
 

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Roggan,

I am using Finspeed wheels so that may be part of my lack of getting the 265 to fit. I am very curious to see what you find out with your experiment.

Kurt
 

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Discussion Starter #9
I am hoping 265/30/19 with a 9.5", higher-offset wheel (40-45mm) would fit with a street/track alignment (not more than -2.5潞 camber). It's the exact same diameter as 225/35/19. What do you think?
I think it could work, as far as I can see there is decent space inwards so if you increase ET to keep the outside tire edge to same or only a few mm further out than stock and same or less diameter you should clear the inside fender. If you go too wide eventually you will scrub the inside suspension or fender on the inside of the wheel at high steering angles but it looks to be a decent margin.

Moving the contact patch significantly inwards though will also affect steering feel and how the car tracks and behaves under breaking as you change the "scrub radius". Basically the wheel will pull further in towards the center of the car on each side from the center of the suspension then what it is calibrated for from the factory. Hard to tell how much difference it will be without testing, it could be just fine and it could be significantly worse, my guess is that the 600LT is especially sensitive to this as it has so much feel coming through the wheel. What will happen is that the front will push for increased toe under breaking, depending on how tight the suspension bushing are this will impact handling to a larger or smaller degree.

I think the 245/30/19 front with 305/30/20 rear for the front could be the most neutral update maintaining balance and steering feel but with increased grip. 265's front would be awesome for lap times though if possible as this would match the GT2/3 RS spec and allow the 600LT to keep up with them in the slow corners where you otherwise will get understeer on 225's or even 245's :cool:
 

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I run 245/305 on finspeeds on cup2s. Huge difference. No rubbing or other issues. Don't be too greedy just to have issues.
 

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Discussion Starter #11
I run 245/305 on finspeeds on cup2s. Huge difference. No rubbing or other issues. Don't be too greedy just to have issues.
Great to hear, very much looking forward to trying the car out with the Cup2's and wider dimensions, my car came with the street PZeros so it should be a big upgrade in traction! On clearance however the 570S and 600LT has difference clearance margins up front.

I have both a 570S and 600LT, the LT clearly has noticably less room/margin up front than the 570, most likely due to its wider track and 720S suspension. I have a set of after market wheels that are 9x20 ET32 with 245/30/20 PS4S front that fit on the 570S for 2 years without issues but on the 600LT I cannot even turn the wheel full lock. I had the hubs milled down by 5mm to ET37 and now they clear with literary 0mm margin. Rear clearance should be much closer if not identical between the two though.

I think 265's front with higher ET (further in) and 30 profile vs 35 stock profile could work even on the 600LT, but I have pretty much made my mind up on 245/30/19 front and 305/30/19 rear, especially since I'm using the stock rims which are just 8" front and wider tires than 245 would fit but it would look a bit weird, the stock 225's are pretty much square sidewall fit already... :p
 

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That makes sense. My wheels are off a 600 with 245/305. That sucks. I'd never run more than a 225 on an 8. It makes it sloppy. I did that with a prior P car and was incensed with the shit handling. 235 on 8 and 295 on 10. It was a pig without the wider wheels to support it. You will have other guys say different, but I didn't buy the car to have it drive like a pig on rollerskates with that sidewall flex which can create too much countersteer.
 

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Discussion Starter #13
That makes sense. My wheels are off a 600 with 245/305. That sucks. I'd never run more than a 225 on an 8. It makes it sloppy. I did that with a prior P car and was incensed with the shit handling. 235 on 8 and 295 on 10. It was a pig without the wider wheels to support it. You will have other guys say different, but I didn't buy the car to have it drive like a pig on rollerskates with that sidewall flex which can create too much countersteer.
I get your point and I'm sure there is a difference but you make it sound huge :geek: I agree the ideal rim / tire match is 225 or 8", 8陆" for 235/245. But I want to use the stock rims and get some more front end bite and am willing to compromise a bit on turn in feel for more grip by going up to 245. With a 245 30 series tire there is also significantly less sidewall than a 245 35 (or even the stock 225) which will counter some if not all of that loss in sidewall support due to the slightly narrow rim.

On my street setup i run 245/30/20 on a 9" rim, this optimal in my view from an visual perspective with proper ET for flush fitment and it is extremely stiff and direct.

This is a 235/35/19 Cup2 on a stock 8" 570S rim, considering that the sidewall is round this does actually look quite square to me, another 5mm more poke shouldn't be that bad at all.

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You can get away with it on a cup2 more given the stiffer sidewall. On a less stiff sidewall, I find it injects too many artifacts of weight transfer.
 
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